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Weather Data Measured & Calculated
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Weather Envoy can also display UV Index, an intensity measurement first
defined by Environment Canada and since been adopted by the World Meteo-
rological Organization. UV Index assigns a number between 0 and 16 to the
current UV intensity. The US EPA categorizes the Index values as shown
below. The lower the number, the lower the danger of sunburn. The Index
value published by the U.S. National Weather Service is a forecast of the next
day’s noontime UV intensity. The Index value displayed by the Weather
Envoy is the result of a real-time measurement.
EvapoTranspiration (ET)
Note: Requires optional solar radiation sensor (#6450, included on Vantage Pro or Vantage
Pro2 Plus weather stations).
EvapoTranspiration (ET) is a measurement of the amount of water vapor
returned to the air in a given area. It combines the amount of water vapor
Table A3: UV Index and Exposure Category
Index Values Exposure Category
0 - 2 Minimal
3 - 4 Low
5 - 6 Moderate
7 - 9 High
10+ Very High
UV Dose that Causes Sunburn
All Burn
Some Burn
I
II
III
IV
V
VI
1
2
3
4
Skin Type (Environment Canada)
Skin Phototype (EPA)
UV Dose (MEDs)
12345
6
20 40 60 80 100 120
mJ/cm
2