# Frost

**URL:** <https://boards.straightdope.com/t/frost/165449>\
**Category:** Factual Questions\
**Created:** [March 31, 2003, 3:23pm UTC](https://boards.straightdope.com/t/frost/165449 "2003-03-31T15:23:36Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![chickendoc](https://avatars.discourse-cdn.com/v4/letter/c/82dd89/32.png) [@chickendoc](https://boards.straightdope.com/u/chickendoc)\
**Post date:** [March 31, 2003, 3:23pm UTC](https://boards.straightdope.com/t/frost/165449/1 "2003-03-31T15:23:36Z")

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I was having a discussion with a coworker about the frost we had this weekend. Supposedly the low this weekend was only 38°F. How does frost form when the air temp is higher than 32°F?

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [March 31, 2003, 3:28pm UTC](https://boards.straightdope.com/t/frost/165449/2 "2003-03-31T15:28:05Z")

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I believe this may be what is called ‘radiation frost’; the ground (and other objects) cool to a lower temperature than the air by losing heat through radiation.

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**Author:** ![chickendoc](https://avatars.discourse-cdn.com/v4/letter/c/82dd89/32.png) [@chickendoc](https://boards.straightdope.com/u/chickendoc)\
**Post date:** [March 31, 2003, 3:30pm UTC](https://boards.straightdope.com/t/frost/165449/3 "2003-03-31T15:30:23Z")

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Mangetout:

Radiation frost sounds like a plausible explanation to me. I’ll look it up.

Thanks

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**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\
**Post date:** [March 31, 2003, 3:31pm UTC](https://boards.straightdope.com/t/frost/165449/4 "2003-03-31T15:31:05Z")

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When the news reports 38 as the low, they are reffering to air temps. Of course, things like car windows and car hoods can cool below 38.

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [March 31, 2003, 3:31pm UTC](https://boards.straightdope.com/t/frost/165449/5 "2003-03-31T15:31:55Z")

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> [@](#):
>
> A thermometer indicates the temperature where the thermometer is, usually a few feet above the ground. Because cold air sinks relative to warmer air and because the ground can cool very quickly the temperature at ground level can be cooler than a few feet higher where the thermometer is, even though the thermometer indicates a temperature that is above freezing, it can easily be below freezing a few feet lower.

And

> [@](#):
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> Certain materials like glass and car metal radiate heat quickly and therefore cool quickly. Also, areas like rooftops or high plateaus, because of their exposure lose heat through re-radiation very quickly and tend to receive frost before sheltered areas.

From[this article](http://www.shorstmeyer.com/wxfaqs/frost/frost.html).

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**Author:** ![chickendoc](https://avatars.discourse-cdn.com/v4/letter/c/82dd89/32.png) [@chickendoc](https://boards.straightdope.com/u/chickendoc)\
**Post date:** [March 31, 2003, 3:34pm UTC](https://boards.straightdope.com/t/frost/165449/6 "2003-03-31T15:34:48Z")

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## quote:

## Certain materials like glass and car metal radiate heat quickly and therefore cool quickly. Also, areas like rooftops or high plateaus, because of their exposure lose heat through re-radiation very quickly and tend to receive frost before sheltered areas.

What about my pepper and tomato plants?