Kelvin
"It is a unit of measurement for temperature of light sources. The Kelvin scale ranges from 2000 K to 10000 K, with 2000 K being the coldest tone & 10000 K being the warmest tone of the scale. Kelvin scale can also be looked in terms of white balances:
• 1000-2000 K: Candlelight
• 2500-3500 K: Tungsten Bulb (household variety)
• 3000-4000 K: Sunrise/Sunset (clear sky)
• 4000-5000 K: Fluorescent Lamps
• 5000-5500 K: Electronic Flash
• 5000-6500 K: Daylight with Clear Sky (sun overhead)
• 6500-8000 K: Moderately Overcast Sky
• 9000-10000 K: Shade or Heavily Overcast Sky "