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March 15, 2007

Cicada Emergence Formula

Filed under: Magicicada | Periodical — Dan @ 1:01 am

You could try this with northern Magicicada periodical cicadas, but I would avoid it for southern states like Louisiana (because you’ll get negative numbers, which will be confusing). Also, do not use temperature data from past years, because the weather is wildly variable and you’ll get a useless number.

Gene Kritsky was nice enough to send a paper he wrote with a formula for predicting the emergence date. E = (19.465 – t)/0.5136, where E = emergence start date in May and t = average April temperatures in °Celsius. His formula worked like a charm for predicting the Brood X emergence in Cincinnati. 80% of his sites had begun the emergence on the predicted date of May 14th of that year. Also when the ground temperature reaches a consistent 18° Celsius that is another good sign the emergence is about to begin.

Try it out:

Average Mean Temperature in Celsius in April: (hint: use a site like Weather Underground to find this info)

The date should be:

Updated: we updated the form to accept 3 numbers past the decimal in case you have super-precise temperature information.

To find the Average Mean Temperature in Celsius on the Weather Underground site:

  1. Go to the site
  2. Enter your zip code in the box labeled “Find the Weather for any City, State or ZIP Code, or Airport Code or Country”
  3. Find the section of the page labeled “History & Almanac”, and click the “April Calendar View” link.
  4. Then scroll to the top of that page and you’ll find the info you need.

Thanks to Roy Troutman and Gene.


  1. pamela johnson says:

    their here right now in kanawha county in charleston WV 17 year 2016

  2. Sandra says:

    We are seeing a lot of dead cicadas what could be the reason for that? I live in Brownsville, Pa. Fayette County.

    1. Dan says:

      @Sandra This is typical. Unfortunately there is often a lot of loss in the first wave of a cicada emergence, a lot of which is due to the lack of good surfaces for them to hang from and molt. More info on that here

  3. Jessica says:

    I read that 2014 is the year for Brood XXII! As a Louisiana resident, yay!!! I tried using the above formula to calculate an estimate for cicada emergence but soon realized that our average temperature for April (25-26 degrees C) gives me a negative May date.

    Additionally, I notice that Orleans parish is outside the described range for the 13 year cicada species. How rigid is range? Is there a large variance from emergence to emergence? Thank you!

    1. Dan says:

      Don’t use it for Louisiana. It is too far south, and too warm for the formula to work.

      Not sure about the Orleans parish, but I haven’t seen any records for that. The name of the Brood is the Baton Rouge Brood, which should give some idea of where it is centered around.

  4. Jeff says:

    HEY GUESS WHAT! I went outside two spots with a couple holes in them. I though they could be from skunks because they flare out at the top, but they’re very round and about 6″ deep. Could that be them????
    I heart cicadas!!

    1. Dan says:

      It could be!

  5. Jeff says:

    I have never had the opportunity to see magicicadas. I’ll take some of you guys’ if you don’t want them. HAHAHA.

  6. Jeff says:

    I’m in SC Pa, not seeing any.
    Well, darn.
    How do I cicada?

    1. Dan says:

      The emergence has been sort of disappointing in PA — at least what I’ve seeing from the live map.

  7. Betsy says:

    I am getting married outdoors in Sheffield, Ma on June 22nd. Do you think my ceremony will be ruined by millions of emerging cicadas?! I am having nightmares! Help!

    1. Dan says:

      Doubtful. There are no 17 year cicadas anticipated for Massachusetts this year.

  8. Jenn says:

    Hey I calculated my emergence date as 5/12. We have been watching or them, but only today saw many little holes, shells on trees and about 4 adults; just as the formula said. With our cold spring, I wondered, but you were right on the mark.

  9. Rayne says:

    My predicted date says “May -83” what is that supposed to mean? as far as I know, dates cant be negative, and no month has 83 days

    1. Dan says:

      Maybe sure you use Celsius and not Fahrenheit.

  10. Karen says:

    So I live in NJ and having a college grad party in my yard for 70 people on June 1. I used the emergence formula and came up with May 30 for them to appear – UGGGHH! Will my yard be covered with them on that day or will they just start to “appear”? We will be in the grass yard! HELP!!

    1. Dan says:

      Karen, you might luck out. You might live in a town where the cicadas won’t appear (more than half of Jersey). If the temperature stays cool, you might avoid it as well.

  11. Erin says:

    Hi there! Thanks for all the great information on this site – super helpful! So now that I know that the cicadas won’t be harming the plants in my garden, I’m wondering about my trees? I notice that in one of the comments above you mention that the only real damage that occurs is when the cicadas lay their eggs int eh trees? Can you explain that a little bit? I have an very old black walnut tree (rather large) in my backyard. Should I be worried about any damage? Thanks!

    1. Dan says:


      You don’t have to worry about large, mature trees, particularly native species. Although not always pretty, hearty domestics can withstand cicada egg laying. It’s the small, wimpy imports you have to worry about. Cicadas co-evolved with domestic trees, and since the cicadas are parasites of the trees, it would not be in their best interest to kill their host.

      BTW, here is what the cicada damage looks like:

      flagging caused by cicadas

  12. Anya says:

    not with my luck: in 2004 we had them billions….:(

  13. Anya says:

    Thank’s, Dan 🙂 Do you know the best way to protect small trees? I am not sure I can cover all of them. Thanks

    1. Dan says:

      Well, you can hose then off, or remove them by hand.

      You might wait until the emergence happens before going out and buying supplies. You might not have an issue.

  14. Anya says:

    What about garden? I will try to cover 2 small trees, but what about tomatoes? Blueberries? Any advices please?

    1. Dan says:

      Anya, fortunately cicadas don’t eat leaves or fruit, so garden plants don’t interest them. Their damage they do happens when they lay their eggs in branches of trees.

  15. Larae Zeman says:

    Outdoor wedding party planned for July 20, 2013 in zip code 21120. Will cicadas be gone by then?

    1. Dan says:

      Larae, you might be in luck just by virtue of the fact that 21120 falls outside of our records for past brood II emergences

  16. Jenn says:

    Thanks for this. I came out with an answer of “May -67.” How do I interpret this?

    1. Dan says:

      You probably used Fahrenheit and not Celsius. You have to use Celsius. I should make a Fahrenheit version, come to think of it. °F to °C Deduct 32, then multiply by 5, then divide by 9

  17. nancy says:

    I just caught one in North Hills, CA (Los Angeles County) Just one was so loud I could hear it from 200 feet away. I flushed it out of the tree with the hose and when it landed on a fence I captured it in a small container.

  18. Alice Nelsen says:

    How long do the adult cicadas live after they have emerged? I live near St. Louis, MO, and they emerged about 2-3 weeks ago. They started ‘singing’ about a week ago. The ground is littered with them. My daughter’s outdoor wedding is scheduled for July 4th. Will they be gone by then?

    1. Dan says:

      They should be all but gone 35 days from now. You might have to do some lawn clean up though to get rid of the corpses.

  19. Maria says:

    Can somebody please help me?? My daughter is getting married in May of this year and she is freaking out over the cicadas. We live in smyrna, tn and I cant seem to get the date for when they expect them to emerge!!

    1. Dan says:

      There isn’t a set date. Depends on the location, and how quickly the soil at that location becomes warm enough for them to emerge. I’ve been to an outdoor wedding during a cicada emergence and it wasn’t bad at all — and 15 years later the couple is still happily married (rare these days).

  20. Angela McGrady says:

    Hi. What will the Cacadias be like in Summerville, S.C.? Are they so many you can’t enjoy your yard? Will they eat any herb or vegetable I’m trying to grow? Are they a nuisance? How about the Ashley River or Lake Moultrie? Will they land on the boat or on us? What is a realistic expectation? Thanks! A.M.

    1. Dan says:

      Fortunately, or unfortunately you’re out of the range for 2011 in Summerville SC. Western SC, like Greenwood will get them.

  21. ZekeL says:

    I don’t know when they emerged, but for the last week or so,
    it’s a cicada fest here in Allentown, Lehigh County, PA. I
    remember the last Brood XIV emergence in the late 1980’s (1987?)
    Is this a XIV emergence here? Anybody? Anybody?

  22. mike says:

    i live in between lake city and clinton, tennessee and for about 3 weeks now they have been emerging. i live about 2 miles from norris lake and about the same from I-75 north. there are so many that you can actually here them over the noise of the busy interstate. also what is the real deal with the folklore about the “w” or “p” on the wing tips i heard that these markings were “w” for wartime and “p” for peace time is this true? thanks

  23. Jeff Johnson says:

    Mass emergence of cicada began yesterday (31 May 2008) here in Bellefonte, PA (Central PA, zip code 16823). I like to work outside with a wireless laptop and a wireless phone. Looks like I’m going to have a lot of background noise!

  24. chris says:

    i live in shelby county kentucky i just wanted to tell u all i have thousands of cicadas in my yard already they are everywhere

  25. mary whalen says:

    I was told to use tobacco cotton to protect my 1 1/2 yr. old crabapple trees. The cotton seems heavy for the trees to bear, and I don’t want to lose them. It is very windy here. Tree nets are very hard to find.

  26. mireek says:

    cecidas ar3 so s3xy

  27. Vaughn Murray says:

    I found tons of holes this weekend (April 26-27) at my cabin in Union County PA (base of Jack’s Mountain near Millmont, PA) and one just left its hole. A hundred in just one square yard area and hundreds more holes around the area…going to be a loud summer!

  28. Amanda says:

    Hey – great site. We are planning our wedding for June 7th, outdoors of course, or I wouldn’t be worrying. What kind of invasion do Cicadas have over downtown urban areas? Example: Downtown Cincinnati?

  29. Bruce Westfall says:

    There is a LARGE list of cities and states mean temperatures found here.

    Not eaten a cicada yet, but our chickens will love them.

  30. Jerry Glenn says:

    Cicada’s hatching in Knoxville, Tennessee. I’m watching one in my dining room right now. It emerged from the ground about 2 hours ago,
    has been very still for about an hour.
    This is new for me. Jerry – August 12 @ 9:15 PM

  31. Terry Newport says:

    The Caicada’s are out in southern New Hampshire. The emergence started about a week ago.

  32. Greg says:

    I had posted question on June 15 asking anybody if they knew if we’d see them in Carol Stream, IL 60188. Well were seeing them now! Only since last week of July. Is this unusual? Did anybody else get the substantially later than May/June when other areas saw them?

  33. Audra says:

    When should the Ohio Valley region of West Virginia see an emergence of cicadas again? Huntington, WV area

  34. Jason says:

    I live in Royal Oak, MI, will the cicadas be emerging out here?

  35. Dan says:

    The ratio should be 50/50.

  36. Jim says:

    I am curious as to the ratio of males to females. I went to some woods nearby and came back with
    about 150 cicadas because I want them to be back in the area. Do you think my effort might be

  37. Lauren says:

    i saw some in gurnee when i went to six flags. not many..but some. They are all over by house house in Schiller Park. You’ll be stopped at a red light, and they’ll be swarming EVERYWHERE! It’s quite gross. You can pump gas during the day without at least 10 of them landing on you..and you see them all crawling all over EVERYTHING. gross x38473.

  38. Laurie says:

    I haven’t seen any in Antioch, nor have my friends in Gurnee, Lindenhurst and Lake Villa. Does that mean we will not see any or at least not very many?

  39. Greg says:

    Anybody know if we’ll see any in Carol Stream, IL 60188? None this year so far, but we saw a couple last summer.

  40. Ron says:

    We live about 6 miles northwest of Janesville, WI, about a block and a half from the Rock River and seem to be one of the few spots in the area that experiences the cicada invasion; we heard the first buzzing on May 27th. I remember hearing about these guys as a teen at the Chicago Museum of S&I but never imagined I’d be living amongst them someday. We lived here for 2 years when we were suprised by the weird buzzing and all that goes with it. Little did we know that the trees we had just planted would be prime targets. We ended up loosing about four trees but thankfully got a 17 year jump on them this time. Our yorkie snaps them up like candy!

  41. Dan says:

    Kentucky… no major emergence this year — but next year, brood XIV. You might see a straggler or two this year.

  42. JC says:

    I was just curious if Central to Eastern KY will see cicadas emerge this year?

  43. Amy says:

    Cicada Mania in Valparaiso Indiana!!!! Yuck! I opened our sliding glass door Saturday and heard a weired buzzing sound. My fiance said it was probably an electrical problem down the road. We live in the country, extremely quet and peaceful. I went for a walk this morning and the closer I got to the woods, the louder the sound was. Then I began to see SEVERAL random red/orange wings laying around and then I just knew, we’ve been taken over. I walked a little further and one was in the road. I was getting ready to step on it when it suddenly flew up into a tree. YIKES!! I ran home. When will they leave??

  44. Margaret says:

    i’m going crazy and can’t wait til these guys are gone. i’m in riverside and, slowly but surely, they have gotten worse & worse, but not quite as bad as glencoe seemed 17 & 34 years ago. it is very loud here, but the noise doesn’t bother me in the least… it’s the darn things flying and lurking around – it’s going to be a long june!

  45. Janet Tabin says:

    We didn’t go from nothing to overwhelming as fast this year as I seem to recall 17 years ago —
    but we are in full swing this morning!! Highland Park, north and east —

  46. Bill Cicada says:

    I followed all the emergences around Chicago and on May 22 only about 5 sites reported very small numbers of cicadas. The first major wave appeared on Memorial day and emerged all day long. The biggest wave ( May 31) was 3 days later. I have heard reports that a few a still emerging all around Northern Illinois.

  47. shelly says:

    i garden for several lake geneva estates and there are thousands of these fabulous creatures concentrated in one part of a yard and then none to be seen in the next. same with the town – they’re all over in the streets, on houses, shrubbery, etc in one block and then none on the next. their distant sound is like an eerie sci-fi alien invasion. very cool.
    haven’t seen them south of lake geneva – yet.
    love it!

  48. Tim says:

    I was in Iowa this last week staying with a friend near Iowa City, and a cicada landed near his garage, so we put it in a jar and killed it with a cotton ball full of alcohol so it could be preserved.

    I live in Minneapolis, MN, and was wondering if there will be an emergence near me that I can go to and photograph.

    I have loved cicadas–and other insects–since I was a little boy growing up in Cedar Rapids, IA. I used to climb up trees in the late summer and wait for the annual cicadas to climb down in the late evenings. Many times I caught them with my bare hands by moving very slowly and grasping them over the front of their wings where they hinge with my thumb and forefinger. Of course, the minute I did this they started making lots of noise and tried to flap their wings. So I would have this screaming, pulsating bug in my hand and would run inside with it and let it go in the house. My mom thought it was interesting, to say the least…


  49. Valerie says:

    It is not 5/31 and we have yet to see a single cicada in our subdivision in Batavia, Illinois.
    Does this mean that we will not get them? Is there a specific date that we will know that we are
    “safe” from a cicada emergence?

    I am a cicada-phobe.

  50. Shirley says:

    My son had the pleasure of sighting the cicadas in our own backyard on May 29th. We live in New Lenox, IL. He is in all his glory, not believing that we would see any Cicadas…

  51. CHERRIE says:

    I live in Rochester Indiana and we have not seen any, will we be getting them?

  52. Jon says:

    My wife is pretty sure she seen a female coming out in our garden yesterday! We live in East Troy, WI. Could this be one?

  53. Amanda says:

    Cicadas first sighted in my backyard in LaGrange Park, IL. on May 19th, 2007.
    As of this weekend, we can’t walk in the yard without stepping on one.
    They are facinating and because they don’t bite or sting, my 3-year-old
    likes to play with them and feel them crawl on his toes.

  54. Deborah says:

    anynoe seen any in the romeoville area?

  55. carol says:

    the cicadas are in lake geneva, watched the emergence tonight. very cool

  56. Mary says:

    Cicadas are out – here in Bull Valley, Illinois. They’re all over our back yard – resting under old logs and other stuff. They have burrowed up through large holes.

    There are a lot of them!

  57. Kay says:

    Tonight CBS 2 news at 10:00PM predicted the Chicago area will see the brood XIII cicada emergence beginning May 22nd. As a former left coaster, I’m completely unprepared for this event!!

  58. Pete says:

    The great move to the surface has begun. I’ve seen already several dozen little mud turrets popping up around my back yard.
    When you remove this turret covering you see a neat little round hole that looks like it fits a cicada nymph perfectly.
    It won’t be long now…

  59. Roy T. says:

    Hello Melissa,
    I would think if the field has been re-wooded for 30 or so years that the periodical cicadas could have re-established themselves. My grandfather owned about 270 acres of cornfields & re-planted trees on almost all of it back in the late 40’s, 50’s, & 60’s. The periodicals have “moved back in” to the whole 270 acres pretty much.


  60. Melissa says:

    I was wondering what kind of soil or dirt they live in for 17 years. I currently work on a project
    and years ago it was a soy bean field. Do you think there are cicadas in this type of dirt/soil?

  61. David Marshall says:

    It will be interesting to see if this holds generally for Illinois localities. In 1956, at Raccoon Grove, IL (35 miles SW of Chicago), Dybas and Davis measured the highest emergence density of periodical cicadas ever recorded. (This site has since been hit by Dutch Elm disease.) They had emergence traps out everywhere and the first nymphs began emerging on 4 June. The weather data for the nearest locality suggests a date closer to 22 May by Gene’s formula. Year to year temperature variation will add to the uncertainty too.

    Overall, cicadas will come out earlier in sunny spots and on south-facing slopes, and later in deep woods and gullies. I’m also guessing things will be earlier in the warm urbanized areas of Chicago (in past emergences cicadas were coming out of the ground in suburban yards around 24-25 May.)

    Since the emergence is usually strung out over one to two weeks, and since individual cicadas live for 2-3 weeks roughly, you can count on 3-4 weeks or so of noise once things get going.

  62. Roy T. says:

    Hello Valerie,
    I would expect about 4 solid weeks of action out of the cicadas after the last week of May. It is actually safe to have the party at any time the while cicadas are out & they may just drown out the kids laughing & screaming during their party.

    Hope this helps,

  63. Valerie says:

    Based on mean temperature, the predicted emergence in our area (Batavia, IL) is June 1, 2007. How long will they last? When is it safe to have an outdoor party with kids, sprinklers, splash pools etc?

  64. Roy T. says:

    Hey Sharon & all,
    Here is the best way to get to the average mean temps for April (so far):
    go to, type your zip in field at top, click on magnifying glass.
    when on page for your city scroll down to “History & Almanac” box & click on “April Calendar View”.
    when on calendar view page scroll up to “Monthly Summary” & find the mean temperature on the 2nd line
    in middle under “Avg:”. It will be listed in ºF/ºC. use ºC.

    Hope this helps,

  65. Dan says:

    It’s (19.4652 minus the temperature) divided by 0.5136

  66. Bob Jacobson says:

    I must be missing something: I just tried this for Chicago and got an answer of 379!! If I’m reading
    the formula correctly, it is E = (19.4652 t)/0.5136

    For Chicago it would become E = (19.4652)(10)/0.5136 = 194.652/0.5136 = 378.995

    I see a space between the 5 and the 2 as given
    above; did I misinterpret the formula?

    Thanks, Bob

  67. Dan says:

    Oi Veh — looks like May 30th at this point.

  68. Sharon says:

    Hello Ray:

    Great site.

    My husband grew up in the Chicago area (St. Charles, IL), and wants to go visit his family this year at the cicada time.

    I looked at the Weather Underground site, and did not find an ‘average mean temperature’ map. Lots of current temps, but not an average.

    Can you tell me your best current estimate of the emergence of Brood XIII in the Chicago area?

    Thanks a bunch!

    Best regards.

  69. Roy Troutman says:

    I looks as though only the far southern end of Wisconsin will see any Brood XIII so you are in the clear up north.

  70. Kathy says:

    Will the cicadas emerge in the Wisc. Northwoods? Like the Hayward and Minocqua areas?

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