Earlton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Earlton 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
34%
23284
11%
80753
8%
23215
38%
23215
14%
60542

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
23%
938
5%
4726
5%
926
26%
926
5%
3794
January11th to 20thNight
25%
943
8%
4713
5%
930
29%
930
6%
3666
January21st to endNight
34%
880
6%
4650
8%
871
37%
871
6%
3863
February1st to 10thNight
32%
739
10%
2399
9%
739
36%
739
12%
1869
February11th to 20thNight
26%
703
10%
2275
5%
700
33%
700
13%
1731
February21st to endNight
28%
592
12%
1924
8%
592
34%
592
12%
1478
March1st to 10thNight
28%
720
13%
2019
9%
720
33%
720
15%
1556
March11th to 20thNight
28%
720
14%
1980
9%
720
33%
720
15%
1530
March21st to endNight
36%
792
18%
2178
11%
792
41%
792
22%
1549
April1st to 10thNight
31%
720
14%
1819
8%
720
34%
720
19%
1393
April11th to 20thNight
35%
561
17%
1625
11%
561
38%
561
21%
1155
April21st to endNight
37%
540
15%
1620
9%
540
43%
540
21%
1109
May1st to 10thNight
37%
432
14%
1512
15%
432
41%
432
19%
1027
May11th to 20thNight
41%
354
16%
1415
19%
354
50%
354
17%
922
May21st to endNight
45%
388
12%
1479
12%
388
53%
388
22%
913
June1st to 10thNight
43%
360
9%
1260
10%
360
46%
360
19%
852
June11th to 20thNight
46%
360
12%
1260
11%
360
48%
360
26%
748
June21st to endNight
51%
360
9%
1260
9%
360
54%
360
23%
792
July1st to 10thNight
53%
350
12%
1225
13%
350
57%
350
26%
742
July11th to 20thNight
53%
348
14%
1218
16%
348
57%
348
27%
718
July21st to endNight
57%
394
14%
1408
18%
372
59%
372
24%
856
August1st to 10thNight
55%
531
12%
1595
11%
529
60%
529
26%
1045
August11th to 20thNight
56%
534
16%
1598
12%
534
60%
534
28%
1019
August21st to endNight
46%
602
15%
1790
10%
602
49%
602
23%
1206
September1st to 10thNight
49%
720
15%
1800
8%
720
51%
720
29%
1221
September11th to 20thNight
44%
720
16%
1898
9%
720
46%
720
27%
1299
September21st to endNight
46%
720
16%
2016
12%
720
49%
720
25%
1391
October1st to 10thNight
37%
720
15%
2160
11%
720
42%
720
19%
1549
October11th to 20thNight
27%
720
9%
2160
7%
720
31%
720
12%
1715
October21st to endNight
28%
792
11%
2470
8%
792
33%
792
12%
1920
November1st to 10thNight
29%
740
12%
2592
9%
740
34%
740
13%
1934
November11th to 20thNight
21%
760
9%
2660
6%
760
26%
760
8%
2152
November21st to endNight
21%
760
5%
2660
3%
760
23%
760
7%
2246
December1st to 10thNight
20%
788
7%
2688
3%
788
25%
788
6%
2281
December11th to 20thNight
24%
950
7%
3505
4%
949
27%
949
8%
2875
December21st to endNight
20%
1033
5%
5196
4%
1026
22%
1026
4%
4426

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
16%11%5%8%7%45%5%5%7%27%
77833
Night
16%13%5%9%7%45%5%5%6%26%
81049
TransparencyDay
57%411%19%8%1
77524
Night
60%411%17%7%1
80893
SeeingDay
21%7%26%27%14%5%
14107
Night
23%6%25%33%12%1
23329

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 10thDay
14%18%9%12%8%6%7%5%5%5%13%
2208
11th to 20thDay
11%12%6%14%12%5%7%5%46%18%
2210
21st to endDay
13%19%9%13%9%45%446%15%
2994
February1st to 10thDay
7%15%8%11%10%47%5%6%7%20%
1656
11th to 20thDay
12%16%6%9%8%5%5%5%47%22%
1573
21st to endDay
10%18%7%9%8%5%6%445%24%
1332
March1st to 10thDay
13%11%5%10%9%5%6%5%46%26%
1933
11th to 20thDay
12%12%5%8%7%46%6%45%29%
1980
21st to endDay
15%11%47%7%45%5%5%5%34%
2178
April1st to 10thDay
19%12%5%8%7%3446%6%26%
2140
11th to 20thDay
20%9%47%6%335%5%6%32%
2300
21st to endDay
20%11%47%434446%33%
2340
May1st to 10thDay
17%10%36%6%35%6%5%7%31%
2448
11th to 20thDay
21%10%47%5%35%446%32%
2478
21st to endDay
17%7%37%5%345%6%7%36%
2794
June1st to 10thDay
18%8%36%6%45%5%6%8%30%
2700
11th to 20thDay
13%7%36%7%46%5%6%8%36%
2700
21st to endDay
16%8%37%6%46%5%7%7%31%
2700
July1st to 10thDay
14%6%36%5%36%5%7%10%36%
2700
11th to 20thDay
14%6%35%7%45%6%6%10%35%
2700
21st to endDay
13%6%37%7%46%6%7%9%33%
2824
August1st to 10thDay
13%6%37%7%5%6%7%6%10%30%
2330
11th to 20thDay
15%6%36%7%45%6%6%8%35%
2303
21st to endDay
15%7%37%7%45%5%6%8%32%
2548
September1st to 10thDay
17%6%35%6%46%5%5%7%36%
2160
11th to 20thDay
19%7%45%5%35%5%6%7%34%
2061
21st to endDay
21%9%37%6%25%446%32%
1944
October1st to 10thDay
20%10%47%7%35%446%31%
1800
11th to 20thDay
25%15%48%7%34445%20%
1800
21st to endDay
26%14%49%7%4445%5%17%
1884
November1st to 10thDay
21%15%5%6%7%35%5%47%22%
1486
11th to 20thDay
19%14%7%11%10%5%6%5%45%17%
1520
21st to endDay
21%19%7%12%9%35%44411%
1520
December1st to 10thDay
17%18%8%12%8%35%46%5%16%
1487
11th to 20thDay
17%17%6%10%8%45%445%20%
1671
21st to endDay
17%23%7%17%9%3433312%
2431
January1st to 10thNight
14%15%8%13%9%5%6%5%5%5%15%
4748
11th to 20thNight
10%15%6%13%11%5%7%6%5%6%17%
4760
21st to endNight
13%19%10%13%8%5%6%44414%
4660
February1st to 10thNight
11%14%6%11%10%5%7%5%6%6%19%
2399
11th to 20thNight
12%15%8%10%9%45%446%24%
2273
21st to endNight
10%16%8%12%7%5%6%45%6%22%
1924
March1st to 10thNight
12%14%8%9%8%5%6%445%26%
2009
11th to 20thNight
16%13%6%8%9%35%5%5%5%26%
1979
21st to endNight
15%12%37%435%45%6%35%
2178
April1st to 10thNight
20%14%5%7%6%3345%6%27%
1819
11th to 20thNight
18%11%38%6%35%45%5%33%
1625
21st to endNight
19%9%46%5%345%5%6%35%
1620
May1st to 10thNight
16%9%49%6%3445%5%35%
1512
11th to 20thNight
18%6%26%6%45%6%6%7%34%
1415
21st to endNight
15%6%26%6%35%45%7%41%
1478
June1st to 10thNight
17%8%36%5%35%5%7%8%32%
1260
11th to 20thNight
17%5%243345%5%9%43%
1260
21st to endNight
15%6%35%5%45%5%7%7%39%
1260
July1st to 10thNight
12%5%25%6%36%5%6%8%42%
1260
11th to 20thNight
14%6%245%25%6%5%10%41%
1260
21st to endNight
10%5%26%6%46%7%7%9%40%
1491
August1st to 10thNight
11%6%26%6%45%6%7%9%38%
1605
11th to 20thNight
14%5%25%5%35%6%6%8%41%
1598
21st to endNight
17%6%35%5%35%5%6%6%38%
1790
September1st to 10thNight
15%7%35%4345%5%7%42%
1800
11th to 20thNight
17%7%35%6%33447%40%
1898
21st to endNight
19%8%26%4345%5%7%37%
2016
October1st to 10thNight
22%9%36%5%3446%6%31%
2160
11th to 20thNight
25%12%48%7%5%5%445%22%
2160
21st to endNight
22%15%5%8%6%345%46%22%
2470
November1st to 10thNight
18%13%5%8%6%45%5%47%26%
2592
11th to 20thNight
20%13%7%11%8%45%5%4419%
2660
21st to endNight
23%17%6%10%7%35%445%14%
2660
December1st to 10thNight
18%18%8%12%8%445%45%13%
2688
11th to 20thNight
19%17%6%10%9%45%45%417%
3526
21st to endNight
21%21%7%15%7%3433413%
5236

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
74%412%9%2
2209
11th to 20thDay
69%39%16%4
2210
21st to endDay
72%39%12%4
2994
February1st to 10thDay
63%310%16%8%
1656
11th to 20thDay
62%310%16%8%1
1582
21st to endDay
63%27%20%7%
1332
March1st to 10thDay
60%49%15%11%1
1936
11th to 20thDay
56%5%8%22%9%1
1980
21st to endDay
52%47%20%14%3
2178
April1st to 10thDay
59%49%16%11%1
2140
11th to 20thDay
53%38%26%9%2
2300
21st to endDay
54%49%17%15%2
2340
May1st to 10thDay
51%5%10%20%12%2
2448
11th to 20thDay
54%47%19%14%1
2482
21st to endDay
47%5%12%22%12%1
2794
June1st to 10thDay
51%411%23%10%1
2700
11th to 20thDay
45%5%11%24%14%1
2700
21st to endDay
50%6%12%22%10%1
2700
July1st to 10thDay
41%7%15%28%9%
2626
11th to 20thDay
43%5%15%27%10%
2619
21st to endDay
47%6%16%27%4
2667
August1st to 10thDay
48%7%18%22%5%
2316
11th to 20thDay
46%7%17%22%7%1
2303
21st to endDay
50%5%14%25%6%
2548
September1st to 10thDay
47%5%16%24%8%
2160
11th to 20thDay
49%5%17%24%5%
2061
21st to endDay
54%416%21%5%
1944
October1st to 10thDay
56%5%12%19%7%1
1800
11th to 20thDay
67%410%15%4
1800
21st to endDay
69%5%10%12%5%
1884
November1st to 10thDay
63%415%13%5%
1486
11th to 20thDay
72%48%12%4
1520
21st to endDay
77%49%8%2
1520
December1st to 10thDay
71%311%11%4
1487
11th to 20thDay
66%49%18%3
1671
21st to endDay
80%29%7%2
2431
January1st to 10thNight
71%413%9%3
4748
11th to 20thNight
67%49%15%4
4760
21st to endNight
74%47%11%4
4660
February1st to 10thNight
64%48%16%8%
2399
11th to 20thNight
63%312%16%6%
2275
21st to endNight
64%38%17%9%1
1924
March1st to 10thNight
61%48%16%10%2
2019
11th to 20thNight
60%48%16%10%1
1980
21st to endNight
50%5%9%17%16%4
2178
April1st to 10thNight
58%37%18%13%1
1819
11th to 20thNight
53%37%20%15%2
1625
21st to endNight
49%411%15%18%2
1620
May1st to 10thNight
51%49%21%13%3
1512
11th to 20thNight
48%5%8%22%14%2
1416
21st to endNight
43%5%13%19%17%3
1479
June1st to 10thNight
49%6%10%23%11%2
1260
11th to 20thNight
38%5%13%27%15%2
1260
21st to endNight
42%6%14%23%13%2
1260
July1st to 10thNight
37%8%15%26%14%
1225
11th to 20thNight
38%5%16%28%13%
1218
21st to endNight
40%6%18%31%6%
1408
August1st to 10thNight
41%7%19%27%6%
1595
11th to 20thNight
38%8%18%28%8%1
1598
21st to endNight
46%5%17%23%9%1
1790
September1st to 10thNight
42%6%18%24%9%2
1800
11th to 20thNight
45%5%18%26%7%
1898
21st to endNight
46%5%16%26%7%
2016
October1st to 10thNight
53%414%19%10%
2160
11th to 20thNight
66%311%17%3
2160
21st to endNight
63%411%15%6%
2470
November1st to 10thNight
59%5%14%17%4
2592
11th to 20thNight
69%411%12%4
2660
21st to endNight
75%411%9%2
2660
December1st to 10thNight
74%5%7%11%3
2688
11th to 20thNight
71%47%14%4
3525
21st to endNight
78%37%10%3
5236

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
24%10%23%28%9%4
180
11th to 20thDay
19%7%28%30%10%5%
180
21st to endDay
18%429%33%13%3
286
February1st to 10thDay
18%13%32%27%9%1
252
11th to 20thDay
22%8%35%24%8%3
240
21st to endDay
23%12%41%20%5%
198
March1st to 10thDay
17%7%35%31%9%1
380
11th to 20thDay
18%11%29%31%9%2
420
21st to endDay
23%8%29%28%10%2
462
April1st to 10thDay
23%8%27%27%13%3
420
11th to 20thDay
26%9%22%26%13%4
412
21st to endDay
27%11%24%21%12%5%
420
May1st to 10thDay
24%5%25%27%14%5%
423
11th to 20thDay
22%6%27%25%14%6%
447
21st to endDay
19%6%32%25%16%3
554
June1st to 10thDay
21%6%28%30%12%3
630
11th to 20thDay
16%8%29%28%16%3
630
21st to endDay
18%6%19%32%20%6%
630
July1st to 10thDay
14%5%26%32%18%5%
621
11th to 20thDay
16%5%23%31%17%8%
618
21st to endDay
14%421%31%22%8%
568
August1st to 10thDay
15%421%25%24%10%
446
11th to 20thDay
16%315%28%25%14%
439
21st to endDay
18%5%23%26%16%13%
495
September1st to 10thDay
17%423%28%18%10%
450
11th to 20thDay
21%6%20%32%16%6%
450
21st to endDay
25%7%20%23%18%7%
450
October1st to 10thDay
28%6%22%26%13%5%
450
11th to 20thDay
31%9%27%22%9%1
450
21st to endDay
32%10%27%24%6%2
408
November1st to 10thDay
33%10%32%21%32
180
11th to 20thDay
23%13%27%26%10%2
180
21st to endDay
34%9%32%16%6%2
180
December1st to 10thDay
24%12%27%23%13%2
180
11th to 20thDay
23%13%32%19%9%3
180
21st to endDay
23%7%29%26%10%4
198
January1st to 10thNight
25%5%27%32%10%1
950
11th to 20thNight
25%6%26%32%10%1
950
21st to endNight
20%422%37%16%2
893
February1st to 10thNight
18%7%28%37%9%1
739
11th to 20thNight
19%6%31%34%9%1
703
21st to endNight
20%6%32%32%10%
592
March1st to 10thNight
18%8%33%31%9%1
720
11th to 20thNight
22%9%28%33%8%
720
21st to endNight
20%8%28%36%9%1
792
April1st to 10thNight
26%9%23%34%7%1
720
11th to 20thNight
23%6%29%30%12%1
561
21st to endNight
25%427%33%10%1
540
May1st to 10thNight
21%426%39%10%
432
11th to 20thNight
20%6%25%38%10%1
354
21st to endNight
19%5%25%41%11%
389
June1st to 10thNight
21%5%25%40%9%
360
11th to 20thNight
19%425%36%15%
360
21st to endNight
16%321%43%16%1
360
July1st to 10thNight
15%223%48%12%
350
11th to 20thNight
16%320%44%18%
348
21st to endNight
13%319%46%19%1
394
August1st to 10thNight
14%219%40%23%2
531
11th to 20thNight
15%216%40%24%3
534
21st to endNight
21%420%33%20%2
602
September1st to 10thNight
18%421%37%19%2
720
11th to 20thNight
20%421%33%20%1
720
21st to endNight
22%5%21%33%17%2
720
October1st to 10thNight
27%423%33%12%2
720
11th to 20thNight
32%7%26%25%10%2
720
21st to endNight
29%6%26%31%7%1
792
November1st to 10thNight
24%7%30%30%7%1
740
11th to 20thNight
28%8%29%25%9%1
760
21st to endNight
33%7%24%29%6%
760
December1st to 10thNight
29%6%27%27%9%2
788
11th to 20thNight
28%6%26%30%8%1
950
21st to endNight
29%8%25%26%10%2
1045
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