Virden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Virden clear sky chart from 2005-11-06 to 2024-02-05.

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%
25194
13%
80501
8%
25116
44%
25116
21%
54288

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
32%
937
10%
4688
8%
926
37%
926
10%
3546
January11th to 20thNight
29%
945
8%
4383
6%
930
33%
930
9%
3338
January21st to endNight
24%
1031
8%
4825
4%
1023
30%
1023
9%
3405
February1st to 10thNight
31%
923
13%
2583
5%
923
38%
923
19%
1856
February11th to 20thNight
39%
807
16%
2264
9%
807
44%
807
22%
1581
February21st to endNight
42%
592
19%
1776
12%
592
49%
592
24%
1212
March1st to 10thNight
34%
720
11%
2160
7%
720
38%
720
18%
1602
March11th to 20thNight
42%
626
19%
2066
14%
626
49%
626
23%
1342
March21st to endNight
39%
594
13%
2066
12%
594
45%
594
19%
1408
April1st to 10thNight
40%
540
20%
1800
16%
540
52%
540
28%
1067
April11th to 20thNight
34%
533
17%
1631
12%
533
42%
533
21%
1122
April21st to endNight
38%
540
14%
1620
8%
540
43%
540
23%
1091
May1st to 10thNight
43%
540
15%
1487
7%
540
46%
540
29%
959
May11th to 20thNight
43%
531
15%
1352
7%
531
45%
531
32%
886
May21st to endNight
43%
584
11%
1358
5%
582
46%
582
30%
960
June1st to 10thNight
42%
540
8%
1260
4%
540
45%
540
36%
834
June11th to 20thNight
41%
540
4%
1260
3%
540
43%
540
31%
861
June21st to endNight
52%
540
6%
1260
4%
540
55%
540
36%
839
July1st to 10thNight
62%
525
7%
1225
5%
525
63%
525
49%
730
July11th to 20thNight
54%
522
12%
1259
5%
522
59%
522
45%
754
July21st to endNight
67%
591
16%
1488
8%
558
69%
558
48%
818
August1st to 10thNight
61%
537
18%
1424
9%
534
65%
534
46%
789
August11th to 20thNight
62%
534
21%
1531
14%
534
66%
534
41%
850
August21st to endNight
54%
594
25%
1806
21%
594
62%
594
39%
987
September1st to 10thNight
52%
540
21%
1800
19%
540
61%
540
37%
959
September11th to 20thNight
45%
540
20%
1937
17%
540
54%
540
29%
1063
September21st to endNight
41%
540
22%
1980
18%
540
50%
540
24%
1180
October1st to 10thNight
38%
562
18%
2002
14%
562
45%
562
22%
1241
October11th to 20thNight
38%
900
18%
2340
9%
900
43%
900
27%
1585
October21st to endNight
31%
990
15%
2574
5%
990
37%
990
21%
1837
November1st to 10thNight
30%
925
15%
2405
5%
925
36%
925
21%
1745
November11th to 20thNight
28%
950
13%
2745
5%
950
34%
950
17%
2037
November21st to endNight
29%
950
12%
2850
5%
950
36%
950
18%
2020
December1st to 10thNight
32%
950
10%
2850
5%
950
37%
950
16%
2096
December11th to 20thNight
24%
950
8%
3486
3%
949
30%
949
9%
2702
December21st to endNight
27%
1031
8%
4960
6%
1026
33%
1026
11%
2986

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%8%48%7%45%5%6%8%35%
77783
Night
9%9%48%7%45%5%6%7%36%
81072
TransparencyDay
47%5%15%24%9%1
77500
Night
46%5%15%23%10%1
80936
SeeingDay
15%8%28%30%16%4
15103
Night
14%7%29%35%13%2
25245

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
5%15%8%14%11%45%8%7%7%16%
2219
11th to 20thDay
48%5%15%14%6%9%12%6%6%15%
2516
21st to endDay
8%11%6%12%8%46%5%5%7%29%
2794
February1st to 10thDay
9%12%412%8%6%5%5%8%7%24%
1472
11th to 20thDay
7%12%5%11%8%5%8%6%6%7%25%
1599
21st to endDay
7%11%6%10%9%5%6%9%6%7%25%
1480
March1st to 10thDay
10%14%9%11%11%46%45%7%19%
1800
11th to 20thDay
8%11%5%8%8%5%6%5%6%7%29%
1892
21st to endDay
11%12%5%11%9%46%5%6%8%25%
2289
April1st to 10thDay
8%10%48%6%345%6%8%38%
2160
11th to 20thDay
14%12%48%6%35%5%48%30%
2279
21st to endDay
13%9%47%7%35%5%5%9%35%
2340
May1st to 10thDay
14%7%35%6%3446%7%42%
2470
11th to 20thDay
14%8%36%5%3446%8%38%
2544
21st to endDay
20%7%36%5%35%6%49%32%
2918
June1st to 10thDay
14%5%35%6%35%5%6%9%39%
2700
11th to 20thDay
16%6%37%6%36%6%6%9%33%
2700
21st to endDay
12%5%36%6%46%5%6%9%39%
2700
July1st to 10thDay
7%425%6%35%6%6%10%48%
2700
11th to 20thDay
8%5%25%6%35%5%7%9%46%
2656
21st to endDay
6%4144345%7%10%52%
2742
August1st to 10thDay
10%5%25%435%6%6%8%46%
2507
11th to 20thDay
9%5%245%35%6%6%10%45%
2370
21st to endDay
10%4235%3446%8%50%
2548
September1st to 10thDay
10%5%25%4345%47%50%
2160
11th to 20thDay
13%6%25%5%3445%7%46%
2022
21st to endDay
15%6%25%43445%7%46%
1980
October1st to 10thDay
16%11%47%5%34446%36%
1936
11th to 20thDay
13%8%36%6%35%5%47%39%
1620
21st to endDay
13%11%6%9%6%35%5%5%5%31%
1782
November1st to 10thDay
18%11%6%10%7%35%446%28%
1673
11th to 20thDay
8%15%6%11%10%445%5%6%27%
1434
21st to endDay
9%13%6%10%8%5%5%5%47%28%
1330
December1st to 10thDay
6%12%8%13%11%6%6%6%46%23%
1330
11th to 20thDay
8%14%7%13%10%6%6%6%5%5%18%
1679
21st to endDay
6%8%37%8%5%6%6%6%7%37%
2442
January1st to 10thNight
6%13%6%15%9%5%6%5%5%7%22%
4733
11th to 20thNight
6%7%5%15%12%6%8%8%8%8%17%
4392
21st to endNight
8%11%6%14%9%45%5%5%6%27%
4873
February1st to 10thNight
8%11%6%9%7%46%6%7%8%28%
2583
11th to 20thNight
6%10%49%8%48%5%6%8%33%
2263
21st to endNight
7%9%5%9%8%45%6%6%7%35%
1776
March1st to 10thNight
11%12%6%9%7%5%5%6%5%7%27%
2160
11th to 20thNight
6%9%5%7%7%45%6%6%7%37%
2066
21st to endNight
10%11%5%8%7%35%5%6%7%34%
2066
April1st to 10thNight
5%8%36%6%345%7%8%44%
1800
11th to 20thNight
14%10%48%6%3445%8%33%
1631
21st to endNight
15%8%25%5%37%6%6%6%37%
1620
May1st to 10thNight
10%8%26%6%35%5%6%8%42%
1487
11th to 20thNight
12%7%25%6%25%5%5%9%42%
1352
21st to endNight
19%5%26%33446%8%40%
1358
June1st to 10thNight
14%424335%5%7%9%44%
1260
11th to 20thNight
14%5%15%5%35%5%6%10%41%
1260
21st to endNight
11%425%5%35%5%7%11%43%
1260
July1st to 10thNight
5%5%2432445%10%55%
1260
11th to 20thNight
6%3244245%7%9%56%
1301
21st to endNight
3313335%46%8%60%
1576
August1st to 10thNight
5%3144345%6%9%56%
1432
11th to 20thNight
6%325%43446%9%55%
1531
21st to endNight
9%423424447%56%
1806
September1st to 10thNight
9%5%143345%6%8%53%
1800
11th to 20thNight
11%6%3442446%8%48%
1937
21st to endNight
13%7%35%5%3346%7%43%
1980
October1st to 10thNight
14%9%35%5%3345%6%42%
2002
11th to 20thNight
13%8%36%6%45%45%7%41%
2340
21st to endNight
11%10%48%7%35%46%6%35%
2574
November1st to 10thNight
13%10%48%6%45%45%7%32%
2405
11th to 20thNight
10%11%5%10%9%45%5%5%6%30%
2745
21st to endNight
9%11%5%8%7%45%6%6%7%33%
2850
December1st to 10thNight
7%10%6%10%9%6%7%6%6%7%27%
2850
11th to 20thNight
9%15%7%12%9%5%6%6%5%6%20%
3518
21st to endNight
7%8%47%7%47%6%7%8%35%
5225

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
64%7%12%13%4
2219
11th to 20thDay
67%6%11%13%4
2540
21st to endDay
56%410%23%6%
2794
February1st to 10thDay
58%413%18%6%
1472
11th to 20thDay
56%5%13%18%8%
1608
21st to endDay
55%7%12%19%8%
1480
March1st to 10thDay
66%5%13%12%5%
1800
11th to 20thDay
53%6%13%21%7%
1894
21st to endDay
56%5%15%19%5%
2289
April1st to 10thDay
43%5%16%24%11%1
2160
11th to 20thDay
53%5%11%19%11%1
2279
21st to endDay
47%5%16%22%8%1
2340
May1st to 10thDay
41%413%27%12%2
2470
11th to 20thDay
44%5%12%26%13%1
2548
21st to endDay
49%5%13%22%10%1
2918
June1st to 10thDay
40%6%20%24%9%2
2700
11th to 20thDay
47%6%16%21%9%1
2700
21st to endDay
40%7%20%26%7%1
2700
July1st to 10thDay
29%7%21%33%9%1
2626
11th to 20thDay
33%7%18%30%11%1
2575
21st to endDay
26%6%20%38%10%1
2590
August1st to 10thDay
34%5%19%31%10%1
2491
11th to 20thDay
32%6%22%31%8%1
2370
21st to endDay
32%415%36%12%1
2548
September1st to 10thDay
34%416%31%13%1
2160
11th to 20thDay
39%5%18%27%10%1
2022
21st to endDay
39%413%32%12%
1980
October1st to 10thDay
50%314%24%8%1
1936
11th to 20thDay
44%5%15%26%9%
1620
21st to endDay
53%5%15%20%7%1
1782
November1st to 10thDay
59%412%18%7%1
1673
11th to 20thDay
58%316%15%6%1
1434
21st to endDay
57%5%15%17%5%
1330
December1st to 10thDay
62%5%12%15%5%
1330
11th to 20thDay
64%7%13%13%3
1680
21st to endDay
45%5%12%23%14%2
2442
January1st to 10thNight
61%5%11%18%5%
4733
11th to 20thNight
62%6%15%13%4
4430
21st to endNight
57%5%13%19%5%
4873
February1st to 10thNight
52%415%19%10%1
2583
11th to 20thNight
48%5%14%21%12%1
2264
21st to endNight
47%414%24%11%
1776
March1st to 10thNight
56%5%15%20%5%
2160
11th to 20thNight
45%415%27%8%1
2066
21st to endNight
49%5%17%21%8%
2066
April1st to 10thNight
36%6%12%28%17%2
1800
11th to 20thNight
51%310%22%14%1
1631
21st to endNight
46%5%15%21%12%2
1620
May1st to 10thNight
40%5%13%25%17%1
1487
11th to 20thNight
39%5%12%27%15%2
1352
21st to endNight
43%5%14%25%13%
1358
June1st to 10thNight
36%5%17%26%13%2
1260
11th to 20thNight
39%7%18%21%13%2
1260
21st to endNight
33%9%20%31%7%1
1260
July1st to 10thNight
25%5%20%34%15%1
1225
11th to 20thNight
25%7%19%33%14%2
1259
21st to endNight
22%6%18%36%16%2
1488
August1st to 10thNight
23%6%21%35%13%1
1424
11th to 20thNight
26%6%20%36%10%2
1531
21st to endNight
27%5%14%35%17%2
1806
September1st to 10thNight
28%5%14%34%18%2
1800
11th to 20thNight
33%5%18%29%14%1
1937
21st to endNight
40%412%31%11%1
1980
October1st to 10thNight
43%418%24%9%1
2002
11th to 20thNight
44%413%28%11%
2340
21st to endNight
48%6%15%23%8%
2574
November1st to 10thNight
50%6%14%21%8%2
2405
11th to 20thNight
54%7%15%18%6%1
2745
21st to endNight
50%7%18%19%7%
2850
December1st to 10thNight
55%5%16%17%6%
2850
11th to 20thNight
64%414%12%5%
3516
21st to endNight
45%6%12%21%14%2
5225

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
12%8%29%32%15%4
270
11th to 20thDay
8%9%31%39%11%2
270
21st to endDay
16%9%26%34%13%2
297
February1st to 10thDay
12%8%37%33%10%1
252
11th to 20thDay
13%5%32%34%13%4
240
21st to endDay
5%5%31%36%19%3
198
March1st to 10thDay
13%8%35%26%14%3
240
11th to 20thDay
12%6%34%29%17%3
240
21st to endDay
18%10%28%28%14%3
375
April1st to 10thDay
14%12%35%29%9%2
420
11th to 20thDay
21%9%27%28%13%
557
21st to endDay
17%9%31%29%15%1
600
May1st to 10thDay
15%10%27%32%14%2
603
11th to 20thDay
17%9%28%25%17%4
625
21st to endDay
21%8%25%28%15%4
679
June1st to 10thDay
14%9%26%29%17%5%
630
11th to 20thDay
17%8%33%26%12%3
630
21st to endDay
13%7%23%33%20%4
630
July1st to 10thDay
9%6%22%36%20%7%
621
11th to 20thDay
12%7%29%29%19%4
618
21st to endDay
6%6%23%35%22%7%
684
August1st to 10thDay
11%5%25%32%20%7%
626
11th to 20thDay
12%423%28%26%7%
615
21st to endDay
12%5%24%34%20%4
667
September1st to 10thDay
12%9%36%25%14%4
450
11th to 20thDay
16%10%25%34%13%2
312
21st to endDay
20%11%28%24%15%1
270
October1st to 10thDay
24%9%22%27%14%4
270
11th to 20thDay
18%10%30%29%9%4
270
21st to endDay
21%8%40%23%6%3
297
November1st to 10thDay
24%10%26%26%12%1
270
11th to 20thDay
17%11%36%25%10%1
270
21st to endDay
16%13%31%32%6%2
270
December1st to 10thDay
11%9%34%29%15%3
270
11th to 20thDay
18%6%40%27%8%1
270
21st to endDay
13%6%31%31%16%3
297
January1st to 10thNight
13%8%30%37%10%1
950
11th to 20thNight
15%9%31%34%9%1
950
21st to endNight
12%9%34%33%11%1
1045
February1st to 10thNight
12%8%32%33%12%2
923
11th to 20thNight
11%7%29%38%12%3
812
21st to endNight
11%427%38%17%3
592
March1st to 10thNight
17%7%27%31%14%4
720
11th to 20thNight
10%6%33%38%12%2
626
21st to endNight
16%427%37%14%3
594
April1st to 10thNight
9%8%36%35%12%
540
11th to 20thNight
18%7%31%33%10%1
533
21st to endNight
18%7%28%34%12%
540
May1st to 10thNight
14%7%29%37%13%1
540
11th to 20thNight
15%5%30%35%14%
531
21st to endNight
23%425%34%14%
584
June1st to 10thNight
17%432%31%16%1
540
11th to 20thNight
16%6%32%33%13%
540
21st to endNight
14%326%39%18%1
540
July1st to 10thNight
8%322%43%22%1
525
11th to 20thNight
8%427%43%16%2
522
21st to endNight
6%221%49%19%3
591
August1st to 10thNight
7%323%45%21%1
537
11th to 20thNight
8%419%41%24%3
534
21st to endNight
13%424%41%17%2
594
September1st to 10thNight
11%426%36%19%3
540
11th to 20thNight
14%6%31%36%13%1
540
21st to endNight
16%8%28%34%12%1
540
October1st to 10thNight
19%7%31%29%13%1
562
11th to 20thNight
18%9%25%35%12%1
900
21st to endNight
16%10%33%32%9%1
990
November1st to 10thNight
19%10%32%30%9%1
925
11th to 20thNight
15%9%35%29%9%2
950
21st to endNight
14%12%32%32%8%1
950
December1st to 10thNight
11%8%33%31%14%3
950
11th to 20thNight
17%9%30%33%9%2
950
21st to endNight
15%7%31%33%12%3
1045
Page generated at 2024-02-02 04:20:27. Version ac07

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