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Lexington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lexington clear sky chart from 2005-11-05 to 2019-05-11.

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%
17604
20%
53431
14%
17560
49%
17560
24%
35017

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
19%
840
15%
2717
7%
836
28%
836
13%
2008
January16th to endNight
20%
896
17%
2912
9%
896
30%
896
16%
2049
February1st to 15thNight
20%
824
14%
2507
6%
821
29%
821
17%
1818
February16th to endNight
17%
735
15%
2205
6%
735
25%
735
14%
1635
March1st to 15thNight
24%
840
18%
2436
9%
840
32%
840
18%
1727
March16th to endNight
32%
896
15%
2464
9%
896
37%
896
22%
1733
April1st to 15thNight
36%
679
22%
2147
14%
679
46%
679
26%
1336
April16th to endNight
41%
624
20%
1917
12%
624
48%
624
24%
1266
May1st to 15thNight
41%
617
16%
1852
11%
617
46%
617
20%
1302
May16th to endNight
60%
610
18%
1828
14%
609
63%
609
28%
1171
June1st to 15thNight
68%
585
19%
1755
17%
585
71%
585
39%
988
June16th to endNight
68%
585
19%
1619
15%
585
70%
585
36%
977
July1st to 15thNight
62%
555
17%
1576
14%
555
63%
555
31%
990
July16th to endNight
74%
612
20%
1739
17%
579
76%
579
37%
1008
August1st to 15thNight
77%
575
23%
1715
21%
572
79%
572
37%
1011
August16th to endNight
76%
621
22%
2019
24%
621
76%
621
36%
1110
September1st to 15thNight
63%
725
24%
2090
21%
725
66%
725
31%
1311
September16th to endNight
60%
777
28%
2145
23%
777
63%
777
34%
1315
October1st to 15thNight
57%
780
31%
2177
25%
780
62%
780
37%
1279
October16th to endNight
41%
832
26%
2573
20%
832
50%
832
28%
1586
November1st to 15thNight
43%
820
27%
2666
23%
820
51%
820
27%
1604
November16th to endNight
35%
840
23%
2730
16%
840
44%
840
23%
1752
December1st to 15thNight
28%
840
15%
2730
8%
840
36%
840
17%
1912
December16th to endNight
23%
896
16%
2912
6%
896
34%
896
14%
2129

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
15%7%35%5%3445%7%36%
54401
Night
14%7%35%5%3445%7%39%
53622
Cloud CoverDay
15%7%36%5%35%45%7%37%
54411
Night
14%7%35%5%3445%7%39%
53626
TransparencyDay
45%5%11%21%13%2
54110
Night
43%5%10%22%15%2
53431
SeeingDay
18%7%22%21%18%11%
7587
Night
18%7%24%28%18%2
17605

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
20%9%48%5%34445%27%
1881
16th to endDay
17%11%5%7%6%24445%31%
2016
February1st to 15thDay
19%11%48%5%2444429%
2014
16th to endDay
18%10%47%6%35%45%6%27%
1840
March1st to 15thDay
22%9%36%5%3344433%
2173
16th to endDay
19%8%36%6%34446%32%
2464
April1st to 15thDay
15%7%35%5%3345%6%39%
2472
16th to endDay
16%7%25%5%3445%8%36%
2647
May1st to 15thDay
20%7%345%3445%7%33%
2656
16th to endDay
10%5%26%6%35%5%6%9%36%
2639
June1st to 15thDay
9%425%5%35%6%6%8%41%
2535
16th to endDay
8%435%5%35%6%7%9%39%
2663
July1st to 15thDay
12%6%35%5%35%5%7%8%35%
2616
16th to endDay
9%5%25%6%47%6%7%9%35%
2673
August1st to 15thDay
10%5%15%5%36%6%7%9%38%
2487
16th to endDay
8%5%26%6%45%5%7%9%37%
2532
September1st to 15thDay
14%5%25%5%26%6%5%7%37%
2187
16th to endDay
15%5%25%423445%46%
2145
October1st to 15thDay
11%5%135%3345%6%48%
2111
16th to endDay
18%5%23413335%46%
2002
November1st to 15thDay
15%6%24423335%46%
1852
16th to endDay
16%9%44422336%41%
1890
December1st to 15thDay
22%11%36%435%34430%
1890
16th to endDay
20%12%47%433446%29%
2016
January1st to 15thNight
18%10%5%8%7%35%43428%
2717
16th to endNight
17%10%47%5%3434433%
2912
February1st to 15thNight
21%9%47%5%23446%30%
2505
16th to endNight
19%12%47%5%33345%28%
2205
March1st to 15thNight
18%9%37%5%24445%34%
2424
16th to endNight
16%8%47%6%34347%35%
2464
April1st to 15thNight
14%5%25%5%24447%42%
2147
16th to endNight
13%6%36%435%45%6%39%
1917
May1st to 15thNight
17%6%35%6%346%5%7%33%
1852
16th to endNight
8%426%5%45%5%7%10%39%
1826
June1st to 15thNight
5%3244245%7%11%47%
1755
16th to endNight
6%2235%25%6%6%12%44%
1619
July1st to 15thNight
9%5%25%5%3446%9%44%
1664
16th to endNight
6%314435%5%7%10%47%
1847
August1st to 15thNight
5%313435%6%6%10%49%
1726
16th to endNight
5%4134345%6%10%50%
2019
September1st to 15thNight
12%5%244245%5%9%44%
2090
16th to endNight
11%5%245%24345%50%
2145
October1st to 15thNight
10%42332345%8%50%
2177
16th to endNight
16%5%24434345%46%
2573
November1st to 15thNight
15%6%25%323336%47%
2666
16th to endNight
17%7%35%423345%41%
2730
December1st to 15thNight
20%10%36%424445%32%
2730
16th to endNight
21%12%46%5%24446%28%
2912

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
20%10%48%5%35%445%27%
1881
16th to endDay
17%10%5%7%6%24445%31%
2016
February1st to 15thDay
19%11%49%5%24445%29%
2014
16th to endDay
18%10%48%6%35%35%6%27%
1840
March1st to 15thDay
22%9%36%433345%33%
2184
16th to endDay
19%7%26%6%25%45%6%32%
2463
April1st to 15thDay
15%7%26%5%3445%6%39%
2472
16th to endDay
16%7%25%5%345%5%8%36%
2647
May1st to 15thDay
19%7%25%5%3445%7%34%
2656
16th to endDay
10%6%26%7%35%5%5%9%37%
2639
June1st to 15thDay
8%425%5%36%6%5%8%42%
2535
16th to endDay
7%435%5%36%6%6%9%40%
2663
July1st to 15thDay
12%6%25%436%5%7%9%35%
2616
16th to endDay
9%5%25%6%47%6%7%9%34%
2673
August1st to 15thDay
10%5%15%5%46%5%6%9%38%
2487
16th to endDay
8%5%26%6%46%6%7%9%37%
2532
September1st to 15thDay
13%5%25%5%36%6%5%7%37%
2187
16th to endDay
15%5%25%42335%5%46%
2145
October1st to 15thDay
11%5%135%23446%48%
2111
16th to endDay
18%5%24423325%46%
2002
November1st to 15thDay
15%6%24423335%46%
1852
16th to endDay
16%9%45%423336%41%
1890
December1st to 15thDay
21%11%36%5%35%34430%
1890
16th to endDay
20%13%37%423446%29%
2016
January1st to 15thNight
18%10%5%7%7%3444328%
2717
16th to endNight
17%10%5%7%5%3434433%
2912
February1st to 15thNight
20%9%47%5%23446%30%
2498
16th to endNight
19%12%37%6%24345%28%
2205
March1st to 15thNight
18%9%37%433445%35%
2436
16th to endNight
15%8%37%6%34346%36%
2464
April1st to 15thNight
13%5%25%5%2445%7%42%
2147
16th to endNight
13%6%36%5%35%447%39%
1917
May1st to 15thNight
16%6%35%6%35%6%6%7%33%
1851
16th to endNight
8%425%6%446%7%10%39%
1826
June1st to 15thNight
5%3224345%8%12%47%
1755
16th to endNight
5%2245%25%6%7%12%44%
1619
July1st to 15thNight
8%5%25%5%35%45%9%45%
1664
16th to endNight
6%324435%5%7%11%46%
1847
August1st to 15thNight
5%313435%6%6%10%49%
1726
16th to endNight
5%3135%245%6%10%50%
2019
September1st to 15thNight
12%5%234345%5%8%44%
2090
16th to endNight
11%424434345%50%
2145
October1st to 15thNight
10%41432345%8%50%
2177
16th to endNight
16%5%25%434345%46%
2573
November1st to 15thNight
15%5%34324336%47%
2666
16th to endNight
17%7%35%324345%41%
2730
December1st to 15thNight
21%9%36%423445%32%
2730
16th to endNight
21%12%46%424446%28%
2912

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
58%38%17%10%1
1882
16th to endDay
54%39%22%8%1
2016
February1st to 15thDay
57%46%21%8%1
2016
16th to endDay
56%49%19%8%
1840
March1st to 15thDay
53%310%18%12%1
2184
16th to endDay
51%411%21%10%
2464
April1st to 15thDay
44%411%24%12%2
2472
16th to endDay
45%411%21%13%4
2647
May1st to 15thDay
49%5%13%20%10%1
2656
16th to endDay
42%7%14%22%11%1
2643
June1st to 15thDay
37%7%13%25%14%1
2535
16th to endDay
37%8%12%21%17%2
2663
July1st to 15thDay
42%8%12%17%15%3
2475
16th to endDay
40%7%14%22%11%2
2518
August1st to 15thDay
38%8%13%22%15%1
2474
16th to endDay
40%7%10%23%15%3
2532
September1st to 15thDay
42%6%12%16%15%4
2187
16th to endDay
39%47%23%22%2
2145
October1st to 15thDay
36%49%25%20%3
2111
16th to endDay
40%37%26%18%2
2002
November1st to 15thDay
41%37%23%18%5%
1852
16th to endDay
46%28%24%18%1
1890
December1st to 15thDay
56%310%18%9%1
1890
16th to endDay
56%411%20%6%
2016
January1st to 15thNight
58%47%14%12%2
2717
16th to endNight
53%38%20%11%1
2912
February1st to 15thNight
54%310%21%8%1
2507
16th to endNight
57%49%17%9%1
2205
March1st to 15thNight
51%47%20%14%2
2436
16th to endNight
48%5%11%23%10%1
2464
April1st to 15thNight
40%410%21%19%3
2147
16th to endNight
43%5%10%20%14%5%
1917
May1st to 15thNight
47%8%10%21%9%2
1852
16th to endNight
37%8%14%21%14%3
1828
June1st to 15thNight
27%6%17%28%16%4
1755
16th to endNight
30%7%17%23%16%4
1619
July1st to 15thNight
37%5%13%22%17%4
1576
16th to endNight
28%7%16%27%17%2
1739
August1st to 15thNight
28%8%15%24%19%3
1715
16th to endNight
27%7%14%26%20%3
2019
September1st to 15thNight
36%6%12%20%18%5%
2090
16th to endNight
36%37%23%26%3
2145
October1st to 15thNight
31%410%26%21%5%
2177
16th to endNight
40%36%25%21%3
2573
November1st to 15thNight
39%36%23%21%5%
2666
16th to endNight
44%38%24%17%1
2730
December1st to 15thNight
52%310%19%11%1
2730
16th to endNight
56%49%18%8%1
2912

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
27%14%35%15%6%1
180
16th to endDay
22%20%40%14%2
192
February1st to 15thDay
27%22%33%10%6%
180
16th to endDay
33%10%35%16%3
159
March1st to 15thDay
28%19%35%14%1
264
16th to endDay
22%12%32%21%8%1
416
April1st to 15thDay
19%14%25%25%11%3
390
16th to endDay
21%8%26%24%13%6%
379
May1st to 15thDay
21%7%27%18%17%7%
388
16th to endDay
16%220%25%18%16%
395
June1st to 15thDay
10%214%22%34%15%
375
16th to endDay
10%322%26%22%14%
503
July1st to 15thDay
17%213%23%23%20%
444
16th to endDay
11%18%25%27%25%
390
August1st to 15thDay
13%110%19%29%25%
358
16th to endDay
10%111%28%29%19%
396
September1st to 15thDay
17%29%19%28%22%
375
16th to endDay
20%212%18%29%18%
374
October1st to 15thDay
16%419%24%23%11%
375
16th to endDay
17%8%28%28%14%3
322
November1st to 15thDay
27%7%25%21%13%4
180
16th to endDay
25%8%31%25%8%1
180
December1st to 15thDay
22%17%32%23%31
180
16th to endDay
28%16%40%10%4
192
January1st to 15thNight
25%14%34%19%6%
840
16th to endNight
25%13%35%23%2
896
February1st to 15thNight
26%12%34%24%1
824
16th to endNight
26%13%38%19%2
735
March1st to 15thNight
23%12%33%24%5%
840
16th to endNight
20%9%31%26%11%
896
April1st to 15thNight
17%10%32%29%10%
679
16th to endNight
16%5%31%30%13%1
624
May1st to 15thNight
21%326%28%18%2
617
16th to endNight
11%216%35%28%5%
611
June1st to 15thNight
7%14%42%30%4
585
16th to endNight
7%15%39%31%5%
585
July1st to 15thNight
11%112%32%32%8%
555
16th to endNight
8%6%33%41%8%
612
August1st to 15thNight
8%6%34%43%7%
575
16th to endNight
6%18%34%42%6%
621
September1st to 15thNight
15%110%25%38%7%
725
16th to endNight
14%214%28%34%5%
777
October1st to 15thNight
12%420%30%28%4
780
16th to endNight
19%5%29%29%14%2
832
November1st to 15thNight
18%7%26%27%18%2
820
16th to endNight
22%9%28%28%11%
840
December1st to 15thNight
25%11%27%26%7%
840
16th to endNight
28%11%31%23%4
896
Page generated at 2019-05-12 00:31:09. Version ac04

Copyright 2019 A. Danko


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