Count the number of cricket chirps in 14 seconds and then add 40. The number will be very close to the air temperature. An alternate approach is to note that they chirp 72 times per minute at 60F. For every additional four chirps, add a degree to 60F, and for every four chirps less, subtract a degree for 60F.
Ahh, the things you learn working at the Air Force Combat Climatology Center, surrounded by meteorologists.