Fort Leaton State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Leaton State Historic Site clear sky chart from 2005-11-05 to 2017-09-22.

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
68%
15296
32%
47277
26%
15255
74%
15255
46%
23978

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
67%
716
36%
2148
27%
716
75%
716
48%
1094
January16th to endNight
66%
768
36%
2304
30%
768
73%
768
47%
1166
February1st to 15thNight
65%
703
36%
2106
25%
698
75%
698
55%
977
February16th to endNight
60%
632
34%
1894
23%
632
69%
632
52%
912
March1st to 15thNight
57%
720
35%
2106
22%
720
67%
720
50%
1070
March16th to endNight
60%
666
38%
2010
26%
666
70%
666
54%
940
April1st to 15thNight
51%
539
37%
1798
23%
539
67%
539
49%
814
April16th to endNight
53%
540
38%
1800
30%
540
68%
540
53%
779
May1st to 15thNight
49%
539
29%
1799
22%
539
63%
539
45%
844
May16th to endNight
59%
561
27%
1871
26%
561
69%
561
42%
934
June1st to 15thNight
70%
540
25%
1662
23%
540
75%
540
47%
835
June16th to endNight
74%
540
23%
1784
25%
540
77%
540
41%
900
July1st to 15thNight
74%
510
19%
1700
21%
510
76%
510
37%
919
July16th to endNight
78%
564
21%
1771
26%
531
79%
531
31%
1031
August1st to 15thNight
81%
539
24%
1789
30%
536
82%
536
33%
1004
August16th to endNight
77%
573
21%
1910
25%
573
78%
573
28%
1161
September1st to 15thNight
75%
540
21%
1800
22%
540
76%
540
30%
1080
September16th to endNight
71%
513
25%
1888
29%
513
72%
513
26%
1084
October1st to 15thNight
73%
526
33%
1846
31%
526
77%
526
42%
897
October16th to endNight
75%
704
39%
2112
28%
704
81%
704
60%
954
November1st to 15thNight
78%
718
39%
2118
28%
718
82%
718
64%
940
November16th to endNight
73%
900
38%
2340
23%
900
78%
900
59%
1190
December1st to 15thNight
73%
900
38%
2340
27%
900
76%
900
55%
1240
December16th to endNight
66%
845
38%
2381
27%
845
74%
845
51%
1213

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
321232345%7%62%
47542
Night
321332445%8%59%
47503
Cloud CoverDay
421232345%7%63%
47540
Night
421332445%7%60%
47503
TransparencyDay
19%49%19%25%21%
47262
Night
21%5%8%17%23%23%
47285
SeeingDay
4313%31%30%15%
4953
Night
4219%49%23%1
15304

By Month

Percentage Cloud Cover SW (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
8%32432335%6%56%
1790
16th to endDay
4323324346%60%
1920
February1st to 15thDay
223323445%66%
1750
16th to endDay
3212212246%69%
1580
March1st to 15thDay
2312213347%65%
1851
16th to endDay
3211212445%70%
2214
April1st to 15thDay
1112313346%71%
2150
16th to endDay
1112212236%74%
2160
May1st to 15thDay
2111212345%72%
2151
16th to endDay
1112112346%73%
2243
June1st to 15thDay
1212347%74%
2285
16th to endDay
21122145%6%9%63%
2161
July1st to 15thDay
5%223435%6%7%8%51%
2160
16th to endDay
4223435%5%7%13%47%
2277
August1st to 15thDay
32124246%7%10%53%
2160
16th to endDay
3313435%7%8%11%44%
2292
September1st to 15thDay
7%4144245%6%10%46%
2160
16th to endDay
7%31422345%7%56%
1881
October1st to 15thDay
22222235%6%68%
1780
16th to endDay
321221223472%
1760
November1st to 15thDay
4312222235%69%
1726
16th to endDay
4313222235%66%
1620
December1st to 15thDay
442432345%7%57%
1620
16th to endDay
3314324447%60%
1851
January1st to 15thNight
6%21322335%6%61%
2148
16th to endNight
5%21332345%6%60%
2304
February1st to 15thNight
2212213247%68%
2102
16th to endNight
321231445%7%64%
1894
March1st to 15thNight
3313323337%64%
2106
16th to endNight
4311212347%66%
2010
April1st to 15thNight
321331435%6%65%
1798
16th to endNight
2212212345%71%
1800
May1st to 15thNight
4213213445%65%
1799
16th to endNight
42123245%7%7%58%
1870
June1st to 15thNight
21133245%9%11%54%
1662
16th to endNight
2113435%5%7%11%52%
1784
July1st to 15thNight
3213436%6%7%13%47%
1800
16th to endNight
42246%46%7%7%12%41%
1891
August1st to 15thNight
32135%36%8%8%11%44%
1800
16th to endNight
43245%47%8%9%11%37%
1910
September1st to 15thNight
44245%36%7%7%10%44%
1800
16th to endNight
5%3237%35%7%7%9%43%
1888
October1st to 15thNight
331342435%7%59%
1846
16th to endNight
2112212235%73%
2112
November1st to 15thNight
31121224474%
2118
16th to endNight
421221224472%
2340
December1st to 15thNight
4312222347%64%
2340
16th to endNight
3313323346%65%
2381

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
8%323423447%56%
1790
16th to endDay
5%324314345%61%
1920
February1st to 15thDay
223423445%66%
1750
16th to endDay
3211212237%70%
1580
March1st to 15thDay
332213446%65%
1851
16th to endDay
3212213345%70%
2212
April1st to 15thDay
212313336%71%
2150
16th to endDay
211122236%74%
2160
May1st to 15thDay
2211213335%72%
2151
16th to endDay
211112346%73%
2243
June1st to 15thDay
11112347%75%
2285
16th to endDay
22112135%5%9%63%
2161
July1st to 15thDay
5%213335%5%6%8%52%
2160
16th to endDay
4223425%5%8%12%47%
2277
August1st to 15thDay
32124245%7%10%54%
2160
16th to endDay
4314435%7%8%12%44%
2292
September1st to 15thDay
8%3244245%6%9%48%
2160
16th to endDay
7%314314446%57%
1881
October1st to 15thDay
31221235%6%68%
1780
16th to endDay
311311223472%
1760
November1st to 15thDay
4312212235%69%
1726
16th to endDay
4323222226%66%
1620
December1st to 15thDay
442342345%7%57%
1620
16th to endDay
4313323348%60%
1851
January1st to 15thNight
6%21321335%6%62%
2148
16th to endNight
6%21332335%6%60%
2304
February1st to 15thNight
2212213247%68%
2102
16th to endNight
321221435%6%65%
1894
March1st to 15thNight
5%312323436%63%
2106
16th to endNight
4312212346%67%
2010
April1st to 15thNight
221232435%6%65%
1798
16th to endNight
221221234471%
1800
May1st to 15thNight
4212313445%65%
1799
16th to endNight
42123245%6%7%58%
1870
June1st to 15thNight
21123245%9%10%54%
1662
16th to endNight
3113435%5%7%11%52%
1784
July1st to 15thNight
32135%35%5%8%12%48%
1800
16th to endNight
42246%45%7%6%12%41%
1891
August1st to 15thNight
4213436%8%8%10%45%
1800
16th to endNight
5%3245%47%7%9%12%37%
1910
September1st to 15thNight
44245%36%7%7%9%44%
1800
16th to endNight
5%3246%46%6%7%9%43%
1888
October1st to 15thNight
421342445%7%60%
1846
16th to endNight
3112212235%73%
2112
November1st to 15thNight
321211245%74%
2118
16th to endNight
421121233471%
2340
December1st to 15thNight
4312222347%64%
2340
16th to endNight
3313322345%65%
2381

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
26%47%22%27%11%
1791
16th to endDay
23%36%20%33%13%
1920
February1st to 15thDay
18%35%13%28%29%
1751
16th to endDay
15%2413%36%26%
1580
March1st to 15thDay
17%36%16%27%28%
1851
16th to endDay
17%2412%26%36%
2214
April1st to 15thDay
15%25%10%26%38%
2150
16th to endDay
12%1410%22%48%
2160
May1st to 15thDay
13%3413%23%40%
2151
16th to endDay
12%37%16%24%36%
2246
June1st to 15thDay
9%37%17%31%30%
2285
16th to endDay
16%412%20%27%19%
2161
July1st to 15thDay
26%8%13%23%19%8%
2031
16th to endDay
25%8%19%26%15%4
2134
August1st to 15thDay
21%8%16%30%19%3
2147
16th to endDay
27%9%17%23%14%6%
2292
September1st to 15thDay
31%7%15%22%15%7%
2160
16th to endDay
26%6%11%20%24%11%
1881
October1st to 15thDay
15%410%24%25%19%
1780
16th to endDay
15%25%16%32%28%
1760
November1st to 15thDay
16%27%21%29%22%
1726
16th to endDay
20%37%15%27%26%
1620
December1st to 15thDay
23%48%21%29%11%
1620
16th to endDay
20%37%23%35%9%
1851
January1st to 15thNight
22%36%19%31%16%
2148
16th to endNight
23%26%16%34%17%
2304
February1st to 15thNight
16%36%10%27%34%
2112
16th to endNight
17%45%12%30%29%
1894
March1st to 15thNight
21%3413%23%33%
2106
16th to endNight
17%36%13%23%35%
2010
April1st to 15thNight
17%46%10%21%39%
1798
16th to endNight
15%3412%19%45%
1800
May1st to 15thNight
20%47%12%19%37%
1800
16th to endNight
21%6%9%16%17%28%
1872
June1st to 15thNight
18%8%9%20%24%18%
1662
16th to endNight
22%7%13%18%21%16%
1784
July1st to 15thNight
24%8%17%23%19%7%
1700
16th to endNight
30%9%16%23%16%4
1771
August1st to 15thNight
27%9%14%25%18%4
1789
16th to endNight
33%10%14%21%14%5%
1910
September1st to 15thNight
31%10%15%21%12%7%
1800
16th to endNight
33%8%11%16%16%12%
1888
October1st to 15thNight
22%5%10%19%20%21%
1846
16th to endNight
14%2416%27%33%
2112
November1st to 15thNight
12%28%17%31%26%
2118
16th to endNight
16%36%13%24%34%
2340
December1st to 15thNight
19%47%20%28%19%
2340
16th to endNight
21%25%18%33%18%
2381

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
8%418%34%28%4
90
16th to endDay
29%20%36%25%6%
96
February1st to 15thDay
3210%27%38%17%
90
16th to endDay
8%414%33%30%7%
81
March1st to 15thDay
35%15%36%28%10%
141
16th to endDay
210%21%35%23%7%
288
April1st to 15thDay
39%28%36%20%
269
16th to endDay
410%25%37%18%3
270
May1st to 15thDay
29%26%45%13%1
288
16th to endDay
35%23%38%26%2
330
June1st to 15thDay
210%30%43%13%
440
16th to endDay
29%34%37%16%
316
July1st to 15thDay
6%6%28%30%27%
305
16th to endDay
2427%33%30%
327
August1st to 15thDay
5%423%32%33%
315
16th to endDay
8%6%25%34%24%
332
September1st to 15thDay
5%16%27%35%23%
315
16th to endDay
13%417%29%34%
108
October1st to 15thDay
8%18%20%33%27%
90
16th to endDay
3112%23%26%33%
96
November1st to 15thDay
4214%36%28%13%
90
16th to endDay
13%10%8%28%33%5%
90
December1st to 15thDay
7%27%25%42%14%
90
16th to endDay
10%5%19%36%25%3
96
January1st to 15thNight
7%117%51%20%
720
16th to endNight
5%220%51%19%
768
February1st to 15thNight
4422%48%19%
704
16th to endNight
3229%55%9%
632
March1st to 15thNight
7%328%48%12%
720
16th to endNight
6%327%48%14%
666
April1st to 15thNight
26%37%47%6%
539
16th to endNight
35%35%48%6%
540
May1st to 15thNight
5%6%35%43%7%
540
16th to endNight
4428%51%11%
563
June1st to 15thNight
221%53%21%
540
16th to endNight
214%57%23%
540
July1st to 15thNight
211%55%27%1
510
16th to endNight
41446%38%4
564
August1st to 15thNight
4338%48%4
539
16th to endNight
5%441%43%4
573
September1st to 15thNight
419%47%35%2
540
16th to endNight
7%9%51%29%1
513
October1st to 15thNight
5%13%53%25%1
526
16th to endNight
316%41%33%4
704
November1st to 15thNight
4112%48%30%1
718
16th to endNight
5%214%48%27%1
900
December1st to 15thNight
6%115%50%26%
900
16th to endNight
4221%51%19%1
845
Page generated at 2017-09-23 05:43:39. Version ac04

Copyright 2017 A. Danko


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