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 2019-06-24.

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%
17356
23%
54117
17%
17312
59%
17312
29%
32647

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
32%
840
28%
2529
13%
836
47%
836
27%
1527
January16th to endNight
30%
896
26%
2688
12%
896
42%
896
25%
1701
February1st to 15thNight
32%
824
24%
2471
12%
821
42%
821
25%
1562
February16th to endNight
24%
735
23%
2205
8%
735
36%
735
22%
1451
March1st to 15thNight
30%
840
22%
2520
11%
840
39%
840
24%
1617
March16th to endNight
40%
686
26%
2323
15%
686
52%
686
30%
1316
April1st to 15thNight
43%
629
24%
2097
19%
629
52%
629
29%
1227
April16th to endNight
52%
624
29%
2078
23%
624
63%
624
39%
1074
May1st to 15thNight
58%
629
24%
2100
21%
629
66%
629
35%
1159
May16th to endNight
67%
658
23%
1980
19%
657
72%
657
35%
1172
June1st to 15thNight
72%
630
16%
1890
16%
630
73%
630
33%
1156
June16th to endNight
75%
609
18%
1828
17%
609
76%
609
33%
1126
July1st to 15thNight
80%
555
12%
1739
14%
555
80%
555
30%
1091
July16th to endNight
80%
612
13%
1932
15%
579
80%
579
26%
1220
August1st to 15thNight
81%
575
11%
1906
13%
572
81%
572
29%
1161
August16th to endNight
71%
621
15%
2070
18%
621
71%
621
24%
1367
September1st to 15thNight
68%
608
18%
1973
18%
608
69%
608
25%
1255
September16th to endNight
66%
777
27%
2145
22%
777
68%
777
32%
1337
October1st to 15thNight
61%
780
33%
2150
23%
780
67%
780
41%
1230
October16th to endNight
55%
832
35%
2496
28%
832
63%
832
42%
1337
November1st to 15thNight
54%
820
30%
2625
24%
820
62%
820
35%
1440
November16th to endNight
48%
840
30%
2730
23%
840
59%
840
34%
1501
December1st to 15thNight
38%
840
26%
2730
18%
840
49%
840
26%
1655
December16th to endNight
30%
896
19%
2912
12%
896
39%
896
20%
1965

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%6%35%5%5%7%40%
54672
Night
11%42442445%8%46%
54336
TransparencyDay
41%5%10%17%18%6%
54393
Night
35%6%12%18%19%8%
54120
SeeingDay
14%6%17%23%23%14%
7264
Night
13%6%21%29%23%5%
17358

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%
2065
16th to endDay
19%5%2442323447%
2240
February1st to 15thDay
15%6%25%5%24446%41%
2050
16th to endDay
17%6%35%5%24446%39%
1840
March1st to 15thDay
15%6%25%5%25%445%41%
2100
16th to endDay
12%6%25%5%34435%46%
2613
April1st to 15thDay
13%5%25%5%3345%7%42%
2511
16th to endDay
9%4145%25%5%5%8%46%
2487
May1st to 15thDay
11%415%6%36%5%5%7%42%
2511
16th to endDay
8%426%6%46%5%5%7%41%
2835
June1st to 15thDay
7%426%7%5%6%6%7%10%34%
2730
16th to endDay
6%436%7%5%8%7%7%9%33%
2639
July1st to 15thDay
8%6%47%8%5%8%8%7%9%24%
2451
16th to endDay
8%5%37%8%48%7%8%10%25%
2468
August1st to 15thDay
6%5%36%8%5%7%7%8%10%29%
2295
16th to endDay
13%6%37%7%47%6%48%30%
2484
September1st to 15thDay
10%6%37%6%45%6%6%6%36%
2304
16th to endDay
9%5%25%5%3445%5%46%
2145
October1st to 15thDay
8%41341345%6%54%
2137
16th to endDay
8%313423447%55%
2080
November1st to 15thDay
12%5%25%322345%53%
1891
16th to endDay
10%414423246%53%
1890
December1st to 15thDay
16%7%34433345%42%
1890
16th to endDay
23%8%34424345%35%
2016
January1st to 15thNight
15%6%24323347%47%
2529
16th to endNight
18%6%2442234445%
2688
February1st to 15thNight
14%6%25%5%24445%45%
2463
16th to endNight
17%6%25%423346%42%
2205
March1st to 15thNight
14%5%26%424446%43%
2520
16th to endNight
11%425%323347%50%
2323
April1st to 15thNight
11%43442436%7%46%
2097
16th to endNight
8%413323346%57%
2078
May1st to 15thNight
8%31332446%9%51%
2099
16th to endNight
6%3144246%7%9%48%
1980
June1st to 15thNight
5%5%245%35%5%7%12%41%
1890
16th to endNight
5%424435%7%9%11%42%
1828
July1st to 15thNight
4425%6%45%6%8%11%40%
1835
16th to endNight
43246%47%7%9%12%38%
2052
August1st to 15thNight
5%313437%7%10%14%36%
1918
16th to endNight
8%425%6%45%6%8%12%35%
2070
September1st to 15thNight
9%425%6%45%6%7%7%40%
1973
16th to endNight
7%425%5%35%5%5%8%45%
2145
October1st to 15thNight
8%413423448%54%
2150
16th to endNight
11%413212235%60%
2496
November1st to 15thNight
12%413323347%53%
2625
16th to endNight
10%424323445%54%
2730
December1st to 15thNight
15%6%24424347%45%
2730
16th to endNight
19%7%36%5%23345%37%
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
41%35%18%22%9%
2066
16th to endDay
41%2415%27%8%
2240
February1st to 15thDay
43%47%15%21%7%
2052
16th to endDay
45%45%16%20%7%
1840
March1st to 15thDay
44%46%15%20%8%
2100
16th to endDay
40%48%16%24%5%
2615
April1st to 15thDay
39%47%19%20%7%
2511
16th to endDay
34%5%8%21%23%6%
2487
May1st to 15thDay
39%5%9%16%21%5%
2511
16th to endDay
40%6%11%21%16%2
2839
June1st to 15thDay
42%7%14%21%12%1
2730
16th to endDay
42%9%17%20%9%1
2639
July1st to 15thDay
50%10%17%14%6%1
2318
16th to endDay
47%10%20%16%4
2325
August1st to 15thDay
44%10%20%15%8%
2283
16th to endDay
50%9%14%13%9%2
2484
September1st to 15thDay
45%6%14%17%11%4
2304
16th to endDay
37%6%10%20%18%7%
2145
October1st to 15thDay
28%49%21%24%12%
2137
16th to endDay
29%35%15%28%17%
2080
November1st to 15thDay
33%27%18%27%10%
1891
16th to endDay
32%36%17%25%15%
1890
December1st to 15thDay
44%36%18%19%7%
1890
16th to endDay
51%37%18%15%4
2016
January1st to 15thNight
37%37%18%25%8%
2529
16th to endNight
42%25%15%25%8%
2688
February1st to 15thNight
40%48%16%18%11%
2472
16th to endNight
44%4415%19%10%
2205
March1st to 15thNight
41%48%15%21%8%
2520
16th to endNight
34%39%20%23%8%
2323
April1st to 15thNight
35%410%17%21%9%
2097
16th to endNight
26%410%23%26%8%
2078
May1st to 15thNight
28%7%12%22%22%7%
2100
16th to endNight
29%8%15%23%19%3
1982
June1st to 15thNight
32%8%19%23%14%1
1890
16th to endNight
31%9%19%25%11%2
1828
July1st to 15thNight
31%11%28%18%7%1
1739
16th to endNight
32%13%24%24%4
1932
August1st to 15thNight
30%12%30%16%8%2
1906
16th to endNight
38%11%22%14%9%3
2070
September1st to 15thNight
39%8%18%16%11%6%
1973
16th to endNight
34%7%11%21%17%7%
2145
October1st to 15thNight
27%5%10%20%20%15%
2150
16th to endNight
27%25%15%27%21%
2496
November1st to 15thNight
31%38%18%26%12%
2625
16th to endNight
31%36%17%24%17%
2730
December1st to 15thNight
39%39%20%20%6%
2730
16th to endNight
49%37%18%17%4
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
22%15%30%17%10%3
180
16th to endDay
26%18%29%18%7%
192
February1st to 15thDay
29%17%32%17%2
180
16th to endDay
23%15%40%18%1
159
March1st to 15thDay
18%24%38%15%2
180
16th to endDay
18%13%24%28%14%
346
April1st to 15thDay
21%12%24%24%15%2
390
16th to endDay
11%8%23%31%20%3
379
May1st to 15thDay
12%5%22%26%24%8%
408
16th to endDay
10%116%29%21%19%
459
June1st to 15thDay
10%110%28%30%18%
435
16th to endDay
8%28%23%30%25%
407
July1st to 15thDay
9%315%35%36%
365
16th to endDay
6%25%21%32%32%
390
August1st to 15thDay
10%5%15%36%31%
358
16th to endDay
13%1317%37%27%
396
September1st to 15thDay
10%211%19%34%21%
375
16th to endDay
11%7%28%33%17%
374
October1st to 15thDay
10%314%27%33%10%
367
16th to endDay
14%7%25%29%16%6%
192
November1st to 15thDay
23%8%28%28%8%2
180
16th to endDay
10%14%29%25%16%4
180
December1st to 15thDay
23%15%35%17%5%1
180
16th to endDay
35%9%26%18%9%
192
January1st to 15thNight
20%13%29%29%7%
840
16th to endNight
22%12%30%29%5%
896
February1st to 15thNight
18%12%31%30%6%
824
16th to endNight
19%14%36%25%3
735
March1st to 15thNight
18%13%32%28%7%
840
16th to endNight
14%7%33%31%12%
686
April1st to 15thNight
14%9%29%29%17%
629
16th to endNight
10%429%34%20%
624
May1st to 15thNight
9%322%39%22%3
630
16th to endNight
7%115%34%33%7%
659
June1st to 15thNight
7%17%33%40%10%
630
16th to endNight
415%27%47%12%
609
July1st to 15thNight
41320%48%23%
555
16th to endNight
4421%46%21%
612
August1st to 15thNight
5%220%48%23%
575
16th to endNight
11%1318%46%19%
621
September1st to 15thNight
9%18%24%41%14%
608
16th to endNight
10%110%31%40%6%
777
October1st to 15thNight
10%119%29%32%6%
780
16th to endNight
13%421%30%26%3
832
November1st to 15thNight
13%5%21%35%19%3
820
16th to endNight
11%8%25%35%18%1
840
December1st to 15thNight
19%10%27%29%13%
840
16th to endNight
23%9%31%25%9%
896
Page generated at 2019-06-24 19:41:31. Version ac04

Copyright 2019 A. Danko


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