UV index Current Stats for Foresthill, CA.
UV Graph
 Solar: Current / Trends / Highs  UV: Current / Trends / Highs
 Current: 0 W/m2  Current: 0.0 index None  
 24hrs ago: 0 W/m2  24hrs ago: 0.0 index None  
 48hrs ago: 0 W/m2  48hrs ago: 0.0 index None  
 72hrs ago: 0 W/m2  72hrs ago: 0.0 index None  
 96hrs ago: 0 W/m2  96hrs ago: 0.0 index None  
 Today High: 976 W/m2 at 12:57pm  Today High: 10.2 index at 1:21pm  Very High 
 Yest. High: 972 W/m2 at 12:54pm  Yest. High: 10.9 index at 12:52pm  Extreme 
 Month High: 1169 W/m2 at 6/8/24  Month High: 11.3 index at 6/8/2024  Extreme 
 Year High: 1406 W/m2 at 4/14/24  Year High: 11.3 index at 6/8/2024  Extreme 

7 day UV Index Forecast for Foresthill, CA.


Friday Saturday Sunday Monday Tuesday Wednesday
UV Index UV Index UV Index UV Index UV Index UV Index
9.9 9.6 8.2 7.6 8.4 8.7
 Very High   Very High   Very High   Very High   Very High   Very High 

UV Index Legend

UV Index Scale
UV Forecast Maps
UV forecast map
UV forecast map
Maps Compliments of National Weather Service


Curious about Ultraviolet Radiation?


Ultraviolet Radiation(UV)Ultraviolet Radiation(UV): Light emmitted from the sun which is harmful to the skin and eye. The wavelengths of the light, only sightly higher than what we see as the color violet; hence the name ultraviolet.
      The ozone layer around the earth is a layer of triatomic molecules made of three oxygen atoms. This filters light from the sun, including much of the harmful UV light from reaching the earths surface. The ultraviolet radiation that reaches the earth is known as UVA and UVB.

      UVA is the largest UV wavelength. It stays between 320-400nm (nanometers). It is also the least dangerous of the 3 types of UV. More recent studies have shown it to be more dangerous than previously assumed. Being a larger wavelength most of it penetrates the ozone layer, which also causes it to reach deeper into the skin than UVB and UVC. Recent studies have shown it to cause cancer deep in the skin. UVB stays mainly on the top layer of the skin but is proven to be more dangerous as it causes cancer in a shorter period of time.

      UVB is a smaller wavelength than UVA but larger than UVC. It is between 280-320nm. Being a smaller wavelength than UVA more of this is blocked by the ozone layer. As the sun is closest to the earth and the angle is more direct during the summer months more UVB penetrates through the ozone making it the most dangerous time of year to be out in the sun. UVB burns the skin and eye which cause skin cancer and cataracks.

      UVC is the smallest of the three wavelength. Making it the most dangerous of the three wavelengths. It stays between 200-280nm. Being a smaller wavelength almost alll of it is blocked by the ozone layer. UVC is so dangerous that even when exposed for a short time it can cause death. One of the many reasons astronauts wear space suits is to be protected from UVC. So in the case of ultraviolet radiation the higher the frequency or smaller the wave the more damaging to the human body it is. So it makes you wonder if we could ever inhabit a planet like mars with such a thin ozone layer. We would be in danger of harmful UV rays.


How to stay safe form harmful UV rays


  • Listen to warnings; Watch the daily UV index. The higher the warning the higher the risk for over exposer to UV
  • Limit the time you spend in the sun. The sun’s rays are strongest between 10 am and 4 pm.
  • Wear sunscreen with at least spf 15
  • Wear tightly woven clothing and wide brimmed hats if possible
  • Wear UV protective sunglasses
  • Different surfaces can reflect more UV. Surfaces like
    • Snow
    • Sand
    • Concrete
  • Be aware of your elevation. The higher you are in elevation, the higher the UV. UV is increased 2% for every 1000 feet increase in elevation.
  • Whenever possible, stay in the shade.
     UV Page Created By Sarah Dondelinger
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