In article om, "m35603" wrote:

Frost forms when a surface cools to a temperature which is colder than
the dewpoint of the air next to the surface. The frosted area of the
roof must be cooler than the rest of the roof and has nothing to do
with moisture in the roof itself.

That does make sense, but why are the shingles wet when it's not below
freezing? That's why I was thinking that it's this wetness that causes
the frost.

Same reason. The only difference between dew and frost is the temperature.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.