Squamish
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Squamish clear sky chart from 2005-11-06 to 2024-02-25.

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
28%
22742
9%
80992
6%
22604
32%
22604
10%
63383

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
15%
847
8%
4696
5%
816
19%
816
3%
4011
January11th to 20thNight
17%
845
14%
4619
4%
820
21%
820
5%
3246
January21st to endNight
17%
863
5%
4944
5%
838
23%
838
4%
4399
February1st to 10thNight
14%
760
8%
2470
4%
760
21%
760
8%
2055
February11th to 20thNight
18%
742
9%
2404
4%
740
24%
740
9%
1931
February21st to endNight
20%
610
9%
1977
5%
610
26%
610
9%
1587
March1st to 10thNight
21%
720
8%
2098
4%
720
25%
720
9%
1743
March11th to 20thNight
20%
720
7%
1980
4%
720
22%
720
8%
1707
March21st to endNight
20%
792
5%
2125
2%
792
22%
792
8%
1846
April1st to 10thNight
25%
720
5%
1800
3%
720
26%
720
9%
1547
April11th to 20thNight
27%
602
8%
1670
4%
602
30%
602
12%
1359
April21st to endNight
24%
482
6%
1562
4%
482
27%
482
11%
1249
May1st to 10thNight
41%
360
8%
1440
10%
360
44%
360
13%
1032
May11th to 20thNight
44%
354
8%
1416
13%
354
46%
354
12%
1030
May21st to endNight
38%
389
6%
1456
6%
388
41%
388
14%
1070
June1st to 10thNight
31%
360
2%
1260
1%
360
32%
360
12%
980
June11th to 20thNight
32%
360
1%
1260
0%
360
33%
360
9%
1012
June21st to endNight
44%
360
4%
1260
1%
360
45%
360
15%
897
July1st to 10thNight
57%
350
5%
1225
4%
350
57%
350
24%
754
July11th to 20thNight
63%
348
12%
1218
12%
348
65%
348
27%
713
July21st to endNight
71%
394
15%
1404
23%
372
74%
372
35%
697
August1st to 10thNight
69%
366
15%
1432
21%
364
72%
364
31%
742
August11th to 20thNight
71%
534
19%
1602
19%
534
73%
534
36%
914
August21st to endNight
54%
637
16%
1825
13%
637
55%
637
25%
1232
September1st to 10thNight
50%
720
16%
1800
8%
720
53%
720
31%
1204
September11th to 20thNight
46%
720
17%
1805
9%
720
49%
720
25%
1295
September21st to endNight
38%
720
14%
2060
9%
720
41%
720
18%
1510
October1st to 10thNight
36%
720
10%
2160
8%
720
38%
720
16%
1593
October11th to 20thNight
29%
720
10%
2160
9%
720
32%
720
13%
1701
October21st to endNight
20%
792
9%
2544
5%
792
25%
792
9%
2038
November1st to 10thNight
14%
740
6%
2590
4%
740
18%
740
6%
2204
November11th to 20thNight
15%
760
7%
2660
4%
760
19%
760
7%
2213
November21st to endNight
16%
760
7%
2660
2%
760
22%
760
7%
2173
December1st to 10thNight
18%
791
10%
2726
5%
791
24%
791
9%
2142
December11th to 20thNight
8%
850
3%
3515
1%
849
12%
849
4%
3097
December21st to endNight
9%
934
5%
5169
2%
905
16%
905
3%
4460

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
27%14%46%5%34345%27%
77938
Night
29%16%35%423345%25%
81317
TransparencyDay
62%6%10%14%7%2
77646
Night
63%6%10%12%7%2
81189
SeeingDay
30%15%26%20%7%1
14387
Night
35%8%23%23%11%1
22753

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
34%26%3432222416%
2219
11th to 20thDay
26%15%5%8%5%32325%27%
2199
21st to endDay
49%20%3431222212%
2708
February1st to 10thDay
29%20%5%7%424435%18%
1710
11th to 20thDay
24%23%46%42333424%
1665
21st to endDay
18%25%6%8%5%4344419%
1373
March1st to 10thDay
29%19%5%8%5%2333420%
1862
11th to 20thDay
31%25%46%5%2323316%
1980
21st to endDay
29%23%5%7%5%2433316%
2231
April1st to 10thDay
28%21%5%7%6%34345%14%
2160
11th to 20thDay
28%20%47%6%3333417%
2237
21st to endDay
27%19%5%6%5%35%44417%
2398
May1st to 10thDay
23%13%5%7%6%345%5%5%24%
2520
11th to 20thDay
21%12%46%6%45%5%6%8%24%
2477
21st to endDay
28%9%46%5%45%446%25%
2817
June1st to 10thDay
33%10%37%5%3445%6%20%
2700
11th to 20thDay
33%12%48%6%34446%17%
2700
21st to endDay
24%8%37%5%34446%32%
2700
July1st to 10thDay
17%7%26%434446%43%
2700
11th to 20thDay
16%5%244345%5%7%46%
2700
21st to endDay
12%42442435%5%54%
2829
August1st to 10thDay
15%5%24323446%51%
2498
11th to 20thDay
11%5%24434446%53%
2298
21st to endDay
18%6%25%5%35%46%8%39%
2530
September1st to 10thDay
17%6%35%5%33445%44%
2160
11th to 20thDay
24%8%35%5%33335%39%
2152
21st to endDay
28%8%35%5%23335%34%
1900
October1st to 10thDay
28%9%35%5%2334435%
1800
11th to 20thDay
37%8%35%424445%25%
1800
21st to endDay
39%10%35%422335%24%
1810
November1st to 10thDay
41%12%45%5%2433318%
1488
11th to 20thDay
39%19%35%41222420%
1520
21st to endDay
38%16%3443332320%
1520
December1st to 10thDay
30%18%46%32222327%
1450
11th to 20thDay
38%19%46%42323316%
1685
21st to endDay
35%22%47%5%3422312%
2442
January1st to 10thNight
34%25%37%42222315%
4726
11th to 20thNight
29%13%45%323448%24%
4699
21st to endNight
46%22%35%32222312%
4944
February1st to 10thNight
29%19%5%6%433346%17%
2470
11th to 20thNight
23%23%5%6%42334423%
2402
21st to endNight
22%24%47%5%2434422%
1977
March1st to 10thNight
28%22%45%42344420%
2098
11th to 20thNight
31%24%35%43433417%
1979
21st to endNight
31%20%46%5%2334418%
2125
April1st to 10thNight
26%21%46%5%4445%319%
1800
11th to 20thNight
25%17%46%434436%24%
1670
21st to endNight
27%15%37%5%33346%24%
1562
May1st to 10thNight
19%11%35%5%36%5%47%33%
1440
11th to 20thNight
20%10%37%5%45%6%6%9%26%
1416
21st to endNight
22%11%36%5%26%446%31%
1456
June1st to 10thNight
28%9%36%7%2445%6%26%
1260
11th to 20thNight
27%13%37%6%2445%6%22%
1260
21st to endNight
20%8%35%5%35%45%6%36%
1260
July1st to 10thNight
14%6%33434446%48%
1260
11th to 20thNight
13%5%2342335%8%52%
1260
21st to endNight
11%323224345%61%
1487
August1st to 10thNight
12%5%23223345%59%
1440
11th to 20thNight
9%41333445%6%58%
1602
21st to endNight
15%7%245%445%5%8%41%
1825
September1st to 10thNight
14%6%2442345%7%49%
1800
11th to 20thNight
24%7%24433435%40%
1805
21st to endNight
27%10%35%422346%34%
2060
October1st to 10thNight
26%11%2443444335%
2160
11th to 20thNight
35%10%245%2334427%
2160
21st to endNight
36%12%35%32443423%
2544
November1st to 10thNight
42%15%35%5%2333415%
2590
11th to 20thNight
38%18%3441332320%
2660
21st to endNight
36%16%45%43322321%
2660
December1st to 10thNight
29%15%46%5%2434425%
2726
11th to 20thNight
38%21%5%6%42233313%
3520
21st to endNight
38%23%46%42322314%
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
73%8%6%9%31
2219
11th to 20thDay
63%39%12%7%6%
2220
21st to endDay
82%347%31
2708
February1st to 10thDay
70%5%8%8%7%2
1710
11th to 20thDay
66%5%7%12%7%2
1674
21st to endDay
71%6%8%9%42
1373
March1st to 10thDay
71%6%8%10%5%1
1862
11th to 20thDay
77%36%9%41
1980
21st to endDay
76%48%9%2
2231
April1st to 10thDay
75%6%10%7%1
2160
11th to 20thDay
74%47%8%7%
2237
21st to endDay
75%6%6%8%5%
2398
May1st to 10thDay
65%7%11%12%5%1
2520
11th to 20thDay
61%9%11%14%41
2480
21st to endDay
64%7%11%14%4
2818
June1st to 10thDay
68%8%10%8%42
2700
11th to 20thDay
73%6%11%7%2
2700
21st to endDay
57%5%13%17%7%2
2700
July1st to 10thDay
47%7%13%20%11%2
2626
11th to 20thDay
40%8%17%25%10%
2619
21st to endDay
32%7%14%27%17%4
2672
August1st to 10thDay
35%8%15%25%14%2
2481
11th to 20thDay
32%8%17%24%16%3
2298
21st to endDay
44%9%16%23%7%2
2530
September1st to 10thDay
43%8%11%25%10%4
2160
11th to 20thDay
51%49%17%17%3
2152
21st to endDay
55%6%11%16%10%2
1900
October1st to 10thDay
54%6%12%16%12%
1800
11th to 20thDay
64%5%9%15%6%1
1800
21st to endDay
67%49%12%7%1
1810
November1st to 10thDay
72%7%6%8%6%1
1488
11th to 20thDay
73%47%7%7%3
1520
21st to endDay
71%5%5%10%8%2
1520
December1st to 10thDay
65%5%8%11%10%2
1450
11th to 20thDay
76%46%8%32
1688
21st to endDay
78%6%48%31
2442
January1st to 10thNight
77%448%5%1
4726
11th to 20thNight
59%6%10%13%8%4
4740
21st to endNight
80%446%41
4944
February1st to 10thNight
70%5%7%8%7%2
2470
11th to 20thNight
66%5%9%10%7%3
2404
21st to endNight
67%49%11%7%2
1977
March1st to 10thNight
69%5%8%12%5%1
2098
11th to 20thNight
74%5%8%8%5%1
1980
21st to endNight
72%7%11%8%2
2125
April1st to 10thNight
70%7%10%11%1
1800
11th to 20thNight
64%7%9%12%7%1
1670
21st to endNight
64%6%12%11%6%
1562
May1st to 10thNight
52%10%17%17%41
1440
11th to 20thNight
55%9%17%14%4
1416
21st to endNight
55%8%15%17%4
1456
June1st to 10thNight
62%6%17%8%33
1260
11th to 20thNight
65%7%14%10%4
1260
21st to endNight
51%9%14%17%6%3
1260
July1st to 10thNight
39%7%18%20%14%2
1225
11th to 20thNight
34%8%20%26%11%
1218
21st to endNight
25%6%15%31%17%5%
1404
August1st to 10thNight
29%6%18%26%17%3
1432
11th to 20thNight
28%9%21%23%15%5%
1602
21st to endNight
42%8%17%23%7%2
1825
September1st to 10thNight
36%9%16%24%13%3
1800
11th to 20thNight
47%6%11%16%15%5%
1805
21st to endNight
54%5%13%17%8%3
2060
October1st to 10thNight
54%7%11%16%11%1
2160
11th to 20thNight
63%6%9%15%8%
2160
21st to endNight
67%5%7%12%8%1
2544
November1st to 10thNight
75%47%8%5%2
2590
11th to 20thNight
72%5%7%7%6%3
2660
21st to endNight
70%46%8%9%2
2660
December1st to 10thNight
64%6%9%11%9%2
2726
11th to 20thNight
78%6%5%5%42
3516
21st to endNight
79%338%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
46%12%19%14%6%2
180
11th to 20thDay
42%10%22%19%7%
180
21st to endDay
48%8%21%16%7%
210
February1st to 10thDay
39%17%27%12%4
370
11th to 20thDay
36%14%29%17%31
365
21st to endDay
29%22%27%17%4
295
March1st to 10thDay
35%18%26%17%4
420
11th to 20thDay
40%16%19%18%8%1
420
21st to endDay
41%16%24%12%6%1
462
April1st to 10thDay
41%17%21%15%5%1
420
11th to 20thDay
37%19%22%15%7%1
412
21st to endDay
33%22%21%16%7%
420
May1st to 10thDay
23%20%27%24%5%
423
11th to 20thDay
26%12%27%24%10%1
448
21st to endDay
28%13%29%21%7%2
579
June1st to 10thDay
33%18%26%18%5%1
630
11th to 20thDay
31%21%27%17%41
630
21st to endDay
22%16%29%26%6%2
630
July1st to 10thDay
19%13%31%27%7%2
621
11th to 20thDay
15%16%33%27%7%2
618
21st to endDay
10%10%31%33%12%3
575
August1st to 10thDay
14%11%26%31%13%5%
447
11th to 20thDay
11%8%29%34%14%3
437
21st to endDay
17%15%32%24%10%2
495
September1st to 10thDay
20%18%33%22%6%1
450
11th to 20thDay
29%14%26%22%8%2
450
21st to endDay
30%14%26%20%8%2
450
October1st to 10thDay
32%13%25%18%10%2
450
11th to 20thDay
40%11%20%17%9%2
450
21st to endDay
44%13%22%13%7%1
352
November1st to 10thDay
39%16%23%17%6%
180
11th to 20thDay
46%11%14%14%12%2
180
21st to endDay
46%16%17%8%10%3
180
December1st to 10thDay
45%8%18%16%11%2
180
11th to 20thDay
46%10%21%16%7%1
180
21st to endDay
40%9%33%14%4
198
January1st to 10thNight
49%11%21%15%41
850
11th to 20thNight
42%10%24%20%4
850
21st to endNight
43%10%25%18%4
863
February1st to 10thNight
38%10%31%17%3
760
11th to 20thNight
34%11%31%21%3
744
21st to endNight
34%12%25%21%7%
610
March1st to 10thNight
38%11%23%18%9%1
720
11th to 20thNight
43%11%21%19%6%
720
21st to endNight
41%9%23%17%10%1
792
April1st to 10thNight
38%8%21%25%8%1
720
11th to 20thNight
33%6%26%26%7%1
602
21st to endNight
34%7%28%22%9%
482
May1st to 10thNight
23%6%23%31%16%1
360
11th to 20thNight
25%5%19%33%17%1
354
21st to endNight
25%426%31%14%
389
June1st to 10thNight
29%6%25%25%14%1
360
11th to 20thNight
29%9%24%26%11%1
360
21st to endNight
23%6%21%30%20%1
360
July1st to 10thNight
15%319%35%28%1
350
11th to 20thNight
14%414%38%29%1
348
21st to endNight
11%211%36%36%4
394
August1st to 10thNight
14%210%32%37%5%
366
11th to 20thNight
11%110%40%35%2
534
21st to endNight
19%319%33%24%1
637
September1st to 10thNight
18%423%36%19%1
720
11th to 20thNight
27%417%26%23%3
720
21st to endNight
33%6%18%28%14%1
720
October1st to 10thNight
31%6%20%27%15%1
720
11th to 20thNight
40%5%21%22%11%1
720
21st to endNight
44%8%26%17%41
792
November1st to 10thNight
50%11%21%16%1
740
11th to 20thNight
48%9%25%15%4
760
21st to endNight
43%13%22%17%5%1
760
December1st to 10thNight
37%10%30%18%6%
791
11th to 20thNight
49%9%29%12%2
850
21st to endNight
47%11%28%13%1
935
Page generated at 2024-02-22 03:05:45. Version ac07

Copyright 2024 Attilla Danko


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