This thermal visualization is based on a band B06 (a band is a region of the electromagnetic spectrum; a satellite sensor can image Earth in different bands). At the central wavelength of 10400-12500 nm it measures in the thermal infrared, or TIR. Instead of measuring the temperature of the air, like weather stations do, band B06 reports on the ground itself, which is often much hotter. Thermal band B06 is useful in providing surface temperatures and is collected with a 60-meter resolution, resampled to 30-meter. More info here.
Thermal composite over northern Tunisia. Acquired on 2001-06-23.