Powell River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Powell River clear sky chart from 2005-11-06 to 2024-01-15.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
34%
22653
5%
74881
3%
22595
36%
22595
7%
63399

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
18%
850
2%
2836
1%
846
19%
846
2%
2650
January11th to 20thNight
24%
820
4%
2760
1%
820
27%
820
4%
2462
January21st to endNight
25%
854
3%
2845
2%
854
26%
854
4%
2570
February1st to 10thNight
24%
720
3%
2340
1%
720
26%
720
4%
2098
February11th to 20thNight
31%
700
7%
2274
5%
700
34%
700
7%
1899
February21st to endNight
26%
592
7%
1924
4%
592
30%
592
4%
1675
March1st to 10thNight
28%
720
4%
2083
2%
720
31%
720
6%
1831
March11th to 20thNight
26%
720
4%
1980
2%
720
27%
720
5%
1761
March21st to endNight
28%
792
5%
2171
2%
792
30%
792
6%
1922
April1st to 10thNight
31%
720
3%
1800
0%
720
32%
720
8%
1587
April11th to 20thNight
32%
535
9%
1603
5%
535
35%
535
9%
1335
April21st to endNight
35%
533
6%
1613
4%
533
36%
533
9%
1327
May1st to 10thNight
40%
360
7%
1440
8%
360
44%
360
8%
1146
May11th to 20thNight
48%
354
6%
1416
8%
354
52%
354
8%
1118
May21st to endNight
41%
389
3%
1371
3%
388
43%
388
7%
1139
June1st to 10thNight
40%
360
1%
1260
1%
360
40%
360
6%
1038
June11th to 20thNight
38%
360
1%
1260
0%
360
38%
360
7%
1058
June21st to endNight
50%
360
3%
1260
1%
360
51%
360
11%
970
July1st to 10thNight
55%
350
4%
1225
2%
350
56%
350
13%
909
July11th to 20thNight
56%
348
8%
1218
6%
348
58%
348
16%
853
July21st to endNight
67%
394
11%
1329
14%
372
70%
372
19%
882
August1st to 10thNight
65%
429
9%
1495
11%
427
67%
427
14%
1073
August11th to 20thNight
68%
534
13%
1602
10%
534
72%
534
21%
1113
August21st to endNight
55%
594
10%
1782
7%
594
57%
594
15%
1362
September1st to 10thNight
60%
714
15%
1794
8%
714
63%
714
24%
1295
September11th to 20thNight
50%
720
13%
1872
8%
720
51%
720
16%
1468
September21st to endNight
43%
720
9%
2016
7%
720
44%
720
12%
1637
October1st to 10thNight
45%
720
7%
2160
6%
720
46%
720
12%
1703
October11th to 20thNight
37%
720
4%
2160
3%
720
39%
720
9%
1794
October21st to endNight
29%
792
5%
2556
3%
792
33%
792
7%
2158
November1st to 10thNight
21%
740
3%
2590
2%
740
23%
740
3%
2336
November11th to 20thNight
20%
760
3%
2660
1%
760
22%
760
3%
2405
November21st to endNight
21%
760
3%
2660
1%
760
23%
760
3%
2408
December1st to 10thNight
24%
836
3%
2821
0%
836
27%
836
4%
2499
December11th to 20thNight
18%
850
0%
3516
0%
849
18%
849
2%
3275
December21st to endNight
16%
933
1%
5189
1%
905
19%
905
2%
4643

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
21%8%36%5%3445%6%33%
74712
Night
26%10%46%5%34445%28%
75070
TransparencyDay
35%39%11%10%41
74394
Night
40%38%9%9%3
74906
SeeingDay
25%11%23%24%14%3
14496
Night
32%8%19%24%16%3
22659

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
39%12%46%6%3443315%
1329
11th to 20thDay
31%13%5%7%7%5%5%5%45%12%
1288
21st to endDay
32%13%410%7%5%444412%
1507
February1st to 10thDay
34%12%36%445%5%45%18%
1620
11th to 20thDay
27%11%37%6%45%446%23%
1575
21st to endDay
25%11%47%6%45%6%5%6%23%
1332
March1st to 10thDay
28%11%46%5%445%6%5%23%
1875
11th to 20thDay
27%13%5%8%6%35%445%21%
1980
21st to endDay
25%11%38%6%35%445%25%
2185
April1st to 10thDay
24%12%48%6%35%5%47%24%
2160
11th to 20thDay
22%9%47%5%35%5%6%6%29%
2303
21st to endDay
23%8%36%5%345%5%6%32%
2345
May1st to 10thDay
17%6%36%5%35%5%5%7%39%
2520
11th to 20thDay
16%8%36%6%45%5%6%9%34%
2477
21st to endDay
18%7%36%5%45%45%7%36%
2902
June1st to 10thDay
20%7%37%5%345%6%7%33%
2700
11th to 20thDay
15%7%37%7%45%5%6%9%32%
2700
21st to endDay
14%6%35%5%345%6%8%42%
2700
July1st to 10thDay
13%43443346%7%50%
2700
11th to 20thDay
10%434434448%53%
2700
21st to endDay
7%41332345%7%62%
2908
August1st to 10thDay
10%314424446%58%
2433
11th to 20thDay
7%42443445%8%57%
2298
21st to endDay
11%6%25%435%5%5%8%48%
2574
September1st to 10thDay
11%5%344245%5%8%50%
2165
11th to 20thDay
18%7%26%5%3446%6%39%
2085
21st to endDay
23%7%35%5%345%5%7%33%
1944
October1st to 10thDay
23%8%36%5%3346%7%32%
1800
11th to 20thDay
30%9%46%5%35%5%5%6%22%
1800
21st to endDay
30%10%36%6%335%46%23%
1798
November1st to 10thDay
35%11%5%8%5%35%44417%
1488
11th to 20thDay
34%12%46%6%35%44417%
1520
21st to endDay
35%11%49%5%45%33416%
1520
December1st to 10thDay
29%11%5%7%6%44446%20%
1354
11th to 20thDay
41%12%5%10%5%3432311%
1685
21st to endDay
36%14%48%7%4444412%
2442
January1st to 10thNight
37%12%37%6%34435%16%
2836
11th to 20thNight
34%12%46%6%45%445%16%
2760
21st to endNight
31%13%5%8%6%45%5%4416%
2845
February1st to 10thNight
33%13%47%5%3343421%
2340
11th to 20thNight
26%12%36%5%24445%28%
2272
21st to endNight
28%12%46%6%33446%24%
1924
March1st to 10thNight
28%10%46%5%45%5%5%5%23%
2083
11th to 20thNight
27%12%49%6%34445%23%
1979
21st to endNight
26%10%5%7%7%45%45%6%22%
2171
April1st to 10thNight
25%11%48%6%35%45%7%24%
1800
11th to 20thNight
21%11%36%6%46%5%6%6%26%
1603
21st to endNight
23%8%35%6%35%46%6%30%
1613
May1st to 10thNight
18%7%37%5%34447%38%
1440
11th to 20thNight
17%7%37%6%46%6%6%7%31%
1416
21st to endNight
16%6%48%6%45%5%6%7%34%
1371
June1st to 10thNight
18%10%48%5%46%5%5%5%30%
1260
11th to 20thNight
18%8%5%6%6%5%45%47%32%
1260
21st to endNight
17%6%25%4345%5%8%41%
1260
July1st to 10thNight
11%6%244345%47%49%
1260
11th to 20thNight
8%5%245%3446%8%52%
1260
21st to endNight
8%2244335%4461%
1407
August1st to 10thNight
8%5%335%3345%6%56%
1503
11th to 20thNight
6%32443445%6%58%
1602
21st to endNight
12%5%35%6%345%5%6%46%
1782
September1st to 10thNight
9%5%2443435%6%55%
1794
11th to 20thNight
18%8%25%6%245%45%41%
1872
21st to endNight
21%7%35%42335%6%40%
2016
October1st to 10thNight
24%7%25%5%2345%5%39%
2160
11th to 20thNight
29%7%35%43445%6%29%
2160
21st to endNight
31%8%35%5%34445%27%
2556
November1st to 10thNight
36%9%47%6%44345%17%
2590
11th to 20thNight
32%10%48%6%4444420%
2660
21st to endNight
34%10%48%6%34435%19%
2660
December1st to 10thNight
29%12%47%6%4434423%
2821
11th to 20thNight
43%15%5%6%5%2443311%
3520
21st to endNight
37%14%48%5%3343315%
5214

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
50%40%5%32
1329
11th to 20thDay
44%44%7%41
1288
21st to endDay
51%39%45%1
1507
February1st to 10thDay
46%40%7%5%1
1620
11th to 20thDay
39%40%9%9%31
1584
21st to endDay
45%38%7%6%31
1332
March1st to 10thDay
43%38%8%8%2
1875
11th to 20thDay
45%38%8%7%21
1980
21st to endDay
42%39%9%8%2
2185
April1st to 10thDay
41%39%10%7%3
2160
11th to 20thDay
35%38%8%11%7%1
2303
21st to endDay
37%38%10%9%5%
2345
May1st to 10thDay
35%38%11%14%2
2520
11th to 20thDay
32%38%12%14%31
2480
21st to endDay
36%40%13%9%3
2903
June1st to 10thDay
36%39%11%9%32
2700
11th to 20thDay
35%40%15%9%2
2700
21st to endDay
28%39%14%12%5%1
2700
July1st to 10thDay
22%39%15%16%6%1
2626
11th to 20thDay
20%39%16%21%4
2619
21st to endDay
15%40%13%21%9%3
2746
August1st to 10thDay
20%39%16%19%6%1
2416
11th to 20thDay
19%38%15%16%9%3
2298
21st to endDay
23%40%17%15%41
2574
September1st to 10thDay
20%39%14%16%9%2
2165
11th to 20thDay
28%40%13%10%8%1
2085
21st to endDay
34%40%11%11%5%
1944
October1st to 10thDay
31%41%11%10%5%
1800
11th to 20thDay
42%40%11%6%2
1800
21st to endDay
41%40%8%7%4
1798
November1st to 10thDay
46%41%5%43
1488
11th to 20thDay
45%43%7%31
1520
21st to endDay
45%42%5%6%1
1520
December1st to 10thDay
42%43%7%5%21
1354
11th to 20thDay
55%36%5%22
1688
21st to endDay
60%29%6%32
2442
January1st to 10thNight
50%41%5%41
2836
11th to 20thNight
43%42%8%421
2760
21st to endNight
47%40%5%7%2
2845
February1st to 10thNight
47%38%7%7%1
2340
11th to 20thNight
37%39%10%9%4
2274
21st to endNight
46%36%7%9%3
1924
March1st to 10thNight
42%39%9%8%2
2083
11th to 20thNight
46%37%9%5%3
1980
21st to endNight
43%39%8%8%2
2171
April1st to 10thNight
42%38%11%9%1
1800
11th to 20thNight
36%39%8%11%6%
1603
21st to endNight
36%38%12%11%4
1613
May1st to 10thNight
35%38%10%13%3
1440
11th to 20thNight
32%39%12%13%31
1416
21st to endNight
38%39%13%8%2
1371
June1st to 10thNight
38%38%12%7%41
1260
11th to 20thNight
39%39%13%8%1
1260
21st to endNight
29%39%14%12%42
1260
July1st to 10thNight
24%40%14%15%7%1
1225
11th to 20thNight
20%38%17%21%4
1218
21st to endNight
16%37%12%22%10%3
1329
August1st to 10thNight
23%38%13%19%7%
1495
11th to 20thNight
17%37%19%13%11%2
1602
21st to endNight
25%39%15%18%2
1782
September1st to 10thNight
17%38%12%23%9%2
1794
11th to 20thNight
27%38%10%11%11%2
1872
21st to endNight
33%38%12%11%5%1
2016
October1st to 10thNight
31%37%13%12%6%
2160
11th to 20thNight
37%38%13%11%1
2160
21st to endNight
39%38%10%9%3
2556
November1st to 10thNight
45%42%6%5%21
2590
11th to 20thNight
45%42%7%5%1
2660
21st to endNight
45%42%6%5%1
2660
December1st to 10thNight
43%41%8%431
2821
11th to 20thNight
56%34%5%32
3516
21st to endNight
60%27%7%5%1
5214

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
40%12%21%14%8%5%
180
11th to 20thDay
43%10%20%14%12%
168
21st to endDay
38%12%19%19%9%3
242
February1st to 10thDay
44%12%24%15%5%
340
11th to 20thDay
32%12%31%18%7%
335
21st to endDay
32%11%29%18%9%1
280
March1st to 10thDay
33%12%21%21%10%3
400
11th to 20thDay
34%15%19%19%12%2
420
21st to endDay
34%15%24%18%7%2
462
April1st to 10thDay
32%17%26%16%8%1
420
11th to 20thDay
27%17%24%17%12%2
412
21st to endDay
26%15%30%17%10%2
420
May1st to 10thDay
19%13%24%32%10%1
423
11th to 20thDay
21%5%24%31%16%2
448
21st to endDay
18%10%29%29%13%2
665
June1st to 10thDay
24%15%25%24%11%1
630
11th to 20thDay
18%14%32%23%11%1
630
21st to endDay
17%9%25%32%15%2
630
July1st to 10thDay
16%8%24%32%19%2
621
11th to 20thDay
11%9%25%33%19%2
618
21st to endDay
7%7%19%36%28%4
654
August1st to 10thDay
11%5%20%31%26%8%
447
11th to 20thDay
8%421%36%25%4
437
21st to endDay
16%10%18%35%19%3
495
September1st to 10thDay
15%9%27%29%15%4
450
11th to 20thDay
26%10%18%24%20%3
450
21st to endDay
25%14%18%25%16%2
450
October1st to 10thDay
31%8%20%20%18%3
450
11th to 20thDay
36%11%18%15%15%5%
450
21st to endDay
36%13%22%16%9%4
371
November1st to 10thDay
38%11%27%13%11%
180
11th to 20thDay
39%13%17%11%14%6%
180
21st to endDay
47%11%14%12%11%5%
180
December1st to 10thDay
36%12%20%12%14%6%
180
11th to 20thDay
46%9%17%17%10%1
180
21st to endDay
41%12%19%22%5%2
198
January1st to 10thNight
47%10%17%14%9%2
850
11th to 20thNight
43%7%15%20%14%
820
21st to endNight
38%7%20%21%12%2
854
February1st to 10thNight
41%10%18%23%7%
720
11th to 20thNight
32%10%19%28%10%1
704
21st to endNight
36%12%18%24%9%3
592
March1st to 10thNight
33%11%22%19%13%2
720
11th to 20thNight
37%12%18%19%13%1
720
21st to endNight
35%9%19%20%15%2
792
April1st to 10thNight
32%7%20%25%13%2
720
11th to 20thNight
28%9%23%26%12%2
535
21st to endNight
28%8%22%27%13%2
533
May1st to 10thNight
19%7%24%31%17%2
360
11th to 20thNight
21%5%16%34%21%3
354
21st to endNight
19%6%21%33%20%1
389
June1st to 10thNight
24%7%18%36%13%2
360
11th to 20thNight
22%6%24%32%16%1
360
21st to endNight
19%419%33%23%2
360
July1st to 10thNight
13%7%16%32%28%4
350
11th to 20thNight
11%5%21%35%26%3
348
21st to endNight
8%315%38%29%6%
394
August1st to 10thNight
9%5%11%31%35%9%
429
11th to 20thNight
9%113%36%35%5%
534
21st to endNight
16%5%17%31%27%4
594
September1st to 10thNight
13%417%34%25%7%
714
11th to 20thNight
22%7%13%20%29%9%
720
21st to endNight
28%7%18%22%21%5%
720
October1st to 10thNight
29%7%14%23%23%3
720
11th to 20thNight
36%5%17%21%17%4
720
21st to endNight
39%9%18%19%11%3
792
November1st to 10thNight
43%9%19%20%8%
740
11th to 20thNight
41%9%23%16%10%1
760
21st to endNight
40%9%20%19%11%2
760
December1st to 10thNight
36%8%21%21%12%3
836
11th to 20thNight
48%10%16%17%8%1
850
21st to endNight
46%9%23%18%4
935
Page generated at 2024-01-11 19:33:49. Version ac07

Copyright 2024 Attilla Danko


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