If An Air Frost Is Recorded When The Temp Drops Below 0c, Why Do I See Frosty Patches Up To 3c?

[leicsnow]

Even when my weather station records above 0c, I can see frost on my garage and my parents have to scrape their cars

[4wd]

Objects radiate heat under clear skies, and can become considerably colder than the surrounding air.

You would find a thermometer placed close to the ground reads far lower overnight under clear skies too.

[Nick L]

What you have described is a ground frost, as 4wd says, the ground/objects on the ground radiate heat quickly to the surrounding air, causing a temperature inversion just a few cm off the ground. The ground can be a few c colder than the air above, so even though your weather station says it's above freezing in the air, the ground below can be at or below freezing.

The other type of frost is an air frost, this is when the air is below freezing too

[gottolovethisweather]

Hi Tellow,

I did a post about this phenomenon on my blog which you can see here - http://wp.me/p1OoP4-4k

Hoping that helps.

Kind Regards

gottolovethisweather

[4wd]

It's really just an extension of what happens when dew forms.

Somehow it seems easier to understand that water is condensing from relatively warm air onto the colder surfaces.

[knocker]

Illustrated quite easily by looking at the overnight min temps last night and the grass min.

http://www.met.reading.ac.uk/~brugge/06.html