Dorset Wilderness Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dorset Wilderness Area clear sky chart from 2005-11-05 to 2019-06-10.

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
30%
17315
13%
53962
9%
17273
35%
17273
15%
39590

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
9%
838
7%
2738
3%
836
13%
836
5%
2348
January16th to endNight
9%
896
6%
2912
2%
896
14%
896
6%
2469
February1st to 15thNight
12%
824
6%
2677
3%
821
16%
821
6%
2265
February16th to endNight
14%
735
8%
2281
2%
735
20%
735
8%
1856
March1st to 15thNight
18%
840
14%
2320
7%
840
24%
840
12%
1839
March16th to endNight
26%
896
17%
2464
10%
896
32%
896
18%
1796
April1st to 15thNight
23%
838
12%
2174
5%
838
28%
838
17%
1638
April16th to endNight
32%
628
18%
1874
9%
628
40%
628
22%
1276
May1st to 15thNight
37%
630
14%
1890
9%
630
42%
630
19%
1333
May16th to endNight
41%
526
14%
1840
12%
525
47%
525
24%
1121
June1st to 15thNight
47%
408
17%
1632
17%
408
57%
408
22%
966
June16th to endNight
51%
390
15%
1560
18%
390
57%
390
23%
925
July1st to 15thNight
58%
452
18%
1562
21%
452
62%
452
30%
895
July16th to endNight
60%
612
16%
1739
15%
579
62%
579
32%
1037
August1st to 15thNight
64%
575
19%
1715
15%
572
66%
572
32%
1036
August16th to endNight
58%
662
21%
1904
14%
662
61%
662
32%
1165
September1st to 15thNight
54%
780
21%
2031
15%
780
56%
780
31%
1332
September16th to endNight
49%
777
22%
2145
15%
777
54%
777
28%
1391
October1st to 15thNight
40%
780
17%
2327
15%
780
45%
780
23%
1549
October16th to endNight
20%
832
14%
2496
7%
832
29%
832
14%
1883
November1st to 15thNight
29%
820
16%
2665
12%
820
36%
820
16%
1921
November16th to endNight
15%
840
9%
2940
6%
840
20%
840
7%
2359
December1st to 15thNight
12%
840
6%
2940
4%
840
16%
840
6%
2455
December16th to endNight
8%
896
4%
3136
1%
896
12%
896
4%
2735

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
17%11%47%6%34446%28%
54527
Night
17%11%47%6%34446%29%
54151
Cloud CoverDay
17%11%47%6%34446%29%
54537
Night
17%11%47%6%34446%29%
54155
TransparencyDay
55%410%18%9%1
54235
Night
55%410%17%9%1
53962
SeeingDay
25%14%26%19%10%4
7519
Night
24%13%25%23%11%1
17318

By Month

Percentage Cloud Cover NE (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
20%17%7%12%8%3433413%
1856
16th to endDay
15%20%7%14%10%3433312%
2016
February1st to 15thDay
17%20%9%11%10%2332313%
1845
16th to endDay
18%16%7%12%7%2434419%
1760
March1st to 15thDay
18%17%7%9%5%23345%22%
2288
16th to endDay
19%12%5%7%5%23345%29%
2464
April1st to 15thDay
23%12%35%433446%27%
2440
16th to endDay
21%10%35%42234436%
2695
May1st to 15thDay
18%9%36%6%345%5%6%29%
2721
16th to endDay
13%6%25%5%35%46%7%37%
2976
June1st to 15thDay
15%6%36%5%25%5%5%7%35%
2856
16th to endDay
16%425%4345%6%10%35%
2730
July1st to 15thDay
10%5%25%5%35%5%6%8%41%
2639
16th to endDay
12%5%25%5%45%6%5%9%37%
2673
August1st to 15thDay
10%7%25%6%36%6%6%8%35%
2487
16th to endDay
11%6%25%6%45%5%6%8%37%
2636
September1st to 15thDay
17%7%26%6%36%45%7%32%
2257
16th to endDay
17%6%36%42435%7%37%
2145
October1st to 15thDay
22%6%26%6%345%45%33%
1963
16th to endDay
29%10%26%5%24445%24%
2080
November1st to 15thDay
16%14%46%5%34446%29%
1848
16th to endDay
20%24%47%5%24335%18%
1680
December1st to 15thDay
19%21%9%12%6%3332313%
1680
16th to endDay
21%24%9%13%6%332228%
1792
January1st to 15thNight
22%17%8%12%6%3322315%
2738
16th to endNight
17%19%8%11%9%3433414%
2912
February1st to 15thNight
19%17%6%12%9%35%33316%
2675
16th to endNight
18%14%8%12%6%2444419%
2281
March1st to 15thNight
17%13%5%10%7%2435%424%
2308
16th to endNight
17%10%5%6%5%24345%33%
2464
April1st to 15thNight
20%12%36%5%33446%28%
2174
16th to endNight
13%9%346%345%5%6%37%
1874
May1st to 15thNight
17%8%35%5%44448%32%
1890
16th to endNight
13%6%25%43345%10%39%
1838
June1st to 15thNight
8%5%26%5%35%6%5%7%42%
1632
16th to endNight
10%5%25%5%45%5%5%8%42%
1560
July1st to 15thNight
7%4246%35%448%48%
1648
16th to endNight
7%425%5%25%45%9%46%
1847
August1st to 15thNight
7%325%4445%6%9%45%
1726
16th to endNight
10%4244345%6%7%45%
1904
September1st to 15thNight
15%5%24323447%44%
2031
16th to endNight
16%4245%3445%7%42%
2145
October1st to 15thNight
17%7%25%32445%7%38%
2327
16th to endNight
26%9%26%434446%27%
2496
November1st to 15thNight
18%10%36%5%34446%30%
2665
16th to endNight
22%19%48%5%34345%19%
2940
December1st to 15thNight
21%20%8%8%5%3433416%
2940
16th to endNight
23%20%8%9%7%33435%11%
3136

Percentage Cloud Cover SE (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
19%18%7%12%8%3433413%
1856
16th to endDay
15%20%8%14%10%3433411%
2016
February1st to 15thDay
17%20%9%12%10%3232313%
1845
16th to endDay
18%16%7%12%7%2443418%
1760
March1st to 15thDay
19%17%7%9%5%22245%22%
2299
16th to endDay
19%12%6%6%423345%29%
2463
April1st to 15thDay
23%12%445%33446%27%
2440
16th to endDay
21%10%25%422345%36%
2695
May1st to 15thDay
19%9%36%5%45%5%5%6%29%
2721
16th to endDay
13%6%25%5%35%46%7%37%
2976
June1st to 15thDay
15%6%26%425%5%5%7%36%
2856
16th to endDay
15%5%25%4345%5%11%35%
2730
July1st to 15thDay
10%5%25%5%35%5%5%8%41%
2639
16th to endDay
13%5%25%5%45%5%6%8%37%
2673
August1st to 15thDay
10%6%25%6%36%5%7%8%35%
2487
16th to endDay
12%6%25%6%35%5%6%7%38%
2636
September1st to 15thDay
17%7%36%6%35%45%8%32%
2257
16th to endDay
17%6%36%5%24447%37%
2145
October1st to 15thDay
22%6%26%6%335%45%32%
1963
16th to endDay
29%10%26%423445%24%
2080
November1st to 15thDay
16%14%46%5%34446%28%
1848
16th to endDay
20%23%47%5%24335%18%
1680
December1st to 15thDay
19%23%9%11%6%3332313%
1680
16th to endDay
21%25%9%13%6%332228%
1792
January1st to 15thNight
21%18%8%12%7%2332215%
2738
16th to endNight
16%20%8%11%9%4333414%
2912
February1st to 15thNight
18%17%6%12%8%35%33316%
2668
16th to endNight
18%14%7%12%6%2444419%
2281
March1st to 15thNight
16%13%6%9%7%24445%24%
2320
16th to endNight
17%10%5%6%5%24345%33%
2464
April1st to 15thNight
20%12%35%5%3445%6%28%
2174
16th to endNight
13%8%35%6%345%5%6%37%
1874
May1st to 15thNight
17%8%46%5%35%348%32%
1889
16th to endNight
13%6%25%5%333411%39%
1838
June1st to 15thNight
9%5%26%5%346%6%7%41%
1632
16th to endNight
11%5%25%5%25%5%5%8%42%
1560
July1st to 15thNight
7%4246%4445%8%48%
1648
16th to endNight
7%425%425%5%6%9%45%
1847
August1st to 15thNight
7%415%5%25%5%6%9%45%
1726
16th to endNight
10%425%42446%7%45%
1904
September1st to 15thNight
16%5%2342435%6%44%
2031
16th to endNight
15%425%5%34447%42%
2145
October1st to 15thNight
18%7%25%42435%7%38%
2327
16th to endNight
26%8%36%5%24445%27%
2496
November1st to 15thNight
18%11%36%5%24446%30%
2665
16th to endNight
21%19%5%8%5%34335%19%
2940
December1st to 15thNight
21%20%9%8%5%3433415%
2940
16th to endNight
22%22%8%9%7%3343410%
3136

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
74%38%9%3
1857
16th to endDay
78%38%8%1
2016
February1st to 15thDay
77%36%10%3
1847
16th to endDay
68%39%12%4
1760
March1st to 15thDay
64%410%15%5%
2299
16th to endDay
56%37%20%9%1
2464
April1st to 15thDay
57%311%16%10%
2440
16th to endDay
50%39%18%12%3
2695
May1st to 15thDay
53%5%10%20%9%1
2721
16th to endDay
43%5%14%23%10%2
2980
June1st to 15thDay
45%5%12%24%11%
2856
16th to endDay
42%5%13%22%14%
2730
July1st to 15thDay
39%5%10%24%17%2
2497
16th to endDay
42%5%12%23%13%1
2518
August1st to 15thDay
43%6%14%24%11%
2474
16th to endDay
42%5%12%24%13%2
2636
September1st to 15thDay
49%5%12%20%10%1
2257
16th to endDay
46%411%22%14%1
2145
October1st to 15thDay
51%413%18%11%
1963
16th to endDay
61%313%15%5%
2080
November1st to 15thDay
56%49%16%9%2
1848
16th to endDay
69%39%10%6%
1680
December1st to 15thDay
77%46%9%2
1680
16th to endDay
83%36%5%1
1792
January1st to 15thNight
75%36%9%4
2738
16th to endNight
74%38%10%2
2912
February1st to 15thNight
73%48%10%3
2677
16th to endNight
68%38%13%4
2281
March1st to 15thNight
62%47%16%8%
2320
16th to endNight
53%37%20%12%1
2464
April1st to 15thNight
55%411%17%10%
2174
16th to endNight
46%49%20%14%4
1874
May1st to 15thNight
50%5%11%19%10%2
1890
16th to endNight
40%415%22%13%2
1840
June1st to 15thNight
39%6%10%27%15%
1632
16th to endNight
38%6%13%21%16%2
1560
July1st to 15thNight
34%5%8%25%22%3
1562
16th to endNight
33%6%13%23%18%3
1739
August1st to 15thNight
33%6%12%30%13%2
1715
16th to endNight
35%5%12%27%16%2
1904
September1st to 15thNight
38%5%13%23%16%2
2031
16th to endNight
40%411%24%17%1
2145
October1st to 15thNight
45%412%20%16%
2327
16th to endNight
57%5%11%17%8%
2496
November1st to 15thNight
54%5%11%16%8%4
2665
16th to endNight
68%48%13%4
2940
December1st to 15thNight
73%39%9%3
2940
16th to endNight
77%48%8%
3136

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
31%30%23%9%31
173
16th to endDay
32%33%27%5%1
192
February1st to 15thDay
40%22%35%2
180
16th to endDay
37%25%32%5%
159
March1st to 15thDay
30%21%30%14%3
379
16th to endDay
29%20%27%16%4
416
April1st to 15thDay
35%22%22%12%6%
390
16th to endDay
27%16%27%13%9%3
379
May1st to 15thDay
30%14%25%21%6%2
408
16th to endDay
17%12%30%24%10%5%
459
June1st to 15thDay
20%10%31%23%11%2
411
16th to endDay
19%9%28%27%12%3
375
July1st to 15thDay
13%6%22%29%19%9%
365
16th to endDay
13%5%27%28%15%9%
390
August1st to 15thDay
17%421%27%18%10%
358
16th to endDay
15%6%23%24%17%12%
396
September1st to 15thDay
18%417%24%22%12%
375
16th to endDay
18%7%22%18%21%10%
374
October1st to 15thDay
24%7%27%22%17%1
375
16th to endDay
35%17%28%13%4
400
November1st to 15thDay
40%14%18%17%7%1
197
16th to endDay
32%21%33%11%
120
December1st to 15thDay
34%23%30%7%4
120
16th to endDay
39%28%25%6%
128
January1st to 15thNight
32%22%30%12%2
840
16th to endNight
31%21%31%13%1
896
February1st to 15thNight
32%21%27%16%2
824
16th to endNight
30%19%29%18%2
735
March1st to 15thNight
26%18%32%19%3
840
16th to endNight
24%15%28%23%6%
896
April1st to 15thNight
28%14%30%21%5%
838
16th to endNight
19%10%31%28%9%1
628
May1st to 15thNight
22%7%24%33%11%
630
16th to endNight
15%6%28%27%18%2
527
June1st to 15thNight
10%429%39%15%
408
16th to endNight
12%5%23%41%16%
390
July1st to 15thNight
8%320%38%24%4
452
16th to endNight
9%416%40%27%2
612
August1st to 15thNight
10%215%39%26%5%
575
16th to endNight
13%318%28%32%3
662
September1st to 15thNight
18%415%31%25%4
780
16th to endNight
18%6%19%25%22%6%
777
October1st to 15thNight
23%7%24%27%15%1
780
16th to endNight
33%14%28%19%4
832
November1st to 15thNight
26%14%25%22%10%1
820
16th to endNight
36%19%25%13%5%
840
December1st to 15thNight
35%21%25%13%4
840
16th to endNight
34%23%27%12%2
896
Page generated at 2019-06-10 19:29:50. Version ac04

Copyright 2019 A. Danko


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