“Chirp, chirp!” We are all familiar with the repetitive sound of a cricket chirping on a warm summer evening, but did you know those chirps are a cricket's way of telling the temperature? Before we dive into that connection, let’s understand why and how crickets chirp.

Crickets are not trying to be meteorologists, but they are trying to attract the attention of a potential mate. Male crickets rub their wings together as a mating call; the result is the famous chirping noise. So, how does this relate to the temperature? 

 

Crickets are ectotherms (more commonly known as cold-blooded), meaning that their body temperature depends on the temperature of their surrounding environment. The warmer it is outside, the warmer the crickets are, and the quicker they can rub their wings together. Therefore, the higher the temperature, the more crickets can chirp in a given time.

This relationship has been recognized for over a century, first published by Amos Dolbear in 1897. Through a series of observations, Dolbear developed a simple formula to calculate temperature based on the frequency of a cricket's chirping. This formula is now known as Dolbear’s Law: 

Temperature (F°) = # of chirps in 15 seconds + 40

 

No one is 100% certain of what species of cricket Dolbear was listening to, but it is believed to be the snowy tree cricket. Those crickets have now earned the nickname “the thermometer cricket." 

The exact rate at which crickets chirp does vary slightly by the type of cricket, meaning that while Dolbear’s Law can give a useful estimate of the current temperature, it might not be exact for your location. 

To find the exact formula for your location, you can record the number of chirps at several different temperatures and plot them on a graph. Using a line of best fit, you will be able to find the relationship between the temperature and the crickets in your backyard!