WARM: The American Sign Language (ASL) sign for "warm / heat / warmth"
The sign for "warm" starts in the same handshape as the sign for FOOD. It is a "modified O" hand.  Think of your warm breath rising upward in the wintertime. 

WARM:

Here it is again folks, this time a bit from the side:

Sample sentence:  Do you like warm cookies and milk?

Notes:

See: HOT

See: FOOD

See: SUN