It's an icon representing a medical thermometer. The thermometer is pointing down and to the left. There are hash marks on it to show where the temperature would be and a line going from the base through the center of the thermometer.
This Warm icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 6,000 icons, all in the same style and quality.