Phoenix
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Phoenix 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
77%
24092
37%
74341
34%
24050
82%
24050
55%
34770

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
75%
758
34%
2456
35%
756
79%
756
46%
1196
January11th to 20thNight
73%
720
37%
2340
38%
720
78%
720
48%
1115
January21st to endNight
65%
792
37%
2574
34%
792
73%
792
43%
1293
February1st to 10thNight
73%
720
38%
2246
36%
720
80%
720
53%
1039
February11th to 20thNight
67%
700
35%
2099
32%
700
74%
700
46%
1083
February21st to endNight
65%
592
36%
1772
35%
592
71%
592
48%
882
March1st to 10thNight
69%
720
39%
1980
31%
720
77%
720
56%
973
March11th to 20thNight
74%
720
39%
1980
33%
720
80%
720
58%
971
March21st to endNight
72%
792
40%
2178
30%
792
80%
792
60%
1053
April1st to 10thNight
74%
720
36%
1980
25%
720
81%
720
64%
923
April11th to 20thNight
68%
623
40%
1867
29%
623
78%
623
66%
787
April21st to endNight
72%
540
48%
1628
37%
540
82%
540
73%
651
May1st to 10thNight
73%
540
42%
1620
34%
540
81%
540
67%
676
May11th to 20thNight
78%
531
42%
1594
35%
531
81%
531
70%
654
May21st to endNight
80%
582
41%
1746
33%
582
84%
582
77%
683
June1st to 10thNight
85%
540
38%
1620
33%
540
87%
540
72%
654
June11th to 20thNight
88%
540
41%
1620
35%
540
90%
540
87%
591
June21st to endNight
85%
540
33%
1620
29%
540
87%
540
66%
692
July1st to 10thNight
86%
525
29%
1575
24%
525
87%
525
53%
768
July11th to 20thNight
85%
522
29%
1566
25%
522
85%
522
49%
796
July21st to endNight
81%
591
27%
1674
23%
558
82%
558
38%
957
August1st to 10thNight
88%
537
31%
1602
27%
534
88%
534
52%
792
August11th to 20thNight
85%
534
35%
1602
31%
534
85%
534
45%
839
August21st to endNight
84%
722
32%
2018
29%
722
84%
722
48%
1085
September1st to 10thNight
82%
720
34%
1980
30%
720
83%
720
52%
1042
September11th to 20thNight
85%
720
43%
1980
37%
720
87%
720
69%
896
September21st to endNight
85%
720
40%
1980
32%
720
88%
720
65%
922
October1st to 10thNight
82%
720
41%
2001
33%
720
86%
720
64%
931
October11th to 20thNight
85%
720
45%
2160
42%
720
88%
720
75%
861
October21st to endNight
81%
792
47%
2376
40%
792
88%
792
75%
944
November1st to 10thNight
82%
740
44%
2220
41%
740
85%
740
65%
961
November11th to 20thNight
84%
760
42%
2441
42%
760
88%
760
63%
1022
November21st to endNight
73%
760
40%
2470
39%
760
79%
760
52%
1121
December1st to 10thNight
75%
760
39%
2470
41%
760
78%
760
49%
1167
December11th to 20thNight
70%
758
34%
2939
38%
758
74%
758
35%
1551
December21st to endNight
68%
821
23%
4367
36%
817
72%
817
26%
2199

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
3213323346%70%
74916
Night
4213323346%68%
74803
TransparencyDay
17%2412%25%41%
74643
Night
18%2311%23%43%
74598
SeeingDay
4414%31%33%14%
13870
Night
4211%44%36%3
24117

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 10thDay
5%324413247%64%
1699
11th to 20thDay
5%324213345%66%
1620
21st to endDay
6%324423347%63%
1782
February1st to 10thDay
3313212347%69%
1710
11th to 20thDay
6%5%23323347%63%
1750
21st to endDay
5%324313446%66%
1484
March1st to 10thDay
421333445%7%64%
1980
11th to 20thDay
431331335%7%66%
1980
21st to endDay
3212324335%71%
2178
April1st to 10thDay
2112223347%73%
1980
11th to 20thDay
2212223335%77%
2041
21st to endDay
2111212235%80%
2329
May1st to 10thDay
1112212235%81%
2340
11th to 20thDay
1112113325%79%
2301
21st to endDay
111111111387%
2530
June1st to 10thDay
1111212225%82%
2340
11th to 20thDay
11111112389%
2340
21st to endDay
1112212235%80%
2340
July1st to 10thDay
221342445%8%66%
2340
11th to 20thDay
23245%346%8%13%51%
2340
21st to endDay
4325%5%35%6%8%10%48%
2545
August1st to 10thDay
32133345%6%9%61%
2328
11th to 20thDay
32144245%7%10%57%
2299
21st to endDay
221342446%9%64%
2333
September1st to 10thDay
331332246%6%66%
1980
11th to 20thDay
221221233478%
1980
21st to endDay
211232333477%
1980
October1st to 10thDay
322313446%73%
1958
11th to 20thDay
11111222484%
1800
21st to endDay
111221223481%
1980
November1st to 10thDay
2112213336%77%
1859
11th to 20thDay
1213323235%76%
1735
21st to endDay
5%413322347%66%
1710
December1st to 10thDay
5%4244345%45%60%
1710
11th to 20thDay
5%425%4335%7%7%54%
2169
21st to endDay
9%6%25%4335%5%7%53%
3146
January1st to 10thNight
5%324324447%61%
2456
11th to 20thNight
6%324323335%67%
2340
21st to endNight
8%315%424335%62%
2574
February1st to 10thNight
3322223336%69%
2246
11th to 20thNight
6%324423436%63%
2098
21st to endNight
6%323423335%66%
1772
March1st to 10thNight
321332345%7%66%
1980
11th to 20thNight
5%312313336%69%
1980
21st to endNight
4212323347%69%
2178
April1st to 10thNight
2212323447%71%
1980
11th to 20thNight
221221233478%
1867
21st to endNight
2112112235%81%
1628
May1st to 10thNight
1212213345%77%
1620
11th to 20thNight
21221223381%
1594
21st to endNight
21111122287%
1746
June1st to 10thNight
211212336%79%
1620
11th to 20thNight
111113488%
1620
21st to endNight
211222223478%
1620
July1st to 10thNight
2223425%5%6%8%62%
1620
11th to 20thNight
22145%346%7%11%55%
1620
21st to endNight
4425%446%6%10%12%44%
1773
August1st to 10thNight
2212335%6%7%10%58%
1611
11th to 20thNight
2324435%6%6%8%55%
1602
21st to endNight
2314435%5%7%8%58%
2018
September1st to 10thNight
34134235%6%8%60%
1980
11th to 20thNight
211321234477%
1980
21st to endNight
2212223335%75%
1980
October1st to 10thNight
3212223335%74%
2001
11th to 20thNight
1211111235%83%
2160
21st to endNight
111221222482%
2376
November1st to 10thNight
2212212346%75%
2220
11th to 20thNight
2212222225%76%
2441
21st to endNight
5%213323346%68%
2470
December1st to 10thNight
5%313413347%64%
2470
11th to 20thNight
7%5%25%5%2445%7%54%
3041
21st to endNight
8%5%245%345%45%55%
4521

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
23%25%18%31%21%
1700
11th to 20thDay
22%3312%30%30%
1620
21st to endDay
23%2416%27%28%
1782
February1st to 10thDay
17%2316%26%35%
1710
11th to 20thDay
24%3413%26%30%
1760
21st to endDay
20%2213%31%31%
1484
March1st to 10thDay
21%2212%29%35%
1980
11th to 20thDay
19%1312%28%37%
1980
21st to endDay
18%139%35%34%
2178
April1st to 10thDay
13%128%35%41%
1980
11th to 20thDay
12%127%26%53%
2044
21st to endDay
9%127%25%56%
2329
May1st to 10thDay
9%127%24%57%
2340
11th to 20thDay
10%128%23%56%
2304
21st to endDay
7%11423%65%
2530
June1st to 10thDay
9%11319%67%
2340
11th to 20thDay
6%1129%82%
2340
21st to endDay
11%12413%69%
2340
July1st to 10thDay
17%35%9%18%48%
2276
11th to 20thDay
23%6%10%22%24%16%
2271
21st to endDay
27%5%13%22%18%14%
2404
August1st to 10thDay
21%48%16%19%33%
2313
11th to 20thDay
20%48%20%23%25%
2299
21st to endDay
18%5%5%16%29%27%
2333
September1st to 10thDay
20%4412%24%36%
1980
11th to 20thDay
11%326%28%50%
1980
21st to endDay
13%325%23%54%
1980
October1st to 10thDay
15%2312%24%44%
1958
11th to 20thDay
7%236%25%58%
1800
21st to endDay
10%139%28%49%
1980
November1st to 10thDay
10%2214%31%41%
1859
11th to 20thDay
15%2211%28%43%
1735
21st to endDay
21%2211%27%37%
1710
December1st to 10thDay
26%3414%24%29%
1710
11th to 20thDay
29%36%19%25%19%
2168
21st to endDay
31%37%21%26%13%
3146
January1st to 10thNight
23%25%15%29%26%
2456
11th to 20thNight
23%1312%28%33%
2340
21st to endNight
27%1314%26%30%
2574
February1st to 10thNight
19%2311%25%39%
2246
11th to 20thNight
25%2312%24%33%
2099
21st to endNight
23%1310%26%36%
1772
March1st to 10thNight
19%2211%25%41%
1980
11th to 20thNight
18%1110%25%44%
1980
21st to endNight
16%239%32%38%
2178
April1st to 10thNight
14%228%26%48%
1980
11th to 20thNight
11%225%24%56%
1867
21st to endNight
9%125%20%63%
1628
May1st to 10thNight
12%126%22%57%
1620
11th to 20thNight
10%126%19%62%
1595
21st to endNight
8%11415%72%
1746
June1st to 10thNight
10%11314%71%
1620
11th to 20thNight
411210%82%
1620
21st to endNight
12%2338%72%
1620
July1st to 10thNight
19%4411%14%48%
1575
11th to 20thNight
21%5%8%22%24%20%
1566
21st to endNight
29%6%11%20%18%17%
1674
August1st to 10thNight
19%5%7%18%18%33%
1602
11th to 20thNight
24%5%9%17%19%27%
1602
21st to endNight
23%5%6%13%24%29%
2018
September1st to 10thNight
22%37%15%19%34%
1980
11th to 20thNight
12%239%22%52%
1980
21st to endNight
14%226%18%58%
1980
October1st to 10thNight
15%2311%20%49%
2001
11th to 20thNight
9%127%20%62%
2160
21st to endNight
9%128%21%59%
2376
November1st to 10thNight
13%228%28%47%
2220
11th to 20thNight
14%139%25%48%
2441
21st to endNight
20%2210%27%39%
2470
December1st to 10thNight
21%3417%22%34%
2470
11th to 20thNight
31%2414%26%23%
3041
21st to endNight
30%6%5%17%24%19%
4521

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
9%313%43%27%5%
267
11th to 20thDay
11%311%36%32%7%
240
21st to endDay
35%17%39%25%11%
264
February1st to 10thDay
5%319%33%30%10%
330
11th to 20thDay
10%9%22%36%19%5%
415
21st to endDay
9%8%26%38%16%3
346
March1st to 10thDay
7%8%22%37%20%5%
420
11th to 20thDay
6%7%20%33%24%10%
420
21st to endDay
5%11%24%35%20%4
462
April1st to 10thDay
310%19%32%27%10%
420
11th to 20thDay
210%26%31%25%6%
412
21st to endDay
310%21%31%24%12%
420
May1st to 10thDay
26%23%31%28%11%
423
11th to 20thDay
2416%37%32%10%
448
21st to endDay
17%17%36%30%9%
485
June1st to 10thDay
2212%35%36%14%
450
11th to 20thDay
1315%32%32%17%
450
21st to endDay
218%35%41%14%
450
July1st to 10thDay
116%26%44%23%
446
11th to 20thDay
315%20%45%27%
444
21st to endDay
31322%40%31%
487
August1st to 10thDay
21420%46%27%
447
11th to 20thDay
31322%46%25%
437
21st to endDay
1319%46%31%
495
September1st to 10thDay
5%18%26%44%17%
450
11th to 20thDay
328%30%43%14%
450
21st to endDay
3212%30%33%18%
450
October1st to 10thDay
3314%33%34%13%
428
11th to 20thDay
3113%29%38%16%
270
21st to endDay
1412%27%40%16%
297
November1st to 10thDay
2212%35%39%9%
270
11th to 20thDay
339%37%39%10%
270
21st to endDay
6%415%37%28%10%
270
December1st to 10thDay
9%10%41%33%7%
270
11th to 20thDay
4315%41%31%6%
270
21st to endDay
12%418%35%26%5%
297
January1st to 10thNight
6%111%52%28%2
760
11th to 20thNight
7%211%48%30%2
720
21st to endNight
10%217%46%23%3
792
February1st to 10thNight
5%216%47%27%4
720
11th to 20thNight
7%317%51%21%1
704
21st to endNight
8%416%51%20%1
592
March1st to 10thNight
4320%53%18%2
720
11th to 20thNight
7%313%44%28%5%
720
21st to endNight
4415%48%28%2
792
April1st to 10thNight
3315%52%26%2
720
11th to 20thNight
3421%47%24%1
623
21st to endNight
2221%48%24%3
540
May1st to 10thNight
1419%46%29%2
540
11th to 20thNight
2216%47%32%2
531
21st to endNight
2214%50%30%2
584
June1st to 10thNight
219%51%35%1
540
11th to 20thNight
110%52%36%1
540
21st to endNight
217%42%46%2
540
July1st to 10thNight
215%39%50%3
525
11th to 20thNight
2431%59%4
522
21st to endNight
32423%59%9%
591
August1st to 10thNight
21224%61%10%
537
11th to 20thNight
21326%62%5%
534
21st to endNight
31420%64%9%
722
September1st to 10thNight
416%29%55%5%
720
11th to 20thNight
217%38%49%4
720
21st to endNight
218%42%41%6%
720
October1st to 10thNight
4110%49%35%2
720
11th to 20thNight
38%48%39%2
720
21st to endNight
2112%41%39%6%
792
November1st to 10thNight
419%46%36%4
740
11th to 20thNight
39%48%38%3
760
21st to endNight
6%212%47%31%3
760
December1st to 10thNight
6%210%49%32%1
760
11th to 20thNight
8%311%51%26%2
760
21st to endNight
8%313%50%23%3
836
Page generated at 2024-01-07 08:06:54. Version ac07

Copyright 2024 Attilla Danko


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