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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. 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!

    Comment by Jeff Johnson — June 1, 2008 @ 4:59 am

  2. 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

    Comment by mike — June 2, 2008 @ 7:33 am

  3. Hi-
    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?

    Comment by ZekeL — August 8, 2008 @ 3:34 pm

  4. 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.

    Comment by Angela McGrady — March 2, 2011 @ 12:32 pm

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

    Comment by Dan — March 3, 2011 @ 5:19 pm

  6. 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!!

    Comment by Maria — March 16, 2011 @ 8:08 pm

  7. 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).

    Comment by Dan — March 16, 2011 @ 8:15 pm

  8. 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?

    Comment by Alice Nelsen — May 30, 2011 @ 7:08 pm

  9. 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.

    Comment by Dan — May 30, 2011 @ 7:51 pm

  10. 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.

    Comment by nancy — July 3, 2011 @ 11:55 am

  11. […] speaking, once the ground temperature gets to 64 degrees Fahrenheit they will emerge. There’s an emergence formula too. Brood XIX cicadas in Georgia will most likely emerge before the cicadas in Illinois, for example, […]

    Pingback by Cicada Mania: A Brood XIX Periodical Cicada Primer — November 3, 2012 @ 12:41 pm

  12. […] Gene Kritsky’s formula, and the Weather Underground, I’ve pulled together some sample emergence predictions. Chances […]

    Pingback by Cicada Mania: 17 year cicada emergence predictions — November 3, 2012 @ 1:09 pm

  13. […] will emerge once the temperature is right, typically at dusk. The best method we know of is using Gene Kritsky’s emergence formula. This is a tool that will allow you to determine the approximate time when the cicadas will emerge […]

    Pingback by Cicada Mania: Brood XIV: When, Where and What do they look like? — November 3, 2012 @ 1:12 pm

  14. […] 22nd Filed under: Brood XIII — by Dan Mozgai @ 5:14 am According to the cicada emergence formula, it looks like May 22nd might be the date. Comments […]

    Pingback by Cicada Mania: May 22nd — November 3, 2012 @ 1:17 pm

  15. […] year Gene’s emergence formula calculator (try it!) did a good job of predicting the Brood XIII emergence, and the 2008 temperature study […]

    Pingback by Cicada Mania: 2008 Cicada Temperature Study — November 14, 2012 @ 7:57 pm

  16. […] Check the Brood II map to see if they’ll be visiting your town, and use the emergence formula to get a better idea of when they’ll arrive. If you’re unlucky enough to have it fall near your wedding day, then talk to the neighbors […]

    Pingback by Will the 17-Year Cicada Spoil Your Outdoor Wedding? | Lombok Weddings — March 15, 2013 @ 11:24 am

  17. Supposed to be May 16th for zip: 08210 (Cape May Court House), based on average for April.

    Comment by Daniel S — April 1, 2013 @ 7:27 am

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

    Comment by Jenn — April 9, 2013 @ 4:06 pm

  19. 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

    Comment by Dan — April 9, 2013 @ 8:33 pm

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

    Comment by Larae Zeman — April 11, 2013 @ 9:19 am

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

    Comment by Dan — April 11, 2013 @ 10:11 am

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

    Comment by Anya — April 12, 2013 @ 5:46 pm

  23. 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.

    Comment by Dan — April 13, 2013 @ 9:40 am

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

    Comment by Anya — April 13, 2013 @ 10:38 am

  25. 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.

    Comment by Dan — April 14, 2013 @ 5:00 am

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

    Comment by Anya — April 14, 2013 @ 9:50 am

  27. 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!

    Comment by Erin — April 20, 2013 @ 10:20 am

  28. @Erin,

    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

    Comment by Dan — April 21, 2013 @ 7:34 am

  29. 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!!

    Comment by Karen — April 27, 2013 @ 6:42 am

  30. 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.

    Comment by Dan — April 30, 2013 @ 2:42 am

  31. 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

    Comment by Rayne — May 7, 2013 @ 3:24 pm

  32. Maybe sure you use Celsius and not Fahrenheit.

    Comment by Dan — May 7, 2013 @ 6:51 pm

  33. 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.

    Comment by Jenn — May 12, 2013 @ 2:29 pm

  34. 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!

    Comment by Betsy — May 19, 2013 @ 5:34 pm

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

    Comment by Dan — May 19, 2013 @ 5:44 pm

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

    Comment by Jeff — May 22, 2013 @ 7:09 pm

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

    Comment by Dan — May 23, 2013 @ 12:29 pm

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

    Comment by Jeff — May 22, 2013 @ 7:12 pm

  39. 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!!

    Comment by Jeff — May 23, 2013 @ 3:41 pm

  40. It could be!

    Comment by Dan — May 23, 2013 @ 7:39 pm

  41. 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!

    Comment by Jessica — February 2, 2014 @ 7:55 pm

  42. 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.

    Comment by Dan — February 4, 2014 @ 5:45 am

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