Our hand warmers reach a max temperature of about ~140 degrees F, with an average temp around 135 degrees F. The exact temperature will vary slightly depending on environmental conditions and the amount of air the warmer is exposed to. 140 degrees F is generally accepted as the high end of the range for safe and comfortable heat. For maximum comfort, we recommend using these warmers outside of a glove liner or other layer of clothing; or if your gloves have a zipper pocket, our warmers will fit nicely inside!