Seward
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seward clear sky chart from 2005-11-06 to 2024-03-01.

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
41%
24641
26%
79788
15%
24537
52%
24537
35%
43948

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
34%
941
27%
4053
11%
926
48%
926
22%
2406
January11th to 20thNight
35%
948
30%
4011
12%
930
47%
930
27%
2008
January21st to endNight
31%
1041
21%
4364
12%
1023
44%
1023
24%
2561
February1st to 10thNight
29%
875
23%
2395
8%
875
40%
875
31%
1517
February11th to 20thNight
30%
743
25%
2218
11%
740
42%
740
32%
1289
February21st to endNight
28%
628
31%
1884
10%
628
44%
628
37%
1015
March1st to 10thNight
30%
672
28%
2116
11%
672
45%
672
35%
1138
March11th to 20thNight
34%
540
24%
1980
16%
540
44%
540
29%
1065
March21st to endNight
25%
594
20%
2178
10%
594
40%
594
21%
1306
April1st to 10thNight
30%
540
24%
1915
13%
540
47%
540
32%
983
April11th to 20thNight
28%
533
24%
1712
11%
533
45%
533
28%
972
April21st to endNight
32%
540
24%
1620
14%
540
47%
540
30%
961
May1st to 10thNight
31%
540
20%
1620
13%
540
43%
540
27%
1028
May11th to 20thNight
41%
531
21%
1593
17%
531
51%
531
34%
912
May21st to endNight
43%
582
16%
1745
9%
582
51%
582
30%
1050
June1st to 10thNight
53%
540
21%
1620
14%
540
60%
540
45%
832
June11th to 20thNight
45%
540
22%
1620
10%
540
55%
540
43%
861
June21st to endNight
51%
540
24%
1620
14%
540
60%
540
46%
825
July1st to 10thNight
63%
525
20%
1575
15%
525
66%
525
41%
860
July11th to 20thNight
64%
522
25%
1566
20%
522
70%
522
55%
750
July21st to endNight
64%
591
23%
1673
20%
558
70%
558
39%
944
August1st to 10thNight
67%
537
24%
1601
23%
534
72%
534
41%
864
August11th to 20thNight
64%
534
28%
1600
28%
534
70%
534
40%
884
August21st to endNight
66%
594
30%
1934
30%
594
73%
594
47%
948
September1st to 10thNight
57%
540
26%
1934
25%
540
66%
540
38%
967
September11th to 20thNight
49%
540
30%
1980
24%
540
61%
540
37%
999
September21st to endNight
51%
540
31%
1980
26%
540
61%
540
39%
952
October1st to 10thNight
46%
540
33%
1980
26%
540
55%
540
35%
973
October11th to 20thNight
38%
693
35%
2133
15%
693
53%
693
48%
1019
October21st to endNight
41%
854
31%
2438
15%
854
52%
854
43%
1309
November1st to 10thNight
44%
925
33%
2405
13%
925
55%
925
51%
1268
November11th to 20thNight
37%
950
35%
2470
13%
950
51%
950
49%
1324
November21st to endNight
41%
950
31%
2470
14%
950
51%
950
41%
1427
December1st to 10thNight
40%
950
30%
2470
14%
950
51%
950
42%
1430
December11th to 20thNight
31%
950
32%
2872
11%
948
45%
948
34%
1606
December21st to endNight
32%
1038
21%
4443
13%
1026
46%
1026
22%
2695

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%6%2443445%7%53%
78886
Night
8%5%2442445%7%55%
80581
TransparencyDay
30%5%12%27%20%5%
78614
Night
29%5%12%26%22%6%
80376
SeeingDay
11%9%31%31%15%3
14562
Night
10%9%36%35%10%1
24666

By Month

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 10thDay
7%7%37%5%345%5%7%47%
2847
11th to 20thDay
7%8%36%6%45%5%5%7%44%
2850
21st to endDay
9%10%46%423336%51%
3135
February1st to 10thDay
7%10%37%5%3335%7%47%
1800
11th to 20thDay
5%5%35%4345%5%7%53%
1849
21st to endDay
6%6%2442345%8%56%
1570
March1st to 10thDay
7%6%244245%6%7%54%
1849
11th to 20thDay
12%8%34323346%50%
1980
21st to endDay
13%8%34424447%47%
2178
April1st to 10thDay
10%424424447%55%
2042
11th to 20thDay
11%7%36%5%3446%6%47%
2196
21st to endDay
14%6%35%5%3445%7%45%
2340
May1st to 10thDay
12%6%35%42446%6%48%
2340
11th to 20thDay
11%6%2442446%7%51%
2302
21st to endDay
10%425%5%45%5%7%10%42%
2531
June1st to 10thDay
4324325%45%8%59%
2340
11th to 20thDay
5%314425%5%5%7%58%
2340
21st to endDay
6%213425%5%5%9%59%
2340
July1st to 10thDay
5%5%24445%5%6%8%52%
2340
11th to 20thDay
3213435%5%6%10%58%
2340
21st to endDay
6%4245%36%6%7%9%47%
2546
August1st to 10thDay
6%4144346%7%10%49%
2328
11th to 20thDay
7%424435%47%8%53%
2301
21st to endDay
5%3144245%5%8%59%
2417
September1st to 10thDay
9%423434446%58%
2026
11th to 20thDay
8%424423446%59%
1980
21st to endDay
7%424423446%60%
1980
October1st to 10thDay
12%5%14323336%58%
1980
11th to 20thDay
8%323322246%65%
1807
21st to endDay
10%7%13322335%60%
1913
November1st to 10thDay
6%412323446%66%
1673
11th to 20thDay
6%41442335%6%62%
1710
21st to endDay
10%6%2321333463%
1710
December1st to 10thDay
7%5%25%4245%5%8%54%
1710
11th to 20thDay
7%7%35%423447%55%
2161
21st to endDay
7%12%5%7%5%3445%7%40%
3135
January1st to 10thNight
7%8%39%6%34445%47%
4108
11th to 20thNight
5%5%25%5%44446%57%
4120
21st to endNight
12%9%36%42333451%
4532
February1st to 10thNight
9%7%46%5%34445%50%
2395
11th to 20thNight
7%6%35%5%3445%7%51%
2218
21st to endNight
7%5%35%323346%58%
1884
March1st to 10thNight
8%5%2442445%7%56%
2116
11th to 20thNight
11%6%2442335%6%53%
1980
21st to endNight
13%8%34434447%45%
2178
April1st to 10thNight
8%41442345%9%55%
1915
11th to 20thNight
11%5%35%425%45%7%50%
1712
21st to endNight
13%6%2442335%6%51%
1620
May1st to 10thNight
12%6%35%4345%6%7%44%
1620
11th to 20thNight
11%4243235%5%8%52%
1593
21st to endNight
10%415%435%6%7%10%45%
1745
June1st to 10thNight
6%21242438%10%59%
1620
11th to 20thNight
5%213335%47%10%56%
1620
21st to endNight
431442447%9%60%
1620
July1st to 10thNight
6%323435%46%10%54%
1620
11th to 20thNight
322232337%11%61%
1620
21st to endNight
7%324435%5%7%11%51%
1772
August1st to 10thNight
43145%345%7%10%53%
1611
11th to 20thNight
7%5%2333447%10%53%
1600
21st to endNight
3324424447%64%
1934
September1st to 10thNight
9%323423347%60%
1934
11th to 20thNight
7%425%324347%59%
1980
21st to endNight
6%41432445%6%62%
1980
October1st to 10thNight
10%414323346%59%
1980
11th to 20thNight
8%312212335%69%
2133
21st to endNight
9%5%23323345%62%
2438
November1st to 10thNight
6%423312345%68%
2405
11th to 20thNight
6%413323446%64%
2470
21st to endNight
9%5%23323446%58%
2470
December1st to 10thNight
6%5%25%423446%58%
2470
11th to 20thNight
8%5%2443435%6%57%
3036
21st to endNight
11%10%46%43335%6%44%
4532

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
35%6%11%27%18%2
2848
11th to 20thDay
38%7%14%23%13%5%
2850
21st to endDay
37%312%28%16%3
3135
February1st to 10thDay
38%414%24%14%7%
1800
11th to 20thDay
30%5%15%26%17%8%
1859
21st to endDay
27%311%27%22%9%
1570
March1st to 10thDay
28%412%24%23%8%
1849
11th to 20thDay
36%49%21%24%6%
1980
21st to endDay
37%6%12%28%13%4
2178
April1st to 10thDay
30%5%11%25%21%7%
2042
11th to 20thDay
36%6%10%27%16%5%
2199
21st to endDay
39%5%10%28%17%2
2340
May1st to 10thDay
36%7%12%21%19%4
2340
11th to 20thDay
32%7%15%32%13%1
2306
21st to endDay
36%8%17%26%11%3
2531
June1st to 10thDay
24%6%18%32%15%5%
2340
11th to 20thDay
25%6%13%28%22%6%
2340
21st to endDay
22%7%11%27%26%7%
2340
July1st to 10thDay
29%7%12%27%22%3
2276
11th to 20thDay
20%7%13%28%24%7%
2271
21st to endDay
29%8%13%28%20%2
2405
August1st to 10thDay
27%8%18%27%15%4
2314
11th to 20thDay
28%6%12%28%19%6%
2301
21st to endDay
23%6%10%28%24%10%
2417
September1st to 10thDay
28%5%8%26%22%11%
2026
11th to 20thDay
27%5%9%27%28%5%
1980
21st to endDay
26%5%10%26%26%8%
1980
October1st to 10thDay
28%5%9%25%26%6%
1980
11th to 20thDay
23%38%26%29%11%
1807
21st to endDay
28%39%26%25%10%
1913
November1st to 10thDay
21%49%29%29%8%
1673
11th to 20thDay
24%310%28%28%8%
1710
21st to endDay
27%36%28%29%7%
1710
December1st to 10thDay
28%6%12%29%22%4
1710
11th to 20thDay
30%49%31%23%3
2159
21st to endDay
42%6%9%24%16%3
3135
January1st to 10thNight
38%6%9%28%16%3
4108
11th to 20thNight
28%5%14%27%21%5%
4120
21st to endNight
38%411%25%20%3
4532
February1st to 10thNight
38%412%23%16%7%
2395
11th to 20thNight
33%5%11%25%20%6%
2218
21st to endNight
28%38%22%26%13%
1884
March1st to 10thNight
28%410%23%25%10%
2116
11th to 20thNight
32%411%24%21%8%
1980
21st to endNight
39%6%12%24%16%3
2178
April1st to 10thNight
27%5%12%23%27%6%
1915
11th to 20thNight
33%5%14%26%18%4
1712
21st to endNight
33%5%13%23%21%4
1620
May1st to 10thNight
38%6%12%20%18%5%
1620
11th to 20thNight
29%7%17%28%16%2
1594
21st to endNight
31%8%21%27%10%3
1746
June1st to 10thNight
20%6%20%31%18%4
1620
11th to 20thNight
23%6%15%29%22%5%
1620
21st to endNight
20%7%13%28%24%8%
1620
July1st to 10thNight
25%7%14%28%21%5%
1575
11th to 20thNight
15%6%16%28%28%7%
1566
21st to endNight
27%8%13%29%21%2
1673
August1st to 10thNight
24%8%17%33%14%4
1601
11th to 20thNight
27%6%13%30%20%4
1600
21st to endNight
21%5%11%29%25%9%
1934
September1st to 10thNight
26%5%10%23%25%11%
1934
11th to 20thNight
26%5%9%23%30%7%
1980
21st to endNight
23%5%10%24%29%9%
1980
October1st to 10thNight
27%411%22%29%8%
1980
11th to 20thNight
19%49%24%32%13%
2133
21st to endNight
26%39%23%27%12%
2438
November1st to 10thNight
20%39%27%28%12%
2405
11th to 20thNight
22%38%29%30%9%
2470
21st to endNight
27%47%26%25%10%
2470
December1st to 10thNight
27%412%29%22%6%
2470
11th to 20thNight
29%38%35%20%4
3037
21st to endNight
39%5%11%27%14%4
4532

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%11%41%27%11%1
270
11th to 20thDay
14%15%43%22%6%1
270
21st to endDay
9%12%49%24%5%
297
February1st to 10thDay
14%18%43%21%31
270
11th to 20thDay
11%14%45%23%7%1
270
21st to endDay
12%16%49%19%4
225
March1st to 10thDay
9%16%48%21%6%
240
11th to 20thDay
18%16%38%19%8%1
240
21st to endDay
19%16%42%18%31
264
April1st to 10thDay
12%17%38%28%41
302
11th to 20thDay
14%18%40%24%3
477
21st to endDay
18%16%38%19%8%2
600
May1st to 10thDay
14%9%36%31%9%1
603
11th to 20thDay
17%8%32%26%15%3
625
21st to endDay
14%8%34%29%12%3
679
June1st to 10thDay
5%428%36%19%9%
630
11th to 20thDay
5%7%31%37%17%2
630
21st to endDay
5%6%30%43%15%2
630
July1st to 10thDay
7%216%40%27%7%
621
11th to 20thDay
5%215%45%28%6%
618
21st to endDay
7%211%43%29%7%
684
August1st to 10thDay
8%217%42%25%6%
626
11th to 20thDay
7%316%44%27%4
615
21st to endDay
7%319%40%25%6%
536
September1st to 10thDay
12%317%36%27%4
316
11th to 20thDay
4324%41%19%10%
270
21st to endDay
12%5%31%27%20%4
270
October1st to 10thDay
16%8%30%23%16%6%
270
11th to 20thDay
7%10%41%27%12%3
270
21st to endDay
18%13%34%20%13%1
297
November1st to 10thDay
11%13%33%29%12%3
270
11th to 20thDay
12%11%40%26%10%1
270
21st to endDay
16%11%33%26%10%3
270
December1st to 10thDay
9%11%36%30%12%3
270
11th to 20thDay
12%11%41%28%7%
270
21st to endDay
16%15%44%22%3
297
January1st to 10thNight
9%10%39%35%6%
950
11th to 20thNight
9%12%39%32%7%1
950
21st to endNight
9%10%45%31%5%
1045
February1st to 10thNight
13%10%42%30%4
875
11th to 20thNight
11%11%44%31%3
744
21st to endNight
10%14%44%28%4
628
March1st to 10thNight
9%15%42%29%4
672
11th to 20thNight
15%11%37%29%8%
540
21st to endNight
18%13%40%24%41
594
April1st to 10thNight
13%13%43%26%5%
540
11th to 20thNight
13%14%41%27%5%
533
21st to endNight
18%12%37%26%7%
540
May1st to 10thNight
15%10%40%30%5%
540
11th to 20thNight
13%8%33%33%12%1
531
21st to endNight
11%9%32%33%13%1
584
June1st to 10thNight
6%6%30%40%16%1
540
11th to 20thNight
47%40%39%10%
540
21st to endNight
5%334%46%11%1
540
July1st to 10thNight
6%221%49%20%2
525
11th to 20thNight
3127%48%21%1
522
21st to endNight
8%121%47%21%1
591
August1st to 10thNight
4219%54%20%1
537
11th to 20thNight
9%220%50%19%
534
21st to endNight
4222%48%23%1
594
September1st to 10thNight
10%324%44%16%1
540
11th to 20thNight
9%333%39%15%1
540
21st to endNight
7%6%33%39%14%1
540
October1st to 10thNight
11%6%33%35%14%1
540
11th to 20thNight
10%9%40%33%8%
693
21st to endNight
12%8%35%31%11%1
854
November1st to 10thNight
8%9%36%36%11%1
925
11th to 20thNight
8%10%43%31%8%
950
21st to endNight
12%9%33%34%11%1
950
December1st to 10thNight
9%10%39%36%7%
950
11th to 20thNight
13%12%40%31%5%
950
21st to endNight
13%12%38%31%5%
1045
Page generated at 2024-02-27 05:30:12. Version ac07

Copyright © 2024 Attilla Danko.


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