The wiki descriptions for these tags are currently inconsistent:
To be used when the character on the picture is suffering from hot weather.
Used for pictures which show a character dressed up in a cold environment.
I think of the "cold" tag as being the exact opposite of the current "hot" tag wiki description, where the character is "suffering from cold weather". Sometimes this suffering comes from the fact that they're NOT dressed up for a cold environment, so the current wiki seems a little misleading to me.