Esquimalt
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Esquimalt clear sky chart from 2005-11-06 to 2024-01-31.

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
43%
22692
10%
75042
9%
22644
46%
22644
17%
53758

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
24%
847
6%
2836
4%
846
27%
846
7%
2389
January11th to 20thNight
33%
846
6%
2843
5%
846
35%
846
9%
2324
January21st to endNight
34%
834
8%
2844
7%
834
37%
834
9%
2267
February1st to 10thNight
30%
720
7%
2340
4%
720
35%
720
10%
1881
February11th to 20thNight
35%
700
10%
2274
8%
700
38%
700
13%
1729
February21st to endNight
31%
592
11%
1916
7%
592
36%
592
13%
1477
March1st to 10thNight
40%
720
10%
2070
9%
720
42%
720
16%
1574
March11th to 20thNight
36%
720
10%
1979
7%
720
38%
720
16%
1528
March21st to endNight
35%
792
8%
2142
5%
792
37%
792
14%
1718
April1st to 10thNight
38%
720
8%
1800
3%
720
39%
720
19%
1382
April11th to 20thNight
40%
615
13%
1683
8%
615
42%
615
21%
1210
April21st to endNight
39%
526
10%
1606
6%
526
43%
526
18%
1134
May1st to 10thNight
50%
360
12%
1440
15%
360
54%
360
21%
864
May11th to 20thNight
55%
354
11%
1416
17%
354
59%
354
20%
870
May21st to endNight
50%
389
7%
1526
10%
388
53%
388
20%
962
June1st to 10thNight
49%
360
7%
1260
6%
360
51%
360
20%
822
June11th to 20thNight
46%
360
5%
1260
4%
360
48%
360
23%
800
June21st to endNight
58%
360
9%
1260
7%
360
61%
360
33%
694
July1st to 10thNight
66%
350
10%
1225
9%
350
68%
350
36%
648
July11th to 20thNight
64%
348
17%
1218
19%
348
69%
348
41%
593
July21st to endNight
74%
394
22%
1458
30%
372
82%
372
56%
542
August1st to 10thNight
74%
425
20%
1491
24%
423
76%
423
43%
697
August11th to 20thNight
82%
534
25%
1602
23%
534
84%
534
53%
770
August21st to endNight
68%
647
24%
1835
18%
647
70%
647
41%
1017
September1st to 10thNight
73%
720
22%
1800
13%
720
74%
720
49%
1021
September11th to 20thNight
63%
720
21%
1822
14%
720
64%
720
33%
1202
September21st to endNight
57%
720
17%
2051
13%
720
59%
720
28%
1339
October1st to 10thNight
58%
720
12%
2160
12%
720
59%
720
24%
1446
October11th to 20thNight
48%
720
12%
2160
12%
720
50%
720
19%
1545
October21st to endNight
41%
792
13%
2486
10%
792
46%
792
17%
1779
November1st to 10thNight
34%
740
7%
2590
7%
740
37%
740
10%
2058
November11th to 20thNight
31%
760
8%
2660
6%
760
36%
760
11%
2052
November21st to endNight
30%
760
7%
2660
4%
760
33%
760
9%
2133
December1st to 10thNight
35%
760
8%
2660
6%
760
38%
760
10%
2084
December11th to 20thNight
24%
840
2%
3497
1%
840
26%
840
5%
3019
December21st to endNight
19%
927
4%
5172
3%
905
24%
905
4%
4188

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
15%8%47%6%45%5%5%7%34%
74877
Night
17%9%47%6%35%5%5%6%34%
75257
TransparencyDay
46%9%18%19%7%1
74567
Night
50%9%16%17%7%1
75085
SeeingDay
16%5%17%27%26%9%
14290
Night
21%6%19%27%21%6%
22708

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
29%13%5%8%7%5%5%44416%
1329
11th to 20thDay
21%14%6%10%7%46%5%6%6%16%
1334
21st to endDay
24%15%6%9%8%5%6%45%5%12%
1735
February1st to 10thDay
24%14%49%7%45%6%5%7%15%
1620
11th to 20thDay
20%14%5%10%5%45%446%23%
1575
21st to endDay
18%12%49%8%5%6%6%5%6%20%
1340
March1st to 10thDay
17%10%6%9%7%47%6%6%8%20%
1885
11th to 20thDay
22%12%5%9%7%46%5%45%21%
1980
21st to endDay
18%13%410%7%5%7%6%6%5%18%
2214
April1st to 10thDay
17%10%5%7%8%5%7%6%7%8%19%
2160
11th to 20thDay
16%10%38%9%48%5%6%6%24%
2224
21st to endDay
16%8%47%8%46%5%6%8%27%
2353
May1st to 10thDay
11%7%37%7%5%7%6%6%9%32%
2520
11th to 20thDay
12%7%37%7%46%6%6%8%34%
2477
21st to endDay
14%8%48%6%36%5%6%6%35%
2745
June1st to 10thDay
14%7%47%5%346%7%8%34%
2700
11th to 20thDay
10%6%47%7%5%7%6%6%9%34%
2700
21st to endDay
9%5%246%46%6%7%7%45%
2700
July1st to 10thDay
7%4245%345%5%6%55%
2700
11th to 20thDay
5%3244245%5%8%58%
2700
21st to endDay
4212322447%70%
2772
August1st to 10thDay
6%324423446%61%
2436
11th to 20thDay
5%32442445%8%59%
2298
21st to endDay
7%325%435%5%6%10%50%
2520
September1st to 10thDay
8%5%25%5%25%45%8%52%
2160
11th to 20thDay
11%6%36%5%35%45%7%44%
2135
21st to endDay
15%6%36%6%3445%8%41%
1908
October1st to 10thDay
18%7%26%5%35%5%6%6%37%
1800
11th to 20thDay
20%10%49%7%46%5%47%24%
1800
21st to endDay
22%10%48%6%35%5%5%7%25%
1867
November1st to 10thDay
26%13%48%7%46%5%5%6%16%
1488
11th to 20thDay
24%11%5%9%7%36%445%22%
1520
21st to endDay
25%11%5%9%6%46%445%20%
1520
December1st to 10thDay
20%15%48%7%44446%24%
1520
11th to 20thDay
27%14%49%8%45%5%5%7%14%
1700
21st to endDay
23%18%6%11%8%45%445%12%
2442
January1st to 10thNight
28%11%48%7%46%5%5%5%17%
2836
11th to 20thNight
22%14%5%8%6%45%5%5%6%20%
2843
21st to endNight
24%11%48%6%45%5%5%6%22%
2844
February1st to 10thNight
23%11%48%7%45%45%6%22%
2340
11th to 20thNight
17%11%48%7%35%5%5%6%29%
2272
21st to endNight
19%12%48%7%46%5%5%6%25%
1916
March1st to 10thNight
18%9%37%7%36%5%6%8%28%
2070
11th to 20thNight
18%10%47%8%46%6%6%6%24%
1979
21st to endNight
19%11%5%9%7%45%5%5%6%24%
2142
April1st to 10thNight
19%8%47%7%45%5%6%7%29%
1800
11th to 20thNight
15%8%46%6%35%7%6%8%31%
1683
21st to endNight
17%8%37%6%445%5%7%34%
1606
May1st to 10thNight
10%6%36%6%35%5%47%45%
1440
11th to 20thNight
10%6%26%5%45%5%7%8%41%
1416
21st to endNight
12%6%26%6%35%5%6%8%41%
1526
June1st to 10thNight
13%7%37%5%35%5%5%6%41%
1260
11th to 20thNight
11%6%35%6%346%8%11%40%
1260
21st to endNight
8%3244245%6%9%52%
1260
July1st to 10thNight
7%323424446%61%
1260
11th to 20thNight
5%314323345%66%
1260
21st to endNight
321213236%75%
1544
August1st to 10thNight
431342335%6%66%
1499
11th to 20thNight
321321245%6%70%
1602
21st to endNight
7%3133245%6%9%57%
1835
September1st to 10thNight
6%31422445%6%63%
1800
11th to 20thNight
12%5%345%2445%6%50%
1822
21st to endNight
13%6%25%5%36%45%6%45%
2051
October1st to 10thNight
14%7%36%5%345%46%44%
2160
11th to 20thNight
20%8%35%6%445%5%6%33%
2160
21st to endNight
23%8%26%6%3445%6%33%
2486
November1st to 10thNight
24%10%47%7%46%5%5%5%23%
2590
11th to 20thNight
24%9%46%7%45%5%5%6%25%
2660
21st to endNight
20%11%5%9%7%45%5%5%5%23%
2660
December1st to 10thNight
20%12%5%8%5%36%5%5%5%25%
2660
11th to 20thNight
24%14%5%10%7%46%5%45%16%
3501
21st to endNight
23%14%5%9%8%45%44419%
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
68%9%9%9%4
1329
11th to 20thDay
69%10%12%7%2
1334
21st to endDay
72%8%11%7%2
1735
February1st to 10thDay
66%10%11%8%4
1620
11th to 20thDay
61%9%13%13%5%
1584
21st to endDay
60%8%14%12%5%1
1340
March1st to 10thDay
56%10%15%15%41
1885
11th to 20thDay
57%9%14%15%41
1980
21st to endDay
58%10%16%13%2
2214
April1st to 10thDay
53%9%20%14%3
2160
11th to 20thDay
49%9%15%18%8%1
2224
21st to endDay
46%11%16%20%7%1
2353
May1st to 10thDay
41%10%21%20%7%1
2520
11th to 20thDay
41%9%22%21%6%
2480
21st to endDay
44%8%23%21%5%
2746
June1st to 10thDay
43%8%23%18%7%1
2700
11th to 20thDay
39%9%26%22%4
2700
21st to endDay
32%9%26%22%10%1
2700
July1st to 10thDay
26%8%21%30%13%3
2626
11th to 20thDay
23%8%22%33%14%1
2619
21st to endDay
12%5%23%41%15%3
2618
August1st to 10thDay
20%7%25%33%13%2
2419
11th to 20thDay
22%8%22%32%13%2
2298
21st to endDay
26%8%24%34%8%1
2520
September1st to 10thDay
29%9%21%25%13%2
2160
11th to 20thDay
39%9%17%21%13%1
2135
21st to endDay
42%8%18%22%10%1
1908
October1st to 10thDay
47%8%17%21%7%
1800
11th to 20thDay
58%8%16%14%4
1800
21st to endDay
56%10%14%13%7%
1867
November1st to 10thDay
66%9%11%10%31
1488
11th to 20thDay
64%6%13%11%5%1
1520
21st to endDay
66%8%11%11%5%
1520
December1st to 10thDay
63%7%11%14%4
1520
11th to 20thDay
71%10%11%5%2
1703
21st to endDay
70%11%11%5%3
2442
January1st to 10thNight
68%9%11%7%4
2836
11th to 20thNight
65%9%13%10%21
2843
21st to endNight
63%8%11%14%31
2844
February1st to 10thNight
62%9%14%10%5%1
2340
11th to 20thNight
56%9%13%15%6%
2274
21st to endNight
59%7%13%15%6%1
1916
March1st to 10thNight
54%9%15%16%5%
2070
11th to 20thNight
55%9%15%16%42
1980
21st to endNight
60%9%15%15%2
2142
April1st to 10thNight
52%9%19%16%4
1800
11th to 20thNight
48%8%16%20%6%2
1683
21st to endNight
49%8%16%17%9%1
1606
May1st to 10thNight
37%10%20%21%11%1
1440
11th to 20thNight
39%10%21%22%8%1
1416
21st to endNight
40%9%24%21%5%
1526
June1st to 10thNight
44%8%18%23%5%2
1260
11th to 20thNight
37%11%24%23%5%
1260
21st to endNight
25%11%27%24%10%3
1260
July1st to 10thNight
24%10%20%28%16%3
1225
11th to 20thNight
22%6%21%31%18%2
1218
21st to endNight
10%6%19%38%22%5%
1458
August1st to 10thNight
19%7%21%32%17%4
1491
11th to 20thNight
14%8%24%32%16%6%
1602
21st to endNight
24%8%20%35%12%1
1835
September1st to 10thNight
21%7%21%31%15%4
1800
11th to 20thNight
36%8%14%20%17%4
1822
21st to endNight
39%8%16%23%13%1
2051
October1st to 10thNight
44%6%16%22%11%
2160
11th to 20thNight
49%8%18%18%8%
2160
21st to endNight
52%7%14%19%9%
2486
November1st to 10thNight
61%9%13%13%4
2590
11th to 20thNight
60%8%14%11%5%2
2660
21st to endNight
63%9%12%9%6%1
2660
December1st to 10thNight
61%8%12%13%6%
2660
11th to 20thNight
71%10%11%43
3497
21st to endNight
66%10%12%8%3
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
27%11%31%17%12%2
180
11th to 20thDay
26%12%23%25%15%
180
21st to endDay
29%7%24%24%15%1
267
February1st to 10thDay
32%8%22%27%10%1
340
11th to 20thDay
25%10%18%32%14%1
335
21st to endDay
19%15%22%25%16%3
284
March1st to 10thDay
21%8%19%30%18%4
420
11th to 20thDay
22%6%21%26%19%6%
420
21st to endDay
20%8%21%27%20%3
462
April1st to 10thDay
19%10%22%24%19%6%
420
11th to 20thDay
18%5%17%30%21%9%
412
21st to endDay
17%6%24%25%23%6%
420
May1st to 10thDay
13%5%14%28%34%6%
423
11th to 20thDay
15%411%26%35%9%
448
21st to endDay
12%316%31%28%10%
507
June1st to 10thDay
13%422%30%25%6%
630
11th to 20thDay
10%425%34%22%5%
630
21st to endDay
8%217%33%28%12%
630
July1st to 10thDay
9%114%29%34%13%
621
11th to 20thDay
5%116%31%33%13%
618
21st to endDay
3111%28%37%21%
518
August1st to 10thDay
6%111%21%35%25%
447
11th to 20thDay
37%21%46%23%
437
21st to endDay
7%213%27%37%15%
495
September1st to 10thDay
11%18%33%37%10%
450
11th to 20thDay
13%111%26%35%14%
450
21st to endDay
13%315%27%33%9%
450
October1st to 10thDay
18%414%26%26%12%
450
11th to 20thDay
25%5%13%26%24%6%
450
21st to endDay
23%11%22%25%15%3
398
November1st to 10thDay
27%7%28%22%17%
180
11th to 20thDay
22%7%26%23%19%3
180
21st to endDay
27%11%22%23%14%4
180
December1st to 10thDay
29%7%19%26%16%3
180
11th to 20thDay
31%12%22%21%14%
180
21st to endDay
35%10%22%26%7%1
198
January1st to 10thNight
31%11%22%21%13%2
850
11th to 20thNight
31%7%18%24%19%2
846
21st to endNight
27%6%19%25%20%4
834
February1st to 10thNight
30%10%18%27%12%3
720
11th to 20thNight
23%7%21%27%18%3
704
21st to endNight
28%8%23%21%14%6%
592
March1st to 10thNight
21%9%19%27%19%5%
720
11th to 20thNight
22%6%24%24%19%4
720
21st to endNight
21%7%23%28%16%5%
792
April1st to 10thNight
21%6%22%24%23%4
720
11th to 20thNight
19%5%25%27%18%6%
615
21st to endNight
18%5%27%31%15%5%
526
May1st to 10thNight
11%424%32%25%4
360
11th to 20thNight
12%418%32%27%7%
354
21st to endNight
13%421%33%25%4
389
June1st to 10thNight
15%5%22%33%23%3
360
11th to 20thNight
13%327%36%17%4
360
21st to endNight
9%225%29%27%9%
360
July1st to 10thNight
9%117%37%33%4
350
11th to 20thNight
8%219%38%28%5%
348
21st to endNight
4217%34%35%9%
394
August1st to 10thNight
5%310%32%41%9%
425
11th to 20thNight
417%28%43%16%
534
21st to endNight
8%216%32%34%8%
647
September1st to 10thNight
8%212%34%33%13%
720
11th to 20thNight
14%210%26%30%18%
720
21st to endNight
16%214%29%28%11%
720
October1st to 10thNight
17%312%27%28%14%
720
11th to 20thNight
23%414%25%23%11%
720
21st to endNight
27%5%17%26%20%5%
792
November1st to 10thNight
30%5%20%26%17%2
740
11th to 20thNight
27%10%21%23%15%4
760
21st to endNight
28%7%21%22%16%5%
760
December1st to 10thNight
27%6%21%24%19%3
760
11th to 20thNight
30%9%23%26%11%1
841
21st to endNight
30%12%27%21%9%1
935
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