Saint-Nicephore
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint-Nicephore clear sky chart from 2005-11-06 to 2024-01-22.

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
28%
22548
12%
74830
8%
22509
34%
22509
14%
55057

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
15%
760
8%
2649
3%
757
20%
757
7%
2186
January11th to 20thNight
17%
760
8%
2660
4%
760
22%
760
7%
2166
January21st to endNight
22%
800
11%
2798
7%
800
28%
800
10%
2120
February1st to 10thNight
16%
720
9%
2448
4%
720
23%
720
9%
1936
February11th to 20thNight
15%
703
11%
2131
3%
700
24%
700
11%
1674
February21st to endNight
22%
592
14%
1776
7%
592
32%
592
13%
1352
March1st to 10thNight
21%
720
14%
2160
8%
720
29%
720
13%
1637
March11th to 20thNight
21%
720
14%
2114
6%
720
30%
720
13%
1620
March21st to endNight
28%
792
19%
1985
7%
792
35%
792
19%
1492
April1st to 10thNight
23%
720
12%
1800
4%
720
27%
720
16%
1407
April11th to 20thNight
28%
685
16%
1749
5%
685
34%
685
21%
1279
April21st to endNight
25%
540
15%
1620
7%
540
32%
540
16%
1172
May1st to 10thNight
27%
478
15%
1558
9%
478
35%
478
15%
1111
May11th to 20thNight
29%
354
17%
1416
14%
354
41%
354
15%
928
May21st to endNight
32%
389
12%
1551
10%
388
42%
388
17%
1009
June1st to 10thNight
32%
360
9%
1440
9%
360
40%
360
15%
981
June11th to 20thNight
40%
360
11%
1440
15%
360
45%
360
19%
910
June21st to endNight
39%
360
8%
1440
9%
360
45%
360
15%
979
July1st to 10thNight
46%
350
11%
1400
16%
350
51%
350
21%
871
July11th to 20thNight
51%
348
12%
1392
18%
348
55%
348
21%
868
July21st to endNight
48%
394
12%
1486
15%
372
51%
372
20%
936
August1st to 10thNight
52%
358
15%
1422
16%
356
56%
356
21%
867
August11th to 20thNight
48%
501
14%
1565
10%
501
52%
501
23%
1049
August21st to endNight
45%
788
17%
1976
9%
788
48%
788
28%
1372
September1st to 10thNight
44%
720
12%
1800
6%
720
46%
720
29%
1244
September11th to 20thNight
48%
720
18%
1922
11%
720
51%
720
32%
1230
September21st to endNight
39%
720
20%
1980
13%
720
43%
720
26%
1348
October1st to 10thNight
36%
720
20%
2029
12%
720
44%
720
22%
1413
October11th to 20thNight
30%
720
14%
2255
9%
720
37%
720
15%
1688
October21st to endNight
22%
792
10%
2574
5%
792
29%
792
12%
1952
November1st to 10thNight
21%
740
13%
2407
7%
740
30%
740
13%
1769
November11th to 20thNight
22%
760
16%
2484
10%
760
30%
760
13%
1857
November21st to endNight
21%
760
11%
2660
6%
760
28%
760
9%
2062
December1st to 10thNight
15%
760
6%
2660
3%
760
19%
760
6%
2206
December11th to 20thNight
16%
760
10%
3245
4%
759
23%
759
6%
2592
December21st to endNight
14%
824
7%
4838
3%
817
20%
817
4%
3774

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
19%10%47%6%35%45%6%30%
74841
Night
19%12%47%6%34446%30%
75090
TransparencyDay
54%6%12%19%8%1
74546
Night
56%6%10%18%9%1
74919
SeeingDay
25%13%28%21%10%3
13528
Night
26%11%28%26%9%1
22560

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
21%19%6%10%8%3444316%
1517
11th to 20thDay
19%17%7%11%7%3443421%
1520
21st to endDay
11%15%6%10%8%35%5%6%6%26%
1592
February1st to 10thDay
16%19%6%9%6%46%5%4422%
1508
11th to 20thDay
16%16%7%11%6%46%345%22%
1716
21st to endDay
15%17%6%8%7%35%5%46%24%
1480
March1st to 10thDay
17%14%5%9%8%45%445%26%
1797
11th to 20thDay
19%13%47%5%45%445%30%
1845
21st to endDay
18%12%5%7%5%35%445%31%
2368
April1st to 10thDay
23%12%5%7%6%44335%27%
2160
11th to 20thDay
22%9%36%434445%36%
2160
21st to endDay
26%9%37%5%34445%29%
2340
May1st to 10thDay
23%8%36%6%34446%34%
2419
11th to 20thDay
18%8%36%6%35%45%7%36%
2478
21st to endDay
19%7%36%6%45%5%5%7%32%
2725
June1st to 10thDay
24%7%36%5%345%6%7%29%
2520
11th to 20thDay
18%6%36%5%445%6%8%36%
2520
21st to endDay
21%8%38%6%35%5%5%6%30%
2520
July1st to 10thDay
15%6%25%7%36%5%6%9%36%
2520
11th to 20thDay
12%6%37%6%36%7%6%9%36%
2520
21st to endDay
15%6%36%6%45%5%7%9%34%
2744
August1st to 10thDay
16%7%37%6%45%6%6%8%32%
2506
11th to 20thDay
14%6%26%6%35%6%6%9%37%
2317
21st to endDay
16%6%35%5%345%6%8%39%
2376
September1st to 10thDay
14%6%36%5%35%5%5%8%40%
2160
11th to 20thDay
19%5%25%42345%7%44%
2037
21st to endDay
19%7%25%4345%6%7%39%
1980
October1st to 10thDay
21%7%26%6%35%5%6%8%31%
1928
11th to 20thDay
22%10%47%6%45%45%7%27%
1703
21st to endDay
27%13%37%5%3435%6%25%
1782
November1st to 10thDay
20%12%46%6%3436%6%31%
1671
11th to 20thDay
19%14%6%9%6%34446%25%
1694
21st to endDay
23%14%6%8%6%25%45%5%23%
1520
December1st to 10thDay
26%17%7%9%6%3443318%
1520
11th to 20thDay
23%15%7%7%5%3344425%
1906
21st to endDay
26%18%6%11%5%2324419%
2772
January1st to 10thNight
20%19%7%10%6%3444418%
2649
11th to 20thNight
17%18%6%12%8%35%44420%
2660
21st to endNight
13%15%6%10%8%5%5%5%46%25%
2798
February1st to 10thNight
15%16%6%11%9%46%45%422%
2448
11th to 20thNight
15%15%6%12%8%35%445%24%
2129
21st to endNight
15%15%6%8%6%4444430%
1776
March1st to 10thNight
17%15%5%9%7%3435%428%
2150
11th to 20thNight
20%12%6%7%6%4444429%
2113
21st to endNight
18%13%5%6%5%34445%34%
1985
April1st to 10thNight
25%9%5%8%6%3445%5%27%
1800
11th to 20thNight
23%8%36%5%34346%34%
1749
21st to endNight
24%10%36%5%3345%6%31%
1620
May1st to 10thNight
24%10%37%5%2445%7%30%
1558
11th to 20thNight
20%8%36%6%345%47%36%
1415
21st to endNight
20%6%25%6%345%6%8%36%
1550
June1st to 10thNight
23%6%36%6%25%46%8%30%
1440
11th to 20thNight
19%6%35%435%5%5%9%36%
1440
21st to endNight
18%7%45%5%45%5%6%8%32%
1440
July1st to 10thNight
13%5%37%6%35%6%6%9%38%
1440
11th to 20thNight
11%5%26%6%46%7%6%9%37%
1440
21st to endNight
13%5%36%6%35%6%7%9%36%
1574
August1st to 10thNight
16%5%25%5%35%5%7%9%39%
1432
11th to 20thNight
15%6%36%6%45%6%5%7%37%
1565
21st to endNight
15%7%36%5%335%5%9%40%
1976
September1st to 10thNight
15%7%35%6%3445%6%42%
1800
11th to 20thNight
18%425%423446%47%
1922
21st to endNight
18%5%36%5%34448%41%
1980
October1st to 10thNight
19%6%36%5%3445%6%39%
2029
11th to 20thNight
22%10%37%5%35%446%30%
2255
21st to endNight
26%10%47%5%34445%27%
2574
November1st to 10thNight
20%12%47%6%34446%29%
2407
11th to 20thNight
20%12%5%8%6%34445%29%
2484
21st to endNight
22%14%6%8%7%34435%26%
2660
December1st to 10thNight
24%18%7%9%7%3334418%
2660
11th to 20thNight
21%17%6%10%7%3333422%
3288
21st to endNight
25%20%6%8%5%3333422%
4884

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
73%5%8%12%2
1518
11th to 20thDay
69%5%8%13%5%
1520
21st to endDay
58%6%11%16%7%1
1592
February1st to 10thDay
67%48%16%41
1508
11th to 20thDay
66%411%12%7%1
1725
21st to endDay
63%5%9%15%7%2
1480
March1st to 10thDay
61%5%9%15%8%2
1800
11th to 20thDay
56%6%12%12%13%1
1845
21st to endDay
57%48%20%10%2
2368
April1st to 10thDay
62%49%16%9%2
2160
11th to 20thDay
51%5%9%20%13%2
2160
21st to endDay
57%5%8%16%11%3
2340
May1st to 10thDay
52%410%19%13%2
2419
11th to 20thDay
48%5%11%22%12%2
2482
21st to endDay
50%7%11%18%12%1
2725
June1st to 10thDay
52%7%11%20%9%1
2520
11th to 20thDay
46%7%12%22%12%1
2520
21st to endDay
55%7%10%20%9%
2520
July1st to 10thDay
44%8%14%26%8%
2450
11th to 20thDay
43%8%16%25%7%
2445
21st to endDay
47%8%15%22%7%
2591
August1st to 10thDay
48%8%17%22%4
2492
11th to 20thDay
42%9%18%23%9%
2317
21st to endDay
42%6%16%24%12%
2376
September1st to 10thDay
42%7%15%26%10%1
2160
11th to 20thDay
39%5%14%30%12%
2037
21st to endDay
44%6%15%26%9%
1980
October1st to 10thDay
51%6%13%22%7%
1928
11th to 20thDay
57%6%15%18%4
1703
21st to endDay
63%5%10%16%6%1
1782
November1st to 10thDay
54%5%14%19%8%
1671
11th to 20thDay
61%5%11%14%8%
1694
21st to endDay
64%6%12%13%3
1520
December1st to 10thDay
73%410%10%3
1520
11th to 20thDay
64%48%18%5%
1906
21st to endDay
71%48%11%5%
2772
January1st to 10thNight
70%6%8%12%3
2649
11th to 20thNight
69%5%8%12%5%1
2660
21st to endNight
62%5%9%15%8%1
2798
February1st to 10thNight
67%48%14%7%1
2448
11th to 20thNight
63%5%8%16%8%
2131
21st to endNight
58%6%8%14%12%1
1776
March1st to 10thNight
60%49%16%9%1
2160
11th to 20thNight
59%6%7%14%12%3
2114
21st to endNight
54%46%20%12%3
1985
April1st to 10thNight
58%5%8%16%11%1
1800
11th to 20thNight
51%5%7%21%14%2
1749
21st to endNight
54%5%9%17%12%2
1620
May1st to 10thNight
54%5%7%16%15%3
1558
11th to 20thNight
50%5%10%17%15%3
1416
21st to endNight
46%7%11%19%15%2
1551
June1st to 10thNight
52%6%11%21%10%1
1440
11th to 20thNight
46%5%11%23%12%3
1440
21st to endNight
49%8%12%19%11%1
1440
July1st to 10thNight
41%8%15%23%13%1
1400
11th to 20thNight
41%7%15%25%11%
1392
21st to endNight
41%9%17%24%8%1
1486
August1st to 10thNight
40%8%19%26%7%
1422
11th to 20thNight
44%7%17%24%8%
1565
21st to endNight
41%8%14%27%10%1
1976
September1st to 10thNight
42%7%15%24%12%1
1800
11th to 20thNight
38%5%16%31%11%1
1922
21st to endNight
44%6%11%26%13%
1980
October1st to 10thNight
47%6%10%25%12%
2029
11th to 20thNight
55%7%10%22%5%
2255
21st to endNight
60%6%10%15%9%1
2574
November1st to 10thNight
56%6%11%19%7%1
2407
11th to 20thNight
57%6%11%16%8%1
2484
21st to endNight
63%5%11%16%5%
2660
December1st to 10thNight
72%49%12%3
2660
11th to 20thNight
67%5%7%16%5%
3288
21st to endNight
69%48%15%4
4884

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
31%12%35%18%41
180
11th to 20thDay
33%15%35%12%4
180
21st to endDay
24%19%32%16%8%1
178
February1st to 10thDay
37%22%33%7%11
190
11th to 20thDay
28%19%37%13%3
384
21st to endDay
25%20%33%20%2
346
March1st to 10thDay
26%18%29%22%4
420
11th to 20thDay
28%19%29%18%6%1
420
21st to endDay
28%17%27%19%7%2
462
April1st to 10thDay
32%13%29%18%7%1
420
11th to 20thDay
33%17%22%18%8%2
412
21st to endDay
29%15%33%12%9%2
420
May1st to 10thDay
30%15%29%16%9%1
423
11th to 20thDay
21%11%35%22%9%2
447
21st to endDay
20%19%30%20%10%1
485
June1st to 10thDay
25%14%32%20%8%2
450
11th to 20thDay
20%12%30%24%13%1
450
21st to endDay
23%11%30%22%11%2
450
July1st to 10thDay
16%8%27%29%16%3
445
11th to 20thDay
16%9%30%33%9%4
444
21st to endDay
18%8%27%33%11%2
488
August1st to 10thDay
20%8%23%28%18%4
446
11th to 20thDay
18%5%24%29%19%4
439
21st to endDay
19%12%24%21%15%9%
495
September1st to 10thDay
16%10%30%25%12%6%
450
11th to 20thDay
21%9%23%21%18%8%
450
21st to endDay
20%11%24%24%16%4
450
October1st to 10thDay
23%11%26%23%12%5%
450
11th to 20thDay
27%15%27%18%11%2
401
21st to endDay
37%12%26%20%6%
396
November1st to 10thDay
33%13%29%20%5%1
365
11th to 20thDay
31%18%26%18%6%2
354
21st to endDay
32%21%29%12%6%1
180
December1st to 10thDay
38%13%22%19%6%3
180
11th to 20thDay
31%22%27%17%21
180
21st to endDay
39%17%24%13%6%1
198
January1st to 10thNight
33%13%29%20%5%
760
11th to 20thNight
29%13%33%20%6%
760
21st to endNight
21%11%35%26%6%1
800
February1st to 10thNight
25%15%33%23%4
720
11th to 20thNight
24%17%35%19%5%1
703
21st to endNight
25%13%32%26%4
592
March1st to 10thNight
25%13%34%24%3
720
11th to 20thNight
28%14%30%21%6%1
720
21st to endNight
25%11%30%26%7%1
792
April1st to 10thNight
32%12%26%24%6%
720
11th to 20thNight
26%16%26%25%7%
685
21st to endNight
31%10%31%21%7%
540
May1st to 10thNight
27%12%29%25%7%
478
11th to 20thNight
24%9%30%29%8%1
354
21st to endNight
22%6%33%31%8%
389
June1st to 10thNight
27%5%29%30%9%
360
11th to 20thNight
20%6%27%34%13%
360
21st to endNight
21%6%28%33%12%1
360
July1st to 10thNight
15%5%29%38%13%1
350
11th to 20thNight
10%426%43%15%1
348
21st to endNight
14%6%23%45%11%
394
August1st to 10thNight
18%320%39%20%1
358
11th to 20thNight
18%323%34%20%2
501
21st to endNight
18%5%23%34%17%3
788
September1st to 10thNight
18%5%26%35%13%2
720
11th to 20thNight
20%5%22%30%20%2
720
21st to endNight
19%7%28%28%15%2
720
October1st to 10thNight
22%10%26%29%12%1
720
11th to 20thNight
29%9%25%26%10%1
720
21st to endNight
33%11%29%22%5%
792
November1st to 10thNight
28%13%29%23%7%
740
11th to 20thNight
27%15%30%18%10%1
760
21st to endNight
31%16%26%20%6%1
760
December1st to 10thNight
36%13%27%18%6%
760
11th to 20thNight
30%15%29%20%6%1
760
21st to endNight
37%15%24%19%5%
836
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