The Old Farmer's Almanac assures us that we can tell the temperature from a cricket's chirps, so why even bother finishing this article? Case closed. The venerable institution that is the Old Farmer's Almanac (established in 1792!) says so. The only small issues are that the Old Farmer's Almanac also predicts the weather from a secret formula based on solar storms, and professionals guess the Almanac's success rate is roughly half of its advertised 80 percent accuracy [source: Neuman].
The science behind the Old Farmer's Almanac leaves a bit to be desired. And the waves of shame will really kick in when you realize how insane you must've been to think for even a fleeting moment that crickets have any interest in keeping track of the temperature.
Well, hide your shame for another day, because the Old Farmer's Almanac is right. It may seem like the world's most perfect old wives' tale, but a cricket's wings don't lie. They really can tell you the temperature if you listen closely enough. And before we get into the specifics of it, let's all just acknowledge that this is completely crazy, and the world is a freaking enchanted place where unicorns probably roam and magic is real.
That acknowledged, it's not random chance, nor is it wizardly fairy tale spells that make crickets living thermostats. It's science, and it actually makes a bit of sense, when you get down to it. So we'll start with an easy fact: Crickets are cold-blooded. That means they get as cold, or warm, as their surroundings. Easy enough, right? But if all cold-blooded creatures take on the temperature around them, why are crickets able to advertise it for all to hear? (And keep in mind, the snowy cricket is the kind most likely to give an accurate reading [source: Scientific American].)
That has to do with chemical reactions that take place in a cold-blooded animal's body. The cricket's "chirps" are muscle contractions that cause its wings to stroke, and those muscle contractions are only going to happen when the chemical reactions that regulate them take place. Those reactions are controlled by the Arrhenius equation [source: Crockett].
Now don't panic. The Arrhenius equation sounds complicated, but it's really just a handy way of saying that for chemical reactions to happen in an insect, a certain amount of "activation energy" is required. If the temperature goes up, those reactions happen with more speed; if the temperature goes down, so do the reactions. So the warmer it is, the more chirps you hear. Temperature falls? Less cricket racket [source: Scientific American].
But that's not all. To get a ballpark figure for what the temperature is in Fahrenheit, count cricket chirps for 15 seconds. Add 37 to the number, and you've got a decent estimate of how cold or warm it is outside.