Drayton Valley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Drayton Valley clear sky chart from 2005-11-06 to 2024-01-16.

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
38%
23339
11%
74197
7%
23306
43%
23306
17%
52427

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
33%
946
11%
2836
7%
946
36%
946
15%
2136
January11th to 20thNight
32%
930
14%
2790
6%
930
39%
930
16%
2042
January21st to endNight
26%
834
14%
2814
7%
834
36%
834
12%
2091
February1st to 10thNight
34%
720
12%
2520
9%
720
40%
720
13%
1822
February11th to 20thNight
31%
701
10%
2364
8%
700
36%
700
13%
1748
February21st to endNight
41%
592
15%
1814
12%
592
46%
592
18%
1299
March1st to 10thNight
38%
720
15%
2160
12%
720
42%
720
18%
1591
March11th to 20thNight
39%
720
16%
2044
9%
720
44%
720
21%
1454
March21st to endNight
37%
792
9%
2089
5%
792
39%
792
16%
1621
April1st to 10thNight
33%
679
10%
1759
3%
679
37%
679
16%
1369
April11th to 20thNight
35%
533
12%
1601
8%
533
40%
533
17%
1179
April21st to endNight
38%
516
10%
1596
10%
516
41%
516
19%
1113
May1st to 10thNight
39%
360
6%
1364
7%
360
42%
360
13%
993
May11th to 20thNight
44%
354
6%
1239
5%
354
46%
354
21%
820
May21st to endNight
40%
388
1%
1358
0%
388
41%
388
15%
977
June1st to 10thNight
40%
360
0%
1252
0%
360
40%
360
15%
919
June11th to 20thNight
40%
360
0%
1080
0%
360
40%
360
13%
851
June21st to endNight
50%
360
0%
1080
0%
360
50%
360
21%
763
July1st to 10thNight
53%
350
0%
1058
0%
350
53%
350
22%
729
July11th to 20thNight
50%
348
0%
1218
0%
348
50%
348
16%
854
July21st to endNight
59%
394
4%
1309
3%
372
60%
372
19%
853
August1st to 10thNight
55%
358
7%
1424
10%
356
56%
356
17%
918
August11th to 20thNight
56%
414
10%
1482
13%
414
58%
414
20%
949
August21st to endNight
54%
594
14%
1782
11%
594
57%
594
27%
1147
September1st to 10thNight
55%
645
14%
1725
10%
645
56%
645
27%
1171
September11th to 20thNight
51%
720
17%
1948
11%
720
54%
720
29%
1315
September21st to endNight
47%
720
20%
1980
11%
720
52%
720
30%
1271
October1st to 10thNight
43%
720
15%
2064
10%
720
48%
720
23%
1443
October11th to 20thNight
38%
720
16%
2340
10%
720
45%
720
21%
1570
October21st to endNight
36%
792
14%
2574
9%
792
43%
792
17%
1813
November1st to 10thNight
31%
866
14%
2540
8%
866
37%
866
15%
1927
November11th to 20thNight
27%
950
13%
2850
5%
950
34%
950
16%
2109
November21st to endNight
30%
950
10%
2850
5%
950
35%
950
18%
2086
December1st to 10thNight
32%
950
15%
2850
9%
950
37%
950
18%
2065
December11th to 20thNight
34%
949
12%
3478
8%
949
37%
949
14%
2564
December21st to endNight
32%
1034
10%
4965
6%
1026
39%
1026
12%
2855

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
11%9%47%6%46%6%6%8%33%
75174
Night
11%10%48%7%45%5%6%7%32%
74633
TransparencyDay
47%9%17%19%7%1
74850
Night
49%8%14%19%8%1
74475
SeeingDay
14%8%26%29%17%5%
14749
Night
15%7%28%34%15%2
23359

By Month

Percentage Cloud Cover NW (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
6%12%6%11%7%46%6%6%8%28%
1329
11th to 20thDay
9%11%5%10%7%36%6%5%8%30%
1298
21st to endDay
8%14%7%9%8%46%6%6%7%27%
1557
February1st to 10thDay
9%13%6%10%8%46%6%7%7%25%
1440
11th to 20thDay
6%14%7%10%8%46%6%7%6%26%
1483
21st to endDay
5%12%7%12%8%46%8%5%8%25%
1440
March1st to 10thDay
7%13%5%10%9%5%6%6%7%5%28%
1800
11th to 20thDay
9%10%47%6%46%6%6%9%34%
1914
21st to endDay
9%15%5%7%6%45%7%6%7%27%
2263
April1st to 10thDay
9%11%5%8%6%5%7%7%7%8%28%
2200
11th to 20thDay
13%13%47%7%36%5%6%7%29%
2310
21st to endDay
11%10%47%6%46%5%7%9%31%
2362
May1st to 10thDay
14%10%47%7%47%6%6%8%28%
2596
11th to 20thDay
10%7%26%6%36%5%6%8%40%
2654
21st to endDay
20%7%27%5%35%5%6%7%34%
2917
June1st to 10thDay
17%7%36%6%46%5%5%9%32%
2704
11th to 20thDay
19%8%48%8%5%6%6%7%8%23%
2880
21st to endDay
10%5%36%6%46%7%8%10%36%
2880
July1st to 10thDay
14%5%26%6%46%5%6%9%36%
2870
11th to 20thDay
13%5%25%6%46%5%8%9%36%
2700
21st to endDay
10%425%6%36%6%6%9%43%
2929
August1st to 10thDay
11%5%27%6%36%6%7%10%37%
2507
11th to 20thDay
9%5%246%35%6%7%9%44%
2417
21st to endDay
12%6%36%6%35%6%6%9%40%
2574
September1st to 10thDay
14%6%35%5%35%5%6%8%41%
2232
11th to 20thDay
16%6%25%43445%8%42%
2012
21st to endDay
12%7%26%7%345%5%7%41%
1980
October1st to 10thDay
11%11%37%5%45%5%46%38%
1894
11th to 20thDay
12%9%36%6%45%46%7%38%
1620
21st to endDay
9%13%48%8%45%6%5%6%32%
1782
November1st to 10thDay
11%15%6%9%8%445%6%7%26%
1516
11th to 20thDay
8%10%6%10%6%5%445%7%35%
1330
21st to endDay
8%10%49%8%6%7%6%6%8%28%
1330
December1st to 10thDay
9%12%6%10%8%46%5%6%8%27%
1330
11th to 20thDay
7%13%5%10%6%46%5%5%9%29%
1682
21st to endDay
6%9%47%7%45%6%7%8%37%
2442
January1st to 10thNight
7%14%6%10%9%5%5%5%5%6%28%
2836
11th to 20thNight
8%13%5%10%7%46%5%5%7%30%
2790
21st to endNight
8%16%6%9%7%45%5%6%6%27%
2814
February1st to 10thNight
9%11%6%11%8%5%5%5%5%6%28%
2520
11th to 20thNight
8%14%6%9%9%46%5%5%7%26%
2362
21st to endNight
6%13%5%9%8%5%5%5%5%7%31%
1814
March1st to 10thNight
7%11%5%10%8%5%6%6%7%7%29%
2160
11th to 20thNight
7%10%5%8%7%47%7%6%8%30%
2044
21st to endNight
9%15%7%9%6%45%5%6%7%26%
2089
April1st to 10thNight
11%11%5%8%8%5%6%7%7%7%25%
1759
11th to 20thNight
12%12%48%8%46%6%5%7%28%
1601
21st to endNight
13%11%37%6%36%5%6%8%33%
1596
May1st to 10thNight
18%10%46%7%46%6%7%7%27%
1364
11th to 20thNight
13%7%28%7%25%5%6%9%37%
1239
21st to endNight
20%7%47%6%45%5%45%31%
1358
June1st to 10thNight
20%9%47%7%45%5%6%7%27%
1252
11th to 20thNight
21%7%38%8%45%6%7%8%21%
1080
21st to endNight
14%6%25%7%5%6%5%8%10%32%
1080
July1st to 10thNight
15%6%35%7%36%5%6%8%36%
1088
11th to 20thNight
12%5%35%7%48%8%8%8%32%
1260
21st to endNight
12%437%5%47%6%6%7%40%
1386
August1st to 10thNight
13%5%36%6%5%6%5%6%8%37%
1432
11th to 20thNight
11%6%26%6%45%6%6%9%40%
1482
21st to endNight
12%6%26%4345%6%10%40%
1782
September1st to 10thNight
13%5%26%7%35%6%5%7%41%
1725
11th to 20thNight
15%7%25%5%3445%7%44%
1948
21st to endNight
12%6%26%5%3446%9%43%
1980
October1st to 10thNight
13%10%27%5%45%5%5%6%38%
2064
11th to 20thNight
12%9%38%6%35%5%48%37%
2340
21st to endNight
10%10%48%7%46%5%6%7%32%
2574
November1st to 10thNight
15%14%6%8%6%35%45%7%27%
2540
11th to 20thNight
10%12%5%8%7%46%5%5%6%31%
2850
21st to endNight
9%10%6%8%9%46%5%6%8%29%
2850
December1st to 10thNight
9%13%5%8%7%45%5%5%7%32%
2850
11th to 20thNight
8%13%6%9%8%5%5%5%5%7%29%
3510
21st to endNight
5%10%48%6%45%5%5%7%42%
5214

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
54%7%11%19%7%2
1329
11th to 20thDay
51%7%12%17%10%2
1298
21st to endDay
56%8%13%16%6%1
1557
February1st to 10thDay
54%8%15%14%8%1
1440
11th to 20thDay
55%9%13%15%8%
1491
21st to endDay
56%7%12%15%9%1
1440
March1st to 10thDay
55%8%13%17%7%1
1800
11th to 20thDay
45%7%14%22%11%1
1915
21st to endDay
54%9%16%16%5%
2263
April1st to 10thDay
50%10%16%16%7%1
2200
11th to 20thDay
52%8%15%18%6%1
2310
21st to endDay
47%9%16%19%6%2
2362
May1st to 10thDay
51%9%14%17%8%
2596
11th to 20thDay
41%8%14%26%10%1
2658
21st to endDay
48%9%16%19%9%
2918
June1st to 10thDay
48%9%18%20%5%
2704
11th to 20thDay
57%11%15%13%4
2880
21st to endDay
40%11%22%21%5%1
2880
July1st to 10thDay
43%11%19%22%5%1
2791
11th to 20thDay
43%11%25%19%2
2619
21st to endDay
35%12%26%24%4
2766
August1st to 10thDay
39%13%24%21%3
2490
11th to 20thDay
34%11%26%22%6%
2417
21st to endDay
39%10%21%21%8%
2574
September1st to 10thDay
40%9%20%23%6%1
2232
11th to 20thDay
40%7%17%27%9%
2012
21st to endDay
41%9%16%23%9%2
1980
October1st to 10thDay
47%8%15%22%8%1
1894
11th to 20thDay
43%9%15%22%10%
1620
21st to endDay
51%7%12%21%9%1
1782
November1st to 10thDay
57%7%14%16%5%1
1516
11th to 20thDay
49%9%15%18%10%
1330
21st to endDay
52%9%15%15%7%2
1330
December1st to 10thDay
54%8%12%15%8%2
1330
11th to 20thDay
50%10%15%17%6%1
1684
21st to endDay
40%8%14%19%16%3
2442
January1st to 10thNight
54%8%12%15%7%3
2836
11th to 20thNight
52%8%13%17%7%2
2790
21st to endNight
57%7%12%14%10%1
2814
February1st to 10thNight
55%6%12%18%8%2
2520
11th to 20thNight
57%6%13%15%9%1
2364
21st to endNight
51%7%11%19%10%1
1814
March1st to 10thNight
50%9%13%21%6%1
2160
11th to 20thNight
48%7%12%20%12%1
2044
21st to endNight
55%9%14%16%5%1
2089
April1st to 10thNight
54%10%12%15%7%1
1759
11th to 20thNight
52%8%13%18%6%2
1601
21st to endNight
46%9%14%21%8%1
1596
May1st to 10thNight
53%9%13%17%7%
1364
11th to 20thNight
44%8%13%22%13%
1239
21st to endNight
53%7%13%15%9%2
1358
June1st to 10thNight
54%8%12%19%6%
1252
11th to 20thNight
56%11%16%14%3
1080
21st to endNight
44%11%18%21%41
1080
July1st to 10thNight
42%11%19%21%6%1
1058
11th to 20thNight
43%15%22%15%5%
1218
21st to endNight
39%13%21%23%4
1309
August1st to 10thNight
42%11%22%21%3
1424
11th to 20thNight
40%11%20%23%6%1
1482
21st to endNight
38%9%19%25%8%
1782
September1st to 10thNight
40%9%18%24%8%2
1725
11th to 20thNight
41%7%15%27%8%3
1948
21st to endNight
38%7%16%24%14%2
1980
October1st to 10thNight
47%7%13%24%9%1
2064
11th to 20thNight
46%6%14%24%9%1
2340
21st to endNight
49%9%15%19%8%1
2574
November1st to 10thNight
57%6%11%17%8%
2540
11th to 20thNight
53%8%13%17%9%1
2850
21st to endNight
52%7%15%17%6%2
2850
December1st to 10thNight
52%7%11%19%9%2
2850
11th to 20thNight
54%8%15%18%6%
3507
21st to endNight
40%7%13%23%14%3
5214

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
7%8%27%29%21%8%
180
11th to 20thDay
9%13%25%30%19%5%
171
21st to endDay
15%10%27%32%11%6%
176
February1st to 10thDay
14%13%36%23%11%3
160
11th to 20thDay
17%9%40%25%9%1
198
21st to endDay
10%8%31%32%15%5%
306
March1st to 10thDay
12%13%31%31%11%2
420
11th to 20thDay
9%8%37%27%13%5%
420
21st to endDay
16%11%32%24%15%2
462
April1st to 10thDay
11%15%34%29%9%3
420
11th to 20thDay
17%10%23%33%14%3
412
21st to endDay
15%13%29%29%12%3
420
May1st to 10thDay
16%13%25%27%16%3
499
11th to 20thDay
12%7%23%31%22%5%
625
21st to endDay
17%6%24%29%17%7%
679
June1st to 10thDay
16%7%29%30%15%3
634
11th to 20thDay
19%7%22%29%18%4
810
21st to endDay
11%6%22%30%23%7%
810
July1st to 10thDay
15%320%34%22%6%
786
11th to 20thDay
14%422%31%24%5%
618
21st to endDay
12%5%19%30%24%11%
675
August1st to 10thDay
8%9%19%28%24%12%
447
11th to 20thDay
9%7%27%28%25%5%
437
21st to endDay
14%8%18%31%22%7%
495
September1st to 10thDay
17%8%28%24%20%4
450
11th to 20thDay
19%6%23%30%18%5%
450
21st to endDay
13%11%28%27%15%5%
450
October1st to 10thDay
16%8%24%29%18%4
390
11th to 20thDay
15%10%29%30%12%4
270
21st to endDay
13%15%34%26%10%2
297
November1st to 10thDay
19%7%30%30%11%3
264
11th to 20thDay
12%7%37%34%7%3
180
21st to endDay
9%7%40%30%9%4
180
December1st to 10thDay
13%10%29%33%11%5%
180
11th to 20thDay
11%13%34%28%13%1
180
21st to endDay
11%5%28%31%19%7%
198
January1st to 10thNight
11%8%32%33%13%2
950
11th to 20thNight
14%8%31%34%11%1
930
21st to endNight
15%15%30%29%9%1
834
February1st to 10thNight
13%10%27%31%15%3
720
11th to 20thNight
14%8%33%33%12%1
704
21st to endNight
11%5%29%35%17%4
592
March1st to 10thNight
13%6%30%33%16%3
720
11th to 20thNight
10%5%33%38%12%2
720
21st to endNight
15%5%26%36%15%3
792
April1st to 10thNight
14%9%31%31%14%1
679
11th to 20thNight
16%6%32%32%14%
533
21st to endNight
17%7%28%36%12%1
516
May1st to 10thNight
21%8%21%34%15%1
360
11th to 20thNight
14%5%28%34%18%1
354
21st to endNight
21%5%23%34%16%1
389
June1st to 10thNight
21%6%24%32%14%2
360
11th to 20thNight
21%5%18%36%18%3
360
21st to endNight
15%5%20%34%23%2
360
July1st to 10thNight
16%317%44%20%1
350
11th to 20thNight
14%222%39%21%2
348
21st to endNight
12%417%41%25%2
394
August1st to 10thNight
15%316%35%26%5%
358
11th to 20thNight
12%417%41%26%1
414
21st to endNight
14%419%40%23%1
594
September1st to 10thNight
15%218%43%20%2
645
11th to 20thNight
17%421%38%19%1
720
21st to endNight
14%428%36%15%2
720
October1st to 10thNight
18%426%36%15%1
720
11th to 20thNight
15%7%29%35%13%1
720
21st to endNight
13%8%31%35%12%1
792
November1st to 10thNight
20%9%29%30%10%2
866
11th to 20thNight
15%9%36%28%10%1
950
21st to endNight
13%7%38%31%9%2
950
December1st to 10thNight
14%10%34%29%12%2
950
11th to 20thNight
13%8%32%33%14%1
950
21st to endNight
12%5%33%33%14%3
1045
Page generated at 2024-01-13 17:28:28. Version ac07

Copyright 2024 Attilla Danko


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