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 2018-10-08.

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%
17258
22%
51355
13%
17219
53%
17219
27%
32541

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%
778
23%
2522
10%
776
44%
776
22%
1533
January16th to endNight
26%
832
25%
2704
12%
832
43%
832
24%
1654
February1st to 15thNight
22%
762
21%
2482
8%
761
39%
761
22%
1516
February16th to endNight
24%
683
25%
2031
10%
683
40%
683
25%
1270
March1st to 15thNight
31%
780
24%
2145
11%
780
43%
780
28%
1357
March16th to endNight
33%
832
20%
2288
11%
832
40%
832
26%
1523
April1st to 15thNight
32%
778
20%
2013
7%
778
41%
778
29%
1317
April16th to endNight
39%
724
20%
1880
9%
724
46%
724
30%
1244
May1st to 15thNight
42%
585
18%
1755
9%
585
49%
585
25%
1161
May16th to endNight
55%
609
15%
1828
11%
609
58%
609
27%
1210
June1st to 15thNight
66%
585
16%
1755
15%
585
68%
585
31%
1099
June16th to endNight
71%
585
17%
1755
14%
585
74%
585
33%
1088
July1st to 15thNight
71%
555
14%
1665
13%
555
72%
555
29%
1066
July16th to endNight
72%
612
15%
1739
13%
579
74%
579
29%
1112
August1st to 15thNight
68%
575
20%
1715
15%
572
70%
572
28%
1117
August16th to endNight
71%
754
18%
1996
14%
754
72%
754
31%
1330
September1st to 15thNight
64%
780
23%
2008
17%
780
65%
780
30%
1364
September16th to endNight
50%
777
18%
2151
15%
777
53%
777
22%
1522
October1st to 15thNight
52%
752
25%
2255
23%
752
58%
752
29%
1398
October16th to endNight
43%
768
34%
2304
21%
768
61%
768
35%
1303
November1st to 15thNight
43%
760
26%
2291
17%
760
55%
760
31%
1371
November16th to endNight
40%
780
27%
2613
18%
780
55%
780
29%
1464
December1st to 15thNight
28%
780
20%
2730
10%
780
42%
780
20%
1709
December16th to endNight
24%
832
22%
2730
9%
832
40%
832
18%
1813

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%24435%5%5%8%42%
51765
Night
13%5%2442445%7%45%
51548
Cloud CoverDay
14%4244345%5%7%42%
51775
Night
13%5%2442445%7%45%
51552
TransparencyDay
39%7%12%21%15%3
51476
Night
37%6%11%22%17%4
51355
SeeingDay
17%6%21%22%20%10%
7024
Night
16%7%25%29%18%2
17264

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
16%41432445%7%44%
1746
16th to endDay
14%6%2443445%5%45%
1872
February1st to 15thDay
14%6%24425%45%7%41%
1710
16th to endDay
16%5%25%42445%7%40%
1726
March1st to 15thDay
14%4233235%46%47%
2134
16th to endDay
18%5%24424447%40%
2288
April1st to 15thDay
11%423323447%50%
2264
16th to endDay
16%424435%346%43%
2365
May1st to 15thDay
16%5%25%5%345%5%8%37%
2526
16th to endDay
12%5%25%5%36%5%6%8%37%
2639
June1st to 15thDay
9%324435%6%7%9%42%
2535
16th to endDay
8%325%6%35%6%6%9%41%
2535
July1st to 15thDay
9%425%6%46%7%7%9%35%
2535
16th to endDay
6%5%36%7%47%6%7%11%33%
2673
August1st to 15thDay
12%426%5%45%6%7%10%33%
2487
16th to endDay
10%5%25%5%36%5%7%11%35%
2545
September1st to 15thDay
12%5%25%42445%7%45%
2278
16th to endDay
21%5%2443445%7%35%
2139
October1st to 15thDay
18%412212236%51%
1875
16th to endDay
12%424323335%53%
1920
November1st to 15thDay
14%414334436%51%
1896
16th to endDay
14%31342425%6%50%
1674
December1st to 15thDay
14%5%15%335%5%36%44%
1560
16th to endDay
20%6%25%323446%39%
1843
January1st to 15thNight
15%5%23424435%48%
2522
16th to endNight
15%5%24324445%46%
2704
February1st to 15thNight
15%6%2432335%6%45%
2480
16th to endNight
13%6%34324446%45%
2031
March1st to 15thNight
13%4234235%6%6%45%
2133
16th to endNight
17%5%24423446%44%
2288
April1st to 15thNight
13%5%2343345%6%45%
2013
16th to endNight
16%5%2441345%6%44%
1880
May1st to 15thNight
14%6%25%42435%8%41%
1755
16th to endNight
13%5%25%5%2445%9%41%
1826
June1st to 15thNight
9%414425%5%7%11%43%
1755
16th to endNight
6%3244345%7%11%46%
1755
July1st to 15thNight
7%3235%36%47%10%44%
1755
16th to endNight
5%5%25%5%36%7%6%11%40%
1847
August1st to 15thNight
11%425%5%3446%10%41%
1726
16th to endNight
7%425%5%36%6%7%11%39%
1996
September1st to 15thNight
12%5%25%425%5%5%6%44%
2008
16th to endNight
19%6%35%5%2445%5%37%
2151
October1st to 15thNight
16%413423436%47%
2255
16th to endNight
12%313323335%55%
2304
November1st to 15thNight
14%5%1432343452%
2291
16th to endNight
14%413323446%52%
2613
December1st to 15thNight
16%6%25%5%3334443%
2730
16th to endNight
17%7%35%434447%37%
2730

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%42342435%7%44%
1746
16th to endDay
14%6%2443445%5%46%
1872
February1st to 15thDay
15%6%2443445%7%41%
1710
16th to endDay
16%42443445%8%40%
1726
March1st to 15thDay
14%42432345%6%46%
2145
16th to endDay
19%5%24434446%41%
2287
April1st to 15thDay
11%423323447%50%
2264
16th to endDay
16%5%24425%336%43%
2365
May1st to 15thDay
16%5%25%5%35%5%5%7%38%
2526
16th to endDay
13%4245%36%5%6%8%38%
2639
June1st to 15thDay
9%324425%6%7%9%42%
2535
16th to endDay
8%3246%35%6%7%9%41%
2535
July1st to 15thDay
9%425%7%45%6%8%9%36%
2535
16th to endDay
6%5%26%6%46%7%7%10%34%
2673
August1st to 15thDay
12%425%5%46%6%7%9%34%
2487
16th to endDay
11%5%25%5%45%6%7%10%36%
2545
September1st to 15thDay
13%425%424447%45%
2278
16th to endDay
21%5%244245%5%7%36%
2139
October1st to 15thDay
19%412222245%52%
1875
16th to endDay
13%423423335%54%
1920
November1st to 15thDay
14%413324436%51%
1896
16th to endDay
14%314324347%50%
1674
December1st to 15thDay
14%5%143445%45%44%
1560
16th to endDay
20%6%34333346%40%
1843
January1st to 15thNight
15%424423436%48%
2522
16th to endNight
15%5%24324446%46%
2704
February1st to 15thNight
15%5%25%424346%46%
2473
16th to endNight
13%6%24425%45%6%46%
2031
March1st to 15thNight
13%42442446%6%45%
2145
16th to endNight
17%5%24423346%43%
2288
April1st to 15thNight
14%5%2442346%6%46%
2013
16th to endNight
17%42442345%7%44%
1880
May1st to 15thNight
14%5%25%42445%7%41%
1754
16th to endNight
12%5%25%5%3345%9%41%
1826
June1st to 15thNight
9%314435%46%12%43%
1755
16th to endNight
7%2234345%7%11%46%
1755
July1st to 15thNight
8%324426%5%7%10%44%
1755
16th to endNight
5%5%25%5%36%6%7%11%40%
1847
August1st to 15thNight
12%3245%3446%10%41%
1726
16th to endNight
8%424446%7%6%10%40%
1996
September1st to 15thNight
12%5%25%435%45%6%44%
2008
16th to endNight
20%6%26%43435%5%37%
2151
October1st to 15thNight
17%414423435%48%
2255
16th to endNight
12%323323335%56%
2304
November1st to 15thNight
14%5%2342333452%
2291
16th to endNight
14%313323346%52%
2613
December1st to 15thNight
16%5%3443344443%
2730
16th to endNight
17%7%25%5%24447%37%
2730

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%20%18%4
1747
16th to endDay
38%5%8%24%17%4
1872
February1st to 15thDay
40%6%10%21%18%2
1712
16th to endDay
41%5%13%20%16%2
1726
March1st to 15thDay
36%5%10%22%18%5%
2145
16th to endDay
44%6%9%20%15%3
2288
April1st to 15thDay
33%6%11%26%15%7%
2264
16th to endDay
41%5%10%18%16%7%
2365
May1st to 15thDay
43%9%13%19%10%3
2526
16th to endDay
42%9%14%22%10%1
2643
June1st to 15thDay
35%10%17%23%12%1
2535
16th to endDay
36%11%14%18%15%2
2535
July1st to 15thDay
41%10%15%16%13%2
2396
16th to endDay
40%10%16%18%12%
2518
August1st to 15thDay
43%10%14%20%9%1
2474
16th to endDay
41%10%15%20%11%1
2545
September1st to 15thDay
38%7%12%19%19%2
2278
16th to endDay
47%7%8%17%17%1
2139
October1st to 15thDay
35%410%27%18%4
1875
16th to endDay
34%38%26%21%5%
1920
November1st to 15thDay
34%5%9%18%24%7%
1896
16th to endDay
33%5%9%23%23%4
1674
December1st to 15thDay
39%7%8%22%16%4
1560
16th to endDay
45%6%9%21%15%2
1843
January1st to 15thNight
38%5%9%18%20%7%
2522
16th to endNight
38%5%9%23%18%4
2704
February1st to 15thNight
39%48%24%18%4
2482
16th to endNight
37%5%10%25%16%3
2031
March1st to 15thNight
36%5%9%25%17%4
2145
16th to endNight
41%5%11%20%17%3
2288
April1st to 15thNight
37%6%9%23%17%5%
2013
16th to endNight
39%5%11%18%18%6%
1880
May1st to 15thNight
41%7%12%21%14%2
1755
16th to endNight
39%8%15%24%10%1
1828
June1st to 15thNight
32%10%18%23%13%1
1755
16th to endNight
29%11%16%20%18%3
1755
July1st to 15thNight
33%11%15%20%13%5%
1665
16th to endNight
33%11%18%23%11%1
1739
August1st to 15thNight
36%9%15%21%14%1
1715
16th to endNight
35%10%15%24%11%2
1996
September1st to 15thNight
38%8%11%19%17%4
2008
16th to endNight
47%6%8%17%18%1
2151
October1st to 15thNight
38%5%8%25%19%3
2255
16th to endNight
31%36%27%25%6%
2304
November1st to 15thNight
35%47%19%23%9%
2291
16th to endNight
33%48%24%24%5%
2613
December1st to 15thNight
42%5%8%22%16%3
2730
16th to endNight
45%6%10%18%15%3
2730

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
18%20%39%16%31
135
16th to endDay
21%25%31%18%3
144
February1st to 15thDay
25%23%38%10%2
135
16th to endDay
22%12%39%20%5%
190
March1st to 15thDay
22%13%32%22%9%
330
16th to endDay
22%10%32%25%7%1
352
April1st to 15thDay
16%14%30%23%12%2
330
16th to endDay
21%5%25%23%16%6%
319
May1st to 15thDay
17%8%27%23%14%7%
348
16th to endDay
20%217%22%26%11%
395
June1st to 15thDay
9%317%25%27%16%
375
16th to endDay
11%216%28%27%13%
375
July1st to 15thDay
13%10%24%32%17%
365
16th to endDay
9%110%23%34%20%
390
August1st to 15thDay
13%14%20%30%19%
358
16th to endDay
12%8%21%28%29%
396
September1st to 15thDay
18%312%16%24%25%
375
16th to endDay
28%112%21%21%14%
374
October1st to 15thDay
23%213%22%26%10%
345
16th to endDay
13%7%25%27%21%5%
336
November1st to 15thDay
20%7%26%23%20%2
314
16th to endDay
10%17%22%27%18%4
116
December1st to 15thDay
21%8%36%20%12%1
90
16th to endDay
31%12%37%14%4
137
January1st to 15thNight
19%16%32%26%4
780
16th to endNight
18%12%39%26%3
832
February1st to 15thNight
19%13%40%24%1
764
16th to endNight
16%13%42%25%2
683
March1st to 15thNight
17%11%35%30%5%
780
16th to endNight
20%8%33%29%7%
832
April1st to 15thNight
16%12%35%26%8%
778
16th to endNight
19%6%28%31%14%
724
May1st to 15thNight
18%5%28%30%16%
585
16th to endNight
15%117%29%31%4
611
June1st to 15thNight
9%114%34%35%4
585
16th to endNight
7%110%39%36%3
585
July1st to 15thNight
9%9%34%38%8%
555
16th to endNight
7%8%35%40%7%
612
August1st to 15thNight
13%7%35%38%4
575
16th to endNight
9%8%28%44%7%
754
September1st to 15thNight
15%110%29%35%8%
780
16th to endNight
24%213%24%31%3
777
October1st to 15thNight
19%417%27%24%5%
752
16th to endNight
14%7%29%30%15%1
768
November1st to 15thNight
16%5%28%32%14%2
760
16th to endNight
16%10%29%28%14%
780
December1st to 15thNight
20%10%33%26%8%
780
16th to endNight
21%12%36%26%3
832
Page generated at 2018-10-09 10:39:12. Version ac04

Copyright 2018 A. Danko


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