Outlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Outlook clear sky chart from 2005-11-06 to 2024-02-05.

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
39%
24134
13%
80558
8%
24068
44%
24068
21%
52617

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
35%
936
9%
4683
5%
926
39%
926
10%
3223
January11th to 20thNight
25%
942
10%
4678
5%
930
32%
930
9%
3439
January21st to endNight
26%
1029
7%
4947
4%
1023
33%
1023
10%
3118
February1st to 10thNight
34%
833
12%
2493
8%
833
39%
833
17%
1844
February11th to 20thNight
35%
700
14%
2273
10%
700
40%
700
17%
1603
February21st to endNight
46%
592
16%
1905
12%
592
52%
592
23%
1271
March1st to 10thNight
39%
720
14%
2160
10%
720
43%
720
21%
1505
March11th to 20thNight
37%
720
17%
1980
10%
720
43%
720
24%
1358
March21st to endNight
39%
698
13%
2084
8%
698
45%
698
20%
1476
April1st to 10thNight
42%
540
17%
1800
12%
540
49%
540
27%
1089
April11th to 20thNight
32%
533
14%
1684
9%
533
37%
533
19%
1175
April21st to endNight
34%
540
13%
1480
9%
540
38%
540
21%
1055
May1st to 10thNight
46%
540
14%
1440
10%
540
48%
540
30%
935
May11th to 20thNight
45%
531
12%
1418
6%
531
48%
531
32%
912
May21st to endNight
49%
442
6%
1410
5%
440
51%
440
24%
909
June1st to 10thNight
46%
360
2%
1121
2%
360
47%
360
28%
695
June11th to 20thNight
43%
360
0%
1080
0%
360
43%
360
20%
748
June21st to endNight
60%
360
0%
1080
0%
360
60%
360
33%
645
July1st to 10thNight
62%
350
2%
1224
1%
350
62%
350
35%
635
July11th to 20thNight
51%
348
7%
1218
5%
348
56%
348
33%
652
July21st to endNight
62%
466
15%
1370
10%
440
67%
440
48%
674
August1st to 10thNight
63%
537
16%
1424
10%
534
67%
534
45%
794
August11th to 20thNight
64%
534
19%
1500
15%
534
67%
534
41%
853
August21st to endNight
56%
594
24%
1836
17%
594
63%
594
39%
1018
September1st to 10thNight
50%
540
18%
1800
16%
540
55%
540
31%
1015
September11th to 20thNight
55%
540
21%
1800
21%
540
62%
540
30%
1036
September21st to endNight
44%
672
25%
2048
17%
672
53%
672
38%
1137
October1st to 10thNight
41%
720
20%
2160
13%
720
47%
720
27%
1396
October11th to 20thNight
41%
720
24%
2160
12%
720
50%
720
32%
1303
October21st to endNight
29%
980
16%
2615
5%
980
37%
980
21%
1884
November1st to 10thNight
27%
925
14%
2590
7%
925
32%
925
17%
1938
November11th to 20thNight
31%
950
13%
2660
5%
950
38%
950
18%
1958
November21st to endNight
24%
950
11%
2705
4%
950
29%
950
17%
1967
December1st to 10thNight
29%
950
10%
2978
4%
950
36%
950
16%
2176
December11th to 20thNight
25%
950
9%
3705
4%
949
33%
949
10%
2760
December21st to endNight
33%
1032
9%
5049
6%
1026
40%
1026
15%
2421

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
10%8%37%6%45%5%6%8%37%
77533
Night
7%8%48%7%46%5%6%8%38%
81268
TransparencyDay
44%6%17%23%9%1
77239
Night
44%6%16%23%10%1
81142
SeeingDay
13%8%27%30%17%5%
14660
Night
12%7%30%35%14%2
24189

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
6%13%5%9%11%6%8%6%45%27%
2219
11th to 20thDay
5%7%49%10%7%11%9%7%8%23%
2199
21st to endDay
6%11%49%7%5%6%5%6%8%33%
2634
February1st to 10thDay
7%12%6%13%7%5%8%6%6%7%23%
1580
11th to 20thDay
8%12%5%10%10%5%6%5%6%7%27%
1575
21st to endDay
5%10%5%11%11%6%8%6%6%8%24%
1350
March1st to 10thDay
8%12%7%10%10%5%8%5%5%8%22%
1800
11th to 20thDay
8%11%5%9%7%46%5%5%9%32%
1979
21st to endDay
9%10%410%8%45%5%5%8%31%
2272
April1st to 10thDay
7%8%47%6%46%7%7%8%36%
2160
11th to 20thDay
11%12%5%9%8%45%6%6%8%29%
2225
21st to endDay
15%10%47%6%35%447%35%
2479
May1st to 10thDay
13%7%36%7%45%6%6%9%35%
2520
11th to 20thDay
8%6%26%6%46%6%7%9%40%
2478
21st to endDay
19%6%36%5%345%5%8%36%
2863
June1st to 10thDay
14%7%26%6%35%5%7%7%39%
2834
11th to 20thDay
21%6%36%6%45%5%6%8%31%
2880
21st to endDay
10%5%25%6%45%6%8%10%40%
2877
July1st to 10thDay
7%3245%35%6%7%11%47%
2700
11th to 20thDay
10%424435%6%6%9%47%
2700
21st to endDay
6%324325%5%6%8%56%
2864
August1st to 10thDay
8%424435%5%6%8%49%
2507
11th to 20thDay
10%5%25%5%35%5%5%8%46%
2400
21st to endDay
12%42443445%8%50%
2520
September1st to 10thDay
10%425%5%45%5%5%7%48%
2160
11th to 20thDay
13%7%245%335%6%7%43%
2160
21st to endDay
11%425%424348%52%
1910
October1st to 10thDay
14%9%35%42445%7%41%
1800
11th to 20thDay
9%8%47%5%35%5%6%7%41%
1792
21st to endDay
10%10%49%6%47%5%6%7%32%
1728
November1st to 10thDay
14%14%6%7%7%45%45%432%
1488
11th to 20thDay
8%11%5%13%8%5%6%6%5%6%28%
1520
21st to endDay
9%11%5%11%8%5%6%5%5%7%28%
1473
December1st to 10thDay
6%12%6%11%11%5%8%5%5%7%25%
1198
11th to 20thDay
6%11%5%11%9%6%7%5%46%30%
1439
21st to endDay
48%38%7%45%5%6%7%45%
2250
January1st to 10thNight
49%5%12%10%5%7%7%7%8%27%
4726
11th to 20thNight
46%411%12%8%11%9%6%7%22%
4699
21st to endNight
6%10%47%8%5%7%6%6%8%34%
5027
February1st to 10thNight
7%11%6%11%8%5%6%7%6%7%26%
2493
11th to 20thNight
6%11%6%11%6%46%7%7%7%28%
2272
21st to endNight
47%5%9%9%48%6%8%9%32%
1905
March1st to 10thNight
7%9%410%8%46%5%7%8%32%
2160
11th to 20thNight
6%11%47%6%46%5%6%8%37%
1980
21st to endNight
9%8%6%9%7%36%6%7%9%30%
2084
April1st to 10thNight
7%8%37%7%445%7%8%42%
1800
11th to 20thNight
10%10%5%8%8%35%5%7%7%31%
1684
21st to endNight
11%11%46%7%46%5%5%7%34%
1480
May1st to 10thNight
12%6%36%5%25%5%7%7%42%
1440
11th to 20thNight
9%6%36%6%345%5%8%45%
1418
21st to endNight
17%6%245%35%5%6%6%40%
1410
June1st to 10thNight
12%426%5%346%6%10%42%
1121
11th to 20thNight
19%6%246%46%6%7%7%34%
1080
21st to endNight
9%324435%6%7%10%47%
1080
July1st to 10thNight
6%4146%245%8%10%51%
1259
11th to 20thNight
8%4244245%6%10%51%
1260
21st to endNight
321332446%9%62%
1451
August1st to 10thNight
6%3234245%7%8%57%
1432
11th to 20thNight
6%3235%45%46%9%52%
1500
21st to endNight
8%5%234345%6%7%55%
1836
September1st to 10thNight
9%5%246%445%6%7%49%
1800
11th to 20thNight
10%6%26%4245%5%8%48%
1800
21st to endNight
8%6%2432445%8%54%
2048
October1st to 10thNight
14%9%25%5%345%5%6%42%
2160
11th to 20thNight
6%7%36%5%35%447%50%
2160
21st to endNight
9%12%5%8%7%45%5%5%6%34%
2615
November1st to 10thNight
14%15%5%7%6%35%45%6%30%
2590
11th to 20thNight
6%11%5%11%8%46%5%6%7%30%
2660
21st to endNight
7%11%5%12%7%36%5%5%7%32%
2705
December1st to 10thNight
7%9%5%11%10%6%7%6%5%6%28%
2978
11th to 20thNight
8%12%6%11%10%5%6%6%6%7%25%
3753
21st to endNight
36%36%6%45%446%53%
5402

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
59%414%15%7%
2219
11th to 20thDay
57%7%14%16%5%1
2220
21st to endDay
48%5%19%22%5%
2634
February1st to 10thDay
59%5%13%16%6%
1580
11th to 20thDay
56%5%14%17%8%1
1584
21st to endDay
56%5%13%17%8%
1350
March1st to 10thDay
61%6%13%17%3
1800
11th to 20thDay
49%7%16%21%7%
1980
21st to endDay
50%8%18%18%6%
2272
April1st to 10thDay
44%7%14%24%11%
2160
11th to 20thDay
52%6%15%17%8%1
2225
21st to endDay
49%5%14%23%7%1
2479
May1st to 10thDay
44%5%13%25%10%1
2520
11th to 20thDay
38%7%13%29%12%1
2482
21st to endDay
46%5%13%22%12%1
2863
June1st to 10thDay
42%6%15%26%10%1
2834
11th to 20thDay
50%7%14%21%8%1
2880
21st to endDay
37%8%21%26%8%1
2877
July1st to 10thDay
28%8%23%32%9%1
2626
11th to 20thDay
33%9%20%28%10%
2619
21st to endDay
26%6%21%35%11%1
2705
August1st to 10thDay
31%8%22%27%11%1
2491
11th to 20thDay
35%6%22%28%8%1
2400
21st to endDay
33%5%16%33%12%1
2520
September1st to 10thDay
35%6%17%27%13%3
2160
11th to 20thDay
38%7%15%28%10%2
2160
21st to endDay
32%415%34%13%1
1910
October1st to 10thDay
42%5%19%26%8%
1800
11th to 20thDay
41%5%15%28%10%1
1792
21st to endDay
50%6%16%21%7%
1728
November1st to 10thDay
56%6%13%17%7%
1488
11th to 20thDay
56%7%15%17%5%
1520
21st to endDay
56%5%18%17%4
1473
December1st to 10thDay
60%6%14%14%6%1
1198
11th to 20thDay
56%5%22%11%6%
1440
21st to endDay
38%6%15%21%15%5%
2250
January1st to 10thNight
53%7%19%17%4
4726
11th to 20thNight
60%5%15%14%6%1
4740
21st to endNight
48%7%18%22%5%
5027
February1st to 10thNight
54%6%13%18%7%
2493
11th to 20thNight
51%6%16%17%9%1
2273
21st to endNight
46%5%15%24%10%
1905
March1st to 10thNight
48%5%18%20%7%
2160
11th to 20thNight
44%7%16%22%10%1
1980
21st to endNight
48%8%17%18%9%
2084
April1st to 10thNight
39%415%26%15%1
1800
11th to 20thNight
50%5%12%19%11%3
1684
21st to endNight
48%6%11%23%10%2
1480
May1st to 10thNight
38%6%11%28%16%1
1440
11th to 20thNight
37%6%11%28%16%2
1418
21st to endNight
42%7%13%22%16%
1410
June1st to 10thNight
36%7%15%30%11%1
1121
11th to 20thNight
47%8%14%19%11%1
1080
21st to endNight
31%8%21%28%11%1
1080
July1st to 10thNight
25%8%22%35%10%
1224
11th to 20thNight
29%7%19%33%12%
1218
21st to endNight
19%5%19%40%15%2
1370
August1st to 10thNight
22%7%23%33%12%3
1424
11th to 20thNight
27%6%19%34%13%2
1500
21st to endNight
28%5%12%34%19%1
1836
September1st to 10thNight
33%5%14%27%16%5%
1800
11th to 20thNight
34%5%15%30%13%3
1800
21st to endNight
29%5%13%32%18%2
2048
October1st to 10thNight
42%5%15%26%12%
2160
11th to 20thNight
36%415%31%13%1
2160
21st to endNight
50%5%14%23%7%1
2615
November1st to 10thNight
56%5%13%17%8%1
2590
11th to 20thNight
52%7%19%16%5%
2660
21st to endNight
52%7%19%19%4
2705
December1st to 10thNight
56%5%16%16%6%
2978
11th to 20thNight
58%7%16%14%5%
3751
21st to endNight
34%413%28%16%5%
5402

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
14%8%27%27%18%7%
180
11th to 20thDay
12%9%30%29%17%2
180
21st to endDay
13%11%29%31%13%2
252
February1st to 10thDay
14%11%31%29%13%2
252
11th to 20thDay
13%6%36%32%10%3
240
21st to endDay
6%5%29%37%18%5%
198
March1st to 10thDay
13%8%33%30%13%3
240
11th to 20thDay
11%9%28%32%14%5%
420
21st to endDay
14%8%27%32%16%3
462
April1st to 10thDay
10%13%33%27%12%4
420
11th to 20thDay
17%14%31%24%12%2
412
21st to endDay
17%11%27%31%12%1
559
May1st to 10thDay
14%7%26%29%18%6%
603
11th to 20thDay
10%8%25%33%17%7%
625
21st to endDay
16%8%23%27%18%8%
679
June1st to 10thDay
12%10%27%30%18%3
630
11th to 20thDay
20%12%25%25%13%5%
630
21st to endDay
13%8%19%31%23%7%
630
July1st to 10thDay
7%5%23%37%23%6%
621
11th to 20thDay
10%6%26%31%21%6%
618
21st to endDay
8%425%29%27%8%
684
August1st to 10thDay
9%424%30%23%9%
626
11th to 20thDay
12%7%19%28%28%6%
538
21st to endDay
11%6%20%33%24%6%
495
September1st to 10thDay
12%8%32%29%16%4
450
11th to 20thDay
18%8%24%32%16%2
450
21st to endDay
16%8%31%29%13%3
334
October1st to 10thDay
19%5%24%26%19%7%
270
11th to 20thDay
10%10%34%29%15%3
270
21st to endDay
12%14%37%25%11%2
297
November1st to 10thDay
19%9%29%30%10%3
270
11th to 20thDay
14%12%33%29%10%2
270
21st to endDay
8%13%36%31%9%3
270
December1st to 10thDay
11%7%37%31%10%4
207
11th to 20thDay
9%11%42%30%7%2
180
21st to endDay
14%435%26%18%4
198
January1st to 10thNight
8%10%34%35%11%2
950
11th to 20thNight
10%10%38%31%10%1
950
21st to endNight
13%9%35%33%10%1
1045
February1st to 10thNight
11%6%30%37%14%2
833
11th to 20thNight
12%8%32%34%12%2
704
21st to endNight
6%5%25%37%22%5%
592
March1st to 10thNight
10%6%31%37%14%2
720
11th to 20thNight
9%8%34%33%14%2
720
21st to endNight
14%8%27%36%13%2
698
April1st to 10thNight
10%7%31%37%13%1
540
11th to 20thNight
17%8%33%31%11%1
533
21st to endNight
18%10%28%33%10%
540
May1st to 10thNight
14%5%25%38%16%1
540
11th to 20thNight
11%9%29%31%19%2
531
21st to endNight
21%320%36%16%4
442
June1st to 10thNight
14%8%26%31%19%3
360
11th to 20thNight
20%6%21%36%16%1
360
21st to endNight
11%5%19%41%22%2
360
July1st to 10thNight
8%418%46%23%1
350
11th to 20thNight
11%5%27%39%18%1
348
21st to endNight
5%425%41%23%3
466
August1st to 10thNight
6%5%22%37%26%4
537
11th to 20thNight
8%319%42%26%2
534
21st to endNight
11%425%37%22%2
594
September1st to 10thNight
11%428%39%17%1
540
11th to 20thNight
15%5%19%45%16%1
540
21st to endNight
12%6%34%35%13%
672
October1st to 10thNight
19%5%27%34%15%
720
11th to 20thNight
10%5%35%35%13%3
720
21st to endNight
16%9%35%31%8%1
980
November1st to 10thNight
22%9%31%29%8%1
925
11th to 20thNight
11%9%35%32%11%2
950
21st to endNight
13%9%39%30%8%1
950
December1st to 10thNight
12%6%37%30%13%2
950
11th to 20thNight
12%10%34%32%12%1
950
21st to endNight
10%6%32%35%14%3
1045
Page generated at 2024-02-02 04:20:30. Version ac07

Copyright 2024 Attilla Danko


Outlook Clear Sky Chart |Charts Home