The Mudcat Café TM
Thread #148889 Message #3462433
Posted By: JohnInKansas
06-Jan-13 - 10:28 PM
Thread Name: BS: How Cold Can it Get?
Subject: RE: BS: How Cold Can it Get?
A minor factor that may affect objects in very cold weather, particularly parked (not running) vehicles, is that on a clear night when there's little wind the night sky is a very effective heat sink and thermal radiation from objects "with a clear view to the sky" can lose enough heat to be quite a bit colder than the free air temperature.
Some Army buddies doing vehicle "winter tests" in Alaska (while I was loafing around destroying trucks in Yuma) documented overnight vehicle surface temperatures generally about 15-20 F (8-11 C) lower than surrounding air temperatures.
The effect is seldom apparent until air temps get down around -10F (-20C), but seems to be more effective as the air temp drops below about there, although a good breeze or cloud cover can mostly wipe it out.