Powell River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Powell River clear sky chart from 2005-11-05 to 2017-09-24.

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
35%
14503
8%
46828
6%
14474
37%
14474
13%
35923

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 15thNight
26%
750
8%
2686
7%
746
29%
746
7%
2234
January16th to endNight
28%
794
5%
2799
4%
794
30%
794
7%
2346
February1st to 15thNight
27%
700
6%
2288
4%
700
30%
700
8%
1917
February16th to endNight
31%
632
11%
2053
9%
632
35%
632
12%
1572
March1st to 15thNight
21%
720
3%
2050
2%
720
22%
720
7%
1765
March16th to endNight
25%
768
6%
2106
3%
768
27%
768
8%
1793
April1st to 15thNight
35%
659
7%
1739
3%
659
37%
659
13%
1420
April16th to endNight
29%
534
8%
1614
6%
534
32%
534
12%
1261
May1st to 15thNight
40%
359
10%
1440
12%
359
46%
359
13%
1003
May16th to endNight
42%
375
5%
1371
5%
374
44%
374
13%
1008
June1st to 15thNight
41%
360
2%
1260
1%
360
41%
360
15%
893
June16th to endNight
43%
360
3%
1260
1%
360
44%
360
16%
902
July1st to 15thNight
58%
340
6%
1190
3%
340
60%
340
29%
666
July16th to endNight
64%
376
11%
1256
13%
354
68%
354
34%
664
August1st to 15thNight
70%
466
14%
1540
15%
464
72%
464
33%
854
August16th to endNight
61%
573
16%
1719
13%
573
64%
573
31%
1059
September1st to 15thNight
65%
714
21%
1794
11%
714
68%
714
40%
1100
September16th to endNight
42%
692
13%
1925
8%
692
44%
692
21%
1363
October1st to 15thNight
42%
660
8%
1980
8%
660
44%
660
19%
1422
October16th to endNight
28%
704
4%
2223
4%
704
30%
704
9%
1824
November1st to 15thNight
15%
700
4%
2450
2%
700
19%
700
5%
2110
November16th to endNight
20%
720
5%
2520
3%
720
23%
720
7%
2081
December1st to 15thNight
23%
747
5%
2685
3%
747
26%
747
7%
2226
December16th to endNight
19%
800
5%
2880
2%
800
22%
800
7%
2440

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
22%8%35%5%2445%6%31%
48134
Night
26%8%36%5%24345%28%
46974
Cloud CoverDay
26%8%35%424345%29%
48134
Night
30%8%35%423345%27%
46977
TransparencyDay
54%8%15%15%5%
47784
Night
58%7%13%14%5%
46828
SeeingDay
24%9%23%25%14%2
6377
Night
31%6%18%24%16%3
14508

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 15thDay
37%11%36%6%35%23415%
1253
16th to endDay
33%12%39%6%35%445%11%
1420
February1st to 15thDay
35%11%345%34435%17%
1576
16th to endDay
24%9%46%6%35%6%46%21%
1421
March1st to 15thDay
35%12%46%43445%413%
1908
16th to endDay
27%12%48%6%44345%19%
2117
April1st to 15thDay
22%10%47%6%35%5%5%6%21%
2206
16th to endDay
25%8%36%5%2445%6%26%
2346
May1st to 15thDay
17%7%35%5%2445%7%35%
2511
16th to endDay
19%8%46%5%35%45%6%30%
2739
June1st to 15thDay
16%6%36%5%35%46%8%34%
2700
16th to endDay
16%6%36%6%345%6%8%31%
2700
July1st to 15thDay
11%41332345%7%53%
2700
16th to endDay
8%323313447%56%
2828
August1st to 15thDay
7%314323447%57%
2410
16th to endDay
11%42432445%8%47%
2483
September1st to 15thDay
10%414424449%50%
2165
16th to endDay
25%6%244245%5%6%30%
1892
October1st to 15thDay
26%8%36%5%2445%6%26%
1650
16th to endDay
34%9%36%42445%6%17%
1645
November1st to 15thDay
39%10%45%42443216%
1408
16th to endDay
33%11%37%6%2444316%
1440
December1st to 15thDay
32%10%5%7%434345%19%
1272
16th to endDay
36%13%37%5%3433414%
1344
January1st to 15thNight
36%10%36%5%2423419%
2686
16th to endNight
33%10%47%5%34445%15%
2799
February1st to 15thNight
33%12%36%5%23335%19%
2276
16th to endNight
25%11%35%5%34345%27%
2053
March1st to 15thNight
33%10%46%6%25%44417%
2050
16th to endNight
28%10%5%7%6%34445%18%
2102
April1st to 15thNight
23%8%47%5%35%5%5%6%23%
1739
16th to endNight
24%7%37%5%445%6%5%25%
1614
May1st to 15thNight
19%7%36%5%25%5%5%5%34%
1439
16th to endNight
16%6%38%6%35%6%6%7%28%
1371
June1st to 15thNight
18%9%46%5%3435%7%33%
1260
16th to endNight
17%8%46%5%345%48%32%
1260
July1st to 15thNight
9%42442436%7%51%
1260
16th to endNight
9%324322445%56%
1341
August1st to 15thNight
6%31442345%6%54%
1548
16th to endNight
9%42442435%7%49%
1719
September1st to 15thNight
8%413423445%57%
1794
16th to endNight
22%6%25%5%23336%37%
1925
October1st to 15thNight
25%7%2432335%5%36%
1980
16th to endNight
36%8%25%334445%21%
2223
November1st to 15thNight
39%8%37%43434416%
2450
16th to endNight
33%10%5%8%5%3333419%
2520
December1st to 15thNight
32%11%47%6%2433320%
2685
16th to endNight
37%12%45%42333417%
2880

Percentage Cloud Cover SW (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 15thDay
41%11%35%42232418%
1253
16th to endDay
37%12%35%5%24346%14%
1420
February1st to 15thDay
37%10%35%42434417%
1576
16th to endDay
29%11%45%5%35%45%421%
1421
March1st to 15thDay
41%12%35%43424413%
1908
16th to endDay
33%14%5%7%5%2423415%
2117
April1st to 15thDay
27%12%48%5%35%446%17%
2206
16th to endDay
30%10%36%5%4335%6%19%
2346
May1st to 15thDay
21%9%25%33436%7%32%
2511
16th to endDay
25%8%35%5%3445%6%26%
2739
June1st to 15thDay
21%7%36%5%2446%7%28%
2700
16th to endDay
22%8%37%5%345%5%6%27%
2700
July1st to 15thDay
14%41342335%6%50%
2700
16th to endDay
12%31331345%7%52%
2828
August1st to 15thDay
9%31332345%7%55%
2410
16th to endDay
14%5%2432326%7%46%
2483
September1st to 15thDay
12%5%1432335%5%50%
2165
16th to endDay
29%5%25%424445%31%
1892
October1st to 15thDay
29%8%37%42344427%
1650
16th to endDay
40%7%2432325%5%20%
1645
November1st to 15thDay
45%8%25%42443215%
1408
16th to endDay
39%10%46%5%2223418%
1440
December1st to 15thDay
36%11%45%32333322%
1272
16th to endDay
42%12%36%42233315%
1344
January1st to 15thNight
41%10%35%42332319%
2685
16th to endNight
38%10%35%42335%5%15%
2799
February1st to 15thNight
38%11%36%42324418%
2276
16th to endNight
30%12%3442333426%
2053
March1st to 15thNight
39%11%36%5%2433316%
2050
16th to endNight
35%11%36%43445%417%
2106
April1st to 15thNight
26%10%35%6%3445%6%22%
1739
16th to endNight
29%8%36%5%2446%424%
1614
May1st to 15thNight
22%7%26%5%25%45%5%32%
1439
16th to endNight
20%8%47%6%345%5%6%28%
1371
June1st to 15thNight
22%7%47%41345%6%32%
1260
16th to endNight
21%6%37%42445%9%30%
1260
July1st to 15thNight
12%31322345%6%53%
1260
16th to endNight
11%223313335%57%
1341
August1st to 15thNight
8%224324446%56%
1548
16th to endNight
13%424324347%49%
1719
September1st to 15thNight
9%313413345%57%
1794
16th to endNight
25%5%25%413347%36%
1925
October1st to 15thNight
29%6%24413345%34%
1980
16th to endNight
42%7%34423336%19%
2223
November1st to 15thNight
46%7%35%42334315%
2450
16th to endNight
38%11%46%42233419%
2520
December1st to 15thNight
37%11%36%42323321%
2685
16th to endNight
42%13%3431323416%
2880

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 15thDay
72%5%7%8%4
1253
16th to endDay
72%9%8%7%1
1420
February1st to 15thDay
70%7%8%6%33
1576
16th to endDay
63%7%13%10%4
1421
March1st to 15thDay
74%6%10%7%1
1908
16th to endDay
69%8%10%10%
2117
April1st to 15thDay
64%9%12%10%2
2206
16th to endDay
61%7%13%11%4
2346
May1st to 15thDay
49%7%17%18%5%
2511
16th to endDay
55%9%16%15%2
2743
June1st to 15thDay
50%9%19%16%31
2700
16th to endDay
52%8%19%14%3
2700
July1st to 15thDay
33%7%22%24%10%1
2541
16th to endDay
27%9%21%29%10%1
2650
August1st to 15thDay
27%8%22%28%10%2
2393
16th to endDay
35%7%23%25%6%1
2483
September1st to 15thDay
33%8%18%23%14%1
2165
16th to endDay
53%8%16%14%6%
1892
October1st to 15thDay
59%10%12%11%6%
1650
16th to endDay
66%8%14%7%2
1645
November1st to 15thDay
73%7%9%5%21
1408
16th to endDay
71%7%7%9%3
1440
December1st to 15thDay
68%8%8%8%5%2
1272
16th to endDay
75%5%6%6%41
1344
January1st to 15thNight
70%5%8%8%5%
2686
16th to endNight
70%7%10%9%2
2799
February1st to 15thNight
69%6%9%9%22
2288
16th to endNight
60%5%12%14%5%
2053
March1st to 15thNight
71%6%10%8%2
2050
16th to endNight
67%9%10%11%1
2106
April1st to 15thNight
61%9%12%14%2
1739
16th to endNight
60%7%12%15%4
1614
May1st to 15thNight
52%7%12%20%6%
1440
16th to endNight
54%9%18%14%3
1371
June1st to 15thNight
52%7%21%13%5%1
1260
16th to endNight
50%8%15%19%31
1260
July1st to 15thNight
32%6%22%23%12%2
1190
16th to endNight
27%6%22%30%10%1
1256
August1st to 15thNight
27%9%20%27%12%2
1540
16th to endNight
33%8%23%25%7%2
1719
September1st to 15thNight
28%7%15%27%18%2
1794
16th to endNight
48%7%19%17%7%1
1925
October1st to 15thNight
50%6%18%17%7%
1980
16th to endNight
66%7%14%8%2
2223
November1st to 15thNight
73%7%8%6%31
2450
16th to endNight
69%6%8%9%5%
2520
December1st to 15thNight
69%6%10%7%4
2685
16th to endNight
71%6%8%8%3
2880

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 15thDay
15%18%31%23%11%
60
16th to endDay
51%6%19%9%11%
106
February1st to 15thDay
41%7%20%22%8%
236
16th to endDay
32%10%24%19%11%
211
March1st to 15thDay
49%16%16%10%4
265
16th to endDay
37%17%23%14%6%1
288
April1st to 15thDay
31%14%25%18%7%1
269
16th to endDay
29%12%32%17%7%
270
May1st to 15thDay
23%9%25%30%10%
288
16th to endDay
21%7%23%29%15%2
455
June1st to 15thDay
20%13%24%27%12%
495
16th to endDay
19%8%30%27%13%1
495
July1st to 15thDay
12%6%26%34%19%1
475
16th to endDay
8%7%21%35%24%2
497
August1st to 15thDay
8%121%33%27%6%
315
16th to endDay
15%6%18%35%20%2
332
September1st to 15thDay
12%8%23%30%20%5%
315
16th to endDay
30%7%21%22%15%2
288
October1st to 15thDay
33%9%25%17%13%1
255
16th to endDay
39%9%18%18%11%2
218
November1st to 15thDay
56%6%25%8%3
60
16th to endDay
41%10%11%13%10%13%
60
December1st to 15thDay
46%10%18%10%11%3
60
16th to endDay
37%6%25%17%9%4
64
January1st to 15thNight
42%6%15%19%13%1
750
16th to endNight
39%5%17%19%15%2
794
February1st to 15thNight
39%8%16%25%10%
704
16th to endNight
33%9%16%27%10%2
632
March1st to 15thNight
40%10%20%16%10%1
720
16th to endNight
36%8%20%18%12%2
768
April1st to 15thNight
27%6%21%27%14%2
659
16th to endNight
29%7%24%26%10%2
534
May1st to 15thNight
22%7%19%29%17%3
360
16th to endNight
20%317%34%21%1
375
June1st to 15thNight
22%6%17%33%19%1
360
16th to endNight
20%222%34%18%2
360
July1st to 15thNight
9%6%18%32%28%5%
340
16th to endNight
9%215%37%28%5%
376
August1st to 15thNight
9%19%36%35%8%
466
16th to endNight
13%215%34%30%4
573
September1st to 15thNight
10%314%28%32%11%
714
16th to endNight
27%5%17%22%20%7%
692
October1st to 15thNight
30%5%15%24%20%3
660
16th to endNight
44%5%15%18%12%3
704
November1st to 15thNight
47%6%24%15%6%
700
16th to endNight
40%9%20%16%10%2
720
December1st to 15thNight
40%7%19%21%10%
747
16th to endNight
47%7%21%17%5%
800
Page generated at 2017-09-25 06:02:29. Version ac04

Copyright 2017 A. Danko


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