Des Moines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Des Moines clear sky chart from 2005-11-06 to 2025-11-03.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	12% 8% 3 7% 5% 4 4 4 5% 7% 40%	126960
	Night	12% 8% 3 8% 4 4 4 3 5% 7% 43%	123341
Transparency	Day	41% 6% 13% 24% 14% 2	130561
	Night	40% 5% 12% 24% 15% 2	127816
Seeing	Day	15% 10% 29% 28% 15% 3	17222
	Night	15% 9% 32% 32% 11% 1	27019

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	8% 12% 5% 20% 7% 6% 4 3 4 5% 25%	3641
	11th to 20th	Day	6% 10% 4 12% 6% 5% 7% 5% 7% 6% 31%	4080
	21st to end	Day	11% 13% 6% 13% 5% 5% 5% 4 4 5% 30%	4488
February	1st to 10th	Day	12% 13% 5% 11% 6% 4 5% 4 4 7% 29%	1800
	11th to 20th	Day	12% 11% 4 8% 5% 6% 4 3 5% 6% 36%	1754
	21st to end	Day	14% 10% 4 8% 6% 5% 4 3 4 6% 36%	1600
March	1st to 10th	Day	18% 9% 3 6% 3 3 3 2 3 5% 46%	4936
	11th to 20th	Day	12% 7% 3 6% 4 3 4 3 5% 8% 47%	4980
	21st to end	Day	20% 13% 5% 8% 5% 4 4 3 5% 6% 26%	5462
April	1st to 10th	Day	16% 11% 3 7% 4 4 4 4 5% 6% 36%	2383
	11th to 20th	Day	16% 9% 3 8% 4 5% 4 3 5% 6% 37%	2374
	21st to end	Day	21% 8% 2 7% 4 4 4 3 6% 6% 34%	2545
May	1st to 10th	Day	14% 8% 2 7% 5% 5% 5% 4 6% 7% 39%	5862
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 5% 6% 47%	6180
	21st to end	Day	15% 8% 2 7% 5% 5% 5% 4 6% 8% 37%	6935
June	1st to 10th	Day	9% 5% 3 6% 5% 4 4 4 6% 9% 44%	2800
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 4 7% 11% 45%	2800
	21st to end	Day	9% 6% 3 6% 5% 5% 5% 4 6% 8% 43%	2800
July	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 4 7% 10% 42%	6360
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 3 6% 8% 49%	6251
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 43%	6422
August	1st to 10th	Day	8% 5% 2 5% 4 4 6% 4 7% 10% 45%	4234
	11th to 20th	Day	13% 7% 3 6% 4 4 4 4 6% 8% 40%	4171
	21st to end	Day	7% 5% 3 6% 5% 5% 5% 4 6% 7% 48%	4393
September	1st to 10th	Day	12% 5% 2 5% 3 2 3 2 4 7% 55%	2400
	11th to 20th	Day	10% 4 2 6% 3 4 4 4 6% 8% 49%	2325
	21st to end	Day	11% 4 2 5% 3 4 4 4 5% 7% 51%	2129
October	1st to 10th	Day	13% 7% 2 6% 4 3 3 2 4 6% 51%	2000
	11th to 20th	Day	15% 7% 2 6% 4 4 3 3 4 4 47%	2000
	21st to end	Day	14% 9% 3 7% 4 3 4 3 5% 7% 42%	2200
November	1st to 10th	Day	12% 6% 2 5% 4 3 4 4 7% 6% 47%	1855
	11th to 20th	Day	13% 8% 4 7% 5% 3 3 4 5% 7% 40%	1600
	21st to end	Day	15% 10% 4 5% 5% 4 4 3 5% 7% 39%	1600
December	1st to 10th	Day	7% 7% 3 7% 4 4 3 3 5% 6% 50%	2610
	11th to 20th	Day	12% 10% 4 14% 6% 5% 5% 4 5% 6% 29%	3008
	21st to end	Day	21% 18% 8% 12% 4 4 3 3 4 4 19%	3982
January	1st to 10th	Night	9% 12% 5% 20% 7% 5% 4 3 5% 6% 26%	6320
	11th to 20th	Night	9% 11% 5% 10% 7% 5% 6% 4 6% 6% 32%	5900
	21st to end	Night	11% 13% 5% 12% 5% 5% 4 4 4 5% 33%	6490
February	1st to 10th	Night	11% 11% 5% 10% 6% 4 5% 3 5% 6% 33%	2600
	11th to 20th	Night	11% 11% 3 8% 5% 4 4 4 5% 6% 40%	2533
	21st to end	Night	11% 9% 4 9% 5% 4 4 3 3 6% 43%	2047
March	1st to 10th	Night	16% 8% 2 4 2 3 3 2 4 5% 50%	4919
	11th to 20th	Night	10% 6% 2 5% 3 3 4 3 5% 8% 50%	4980
	21st to end	Night	17% 12% 5% 11% 5% 5% 4 3 5% 6% 29%	5467
April	1st to 10th	Night	14% 7% 2 7% 5% 3 3 3 5% 7% 44%	2016
	11th to 20th	Night	14% 8% 3 7% 4 4 3 3 5% 6% 42%	1975
	21st to end	Night	18% 8% 2 7% 4 3 4 3 5% 7% 40%	1852
May	1st to 10th	Night	15% 7% 2 5% 4 4 4 3 5% 6% 46%	4053
	11th to 20th	Night	13% 6% 2 4 3 3 3 3 5% 7% 50%	3734
	21st to end	Night	17% 7% 2 6% 4 3 4 4 5% 7% 41%	3942
June	1st to 10th	Night	7% 4 2 5% 5% 5% 3 4 5% 8% 52%	1600
	11th to 20th	Night	7% 5% 2 5% 4 4 4 4 7% 9% 50%	1600
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 8% 51%	1600
July	1st to 10th	Night	7% 4 2 5% 4 4 5% 4 7% 10% 49%	3618
	11th to 20th	Night	6% 4 2 5% 3 3 4 3 6% 9% 54%	3709
	21st to end	Night	8% 4 2 6% 4 4 5% 5% 8% 9% 45%	4449
August	1st to 10th	Night	5% 4 2 5% 3 4 3 3 6% 9% 55%	2926
	11th to 20th	Night	10% 5% 2 5% 3 4 3 3 4 6% 54%	2888
	21st to end	Night	8% 5% 2 4 3 3 3 2 5% 9% 56%	3507
September	1st to 10th	Night	9% 5% 2 5% 3 3 3 3 4 6% 59%	2000
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 5% 7% 54%	2070
	21st to end	Night	10% 4 2 4 2 3 3 3 5% 6% 58%	2250
October	1st to 10th	Night	13% 6% 2 6% 3 2 2 3 4 7% 52%	2400
	11th to 20th	Night	13% 6% 2 5% 3 4 4 2 4 6% 49%	2400
	21st to end	Night	16% 7% 2 6% 3 3 3 3 4 5% 47%	2640
November	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 4 7% 53%	2481
	11th to 20th	Night	13% 8% 2 7% 4 4 3 3 5% 7% 45%	2800
	21st to end	Night	15% 11% 3 6% 4 4 3 3 4 6% 42%	2800
December	1st to 10th	Night	6% 9% 3 7% 5% 4 4 3 5% 7% 47%	4580
	11th to 20th	Night	11% 10% 4 11% 6% 5% 5% 3 4 6% 36%	5199
	21st to end	Night	20% 17% 8% 12% 4 4 3 3 3 4 21%	6996

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	59% 6% 11% 16% 6%	3642
	11th to 20th	Day	51% 4 10% 20% 13% 2	4080
	21st to end	Day	56% 6% 12% 20% 6%	4488
February	1st to 10th	Day	55% 5% 13% 18% 9% 1	1800
	11th to 20th	Day	49% 6% 13% 20% 11% 2	1763
	21st to end	Day	48% 5% 13% 21% 11% 2	1600
March	1st to 10th	Day	43% 4 9% 25% 17% 1	4936
	11th to 20th	Day	35% 5% 10% 27% 20% 2	4980
	21st to end	Day	57% 6% 17% 15% 4 1	5464
April	1st to 10th	Day	47% 7% 11% 26% 9% 1	2383
	11th to 20th	Day	47% 7% 11% 21% 12% 2	2374
	21st to end	Day	48% 6% 13% 21% 11% 1	2545
May	1st to 10th	Day	42% 8% 12% 21% 16% 1	5900
	11th to 20th	Day	37% 6% 10% 28% 16% 3	6184
	21st to end	Day	43% 7% 12% 23% 14% 1	6949
June	1st to 10th	Day	35% 8% 17% 23% 14% 2	2800
	11th to 20th	Day	32% 7% 16% 24% 19% 2	2800
	21st to end	Day	37% 8% 14% 25% 14% 2	2800
July	1st to 10th	Day	37% 5% 15% 31% 11% 1	6291
	11th to 20th	Day	34% 5% 14% 29% 17% 1	6176
	21st to end	Day	34% 7% 20% 26% 12% 1	6240
August	1st to 10th	Day	33% 7% 16% 27% 16% 1	4220
	11th to 20th	Day	41% 6% 13% 26% 13% 1	4210
	21st to end	Day	33% 5% 16% 27% 16% 2	4392
September	1st to 10th	Day	30% 5% 13% 27% 21% 4	2400
	11th to 20th	Day	32% 6% 15% 30% 17% 1	2325
	21st to end	Day	32% 6% 11% 31% 20% 1	2129
October	1st to 10th	Day	22% 2 7% 27% 39% 2	3260
	11th to 20th	Day	28% 3 8% 32% 24% 5%	3240
	21st to end	Day	38% 4 10% 28% 17% 3	3538
November	1st to 10th	Day	35% 6% 18% 22% 18% 2	1855
	11th to 20th	Day	43% 6% 13% 21% 17% 1	1600
	21st to end	Day	46% 4 16% 23% 10% 1	1600
December	1st to 10th	Day	34% 4 17% 34% 9% 1	2610
	11th to 20th	Day	55% 5% 14% 17% 8%	3005
	21st to end	Day	68% 5% 10% 13% 4 1	3982
January	1st to 10th	Night	59% 5% 14% 14% 8% 1	6320
	11th to 20th	Night	51% 4 13% 15% 15% 2	5900
	21st to end	Night	53% 5% 11% 17% 13% 1	6490
February	1st to 10th	Night	51% 4 13% 20% 10% 1	2600
	11th to 20th	Night	45% 6% 11% 24% 12% 2	2534
	21st to end	Night	44% 4 11% 21% 17% 3	2047
March	1st to 10th	Night	37% 4 8% 30% 19% 2	4919
	11th to 20th	Night	32% 5% 8% 33% 18% 4	4980
	21st to end	Night	55% 8% 15% 15% 5% 2	5467
April	1st to 10th	Night	39% 6% 11% 26% 15% 2	2016
	11th to 20th	Night	42% 6% 11% 23% 16% 3	1975
	21st to end	Night	43% 6% 15% 21% 13% 2	1852
May	1st to 10th	Night	37% 6% 10% 28% 18% 1	4080
	11th to 20th	Night	33% 6% 12% 27% 17% 5%	3735
	21st to end	Night	42% 7% 11% 22% 16% 2	3950
June	1st to 10th	Night	30% 7% 16% 28% 17% 3	1600
	11th to 20th	Night	29% 7% 15% 23% 22% 5%	1600
	21st to end	Night	30% 7% 14% 26% 20% 4	1600
July	1st to 10th	Night	31% 5% 15% 32% 15% 2	3580
	11th to 20th	Night	27% 5% 16% 31% 19% 2	3664
	21st to end	Night	32% 8% 20% 26% 13% 1	4320
August	1st to 10th	Night	26% 6% 17% 33% 16% 1	2916
	11th to 20th	Night	31% 6% 15% 31% 16% 1	2915
	21st to end	Night	27% 6% 17% 29% 17% 5%	3507
September	1st to 10th	Night	27% 6% 11% 27% 25% 4	2000
	11th to 20th	Night	29% 5% 13% 32% 20% 2	2070
	21st to end	Night	27% 5% 10% 31% 26% 3	2250
October	1st to 10th	Night	22% 3 6% 23% 43% 3	3920
	11th to 20th	Night	28% 4 8% 27% 27% 7%	3899
	21st to end	Night	41% 4 10% 25% 19% 2	4252
November	1st to 10th	Night	32% 5% 16% 25% 18% 4	2481
	11th to 20th	Night	39% 5% 13% 26% 14% 2	2800
	21st to end	Night	44% 4 11% 26% 13% 1	2800
December	1st to 10th	Night	37% 4 12% 37% 9% 1	4580
	11th to 20th	Night	50% 5% 14% 24% 7%	5201
	21st to end	Night	67% 5% 9% 14% 5%	6996

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	18% 15% 32% 25% 9% 2	300
	11th to 20th	Day	18% 15% 42% 20% 5%	300
	21st to end	Day	19% 12% 40% 25% 4	330
February	1st to 10th	Day	19% 18% 37% 22% 3 1	300
	11th to 20th	Day	19% 18% 38% 19% 5% 1	300
	21st to end	Day	24% 12% 42% 19% 3	249
March	1st to 10th	Day	21% 14% 43% 16% 5%	300
	11th to 20th	Day	24% 12% 35% 21% 7%	300
	21st to end	Day	31% 19% 29% 17% 3	330
April	1st to 10th	Day	25% 14% 34% 20% 6%	483
	11th to 20th	Day	23% 16% 32% 20% 9%	492
	21st to end	Day	25% 14% 30% 23% 7% 1	645
May	1st to 10th	Day	19% 13% 34% 22% 11% 1	703
	11th to 20th	Day	20% 14% 27% 24% 12% 2	725
	21st to end	Day	17% 9% 27% 29% 14% 4	789
June	1st to 10th	Day	8% 7% 24% 33% 23% 5%	730
	11th to 20th	Day	11% 5% 30% 34% 16% 4	730
	21st to end	Day	11% 8% 34% 31% 14% 3	730
July	1st to 10th	Day	7% 4 19% 31% 28% 10%	721
	11th to 20th	Day	6% 4 25% 36% 22% 6%	718
	21st to end	Day	8% 2 19% 41% 25% 5%	794
August	1st to 10th	Day	9% 3 24% 36% 24% 5%	726
	11th to 20th	Day	13% 3 17% 36% 27% 6%	715
	21st to end	Day	9% 3 21% 36% 24% 7%	638
September	1st to 10th	Day	13% 5% 23% 30% 22% 8%	530
	11th to 20th	Day	8% 4 23% 38% 22% 5%	455
	21st to end	Day	11% 8% 25% 33% 19% 3	330
October	1st to 10th	Day	17% 8% 31% 23% 17% 4	330
	11th to 20th	Day	17% 23% 34% 18% 7% 2	330
	21st to end	Day	20% 15% 36% 21% 6% 2	363
November	1st to 10th	Day	18% 11% 41% 21% 8% 2	306
	11th to 20th	Day	20% 19% 31% 20% 8% 1	300
	21st to end	Day	22% 13% 37% 23% 5%	300
December	1st to 10th	Day	11% 15% 44% 20% 9% 1	300
	11th to 20th	Day	15% 17% 38% 22% 7% 1	300
	21st to end	Day	25% 16% 38% 15% 5%	330
January	1st to 10th	Night	14% 11% 37% 29% 8%	1000
	11th to 20th	Night	18% 12% 34% 27% 7% 1	1000
	21st to end	Night	19% 11% 36% 29% 5%	1100
February	1st to 10th	Night	17% 13% 36% 29% 4	1000
	11th to 20th	Night	17% 12% 38% 28% 5%	979
	21st to end	Night	17% 13% 39% 26% 3 2	727
March	1st to 10th	Night	18% 13% 38% 24% 7% 1	600
	11th to 20th	Night	19% 8% 38% 27% 7% 1	600
	21st to end	Night	24% 14% 37% 20% 4 1	660
April	1st to 10th	Night	18% 12% 42% 25% 3	600
	11th to 20th	Night	18% 15% 36% 26% 5% 1	593
	21st to end	Night	21% 9% 37% 25% 8% 1	600
May	1st to 10th	Night	17% 8% 34% 32% 8% 1	600
	11th to 20th	Night	16% 9% 32% 31% 11% 1	591
	21st to end	Night	17% 6% 25% 36% 14%	650
June	1st to 10th	Night	7% 4 26% 46% 17% 1	600
	11th to 20th	Night	10% 4 27% 46% 13%	600
	21st to end	Night	9% 6% 31% 40% 14%	600
July	1st to 10th	Night	6% 2 14% 44% 32% 2	585
	11th to 20th	Night	5% 2 18% 48% 26% 1	582
	21st to end	Night	6% 2 16% 50% 24% 1	657
August	1st to 10th	Night	8% 2 18% 47% 23% 3	597
	11th to 20th	Night	7% 2 19% 44% 26% 2	594
	21st to end	Night	9% 3 17% 45% 25% 2	660
September	1st to 10th	Night	11% 5% 20% 39% 23% 2	600
	11th to 20th	Night	13% 2 21% 40% 22% 3	600
	21st to end	Night	11% 6% 25% 39% 18% 1	650
October	1st to 10th	Night	16% 7% 29% 32% 16% 1	800
	11th to 20th	Night	17% 11% 34% 31% 8%	800
	21st to end	Night	20% 12% 33% 28% 7%	880
November	1st to 10th	Night	14% 10% 38% 30% 9%	814
	11th to 20th	Night	17% 14% 39% 23% 6%	1000
	21st to end	Night	19% 12% 35% 27% 7%	1000
December	1st to 10th	Night	17% 12% 37% 28% 6%	1000
	11th to 20th	Night	20% 9% 36% 29% 7%	1000
	21st to end	Night	23% 12% 35% 26% 5%	1100

Page generated at 2025-10-31 01:02:37. Version ac07

Copyright © 2025 Attilla Danko.