State Line Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the State Line Area clear sky chart from 2005-11-05 to 2017-09-23.

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
52%
15099
24%
47092
17%
15055
59%
15055
30%
28232

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
33%
720
28%
2166
12%
716
47%
716
27%
1304
January16th to endNight
28%
768
26%
2304
11%
768
41%
768
25%
1458
February1st to 15thNight
34%
704
26%
2111
12%
701
45%
701
28%
1278
February16th to endNight
26%
631
25%
1893
9%
631
39%
631
24%
1208
March1st to 15thNight
32%
720
22%
2160
12%
720
41%
720
25%
1371
March16th to endNight
42%
588
27%
1991
17%
588
53%
588
30%
1120
April1st to 15thNight
45%
539
24%
1797
19%
539
54%
539
30%
1033
April16th to endNight
51%
540
29%
1800
23%
540
62%
540
37%
941
May1st to 15thNight
55%
539
20%
1800
16%
539
63%
539
32%
1022
May16th to endNight
66%
562
23%
1690
20%
561
71%
561
35%
997
June1st to 15thNight
72%
540
14%
1620
14%
540
72%
540
32%
1001
June16th to endNight
76%
540
19%
1620
18%
540
76%
540
33%
1001
July1st to 15thNight
80%
510
12%
1598
14%
510
80%
510
30%
995
July16th to endNight
80%
564
13%
1772
16%
531
80%
531
26%
1128
August1st to 15thNight
81%
539
11%
1788
14%
536
81%
536
30%
1086
August16th to endNight
69%
573
16%
1910
19%
573
69%
573
23%
1275
September1st to 15thNight
68%
561
19%
1821
19%
561
69%
561
26%
1137
September16th to endNight
65%
689
27%
1903
22%
689
67%
689
33%
1184
October1st to 15thNight
59%
660
33%
1819
23%
660
66%
660
41%
1038
October16th to endNight
56%
704
35%
2112
29%
704
63%
704
44%
1108
November1st to 15thNight
55%
700
32%
2241
26%
700
65%
700
37%
1190
November16th to endNight
46%
720
30%
2340
22%
720
57%
720
34%
1292
December1st to 15thNight
39%
720
25%
2340
19%
720
49%
720
26%
1401
December16th to endNight
30%
768
20%
2496
13%
768
39%
768
20%
1664

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
11%5%25%5%35%5%5%7%40%
47784
Night
11%42442445%8%46%
47311
TransparencyDay
41%5%10%17%18%6%
47505
Night
34%5%12%18%19%8%
47095
SeeingDay
13%5%15%23%26%16%
5049
Night
13%6%21%29%24%5%
15101

By Month

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%6%24423346%44%
1769
16th to endDay
19%5%24413235%47%
1920
February1st to 15thDay
13%5%25%424446%45%
1750
16th to endDay
17%6%25%5%23345%42%
1580
March1st to 15thDay
15%6%35%5%34446%41%
1800
16th to endDay
12%5%26%5%34435%45%
2239
April1st to 15thDay
13%5%25%5%3345%7%42%
2151
16th to endDay
9%425%5%35%5%5%8%44%
2160
May1st to 15thDay
12%415%6%36%5%5%7%39%
2151
16th to endDay
9%436%7%46%5%5%7%39%
2421
June1st to 15thDay
7%5%26%7%5%6%7%7%10%33%
2340
16th to endDay
6%436%7%5%8%7%7%10%33%
2340
July1st to 15thDay
9%6%47%8%48%8%7%9%25%
2262
16th to endDay
9%6%37%8%48%7%8%10%25%
2276
August1st to 15thDay
7%5%37%8%5%6%7%8%10%29%
2160
16th to endDay
13%6%37%7%47%6%47%30%
2292
September1st to 15thDay
10%6%37%6%35%6%6%6%37%
2127
16th to endDay
9%5%25%5%345%5%6%46%
1894
October1st to 15thDay
8%41341445%6%54%
1809
16th to endDay
8%313423446%56%
1760
November1st to 15thDay
10%5%25%312246%56%
1615
16th to endDay
12%423423245%54%
1620
December1st to 15thDay
15%7%34433345%42%
1620
16th to endDay
22%8%345%23335%36%
1728
January1st to 15thNight
15%5%24323347%48%
2166
16th to endNight
19%6%2432234445%
2304
February1st to 15thNight
14%5%24423445%49%
2103
16th to endNight
17%6%25%423335%45%
1893
March1st to 15thNight
15%5%25%424446%44%
2160
16th to endNight
11%425%423347%51%
1991
April1st to 15thNight
11%324325%36%7%47%
1797
16th to endNight
8%413323347%56%
1800
May1st to 15thNight
9%32332447%9%48%
1799
16th to endNight
7%3144246%7%9%47%
1690
June1st to 15thNight
5%5%25%5%35%5%7%12%40%
1620
16th to endNight
5%424435%6%9%12%41%
1620
July1st to 15thNight
4425%5%45%6%8%11%40%
1694
16th to endNight
43246%47%8%9%13%37%
1892
August1st to 15thNight
5%3135%37%7%10%14%37%
1800
16th to endNight
8%5%25%6%45%6%7%12%34%
1910
September1st to 15thNight
8%425%6%45%6%6%7%41%
1821
16th to endNight
8%425%5%35%5%5%8%45%
1903
October1st to 15thNight
9%413323447%55%
1819
16th to endNight
11%413111235%61%
2112
November1st to 15thNight
10%313323347%56%
2241
16th to endNight
11%425%323345%54%
2340
December1st to 15thNight
14%6%14424347%46%
2340
16th to endNight
18%7%35%6%24345%38%
2496

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
41%25%17%22%10%
1770
16th to endDay
41%2414%27%8%
1920
February1st to 15thDay
39%36%16%24%9%
1752
16th to endDay
43%2416%23%8%
1580
March1st to 15thDay
44%37%17%20%7%
1800
16th to endDay
40%48%17%23%5%
2241
April1st to 15thDay
39%47%19%20%8%
2151
16th to endDay
36%5%9%21%22%5%
2160
May1st to 15thDay
42%5%9%16%19%6%
2151
16th to endDay
41%6%12%22%14%2
2425
June1st to 15thDay
42%7%14%22%11%1
2340
16th to endDay
41%8%17%20%10%1
2340
July1st to 15thDay
50%9%17%14%6%1
2129
16th to endDay
48%9%20%15%4
2133
August1st to 15thDay
44%9%20%15%8%
2148
16th to endDay
50%9%13%13%9%2
2292
September1st to 15thDay
44%5%13%18%11%5%
2127
16th to endDay
37%6%9%19%18%8%
1894
October1st to 15thDay
29%39%17%26%14%
1809
16th to endDay
28%35%13%29%19%
1760
November1st to 15thDay
31%26%17%29%12%
1615
16th to endDay
32%26%16%25%15%
1620
December1st to 15thDay
43%37%19%19%7%
1620
16th to endDay
50%26%17%16%5%
1728
January1st to 15thNight
36%36%17%26%9%
2166
16th to endNight
42%25%14%25%9%
2304
February1st to 15thNight
37%37%17%20%13%
2112
16th to endNight
41%4416%22%11%
1893
March1st to 15thNight
41%48%16%22%7%
2160
16th to endNight
34%39%21%23%7%
1991
April1st to 15thNight
34%411%18%20%10%
1797
16th to endNight
27%410%23%25%7%
1800
May1st to 15thNight
30%7%13%20%20%8%
1800
16th to endNight
29%8%15%22%19%3
1692
June1st to 15thNight
33%8%20%23%12%1
1620
16th to endNight
32%8%19%24%12%2
1620
July1st to 15thNight
31%11%28%18%8%1
1598
16th to endNight
32%14%25%23%3
1772
August1st to 15thNight
30%12%29%17%8%2
1788
16th to endNight
39%11%20%13%10%3
1910
September1st to 15thNight
37%7%17%17%12%6%
1821
16th to endNight
35%6%11%20%18%8%
1903
October1st to 15thNight
28%48%17%23%17%
1819
16th to endNight
26%25%15%27%23%
2112
November1st to 15thNight
28%36%17%29%14%
2241
16th to endNight
32%25%17%23%18%
2340
December1st to 15thNight
38%39%21%20%6%
2340
16th to endNight
48%37%17%18%5%
2496

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
20%15%28%21%11%3
90
16th to endDay
26%20%30%15%7%
96
February1st to 15thDay
17%17%36%24%3
90
16th to endDay
20%13%38%25%1
81
March1st to 15thDay
23%22%38%13%2
90
16th to endDay
17%11%21%29%18%
228
April1st to 15thDay
20%11%21%25%18%2
270
16th to endDay
11%7%24%30%22%4
270
May1st to 15thDay
14%6%22%26%21%8%
288
16th to endDay
12%116%30%21%16%
331
June1st to 15thDay
9%10%24%33%21%
315
16th to endDay
8%17%23%30%27%
315
July1st to 15thDay
9%215%38%34%
305
16th to endDay
6%1419%32%35%
326
August1st to 15thDay
11%416%36%30%
313
16th to endDay
13%1318%36%27%
332
September1st to 15thDay
10%211%18%36%20%
315
16th to endDay
12%6%30%32%17%
283
October1st to 15thDay
8%416%26%35%7%
249
16th to endDay
16%217%30%20%12%
96
November1st to 15thDay
21%7%32%27%6%4
90
16th to endDay
12%14%30%27%13%2
90
December1st to 15thDay
23%11%40%18%33
90
16th to endDay
34%11%21%19%11%1
96
January1st to 15thNight
20%13%29%29%6%
720
16th to endNight
23%12%30%27%4
768
February1st to 15thNight
17%12%31%31%6%
704
16th to endNight
19%15%33%26%3
631
March1st to 15thNight
19%12%32%28%7%
720
16th to endNight
14%7%31%31%13%
588
April1st to 15thNight
13%8%29%30%17%
539
16th to endNight
11%429%34%19%
540
May1st to 15thNight
10%324%36%22%2
540
16th to endNight
7%117%34%34%4
563
June1st to 15thNight
7%16%33%40%10%
540
16th to endNight
5%25%26%48%12%
540
July1st to 15thNight
31320%49%21%
510
16th to endNight
4321%47%21%
564
August1st to 15thNight
5%220%49%22%
539
16th to endNight
12%1318%45%18%
573
September1st to 15thNight
8%18%24%42%13%
561
16th to endNight
10%111%31%39%5%
689
October1st to 15thNight
10%121%29%32%4
660
16th to endNight
13%5%20%29%27%3
704
November1st to 15thNight
12%5%22%35%21%4
700
16th to endNight
12%8%26%34%16%
720
December1st to 15thNight
18%10%27%30%13%
720
16th to endNight
22%10%31%25%10%
768
Page generated at 2017-09-24 08:15:48. Version ac04

Copyright 2017 A. Danko


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