Nature’s Thermometer

Much like a sluggish bumble bee on a cool spring morning or a lizard sunning on a rock, crickets move slower in cooler temperatures. Each of these animals is an ectotherm — their body temperature depends on the temperature of their environment. As crickets warm, they can rub their wings together faster, which is how male crickets make the nightly repetitive chirp they use to attract mates. 

The relationship between cricket chirping and temperature has been noted for a long time. In Western science, it is called Dolbear’s law after the most widely referenced early publication on the phenomenon published in 1897 by Amos Dolbear. His observations showed that you can count the number of chirps per 15 seconds, add 40, and that will give you the temperature in Fahrenheit (F). 

Dolbear's law

Temperature (F) = number of cricket chirps in 15 seconds + 40