Gasoline "Snow"?

I agree it possibly had something to do with local chilling taking
water out of the local air. But air at that temp already has very
little water vapor in it. That seems hard to believe, and I've never
seen what you described. Huh!

Gasoline will dissolve a small amount of water into solution. The
amount that will dissolve goes down with temperature, creating a fine
ice crystal "snow" in your fuel tanks under severe cold conditions.
When flying, this snow will accumulate on any filter screens (such as
in the gascolator) and can eventually block your fuel flow requiring
only a very tiny amount of water.

I know - it happened to me (see Sport Aviation Dec 1986)

Remember that your fuel that morning was probably colder than it had
ever been since it was made at a refinery in some warmer climate. For
that reason I add a small amount of isopropyl alcohol to my fuel
whenever the local temps go below freezing.

Beware of fuel that has been severely chilled before it was last
filtered.