Harrisonburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harrisonburg clear sky chart from 2005-11-05 to 2018-10-27.

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%
16828
20%
51348
13%
16792
52%
16792
25%
32736

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
29%
776
22%
2522
10%
776
44%
776
20%
1564
January16th to endNight
24%
832
21%
2704
10%
832
40%
832
21%
1707
February1st to 15thNight
27%
761
19%
2482
7%
761
42%
761
21%
1557
February16th to endNight
21%
683
22%
2071
9%
683
36%
683
20%
1343
March1st to 15thNight
28%
780
22%
2145
10%
780
40%
780
25%
1382
March16th to endNight
30%
832
18%
2288
9%
832
38%
832
23%
1541
April1st to 15thNight
29%
778
18%
1979
6%
778
37%
778
25%
1335
April16th to endNight
41%
733
19%
1889
9%
733
47%
733
29%
1262
May1st to 15thNight
48%
585
16%
1755
10%
585
52%
585
22%
1199
May16th to endNight
56%
523
15%
1742
12%
523
59%
523
24%
1124
June1st to 15thNight
65%
390
17%
1560
21%
390
69%
390
25%
901
June16th to endNight
71%
390
18%
1560
20%
390
75%
390
25%
901
July1st to 15thNight
66%
512
13%
1622
13%
512
68%
512
27%
1022
July16th to endNight
77%
612
15%
1739
13%
579
79%
579
33%
1070
August1st to 15thNight
70%
575
17%
1715
14%
572
70%
572
28%
1134
August16th to endNight
65%
761
17%
2003
13%
761
66%
761
29%
1354
September1st to 15thNight
60%
780
24%
1956
16%
780
63%
780
33%
1300
September16th to endNight
52%
777
21%
2177
17%
777
55%
777
26%
1460
October1st to 15thNight
51%
780
21%
2340
20%
780
56%
780
26%
1496
October16th to endNight
40%
816
28%
2447
18%
816
55%
816
31%
1437
November1st to 15thNight
45%
760
26%
2308
18%
760
56%
760
28%
1401
November16th to endNight
37%
780
23%
2730
16%
780
50%
780
23%
1606
December1st to 15thNight
33%
780
17%
2730
10%
780
44%
780
17%
1784
December16th to endNight
33%
832
21%
2884
11%
832
46%
832
19%
1856

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
13%5%25%5%35%5%5%7%40%
52176
Night
12%5%2443445%7%44%
51541
Cloud CoverDay
13%5%25%5%35%5%5%7%40%
52186
Night
12%5%2442445%7%44%
51545
TransparencyDay
41%7%12%20%14%2
51887
Night
38%7%12%22%15%3
51348
SeeingDay
17%10%22%24%16%8%
7046
Night
16%9%24%31%16%2
16837

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
12%6%25%5%345%5%7%39%
1746
16th to endDay
13%7%25%434445%44%
1872
February1st to 15thDay
12%8%46%5%345%46%39%
1710
16th to endDay
14%5%36%42445%6%41%
1685
March1st to 15thDay
13%6%25%425%435%45%
2134
16th to endDay
13%9%25%5%345%5%6%38%
2288
April1st to 15thDay
12%435%5%34446%46%
2297
16th to endDay
16%5%25%433347%44%
2357
May1st to 15thDay
16%6%25%5%35%5%5%8%35%
2526
16th to endDay
14%5%25%6%46%5%6%8%34%
2723
June1st to 15thDay
11%3245%45%6%6%9%39%
2730
16th to endDay
7%425%6%35%6%7%12%37%
2730
July1st to 15thDay
9%426%6%36%6%7%9%35%
2574
16th to endDay
8%426%6%47%7%8%10%33%
2673
August1st to 15thDay
10%5%26%7%45%6%7%8%34%
2487
16th to endDay
10%4246%36%7%7%8%36%
2535
September1st to 15thDay
14%5%245%345%5%6%43%
2331
16th to endDay
17%6%26%5%3445%5%37%
2111
October1st to 15thDay
16%5%25%423446%44%
1950
16th to endDay
13%413423446%50%
2034
November1st to 15thDay
12%6%23224346%51%
1874
16th to endDay
14%424424336%48%
1560
December1st to 15thDay
15%6%24425%35%7%42%
1560
16th to endDay
16%7%26%424346%40%
1689
January1st to 15thNight
13%5%2433445%6%45%
2522
16th to endNight
14%8%25%424345%43%
2704
February1st to 15thNight
12%7%243245%6%6%44%
2480
16th to endNight
11%6%25%5%3446%6%42%
2071
March1st to 15thNight
13%5%24434346%46%
2133
16th to endNight
15%6%25%423447%43%
2288
April1st to 15thNight
13%6%25%3345%6%5%44%
1979
16th to endNight
14%42342445%7%45%
1889
May1st to 15thNight
14%6%15%435%446%41%
1755
16th to endNight
13%5%2442446%8%42%
1740
June1st to 15thNight
8%415%425%6%6%10%44%
1560
16th to endNight
7%315%425%6%6%8%47%
1560
July1st to 15thNight
8%425%4345%7%9%43%
1712
16th to endNight
4324435%5%8%12%44%
1847
August1st to 15thNight
8%426%6%345%6%8%42%
1726
16th to endNight
9%5%146%35%6%6%10%39%
2003
September1st to 15thNight
12%5%1442445%7%46%
1956
16th to endNight
16%6%24434445%43%
2177
October1st to 15thNight
15%5%24335%346%43%
2340
16th to endNight
12%413423445%52%
2447
November1st to 15thNight
12%6%24323445%50%
2308
16th to endNight
14%5%23324345%49%
2730
December1st to 15thNight
14%6%35%5%35%5%3441%
2730
16th to endNight
14%6%35%5%35%446%41%
2884

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
13%6%25%5%345%6%7%39%
1746
16th to endDay
14%7%34434445%44%
1872
February1st to 15thDay
12%8%45%6%3445%6%39%
1710
16th to endDay
14%6%36%4245%5%6%40%
1685
March1st to 15thDay
14%6%25%425%345%45%
2145
16th to endDay
14%8%35%4345%5%6%38%
2287
April1st to 15thDay
12%5%245%34446%46%
2297
16th to endDay
16%5%15%434347%43%
2357
May1st to 15thDay
16%6%25%6%35%5%5%8%35%
2526
16th to endDay
13%6%26%6%36%5%6%8%35%
2723
June1st to 15thDay
11%415%5%36%6%6%9%40%
2730
16th to endDay
8%325%5%36%5%7%12%38%
2730
July1st to 15thDay
10%425%6%36%6%7%9%35%
2574
16th to endDay
8%5%25%6%48%7%7%10%34%
2673
August1st to 15thDay
10%5%26%7%45%6%7%9%33%
2487
16th to endDay
10%5%25%5%46%7%7%9%36%
2535
September1st to 15thDay
13%5%24435%45%6%44%
2331
16th to endDay
17%6%26%5%35%45%6%36%
2111
October1st to 15thDay
16%5%25%423445%44%
1950
16th to endDay
13%5%13423446%50%
2034
November1st to 15thDay
12%6%23324246%51%
1874
16th to endDay
14%424424336%48%
1560
December1st to 15thDay
15%5%24325%35%6%43%
1560
16th to endDay
16%7%25%5%23346%39%
1689
January1st to 15thNight
13%5%2443445%6%44%
2522
16th to endNight
14%8%34424346%43%
2704
February1st to 15thNight
12%7%24325%5%5%6%44%
2473
16th to endNight
11%6%25%5%245%6%6%41%
2071
March1st to 15thNight
13%5%24433446%46%
2145
16th to endNight
15%6%34424346%43%
2288
April1st to 15thNight
13%5%24435%46%5%43%
1979
16th to endNight
14%42442445%7%45%
1889
May1st to 15thNight
15%5%25%435%447%40%
1754
16th to endNight
14%5%235%245%6%8%41%
1740
June1st to 15thNight
7%4245%25%5%7%10%44%
1560
16th to endNight
6%415%4247%6%8%47%
1560
July1st to 15thNight
8%5%25%425%5%7%9%43%
1712
16th to endNight
4313436%5%8%12%45%
1847
August1st to 15thNight
8%5%25%6%35%5%7%7%42%
1726
16th to endNight
8%5%245%45%5%7%10%38%
2003
September1st to 15thNight
12%5%1442445%8%46%
1956
16th to endNight
15%6%24434445%42%
2177
October1st to 15thNight
14%5%15%424446%44%
2340
16th to endNight
12%42342335%5%51%
2447
November1st to 15thNight
12%6%24323445%50%
2308
16th to endNight
13%6%23424446%48%
2730
December1st to 15thNight
14%7%25%5%25%5%35%41%
2730
16th to endNight
13%6%25%5%345%46%40%
2884

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
42%7%11%17%16%4
1747
16th to endDay
42%410%21%16%3
1872
February1st to 15thDay
44%5%10%20%15%3
1712
16th to endDay
42%6%11%21%14%2
1685
March1st to 15thDay
42%5%9%21%16%4
2145
16th to endDay
46%7%10%18%14%3
2288
April1st to 15thDay
38%6%10%21%17%5%
2297
16th to endDay
41%6%10%18%16%5%
2357
May1st to 15thDay
47%8%13%17%11%1
2526
16th to endDay
45%10%14%19%9%1
2727
June1st to 15thDay
39%10%15%22%11%1
2730
16th to endDay
37%11%16%20%12%1
2730
July1st to 15thDay
41%10%14%18%12%2
2435
16th to endDay
42%11%14%18%10%1
2518
August1st to 15thDay
43%11%14%19%10%
2474
16th to endDay
42%11%14%20%9%
2535
September1st to 15thDay
40%8%12%18%16%3
2331
16th to endDay
47%7%9%19%15%1
2111
October1st to 15thDay
41%5%10%24%14%4
1950
16th to endDay
34%5%8%27%20%3
2034
November1st to 15thDay
35%410%22%21%6%
1874
16th to endDay
37%49%25%20%3
1560
December1st to 15thDay
40%6%12%22%14%3
1560
16th to endDay
45%5%11%23%12%1
1689
January1st to 15thNight
39%5%11%18%18%6%
2522
16th to endNight
42%411%22%17%2
2704
February1st to 15thNight
39%6%12%23%15%3
2482
16th to endNight
40%6%12%21%15%2
2071
March1st to 15thNight
39%5%11%25%14%3
2145
16th to endNight
41%6%13%20%16%2
2288
April1st to 15thNight
39%6%11%22%15%3
1979
16th to endNight
37%7%12%18%18%4
1889
May1st to 15thNight
43%8%13%20%11%2
1755
16th to endNight
39%9%16%23%10%1
1742
June1st to 15thNight
32%10%18%24%12%1
1560
16th to endNight
31%11%16%20%18%1
1560
July1st to 15thNight
34%11%18%20%12%3
1622
16th to endNight
28%12%20%24%13%
1739
August1st to 15thNight
37%10%16%21%14%
1715
16th to endNight
37%9%16%24%10%1
2003
September1st to 15thNight
35%9%14%20%17%2
1956
16th to endNight
42%6%9%23%16%1
2177
October1st to 15thNight
40%5%11%24%15%2
2340
16th to endNight
33%49%26%22%3
2447
November1st to 15thNight
36%5%9%20%21%7%
2308
16th to endNight
37%5%9%23%20%3
2730
December1st to 15thNight
45%6%9%21%14%3
2730
16th to endNight
44%5%12%21%13%2
2884

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
19%28%33%11%5%
135
16th to endDay
25%29%28%15%2
144
February1st to 15thDay
25%33%34%5%
135
16th to endDay
26%17%33%19%2
204
March1st to 15thDay
19%21%30%21%6%
330
16th to endDay
18%18%30%22%7%2
352
April1st to 15thDay
16%20%25%23%11%1
330
16th to endDay
23%10%23%21%14%6%
319
May1st to 15thDay
21%15%22%19%14%6%
348
16th to endDay
19%422%23%17%11%
395
June1st to 15thDay
13%5%24%26%23%7%
375
16th to endDay
11%5%26%28%21%7%
375
July1st to 15thDay
13%219%31%22%10%
365
16th to endDay
11%111%32%28%14%
390
August1st to 15thDay
14%314%26%24%16%
358
16th to endDay
10%211%28%23%23%
396
September1st to 15thDay
16%5%14%21%21%21%
375
16th to endDay
22%420%21%21%10%
374
October1st to 15thDay
18%6%15%28%22%7%
375
16th to endDay
13%15%28%22%15%3
382
November1st to 15thDay
21%7%21%29%16%2
307
16th to endDay
16%15%32%25%6%3
90
December1st to 15thDay
18%17%34%20%6%2
90
16th to endDay
19%28%33%16%1
102
January1st to 15thNight
19%17%29%27%6%
780
16th to endNight
20%14%35%27%2
832
February1st to 15thNight
18%15%34%29%1
764
16th to endNight
18%19%35%22%2
683
March1st to 15thNight
20%15%32%26%5%
780
16th to endNight
19%13%31%26%6%1
832
April1st to 15thNight
16%17%33%25%5%
778
16th to endNight
18%9%25%31%12%
733
May1st to 15thNight
18%5%21%35%17%2
585
16th to endNight
17%116%37%24%2
525
June1st to 15thNight
8%216%40%28%2
390
16th to endNight
6%114%48%27%
390
July1st to 15thNight
11%111%34%36%3
512
16th to endNight
6%8%35%41%7%
612
August1st to 15thNight
10%110%39%33%4
575
16th to endNight
11%110%34%37%4
761
September1st to 15thNight
14%215%29%32%6%
780
16th to endNight
19%316%29%27%4
777
October1st to 15thNight
17%6%18%30%23%3
780
16th to endNight
14%11%29%28%15%1
816
November1st to 15thNight
16%10%22%34%13%2
760
16th to endNight
16%14%28%28%11%1
780
December1st to 15thNight
19%11%29%30%8%
780
16th to endNight
17%13%29%35%3
832
Page generated at 2018-10-28 08:41:05. Version ac04

Copyright 2018 A. Danko


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