Aztalan State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aztalan State Park clear sky chart from 2005-11-06 to 2024-01-10.

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
36%
24686
17%
74636
10%
24630
43%
24630
22%
50550

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
24%
950
14%
2647
6%
946
31%
946
18%
1913
January11th to 20thNight
21%
900
11%
2520
3%
900
28%
900
14%
1962
January21st to endNight
21%
990
10%
2722
3%
990
27%
990
15%
2106
February1st to 10thNight
22%
900
12%
2340
3%
900
28%
900
19%
1738
February11th to 20thNight
26%
735
19%
2134
8%
735
34%
735
19%
1483
February21st to endNight
20%
592
17%
1776
5%
592
31%
592
18%
1238
March1st to 10thNight
28%
720
14%
2160
7%
720
34%
720
19%
1498
March11th to 20thNight
35%
658
20%
2098
13%
658
43%
658
24%
1316
March21st to endNight
33%
594
16%
1989
13%
594
38%
594
16%
1412
April1st to 10thNight
26%
540
13%
1800
8%
540
34%
540
17%
1233
April11th to 20thNight
33%
533
20%
1775
15%
533
42%
533
19%
1183
April21st to endNight
33%
540
16%
1713
9%
540
41%
540
22%
1156
May1st to 10thNight
32%
540
15%
1576
9%
540
37%
540
21%
1101
May11th to 20thNight
36%
531
18%
1417
9%
531
43%
531
26%
984
May21st to endNight
47%
584
15%
1552
9%
582
52%
582
30%
1026
June1st to 10thNight
53%
540
17%
1440
10%
540
57%
540
35%
883
June11th to 20thNight
48%
540
18%
1440
10%
540
52%
540
35%
901
June21st to endNight
54%
540
19%
1440
11%
540
57%
540
36%
894
July1st to 10thNight
70%
525
17%
1400
12%
525
71%
525
45%
813
July11th to 20thNight
63%
522
21%
1392
14%
522
67%
522
42%
816
July21st to endNight
67%
591
22%
1487
16%
558
69%
558
40%
885
August1st to 10thNight
68%
537
21%
1423
17%
534
70%
534
37%
885
August11th to 20thNight
67%
534
21%
1744
22%
534
72%
534
35%
980
August21st to endNight
62%
594
22%
1980
23%
594
67%
594
34%
1110
September1st to 10thNight
59%
540
24%
1800
23%
540
65%
540
34%
997
September11th to 20thNight
57%
600
29%
1860
27%
600
62%
600
34%
1081
September21st to endNight
46%
720
23%
1980
14%
720
53%
720
33%
1228
October1st to 10thNight
45%
720
23%
2086
16%
720
51%
720
30%
1291
October11th to 20thNight
32%
720
19%
2160
9%
720
42%
720
24%
1424
October21st to endNight
29%
792
16%
2569
10%
792
37%
792
19%
1745
November1st to 10thNight
33%
740
25%
2406
16%
740
46%
740
25%
1469
November11th to 20thNight
24%
760
17%
2470
9%
760
33%
760
17%
1713
November21st to endNight
26%
926
16%
2636
8%
926
34%
926
20%
1839
December1st to 10thNight
20%
950
12%
2660
3%
950
27%
950
16%
1980
December11th to 20thNight
20%
950
12%
3211
4%
948
27%
948
12%
2439
December21st to endNight
16%
1038
7%
4833
3%
1026
23%
1026
7%
3828

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%8%47%6%35%5%5%7%37%
74760
Night
14%9%46%5%3445%6%39%
74937
TransparencyDay
46%6%13%22%12%1
74461
Night
45%6%12%22%13%2
74757
SeeingDay
16%10%29%26%15%5%
14707
Night
18%8%31%31%12%1
24696

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
12%11%5%8%8%445%6%7%31%
1509
11th to 20thDay
13%16%6%11%7%335%5%7%23%
1440
21st to endDay
14%15%7%11%7%3445%7%23%
1631
February1st to 10thDay
13%13%6%8%6%45%5%45%30%
1620
11th to 20thDay
14%12%46%5%46%445%35%
1712
21st to endDay
13%14%5%9%7%34446%30%
1480
March1st to 10thDay
14%9%48%5%35%5%5%6%34%
1800
11th to 20thDay
14%8%46%6%34348%40%
1876
21st to endDay
19%10%47%7%45%447%30%
2366
April1st to 10thDay
18%12%5%7%5%35%45%6%30%
2160
11th to 20thDay
18%9%46%5%346%5%7%33%
2134
21st to endDay
20%8%47%6%3445%7%33%
2245
May1st to 10thDay
16%8%37%6%45%5%6%9%30%
2382
11th to 20thDay
19%7%36%6%345%5%8%35%
2479
21st to endDay
14%6%36%6%35%5%6%7%38%
2725
June1st to 10thDay
10%425%6%35%5%6%8%44%
2520
11th to 20thDay
13%5%35%5%35%5%6%8%43%
2520
21st to endDay
12%5%35%5%35%5%6%10%41%
2520
July1st to 10thDay
8%5%25%5%445%6%10%48%
2520
11th to 20thDay
7%5%25%5%45%6%7%10%45%
2520
21st to endDay
7%4345%35%5%7%10%47%
2743
August1st to 10thDay
7%435%5%46%5%7%9%44%
2507
11th to 20thDay
10%5%36%5%35%5%6%9%43%
2154
21st to endDay
10%5%25%5%35%5%5%8%46%
2376
September1st to 10thDay
14%5%25%5%35%5%6%8%43%
2160
11th to 20thDay
13%5%24435%35%7%50%
2080
21st to endDay
13%6%36%5%345%5%8%43%
1980
October1st to 10thDay
15%6%26%43445%7%44%
1872
11th to 20thDay
20%9%37%6%3346%8%32%
1800
21st to endDay
18%10%37%5%24446%37%
1787
November1st to 10thDay
12%8%36%435%446%46%
1672
11th to 20thDay
15%10%49%7%45%45%6%32%
1710
21st to endDay
17%11%47%5%33345%37%
1539
December1st to 10thDay
14%13%49%8%44446%31%
1520
11th to 20thDay
14%13%5%8%6%35%5%5%6%28%
1918
21st to endDay
19%21%9%12%6%3443315%
2783
January1st to 10thNight
12%13%6%8%6%34445%35%
2647
11th to 20thNight
14%14%6%10%7%35%5%46%27%
2520
21st to endNight
14%12%8%10%7%45%45%7%26%
2722
February1st to 10thNight
12%14%6%8%6%3445%6%32%
2340
11th to 20thNight
12%11%47%6%34445%39%
2133
21st to endNight
18%11%46%5%3445%6%35%
1776
March1st to 10thNight
17%9%45%6%3445%6%36%
2160
11th to 20thNight
14%7%335%25%5%6%9%41%
2098
21st to endNight
19%10%47%5%45%445%33%
1989
April1st to 10thNight
17%11%36%6%345%5%6%35%
1800
11th to 20thNight
21%9%35%434446%37%
1775
21st to endNight
19%8%35%5%3445%6%38%
1713
May1st to 10thNight
16%7%37%436%5%6%7%34%
1576
11th to 20thNight
17%6%36%5%36%46%6%38%
1416
21st to endNight
12%6%36%5%3446%10%41%
1551
June1st to 10thNight
10%3245%35%5%7%9%48%
1440
11th to 20thNight
13%415%5%245%5%8%47%
1440
21st to endNight
10%426%42345%8%50%
1440
July1st to 10thNight
7%3134245%7%11%53%
1440
11th to 20thNight
7%325%42445%9%55%
1440
21st to endNight
6%315%435%5%7%8%52%
1575
August1st to 10thNight
5%5%245%45%6%7%10%48%
1432
11th to 20thNight
9%4244335%5%8%53%
1744
21st to endNight
9%5%24435%5%5%8%51%
1980
September1st to 10thNight
9%425%42445%7%53%
1800
11th to 20thNight
12%5%1443445%6%52%
1860
21st to endNight
11%6%35%5%2345%7%49%
1980
October1st to 10thNight
11%6%35%5%33446%49%
2086
11th to 20thNight
17%8%26%5%35%445%42%
2160
21st to endNight
20%9%36%43445%7%36%
2569
November1st to 10thNight
12%7%35%5%2445%6%47%
2406
11th to 20thNight
14%10%47%6%35%5%46%35%
2470
21st to endNight
17%9%47%5%3445%5%38%
2636
December1st to 10thNight
16%13%48%6%45%445%31%
2660
11th to 20thNight
16%14%5%9%6%35%445%29%
3279
21st to endNight
22%17%6%9%6%34445%20%
4884

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
52%6%15%18%9%
1510
11th to 20thDay
61%6%11%14%8%
1440
21st to endDay
62%5%12%13%7%
1631
February1st to 10thDay
56%412%18%8%1
1620
11th to 20thDay
50%5%11%22%10%2
1722
21st to endDay
56%5%9%17%10%2
1480
March1st to 10thDay
49%7%13%21%8%1
1800
11th to 20thDay
45%413%23%14%1
1876
21st to endDay
55%7%11%19%7%1
2366
April1st to 10thDay
54%6%11%19%10%
2160
11th to 20thDay
49%7%11%20%12%2
2134
21st to endDay
50%7%12%19%11%1
2245
May1st to 10thDay
49%7%13%22%8%1
2382
11th to 20thDay
47%7%12%22%12%1
2483
21st to endDay
44%7%12%21%13%2
2725
June1st to 10thDay
36%7%14%26%16%1
2520
11th to 20thDay
37%7%13%23%18%1
2520
21st to endDay
38%8%15%23%15%2
2520
July1st to 10thDay
31%8%15%31%14%2
2451
11th to 20thDay
33%9%16%24%17%2
2445
21st to endDay
30%8%17%27%16%3
2591
August1st to 10thDay
35%8%15%29%12%2
2492
11th to 20thDay
37%8%15%26%13%1
2154
21st to endDay
35%7%12%25%18%2
2376
September1st to 10thDay
37%7%12%24%17%1
2160
11th to 20thDay
34%5%13%31%16%2
2080
21st to endDay
40%5%12%30%13%1
1980
October1st to 10thDay
41%5%9%29%15%1
1872
11th to 20thDay
50%6%12%22%10%1
1800
21st to endDay
49%5%11%23%12%1
1787
November1st to 10thDay
40%6%14%25%14%2
1672
11th to 20thDay
52%6%13%20%9%1
1710
21st to endDay
51%415%23%6%
1539
December1st to 10thDay
56%5%14%17%7%1
1520
11th to 20thDay
55%6%14%16%6%2
1915
21st to endDay
75%5%7%8%5%
2783
January1st to 10thNight
52%5%11%20%11%1
2647
11th to 20thNight
60%6%12%13%8%
2520
21st to endNight
59%5%12%14%9%1
2722
February1st to 10thNight
53%5%10%19%11%2
2340
11th to 20thNight
48%6%11%20%14%1
2134
21st to endNight
51%412%19%11%3
1776
March1st to 10thNight
49%6%13%20%10%2
2160
11th to 20thNight
39%6%14%23%16%2
2098
21st to endNight
53%5%9%20%10%2
1989
April1st to 10thNight
49%6%10%19%15%1
1800
11th to 20thNight
49%47%20%17%3
1775
21st to endNight
45%6%12%20%14%1
1713
May1st to 10thNight
47%7%12%21%12%1
1576
11th to 20thNight
44%7%12%23%12%2
1417
21st to endNight
38%8%14%23%14%3
1552
June1st to 10thNight
31%8%14%27%19%1
1440
11th to 20thNight
33%7%11%24%22%2
1440
21st to endNight
33%6%15%24%19%2
1440
July1st to 10thNight
25%7%17%30%18%3
1400
11th to 20thNight
28%6%13%30%21%3
1392
21st to endNight
26%9%14%30%16%5%
1487
August1st to 10thNight
29%10%16%27%16%3
1423
11th to 20thNight
30%6%15%30%18%1
1744
21st to endNight
31%6%13%27%20%3
1980
September1st to 10thNight
29%7%13%26%23%2
1800
11th to 20thNight
32%6%11%31%18%2
1860
21st to endNight
36%5%11%30%17%1
1980
October1st to 10thNight
36%6%8%30%18%1
2086
11th to 20thNight
44%5%12%22%17%1
2160
21st to endNight
48%5%12%23%11%1
2569
November1st to 10thNight
39%5%10%27%17%2
2406
11th to 20thNight
50%6%13%20%11%1
2470
21st to endNight
49%5%15%22%9%1
2636
December1st to 10thNight
55%6%12%19%8%1
2660
11th to 20thNight
58%5%11%17%8%1
3281
21st to endNight
67%5%9%14%4
4884

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
20%11%34%25%7%2
267
11th to 20thDay
19%13%36%24%7%1
240
21st to endDay
21%13%34%26%5%1
264
February1st to 10thDay
15%18%43%18%5%
240
11th to 20thDay
20%23%34%17%6%
240
21st to endDay
23%19%41%16%11
198
March1st to 10thDay
17%19%44%15%5%
240
11th to 20thDay
21%20%30%16%12%1
240
21st to endDay
27%12%30%23%7%2
452
April1st to 10thDay
21%14%35%25%5%
420
11th to 20thDay
25%15%27%21%9%3
412
21st to endDay
25%11%25%24%13%2
420
May1st to 10thDay
21%12%30%26%9%2
465
11th to 20thDay
22%9%29%26%11%2
625
21st to endDay
17%9%28%23%16%7%
679
June1st to 10thDay
10%6%28%32%19%5%
630
11th to 20thDay
14%7%26%32%14%6%
630
21st to endDay
13%7%29%29%17%5%
630
July1st to 10thDay
8%317%31%27%14%
621
11th to 20thDay
8%6%26%31%22%8%
618
21st to endDay
7%326%35%21%8%
684
August1st to 10thDay
8%219%33%25%12%
626
11th to 20thDay
12%6%14%25%26%16%
465
21st to endDay
11%5%19%31%24%10%
495
September1st to 10thDay
16%6%21%26%24%8%
450
11th to 20thDay
13%320%29%23%11%
450
21st to endDay
15%11%27%21%18%8%
450
October1st to 10thDay
20%8%22%27%17%6%
342
11th to 20thDay
26%14%33%20%7%1
270
21st to endDay
27%12%34%21%5%2
297
November1st to 10thDay
14%15%39%21%11%1
270
11th to 20thDay
19%14%41%17%9%
270
21st to endDay
25%12%38%20%6%
270
December1st to 10thDay
19%15%43%17%6%1
270
11th to 20thDay
20%13%39%18%10%1
270
21st to endDay
22%18%40%17%3
297
January1st to 10thNight
17%14%36%25%8%1
950
11th to 20thNight
20%11%35%26%6%1
900
21st to endNight
19%11%36%27%6%
990
February1st to 10thNight
20%9%38%26%5%1
900
11th to 20thNight
18%14%34%29%5%
738
21st to endNight
24%13%37%22%4
592
March1st to 10thNight
21%10%34%27%7%1
720
11th to 20thNight
18%10%33%31%7%
658
21st to endNight
21%10%29%31%7%1
594
April1st to 10thNight
24%10%36%25%5%
540
11th to 20thNight
25%10%29%29%7%
533
21st to endNight
23%7%32%29%9%
540
May1st to 10thNight
19%7%36%31%6%
540
11th to 20thNight
19%5%34%31%12%
531
21st to endNight
14%5%28%37%17%
584
June1st to 10thNight
11%426%43%15%1
540
11th to 20thNight
14%331%39%13%1
540
21st to endNight
11%326%44%16%
540
July1st to 10thNight
7%215%39%33%3
525
11th to 20thNight
7%220%46%24%2
522
21st to endNight
7%217%51%21%2
591
August1st to 10thNight
9%115%48%25%3
537
11th to 20thNight
9%215%40%30%5%
534
21st to endNight
11%218%41%25%3
594
September1st to 10thNight
9%322%37%23%5%
540
11th to 20thNight
13%421%34%25%4
600
21st to endNight
13%6%27%30%21%2
720
October1st to 10thNight
14%7%29%32%17%2
720
11th to 20thNight
22%9%32%29%8%
720
21st to endNight
24%9%31%27%7%1
792
November1st to 10thNight
16%9%36%27%11%1
740
11th to 20thNight
19%12%39%23%6%
760
21st to endNight
22%12%34%25%7%
926
December1st to 10thNight
22%12%39%21%6%1
950
11th to 20thNight
24%11%34%25%5%
950
21st to endNight
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