Yeuph t1_itziw47 wrote on October 27, 2022 at 1:30 PM

Reply to comment by James19991 in Are we set for the latest first freeze ever this year? by babyyodaisamazing98

How does that work? Frost without freezing?

James19991 t1_itzkvvh wrote on October 27, 2022 at 1:45 PM

Official temperatures are measured 6 ft above the ground or so, and cold air sinks, so if it's 33 or 34 above the ground, it's totally possible for it to be 32 or 31 at ground level in certain areas.

distilledfluid t1_itzoqoz wrote on October 27, 2022 at 2:12 PM

Correct!

Can get more information on the same question from the NWS link here:

https://www.weather.gov/abr/frost_fall2012

James19991 t1_itzs9h9 wrote on October 27, 2022 at 2:36 PM

Good stuff, thanks

LordApocalyptica t1_iu05jdn wrote on October 27, 2022 at 4:03 PM

Also the heat exchange mechanism of phase change means that at a micro environmental level you can have phenomena like frost happening even if the ambient temp is slightly higher

KentuckYSnow t1_itzkw4b wrote on October 27, 2022 at 1:45 PM

Temps at ground level can be a few degrees colder than just a few feet higher and dip below 32, at which point the vapor in the air can freeze.