St-Valérien-de-Milton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the St-Valérien-de-Milton clear sky chart from 2005-11-05 to 2018-03-21.

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%
15371
12%
49229
8%
15339
34%
15339
14%
36432

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
17%
780
8%
2716
5%
776
22%
776
7%
2226
January16th to endNight
18%
832
8%
2912
5%
832
23%
832
8%
2329
February1st to 15thNight
17%
764
8%
2512
3%
761
23%
761
9%
2050
February16th to endNight
20%
683
10%
2049
5%
683
27%
683
11%
1620
March1st to 15thNight
22%
780
13%
2340
9%
780
28%
780
12%
1825
March16th to endNight
30%
792
20%
2076
9%
792
38%
792
20%
1498
April1st to 15thNight
24%
718
13%
1796
5%
718
28%
718
16%
1412
April16th to endNight
28%
591
17%
1671
6%
591
36%
591
19%
1177
May1st to 15thNight
28%
433
16%
1513
12%
433
36%
433
17%
1039
May16th to endNight
33%
375
11%
1497
10%
374
41%
374
15%
1004
June1st to 15thNight
31%
360
8%
1440
7%
360
39%
360
12%
1016
June16th to endNight
41%
360
8%
1440
10%
360
47%
360
18%
914
July1st to 15thNight
49%
340
11%
1360
16%
340
52%
340
19%
849
July16th to endNight
49%
376
11%
1418
16%
354
52%
354
21%
873
August1st to 15thNight
49%
393
13%
1464
13%
391
52%
391
20%
923
August16th to endNight
50%
717
18%
1863
11%
717
53%
717
32%
1225
September1st to 15thNight
43%
720
13%
1817
7%
720
45%
720
27%
1257
September16th to endNight
45%
717
21%
1980
14%
717
49%
717
31%
1267
October1st to 15thNight
32%
720
17%
2081
10%
720
40%
720
20%
1479
October16th to endNight
24%
768
10%
2492
7%
768
30%
768
12%
1887
November1st to 15thNight
25%
760
16%
2472
11%
760
32%
760
13%
1846
November16th to endNight
22%
780
12%
2678
9%
780
28%
780
10%
2062
December1st to 15thNight
15%
780
7%
2730
2%
780
21%
780
6%
2253
December16th to endNight
12%
832
9%
2912
3%
832
20%
832
6%
2401

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
20%9%36%5%34446%30%
49626
Night
20%11%47%5%34345%29%
49399
TransparencyDay
54%5%11%18%7%
49314
Night
56%5%10%18%8%
49229
SeeingDay
26%12%27%20%9%3
6178
Night
26%11%27%24%9%
15371

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
22%17%6%10%6%35%33416%
1552
16th to endDay
15%14%6%9%7%36%446%21%
1664
February1st to 15thDay
15%17%7%11%6%46%34419%
1675
16th to endDay
17%15%7%8%6%44345%21%
1710
March1st to 15thDay
19%13%5%7%6%45%435%24%
1940
16th to endDay
18%10%47%424345%34%
2274
April1st to 15thDay
24%11%37%42433430%
2152
16th to endDay
24%7%24434345%35%
2288
May1st to 15thDay
23%7%26%5%3445%6%31%
2448
16th to endDay
21%6%36%5%345%5%7%31%
2618
June1st to 15thDay
26%6%3442445%7%29%
2520
16th to endDay
21%6%26%5%245%6%8%29%
2520
July1st to 15thDay
14%5%25%5%45%5%5%9%34%
2520
16th to endDay
15%5%35%6%345%6%9%33%
2654
August1st to 15thDay
16%6%26%6%45%6%5%9%30%
2472
16th to endDay
13%5%2442445%7%44%
2336
September1st to 15thDay
18%6%25%424346%40%
2142
16th to endDay
16%5%2432435%7%46%
1980
October1st to 15thDay
24%8%26%42435%7%31%
1878
16th to endDay
25%11%36%425%446%25%
1731
November1st to 15thDay
21%10%45%5%33445%31%
1716
16th to endDay
22%12%5%7%5%24345%25%
1612
December1st to 15thDay
27%15%5%8%6%2434416%
1560
16th to endDay
25%19%6%7%6%2434416%
1664
January1st to 15thNight
21%15%6%10%6%3433420%
2716
16th to endNight
15%16%6%8%8%35%44421%
2912
February1st to 15thNight
14%16%7%13%7%34445%19%
2511
16th to endNight
17%14%6%9%5%3433426%
2049
March1st to 15thNight
22%14%5%7%6%3334426%
2327
16th to endNight
17%12%45%32433438%
2076
April1st to 15thNight
26%11%36%5%2434427%
1796
16th to endNight
22%8%24424346%36%
1671
May1st to 15thNight
23%7%35%5%23346%33%
1513
16th to endNight
22%6%2442446%7%33%
1495
June1st to 15thNight
29%6%1443435%6%28%
1440
16th to endNight
16%5%26%5%345%6%8%36%
1440
July1st to 15thNight
15%5%26%5%25%5%6%9%35%
1440
16th to endNight
13%5%245%25%5%6%9%39%
1514
August1st to 15thNight
15%6%35%43446%7%38%
1474
16th to endNight
13%5%24424449%43%
1863
September1st to 15thNight
19%6%25%423346%41%
1817
16th to endNight
18%413422348%45%
1980
October1st to 15thNight
18%8%27%5%24345%36%
2081
16th to endNight
28%9%46%334335%27%
2492
November1st to 15thNight
21%11%36%5%35%445%29%
2472
16th to endNight
24%14%47%42333426%
2678
December1st to 15thNight
24%17%5%7%6%4433418%
2730
16th to endNight
23%18%6%8%6%3433318%
2912

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
72%47%11%3
1553
16th to endDay
64%5%12%14%3
1664
February1st to 15thDay
69%5%8%13%1
1678
16th to endDay
64%410%12%6%
1710
March1st to 15thDay
64%410%13%6%
1950
16th to endDay
52%310%19%11%1
2274
April1st to 15thDay
58%47%18%9%1
2152
16th to endDay
51%49%18%13%2
2288
May1st to 15thDay
53%410%17%12%
2448
16th to endDay
52%7%10%18%9%1
2622
June1st to 15thDay
54%6%12%17%8%
2520
16th to endDay
51%7%12%20%7%
2520
July1st to 15thDay
43%8%14%26%7%
2371
16th to endDay
47%8%16%21%6%
2487
August1st to 15thDay
50%8%15%20%4
2458
16th to endDay
38%6%17%26%10%
2336
September1st to 15thDay
44%5%13%25%10%
2142
16th to endDay
38%5%13%30%10%
1980
October1st to 15thDay
52%5%13%21%6%
1878
16th to endDay
61%5%12%16%4
1731
November1st to 15thDay
55%6%12%17%7%
1716
16th to endDay
62%5%10%14%6%
1612
December1st to 15thDay
71%410%11%1
1560
16th to endDay
73%48%7%5%
1664
January1st to 15thNight
69%5%8%12%3
2716
16th to endNight
66%5%8%13%5%
2912
February1st to 15thNight
68%48%14%3
2512
16th to endNight
63%48%12%9%
2049
March1st to 15thNight
62%37%16%7%1
2340
16th to endNight
51%37%17%15%3
2076
April1st to 15thNight
60%35%17%11%1
1796
16th to endNight
49%48%19%15%2
1671
May1st to 15thNight
51%48%17%15%3
1513
16th to endNight
48%7%10%21%9%2
1497
June1st to 15thNight
55%5%10%20%7%1
1440
16th to endNight
44%6%13%21%12%
1440
July1st to 15thNight
40%9%13%24%11%
1360
16th to endNight
39%8%16%23%11%
1418
August1st to 15thNight
43%6%17%23%8%
1464
16th to endNight
37%6%17%27%10%
1863
September1st to 15thNight
44%5%12%26%11%
1817
16th to endNight
38%5%12%30%13%
1980
October1st to 15thNight
50%5%10%23%9%
2081
16th to endNight
60%411%17%6%
2492
November1st to 15thNight
56%5%10%18%6%2
2472
16th to endNight
62%49%16%6%
2678
December1st to 15thNight
71%49%12%2
2730
16th to endNight
71%38%9%5%
2912

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
33%10%34%17%4
90
16th to endDay
30%22%29%14%21
96
February1st to 15thDay
38%18%26%11%5%
154
16th to endDay
29%17%31%16%3
291
March1st to 15thDay
34%16%23%21%3
330
16th to endDay
25%15%27%20%8%3
311
April1st to 15thDay
31%15%25%20%42
270
16th to endDay
28%12%28%15%10%4
270
May1st to 15thDay
33%11%27%15%9%2
288
16th to endDay
22%13%30%20%9%2
331
June1st to 15thDay
33%8%26%22%6%1
315
16th to endDay
23%9%36%20%8%1
315
July1st to 15thDay
21%7%32%22%11%3
305
16th to endDay
18%430%33%11%2
326
August1st to 15thDay
21%7%25%25%15%3
313
16th to endDay
16%8%26%20%18%9%
332
September1st to 15thDay
20%8%24%23%14%8%
315
16th to endDay
17%10%23%22%16%8%
314
October1st to 15thDay
26%12%25%21%10%4
315
16th to endDay
33%14%23%17%10%
289
November1st to 15thDay
28%13%26%18%11%1
280
16th to endDay
28%21%21%18%8%1
142
December1st to 15thDay
38%14%21%21%13
90
16th to endDay
41%18%30%7%2
96
January1st to 15thNight
29%14%31%19%5%
780
16th to endNight
25%15%30%22%6%
832
February1st to 15thNight
23%13%35%22%5%
764
16th to endNight
25%14%32%21%4
683
March1st to 15thNight
29%12%29%24%3
780
16th to endNight
24%13%26%26%7%1
792
April1st to 15thNight
31%12%26%24%5%
718
16th to endNight
28%14%25%21%10%
591
May1st to 15thNight
25%8%32%21%9%1
433
16th to endNight
25%7%28%29%8%
375
June1st to 15thNight
33%5%24%25%10%
360
16th to endNight
17%431%34%10%
360
July1st to 15thNight
15%5%24%35%17%1
340
16th to endNight
16%225%40%14%
376
August1st to 15thNight
18%222%34%21%
393
16th to endNight
16%323%35%17%3
717
September1st to 15thNight
22%5%23%32%15%1
720
16th to endNight
21%5%25%26%18%2
717
October1st to 15thNight
23%9%28%24%12%1
720
16th to endNight
34%12%26%21%5%
768
November1st to 15thNight
28%13%28%19%10%
760
16th to endNight
32%17%21%18%8%1
780
December1st to 15thNight
34%15%28%17%3
780
16th to endNight
34%15%25%19%4
832
Page generated at 2018-03-22 11:34:27. Version ac04

Copyright 2018 A. Danko


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