Mean monthly frequency (%) of clear and overcast sky conditions (midnight to midnight observations).
58° 21'N / 134° 35' W
12.1 ft. above sea level
midnight - midnight
sunrise - sunset
Analyses are based on hourly observations for the years 1971 - 1998.
Clear skies are defined as 0 to 0.30 coverage, partly cloudy 0.40 to 0.70, and cloudy skies 0.80 to 1.00.
Mean monthly frequency (%) of clear, partly cloudy, and cloudy sky condition and mean cloudiness (fraction of sky coverage).
| Sky Condition |
Jan
|
Feb
|
Mar
|
Apr
|
May
|
Jun
|
Jul
|
Aug
|
Sep
|
Oct
|
Nov
|
Dec
|
| Clear |
22
|
21
|
21
|
19
|
17
|
13
|
13
|
17
|
13
|
10
|
11
|
15
|
| Partly Cloudy |
6
|
6
|
7
|
11
|
11
|
10
|
9
|
10
|
8
|
6
|
5
|
6
|
| Cloudy |
72
|
73
|
72
|
70
|
72
|
77
|
78
|
73
|
79
|
84
|
84
|
79
|
|
Mean Cloudiness
|
0.76
|
0.77
|
0.76
|
0.76
|
0.77
|
0.82
|
0.83
|
0.78
|
0.83
|
0.87
|
0.86
|
0.82
|