Appleton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Appleton clear sky chart from 2005-11-05 to 2017-09-10.

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
35%
16057
17%
46771
9%
16014
42%
16014
24%
31202

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
22%
900
13%
2506
5%
895
29%
895
17%
1845
January16th to endNight
18%
960
13%
2688
2%
960
27%
960
17%
2020
February1st to 15thNight
23%
848
15%
2268
3%
847
31%
847
19%
1597
February16th to endNight
29%
631
17%
1893
7%
631
38%
631
17%
1350
March1st to 15thNight
31%
720
15%
2160
9%
720
37%
720
22%
1427
March16th to endNight
34%
613
18%
2010
14%
613
42%
613
21%
1336
April1st to 15thNight
27%
539
16%
1797
10%
539
36%
539
20%
1216
April16th to endNight
35%
540
19%
1710
12%
540
43%
540
23%
1133
May1st to 15thNight
30%
540
16%
1518
8%
540
38%
540
22%
1062
May16th to endNight
43%
562
16%
1498
8%
561
49%
561
32%
964
June1st to 15thNight
47%
540
14%
1440
6%
540
52%
540
32%
923
June16th to endNight
50%
540
14%
1440
6%
540
54%
540
35%
896
July1st to 15thNight
61%
510
17%
1360
10%
510
64%
510
45%
781
July16th to endNight
59%
564
20%
1417
12%
531
63%
531
44%
830
August1st to 15thNight
67%
539
23%
1476
18%
536
70%
536
41%
863
August16th to endNight
56%
573
21%
1910
19%
573
62%
573
32%
1098
September1st to 15thNight
53%
525
25%
1750
22%
525
61%
525
34%
972
September16th to endNight
50%
648
22%
1806
14%
648
57%
648
34%
1085
October1st to 15thNight
40%
660
23%
1925
15%
660
47%
660
29%
1192
October16th to endNight
30%
704
15%
2254
8%
704
39%
704
19%
1525
November1st to 15thNight
30%
700
21%
2276
13%
700
40%
700
24%
1417
November16th to endNight
26%
841
15%
2461
7%
841
35%
841
18%
1751
December1st to 15thNight
17%
900
11%
2520
2%
900
25%
900
16%
1846
December16th to endNight
17%
960
13%
2688
2%
960
26%
960
14%
2073

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%7%36%5%35%5%5%7%36%
47867
Night
13%8%35%5%34446%39%
46939
Cloud CoverDay
13%7%36%5%35%45%7%36%
47876
Night
13%8%36%5%2445%6%39%
46944
TransparencyDay
45%413%24%10%1
47553
Night
44%412%24%12%1
46771
SeeingDay
16%7%28%27%14%4
6049
Night
17%8%31%29%11%1
16060

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
12%12%5%9%7%35%45%5%28%
1432
16th to endDay
12%14%5%11%8%345%5%5%23%
1536
February1st to 15thDay
12%10%5%7%6%35%5%5%5%31%
1593
16th to endDay
13%10%48%425%45%6%33%
1580
March1st to 15thDay
14%9%46%43445%8%34%
1790
16th to endDay
16%8%36%5%24447%34%
2223
April1st to 15thDay
16%12%46%435%5%45%30%
2151
16th to endDay
19%8%36%5%25%346%34%
2250
May1st to 15thDay
18%6%27%6%3445%7%33%
2433
16th to endDay
10%5%15%5%35%6%6%9%41%
2617
June1st to 15thDay
13%5%35%5%3445%8%40%
2520
16th to endDay
9%5%25%5%35%46%10%39%
2520
July1st to 15thDay
6%315%445%6%6%10%45%
2520
16th to endDay
9%4235%25%5%6%8%44%
2655
August1st to 15thDay
6%425%5%45%6%7%9%42%
2472
16th to endDay
12%5%25%435%448%44%
2292
September1st to 15thDay
11%5%25%424447%45%
2094
16th to endDay
10%5%36%5%36%45%9%39%
1815
October1st to 15thDay
17%7%25%424335%42%
1702
16th to endDay
16%9%36%6%3435%6%33%
1617
November1st to 15thDay
13%7%25%6%35%5%5%6%36%
1582
16th to endDay
15%10%5%6%6%345%5%7%30%
1497
December1st to 15thDay
15%12%5%7%7%35%45%5%28%
1440
16th to endDay
19%13%7%9%8%44445%19%
1536
January1st to 15thNight
14%12%5%7%5%3434432%
2506
16th to endNight
12%13%6%9%6%45%45%428%
2688
February1st to 15thNight
11%11%48%5%2443437%
2266
16th to endNight
14%11%47%6%4443434%
1893
March1st to 15thNight
13%8%35%43435%5%40%
2147
16th to endNight
16%8%35%5%3435%6%36%
2010
April1st to 15thNight
21%7%35%5%3335%5%35%
1797
16th to endNight
18%7%35%5%23346%39%
1710
May1st to 15thNight
19%6%35%43445%6%36%
1518
16th to endNight
11%4245%25%5%7%9%42%
1496
June1st to 15thNight
10%5%25%5%336%5%7%44%
1440
16th to endNight
8%5%23425%5%6%10%44%
1440
July1st to 15thNight
6%3134335%7%7%54%
1440
16th to endNight
5%424325%45%9%52%
1513
August1st to 15thNight
7%3144245%6%9%50%
1485
16th to endNight
9%5%2442445%6%50%
1910
September1st to 15thNight
10%5%2332335%5%54%
1750
16th to endNight
11%414433347%48%
1806
October1st to 15thNight
15%5%14423446%46%
1925
16th to endNight
16%8%25%6%25%45%7%35%
2254
November1st to 15thNight
14%7%25%5%24436%43%
2276
16th to endNight
16%10%45%6%345%46%32%
2461
December1st to 15thNight
16%13%47%5%25%446%30%
2520
16th to endNight
19%14%5%7%6%34335%26%
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
13%12%5%9%6%45%36%5%28%
1432
16th to endDay
12%14%5%11%7%345%5%6%23%
1536
February1st to 15thDay
13%10%5%7%6%35%5%5%5%31%
1593
16th to endDay
13%10%48%435%45%6%33%
1580
March1st to 15thDay
14%9%46%5%345%5%7%34%
1800
16th to endDay
16%8%36%5%24447%34%
2222
April1st to 15thDay
16%11%46%435%45%5%31%
2151
16th to endDay
19%8%36%5%25%346%34%
2250
May1st to 15thDay
18%6%26%6%3445%6%33%
2433
16th to endDay
10%5%15%5%35%6%6%8%41%
2617
June1st to 15thDay
13%6%35%5%3446%7%39%
2520
16th to endDay
9%5%25%5%36%46%10%39%
2520
July1st to 15thDay
6%315%435%6%6%10%45%
2520
16th to endDay
9%5%235%35%5%6%9%44%
2655
August1st to 15thDay
7%425%5%35%5%7%9%42%
2472
16th to endDay
12%5%2443445%8%44%
2292
September1st to 15thDay
11%5%25%5%2445%7%45%
2094
16th to endDay
10%5%36%5%36%45%9%39%
1815
October1st to 15thDay
17%7%25%424335%42%
1702
16th to endDay
16%9%36%6%4435%6%33%
1617
November1st to 15thDay
13%8%35%6%345%5%6%37%
1582
16th to endDay
15%10%47%6%25%45%7%30%
1497
December1st to 15thDay
15%12%5%7%7%35%445%28%
1440
16th to endDay
19%13%7%9%8%34445%19%
1536
January1st to 15thNight
14%12%5%7%5%3434432%
2506
16th to endNight
12%13%6%9%6%35%5%5%428%
2688
February1st to 15thNight
11%11%48%5%24435%37%
2259
16th to endNight
14%11%47%6%4444434%
1893
March1st to 15thNight
13%8%35%5%3435%5%40%
2160
16th to endNight
16%7%35%5%3435%6%36%
2010
April1st to 15thNight
21%7%35%43435%5%35%
1797
16th to endNight
18%7%35%423446%39%
1710
May1st to 15thNight
19%6%25%43345%6%36%
1517
16th to endNight
11%4245%245%7%9%42%
1496
June1st to 15thNight
10%5%25%5%346%5%7%44%
1440
16th to endNight
8%5%23425%5%7%10%44%
1440
July1st to 15thNight
6%3134245%6%7%54%
1440
16th to endNight
4424325%45%9%52%
1513
August1st to 15thNight
7%3143245%6%8%50%
1485
16th to endNight
9%5%2442345%6%50%
1910
September1st to 15thNight
10%5%24323345%54%
1750
16th to endNight
11%415%5%33347%48%
1806
October1st to 15thNight
15%5%14324446%46%
1925
16th to endNight
16%8%25%6%2445%7%35%
2254
November1st to 15thNight
14%7%25%5%24346%43%
2276
16th to endNight
16%10%46%6%245%47%32%
2461
December1st to 15thNight
16%13%5%7%5%24445%30%
2520
16th to endNight
19%14%5%7%6%34335%26%
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
56%412%19%6%
1433
16th to endDay
60%311%16%7%
1536
February1st to 15thDay
52%410%23%8%
1595
16th to endDay
50%412%21%9%1
1580
March1st to 15thDay
48%5%15%20%8%1
1800
16th to endDay
49%416%22%5%1
2223
April1st to 15thDay
53%411%20%9%
2151
16th to endDay
51%410%20%10%2
2250
May1st to 15thDay
49%412%23%8%
2433
16th to endDay
37%6%13%26%13%1
2621
June1st to 15thDay
41%414%27%11%
2520
16th to endDay
38%6%15%24%14%
2520
July1st to 15thDay
32%6%13%30%14%2
2371
16th to endDay
34%6%14%26%15%2
2488
August1st to 15thDay
35%6%15%30%10%1
2457
16th to endDay
37%5%13%27%14%1
2292
September1st to 15thDay
37%412%31%13%
2094
16th to endDay
40%415%29%9%
1815
October1st to 15thDay
44%313%27%11%
1702
16th to endDay
51%414%23%7%
1617
November1st to 15thDay
45%412%23%11%1
1582
16th to endDay
52%417%19%5%
1497
December1st to 15thDay
54%414%20%5%
1440
16th to endDay
67%310%12%5%
1536
January1st to 15thNight
55%310%19%10%
2506
16th to endNight
56%412%18%7%
2688
February1st to 15thNight
49%310%24%9%1
2268
16th to endNight
52%311%21%8%1
1893
March1st to 15thNight
44%414%22%12%1
2160
16th to endNight
47%312%25%9%
2010
April1st to 15thNight
50%37%21%14%2
1797
16th to endNight
46%311%21%14%2
1710
May1st to 15thNight
47%5%12%22%12%
1518
16th to endNight
35%6%14%25%15%1
1498
June1st to 15thNight
36%6%12%29%14%
1440
16th to endNight
32%6%15%26%16%2
1440
July1st to 15thNight
26%414%31%18%4
1360
16th to endNight
26%6%15%31%17%3
1417
August1st to 15thNight
28%5%14%33%15%1
1476
16th to endNight
33%412%28%17%2
1910
September1st to 15thNight
32%310%29%23%
1750
16th to endNight
34%314%35%11%1
1806
October1st to 15thNight
38%411%30%14%1
1925
16th to endNight
47%414%20%11%
2254
November1st to 15thNight
41%313%24%14%2
2276
16th to endNight
51%415%20%6%
2461
December1st to 15thNight
54%314%18%7%
2520
16th to endNight
60%312%16%5%
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
26%8%31%28%4
90
16th to endDay
26%327%32%11%
96
February1st to 15thDay
16%12%41%22%7%
90
16th to endDay
20%11%37%22%7%1
81
March1st to 15thDay
26%10%32%18%12%
90
16th to endDay
32%5%22%28%9%1
234
April1st to 15thDay
26%9%28%24%9%
270
16th to endDay
24%8%28%25%10%3
270
May1st to 15thDay
23%10%32%22%8%3
390
16th to endDay
15%9%33%24%10%5%
517
June1st to 15thDay
15%7%30%29%13%2
495
16th to endDay
11%8%32%29%14%4
495
July1st to 15thDay
9%6%23%30%21%7%
475
16th to endDay
9%5%28%29%18%8%
515
August1st to 15thDay
9%123%32%24%8%
457
16th to endDay
16%5%17%29%20%10%
332
September1st to 15thDay
15%420%30%20%8%
294
16th to endDay
14%425%27%22%5%
254
October1st to 15thDay
16%9%23%27%20%3
142
16th to endDay
16%7%47%21%6%
96
November1st to 15thDay
316%33%32%12%2
90
16th to endDay
27%15%36%11%8%
90
December1st to 15thDay
20%16%50%12%1
90
16th to endDay
30%23%36%8%1
96
January1st to 15thNight
19%12%36%24%7%
900
16th to endNight
19%9%39%24%6%
960
February1st to 15thNight
18%11%34%28%6%
850
16th to endNight
20%11%30%28%8%
631
March1st to 15thNight
18%10%31%28%9%1
720
16th to endNight
18%8%30%31%9%1
613
April1st to 15thNight
24%7%35%25%5%
539
16th to endNight
20%7%33%29%8%
540
May1st to 15thNight
23%7%34%26%8%
540
16th to endNight
12%7%31%35%13%
563
June1st to 15thNight
12%5%27%38%14%
540
16th to endNight
10%329%40%13%1
540
July1st to 15thNight
8%220%46%21%
510
16th to endNight
7%223%40%24%1
564
August1st to 15thNight
9%214%47%25%2
539
16th to endNight
11%221%37%24%2
573
September1st to 15thNight
12%424%33%20%5%
525
16th to endNight
12%7%23%31%22%1
648
October1st to 15thNight
19%8%27%27%16%1
660
16th to endNight
21%12%29%26%9%
704
November1st to 15thNight
18%9%37%26%8%1
700
16th to endNight
20%13%33%24%7%
841
December1st to 15thNight
24%12%38%19%4
900
16th to endNight
26%10%34%22%41
960
Page generated at 2017-09-11 18:35:28. Version ac04

Copyright 2017 A. Danko


Appleton Clear Sky Chart | Charts Home