Question 1

Why can RH be high on a cold morning and low in the afternoon with the same air?

Accepted Answer

The moisture content stays the same, but warming raises e_s, so RH falls; the dew point barely changes.

Question 2

What does 100% RH mean?

Accepted Answer

The air temperature equals the dew point, so the air is saturated and fog, dew or condensation can form.

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