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 2017-12-04.

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
37%
16216
15%
47751
10%
16174
42%
16174
20%
33531

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
6%
2622
3%
894
23%
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
37%
768
20%
1516
April1st to 15thNight
26%
554
12%
1806
7%
554
33%
554
18%
1264
April16th to endNight
36%
540
18%
1620
8%
540
44%
540
23%
1086
May1st to 15thNight
35%
540
13%
1620
7%
540
41%
540
20%
1150
May16th to endNight
50%
562
15%
1642
10%
561
55%
561
28%
1054
June1st to 15thNight
54%
540
15%
1440
10%
540
59%
540
34%
929
June16th to endNight
57%
540
16%
1440
11%
540
61%
540
34%
913
July1st to 15thNight
66%
510
17%
1360
14%
510
68%
510
40%
815
July16th to endNight
68%
564
19%
1472
16%
531
71%
531
38%
877
August1st to 15thNight
70%
539
20%
1609
17%
536
72%
536
35%
940
August16th to endNight
64%
573
21%
1782
19%
573
68%
573
33%
1049
September1st to 15thNight
60%
645
26%
1905
21%
645
64%
645
34%
1137
September16th to endNight
58%
717
25%
1980
19%
717
62%
717
34%
1226
October1st to 15thNight
46%
720
20%
2043
16%
720
51%
720
27%
1353
October16th to endNight
27%
768
17%
2436
11%
768
36%
768
17%
1700
November1st to 15thNight
34%
760
18%
2471
15%
760
40%
760
21%
1635
November16th to endNight
26%
780
14%
2535
9%
780
32%
780
14%
1851
December1st to 15thNight
20%
790
8%
2445
4%
790
24%
790
11%
1943
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
13%8%47%6%35%5%5%7%32%
48744
Night
15%8%46%5%34446%35%
47926
Cloud CoverDay
14%8%46%6%35%5%5%7%33%
48753
Night
15%8%46%5%3445%6%35%
47931
TransparencyDay
49%6%12%19%11%1
48437
Night
48%6%12%20%11%1
47751
SeeingDay
16%7%27%24%16%7%
6169
Night
18%8%29%29%12%1
16220

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
16%7%26%5%25%447%37%
2340
May1st to 15thDay
18%8%36%5%35%447%31%
2331
16th to endDay
13%7%25%5%35%5%5%8%38%
2470
June1st to 15thDay
9%6%25%6%35%5%6%9%39%
2520
16th to endDay
9%5%35%6%37%6%7%10%35%
2520
July1st to 15thDay
7%4245%35%6%5%8%44%
2520
16th to endDay
7%425%5%46%6%6%10%38%
2595
August1st to 15thDay
8%425%6%46%6%6%8%38%
2340
16th to endDay
12%5%25%5%35%5%5%8%39%
2417
September1st to 15thDay
12%5%245%445%6%8%40%
2043
16th to endDay
10%6%24435%5%5%9%41%
1980
October1st to 15thDay
14%7%36%6%34447%38%
1917
16th to endDay
20%9%36%5%34446%31%
1786
November1st to 15thDay
15%8%37%5%23446%37%
1717
16th to endDay
17%13%5%8%6%34445%27%
1755
December1st to 15thDay
14%14%9%9%5%3446%423%
1596
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%5%34447%37%
1620
May1st to 15thNight
20%7%26%6%3445%7%32%
1620
16th to endNight
13%5%244245%48%44%
1640
June1st to 15thNight
9%43443446%7%47%
1440
16th to endNight
7%4345%245%7%10%44%
1440
July1st to 15thNight
6%4244245%5%8%52%
1440
16th to endNight
5%3244245%6%9%50%
1573
August1st to 15thNight
6%3145%446%6%8%49%
1620
16th to endNight
10%424423447%50%
1782
September1st to 15thNight
11%424423436%51%
1905
16th to endNight
11%5%2332445%7%48%
1980
October1st to 15thNight
15%6%25%5%2445%6%41%
2043
16th to endNight
19%7%36%5%24345%35%
2436
November1st to 15thNight
15%9%35%5%2435%5%38%
2471
16th to endNight
18%12%5%7%5%24446%28%
2535
December1st to 15thNight
20%12%5%9%6%34445%22%
2445
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%
2340
May1st to 15thDay
18%7%36%6%35%45%7%31%
2331
16th to endDay
13%7%245%35%46%8%38%
2470
June1st to 15thDay
9%6%25%6%35%46%9%39%
2520
16th to endDay
9%425%6%46%7%6%10%35%
2520
July1st to 15thDay
7%4246%35%6%6%8%44%
2520
16th to endDay
7%5%245%46%6%6%10%39%
2595
August1st to 15thDay
9%425%7%36%5%6%8%39%
2340
16th to endDay
12%5%25%5%35%5%5%8%39%
2417
September1st to 15thDay
12%5%25%5%35%5%5%8%41%
2043
16th to endDay
10%5%245%25%5%5%9%42%
1980
October1st to 15thDay
14%6%26%6%34447%39%
1917
16th to endDay
20%9%26%5%43446%31%
1786
November1st to 15thDay
15%8%36%5%24446%38%
1717
16th to endDay
17%12%6%7%5%34445%27%
1755
December1st to 15thDay
14%14%8%10%5%3445%423%
1596
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%8%25%43445%7%38%
1620
May1st to 15thNight
20%7%15%6%24447%33%
1619
16th to endNight
13%5%2443345%8%43%
1640
June1st to 15thNight
10%42443445%7%47%
1440
16th to endNight
7%4245%245%8%10%43%
1440
July1st to 15thNight
5%3245%2445%8%52%
1440
16th to endNight
5%314425%47%9%50%
1573
August1st to 15thNight
6%3145%345%6%8%48%
1620
16th to endNight
11%5%24423447%50%
1782
September1st to 15thNight
11%423423436%51%
1905
16th to endNight
11%5%2432445%6%48%
1980
October1st to 15thNight
14%6%2443445%6%42%
2043
16th to endNight
18%9%35%5%2434436%
2436
November1st to 15thNight
15%8%35%42435%5%39%
2471
16th to endNight
18%12%46%5%24446%28%
2535
December1st to 15thNight
20%11%6%8%6%3445%5%22%
2445
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
46%5%13%17%14%2
2340
May1st to 15thDay
51%7%10%18%10%1
2331
16th to endDay
43%6%13%23%10%1
2474
June1st to 15thDay
39%6%14%23%14%1
2520
16th to endDay
41%9%12%19%15%1
2520
July1st to 15thDay
35%7%11%23%19%2
2371
16th to endDay
36%9%14%21%16%1
2433
August1st to 15thDay
39%8%13%23%13%1
2327
16th to endDay
40%7%11%22%15%2
2417
September1st to 15thDay
39%7%13%23%14%1
2043
16th to endDay
37%6%12%26%16%
1980
October1st to 15thDay
45%5%10%23%11%2
1917
16th to endDay
53%5%13%19%7%
1786
November1st to 15thDay
46%6%9%21%13%1
1717
16th to endDay
58%412%17%5%
1755
December1st to 15thDay
62%7%11%13%3
1596
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
46%412%17%16%3
1620
May1st to 15thNight
49%6%10%20%10%2
1620
16th to endNight
38%7%13%23%14%3
1642
June1st to 15thNight
35%6%12%28%15%1
1440
16th to endNight
32%8%16%23%17%
1440
July1st to 15thNight
29%6%12%27%20%2
1360
16th to endNight
26%9%14%24%22%2
1472
August1st to 15thNight
30%7%14%29%16%2
1609
16th to endNight
34%411%27%18%3
1782
September1st to 15thNight
33%5%8%29%20%2
1905
16th to endNight
34%5%12%28%18%
1980
October1st to 15thNight
41%5%10%22%17%1
2043
16th to endNight
50%5%11%22%9%
2436
November1st to 15thNight
46%5%12%20%12%2
2471
16th to endNight
56%413%18%6%
2535
December1st to 15thNight
63%6%11%13%5%
2445
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
20%8%31%22%11%7%
270
May1st to 15thDay
23%7%29%21%12%5%
288
16th to endDay
16%10%25%22%16%8%
370
June1st to 15thDay
11%5%30%30%15%5%
495
16th to endDay
11%7%31%28%15%5%
495
July1st to 15thDay
9%225%29%21%11%
475
16th to endDay
9%323%27%23%12%
455
August1st to 15thDay
10%18%26%23%20%
313
16th to endDay
15%218%22%25%16%
332
September1st to 15thDay
12%220%19%28%16%
315
16th to endDay
14%5%14%21%30%13%
314
October1st to 15thDay
16%6%23%30%16%5%
315
16th to endDay
23%12%27%28%6%
202
November1st to 15thDay
13%14%27%30%11%3
135
16th to endDay
20%18%42%11%5%
135
December1st to 15thDay
20%26%33%12%9%
100
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
540
May1st to 15thNight
24%5%27%32%8%1
540
16th to endNight
15%326%34%18%1
563
June1st to 15thNight
11%225%45%15%
540
16th to endNight
7%223%42%20%2
540
July1st to 15thNight
7%117%44%25%3
510
16th to endNight
6%116%44%29%2
564
August1st to 15thNight
7%13%47%24%5%
539
16th to endNight
12%112%34%32%5%
573
September1st to 15thNight
13%316%34%26%5%
645
16th to endNight
14%417%29%30%5%
717
October1st to 15thNight
17%6%24%31%18%2
720
16th to endNight
23%13%32%23%7%
768
November1st to 15thNight
19%9%30%28%10%1
760
16th to endNight
24%13%31%23%6%
780
December1st to 15thNight
24%11%36%22%3
790
16th to endNight
29%11%36%18%3
960
Page generated at 2017-12-05 10:19:03. Version ac04

Copyright 2017 A. Danko


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