(WGNO) — Crickets can’t predict the weather, but their chirp can tell you the temperature.

Crickets are ectotherms — meaning their body temperature depends on the temperature of their surrounding environment.

Much like a sluggish bumblebee on a cool spring morning or a lizard sunning on a rock, crickets move slower in cooler temperatures.

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 the 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 article is called “The Cricket as a Thermometer,” according to Almanac.com, and it discusses the correlation between a cricket’s chirp rate and the ambient temperature.

“The warmer the temperature, the easier the cricket’s muscles activate, so the chirps increase,” according to the Almanac. “The cooler the temperature, the slower the reaction rate, and the less frequent the chirps.”

Dolbear’s observations showed that you can count the number of chirps per 15 seconds, add 40, and that will give you the temperature in Fahrenheit.

The National Weather Service Weather Forecast Office in El Paso, Texas, has set up an online calculator based on Dolbear’s law.

To use the calculator, users simply enter the number of chirps, and it will provide the temperature.