Jackson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jackson clear sky chart from 2005-11-05 to 2017-04-30.

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
36%
15476
15%
45569
10%
15434
41%
15434
20%
32180

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
14%
900
9%
2506
3%
895
20%
895
12%
2003
January16th to endNight
20%
894
7%
2622
3%
894
24%
894
10%
2147
February1st to 15thNight
18%
701
9%
2224
3%
701
24%
701
11%
1735
February16th to endNight
22%
631
14%
1893
6%
631
30%
631
14%
1409
March1st to 15thNight
28%
720
14%
2100
9%
720
32%
720
18%
1526
March16th to endNight
31%
768
17%
2112
10%
768
38%
768
20%
1516
April1st to 15thNight
26%
554
12%
1806
7%
554
33%
554
18%
1264
April16th to endNight
36%
537
18%
1612
8%
537
44%
537
23%
1078
May1st to 15thNight
35%
495
14%
1485
7%
495
42%
495
20%
1063
May16th to endNight
52%
514
14%
1502
10%
513
57%
513
29%
953
June1st to 15thNight
51%
495
16%
1320
11%
495
56%
495
32%
872
June16th to endNight
58%
495
14%
1320
11%
495
61%
495
33%
843
July1st to 15thNight
65%
465
18%
1240
15%
465
67%
465
40%
739
July16th to endNight
68%
522
18%
1355
15%
489
70%
489
37%
818
August1st to 15thNight
68%
494
21%
1474
17%
491
70%
491
34%
863
August16th to endNight
65%
525
20%
1633
17%
525
68%
525
33%
959
September1st to 15thNight
60%
591
27%
1746
22%
591
64%
591
33%
1050
September16th to endNight
58%
657
22%
1815
17%
657
61%
657
33%
1141
October1st to 15thNight
46%
660
21%
1873
17%
660
51%
660
28%
1224
October16th to endNight
26%
704
15%
2233
9%
704
35%
704
17%
1569
November1st to 15thNight
35%
700
19%
2276
16%
700
40%
700
21%
1486
November16th to endNight
25%
720
13%
2340
9%
720
31%
720
13%
1739
December1st to 15thNight
19%
774
8%
2394
4%
774
24%
774
10%
1910
December16th to endNight
14%
960
7%
2688
1%
960
19%
960
8%
2273

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
14%9%47%6%35%5%5%7%32%
46162
Night
15%9%46%5%34446%34%
45744
Cloud CoverDay
14%8%46%6%35%5%5%7%32%
46171
Night
15%8%46%5%3445%6%34%
45749
TransparencyDay
50%6%12%18%10%1
45855
Night
49%6%12%19%11%1
45569
SeeingDay
16%7%27%24%16%7%
5291
Night
18%8%29%29%12%1
15480

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
17%15%7%9%8%5%5%435%15%
1432
16th to endDay
14%17%9%12%9%4433415%
1599
February1st to 15thDay
13%15%6%10%8%46%436%19%
1636
16th to endDay
15%12%6%12%7%45%5%5%5%19%
1580
March1st to 15thDay
16%10%5%8%6%35%5%47%26%
1849
16th to endDay
17%10%37%6%24446%30%
2112
April1st to 15thDay
19%11%45%5%24346%30%
2153
16th to endDay
15%7%26%5%25%447%37%
2327
May1st to 15thDay
18%8%36%6%35%45%6%30%
2136
16th to endDay
13%7%25%5%345%5%7%39%
2259
June1st to 15thDay
10%6%25%6%35%5%6%9%37%
2310
16th to endDay
9%5%35%6%37%6%7%10%35%
2310
July1st to 15thDay
7%4245%35%6%6%8%44%
2310
16th to endDay
8%425%5%46%6%6%10%38%
2404
August1st to 15thDay
8%425%6%35%6%7%8%39%
2145
16th to endDay
12%5%25%5%35%5%5%8%39%
2215
September1st to 15thDay
13%5%245%345%6%8%41%
1873
16th to endDay
11%6%35%435%6%5%9%39%
1815
October1st to 15thDay
13%7%36%6%34447%38%
1757
16th to endDay
20%9%36%5%44446%31%
1637
November1st to 15thDay
14%8%37%5%24446%38%
1582
16th to endDay
18%13%5%8%6%35%445%25%
1620
December1st to 15thDay
14%14%9%10%6%3446%422%
1565
16th to endDay
20%17%8%10%8%34335%15%
1536
January1st to 15thNight
20%13%6%8%7%34345%21%
2506
16th to endNight
13%12%8%11%9%5%6%45%6%17%
2622
February1st to 15thNight
15%13%7%9%6%35%43426%
2222
16th to endNight
15%10%5%8%6%45%5%46%26%
1893
March1st to 15thNight
16%11%46%6%24346%33%
2087
16th to endNight
15%7%46%5%35%6%5%6%33%
2112
April1st to 15thNight
18%8%35%435%5%5%5%34%
1806
16th to endNight
16%7%26%434447%38%
1612
May1st to 15thNight
20%7%26%6%3446%7%31%
1485
16th to endNight
12%5%2442445%8%45%
1500
June1st to 15thNight
10%5%35%43446%7%45%
1320
16th to endNight
7%4345%245%8%10%43%
1320
July1st to 15thNight
5%4244245%5%8%52%
1320
16th to endNight
6%3244245%7%9%50%
1456
August1st to 15thNight
6%3244446%6%8%48%
1485
16th to endNight
11%424423447%50%
1633
September1st to 15thNight
11%5%24423336%51%
1746
16th to endNight
11%5%2432445%7%46%
1815
October1st to 15thNight
14%5%25%5%24446%43%
1873
16th to endNight
20%7%36%5%24345%34%
2233
November1st to 15thNight
14%9%35%5%2435%5%39%
2276
16th to endNight
18%13%5%7%5%24445%27%
2340
December1st to 15thNight
21%12%5%9%6%34445%21%
2394
16th to endNight
21%16%6%10%6%35%445%15%
2688

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
17%15%6%8%8%46%435%16%
1432
16th to endDay
14%17%10%11%9%45%24415%
1599
February1st to 15thDay
13%13%7%10%8%47%436%19%
1636
16th to endDay
15%12%6%12%6%45%5%5%5%19%
1580
March1st to 15thDay
16%10%5%8%5%35%5%5%6%26%
1859
16th to endDay
18%10%36%6%2445%6%29%
2111
April1st to 15thDay
19%11%35%5%34346%30%
2153
16th to endDay
16%6%36%5%2445%7%37%
2327
May1st to 15thDay
18%8%36%6%35%45%6%30%
2136
16th to endDay
13%6%345%35%46%8%39%
2259
June1st to 15thDay
10%6%25%6%35%46%9%37%
2310
16th to endDay
10%425%6%36%7%6%9%35%
2310
July1st to 15thDay
7%4246%35%6%6%8%44%
2310
16th to endDay
8%5%25%5%46%6%6%10%38%
2404
August1st to 15thDay
9%425%6%36%5%6%8%40%
2145
16th to endDay
12%5%25%5%35%5%5%8%39%
2215
September1st to 15thDay
13%5%25%5%35%5%5%8%41%
1873
16th to endDay
11%6%25%5%25%5%5%9%39%
1815
October1st to 15thDay
14%7%26%6%34447%39%
1757
16th to endDay
20%9%26%5%43446%31%
1637
November1st to 15thDay
14%8%36%424446%38%
1582
16th to endDay
18%12%6%7%6%35%445%25%
1620
December1st to 15thDay
15%14%8%10%5%3445%422%
1565
16th to endDay
20%16%8%10%6%24335%15%
1536
January1st to 15thNight
21%13%6%8%7%34345%21%
2506
16th to endNight
13%12%8%11%9%5%6%45%6%17%
2622
February1st to 15thNight
15%13%6%9%6%34445%26%
2215
16th to endNight
15%10%5%9%6%45%45%6%27%
1893
March1st to 15thNight
17%10%45%5%34346%33%
2100
16th to endNight
16%8%35%5%35%5%5%6%33%
2112
April1st to 15thNight
18%7%34435%45%5%34%
1806
16th to endNight
16%7%25%43445%7%38%
1612
May1st to 15thNight
20%7%16%6%34447%32%
1484
16th to endNight
12%5%2443345%8%44%
1500
June1st to 15thNight
11%435%43445%7%44%
1320
16th to endNight
7%4245%245%8%10%43%
1320
July1st to 15thNight
5%425%42445%8%52%
1320
16th to endNight
6%314425%46%9%50%
1456
August1st to 15thNight
7%3145%345%6%9%48%
1485
16th to endNight
11%424423447%50%
1633
September1st to 15thNight
12%5%23423336%52%
1746
16th to endNight
12%5%2432445%7%46%
1815
October1st to 15thNight
14%5%2442445%6%43%
1873
16th to endNight
19%9%35%6%24345%35%
2233
November1st to 15thNight
14%8%35%5%2435%5%40%
2276
16th to endNight
19%12%5%7%5%24446%28%
2340
December1st to 15thNight
21%12%6%9%6%3435%5%22%
2394
16th to endNight
21%16%6%9%5%35%445%15%
2688

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
70%412%9%3
1433
16th to endDay
73%49%8%3
1599
February1st to 15thDay
66%5%8%12%5%
1638
16th to endDay
64%5%11%13%4
1580
March1st to 15thDay
56%7%12%16%6%1
1859
16th to endDay
53%6%11%19%7%
2112
April1st to 15thDay
55%49%19%10%
2153
16th to endDay
45%5%13%17%14%2
2327
May1st to 15thDay
53%7%11%18%8%
2136
16th to endDay
42%6%13%24%11%1
2263
June1st to 15thDay
41%6%14%22%14%1
2310
16th to endDay
41%10%12%18%16%1
2310
July1st to 15thDay
35%8%11%22%20%2
2161
16th to endDay
37%9%15%21%14%1
2242
August1st to 15thDay
38%8%13%24%13%1
2132
16th to endDay
40%7%11%22%15%2
2215
September1st to 15thDay
39%7%13%22%15%1
1873
16th to endDay
39%6%12%25%15%
1815
October1st to 15thDay
44%5%11%24%12%1
1757
16th to endDay
53%5%13%19%6%
1637
November1st to 15thDay
45%6%9%22%14%1
1582
16th to endDay
60%412%17%4
1620
December1st to 15thDay
63%7%11%13%3
1565
16th to endDay
72%5%11%7%3
1536
January1st to 15thNight
64%311%13%5%
2506
16th to endNight
66%6%14%9%3
2622
February1st to 15thNight
60%7%9%15%5%1
2224
16th to endNight
58%412%18%5%1
1893
March1st to 15thNight
51%6%12%17%9%1
2100
16th to endNight
48%7%11%21%10%1
2112
April1st to 15thNight
49%6%11%17%14%
1806
16th to endNight
45%412%17%16%3
1612
May1st to 15thNight
50%6%11%20%10%1
1485
16th to endNight
37%7%13%23%14%3
1502
June1st to 15thNight
37%6%12%27%14%1
1320
16th to endNight
32%9%17%22%17%
1320
July1st to 15thNight
29%5%12%27%21%3
1240
16th to endNight
27%9%14%24%20%2
1355
August1st to 15thNight
30%7%14%28%17%1
1474
16th to endNight
34%411%27%18%4
1633
September1st to 15thNight
34%5%7%28%20%2
1746
16th to endNight
35%6%13%26%17%
1815
October1st to 15thNight
40%5%11%22%18%1
1873
16th to endNight
50%5%12%22%8%
2233
November1st to 15thNight
45%5%12%21%13%2
2276
16th to endNight
57%412%18%6%
2340
December1st to 15thNight
64%5%11%13%5%
2394
16th to endNight
70%6%10%9%4
2688

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%14%43%15%4
90
16th to endDay
27%13%38%17%3
96
February1st to 15thDay
21%17%45%15%
90
16th to endDay
20%13%40%19%4
81
March1st to 15thDay
28%12%32%20%6%
149
16th to endDay
22%9%35%22%8%2
288
April1st to 15thDay
23%10%31%25%7%1
270
16th to endDay
19%8%31%22%11%7%
266
May1st to 15thDay
23%7%29%20%13%6%
228
16th to endDay
15%8%22%24%19%9%
303
June1st to 15thDay
13%6%30%29%14%5%
420
16th to endDay
13%5%27%30%17%6%
420
July1st to 15thDay
9%323%29%22%12%
400
16th to endDay
9%224%27%23%11%
390
August1st to 15thDay
10%16%26%25%21%
253
16th to endDay
15%217%20%25%18%
268
September1st to 15thDay
14%217%19%29%16%
255
16th to endDay
14%5%15%24%28%10%
254
October1st to 15thDay
14%6%23%32%16%6%
255
16th to endDay
26%11%28%26%6%
149
November1st to 15thDay
416%25%36%12%4
90
16th to endDay
24%15%41%11%7%
90
December1st to 15thDay
22%28%33%12%3
90
16th to endDay
25%32%36%6%
96
January1st to 15thNight
26%13%37%17%4
900
16th to endNight
16%12%38%27%5%
894
February1st to 15thNight
21%13%37%22%3
704
16th to endNight
22%11%36%26%4
631
March1st to 15thNight
22%12%31%26%6%
720
16th to endNight
18%9%36%24%9%
768
April1st to 15thNight
20%12%35%25%5%
554
16th to endNight
19%6%33%27%10%1
537
May1st to 15thNight
24%5%27%31%9%2
495
16th to endNight
14%224%35%20%2
515
June1st to 15thNight
12%226%44%13%
495
16th to endNight
7%222%42%21%3
495
July1st to 15thNight
7%116%43%26%3
465
16th to endNight
6%116%45%28%1
522
August1st to 15thNight
8%14%47%24%4
494
16th to endNight
12%112%34%32%6%
525
September1st to 15thNight
14%316%33%26%5%
591
16th to endNight
14%416%30%29%4
657
October1st to 15thNight
16%6%25%31%18%2
660
16th to endNight
23%13%33%22%7%
704
November1st to 15thNight
19%10%30%28%11%1
700
16th to endNight
25%13%30%23%6%
720
December1st to 15thNight
25%12%36%21%3
774
16th to endNight
29%11%36%18%3
960
Page generated at 2017-04-30 20:40:10. Version ac04

Copyright 2017 A. Danko


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