Jasper
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jasper clear sky chart from 2005-11-06 to 2024-03-08.

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
31%
23587
9%
81265
5%
23493
35%
23493
13%
59154

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%
1028
7%
5014
4%
1006
28%
1006
7%
3783
January11th to 20thNight
25%
885
18%
4622
6%
874
29%
874
8%
3085
January21st to endNight
20%
826
8%
4853
5%
814
30%
814
5%
3816
February1st to 10thNight
24%
760
8%
2660
6%
760
29%
760
9%
2072
February11th to 20thNight
27%
743
10%
2501
7%
740
34%
740
13%
1851
February21st to endNight
29%
628
14%
1900
8%
628
36%
628
17%
1389
March1st to 10thNight
29%
750
13%
2249
9%
750
35%
750
15%
1667
March11th to 20thNight
25%
720
13%
2125
6%
720
31%
720
18%
1510
March21st to endNight
29%
792
9%
1980
3%
792
31%
792
15%
1555
April1st to 10thNight
32%
720
8%
1800
3%
720
35%
720
12%
1447
April11th to 20thNight
30%
592
11%
1660
5%
592
34%
592
16%
1223
April21st to endNight
35%
399
9%
1479
9%
399
39%
399
13%
1073
May1st to 10thNight
46%
360
5%
1440
6%
360
48%
360
13%
1046
May11th to 20thNight
48%
354
6%
1307
4%
354
50%
354
18%
871
May21st to endNight
42%
388
1%
1342
0%
388
42%
388
15%
989
June1st to 10thNight
37%
360
0%
1080
0%
360
37%
360
17%
804
June11th to 20thNight
33%
360
0%
1080
0%
360
33%
360
12%
874
June21st to endNight
46%
360
0%
1080
0%
360
46%
360
18%
776
July1st to 10thNight
49%
350
0%
1050
0%
350
49%
350
22%
714
July11th to 20thNight
45%
348
1%
1048
0%
348
45%
348
19%
739
July21st to endNight
54%
394
6%
1464
5%
372
57%
372
21%
882
August1st to 10thNight
56%
358
6%
1424
9%
356
59%
356
17%
923
August11th to 20thNight
52%
356
12%
1424
16%
356
56%
356
22%
858
August21st to endNight
42%
620
13%
1808
9%
620
45%
620
21%
1246
September1st to 10thNight
43%
720
11%
1800
7%
720
45%
720
24%
1284
September11th to 20thNight
42%
720
12%
1857
6%
720
44%
720
24%
1340
September21st to endNight
32%
720
14%
1980
7%
720
37%
720
19%
1421
October1st to 10thNight
33%
720
9%
2127
7%
720
36%
720
16%
1579
October11th to 20thNight
29%
720
10%
2301
6%
720
36%
720
15%
1680
October21st to endNight
23%
792
9%
2574
5%
792
29%
792
12%
1937
November1st to 10thNight
20%
740
8%
2526
5%
740
24%
740
10%
1953
November11th to 20thNight
22%
934
8%
2834
2%
934
27%
934
13%
2106
November21st to endNight
21%
950
8%
2850
2%
950
27%
950
13%
2195
December1st to 10thNight
25%
950
13%
2850
6%
950
31%
950
15%
2094
December11th to 20thNight
25%
1035
7%
3731
4%
1034
29%
1034
10%
2928
December21st to endNight
25%
1135
7%
5445
4%
1114
32%
1114
10%
3444

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
8%11%5%11%9%5%7%6%7%7%24%
77794
Night
49%5%10%9%5%7%7%7%9%28%
81712
TransparencyDay
58%8%14%14%5%1
77493
Night
52%9%16%16%6%1
81593
SeeingDay
19%14%29%24%11%3
15069
Night
12%11%36%30%11%1
23636

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
15%8%14%13%9%10%8%8%9%16%
1899
11th to 20thDay
26%5%12%8%46%9%9%7%32%
2183
21st to endDay
216%5%12%10%5%8%7%8%8%18%
2794
February1st to 10thDay
29%6%14%10%5%8%7%8%9%22%
1520
11th to 20thDay
19%6%15%10%5%7%8%8%8%22%
1564
21st to endDay
17%6%14%13%7%6%8%9%7%23%
1553
March1st to 10thDay
8%5%11%11%7%9%9%8%10%22%
1871
11th to 20thDay
18%6%12%10%6%9%7%9%8%25%
1833
21st to endDay
214%7%16%12%6%8%7%7%8%14%
2376
April1st to 10thDay
313%8%16%11%7%10%7%5%6%14%
2160
11th to 20thDay
413%8%15%11%5%6%6%5%7%19%
2250
21st to endDay
8%15%7%12%9%46%5%7%7%20%
2479
May1st to 10thDay
9%19%6%13%8%5%5%5%6%6%18%
2520
11th to 20thDay
9%13%5%8%8%46%5%6%8%27%
2586
21st to endDay
17%15%5%10%7%5%6%5%5%5%21%
2930
June1st to 10thDay
19%12%5%10%8%46%6%7%6%18%
2880
11th to 20thDay
21%16%6%10%9%5%7%5%5%412%
2880
21st to endDay
13%11%5%11%9%46%6%5%7%22%
2880
July1st to 10thDay
16%10%48%8%47%6%6%7%24%
2880
11th to 20thDay
13%9%48%9%5%6%6%6%7%27%
2875
21st to endDay
10%8%410%8%5%7%6%5%7%31%
2764
August1st to 10thDay
11%10%48%8%5%6%6%7%7%28%
2507
11th to 20thDay
10%8%37%7%47%6%6%9%33%
2475
21st to endDay
13%11%48%7%46%6%6%8%27%
2546
September1st to 10thDay
11%10%49%8%5%6%5%46%31%
2160
11th to 20thDay
11%10%38%6%46%6%6%6%34%
2102
21st to endDay
9%11%5%9%8%5%6%5%7%6%29%
1980
October1st to 10thDay
7%14%410%8%46%5%7%8%28%
1832
11th to 20thDay
5%11%49%9%6%7%7%7%9%27%
1658
21st to endDay
412%6%10%9%5%7%8%7%9%25%
1782
November1st to 10thDay
312%6%12%11%6%8%6%7%8%22%
1548
11th to 20thDay
27%5%9%7%5%8%7%8%12%29%
1330
21st to endDay
210%5%11%9%5%7%8%8%9%26%
1330
December1st to 10thDay
28%5%12%10%5%8%9%8%8%25%
1330
11th to 20thDay
210%5%10%10%7%9%7%7%9%24%
1447
21st to endDay
8%48%8%5%8%6%9%11%32%
2090
January1st to 10thNight
17%6%14%15%6%8%6%7%10%19%
5046
11th to 20thNight
16%5%10%9%5%7%8%9%11%28%
4741
21st to endNight
212%5%13%10%6%8%7%7%9%20%
4862
February1st to 10thNight
39%5%12%12%5%8%8%8%9%20%
2660
11th to 20thNight
28%411%9%6%9%8%7%10%25%
2499
21st to endNight
29%6%11%10%5%8%8%7%10%24%
1900
March1st to 10thNight
8%5%11%11%5%8%8%8%9%26%
2249
11th to 20thNight
17%6%8%9%5%8%8%9%10%29%
2124
21st to endNight
211%7%14%8%5%7%8%7%10%22%
1980
April1st to 10thNight
210%7%12%10%6%8%7%8%9%21%
1800
11th to 20thNight
49%7%10%9%47%6%7%9%29%
1660
21st to endNight
6%11%5%10%7%37%6%7%9%29%
1479
May1st to 10thNight
9%11%48%7%5%6%7%8%9%26%
1440
11th to 20thNight
7%8%47%7%5%6%7%6%8%37%
1307
21st to endNight
13%10%47%8%5%5%6%5%8%29%
1342
June1st to 10thNight
13%9%48%6%5%6%6%6%6%29%
1080
11th to 20thNight
18%11%5%9%8%5%7%5%6%6%19%
1080
21st to endNight
10%6%38%7%5%8%6%7%9%32%
1080
July1st to 10thNight
14%7%35%447%6%7%9%34%
1080
11th to 20thNight
11%7%37%6%37%6%8%9%34%
1084
21st to endNight
7%5%47%6%36%6%6%7%42%
1550
August1st to 10thNight
9%8%37%7%46%6%7%8%34%
1432
11th to 20thNight
10%7%46%5%25%5%6%7%43%
1424
21st to endNight
13%7%36%6%36%6%7%8%35%
1808
September1st to 10thNight
12%9%36%7%46%6%5%6%37%
1800
11th to 20thNight
10%10%39%6%35%5%6%7%36%
1857
21st to endNight
8%9%46%7%45%6%8%9%33%
1980
October1st to 10thNight
6%13%5%9%8%45%5%7%8%30%
2127
11th to 20thNight
5%12%47%8%46%7%7%11%29%
2301
21st to endNight
311%410%9%5%6%7%9%8%26%
2574
November1st to 10thNight
311%6%10%10%6%7%7%7%9%23%
2526
11th to 20thNight
19%5%9%8%5%7%8%8%11%28%
2834
21st to endNight
29%6%9%11%6%7%7%8%11%25%
2850
December1st to 10thNight
37%5%10%10%5%7%7%7%10%28%
2850
11th to 20thNight
18%6%12%10%6%9%7%8%9%23%
3740
21st to endNight
18%5%9%8%5%7%7%8%10%31%
5566

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
61%11%16%10%31
1899
11th to 20thDay
50%10%10%12%15%3
2204
21st to endDay
59%13%15%9%4
2794
February1st to 10thDay
59%7%12%11%9%2
1520
11th to 20thDay
60%7%10%16%6%
1572
21st to endDay
58%6%13%14%7%2
1553
March1st to 10thDay
55%11%14%13%6%
1871
11th to 20thDay
54%9%16%16%6%
1833
21st to endDay
67%8%12%9%4
2376
April1st to 10thDay
70%7%11%10%2
2160
11th to 20thDay
65%7%12%14%2
2250
21st to endDay
64%8%13%12%2
2479
May1st to 10thDay
67%6%12%12%3
2520
11th to 20thDay
56%7%16%15%7%
2590
21st to endDay
65%8%12%11%5%
2931
June1st to 10thDay
65%7%11%11%5%1
2880
11th to 20thDay
73%6%10%7%3
2880
21st to endDay
62%8%12%12%5%1
2880
July1st to 10thDay
57%8%11%17%6%1
2801
11th to 20thDay
56%8%13%16%6%
2788
21st to endDay
52%6%14%20%8%
2610
August1st to 10thDay
54%9%16%15%6%
2490
11th to 20thDay
48%7%18%20%6%1
2475
21st to endDay
54%7%12%20%6%
2546
September1st to 10thDay
55%6%14%21%41
2160
11th to 20thDay
50%6%16%19%8%1
2102
21st to endDay
55%8%13%15%7%1
1980
October1st to 10thDay
54%7%16%18%4
1832
11th to 20thDay
53%11%16%17%3
1658
21st to endDay
58%8%15%15%5%
1782
November1st to 10thDay
59%10%14%13%41
1548
11th to 20thDay
49%10%23%13%5%1
1330
21st to endDay
54%10%18%10%5%3
1330
December1st to 10thDay
58%9%12%15%6%1
1330
11th to 20thDay
55%10%15%12%6%1
1449
21st to endDay
42%10%22%15%10%
2090
January1st to 10thNight
60%8%16%11%41
5046
11th to 20thNight
49%9%10%12%18%2
4782
21st to endNight
61%12%12%11%3
4862
February1st to 10thNight
61%8%11%11%8%1
2660
11th to 20thNight
55%8%16%15%6%1
2501
21st to endNight
54%6%12%20%8%1
1900
March1st to 10thNight
52%9%15%17%7%1
2249
11th to 20thNight
48%8%18%20%5%
2125
21st to endNight
56%9%17%14%4
1980
April1st to 10thNight
60%9%15%15%2
1800
11th to 20thNight
52%8%16%18%5%
1660
21st to endNight
53%9%15%18%5%
1479
May1st to 10thNight
53%10%18%16%3
1440
11th to 20thNight
43%12%16%19%10%
1307
21st to endNight
53%9%16%18%4
1342
June1st to 10thNight
55%6%15%16%6%1
1080
11th to 20thNight
63%8%16%9%4
1080
21st to endNight
48%10%19%17%5%1
1080
July1st to 10thNight
44%9%19%21%7%1
1050
11th to 20thNight
45%10%19%19%6%1
1048
21st to endNight
39%8%20%26%7%
1464
August1st to 10thNight
45%8%22%21%4
1424
11th to 20thNight
39%7%24%23%6%
1424
21st to endNight
45%9%20%20%7%
1808
September1st to 10thNight
46%7%18%22%6%1
1800
11th to 20thNight
48%6%19%19%8%1
1857
21st to endNight
44%11%20%18%6%1
1980
October1st to 10thNight
53%8%16%19%4
2127
11th to 20thNight
50%11%17%19%3
2301
21st to endNight
55%9%17%14%5%
2574
November1st to 10thNight
60%8%16%13%3
2526
11th to 20thNight
51%12%19%12%6%
2834
21st to endNight
54%11%16%12%5%2
2850
December1st to 10thNight
53%8%16%16%7%1
2850
11th to 20thNight
57%12%14%12%4
3737
21st to endNight
45%9%20%19%5%1
5566

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
9%9%21%41%16%3
180
11th to 20thDay
11%7%29%37%12%4
180
21st to endDay
16%8%33%29%11%4
198
February1st to 10thDay
17%13%36%21%11%3
180
11th to 20thDay
15%14%29%25%13%5%
264
21st to endDay
12%17%39%19%11%2
375
March1st to 10thDay
15%21%31%20%11%3
449
11th to 20thDay
15%19%35%19%9%3
420
21st to endDay
17%20%30%19%9%5%
462
April1st to 10thDay
19%19%31%22%7%1
420
11th to 20thDay
17%18%27%24%9%5%
412
21st to endDay
21%18%26%21%10%4
420
May1st to 10thDay
22%16%31%22%7%2
423
11th to 20thDay
17%11%26%30%13%3
557
21st to endDay
23%9%24%24%17%3
692
June1st to 10thDay
23%15%30%23%9%
810
11th to 20thDay
30%14%27%20%8%1
810
21st to endDay
20%14%24%24%15%3
810
July1st to 10thDay
20%12%28%27%11%2
796
11th to 20thDay
20%11%31%25%11%2
787
21st to endDay
15%13%27%25%16%4
510
August1st to 10thDay
17%10%26%28%14%5%
447
11th to 20thDay
16%14%33%22%10%4
437
21st to endDay
19%14%32%21%12%3
495
September1st to 10thDay
24%16%27%20%11%3
450
11th to 20thDay
19%14%28%25%11%2
450
21st to endDay
26%20%28%15%8%3
450
October1st to 10thDay
21%16%29%19%10%4
450
11th to 20thDay
21%13%30%23%11%3
308
21st to endDay
17%12%30%33%7%2
297
November1st to 10thDay
20%11%37%23%6%3
212
11th to 20thDay
16%11%32%28%9%4
180
21st to endDay
18%16%24%26%10%6%
180
December1st to 10thDay
12%6%29%30%16%7%
180
11th to 20thDay
9%8%30%34%13%6%
180
21st to endDay
8%7%26%37%16%6%
198
January1st to 10thNight
10%12%40%31%6%1
1040
11th to 20thNight
8%14%41%28%7%2
901
21st to endNight
9%16%43%24%7%1
836
February1st to 10thNight
11%14%37%27%11%1
760
11th to 20thNight
8%11%40%31%9%1
744
21st to endNight
7%12%39%28%11%3
628
March1st to 10thNight
6%14%40%28%11%1
750
11th to 20thNight
6%13%45%26%9%1
720
21st to endNight
8%12%36%30%11%2
792
April1st to 10thNight
8%13%29%36%12%1
720
11th to 20thNight
10%10%35%29%15%1
592
21st to endNight
15%8%31%35%11%1
399
May1st to 10thNight
13%7%23%45%11%
360
11th to 20thNight
12%329%40%16%1
354
21st to endNight
16%7%25%31%21%1
389
June1st to 10thNight
20%331%32%14%1
360
11th to 20thNight
24%8%23%32%13%1
360
21st to endNight
14%8%22%34%19%2
360
July1st to 10thNight
20%5%19%40%16%1
350
11th to 20thNight
16%9%23%31%20%1
348
21st to endNight
9%5%19%42%23%1
394
August1st to 10thNight
15%415%39%27%1
358
11th to 20thNight
14%5%20%40%19%2
356
21st to endNight
17%7%26%38%12%1
620
September1st to 10thNight
18%8%25%35%14%1
720
11th to 20thNight
16%7%26%33%17%1
720
21st to endNight
18%12%31%27%12%1
720
October1st to 10thNight
17%9%32%33%9%1
720
11th to 20thNight
14%10%39%28%8%1
720
21st to endNight
13%13%41%25%6%1
792
November1st to 10thNight
12%13%42%26%6%1
740
11th to 20thNight
11%16%42%26%41
934
21st to endNight
11%13%47%22%6%1
950
December1st to 10thNight
9%12%43%27%9%1
950
11th to 20thNight
9%10%45%27%8%1
1035
21st to endNight
6%10%45%29%9%1
1144
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