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Ste-Thérèse
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ste-Thérèse clear sky chart from 2005-11-05 to 2017-09-10.

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
34%
14599
14%
46769
9%
14567
40%
14567
18%
32745

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
19%
720
10%
2506
6%
716
25%
716
10%
1917
January16th to endNight
25%
768
12%
2688
7%
768
32%
768
13%
1967
February1st to 15thNight
23%
704
10%
2310
6%
701
30%
701
12%
1766
February16th to endNight
26%
631
14%
1896
7%
631
36%
631
16%
1400
March1st to 15thNight
26%
720
14%
2160
10%
720
32%
720
16%
1591
March16th to endNight
35%
768
20%
1994
10%
768
42%
768
25%
1393
April1st to 15thNight
30%
718
17%
1796
6%
718
35%
718
21%
1342
April16th to endNight
30%
625
17%
1705
6%
625
37%
625
23%
1194
May1st to 15thNight
31%
386
16%
1466
12%
386
41%
386
17%
969
May16th to endNight
35%
375
13%
1497
14%
374
44%
374
18%
978
June1st to 15thNight
39%
360
9%
1440
9%
360
46%
360
15%
984
June16th to endNight
44%
360
8%
1440
10%
360
48%
360
18%
917
July1st to 15thNight
55%
340
14%
1360
20%
340
60%
340
26%
757
July16th to endNight
58%
376
13%
1418
16%
354
61%
354
25%
806
August1st to 15thNight
60%
359
15%
1430
18%
357
62%
357
22%
860
August16th to endNight
57%
760
20%
1906
11%
760
60%
760
38%
1205
September1st to 15thNight
52%
700
14%
1750
7%
700
53%
700
30%
1203
September16th to endNight
50%
657
21%
1803
14%
657
54%
657
32%
1145
October1st to 15thNight
36%
660
20%
1950
12%
660
46%
660
23%
1316
October16th to endNight
30%
704
12%
2255
8%
704
37%
704
16%
1621
November1st to 15thNight
30%
700
18%
2277
12%
700
40%
700
18%
1599
November16th to endNight
27%
720
15%
2514
10%
720
35%
720
13%
1812
December1st to 15thNight
22%
720
10%
2520
5%
720
29%
720
11%
1924
December16th to endNight
16%
768
12%
2688
5%
768
25%
768
10%
2079

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%8%36%5%35%45%6%33%
47870
Night
18%9%36%5%24446%33%
46938
Cloud CoverDay
18%8%35%5%3445%6%33%
47879
Night
18%9%36%5%24446%33%
46944
TransparencyDay
50%412%21%10%1
47557
Night
51%411%20%10%1
46769
SeeingDay
21%6%24%26%15%5%
5540
Night
22%6%26%31%11%
14599

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%12%46%7%44345%23%
1432
16th to endDay
12%14%48%7%25%45%5%29%
1536
February1st to 15thDay
12%15%49%5%35%5%46%25%
1551
16th to endDay
16%13%5%8%5%25%34428%
1577
March1st to 15thDay
17%11%48%6%45%35%428%
1790
16th to endDay
18%8%25%5%24345%39%
2226
April1st to 15thDay
22%9%36%5%23335%33%
2152
16th to endDay
20%6%35%5%33445%38%
2254
May1st to 15thDay
22%6%25%6%35%446%32%
2496
16th to endDay
20%6%345%35%45%7%33%
2618
June1st to 15thDay
22%6%245%35%447%32%
2520
16th to endDay
18%5%26%5%26%5%6%8%30%
2520
July1st to 15thDay
12%425%5%36%6%6%8%38%
2520
16th to endDay
12%426%5%36%6%6%9%36%
2654
August1st to 15thDay
12%6%26%6%35%5%6%8%35%
2511
16th to endDay
9%4145%345%5%8%46%
2292
September1st to 15thDay
15%6%24425%45%8%39%
2098
16th to endDay
14%5%24423247%48%
1826
October1st to 15thDay
21%7%25%5%34346%35%
1680
16th to endDay
23%8%46%6%24445%28%
1617
November1st to 15thDay
15%10%36%44445%7%33%
1581
16th to endDay
22%9%345%3445%5%31%
1443
December1st to 15thDay
25%11%5%8%42445%5%22%
1440
16th to endDay
26%12%5%6%5%24346%23%
1536
January1st to 15thNight
18%14%7%8%6%2445%5%22%
2506
16th to endNight
13%11%5%9%8%35%45%5%27%
2688
February1st to 15thNight
13%12%6%10%7%46%5%45%24%
2308
16th to endNight
16%12%5%7%6%2445%5%29%
1896
March1st to 15thNight
19%12%45%5%25%44430%
2147
16th to endNight
16%9%46%5%23335%40%
1994
April1st to 15thNight
25%7%35%423335%33%
1796
16th to endNight
22%5%26%423346%37%
1705
May1st to 15thNight
21%7%27%5%33435%35%
1466
16th to endNight
20%7%25%42445%6%37%
1495
June1st to 15thNight
23%7%35%5%25%447%30%
1440
16th to endNight
18%425%5%35%46%7%37%
1440
July1st to 15thNight
10%314435%5%6%10%42%
1440
16th to endNight
11%4345%25%5%7%9%42%
1514
August1st to 15thNight
11%5%25%5%345%6%8%40%
1440
16th to endNight
12%41432335%8%48%
1906
September1st to 15thNight
15%5%25%5%345%5%7%41%
1750
16th to endNight
17%414323346%48%
1803
October1st to 15thNight
18%5%25%5%2435%6%38%
1950
16th to endNight
25%7%46%423335%32%
2255
November1st to 15thNight
20%8%25%5%245%46%33%
2277
16th to endNight
22%11%37%5%23345%29%
2514
December1st to 15thNight
24%12%47%5%24435%25%
2520
16th to endNight
23%15%5%7%5%2334324%
2688

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
22%12%5%7%8%3444423%
1432
16th to endDay
12%14%38%7%35%446%28%
1536
February1st to 15thDay
13%14%5%9%6%36%5%36%25%
1551
16th to endDay
17%13%5%7%6%35%345%28%
1577
March1st to 15thDay
18%10%48%6%35%445%27%
1800
16th to endDay
18%9%35%5%24246%38%
2225
April1st to 15thDay
22%9%25%5%34435%32%
2152
16th to endDay
20%6%35%5%2344438%
2254
May1st to 15thDay
21%6%26%5%45%446%32%
2496
16th to endDay
20%5%25%435%5%5%8%33%
2618
June1st to 15thDay
22%7%245%3445%7%31%
2520
16th to endDay
17%6%35%5%36%5%6%8%31%
2520
July1st to 15thDay
12%425%5%36%5%6%9%38%
2520
16th to endDay
12%425%5%35%6%7%9%37%
2654
August1st to 15thDay
12%5%36%7%35%5%6%8%35%
2511
16th to endDay
9%4145%35%46%8%47%
2292
September1st to 15thDay
16%6%24425%45%8%39%
2098
16th to endDay
15%424433347%47%
1826
October1st to 15thDay
21%6%25%5%35%345%35%
1680
16th to endDay
24%8%35%6%34446%27%
1617
November1st to 15thDay
16%9%45%5%3346%6%33%
1581
16th to endDay
23%9%34425%445%31%
1443
December1st to 15thDay
26%10%47%5%3345%5%21%
1440
16th to endDay
26%13%45%5%24345%22%
1536
January1st to 15thNight
18%14%6%9%6%3345%5%22%
2506
16th to endNight
13%12%5%8%7%35%445%27%
2688
February1st to 15thNight
13%13%5%10%7%35%5%46%22%
2301
16th to endNight
17%12%47%6%25%445%29%
1896
March1st to 15thNight
20%12%36%5%34445%29%
2160
16th to endNight
16%9%36%5%2324439%
1994
April1st to 15thNight
26%7%45%424335%32%
1796
16th to endNight
22%6%345%23445%37%
1705
May1st to 15thNight
21%7%26%6%24335%35%
1466
16th to endNight
20%5%35%42445%6%35%
1495
June1st to 15thNight
24%7%25%43445%7%30%
1440
16th to endNight
17%436%425%5%6%8%35%
1440
July1st to 15thNight
10%314426%6%7%9%42%
1440
16th to endNight
10%3344335%7%10%41%
1514
August1st to 15thNight
12%5%25%5%25%46%9%40%
1440
16th to endNight
13%313434449%48%
1906
September1st to 15thNight
15%435%5%34447%41%
1750
16th to endNight
17%424322346%47%
1803
October1st to 15thNight
18%5%26%5%33446%38%
1950
16th to endNight
25%8%46%433335%31%
2255
November1st to 15thNight
20%8%26%5%25%445%33%
2277
16th to endNight
22%11%47%5%23335%29%
2514
December1st to 15thNight
24%12%47%5%34345%24%
2520
16th to endNight
24%16%48%5%2333423%
2688

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
64%48%15%6%
1433
16th to endDay
55%411%17%8%
1536
February1st to 15thDay
59%311%18%5%
1553
16th to endDay
59%210%16%9%1
1577
March1st to 15thDay
58%312%15%9%1
1800
16th to endDay
47%310%18%15%4
2226
April1st to 15thDay
54%37%19%12%3
2152
16th to endDay
49%37%20%14%4
2254
May1st to 15thDay
52%38%19%13%2
2496
16th to endDay
48%411%20%12%1
2622
June1st to 15thDay
51%411%19%10%1
2520
16th to endDay
49%5%12%22%8%1
2520
July1st to 15thDay
39%6%15%26%12%
2371
16th to endDay
41%5%18%24%8%
2487
August1st to 15thDay
45%5%18%22%8%
2497
16th to endDay
33%419%28%12%
2292
September1st to 15thDay
41%5%13%26%12%
2098
16th to endDay
37%312%32%12%
1826
October1st to 15thDay
49%312%23%10%
1680
16th to endDay
58%412%17%7%
1617
November1st to 15thDay
48%5%13%20%10%
1581
16th to endDay
54%5%11%20%7%
1443
December1st to 15thDay
64%312%15%4
1440
16th to endDay
63%411%12%7%
1536
January1st to 15thNight
63%310%16%5%
2506
16th to endNight
57%410%17%8%1
2688
February1st to 15thNight
62%310%17%6%
2310
16th to endNight
57%39%17%10%
1896
March1st to 15thNight
57%39%17%9%1
2160
16th to endNight
48%29%18%16%4
1994
April1st to 15thNight
53%45%20%14%2
1796
16th to endNight
48%47%19%15%4
1705
May1st to 15thNight
51%27%18%14%4
1466
16th to endNight
47%5%9%20%13%2
1497
June1st to 15thNight
52%410%20%10%
1440
16th to endNight
44%6%12%19%15%1
1440
July1st to 15thNight
33%7%14%28%15%
1360
16th to endNight
35%6%19%24%13%
1418
August1st to 15thNight
40%5%17%23%11%
1430
16th to endNight
34%416%31%13%
1906
September1st to 15thNight
42%5%12%25%13%
1750
16th to endNight
38%411%32%13%
1803
October1st to 15thNight
46%49%26%12%
1950
16th to endNight
55%312%20%7%
2255
November1st to 15thNight
52%412%20%9%2
2277
16th to endNight
57%310%20%7%
2514
December1st to 15thNight
62%411%17%3
2520
16th to endNight
65%39%13%7%
2688

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
16%13%25%33%11%
60
16th to endDay
26%7%29%26%6%3
64
February1st to 15thDay
31%13%27%23%3
86
16th to endDay
27%5%28%30%8%
236
March1st to 15thDay
21%11%29%28%8%
270
16th to endDay
23%6%28%25%12%3
288
April1st to 15thDay
27%11%25%22%9%4
270
16th to endDay
19%9%28%25%13%4
270
May1st to 15thDay
26%5%27%22%13%3
288
16th to endDay
20%8%30%21%15%4
331
June1st to 15thDay
26%9%23%24%12%3
315
16th to endDay
18%422%33%18%2
315
July1st to 15thDay
14%321%33%21%5%
305
16th to endDay
14%213%39%23%6%
326
August1st to 15thDay
14%315%30%26%9%
313
16th to endDay
9%320%29%22%14%
332
September1st to 15thDay
17%418%23%24%11%
294
16th to endDay
17%7%25%18%17%13%
254
October1st to 15thDay
21%6%23%26%18%3
255
16th to endDay
30%8%24%23%12%
246
November1st to 15thDay
22%8%25%26%13%2
235
16th to endDay
31%11%20%23%12%
63
December1st to 15thDay
30%131%26%6%3
60
16th to endDay
35%12%39%10%1
64
January1st to 15thNight
23%12%30%26%7%
720
16th to endNight
18%9%34%28%8%
768
February1st to 15thNight
20%7%33%30%7%
704
16th to endNight
24%6%32%30%6%
631
March1st to 15thNight
26%8%29%30%5%
720
16th to endNight
20%6%27%34%9%
768
April1st to 15thNight
27%8%25%32%5%
718
16th to endNight
25%8%30%25%9%
625
May1st to 15thNight
24%428%30%9%1
386
16th to endNight
21%430%34%8%
375
June1st to 15thNight
30%320%32%13%
360
16th to endNight
18%325%38%14%
360
July1st to 15thNight
10%324%41%20%
340
16th to endNight
10%318%46%19%1
376
August1st to 15thNight
14%311%42%24%2
359
16th to endNight
14%119%36%25%2
760
September1st to 15thNight
17%317%42%17%1
700
16th to endNight
18%322%31%21%2
657
October1st to 15thNight
21%5%28%32%11%1
660
16th to endNight
29%6%27%27%8%
704
November1st to 15thNight
24%6%30%27%11%
700
16th to endNight
27%10%25%24%12%
720
December1st to 15thNight
31%7%26%26%6%
720
16th to endNight
32%7%30%22%5%
768
Page generated at 2017-09-11 19:35:21. Version ac04

Copyright 2017 A. Danko


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