about the weather

Astronomical dawn/dusk
The instant in the morning, when the centre of the Sun is at a depression angle of eighteen degrees (18°) below an ideal horizon.
Delta T
Calculated by subtracting the wet bulb temperature from the dry bulb temperature. (source)
Dew point
The temperature to which air must be cooled in order to produce condensation (dew). It represents how much moisture is in the air: the higher the dew point temperature, the greater the atmospheric moisture content. (source)
Ephemeris
Humidex
A measure of how hot we feel. It is an equivalent scale intended for the general public to express the combined effects of warm temperatures and humidity. (source)
UV Index
Solar Irradiance
Wet bulb temperature
The lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure. (source)
Windchill
The lowering of body temperature due to the passing-flow of lower-temperature air. (source)