This page made possible by the sponsorship of: Joseph & Amy Galloway.

Des Moines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Des Moines clear sky chart from 2005-11-05 to 2021-11-10.

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
39%
21615
19%
63437
11%
21568
46%
21568
27%
40660

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
30%
1200
15%
3254
6%
1195
37%
1195
23%
2245
January16th to endNight
26%
1280
16%
3328
6%
1280
33%
1280
20%
2434
February1st to 15thNight
24%
1180
12%
3068
4%
1176
29%
1176
19%
2295
February16th to endNight
30%
976
19%
2662
7%
976
38%
976
25%
1808
March1st to 15thNight
33%
720
23%
2640
14%
720
45%
720
23%
1596
March16th to endNight
25%
768
10%
2816
6%
768
31%
768
13%
2018
April1st to 15thNight
28%
719
18%
2410
11%
719
41%
719
22%
1527
April16th to endNight
30%
714
16%
2260
10%
714
41%
714
22%
1514
May1st to 15thNight
38%
720
16%
2128
10%
720
44%
720
24%
1413
May16th to endNight
44%
755
16%
2010
8%
753
49%
753
27%
1366
June1st to 15thNight
56%
720
20%
1920
10%
720
60%
720
39%
1143
June16th to endNight
51%
720
19%
1920
9%
720
55%
720
38%
1153
July1st to 15thNight
73%
690
21%
1840
12%
690
74%
690
51%
979
July16th to endNight
73%
756
23%
2123
19%
723
76%
723
47%
1110
August1st to 15thNight
66%
710
22%
2122
23%
707
69%
707
36%
1209
August16th to endNight
64%
765
24%
2427
26%
765
69%
765
36%
1336
September1st to 15thNight
57%
720
29%
2400
28%
720
63%
720
36%
1299
September16th to endNight
53%
757
26%
2656
22%
757
62%
757
36%
1383
October1st to 15thNight
36%
960
23%
2880
13%
960
43%
960
27%
1808
October16th to endNight
35%
1024
21%
3072
11%
1024
44%
1024
28%
1893
November1st to 15thNight
34%
1081
24%
3197
12%
1081
45%
1081
31%
1899
November16th to endNight
29%
1200
19%
3360
8%
1200
38%
1200
26%
2188
December1st to 15thNight
27%
1200
14%
3360
5%
1200
36%
1200
20%
2396
December16th to endNight
25%
1280
17%
3584
6%
1280
34%
1280
18%
2648

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%3445%7%39%
64526
Night
12%7%35%424446%44%
63617
Cloud CoverDay
13%7%36%5%3445%7%39%
64535
Night
12%7%35%424446%44%
63621
TransparencyDay
43%6%13%22%12%1
64224
Night
40%5%13%24%14%2
63437
SeeingDay
16%8%28%28%15%3
11694
Night
15%7%31%32%11%
21615

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
10%11%410%5%34447%33%
2000
16th to endDay
13%13%6%9%7%35%446%24%
2304
February1st to 15thDay
14%12%48%6%34436%30%
2115
16th to endDay
13%9%48%6%45%346%33%
1991
March1st to 15thDay
14%9%5%6%42445%7%34%
2629
16th to endDay
19%12%47%5%33345%30%
2816
April1st to 15thDay
17%9%36%324445%37%
2857
16th to endDay
20%7%36%5%24446%33%
2963
May1st to 15thDay
18%7%36%5%35%5%5%7%33%
3142
16th to endDay
16%7%26%6%35%5%5%7%34%
3513
June1st to 15thDay
10%425%5%3445%8%44%
3360
16th to endDay
8%5%246%35%5%7%9%43%
3360
July1st to 15thDay
6%3245%3446%9%49%
3360
16th to endDay
5%3244345%7%9%48%
3343
August1st to 15thDay
7%424445%6%6%9%44%
3071
16th to endDay
10%425%434447%48%
3183
September1st to 15thDay
13%423323346%52%
2880
16th to endDay
11%31442345%7%51%
2604
October1st to 15thDay
17%6%35%422335%45%
2400
16th to endDay
15%8%35%423346%42%
2560
November1st to 15thDay
12%5%3342345%6%48%
2187
16th to endDay
16%8%35%5%2345%7%38%
1920
December1st to 15thDay
14%10%49%6%2435%6%31%
1920
16th to endDay
14%14%310%6%34436%27%
2048
January1st to 15thNight
10%9%37%6%4445%7%36%
3254
16th to endNight
12%11%47%5%35%445%34%
3328
February1st to 15thNight
13%11%49%7%24445%31%
3065
16th to endNight
12%7%47%434435%41%
2662
March1st to 15thNight
13%8%35%413346%46%
2628
16th to endNight
19%10%47%5%34446%30%
2816
April1st to 15thNight
14%6%35%5%24436%43%
2410
16th to endNight
17%7%35%5%23345%39%
2260
May1st to 15thNight
16%5%13425%5%5%8%39%
2128
16th to endNight
13%6%235%245%5%7%41%
2008
June1st to 15thNight
7%41442445%8%52%
1920
16th to endNight
7%4144246%5%8%50%
1920
July1st to 15thNight
5%11222346%9%60%
1920
16th to endNight
42124235%5%9%57%
2230
August1st to 15thNight
5%32442445%7%54%
2132
16th to endNight
8%313323347%56%
2427
September1st to 15thNight
11%323323335%57%
2400
16th to endNight
10%413213347%57%
2656
October1st to 15thNight
16%6%25%422336%47%
2880
16th to endNight
14%6%24423346%49%
3072
November1st to 15thNight
11%5%24424347%50%
3197
16th to endNight
15%7%35%333345%45%
3360
December1st to 15thNight
12%10%38%6%34345%35%
3360
16th to endNight
15%10%5%8%6%2445%432%
3584

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
9%11%410%6%34447%32%
2000
16th to endDay
13%12%6%9%7%35%446%25%
2304
February1st to 15thDay
13%13%48%6%44436%30%
2115
16th to endDay
14%9%47%6%34446%34%
1991
March1st to 15thDay
15%9%46%5%33447%35%
2640
16th to endDay
19%11%5%6%6%33345%30%
2814
April1st to 15thDay
17%9%36%424446%36%
2857
16th to endDay
20%7%26%5%2445%6%33%
2963
May1st to 15thDay
18%7%35%5%35%46%6%33%
3142
16th to endDay
15%8%35%6%45%45%7%34%
3513
June1st to 15thDay
10%4245%2445%9%44%
3360
16th to endDay
7%5%245%35%5%7%9%42%
3360
July1st to 15thDay
6%3245%35%45%9%49%
3360
16th to endDay
5%324425%46%9%49%
3343
August1st to 15thDay
7%4245%35%6%6%9%44%
3071
16th to endDay
10%425%434446%48%
3183
September1st to 15thDay
13%414323346%52%
2880
16th to endDay
10%324324447%50%
2604
October1st to 15thDay
16%7%25%42224445%
2400
16th to endDay
15%8%25%423446%43%
2560
November1st to 15thDay
11%6%3442345%6%47%
2187
16th to endDay
16%8%345%23347%38%
1920
December1st to 15thDay
14%10%5%9%6%2445%6%31%
1920
16th to endDay
14%14%410%6%34436%27%
2048
January1st to 15thNight
10%9%47%6%3445%7%36%
3254
16th to endNight
12%11%5%7%5%35%445%34%
3328
February1st to 15thNight
12%12%5%9%6%24345%32%
3058
16th to endNight
12%8%47%5%34336%41%
2662
March1st to 15thNight
13%8%25%323336%46%
2640
16th to endNight
18%10%46%5%34446%30%
2816
April1st to 15thNight
14%6%36%423446%42%
2410
16th to endNight
18%7%36%42335%5%39%
2260
May1st to 15thNight
16%6%134345%6%8%39%
2127
16th to endNight
13%6%245%345%5%8%41%
2008
June1st to 15thNight
7%41342435%8%52%
1920
16th to endNight
7%4145%245%5%8%50%
1920
July1st to 15thNight
5%21232335%10%59%
1920
16th to endNight
42123235%6%9%58%
2230
August1st to 15thNight
5%32442346%8%53%
2132
16th to endNight
8%32332345%7%56%
2427
September1st to 15thNight
10%414323335%57%
2400
16th to endNight
10%413223346%57%
2656
October1st to 15thNight
15%7%25%322336%47%
2880
16th to endNight
14%6%24423346%48%
3072
November1st to 15thNight
11%5%24323337%50%
3197
16th to endNight
15%8%35%423336%45%
3360
December1st to 15thNight
12%10%38%6%34346%34%
3360
16th to endNight
14%11%5%8%6%34445%32%
3584

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
50%5%13%20%9%
2001
16th to endDay
59%6%12%15%5%
2304
February1st to 15thDay
55%413%17%6%
2116
16th to endDay
50%5%13%18%9%2
1991
March1st to 15thDay
48%5%13%21%10%1
2640
16th to endDay
56%5%12%15%7%1
2816
April1st to 15thDay
48%6%10%24%9%
2857
16th to endDay
50%6%12%20%10%
2963
May1st to 15thDay
49%7%13%19%10%
3142
16th to endDay
48%7%13%18%10%1
3517
June1st to 15thDay
35%6%16%22%16%1
3360
16th to endDay
35%9%15%24%13%1
3360
July1st to 15thDay
30%8%15%28%13%3
3211
16th to endDay
27%8%16%28%16%2
3187
August1st to 15thDay
33%9%16%25%14%1
3057
16th to endDay
35%6%11%26%16%3
3183
September1st to 15thDay
32%5%13%25%19%2
2880
16th to endDay
32%5%13%30%17%
2604
October1st to 15thDay
42%39%23%18%2
2400
16th to endDay
42%410%24%15%1
2560
November1st to 15thDay
35%5%15%22%18%1
2187
16th to endDay
46%5%14%22%11%
1920
December1st to 15thDay
53%415%17%8%
1920
16th to endDay
59%412%15%6%1
2048
January1st to 15thNight
46%416%19%12%
3254
16th to endNight
51%5%14%18%9%
3328
February1st to 15thNight
54%412%19%7%1
3068
16th to endNight
44%411%22%14%1
2662
March1st to 15thNight
39%5%11%28%14%1
2640
16th to endNight
54%6%13%16%7%1
2816
April1st to 15thNight
41%5%10%25%14%1
2410
16th to endNight
45%5%14%19%13%2
2260
May1st to 15thNight
40%8%15%22%12%1
2128
16th to endNight
41%7%13%22%11%2
2010
June1st to 15thNight
29%6%16%26%18%3
1920
16th to endNight
29%7%15%25%19%3
1920
July1st to 15thNight
19%5%19%34%16%4
1840
16th to endNight
19%7%17%33%19%2
2123
August1st to 15thNight
27%8%13%30%17%2
2122
16th to endNight
27%7%12%27%19%5%
2427
September1st to 15thNight
29%410%26%24%3
2400
16th to endNight
27%411%32%21%2
2656
October1st to 15thNight
39%5%8%22%20%3
2880
16th to endNight
37%5%12%23%19%3
3072
November1st to 15thNight
34%413%25%18%3
3197
16th to endNight
41%412%27%11%1
3360
December1st to 15thNight
50%413%21%8%
3360
16th to endNight
53%5%11%18%9%
3584

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
19%12%34%23%7%1
270
16th to endDay
23%10%37%22%5%
288
February1st to 15thDay
23%17%35%20%2
270
16th to endDay
25%10%40%17%5%1
240
March1st to 15thDay
23%11%41%17%6%
270
16th to endDay
31%13%29%19%5%
288
April1st to 15thDay
23%13%32%20%8%
496
16th to endDay
22%12%30%23%9%1
615
May1st to 15thDay
21%11%33%20%11%1
768
16th to endDay
18%10%25%28%13%2
837
June1st to 15thDay
10%5%24%33%21%4
795
16th to endDay
9%5%32%32%16%3
795
July1st to 15thDay
5%319%32%28%10%
775
16th to endDay
6%118%39%28%5%
835
August1st to 15thDay
9%119%38%24%5%
774
16th to endDay
13%317%34%25%6%
711
September1st to 15thDay
14%323%29%21%7%
555
16th to endDay
9%6%29%33%16%2
335
October1st to 15thDay
22%14%29%21%9%2
315
16th to endDay
19%14%33%23%7%
336
November1st to 15thDay
14%9%41%23%8%3
298
16th to endDay
28%11%34%20%4
270
December1st to 15thDay
17%11%35%22%11%1
270
16th to endDay
21%13%39%19%6%
288
January1st to 15thNight
15%10%34%29%9%
1200
16th to endNight
18%10%35%29%5%
1280
February1st to 15thNight
18%10%36%28%4
1180
16th to endNight
17%10%37%28%5%1
976
March1st to 15thNight
18%10%34%28%8%1
720
16th to endNight
23%10%35%23%6%
768
April1st to 15thNight
17%12%37%28%4
719
16th to endNight
19%8%36%26%7%1
714
May1st to 15thNight
17%7%33%32%8%
720
16th to endNight
16%6%27%34%14%
755
June1st to 15thNight
10%226%45%15%
720
16th to endNight
7%429%44%14%
720
July1st to 15thNight
5%14%45%31%2
690
16th to endNight
4115%49%28%1
756
August1st to 15thNight
6%16%49%23%2
710
16th to endNight
9%218%41%26%2
765
September1st to 15thNight
13%320%36%22%2
720
16th to endNight
12%426%37%18%
757
October1st to 15thNight
19%7%32%27%11%1
960
16th to endNight
18%9%31%31%8%
1024
November1st to 15thNight
14%10%37%28%8%
1081
16th to endNight
19%10%37%25%6%
1200
December1st to 15thNight
18%11%35%27%6%
1200
16th to endNight
21%9%33%29%5%
1280
Page generated at 2021-11-11 17:33:37. Version ac04

Copyright 2021 A. Danko


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