A Rough Estimate
The frequency of a cricket’s chirping varies according to the surrounding temperature. To get a rough estimate of the temperature in degrees Fahrenheit, count the number of chirps in 15 seconds and then add 37. The number you get will be an approximation of the outside temperature. Then go check it against weather.com or something else empirical. Science!
However this is just one possible formula. While research has added validity to the first formula, the following formula also has some evidence behind it: count the number of chirps in 13 seconds and add 40 degrees (for Fahrenheit). This first particular formula has its roots in the Old Farmer’s Almanac.
Of course, to utilize these formulas, there have to be crickets around, and each is only valid down to about 55 degrees (F), as below this temperature crickets are either not around or not in the mood.
This means that the old wisdom of “crickets chirp more slowly when it is cold out”, or vice versa, is also true.
So, how do crickets make that chirping sound?
Usually, the males are the “singers.” The male cricket rubs a scraper (a sharp ridge on his wing) against a series of wrinkles, or “files”, on the other wing. The tone of the chirping depends upon the distance between the wrinkles.
There are several reasons why crickets chirp. They may be:
Calling to attract a female with a loud and monotonous sound
Courting a nearby female with a quick, softer chirp
Behaving aggressively during the encounter of two males
Sounding a danger alert when sensing trouble
Go out and try your bug thermometer!