Traditional infrared thermometers that point at your forehead are only measuring your skin temperature to try to identify whether you have an increased core body temperature (also called deep body temperature), which is a true index of fever, one of the leading signs of Covid-19. Extreme hot or cold weather changes your skin temperature but not your core body temperature, thereby giving false positives and false negatives in fever scans. https://machinesense.com/blogs/news/how-does-external-weather-affect-an-infrared-thermometer