Tucson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tucson clear sky chart from 2005-11-05 to 2018-02-22.

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
77%
16209
36%
48865
32%
16171
81%
16171
55%
23045

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
72%
778
32%
2522
32%
776
77%
776
50%
1170
January16th to endNight
69%
832
36%
2704
35%
832
76%
832
45%
1342
February1st to 15thNight
75%
760
37%
2391
37%
760
81%
760
54%
1098
February16th to endNight
67%
660
38%
1918
34%
660
73%
660
50%
978
March1st to 15thNight
68%
720
40%
1980
32%
720
76%
720
60%
954
March16th to endNight
76%
768
39%
2112
29%
768
83%
768
63%
994
April1st to 15thNight
70%
685
35%
1944
27%
685
77%
685
58%
919
April16th to endNight
75%
540
45%
1788
41%
540
84%
540
71%
656
May1st to 15thNight
75%
539
41%
1619
32%
539
82%
539
75%
633
May16th to endNight
79%
561
42%
1684
35%
561
83%
561
75%
656
June1st to 15thNight
85%
540
35%
1620
31%
540
86%
540
71%
662
June16th to endNight
86%
540
32%
1620
28%
540
87%
540
65%
698
July1st to 15thNight
84%
510
20%
1530
18%
510
84%
510
41%
829
July16th to endNight
83%
564
18%
1593
16%
531
82%
531
31%
973
August1st to 15thNight
87%
539
25%
1611
23%
536
88%
536
44%
864
August16th to endNight
85%
597
31%
1875
32%
597
85%
597
41%
1002
September1st to 15thNight
80%
720
29%
1980
25%
720
81%
720
43%
1135
September16th to endNight
81%
716
44%
1980
34%
716
87%
716
67%
904
October1st to 15thNight
83%
720
40%
2091
34%
720
87%
720
67%
919
October16th to endNight
88%
768
45%
2304
42%
768
90%
768
70%
975
November1st to 15thNight
81%
760
42%
2280
38%
760
84%
760
66%
983
November16th to endNight
74%
780
40%
2480
38%
780
80%
780
53%
1139
December1st to 15thNight
71%
780
37%
2535
37%
780
76%
780
49%
1188
December16th to endNight
70%
832
35%
2704
37%
832
74%
832
43%
1374

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
3112323346%66%
49383
Night
3112213346%68%
49061
TransparencyDay
18%46%11%24%35%
49078
Night
17%36%12%25%34%
48867
SeeingDay
5%7%21%34%23%7%
5919
Night
4112%40%36%5%
16218

By Month

Percentage Cloud Cover SW (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
4212313446%65%
1746
16th to endDay
7%312322336%64%
1872
February1st to 15thDay
6%21222233469%
1800
16th to endDay
7%212323335%63%
1701
March1st to 15thDay
412313346%68%
1980
16th to endDay
3111112335%75%
2112
April1st to 15thDay
31122246%72%
2003
16th to endDay
1111112382%
2169
May1st to 15thDay
1121213480%
2331
16th to endDay
1111122384%
2429
June1st to 15thDay
211112135%79%
2340
16th to endDay
112112346%73%
2340
July1st to 15thDay
42145%36%8%8%8%46%
2340
16th to endDay
6%425%7%47%8%8%11%32%
2467
August1st to 15thDay
5%325%5%35%6%7%8%45%
2340
16th to endDay
32145%36%6%7%8%50%
2321
September1st to 15thDay
5%2235%45%5%5%6%52%
1980
16th to endDay
3111212335%73%
1980
October1st to 15thDay
22212235%76%
1869
16th to endDay
1111223479%
1920
November1st to 15thDay
1111135%6%76%
1909
16th to endDay
322212335%72%
1807
December1st to 15thDay
7%22223247%63%
1755
16th to endDay
6%21332335%6%63%
1872
January1st to 15thNight
5%212212445%66%
2522
16th to endNight
6%213313345%62%
2704
February1st to 15thNight
412213246%69%
2380
16th to endNight
7%212213446%63%
1918
March1st to 15thNight
5%112213236%70%
1980
16th to endNight
31221223474%
2112
April1st to 15thNight
222213345%71%
1944
16th to endNight
21111385%
1788
May1st to 15thNight
111236%79%
1619
16th to endNight
111112385%
1684
June1st to 15thNight
111122481%
1620
16th to endNight
1111212235%75%
1620
July1st to 15thNight
1214425%7%6%11%52%
1620
16th to endNight
32145%35%8%9%15%40%
1701
August1st to 15thNight
1212325%5%7%10%57%
1620
16th to endNight
221343448%9%53%
1875
September1st to 15thNight
42144245%6%7%56%
1980
16th to endNight
212211235%76%
1980
October1st to 15thNight
11111223478%
2091
16th to endNight
11111222480%
2304
November1st to 15thNight
112212235%75%
2280
16th to endNight
5%212212335%69%
2480
December1st to 15thNight
7%212212336%67%
2535
16th to endNight
8%213423335%62%
2704

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
20%45%13%26%29%
1747
16th to endDay
22%3413%26%29%
1872
February1st to 15thDay
20%2412%26%34%
1800
16th to endDay
23%25%13%28%26%
1701
March1st to 15thDay
17%237%30%39%
1980
16th to endDay
13%248%30%40%
2112
April1st to 15thDay
13%136%36%38%
2003
16th to endDay
9%127%23%56%
2169
May1st to 15thDay
9%237%20%57%
2331
16th to endDay
7%136%23%57%
2432
June1st to 15thDay
9%12319%63%
2340
16th to endDay
12%35%6%16%56%
2340
July1st to 15thDay
28%10%13%14%14%18%
2201
16th to endDay
40%13%17%18%8%2
2312
August1st to 15thDay
32%9%12%14%16%13%
2325
16th to endDay
28%7%12%17%17%15%
2321
September1st to 15thDay
29%6%10%17%15%20%
1980
16th to endDay
14%249%33%35%
1980
October1st to 15thDay
11%35%10%26%42%
1869
16th to endDay
10%149%26%48%
1920
November1st to 15thDay
9%2411%33%37%
1909
16th to endDay
15%248%28%39%
1807
December1st to 15thDay
22%25%15%30%23%
1755
16th to endDay
22%38%17%31%17%
1872
January1st to 15thNight
19%36%12%28%29%
2522
16th to endNight
22%45%13%29%24%
2704
February1st to 15thNight
17%25%15%24%34%
2391
16th to endNight
22%25%11%31%25%
1918
March1st to 15thNight
16%2410%26%39%
1980
16th to endNight
14%2310%32%36%
2112
April1st to 15thNight
16%238%34%35%
1944
16th to endNight
7%117%25%55%
1788
May1st to 15thNight
7%15%8%26%51%
1620
16th to endNight
7%126%24%57%
1685
June1st to 15thNight
9%12418%62%
1620
16th to endNight
12%145%17%58%
1620
July1st to 15thNight
21%10%16%17%15%18%
1530
16th to endNight
27%14%22%23%9%2
1593
August1st to 15thNight
19%10%15%19%19%14%
1611
16th to endNight
24%6%15%19%18%15%
1875
September1st to 15thNight
24%7%10%21%18%17%
1980
16th to endNight
11%3311%34%35%
1980
October1st to 15thNight
10%3412%26%42%
2091
16th to endNight
10%2310%24%48%
2304
November1st to 15thNight
12%1413%32%34%
2280
16th to endNight
18%2410%24%39%
2480
December1st to 15thNight
20%25%15%30%25%
2535
16th to endNight
25%27%15%29%20%
2704

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
8%5%17%41%25%1
135
16th to endDay
6%223%38%21%7%
144
February1st to 15thDay
6%11%17%36%21%6%
225
16th to endDay
12%13%35%26%9%1
264
March1st to 15thDay
5%17%30%26%12%7%
270
16th to endDay
120%33%23%15%5%
288
April1st to 15thDay
5%17%34%24%15%3
269
16th to endDay
225%31%26%12%1
270
May1st to 15thDay
218%34%28%12%4
288
16th to endDay
39%32%37%14%3
330
June1st to 15thDay
4329%41%14%6%
315
16th to endDay
2114%47%25%7%
315
July1st to 15thDay
6%9%40%34%8%
305
16th to endDay
7%6%34%30%19%
327
August1st to 15thDay
6%6%37%34%14%
315
16th to endDay
5%15%35%37%14%
332
September1st to 15thDay
8%115%36%29%6%
315
16th to endDay
6%5%23%32%26%5%
315
October1st to 15thDay
2422%38%23%9%
204
16th to endDay
28%35%41%11%
144
November1st to 15thDay
26%17%40%27%5%
135
16th to endDay
5%324%34%26%4
135
December1st to 15thDay
5%220%37%31%1
135
16th to endDay
11%5%22%30%22%7%
144
January1st to 15thNight
6%115%49%23%3
780
16th to endNight
7%215%44%25%3
832
February1st to 15thNight
5%212%45%30%4
764
16th to endNight
8%318%48%20%1
660
March1st to 15thNight
4419%40%27%3
720
16th to endNight
3314%45%29%4
768
April1st to 15thNight
3416%50%22%1
685
16th to endNight
1417%49%23%2
540
May1st to 15thNight
318%43%30%2
540
16th to endNight
1115%45%33%1
563
June1st to 15thNight
119%47%37%2
540
16th to endNight
16%37%51%2
540
July1st to 15thNight
15%21%65%6%
510
16th to endNight
4117%60%16%
564
August1st to 15thNight
2215%63%15%
539
16th to endNight
3119%61%13%
597
September1st to 15thNight
46%28%49%11%
720
16th to endNight
210%36%41%8%
716
October1st to 15thNight
211%41%38%5%
720
16th to endNight
26%43%38%9%
768
November1st to 15thNight
2111%42%37%4
760
16th to endNight
6%114%40%32%4
780
December1st to 15thNight
8%214%43%26%3
780
16th to endNight
9%212%47%22%5%
832
Page generated at 2018-02-23 09:21:32. Version ac04

Copyright 2018 A. Danko


Tucson Clear Sky Chart |Charts Home