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 2017-09-18.

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
43%
15385
20%
46953
13%
15349
52%
15349
25%
29911

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
27%
716
22%
2327
10%
716
43%
716
19%
1465
January16th to endNight
22%
768
21%
2496
9%
768
38%
768
20%
1582
February1st to 15thNight
27%
701
20%
2287
8%
701
42%
701
22%
1409
February16th to endNight
21%
631
23%
1913
9%
631
36%
631
20%
1229
March1st to 15thNight
29%
720
22%
1980
10%
720
40%
720
24%
1290
March16th to endNight
30%
768
18%
2112
9%
768
38%
768
23%
1418
April1st to 15thNight
30%
718
18%
1826
6%
718
38%
718
26%
1223
April16th to endNight
42%
685
20%
1765
9%
685
48%
685
30%
1175
May1st to 15thNight
46%
540
15%
1620
10%
540
50%
540
21%
1127
May16th to endNight
57%
482
16%
1605
13%
482
60%
482
25%
1014
June1st to 15thNight
65%
360
17%
1440
21%
360
69%
360
25%
828
June16th to endNight
70%
360
18%
1440
19%
360
75%
360
25%
831
July1st to 15thNight
63%
470
11%
1490
11%
470
65%
470
25%
963
July16th to endNight
79%
564
15%
1595
13%
531
81%
531
35%
963
August1st to 15thNight
70%
539
17%
1609
14%
536
70%
536
28%
1060
August16th to endNight
64%
702
18%
1848
13%
702
65%
702
29%
1253
September1st to 15thNight
62%
720
25%
1806
16%
720
65%
720
34%
1183
September16th to endNight
52%
669
20%
1875
17%
669
54%
669
25%
1265
October1st to 15thNight
50%
660
23%
1980
22%
660
56%
660
27%
1249
October16th to endNight
40%
704
28%
2112
17%
704
55%
704
31%
1241
November1st to 15thNight
45%
700
27%
2125
18%
700
56%
700
29%
1268
November16th to endNight
36%
720
20%
2520
14%
720
47%
720
22%
1518
December1st to 15thNight
33%
720
18%
2520
10%
720
44%
720
17%
1640
December16th to endNight
32%
768
21%
2662
11%
768
46%
768
18%
1717

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
12%5%25%5%35%5%5%7%40%
47814
Night
12%5%2443445%7%44%
47146
Cloud CoverDay
12%5%25%5%35%5%5%7%40%
47824
Night
12%5%2442445%7%44%
47150
TransparencyDay
41%8%12%20%14%2
47525
Night
38%7%12%22%16%2
46953
SeeingDay
16%10%22%24%17%8%
5600
Night
16%9%24%31%16%1
15394

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%
1611
16th to endDay
13%7%35%434445%43%
1728
February1st to 15thDay
11%7%46%5%345%5%6%39%
1575
16th to endDay
12%5%36%425%5%5%6%42%
1557
March1st to 15thDay
13%6%35%425%43444%
1969
16th to endDay
13%8%25%5%345%5%6%38%
2112
April1st to 15thDay
11%425%5%3445%6%47%
2120
16th to endDay
16%5%15%433347%44%
2205
May1st to 15thDay
17%6%25%5%35%5%5%7%34%
2331
16th to endDay
13%5%25%6%36%5%6%8%35%
2509
June1st to 15thDay
10%4245%45%6%6%10%39%
2520
16th to endDay
7%425%6%35%6%7%11%38%
2520
July1st to 15thDay
10%426%6%36%6%8%9%32%
2376
16th to endDay
7%425%6%47%7%8%10%34%
2465
August1st to 15thDay
10%5%26%7%45%6%7%8%33%
2340
16th to endDay
10%425%6%36%7%7%8%35%
2339
September1st to 15thDay
12%5%244345%5%6%44%
2152
16th to endDay
16%6%26%5%35%45%5%37%
1809
October1st to 15thDay
17%5%25%322345%45%
1650
16th to endDay
13%5%1342345%7%48%
1760
November1st to 15thDay
11%6%23224346%53%
1727
16th to endDay
15%5%24434346%45%
1440
December1st to 15thDay
15%5%23425%35%7%43%
1440
16th to endDay
17%7%25%424346%40%
1559
January1st to 15thNight
14%6%2443445%6%44%
2327
16th to endNight
14%8%25%424345%43%
2496
February1st to 15thNight
12%7%243245%5%6%46%
2285
16th to endNight
10%5%26%5%345%6%6%43%
1913
March1st to 15thNight
14%424434347%46%
1968
16th to endNight
15%6%25%423446%43%
2112
April1st to 15thNight
12%5%25%33446%5%45%
1826
16th to endNight
13%42442445%8%45%
1765
May1st to 15thNight
15%7%15%435%45%6%39%
1620
16th to endNight
11%42342446%8%43%
1603
June1st to 15thNight
7%415%425%6%6%10%45%
1440
16th to endNight
6%325%425%7%7%8%46%
1440
July1st to 15thNight
9%435%4345%7%10%41%
1580
16th to endNight
4213436%5%8%12%45%
1703
August1st to 15thNight
8%5%26%6%346%6%9%41%
1620
16th to endNight
9%5%25%6%35%6%6%9%38%
1848
September1st to 15thNight
11%41442445%7%47%
1806
16th to endNight
16%6%24434445%43%
1875
October1st to 15thNight
15%414334346%45%
1980
16th to endNight
12%41442335%5%52%
2112
November1st to 15thNight
12%6%23323445%52%
2125
16th to endNight
15%5%2442435%5%47%
2520
December1st to 15thNight
14%6%35%5%35%5%3442%
2520
16th to endNight
14%6%245%35%446%41%
2662

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%35%5%345%6%7%39%
1611
16th to endDay
14%7%34434445%43%
1728
February1st to 15thDay
11%8%45%5%35%45%6%39%
1575
16th to endDay
12%6%26%4245%6%6%41%
1557
March1st to 15thDay
14%6%25%426%345%44%
1980
16th to endDay
14%8%36%4345%5%6%38%
2111
April1st to 15thDay
11%5%245%34446%47%
2120
16th to endDay
16%5%14424347%43%
2205
May1st to 15thDay
17%6%25%6%25%45%7%34%
2331
16th to endDay
12%5%26%6%36%5%6%8%36%
2509
June1st to 15thDay
10%415%5%36%6%6%9%40%
2520
16th to endDay
8%325%5%36%5%7%11%39%
2520
July1st to 15thDay
11%436%6%36%6%7%10%33%
2376
16th to endDay
7%425%6%48%7%7%10%35%
2465
August1st to 15thDay
10%5%26%7%45%6%7%9%33%
2340
16th to endDay
10%5%25%5%46%7%7%9%35%
2339
September1st to 15thDay
12%5%14435%45%6%45%
2152
16th to endDay
17%6%26%5%35%45%6%37%
1809
October1st to 15thDay
17%5%25%322345%46%
1650
16th to endDay
14%5%13423447%48%
1760
November1st to 15thDay
11%6%23224246%53%
1727
16th to endDay
15%424424446%45%
1440
December1st to 15thDay
16%5%24325%36%6%44%
1440
16th to endDay
17%7%25%5%33346%40%
1559
January1st to 15thNight
14%5%2443445%7%43%
2327
16th to endNight
14%8%34424346%43%
2496
February1st to 15thNight
12%7%25%32445%6%45%
2278
16th to endNight
10%6%26%5%245%6%6%42%
1913
March1st to 15thNight
14%5%25%433447%45%
1980
16th to endNight
15%5%34424346%44%
2112
April1st to 15thNight
13%5%2443446%5%44%
1826
16th to endNight
14%42442445%7%45%
1765
May1st to 15thNight
16%5%25%436%447%39%
1619
16th to endNight
12%4235%245%6%9%43%
1603
June1st to 15thNight
7%4245%25%6%7%9%45%
1440
16th to endNight
6%425%425%7%6%8%46%
1440
July1st to 15thNight
8%5%25%425%5%7%10%41%
1580
16th to endNight
4313436%5%8%12%46%
1703
August1st to 15thNight
8%5%25%6%25%5%7%7%42%
1620
16th to endNight
9%5%25%5%45%5%7%10%38%
1848
September1st to 15thNight
11%41442445%8%47%
1806
16th to endNight
15%6%2443445%5%42%
1875
October1st to 15thNight
15%5%14424445%46%
1980
16th to endNight
12%42342335%5%52%
2112
November1st to 15thNight
12%5%24323445%51%
2125
16th to endNight
14%6%24424446%46%
2520
December1st to 15thNight
15%7%25%5%25%5%3441%
2520
16th to endNight
14%7%25%5%345%46%40%
2662

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%8%11%18%15%3
1612
16th to endDay
43%410%21%16%3
1728
February1st to 15thDay
43%5%11%20%15%3
1577
16th to endDay
41%6%12%22%14%2
1557
March1st to 15thDay
43%5%9%22%15%3
1980
16th to endDay
46%7%10%19%13%3
2112
April1st to 15thDay
38%6%10%21%17%5%
2120
16th to endDay
41%6%10%18%16%5%
2205
May1st to 15thDay
48%8%12%17%11%1
2331
16th to endDay
43%9%14%20%9%1
2513
June1st to 15thDay
38%10%15%22%11%1
2520
16th to endDay
37%11%17%19%12%1
2520
July1st to 15thDay
43%10%13%16%12%2
2237
16th to endDay
40%11%15%19%11%1
2310
August1st to 15thDay
44%11%13%19%11%
2327
16th to endDay
42%11%14%20%9%1
2339
September1st to 15thDay
39%7%12%18%18%3
2152
16th to endDay
46%7%8%19%16%
1809
October1st to 15thDay
40%5%10%25%14%4
1650
16th to endDay
35%5%9%26%18%4
1760
November1st to 15thDay
33%39%22%22%6%
1727
16th to endDay
39%49%23%19%2
1440
December1st to 15thDay
40%6%12%22%14%4
1440
16th to endDay
45%5%11%22%13%1
1559
January1st to 15thNight
40%5%11%18%18%5%
2327
16th to endNight
42%411%22%16%2
2496
February1st to 15thNight
38%5%11%24%16%3
2287
16th to endNight
39%6%12%22%16%2
1913
March1st to 15thNight
39%5%12%26%13%3
1980
16th to endNight
41%6%13%20%15%1
2112
April1st to 15thNight
38%6%11%22%16%4
1826
16th to endNight
36%8%13%18%18%4
1765
May1st to 15thNight
45%8%12%19%12%1
1620
16th to endNight
36%9%17%24%9%1
1605
June1st to 15thNight
32%10%17%25%12%1
1440
16th to endNight
31%11%16%21%17%2
1440
July1st to 15thNight
36%11%18%18%12%3
1490
16th to endNight
26%12%21%25%13%
1595
August1st to 15thNight
36%10%15%21%15%
1609
16th to endNight
39%8%15%25%9%1
1848
September1st to 15thNight
33%9%14%20%18%3
1806
16th to endNight
42%6%9%21%17%1
1875
October1st to 15thNight
39%410%26%16%2
1980
16th to endNight
33%410%25%22%3
2112
November1st to 15thNight
35%48%20%22%8%
2125
16th to endNight
38%5%10%22%19%3
2520
December1st to 15thNight
44%6%9%21%15%3
2520
16th to endNight
44%5%12%21%13%2
2662

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
24%25%33%10%5%1
90
16th to endDay
25%32%28%12%2
96
February1st to 15thDay
22%36%36%31
90
16th to endDay
22%20%33%22%2
159
March1st to 15thDay
16%19%31%24%7%
270
16th to endDay
18%16%31%22%8%3
288
April1st to 15thDay
13%18%25%26%14%1
270
16th to endDay
22%7%23%22%15%7%
270
May1st to 15thDay
23%16%22%17%12%7%
288
16th to endDay
18%5%23%23%17%12%
331
June1st to 15thDay
12%6%25%25%23%8%
315
16th to endDay
10%5%27%27%21%7%
315
July1st to 15thDay
15%221%32%20%6%
305
16th to endDay
8%110%33%30%16%
326
August1st to 15thDay
13%315%26%24%15%
313
16th to endDay
11%210%28%23%24%
332
September1st to 15thDay
13%6%15%23%21%20%
315
16th to endDay
22%420%18%22%12%
262
October1st to 15thDay
20%5%14%30%21%7%
255
16th to endDay
13%13%28%22%17%4
272
November1st to 15thDay
18%8%20%30%19%3
250
16th to endDay
23%11%31%23%6%3
60
December1st to 15thDay
18%18%33%20%6%3
60
16th to endDay
22%27%29%19%1
68
January1st to 15thNight
20%18%29%26%5%
720
16th to endNight
20%14%35%26%1
768
February1st to 15thNight
18%15%34%29%1
704
16th to endNight
17%20%36%22%2
631
March1st to 15thNight
20%14%32%26%5%
720
16th to endNight
19%13%31%25%7%1
768
April1st to 15thNight
15%18%32%26%6%
718
16th to endNight
18%9%25%32%13%1
685
May1st to 15thNight
18%5%22%34%16%1
540
16th to endNight
15%117%37%24%2
484
June1st to 15thNight
8%316%41%27%2
360
16th to endNight
6%114%50%25%
360
July1st to 15thNight
12%211%36%34%2
470
16th to endNight
5%7%34%42%8%
564
August1st to 15thNight
10%110%38%33%4
539
16th to endNight
12%110%35%36%3
702
September1st to 15thNight
12%215%30%32%5%
720
16th to endNight
18%316%30%26%3
669
October1st to 15thNight
18%6%19%31%21%3
660
16th to endNight
14%10%29%28%15%
704
November1st to 15thNight
15%11%22%34%13%2
700
16th to endNight
17%14%28%26%11%1
720
December1st to 15thNight
19%12%29%30%8%
720
16th to endNight
18%13%27%35%4
768
Page generated at 2017-09-19 07:32:20. Version ac04

Copyright 2017 A. Danko


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