This information was posted in a comment, but it’s important enough to place on the homepage in a post:
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 64° Fahrenheit 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.