Vernon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vernon clear sky chart from 2005-11-05 to 2017-03-22.

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
44%
14361
9%
45143
7%
14333
46%
14333
16%
33540

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
26%
746
4%
2593
4%
743
28%
743
6%
2254
January16th to endNight
29%
768
3%
2688
2%
768
31%
768
6%
2303
February1st to 15thNight
37%
699
6%
2399
5%
698
38%
698
9%
1940
February16th to endNight
44%
632
10%
1963
9%
632
46%
632
16%
1449
March1st to 15thNight
34%
720
5%
2160
4%
720
35%
720
12%
1733
March16th to endNight
38%
732
8%
1914
4%
732
40%
732
17%
1473
April1st to 15thNight
46%
659
8%
1649
4%
659
47%
659
19%
1262
April16th to endNight
41%
452
11%
1442
9%
452
44%
452
17%
1054
May1st to 15thNight
51%
329
11%
1320
18%
329
53%
329
17%
855
May16th to endNight
53%
342
6%
1319
6%
342
54%
342
16%
915
June1st to 15thNight
46%
330
2%
1075
0%
330
46%
330
18%
755
June16th to endNight
52%
330
3%
990
0%
330
52%
330
21%
691
July1st to 15thNight
67%
310
7%
1040
2%
310
69%
310
36%
557
July16th to endNight
72%
348
11%
1304
15%
326
76%
326
36%
624
August1st to 15thNight
77%
330
21%
1312
31%
328
80%
328
38%
618
August16th to endNight
69%
563
22%
1613
18%
563
71%
563
40%
899
September1st to 15thNight
67%
660
21%
1650
13%
660
69%
660
41%
1011
September16th to endNight
60%
656
19%
1778
14%
656
62%
656
29%
1161
October1st to 15thNight
54%
660
12%
1980
12%
660
55%
660
23%
1340
October16th to endNight
42%
704
9%
2276
7%
704
46%
704
16%
1658
November1st to 15thNight
36%
700
9%
2389
8%
700
38%
700
10%
1907
November16th to endNight
31%
816
5%
2616
3%
816
34%
816
7%
2213
December1st to 15thNight
32%
900
5%
2700
3%
900
34%
900
9%
2286
December16th to endNight
27%
975
3%
2973
2%
975
28%
975
7%
2582

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
10%8%37%7%46%5%6%7%33%
45753
Night
10%10%48%7%36%5%5%7%31%
45300
Cloud CoverDay
11%9%37%6%36%5%6%7%32%
45753
Night
11%10%47%6%35%5%5%7%31%
45303
TransparencyDay
49%11%15%15%6%
45414
Night
51%10%15%15%6%
45143
SeeingDay
14%13%27%26%14%2
5398
Night
15%7%23%31%19%3
14369

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 15thDay
15%13%6%8%6%5%7%6%6%6%15%
1351
16th to endDay
8%12%5%10%9%5%7%7%6%6%19%
1536
February1st to 15thDay
9%12%5%11%10%46%5%6%6%22%
1465
16th to endDay
9%10%5%7%8%47%6%8%8%24%
1511
March1st to 15thDay
10%10%48%9%5%6%5%7%8%23%
1800
16th to endDay
8%10%5%8%7%5%7%7%7%8%24%
2103
April1st to 15thDay
8%11%5%8%8%5%6%5%7%8%25%
1969
16th to endDay
9%10%47%7%46%5%6%8%29%
2186
May1st to 15thDay
9%8%37%6%45%5%5%7%36%
2301
16th to endDay
14%8%38%6%36%5%7%7%29%
2438
June1st to 15thDay
17%6%37%7%35%6%6%6%29%
2552
16th to endDay
13%6%36%7%46%6%6%7%32%
2640
July1st to 15thDay
5%3245%35%5%6%8%49%
2514
16th to endDay
5%213425%45%8%55%
2461
August1st to 15thDay
43135%35%6%5%9%51%
2310
16th to endDay
6%315%4345%6%7%50%
2236
September1st to 15thDay
6%415%5%3445%7%49%
1980
16th to endDay
11%5%35%5%345%5%8%39%
1851
October1st to 15thDay
10%7%36%7%46%5%6%7%34%
1650
16th to endDay
17%8%39%6%335%5%7%28%
1595
November1st to 15thDay
14%11%49%6%35%6%5%6%23%
1467
16th to endDay
10%11%7%9%9%5%9%7%6%6%17%
1332
December1st to 15thDay
7%13%7%12%12%5%7%6%5%6%16%
1260
16th to endDay
11%13%5%10%8%47%6%6%8%17%
1245
January1st to 15thNight
14%17%6%10%9%5%7%5%5%6%12%
2593
16th to endNight
9%15%6%14%10%47%45%7%13%
2688
February1st to 15thNight
13%15%5%9%6%36%6%5%6%21%
2387
16th to endNight
7%12%48%7%35%5%5%7%31%
1963
March1st to 15thNight
9%11%6%8%7%46%5%6%7%26%
2160
16th to endNight
8%9%5%8%5%46%5%6%8%31%
1910
April1st to 15thNight
9%6%45%7%5%5%6%6%9%34%
1649
16th to endNight
9%8%5%7%6%46%45%6%35%
1442
May1st to 15thNight
7%7%37%7%345%6%7%39%
1319
16th to endNight
12%7%36%5%35%5%6%9%33%
1319
June1st to 15thNight
14%5%35%6%346%7%8%34%
1075
16th to endNight
8%5%27%6%26%7%6%8%37%
990
July1st to 15thNight
3313425%5%5%8%56%
1110
16th to endNight
421232445%8%60%
1400
August1st to 15thNight
411232446%9%58%
1320
16th to endNight
4114335%45%8%56%
1613
September1st to 15thNight
6%22342445%7%57%
1650
16th to endNight
8%425%5%24448%47%
1778
October1st to 15thNight
8%6%25%6%35%5%5%7%43%
1980
16th to endNight
13%7%26%7%35%45%8%32%
2276
November1st to 15thNight
16%11%48%6%35%5%5%7%24%
2389
16th to endNight
12%13%7%10%9%46%5%5%5%17%
2616
December1st to 15thNight
10%15%6%12%8%47%6%5%6%17%
2700
16th to endNight
11%16%6%10%9%5%6%5%5%5%15%
2973

Percentage Cloud Cover SW (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
16%16%5%8%8%46%6%6%5%15%
1351
16th to endDay
11%14%48%7%5%8%6%5%7%18%
1536
February1st to 15thDay
11%14%5%10%9%45%6%6%421%
1465
16th to endDay
10%12%48%6%46%6%7%8%24%
1511
March1st to 15thDay
12%12%5%9%8%47%6%5%6%21%
1800
16th to endDay
11%11%5%8%8%45%6%6%6%23%
2103
April1st to 15thDay
11%12%5%8%7%48%46%8%23%
1969
16th to endDay
11%10%49%7%46%5%5%7%27%
2186
May1st to 15thDay
12%8%36%5%35%45%7%35%
2301
16th to endDay
15%8%47%7%36%6%6%6%27%
2438
June1st to 15thDay
18%7%37%6%35%5%5%6%28%
2552
16th to endDay
15%6%26%7%36%5%6%7%31%
2640
July1st to 15thDay
6%324435%5%6%8%48%
2514
16th to endDay
5%213325%45%7%56%
2461
August1st to 15thDay
43145%35%5%5%8%51%
2310
16th to endDay
6%414435%5%6%8%48%
2236
September1st to 15thDay
7%425%4245%5%7%50%
1980
16th to endDay
12%6%25%5%35%5%6%7%39%
1851
October1st to 15thDay
12%8%27%6%46%47%7%33%
1650
16th to endDay
18%9%36%6%245%5%7%28%
1595
November1st to 15thDay
17%13%5%8%6%45%5%6%5%22%
1467
16th to endDay
11%14%6%7%8%5%8%6%6%7%15%
1332
December1st to 15thDay
9%15%6%11%11%47%6%5%6%16%
1260
16th to endDay
14%14%5%9%7%45%5%8%6%18%
1245
January1st to 15thNight
18%17%6%9%7%46%45%5%14%
2592
16th to endNight
11%15%6%10%11%5%7%5%5%6%14%
2688
February1st to 15thNight
15%15%5%7%6%45%5%5%5%22%
2387
16th to endNight
8%14%48%5%35%5%5%7%30%
1963
March1st to 15thNight
12%12%5%9%6%46%5%5%7%24%
2160
16th to endNight
10%10%5%7%6%36%5%6%7%30%
1914
April1st to 15thNight
9%9%36%7%46%6%6%9%30%
1649
16th to endNight
10%8%38%7%46%5%46%34%
1442
May1st to 15thNight
6%10%28%6%35%5%5%6%38%
1319
16th to endNight
13%7%37%445%5%5%9%32%
1319
June1st to 15thNight
15%6%46%6%235%5%8%34%
1075
16th to endNight
10%6%36%5%36%6%6%7%37%
990
July1st to 15thNight
4313335%46%10%54%
1110
16th to endNight
5%2132346%8%60%
1400
August1st to 15thNight
5%21332445%9%57%
1320
16th to endNight
431342446%7%56%
1613
September1st to 15thNight
6%41342445%7%55%
1650
16th to endNight
10%425%5%335%48%46%
1778
October1st to 15thNight
10%6%26%5%36%45%6%42%
1980
16th to endNight
15%7%36%7%35%5%5%6%32%
2276
November1st to 15thNight
19%13%46%5%4446%6%24%
2389
16th to endNight
15%14%6%8%7%46%6%5%5%18%
2616
December1st to 15thNight
11%16%6%10%8%47%5%46%19%
2700
16th to endNight
12%17%7%9%8%46%5%5%5%15%
2973

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
65%16%12%4
1351
16th to endDay
61%14%15%6%1
1536
February1st to 15thDay
61%13%13%8%2
1465
16th to endDay
54%12%16%11%4
1511
March1st to 15thDay
59%13%15%9%2
1800
16th to endDay
57%11%17%9%3
2103
April1st to 15thDay
57%11%15%14%1
1969
16th to endDay
54%10%15%14%4
2186
May1st to 15thDay
46%9%15%18%10%
2301
16th to endDay
54%11%16%14%3
2442
June1st to 15thDay
54%10%13%13%6%1
2552
16th to endDay
49%11%14%15%8%
2640
July1st to 15thDay
32%10%14%21%16%3
2355
16th to endDay
26%8%18%26%18%2
2294
August1st to 15thDay
29%9%19%28%11%2
2293
16th to endDay
31%10%16%26%13%1
2236
September1st to 15thDay
31%9%14%29%14%1
1980
16th to endDay
41%10%17%20%7%1
1851
October1st to 15thDay
45%10%20%18%4
1650
16th to endDay
54%11%18%12%1
1595
November1st to 15thDay
61%12%13%9%2
1467
16th to endDay
65%13%12%7%1
1332
December1st to 15thDay
66%12%12%8%
1260
16th to endDay
62%15%14%6%1
1245
January1st to 15thNight
70%10%11%5%1
2593
16th to endNight
67%12%11%6%1
2688
February1st to 15thNight
60%11%13%10%3
2399
16th to endNight
51%9%18%14%5%
1963
March1st to 15thNight
58%11%16%10%2
2160
16th to endNight
51%10%18%15%4
1914
April1st to 15thNight
46%13%19%14%5%
1649
16th to endNight
49%10%15%20%4
1442
May1st to 15thNight
43%9%14%18%12%
1320
16th to endNight
48%9%18%18%5%
1319
June1st to 15thNight
47%9%13%18%8%1
1075
16th to endNight
42%11%16%19%9%
990
July1st to 15thNight
26%7%18%24%18%4
1040
16th to endNight
21%8%15%30%20%2
1304
August1st to 15thNight
22%6%19%31%17%3
1312
16th to endNight
24%8%17%29%18%1
1613
September1st to 15thNight
26%8%15%26%19%2
1650
16th to endNight
35%9%14%26%9%3
1778
October1st to 15thNight
40%10%18%20%9%
1980
16th to endNight
50%9%18%18%2
2276
November1st to 15thNight
59%11%12%11%4
2389
16th to endNight
66%11%11%8%2
2616
December1st to 15thNight
64%11%13%8%1
2700
16th to endNight
67%12%12%6%
2973

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
11%115%30%26%15%
60
16th to endDay
23%326%28%14%4
64
February1st to 15thDay
13%18%30%26%8%3
125
16th to endDay
11%13%29%30%11%2
227
March1st to 15thDay
22%25%32%15%3
270
16th to endDay
16%25%33%20%5%
250
April1st to 15thDay
20%20%29%17%12%
209
16th to endDay
12%26%29%19%8%3
210
May1st to 15thDay
15%17%31%24%7%2
228
16th to endDay
17%14%21%20%20%5%
313
June1st to 15thDay
18%11%22%27%17%1
497
16th to endDay
14%9%27%28%16%2
585
July1st to 15thDay
9%11%23%31%22%1
439
16th to endDay
6%10%32%33%14%2
271
August1st to 15thDay
5%9%26%34%19%4
255
16th to endDay
9%11%28%36%11%2
268
September1st to 15thDay
12%12%28%24%18%3
255
16th to endDay
17%11%33%21%13%1
255
October1st to 15thDay
17%16%29%21%12%1
255
16th to endDay
20%326%26%19%3
107
November1st to 15thDay
29%11%28%18%12%
71
16th to endDay
15%6%31%20%13%13%
60
December1st to 15thDay
20%10%21%20%21%6%
60
16th to endDay
10%6%29%35%12%4
64
January1st to 15thNight
24%10%24%24%13%1
747
16th to endNight
17%6%27%29%16%3
768
February1st to 15thNight
21%9%18%31%15%2
704
16th to endNight
14%6%25%29%19%3
632
March1st to 15thNight
17%12%27%29%11%1
720
16th to endNight
13%10%28%30%14%3
732
April1st to 15thNight
11%11%22%30%20%2
659
16th to endNight
13%6%28%34%15%1
452
May1st to 15thNight
10%7%19%39%21%
330
16th to endNight
16%418%29%27%3
343
June1st to 15thNight
16%325%29%22%2
330
16th to endNight
11%422%40%18%3
330
July1st to 15thNight
6%317%34%35%2
310
16th to endNight
7%216%34%37%2
348
August1st to 15thNight
6%10%30%43%7%
330
16th to endNight
6%315%39%31%4
563
September1st to 15thNight
6%416%28%33%11%
660
16th to endNight
13%5%16%33%26%4
656
October1st to 15thNight
12%5%20%34%23%3
660
16th to endNight
18%8%22%31%17%3
704
November1st to 15thNight
23%11%23%31%9%1
700
16th to endNight
20%10%23%26%13%4
816
December1st to 15thNight
16%8%28%31%13%1
900
16th to endNight
20%8%31%29%9%1
975
Page generated at 2017-03-23 04:36:11. Version ac04

Copyright 2017 A. Danko


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