Thetford Mines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Thetford Mines clear sky chart from 2005-11-06 to 2025-01-22.

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
24%
23952
10%
106201
6%
23636
30%
23636
9%
79431

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
8%
798
5%
4543
2%
777
14%
777
2%
3806
January11th to 20thNight
10%
799
6%
4566
2%
780
16%
780
3%
3835
January21st to endNight
15%
837
6%
4865
3%
819
22%
819
4%
3849
February1st to 10thNight
14%
760
10%
2632
3%
760
23%
760
8%
2077
February11th to 20thNight
10%
743
8%
2220
1%
740
19%
740
7%
1830
February21st to endNight
17%
628
13%
1884
5%
628
27%
628
12%
1446
March1st to 10thNight
15%
752
14%
3717
5%
743
24%
743
7%
2698
March11th to 20thNight
17%
751
10%
3639
4%
740
26%
740
6%
2863
March21st to endNight
24%
834
11%
3505
6%
814
32%
814
10%
2617
April1st to 10thNight
21%
760
14%
1900
5%
760
26%
760
15%
1465
April11th to 20thNight
23%
672
15%
1796
5%
672
30%
672
19%
1304
April21st to endNight
22%
570
13%
1710
6%
570
28%
570
14%
1262
May1st to 10thNight
23%
560
12%
2790
7%
556
32%
556
10%
1975
May11th to 20thNight
29%
370
14%
2480
15%
364
41%
364
8%
1612
May21st to endNight
28%
408
9%
2722
10%
399
38%
399
10%
1588
June1st to 10thNight
31%
380
9%
1397
8%
380
37%
380
15%
997
June11th to 20thNight
39%
380
13%
1330
12%
380
45%
380
19%
871
June21st to endNight
33%
380
8%
1393
7%
380
38%
380
14%
1003
July1st to 10thNight
39%
364
8%
2414
11%
360
46%
360
10%
1592
July11th to 20thNight
42%
364
8%
2358
15%
358
48%
358
10%
1540
July21st to endNight
42%
409
8%
2432
14%
383
45%
383
11%
1476
August1st to 10thNight
50%
385
11%
2410
13%
377
55%
377
11%
1630
August11th to 20thNight
43%
556
8%
2715
8%
551
47%
551
11%
2005
August21st to endNight
40%
746
15%
3132
8%
738
45%
738
15%
2127
September1st to 10thNight
39%
760
13%
1900
5%
760
42%
760
26%
1339
September11th to 20thNight
45%
760
16%
2071
9%
760
50%
760
28%
1360
September21st to endNight
37%
760
19%
2090
12%
760
42%
760
24%
1431
October1st to 10thNight
33%
760
12%
3003
11%
740
41%
740
13%
2246
October11th to 20thNight
26%
760
8%
3387
6%
740
33%
740
8%
2681
October21st to endNight
19%
836
6%
3896
4%
814
26%
814
8%
2849
November1st to 10thNight
19%
780
11%
2537
6%
780
26%
780
11%
1918
November11th to 20thNight
22%
800
14%
2600
8%
800
29%
800
11%
1977
November21st to endNight
16%
846
9%
2851
5%
846
21%
846
8%
2308
December1st to 10thNight
12%
894
3%
4897
1%
870
16%
870
3%
4259
December11th to 20thNight
13%
893
5%
5485
3%
868
18%
868
3%
4474
December21st to endNight
9%
897
10%
6934
2%
869
15%
869
2%
5121

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
18%12%410%6%5%5%45%6%26%
104713
Night
17%14%5%11%6%44345%26%
104666
TransparencyDay
58%6%11%17%8%1
108199
Night
59%5%10%16%8%1
109270
SeeingDay
28%18%29%17%7%1
15269
Night
26%15%28%22%8%1
24056

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
13%18%10%17%11%6%5%33310%
2597
11th to 20thDay
10%17%8%22%12%6%322218%
2600
21st to endDay
9%13%9%16%8%8%5%346%18%
2780
February1st to 10thDay
12%19%7%14%9%7%5%33318%
1544
11th to 20thDay
13%20%8%14%7%5%5%345%16%
1848
21st to endDay
13%19%5%12%7%5%4345%20%
1570
March1st to 10thDay
17%16%6%10%7%44245%24%
3116
11th to 20thDay
14%23%6%14%5%4423321%
3318
21st to endDay
16%16%5%11%5%3323431%
4056
April1st to 10thDay
21%17%410%6%43345%24%
2280
11th to 20thDay
19%13%47%444345%33%
2333
21st to endDay
22%14%48%5%43346%27%
2470
May1st to 10thDay
21%10%48%5%5%5%35%6%27%
4159
11th to 20thDay
19%9%39%5%5%5%5%6%8%26%
4398
21st to endDay
17%8%37%6%6%6%5%6%7%28%
4837
June1st to 10thDay
24%9%26%5%5%5%45%8%26%
2779
11th to 20thDay
19%6%27%5%46%5%6%9%31%
2850
21st to endDay
25%9%38%6%5%445%6%24%
2780
July1st to 10thDay
16%8%39%6%6%6%5%6%8%28%
4440
11th to 20thDay
17%8%38%6%5%5%5%6%8%29%
4440
21st to endDay
18%7%25%445%45%7%39%
4814
August1st to 10thDay
19%7%28%6%5%6%5%7%9%25%
4366
11th to 20thDay
20%8%38%6%6%6%5%7%7%25%
4045
21st to endDay
21%7%26%45%5%36%6%34%
4308
September1st to 10thDay
17%9%37%4445%5%7%35%
2280
11th to 20thDay
20%7%26%33436%6%40%
2108
21st to endDay
20%8%36%445%46%9%33%
2090
October1st to 10thDay
22%11%36%44445%7%30%
2090
11th to 20thDay
22%16%38%5%5%5%35%424%
1753
21st to endDay
25%19%5%9%434245%21%
1881
November1st to 10thDay
19%17%49%5%4333428%
1761
11th to 20thDay
18%18%7%12%5%33345%22%
1800
21st to endDay
19%21%6%11%5%44335%17%
1540
December1st to 10thDay
16%19%8%15%9%5%424413%
2280
11th to 20thDay
19%16%8%12%5%4433323%
2618
21st to endDay
18%21%6%13%6%4433419%
3784
January1st to 10thNight
13%19%9%18%8%6%424314%
4569
11th to 20thNight
10%18%7%18%12%6%433415%
4580
21st to endNight
9%17%8%15%8%6%6%45%418%
4899
February1st to 10thNight
11%17%6%12%9%6%5%34421%
2632
11th to 20thNight
11%19%7%15%7%6%6%34320%
2218
21st to endNight
13%16%6%11%7%5%434427%
1884
March1st to 10thNight
21%16%48%5%46%33428%
3724
11th to 20thNight
13%20%7%15%6%4433323%
3640
21st to endNight
16%16%411%6%5%334429%
3572
April1st to 10thNight
21%15%39%434345%28%
1900
11th to 20thNight
19%10%37%5%4345%6%32%
1796
21st to endNight
22%12%37%435%35%5%30%
1710
May1st to 10thNight
23%8%48%6%45%35%6%28%
2811
11th to 20thNight
19%10%37%5%44447%33%
2495
21st to endNight
18%7%26%445%47%9%35%
2738
June1st to 10thNight
23%10%37%5%45%447%29%
1397
11th to 20thNight
18%6%35%5%45%36%8%36%
1330
21st to endNight
22%8%27%5%5%5%45%7%29%
1393
July1st to 10thNight
13%8%48%7%5%6%5%6%7%31%
2520
11th to 20thNight
20%8%37%5%4445%6%34%
2520
21st to endNight
15%7%26%44446%7%41%
2739
August1st to 10thNight
23%8%36%44436%8%32%
2531
11th to 20thNight
18%11%39%6%45%45%6%29%
2782
21st to endNight
18%7%38%44435%6%38%
3344
September1st to 10thNight
19%6%26%43435%6%39%
1900
11th to 20thNight
16%7%25%334445%46%
2071
21st to endNight
17%8%26%444347%41%
2090
October1st to 10thNight
19%9%26%445%35%7%36%
2090
11th to 20thNight
21%12%37%5%5%5%35%6%29%
2423
21st to endNight
24%14%47%5%4435%426%
2717
November1st to 10thNight
19%16%48%5%5%435%5%26%
2537
11th to 20thNight
17%14%5%11%6%5%434427%
2600
21st to endNight
17%20%7%12%6%4334421%
2851
December1st to 10thNight
15%18%10%20%10%4323411%
4910
11th to 20thNight
19%19%6%15%7%4324417%
5591
21st to endNight
18%20%6%11%5%3333424%
7162

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
78%5%6%9%2
2598
11th to 20thDay
75%3413%41
2600
21st to endDay
67%6%7%11%8%1
2780
February1st to 10thDay
72%46%11%7%1
1544
11th to 20thDay
72%38%9%7%1
1857
21st to endDay
65%5%8%14%6%2
1570
March1st to 10thDay
62%6%7%13%10%2
3119
11th to 20thDay
69%48%11%7%1
3318
21st to endDay
58%36%16%13%3
4056
April1st to 10thDay
64%48%14%8%2
2280
11th to 20thDay
54%49%20%12%2
2333
21st to endDay
60%48%15%11%2
2470
May1st to 10thDay
55%6%10%17%10%1
4173
11th to 20thDay
53%9%16%15%7%1
4402
21st to endDay
51%8%10%18%12%
4837
June1st to 10thDay
55%7%10%20%6%1
2779
11th to 20thDay
48%6%14%20%10%1
2850
21st to endDay
60%7%9%16%8%
2780
July1st to 10thDay
52%8%13%22%6%
4370
11th to 20thDay
50%8%16%22%4
4365
21st to endDay
44%7%14%28%7%
4661
August1st to 10thDay
53%8%15%20%4
4352
11th to 20thDay
55%9%16%16%5%
4084
21st to endDay
50%5%14%19%12%1
4308
September1st to 10thDay
47%7%14%23%9%1
2280
11th to 20thDay
44%5%12%27%12%
2108
21st to endDay
46%7%13%23%10%
2090
October1st to 10thDay
53%6%13%23%5%
3480
11th to 20thDay
58%412%22%3
2891
21st to endDay
58%416%16%7%
3081
November1st to 10thDay
61%5%10%18%7%
1761
11th to 20thDay
65%49%13%7%1
1800
21st to endDay
71%6%9%11%3
1540
December1st to 10thDay
77%38%7%5%
2280
11th to 20thDay
68%46%14%9%
2618
21st to endDay
70%35%10%10%2
3784
January1st to 10thNight
74%6%8%9%3
4569
11th to 20thNight
75%5%6%10%31
4580
21st to endNight
68%6%8%10%7%1
4899
February1st to 10thNight
66%49%12%8%1
2632
11th to 20thNight
70%47%11%7%1
2220
21st to endNight
61%48%14%11%2
1884
March1st to 10thNight
58%7%10%14%8%2
3734
11th to 20thNight
67%5%7%13%7%1
3641
21st to endNight
61%37%18%9%2
3572
April1st to 10thNight
59%49%15%12%2
1900
11th to 20thNight
51%5%10%20%12%2
1796
21st to endNight
55%5%10%16%11%2
1710
May1st to 10thNight
56%6%12%16%8%1
2817
11th to 20thNight
49%9%11%19%10%1
2496
21st to endNight
44%7%15%18%15%1
2739
June1st to 10thNight
52%7%12%20%7%
1397
11th to 20thNight
46%6%11%24%12%2
1330
21st to endNight
54%7%12%19%9%
1393
July1st to 10thNight
49%8%16%19%7%
2480
11th to 20thNight
48%7%19%20%6%
2472
21st to endNight
42%7%18%26%6%
2651
August1st to 10thNight
50%7%15%24%4
2521
11th to 20thNight
55%8%15%17%5%
2809
21st to endNight
47%6%13%21%13%
3344
September1st to 10thNight
45%6%14%25%10%1
1900
11th to 20thNight
39%6%15%30%9%1
2071
21st to endNight
43%8%12%24%13%1
2090
October1st to 10thNight
50%5%11%24%10%
3480
11th to 20thNight
55%410%25%5%
4024
21st to endNight
53%5%17%16%9%1
4467
November1st to 10thNight
60%5%12%17%5%1
2537
11th to 20thNight
61%411%14%9%1
2600
21st to endNight
68%5%10%13%5%
2851
December1st to 10thNight
80%37%7%2
4910
11th to 20thNight
73%45%13%5%
5592
21st to endNight
66%36%14%10%
7162

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
33%19%37%10%2
200
11th to 20thDay
31%26%30%11%3
200
21st to endDay
23%26%33%16%21
200
February1st to 10thDay
38%24%27%7%21
201
11th to 20thDay
30%28%32%10%1
456
21st to endDay
32%23%27%15%3
382
March1st to 10thDay
29%22%30%15%4
460
11th to 20thDay
32%24%27%12%41
460
21st to endDay
31%24%27%11%7%1
506
April1st to 10thDay
38%20%25%11%5%2
460
11th to 20thDay
34%21%24%13%6%1
452
21st to endDay
33%23%27%12%32
460
May1st to 10thDay
34%16%30%15%5%1
463
11th to 20thDay
24%15%32%19%8%2
487
21st to endDay
23%21%36%14%6%1
529
June1st to 10thDay
30%14%29%17%9%1
609
11th to 20thDay
22%14%29%24%10%1
680
21st to endDay
27%12%30%20%9%2
610
July1st to 10thDay
21%13%31%27%7%1
485
11th to 20thDay
19%13%41%19%8%
484
21st to endDay
23%10%34%26%6%2
532
August1st to 10thDay
23%14%29%22%10%2
486
11th to 20thDay
22%9%29%27%11%2
479
21st to endDay
25%13%25%20%12%5%
539
September1st to 10thDay
21%16%29%22%8%4
490
11th to 20thDay
23%11%24%24%14%5%
490
21st to endDay
22%17%26%21%10%5%
490
October1st to 10thDay
26%17%28%18%10%2
490
11th to 20thDay
32%16%27%15%8%1
410
21st to endDay
39%19%22%16%3
429
November1st to 10thDay
36%16%29%15%4
395
11th to 20thDay
30%22%26%15%7%1
400
21st to endDay
34%23%30%11%1
235
December1st to 10thDay
35%18%30%13%41
200
11th to 20thDay
38%25%26%10%3
200
21st to endDay
35%22%28%12%31
220
January1st to 10thNight
28%23%32%14%21
800
11th to 20thNight
28%22%30%15%5%
800
21st to endNight
19%20%35%20%41
841
February1st to 10thNight
22%24%33%18%5%
760
11th to 20thNight
25%22%35%15%3
743
21st to endNight
25%17%34%19%5%
628
March1st to 10thNight
26%18%35%19%3
760
11th to 20thNight
26%21%31%18%41
760
21st to endNight
25%17%28%25%5%1
836
April1st to 10thNight
32%16%27%20%5%
760
11th to 20thNight
27%15%30%21%7%
672
21st to endNight
30%16%27%20%6%
570
May1st to 10thNight
28%13%29%24%6%1
560
11th to 20thNight
23%8%31%30%6%1
374
21st to endNight
23%8%34%27%7%1
411
June1st to 10thNight
26%12%25%28%8%1
380
11th to 20thNight
22%8%25%33%13%
380
21st to endNight
23%8%29%29%11%1
380
July1st to 10thNight
15%6%32%35%12%1
370
11th to 20thNight
15%7%26%39%13%1
368
21st to endNight
18%7%24%41%10%
416
August1st to 10thNight
20%420%38%18%1
390
11th to 20thNight
19%7%23%33%18%1
562
21st to endNight
21%7%24%29%17%3
756
September1st to 10thNight
21%8%26%30%12%2
760
11th to 20thNight
21%8%22%28%20%2
760
21st to endNight
22%9%28%25%15%1
760
October1st to 10thNight
24%12%26%26%11%1
760
11th to 20thNight
28%15%25%22%9%1
760
21st to endNight
34%17%25%19%4
836
November1st to 10thNight
31%18%26%21%5%
780
11th to 20thNight
28%18%27%18%10%1
800
21st to endNight
32%20%26%17%5%
846
December1st to 10thNight
34%19%27%15%5%
900
11th to 20thNight
30%23%24%17%5%1
900
21st to endNight
35%20%25%15%5%
917
Page generated at 2025-01-19 03:06:49. Version ac07

Copyright © 2025 Attilla Danko.


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