A story on the news last night brought back to mind what I knew as a kid. If you count the number of cricket chirps in 14 seconds and add 38, it will be the exact Fahrenheit temperature.
I never can remember the damn formula for converting F-to-C. So, for those enlightened countries that use the metric system, can some genetic scientist develop a Celsius cricket? Save a fortune on thermometers.
Our cats hunt down and eat all crickets around here, so a Celsius cricket wouldn’t help. Maybe one that could post it on the Web, so the cats didn’t hear…
The formula’s simple enough, you just need to know that 0C = 32F, and 1 degree C = 1.8 degrees F precisely.
so 10C = 32+18 = 50F
20C = 32+36 = 68F
30C = 32+54 = 86F and so on.
working the other way, you just take off the 32, then divide by 1.8, i.e. multiply by 5/9.
so 75F = 43 x 5/9 = 24C.
The temperature in Fahrenheit is C x 14 + 38, where is C is the chirps per second. In Celsius, that’ll be (C x 14 + 38 - 32) x 5/9 == C x 8 + 3 (approximately).
So, for the Celsius cricket, count the number of chirps in 8 seconds and add 3.
Nothing to do with crickets but I surprised myself the other day when I took a dog’s temperature and discovered the thermometer was set to Celsius. Instead of sticking the thermometer up the dog’s butt again I just did the math, amazingly I remembered the formula without having to look it up.* So you never know, maybe you could remember the formula if you tried. 
Oh man, Pleonast, I never fail to be astonished at the depth and bredth of knowledge that Dopers posses (or for the scientific term, "smartness). Thanks