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 is the Warm icon for Windows 10
. Here we go. Optimized for 32x32 px, these are the simplest icons in the line style. Downloadable formats are PNG and SVG, among others. Icons8 icon pack is unique in providing a huge number of icons designed by the same team of four designers who create the new icons every working day in the same style and with the same quality. Same cool as the Bat Face, huh.