UF Campus Teaching Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UF Campus Teaching Observatory clear sky chart from 2005-11-06 to 2024-03-23.

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%
24603
21%
80052
15%
24500
59%
24500
27%
49303

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 10thNight
34%
753
23%
3999
13%
737
48%
737
16%
2235
January11th to 20thNight
44%
755
23%
4023
20%
740
56%
740
16%
2533
January21st to endNight
28%
832
15%
4315
11%
814
42%
814
14%
2520
February1st to 10thNight
40%
760
24%
2280
15%
760
50%
760
30%
1394
February11th to 20thNight
36%
740
23%
2218
12%
739
48%
739
28%
1354
February21st to endNight
38%
628
24%
1848
13%
628
49%
628
30%
1123
March1st to 10thNight
40%
760
29%
2090
16%
760
50%
760
37%
1214
March11th to 20thNight
41%
760
26%
2090
14%
760
51%
760
33%
1266
March21st to endNight
42%
801
27%
2201
14%
801
52%
801
39%
1260
April1st to 10thNight
45%
720
25%
1980
15%
720
52%
720
35%
1176
April11th to 20thNight
41%
711
22%
1948
12%
711
49%
711
34%
1170
April21st to endNight
52%
648
31%
1728
18%
648
60%
648
44%
983
May1st to 10thNight
63%
540
29%
1620
20%
540
70%
540
46%
848
May11th to 20thNight
61%
531
20%
1592
13%
531
66%
531
37%
920
May21st to endNight
73%
582
24%
1744
18%
582
75%
582
37%
1016
June1st to 10thNight
63%
540
13%
1620
10%
540
65%
540
27%
1065
June11th to 20thNight
71%
540
12%
1620
9%
540
73%
540
28%
1050
June21st to endNight
72%
540
11%
1620
9%
540
73%
540
27%
1081
July1st to 10thNight
73%
525
8%
1575
7%
525
73%
525
23%
1103
July11th to 20thNight
73%
522
9%
1566
9%
522
73%
522
23%
1108
July21st to endNight
78%
591
11%
1672
11%
558
79%
558
27%
1110
August1st to 10thNight
74%
537
8%
1600
7%
534
74%
534
25%
1087
August11th to 20thNight
75%
534
7%
1694
7%
534
75%
534
23%
1155
August21st to endNight
62%
749
11%
2135
11%
749
63%
749
19%
1552
September1st to 10thNight
65%
720
11%
1980
10%
720
65%
720
21%
1436
September11th to 20thNight
56%
720
9%
1980
9%
720
57%
720
19%
1462
September21st to endNight
60%
720
22%
1980
19%
720
63%
720
29%
1325
October1st to 10thNight
53%
720
24%
1980
19%
720
58%
720
30%
1267
October11th to 20thNight
61%
720
32%
2144
29%
720
69%
720
41%
1173
October21st to endNight
55%
792
29%
2376
24%
792
63%
792
32%
1411
November1st to 10thNight
49%
740
28%
2221
21%
740
61%
740
37%
1238
November11th to 20thNight
46%
760
28%
2303
20%
760
58%
760
32%
1366
November21st to endNight
43%
760
25%
2470
19%
760
54%
760
29%
1466
December1st to 10thNight
46%
760
27%
2470
21%
760
57%
760
30%
1431
December11th to 20thNight
44%
760
24%
2934
18%
758
53%
758
23%
1731
December21st to endNight
42%
832
16%
4436
18%
817
53%
817
15%
2674

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
10%6%36%6%46%6%6%8%39%
79134
Night
10%6%35%5%35%5%6%9%44%
80752
TransparencyDay
40%7%13%18%15%7%
78857
Night
37%7%15%19%16%7%
80548
SeeingDay
12%6%21%25%22%14%
14478
Night
11%6%21%32%24%6%
24628

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 10thDay
14%7%26%5%2445%6%46%
2836
11th to 20thDay
19%9%47%5%23446%38%
2840
21st to endDay
11%6%25%5%3446%8%45%
3256
February1st to 10thDay
16%5%35%5%345%5%7%44%
1900
11th to 20thDay
12%5%3443445%7%51%
1848
21st to endDay
11%6%36%5%235%5%6%48%
1603
March1st to 10thDay
8%425%33345%9%53%
2090
11th to 20thDay
10%5%244345%6%8%50%
2090
21st to endDay
9%5%35%5%3445%7%51%
2200
April1st to 10thDay
8%3245%36%46%9%50%
1980
11th to 20thDay
10%5%37%6%45%5%5%7%43%
1960
21st to endDay
5%324435%6%5%8%54%
2243
May1st to 10thDay
5%3246%345%6%9%54%
2340
11th to 20thDay
8%435%5%47%6%8%10%39%
2301
21st to endDay
8%5%36%7%47%6%7%8%39%
2531
June1st to 10thDay
10%7%36%7%5%8%8%7%11%27%
2340
11th to 20thDay
6%437%9%5%10%9%9%10%28%
2340
21st to endDay
8%6%47%9%5%8%7%8%10%28%
2340
July1st to 10thDay
9%6%47%9%5%9%9%9%11%24%
2340
11th to 20thDay
7%6%48%9%6%8%9%9%10%23%
2340
21st to endDay
8%6%37%9%6%8%8%8%10%26%
2547
August1st to 10thDay
9%5%27%7%5%9%9%10%12%24%
2327
11th to 20thDay
9%6%48%9%7%8%9%9%10%19%
2201
21st to endDay
11%6%38%10%5%6%8%9%10%23%
2201
September1st to 10thDay
10%6%37%8%5%9%10%9%10%23%
1980
11th to 20thDay
12%7%39%7%5%8%8%8%9%25%
1980
21st to endDay
10%6%38%8%46%6%7%7%35%
1980
October1st to 10thDay
10%6%27%7%45%6%6%7%39%
1980
11th to 20thDay
6%434435%5%5%7%53%
1814
21st to endDay
8%425%5%35%5%7%7%50%
1980
November1st to 10thDay
9%5%25%6%35%5%5%8%49%
1857
11th to 20thDay
9%7%36%5%345%5%7%46%
1872
21st to endDay
11%5%36%5%35%447%47%
1710
December1st to 10thDay
9%5%35%5%35%46%9%47%
1710
11th to 20thDay
13%7%35%5%345%5%7%44%
2153
21st to endDay
16%9%36%5%34346%42%
3124
January1st to 10thNight
14%8%35%5%24448%43%
4109
11th to 20thNight
14%8%37%6%35%45%7%37%
4120
21st to endNight
14%7%26%6%45%46%7%41%
4395
February1st to 10thNight
12%6%25%5%34446%47%
2280
11th to 20thNight
11%7%36%43435%6%48%
2218
21st to endNight
10%6%35%44345%6%49%
1848
March1st to 10thNight
9%6%2442335%8%53%
2090
11th to 20thNight
9%5%345%345%6%9%48%
2090
21st to endNight
7%4244245%5%7%55%
2201
April1st to 10thNight
9%5%24425%5%6%8%52%
1980
11th to 20thNight
9%435%44446%9%49%
1948
21st to endNight
6%3234245%7%8%56%
1728
May1st to 10thNight
431432445%9%61%
1620
11th to 20thNight
44345%35%5%7%10%50%
1592
21st to endNight
5%324446%6%6%10%49%
1744
June1st to 10thNight
10%6%36%6%46%6%7%11%35%
1620
11th to 20thNight
5%435%6%37%6%10%14%34%
1620
21st to endNight
7%5%25%6%36%7%8%15%36%
1620
July1st to 10thNight
5%436%6%47%7%10%15%32%
1620
11th to 20thNight
45%37%7%47%8%8%11%34%
1620
21st to endNight
4425%6%5%8%8%9%12%36%
1771
August1st to 10thNight
6%5%25%7%36%8%10%10%36%
1611
11th to 20thNight
5%5%25%7%46%8%9%15%33%
1694
21st to endNight
9%7%39%8%45%7%7%9%31%
2135
September1st to 10thNight
7%6%38%7%37%8%11%12%29%
1980
11th to 20thNight
12%7%47%7%5%7%8%6%9%29%
1980
21st to endNight
9%7%36%6%45%47%10%38%
1980
October1st to 10thNight
10%5%36%6%45%46%8%44%
1980
11th to 20thNight
6%425%433449%56%
2144
21st to endNight
8%6%25%5%34446%51%
2376
November1st to 10thNight
9%425%4235%5%7%53%
2221
11th to 20thNight
10%6%345%345%5%6%50%
2303
21st to endNight
11%6%25%5%3445%7%47%
2470
December1st to 10thNight
11%6%245%345%5%9%47%
2470
11th to 20thNight
14%6%26%5%33346%48%
3042
21st to endNight
15%8%35%6%35%45%7%39%
4532

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 10thDay
39%36%19%19%12%
2837
11th to 20thDay
49%35%13%17%13%
2840
21st to endDay
36%5%9%20%17%13%
3256
February1st to 10thDay
40%5%9%14%20%12%
1900
11th to 20thDay
33%5%9%16%24%13%
1858
21st to endDay
36%5%10%16%21%12%
1603
March1st to 10thDay
28%5%9%23%24%11%
2090
11th to 20thDay
32%413%23%17%12%
2090
21st to endDay
33%410%24%20%10%
2200
April1st to 10thDay
32%5%12%20%19%12%
1980
11th to 20thDay
41%5%7%18%21%7%
1960
21st to endDay
27%5%10%26%23%10%
2243
May1st to 10thDay
27%5%10%24%25%9%
2340
11th to 20thDay
37%7%16%23%13%4
2305
21st to endDay
39%7%12%21%18%3
2531
June1st to 10thDay
48%9%18%18%7%
2340
11th to 20thDay
46%11%20%19%4
2340
21st to endDay
48%10%22%14%5%1
2340
July1st to 10thDay
49%12%23%14%1
2275
11th to 20thDay
50%12%26%10%2
2271
21st to endDay
47%12%25%14%2
2405
August1st to 10thDay
45%13%25%14%2
2314
11th to 20thDay
54%13%23%9%1
2201
21st to endDay
51%11%20%15%2
2201
September1st to 10thDay
50%13%20%11%5%1
1980
11th to 20thDay
52%10%18%13%6%1
1980
21st to endDay
45%7%13%17%14%4
1980
October1st to 10thDay
43%6%9%16%14%11%
1980
11th to 20thDay
30%6%7%23%26%8%
1814
21st to endDay
32%5%8%17%24%14%
1980
November1st to 10thDay
33%5%9%21%18%14%
1857
11th to 20thDay
38%49%18%22%10%
1872
21st to endDay
37%48%20%25%6%
1710
December1st to 10thDay
35%313%27%16%6%
1710
11th to 20thDay
39%5%8%19%18%11%
2150
21st to endDay
44%45%20%19%8%
3124
January1st to 10thNight
41%37%17%20%13%
4109
11th to 20thNight
46%46%17%19%8%
4120
21st to endNight
42%5%11%13%18%10%
4395
February1st to 10thNight
38%49%17%20%12%
2280
11th to 20thNight
37%47%20%20%12%
2219
21st to endNight
36%5%10%18%21%11%
1848
March1st to 10thNight
30%411%22%22%11%
2090
11th to 20thNight
32%6%15%20%17%10%
2090
21st to endNight
29%412%26%19%10%
2201
April1st to 10thNight
30%6%15%20%19%10%
1980
11th to 20thNight
33%5%10%25%21%7%
1948
21st to endNight
25%6%13%28%20%8%
1728
May1st to 10thNight
22%6%12%28%25%8%
1620
11th to 20thNight
29%7%20%26%15%4
1593
21st to endNight
28%8%17%24%21%2
1745
June1st to 10thNight
41%7%24%22%6%
1620
11th to 20thNight
35%11%28%23%3
1620
21st to endNight
35%14%27%18%6%1
1620
July1st to 10thNight
38%16%30%14%2
1575
11th to 20thNight
41%14%29%14%3
1566
21st to endNight
33%16%31%18%3
1672
August1st to 10thNight
36%15%34%13%2
1600
11th to 20thNight
37%15%33%14%2
1694
21st to endNight
47%12%22%17%3
2135
September1st to 10thNight
41%16%23%14%5%1
1980
11th to 20thNight
49%10%18%16%6%1
1980
21st to endNight
40%7%18%17%13%3
1980
October1st to 10thNight
37%8%12%19%14%10%
1980
11th to 20thNight
26%5%10%25%27%7%
2144
21st to endNight
33%6%7%17%24%12%
2376
November1st to 10thNight
29%411%22%20%13%
2221
11th to 20thNight
34%5%9%20%20%12%
2303
21st to endNight
38%410%19%22%9%
2470
December1st to 10thNight
35%413%27%15%7%
2470
11th to 20thNight
39%39%17%22%10%
3044
21st to endNight
44%5%10%19%17%5%
4532

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 10thDay
12%15%51%16%6%
270
11th to 20thDay
13%10%46%20%9%2
270
21st to endDay
20%21%42%15%2
297
February1st to 10thDay
16%15%37%24%7%1
270
11th to 20thDay
15%16%37%24%7%1
270
21st to endDay
13%15%35%28%10%
258
March1st to 10thDay
11%16%32%29%10%2
460
11th to 20thDay
13%11%35%23%15%2
460
21st to endDay
13%11%31%29%14%2
470
April1st to 10thDay
15%13%26%26%18%2
420
11th to 20thDay
14%9%30%29%14%4
412
21st to endDay
7%6%29%30%20%8%
420
May1st to 10thDay
7%6%26%30%21%10%
423
11th to 20thDay
9%418%32%22%16%
447
21st to endDay
10%210%26%33%19%
485
June1st to 10thDay
14%212%26%27%19%
450
11th to 20thDay
12%19%24%32%22%
450
21st to endDay
6%7%24%34%29%
450
July1st to 10thDay
9%2416%30%40%
445
11th to 20thDay
7%215%35%41%
444
21st to endDay
9%15%19%36%30%
488
August1st to 10thDay
11%1420%31%33%
446
11th to 20thDay
9%1316%31%40%
439
21st to endDay
12%15%21%34%27%
495
September1st to 10thDay
12%27%18%33%28%
450
11th to 20thDay
15%26%29%27%20%
450
21st to endDay
12%28%27%34%18%
450
October1st to 10thDay
14%423%32%20%7%
450
11th to 20thDay
6%420%35%28%7%
450
21st to endDay
10%424%37%21%4
495
November1st to 10thDay
12%5%28%30%22%4
455
11th to 20thDay
18%6%30%30%13%3
432
21st to endDay
12%7%40%32%8%1
270
December1st to 10thDay
11%14%35%22%14%4
270
11th to 20thDay
17%11%35%27%9%1
270
21st to endDay
14%7%37%32%9%1
297
January1st to 10thNight
16%12%32%29%10%1
760
11th to 20thNight
13%11%26%38%13%1
760
21st to endNight
19%12%35%28%6%
836
February1st to 10thNight
17%8%31%33%10%1
760
11th to 20thNight
14%11%31%34%9%1
743
21st to endNight
11%12%33%39%5%
628
March1st to 10thNight
13%10%35%32%10%
760
11th to 20thNight
12%12%30%32%14%
760
21st to endNight
9%9%35%35%11%
801
April1st to 10thNight
10%9%31%37%12%1
720
11th to 20thNight
11%8%33%34%13%1
711
21st to endNight
8%5%28%40%17%1
648
May1st to 10thNight
5%324%46%20%2
540
11th to 20thNight
7%320%38%29%4
531
21st to endNight
7%111%39%35%6%
584
June1st to 10thNight
14%210%32%34%8%
540
11th to 20thNight
6%27%29%38%19%
540
21st to endNight
9%16%21%44%20%
540
July1st to 10thNight
7%1418%47%24%
525
11th to 20thNight
42215%49%28%
522
21st to endNight
5%220%52%20%
591
August1st to 10thNight
8%417%49%22%
537
11th to 20thNight
7%2214%53%22%
534
21st to endNight
12%35%25%39%16%
749
September1st to 10thNight
11%16%24%43%15%
720
11th to 20thNight
15%29%33%33%9%
720
21st to endNight
13%210%32%35%8%
720
October1st to 10thNight
12%220%35%27%4
720
11th to 20thNight
7%321%41%27%2
720
21st to endNight
10%421%41%22%2
792
November1st to 10thNight
11%5%29%31%21%2
740
11th to 20thNight
12%429%37%16%1
760
21st to endNight
15%5%30%36%14%1
760
December1st to 10thNight
12%8%26%34%18%1
760
11th to 20thNight
14%8%27%36%14%1
760
21st to endNight
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