You are outdoors without your thermometer and wonder “what’s the temperature?” If you listen to the crickets, there is an easy formula to calculate it: Count the chirps in 15 seconds and add 40. The result is the temperature in Fahrenheit. How does it work? A Swedish chemist, Savante Arrhenius, described a similar equation in 1897 to explain chemical reaction rates and their response to temperature. The chirp rate is controlled by metabolic reactions and is faster when it is warm and slower when it is cool. Is it accurate? Studies have shown that it is accurate to within a degree or two. You just need to be careful in counting the chirps, and be able to hear the crickets over the noisy cicadas.
Mary Knapp, Weather Data Library