Mean monthly frequency (%) of clear and overcast sky conditions (midnight to midnight observations).
59° 31'N / 139° 38' W
27.9 ft. above sea level
midnight - midnight
sunrise - sunset
Analyses are based on hourly observations for the years 1971 - 1994.
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 |
20
|
23
|
23
|
19
|
13
|
10
|
10
|
14
|
16
|
14
|
18
|
16
|
| Partly Cloudy |
8
|
8
|
10
|
11
|
11
|
10
|
8
|
10
|
9
|
9
|
10
|
8
|
| Cloudy |
72
|
69
|
67
|
70
|
76
|
80
|
82
|
76
|
75
|
77
|
72
|
76
|
|
Mean Cloudiness
|
0.77
|
0.74
|
0.73
|
0.76
|
0.81
|
0.85
|
0.86
|
0.81
|
0.80
|
0.81
|
0.77
|
0.80
|