W
E A T H E R
D
A T A
M
E A S U R E D
& C
A L C U L A T E D
UV (Ultra Violet) Radiation
30
UV Dose and Sunburn
- Use this plot to estimate the MED dose leading to sun-
burn. A person with Type II (Environment Canada) skin type might choose 0.75
MED as the maximum for the day; in contrast, a person with Type V (Environ-
ment Canada) Skin Type might consider 2.5 MEDs a reasonable dose for the day.
NOTE: the Weather Envoy assumes a Fitzpatrick (Environment Canada) Skin
Type of II.
Weather Envoy can also display UV Index, an intensity measurement first defined
by Environment Canada and since been adopted by the World Meteorological
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 mea-
surement.
T
ABLE
A3: UV I
NDEX
AND
E
XPOSURE
C
ATEGORY
I
NDEX
V
AL
-
UES
E
XPOSURE
C
ATE
-
GORY
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 T
ype (Environment Canada)
Skin Phototype (EP
A)
UV Dose (MEDs)
1
2
3
4
5
6
20
40
60
80
100
120 mJ/cm
2
