Outlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Outlook clear sky chart from 2005-11-05 to 2017-11-30.

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%
15913
12%
47688
8%
15882
44%
15882
21%
32709

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
31%
895
8%
2685
4%
895
34%
895
15%
2006
January16th to endNight
24%
960
12%
2808
5%
960
31%
960
15%
2093
February1st to 15thNight
35%
756
9%
2345
7%
756
39%
756
16%
1735
February16th to endNight
39%
632
13%
2040
8%
632
45%
632
18%
1456
March1st to 15thNight
38%
720
13%
2100
10%
720
42%
720
22%
1452
March16th to endNight
36%
705
12%
2049
7%
705
42%
705
16%
1530
April1st to 15thNight
39%
539
15%
1793
10%
539
45%
539
24%
1124
April16th to endNight
36%
540
14%
1527
10%
540
40%
540
21%
1086
May1st to 15thNight
44%
539
12%
1439
8%
539
46%
539
29%
954
May16th to endNight
44%
467
6%
1402
4%
465
47%
465
21%
969
June1st to 15thNight
46%
360
1%
1107
0%
360
46%
360
23%
752
June16th to endNight
52%
360
0%
1080
0%
360
52%
360
26%
705
July1st to 15thNight
61%
340
1%
1190
1%
340
62%
340
31%
651
July16th to endNight
59%
424
10%
1283
7%
398
63%
398
42%
655
August1st to 15thNight
69%
539
16%
1432
10%
536
72%
536
44%
809
August16th to endNight
59%
573
22%
1747
16%
573
65%
573
41%
961
September1st to 15thNight
56%
540
17%
1800
17%
540
60%
540
32%
1021
September16th to endNight
51%
625
26%
1967
21%
625
59%
625
38%
1079
October1st to 15thNight
40%
720
19%
2160
11%
720
47%
720
27%
1399
October16th to endNight
36%
894
17%
2464
7%
894
42%
894
23%
1718
November1st to 15thNight
33%
950
14%
2660
7%
950
39%
950
19%
1932
November16th to endNight
28%
975
12%
2760
5%
975
34%
975
16%
2048
December1st to 15thNight
27%
900
5%
2841
2%
900
30%
900
10%
2273
December16th to endNight
32%
960
10%
3009
6%
960
38%
960
13%
2301

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
12%8%36%6%35%5%5%7%35%
48748
Night
9%9%47%6%35%5%5%7%35%
47843
Cloud CoverDay
20%7%35%5%34446%34%
48749
Night
17%8%36%5%34446%34%
47845
TransparencyDay
46%6%17%21%7%
48403
Night
46%6%16%21%8%
47692
SeeingDay
15%7%24%28%18%5%
6404
Night
13%6%28%34%15%2
15927

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
8%13%49%9%5%7%6%5%6%23%
1253
16th to endDay
6%11%6%10%6%45%46%9%28%
1416
February1st to 15thDay
8%13%5%11%9%5%8%5%5%5%21%
1527
16th to endDay
8%12%6%12%10%47%45%7%20%
1434
March1st to 15thDay
7%11%5%9%9%47%5%49%24%
1860
16th to endDay
11%10%49%7%45%5%5%8%26%
2174
April1st to 15thDay
9%9%5%7%6%35%6%7%7%31%
2153
16th to endDay
16%11%47%6%34336%31%
2433
May1st to 15thDay
12%6%35%5%35%6%6%9%35%
2511
16th to endDay
19%7%36%5%4445%7%32%
2711
June1st to 15thDay
18%7%25%5%3446%6%33%
2850
16th to endDay
16%6%25%5%35%5%6%9%34%
2877
July1st to 15thDay
9%315%4345%6%9%44%
2700
16th to endDay
7%324325%5%6%9%50%
2796
August1st to 15thDay
12%5%2443445%8%45%
2520
16th to endDay
11%31442345%8%49%
2454
September1st to 15thDay
11%4245%34446%47%
2160
16th to endDay
11%414423348%51%
1992
October1st to 15thDay
16%9%35%42435%6%37%
1800
16th to endDay
12%10%36%436%46%7%33%
1746
November1st to 15thDay
11%11%5%6%5%35%45%6%33%
1528
16th to endDay
10%12%5%9%8%45%446%26%
1524
December1st to 15thDay
8%15%6%12%10%5%7%445%17%
1117
16th to endDay
6%12%5%13%9%6%6%6%47%19%
1212
January1st to 15thNight
7%9%5%9%8%5%7%6%5%8%26%
2685
16th to endNight
6%12%6%10%7%46%5%6%8%26%
2808
February1st to 15thNight
6%11%6%11%7%45%6%5%6%27%
2337
16th to endNight
6%11%6%11%8%36%5%7%7%26%
2040
March1st to 15thNight
7%9%48%6%45%5%6%8%34%
2100
16th to endNight
11%11%48%6%36%6%6%8%26%
2046
April1st to 15thNight
9%8%37%6%3346%8%39%
1793
16th to endNight
12%11%36%6%36%45%6%33%
1527
May1st to 15thNight
13%5%35%5%25%46%7%40%
1439
16th to endNight
16%6%245%35%5%46%37%
1402
June1st to 15thNight
17%425%5%25%6%6%8%34%
1107
16th to endNight
12%5%25%5%35%5%7%8%40%
1080
July1st to 15thNight
6%3145%2447%9%48%
1260
16th to endNight
5%21321445%10%56%
1371
August1st to 15thNight
6%2133245%6%9%54%
1440
16th to endNight
7%322334447%55%
1747
September1st to 15thNight
11%5%23433347%50%
1800
16th to endNight
8%4132135%5%7%54%
1967
October1st to 15thNight
13%8%25%433445%43%
2160
16th to endNight
10%10%46%5%36%345%38%
2464
November1st to 15thNight
11%12%47%5%35%446%33%
2660
16th to endNight
8%13%5%10%6%36%5%46%30%
2760
December1st to 15thNight
10%12%7%11%9%5%5%5%5%7%18%
2841
16th to endNight
5%10%6%11%10%6%7%6%5%7%23%
3009

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
10%14%410%7%5%6%5%5%6%22%
1253
16th to endDay
8%10%5%10%6%45%46%7%27%
1416
February1st to 15thDay
10%12%5%11%9%47%445%23%
1527
16th to endDay
10%11%5%11%8%46%45%7%23%
1434
March1st to 15thDay
25%9%46%7%35%43425%
1860
16th to endDay
28%7%36%5%24446%25%
2175
April1st to 15thDay
17%7%46%5%345%47%32%
2153
16th to endDay
25%9%36%5%23325%33%
2433
May1st to 15thDay
33%5%2442445%5%28%
2511
16th to endDay
34%424423346%30%
2711
June1st to 15thDay
30%5%1442435%5%31%
2850
16th to endDay
26%42442345%7%33%
2877
July1st to 15thDay
9%4145%25%5%7%8%46%
2700
16th to endDay
7%313325%5%6%8%50%
2796
August1st to 15thDay
33%31331223439%
2520
16th to endDay
31%312212335%41%
2454
September1st to 15thDay
16%5%14434436%45%
2160
16th to endDay
15%413323247%50%
1992
October1st to 15thDay
19%10%25%32335%6%37%
1800
16th to endDay
14%10%35%5%25%46%6%34%
1746
November1st to 15thDay
14%11%5%5%4245%5%6%34%
1528
16th to endDay
13%11%5%9%6%45%445%28%
1524
December1st to 15thDay
7%16%6%12%11%5%6%445%19%
1117
16th to endDay
7%11%6%12%9%5%7%6%47%20%
1212
January1st to 15thNight
12%9%5%9%7%45%6%5%7%25%
2685
16th to endNight
13%12%5%9%6%46%45%6%25%
2808
February1st to 15thNight
12%10%5%9%7%34445%30%
2337
16th to endNight
11%10%5%9%6%35%45%7%30%
2040
March1st to 15thNight
26%6%26%423346%33%
2100
16th to endNight
29%7%25%4335%45%27%
2049
April1st to 15thNight
14%7%35%5%2245%7%40%
1793
16th to endNight
16%10%27%5%35%446%34%
1527
May1st to 15thNight
25%5%25%42435%6%33%
1439
16th to endNight
27%5%2442445%5%34%
1401
June1st to 15thNight
17%4245%26%5%6%8%34%
1107
16th to endNight
13%425%445%46%8%40%
1080
July1st to 15thNight
6%31443447%9%49%
1260
16th to endNight
5%2133135%5%10%57%
1371
August1st to 15thNight
19%22213346%51%
1440
16th to endNight
22%213213335%51%
1747
September1st to 15thNight
14%5%23422346%48%
1800
16th to endNight
12%413223448%52%
1967
October1st to 15thNight
17%8%25%423345%42%
2160
16th to endNight
14%10%35%5%24436%38%
2464
November1st to 15thNight
25%9%35%423336%31%
2660
16th to endNight
22%10%37%5%3434429%
2760
December1st to 15thNight
21%11%6%9%9%45%5%45%17%
2841
16th to endNight
16%10%5%9%10%5%6%5%46%19%
3009

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
59%7%15%12%5%
1253
16th to endDay
52%6%16%17%5%
1416
February1st to 15thDay
63%413%14%3
1527
16th to endDay
61%6%12%14%5%
1434
March1st to 15thDay
57%6%18%14%3
1860
16th to endDay
54%8%15%16%4
2175
April1st to 15thDay
48%8%14%19%8%
2153
16th to endDay
54%414%17%6%1
2433
May1st to 15thDay
42%5%14%27%8%1
2511
16th to endDay
50%5%13%18%11%
2715
June1st to 15thDay
48%6%15%21%7%
2850
16th to endDay
45%7%18%23%4
2877
July1st to 15thDay
32%7%20%30%7%
2541
16th to endDay
29%7%23%30%8%
2621
August1st to 15thDay
36%6%24%24%7%
2504
16th to endDay
31%5%19%31%9%1
2454
September1st to 15thDay
36%5%17%24%13%2
2160
16th to endDay
33%317%33%11%1
1992
October1st to 15thDay
46%5%17%24%6%
1800
16th to endDay
47%6%19%21%4
1746
November1st to 15thDay
49%7%19%18%6%
1528
16th to endDay
59%5%16%15%2
1524
December1st to 15thDay
68%6%14%8%1
1117
16th to endDay
62%6%15%11%2
1212
January1st to 15thNight
54%7%17%16%4
2685
16th to endNight
54%7%14%15%6%
2808
February1st to 15thNight
55%5%15%16%6%
2348
16th to endNight
53%415%18%8%
2040
March1st to 15thNight
46%6%19%20%6%
2100
16th to endNight
53%8%15%16%6%
2049
April1st to 15thNight
42%415%22%13%1
1793
16th to endNight
50%5%11%19%9%3
1527
May1st to 15thNight
41%5%11%27%13%1
1440
16th to endNight
46%6%11%17%15%1
1402
June1st to 15thNight
44%7%15%23%9%
1107
16th to endNight
39%7%18%25%7%1
1080
July1st to 15thNight
28%7%19%35%7%
1190
16th to endNight
22%6%22%36%10%1
1283
August1st to 15thNight
24%6%24%34%8%2
1432
16th to endNight
27%5%13%35%16%1
1747
September1st to 15thNight
33%413%26%16%5%
1800
16th to endNight
27%5%12%35%17%1
1967
October1st to 15thNight
42%415%27%10%
2160
16th to endNight
46%5%17%23%6%
2464
November1st to 15thNight
50%6%15%19%7%1
2660
16th to endNight
54%6%19%15%4
2760
December1st to 15thNight
64%6%16%11%1
2841
16th to endNight
58%7%14%15%4
3009

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
13%11%11%31%25%6%
60
16th to endDay
21%9%32%21%13%2
76
February1st to 15thDay
23%8%31%27%8%
90
16th to endDay
12%429%37%14%1
81
March1st to 15thDay
17%12%34%27%6%3
150
16th to endDay
17%10%27%32%10%1
288
April1st to 15thDay
13%16%31%22%13%2
269
16th to endDay
24%10%19%28%15%1
363
May1st to 15thDay
15%6%28%30%15%3
468
16th to endDay
16%8%21%26%15%10%
517
June1st to 15thDay
15%8%28%28%15%4
495
16th to endDay
19%8%20%27%20%3
495
July1st to 15thDay
9%221%33%26%6%
475
16th to endDay
9%5%23%29%25%6%
515
August1st to 15thDay
13%218%26%27%10%
493
16th to endDay
10%419%35%24%5%
339
September1st to 15thDay
17%6%26%28%17%3
315
16th to endDay
14%6%23%28%21%5%
237
October1st to 15thDay
27%429%17%16%4
135
16th to endDay
19%8%32%23%14%1
144
November1st to 15thDay
13%234%34%12%2
135
16th to endDay
15%14%23%27%13%5%
134
December1st to 15thDay
3433%36%10%12%
66
16th to endDay
20%140%26%7%3
64
January1st to 15thNight
11%9%32%33%11%1
900
16th to endNight
13%9%37%30%8%
960
February1st to 15thNight
11%6%28%35%15%2
764
16th to endNight
10%5%25%32%20%4
632
March1st to 15thNight
9%7%29%37%13%2
720
16th to endNight
18%7%26%33%12%1
705
April1st to 15thNight
12%7%30%35%12%1
539
16th to endNight
21%7%25%31%12%
540
May1st to 15thNight
16%6%24%34%16%1
540
16th to endNight
19%422%31%16%4
467
June1st to 15thNight
18%5%22%32%18%3
360
16th to endNight
15%321%36%21%1
360
July1st to 15thNight
9%316%43%24%1
340
16th to endNight
7%326%38%22%1
424
August1st to 15thNight
7%216%35%33%5%
539
16th to endNight
9%223%37%25%1
573
September1st to 15thNight
14%319%40%20%2
540
16th to endNight
11%329%37%17%
625
October1st to 15thNight
18%428%31%15%1
720
16th to endNight
15%7%31%34%10%1
894
November1st to 15thNight
18%8%30%29%10%1
950
16th to endNight
14%9%34%32%8%1
975
December1st to 15thNight
16%5%32%30%13%2
900
16th to endNight
9%7%28%35%16%3
960
Page generated at 2017-12-01 11:13:46. Version ac04

Copyright 2017 A. Danko


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