Smith Mountain Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smith Mountain Lake State Park clear sky chart from 2005-11-05 to 2017-09-17.

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%
15849
21%
47163
13%
15810
53%
15810
27%
29875

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%
718
23%
2327
10%
716
44%
716
21%
1431
January16th to endNight
24%
768
24%
2496
10%
768
42%
768
23%
1538
February1st to 15thNight
22%
702
22%
2287
7%
701
40%
701
23%
1376
February16th to endNight
22%
631
26%
1876
9%
631
40%
631
26%
1162
March1st to 15thNight
33%
720
24%
1980
12%
720
44%
720
28%
1257
March16th to endNight
33%
768
20%
2112
11%
768
41%
768
26%
1403
April1st to 15thNight
33%
718
20%
1858
7%
718
42%
718
29%
1205
April16th to endNight
40%
677
20%
1757
9%
677
46%
677
30%
1166
May1st to 15thNight
40%
540
16%
1620
7%
540
47%
540
23%
1089
May16th to endNight
58%
561
16%
1684
12%
561
61%
561
29%
1084
June1st to 15thNight
64%
540
16%
1620
15%
540
66%
540
31%
1009
June16th to endNight
72%
540
17%
1620
14%
540
74%
540
33%
1009
July1st to 15thNight
70%
510
12%
1530
11%
510
71%
510
27%
1010
July16th to endNight
74%
564
16%
1595
13%
531
76%
531
30%
1003
August1st to 15thNight
68%
539
19%
1609
15%
536
70%
536
28%
1043
August16th to endNight
70%
696
19%
1842
14%
696
71%
696
30%
1240
September1st to 15thNight
64%
720
23%
1854
17%
720
66%
720
31%
1248
September16th to endNight
48%
665
17%
1842
13%
665
51%
665
21%
1318
October1st to 15thNight
49%
660
26%
1980
24%
660
57%
660
28%
1230
October16th to endNight
43%
704
32%
2112
20%
704
59%
704
34%
1196
November1st to 15thNight
44%
700
27%
2110
18%
700
56%
700
32%
1236
November16th to endNight
38%
720
25%
2412
16%
720
52%
720
27%
1378
December1st to 15thNight
28%
720
21%
2520
10%
720
42%
720
20%
1578
December16th to endNight
24%
768
22%
2520
9%
768
40%
768
18%
1666

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%424435%5%5%8%42%
47597
Night
13%5%2442445%7%45%
47356
Cloud CoverDay
13%424435%5%5%7%42%
47607
Night
13%42442445%7%45%
47360
TransparencyDay
39%7%12%21%15%3
47308
Night
37%6%11%22%17%4
47163
SeeingDay
17%6%21%22%21%10%
5629
Night
16%7%25%29%18%2
15855

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
15%41442445%7%43%
1611
16th to endDay
14%6%2443445%5%44%
1728
February1st to 15thDay
13%6%24425%5%5%7%41%
1575
16th to endDay
15%415%43445%8%42%
1595
March1st to 15thDay
14%4234345%46%47%
1969
16th to endDay
18%5%24424447%40%
2112
April1st to 15thDay
11%423323447%51%
2089
16th to endDay
16%424435%346%43%
2213
May1st to 15thDay
17%5%25%5%35%5%6%8%35%
2331
16th to endDay
11%415%5%36%5%6%8%39%
2431
June1st to 15thDay
10%324435%6%7%9%42%
2340
16th to endDay
8%325%6%36%6%7%9%41%
2340
July1st to 15thDay
9%425%6%46%7%7%9%33%
2340
16th to endDay
5%436%7%47%7%7%11%34%
2465
August1st to 15thDay
12%426%5%46%6%8%10%32%
2340
16th to endDay
10%5%26%5%36%5%7%10%34%
2348
September1st to 15thDay
11%5%25%42445%7%46%
2103
16th to endDay
22%6%25%5%3445%6%35%
1824
October1st to 15thDay
18%412212236%53%
1650
16th to endDay
13%5%24423335%52%
1760
November1st to 15thDay
12%414324436%53%
1747
16th to endDay
15%31442425%6%48%
1545
December1st to 15thDay
14%415%335%5%37%45%
1440
16th to endDay
21%6%24323346%39%
1701
January1st to 15thNight
15%5%23424336%48%
2327
16th to endNight
15%5%24335%446%45%
2496
February1st to 15thNight
15%5%2432335%6%46%
2285
16th to endNight
12%5%34325%445%47%
1876
March1st to 15thNight
13%4234235%6%6%45%
1968
16th to endNight
17%5%34433446%44%
2112
April1st to 15thNight
13%5%2343345%6%46%
1858
16th to endNight
15%5%2441445%6%44%
1757
May1st to 15thNight
15%6%25%5%3435%8%40%
1620
16th to endNight
11%425%5%2445%9%43%
1682
June1st to 15thNight
9%414435%47%11%43%
1620
16th to endNight
6%3245%345%7%11%46%
1620
July1st to 15thNight
8%4245%37%5%7%10%41%
1620
16th to endNight
35%25%5%36%7%6%11%41%
1703
August1st to 15thNight
10%425%5%3446%10%40%
1620
16th to endNight
8%425%6%36%6%7%11%38%
1842
September1st to 15thNight
11%5%25%425%5%5%6%45%
1854
16th to endNight
19%6%36%5%25%45%5%36%
1842
October1st to 15thNight
16%4245%23435%48%
1980
16th to endNight
12%313223335%55%
2112
November1st to 15thNight
13%41432343454%
2110
16th to endNight
15%413323446%50%
2412
December1st to 15thNight
16%6%25%5%3344443%
2520
16th to endNight
18%7%35%434447%37%
2520

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
16%42342445%7%43%
1611
16th to endDay
14%6%2443445%5%45%
1728
February1st to 15thDay
13%6%25%335%45%7%42%
1575
16th to endDay
15%42443446%8%41%
1595
March1st to 15thDay
14%4234245%5%6%46%
1980
16th to endDay
19%424434446%41%
2111
April1st to 15thDay
11%423423447%51%
2089
16th to endDay
16%5%24435%447%43%
2213
May1st to 15thDay
17%5%25%5%35%5%5%7%36%
2331
16th to endDay
11%4245%46%5%7%8%40%
2431
June1st to 15thDay
10%324425%6%7%9%42%
2340
16th to endDay
8%3246%35%6%7%9%41%
2340
July1st to 15thDay
9%425%7%46%6%8%10%33%
2340
16th to endDay
5%426%7%47%7%7%10%35%
2465
August1st to 15thDay
12%425%5%46%6%7%9%33%
2340
16th to endDay
11%5%26%5%45%6%7%9%35%
2348
September1st to 15thDay
11%425%424447%47%
2103
16th to endDay
22%5%2443445%6%35%
1824
October1st to 15thDay
19%412222245%53%
1650
16th to endDay
13%423423335%52%
1760
November1st to 15thDay
12%413324436%53%
1747
16th to endDay
15%414424347%48%
1545
December1st to 15thDay
14%5%143445%46%45%
1440
16th to endDay
21%5%3433335%5%40%
1701
January1st to 15thNight
15%424423436%48%
2327
16th to endNight
15%5%24324446%45%
2496
February1st to 15thNight
15%5%24314346%47%
2278
16th to endNight
12%6%24325%45%5%47%
1876
March1st to 15thNight
13%42442446%6%45%
1980
16th to endNight
17%5%24423346%44%
2112
April1st to 15thNight
14%42442346%6%46%
1858
16th to endNight
16%42442345%7%43%
1757
May1st to 15thNight
15%5%25%42445%7%40%
1619
16th to endNight
10%5%25%5%3445%9%43%
1682
June1st to 15thNight
9%414435%46%12%43%
1620
16th to endNight
6%223435%5%7%11%46%
1620
July1st to 15thNight
8%3245%26%6%7%10%42%
1620
16th to endNight
4425%5%36%6%7%11%41%
1703
August1st to 15thNight
11%4245%3446%10%41%
1620
16th to endNight
8%425%446%7%7%10%39%
1842
September1st to 15thNight
11%5%25%435%45%6%46%
1854
16th to endNight
20%6%26%43435%5%36%
1842
October1st to 15thNight
17%4145%2333448%
1980
16th to endNight
12%323323335%56%
2112
November1st to 15thNight
12%42342333454%
2110
16th to endNight
15%313323346%50%
2412
December1st to 15thNight
17%5%3443344443%
2520
16th to endNight
18%7%25%5%23447%37%
2520

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
38%6%11%21%18%2
1612
16th to endDay
39%5%8%25%16%4
1728
February1st to 15thDay
39%5%9%22%19%2
1577
16th to endDay
38%5%14%21%16%2
1595
March1st to 15thDay
36%6%11%22%17%4
1980
16th to endDay
44%6%9%21%14%4
2112
April1st to 15thDay
32%6%11%25%16%7%
2089
16th to endDay
41%5%11%19%15%6%
2213
May1st to 15thDay
45%9%13%17%10%2
2331
16th to endDay
39%9%14%23%11%1
2435
June1st to 15thDay
35%9%17%23%12%1
2340
16th to endDay
37%11%15%18%15%2
2340
July1st to 15thDay
43%11%15%14%12%2
2201
16th to endDay
39%10%17%18%13%
2310
August1st to 15thDay
44%10%13%20%10%1
2327
16th to endDay
42%10%14%20%10%1
2348
September1st to 15thDay
37%7%12%19%20%2
2103
16th to endDay
48%7%9%15%18%1
1824
October1st to 15thDay
34%310%27%19%4
1650
16th to endDay
35%39%25%20%5%
1760
November1st to 15thDay
33%5%9%18%26%7%
1747
16th to endDay
35%5%9%23%21%3
1545
December1st to 15thDay
39%7%8%22%17%5%
1440
16th to endDay
45%6%8%20%16%2
1701
January1st to 15thNight
39%5%9%19%19%7%
2327
16th to endNight
39%5%9%23%17%3
2496
February1st to 15thNight
38%48%24%19%4
2287
16th to endNight
37%5%10%25%17%3
1876
March1st to 15thNight
36%6%9%26%16%3
1980
16th to endNight
41%5%10%21%17%2
2112
April1st to 15thNight
36%6%10%22%18%5%
1858
16th to endNight
39%5%11%19%16%7%
1757
May1st to 15thNight
43%7%13%20%14%1
1620
16th to endNight
36%8%16%25%10%2
1684
June1st to 15thNight
32%10%18%24%13%1
1620
16th to endNight
29%12%16%19%18%3
1620
July1st to 15thNight
35%12%15%19%12%5%
1530
16th to endNight
32%11%18%24%12%1
1595
August1st to 15thNight
36%9%15%20%15%1
1609
16th to endNight
36%10%14%23%11%2
1842
September1st to 15thNight
37%8%10%19%18%5%
1854
16th to endNight
48%6%8%15%18%1
1842
October1st to 15thNight
39%48%24%19%3
1980
16th to endNight
31%36%27%24%5%
2112
November1st to 15thNight
33%48%18%25%9%
2110
16th to endNight
34%48%24%23%5%
2412
December1st to 15thNight
42%5%8%22%17%3
2520
16th to endNight
45%5%10%18%16%3
2520

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
17%20%43%12%42
90
16th to endDay
21%31%30%15%1
96
February1st to 15thDay
20%27%41%8%2
90
16th to endDay
16%15%41%21%5%
146
March1st to 15thDay
20%12%31%24%11%
270
16th to endDay
21%9%31%26%9%1
288
April1st to 15thDay
14%14%26%25%15%3
270
16th to endDay
21%424%22%18%8%
270
May1st to 15thDay
19%10%29%22%11%6%
288
16th to endDay
16%119%23%25%13%
331
June1st to 15thDay
11%317%23%25%17%
315
16th to endDay
11%317%28%28%11%
315
July1st to 15thDay
15%12%25%33%12%
305
16th to endDay
6%19%23%35%24%
326
August1st to 15thDay
14%14%20%30%18%
313
16th to endDay
12%6%21%29%28%
332
September1st to 15thDay
15%213%19%26%21%
315
16th to endDay
32%15%16%19%15%
259
October1st to 15thDay
25%315%23%24%6%
255
16th to endDay
14%6%23%30%21%2
272
November1st to 15thDay
16%8%27%23%21%3
255
16th to endDay
14%16%20%24%20%2
77
December1st to 15thDay
20%10%35%20%13%1
60
16th to endDay
36%12%30%16%4
91
January1st to 15thNight
19%17%32%26%4
720
16th to endNight
18%12%41%25%2
768
February1st to 15thNight
19%13%41%25%
704
16th to endNight
15%13%43%24%2
631
March1st to 15thNight
16%11%34%31%5%
720
16th to endNight
19%8%33%29%7%1
768
April1st to 15thNight
15%12%35%26%9%
718
16th to endNight
18%6%28%31%15%
677
May1st to 15thNight
19%5%29%30%14%
540
16th to endNight
13%118%29%32%4
563
June1st to 15thNight
10%115%34%34%5%
540
16th to endNight
7%110%40%36%3
540
July1st to 15thNight
10%10%36%37%5%
510
16th to endNight
6%18%35%41%7%
564
August1st to 15thNight
12%7%35%38%4
539
16th to endNight
10%8%29%44%7%
696
September1st to 15thNight
13%110%31%36%6%
720
16th to endNight
24%215%25%29%2
665
October1st to 15thNight
19%5%20%29%22%3
660
16th to endNight
14%6%29%32%15%1
704
November1st to 15thNight
14%6%29%33%14%2
700
16th to endNight
17%10%28%28%13%
720
December1st to 15thNight
21%10%34%26%8%
720
16th to endNight
22%11%35%26%3
768
Page generated at 2017-09-18 08:38:27. Version ac04

Copyright 2017 A. Danko


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