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