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We explain how to use the “cricket thermometer” method. And next time there’s a warm evening, count the cricket chirps!

The Cricket as a Thermometer

Crickets are cold-blooded and take on the temperature of their surroundings. In 1897, a scientist named Amos Dolbear published an article titled “The Cricket as a Thermometer” that noted the correlation between the ambient temperature and the rate at which crickets chirp.

The insects’ muscles contract to produce chirping based on chemical reactions. The warmer the temperature, the easier the cricket’s muscles activate, so the chirps increase. The cooler the temperature, the slower the reaction rate, and the less frequent the chirps are, the lower the chirp rate.

Cricket Temperature Formula

The formula expressed in that article became known as Dolbear’s Law. It’s surprisingly simple:

To Convert Cricket Chirps to Degrees Fahrenheit: 

Just count the number of chirps in 14 seconds, then add 40 to get the temperature.

The number you get will be an approximation of the outside temperature.

Example: 30 chirps + 40 = 70°F

To Convert Cricket Chirps to Degrees Celsius: 

Count the number of chirps in 25 seconds, divide by 3, then add 4 to get the temperature.

Example: 48 chirps /(divided by) 3 + 4 = 20°C

Use the method you prefer and then convert to degrees Celsius or Fahrenheit using our temperature converter.

To find out this week’s weather in your region, see our seven-day forecast. (See which one’s more accurate!)

How Do Crickets Chirp?

So, how and why do crickets make that chirping sound, anyway? 

Chirping is a cricket’s way of communicating. Male crickets use chirping to attract females, scare off other males, or warn of danger.

Contrary to popular belief, crickets do not use their legs to chirp! In fact, crickets produce the iconic sound by rubbing the edges of their wings together. 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.

It’s a little similar to the way you run your thumb against a comb. 

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 between two males
• Sounding a danger alert when sensing trouble

Crickets are part of the family Orthoptera (grasshoppers and katydids). Enjoy more cricket facts and how to take care of crickets.

The Cricket Chirp Challenge

Next time you hear a cricket, test out its temperature-telling prowess and let us know how it goes! 

Here’s a fun challenge:

1. Go outside in the evening if you know a place where crickets chirp (or have a pet cricket).
2. Bring a stopwatch (a mobile phone has one). Pick out the chirping sound of a single cricket.
3. Just count the number of chirps in 14 seconds, then add 40 to get the temperature. (Perhaps do this a few times, just to see if you’re getting the same number. Take the average.)
4. Check the temperature on an outdoor thermometer. Is it close? 
5. Try it again on a cooler evening. See how the chirp frequency changes.

Start to notice the chirps of the crickets when you’re outdoors. It’s nature’s thermometer! 

Enjoy learning about crickets and temperature? Find out how other insects predict the weather.