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 2024-01-16.

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	13% 8% 3 6% 5% 3 5% 4 5% 7% 40%	74712
	Night	12% 8% 3 6% 5% 3 4 4 5% 7% 43%	75105
Transparency	Day	43% 7% 14% 22% 13% 2	74424
	Night	41% 6% 13% 24% 14% 2	74913
Seeing	Day	15% 9% 29% 28% 15% 4	14670
	Night	15% 9% 32% 32% 11% 1	24668

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	9% 12% 5% 11% 7% 5% 5% 5% 4 7% 31%	1527
	11th to 20th	Day	11% 12% 6% 11% 9% 4 5% 4 5% 6% 27%	1665
	21st to end	Day	14% 12% 6% 10% 7% 3 6% 5% 5% 6% 26%	1782
February	1st to 10th	Day	13% 13% 5% 9% 7% 4 5% 5% 3 6% 30%	1620
	11th to 20th	Day	13% 9% 4 8% 6% 4 4 4 5% 7% 37%	1574
	21st to end	Day	15% 10% 4 8% 8% 4 5% 4 4 6% 33%	1434
March	1st to 10th	Day	16% 10% 5% 7% 5% 3 4 4 4 7% 36%	1980
	11th to 20th	Day	14% 11% 5% 7% 7% 3 4 5% 5% 6% 33%	1980
	21st to end	Day	20% 11% 6% 7% 7% 3 4 3 5% 5% 29%	2178
April	1st to 10th	Day	17% 10% 4 6% 4 3 4 5% 5% 7% 36%	2144
	11th to 20th	Day	16% 9% 3 8% 5% 3 5% 4 5% 6% 36%	2134
	21st to end	Day	22% 7% 3 6% 5% 3 4 4 6% 6% 35%	2290
May	1st to 10th	Day	17% 8% 3 6% 6% 3 6% 5% 7% 7% 32%	2340
	11th to 20th	Day	18% 7% 3 6% 5% 3 5% 5% 5% 7% 36%	2424
	21st to end	Day	15% 8% 3 5% 6% 4 5% 5% 5% 8% 36%	2725
June	1st to 10th	Day	10% 5% 3 5% 6% 3 5% 5% 6% 9% 44%	2520
	11th to 20th	Day	9% 5% 2 4 5% 3 5% 5% 7% 11% 46%	2520
	21st to end	Day	9% 5% 3 5% 6% 4 6% 5% 6% 8% 43%	2520
July	1st to 10th	Day	7% 4 2 4 4 3 4 5% 6% 10% 50%	2520
	11th to 20th	Day	6% 3 2 5% 6% 3 6% 5% 6% 9% 50%	2481
	21st to end	Day	6% 4 2 5% 4 3 6% 5% 7% 10% 48%	2546
August	1st to 10th	Day	8% 5% 2 5% 6% 3 6% 6% 7% 10% 41%	2328
	11th to 20th	Day	10% 5% 3 5% 4 3 5% 5% 5% 9% 47%	2301
	21st to end	Day	9% 5% 2 5% 5% 4 4 4 4 6% 52%	2426
September	1st to 10th	Day	14% 5% 2 4 4 2 3 3 4 6% 54%	2160
	11th to 20th	Day	10% 4 2 4 4 3 4 5% 6% 8% 51%	2093
	21st to end	Day	11% 4 2 4 3 3 5% 4 5% 7% 51%	1917
October	1st to 10th	Day	14% 7% 2 6% 5% 3 3 3 4 6% 47%	1800
	11th to 20th	Day	16% 7% 3 5% 4 3 4 3 5% 5% 46%	1800
	21st to end	Day	15% 9% 3 7% 4 2 4 4 4 7% 42%	1980
November	1st to 10th	Day	11% 5% 2 4 5% 2 4 5% 6% 6% 49%	1742
	11th to 20th	Day	13% 8% 4 6% 6% 2 4 4 5% 8% 41%	1520
	21st to end	Day	15% 9% 4 4 5% 3 3 4 4 7% 40%	1520
December	1st to 10th	Day	11% 11% 4 8% 6% 3 5% 5% 5% 6% 36%	1520
	11th to 20th	Day	11% 10% 4 9% 6% 3 5% 5% 5% 7% 34%	1918
	21st to end	Day	21% 15% 8% 12% 6% 3 3 4 4 5% 20%	2783
January	1st to 10th	Night	9% 10% 4 8% 6% 4 5% 4 6% 7% 38%	2634
	11th to 20th	Night	12% 12% 6% 10% 8% 3 5% 4 5% 5% 29%	2406
	21st to end	Night	13% 13% 4 7% 6% 3 5% 4 5% 6% 33%	2574
February	1st to 10th	Night	12% 11% 5% 10% 7% 3 5% 3 5% 6% 33%	2340
	11th to 20th	Night	12% 10% 4 6% 6% 3 4 5% 5% 6% 40%	2273
	21st to end	Night	12% 9% 5% 8% 6% 3 4 3 3 6% 40%	1838
March	1st to 10th	Night	14% 10% 3 6% 4 2 4 3 3 6% 45%	1980
	11th to 20th	Night	15% 8% 3 7% 4 3 4 5% 4 7% 39%	1980
	21st to end	Night	20% 11% 5% 8% 6% 4 5% 4 5% 6% 27%	2178
April	1st to 10th	Night	14% 7% 3 6% 5% 2 3 4 4 7% 44%	1815
	11th to 20th	Night	15% 8% 4 6% 5% 3 4 3 5% 6% 41%	1775
	21st to end	Night	18% 7% 3 6% 4 2 4 4 5% 7% 41%	1668
May	1st to 10th	Night	16% 7% 2 4 5% 3 5% 5% 6% 9% 39%	1620
	11th to 20th	Night	16% 6% 2 4 4 2 4 5% 6% 9% 42%	1470
	21st to end	Night	13% 6% 2 4 6% 3 4 5% 6% 8% 42%	1551
June	1st to 10th	Night	7% 4 2 4 5% 3 4 4 5% 9% 52%	1440
	11th to 20th	Night	7% 5% 2 4 5% 2 4 4 6% 9% 51%	1440
	21st to end	Night	8% 4 2 4 5% 3 4 5% 6% 8% 51%	1440
July	1st to 10th	Night	6% 2 2 2 3 2 4 4 6% 10% 58%	1440
	11th to 20th	Night	5% 2 1 2 3 2 3 4 6% 10% 62%	1476
	21st to end	Night	4 3 1 3 4 3 4 6% 7% 9% 56%	1772
August	1st to 10th	Night	7% 4 2 6% 5% 3 4 5% 6% 9% 50%	1611
	11th to 20th	Night	7% 3 2 4 4 2 4 4 5% 7% 58%	1600
	21st to end	Night	8% 4 2 4 3 2 3 4 6% 8% 58%	1930
September	1st to 10th	Night	9% 5% 2 4 4 2 4 4 4 6% 57%	1800
	11th to 20th	Night	11% 5% 2 3 3 2 3 4 5% 7% 56%	1862
	21st to end	Night	10% 4 2 4 3 2 3 3 5% 6% 58%	2024
October	1st to 10th	Night	13% 6% 2 5% 4 2 3 3 4 7% 51%	2160
	11th to 20th	Night	14% 6% 2 5% 4 3 4 3 4 6% 48%	2160
	21st to end	Night	16% 7% 2 5% 4 2 3 4 4 6% 47%	2376
November	1st to 10th	Night	10% 5% 2 4 4 2 4 4 4 7% 54%	2329
	11th to 20th	Night	13% 7% 3 6% 5% 2 4 4 4 7% 46%	2660
	21st to end	Night	15% 9% 3 5% 5% 3 4 3 4 6% 44%	2660
December	1st to 10th	Night	11% 10% 4 8% 7% 4 5% 4 5% 6% 37%	2660
	11th to 20th	Night	11% 10% 3 8% 7% 3 5% 4 4 6% 39%	3279
	21st to end	Night	19% 17% 8% 11% 5% 3 4 4 4 4 23%	4884

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	52% 7% 13% 18% 10% 1	1528
	11th to 20th	Day	57% 6% 13% 17% 6%	1665
	21st to end	Day	58% 6% 14% 15% 6% 1	1782
February	1st to 10th	Day	55% 5% 13% 18% 8% 1	1620
	11th to 20th	Day	49% 6% 14% 21% 9% 2	1583
	21st to end	Day	52% 5% 13% 19% 10% 2	1434
March	1st to 10th	Day	50% 6% 14% 21% 9% 1	1980
	11th to 20th	Day	51% 5% 12% 20% 10% 1	1980
	21st to end	Day	57% 6% 12% 16% 7% 2	2178
April	1st to 10th	Day	48% 7% 11% 24% 9% 1	2144
	11th to 20th	Day	48% 7% 11% 22% 11% 1	2134
	21st to end	Day	48% 6% 12% 21% 11% 1	2290
May	1st to 10th	Day	49% 8% 14% 18% 10% 1	2340
	11th to 20th	Day	47% 7% 12% 22% 11% 1	2428
	21st to end	Day	46% 8% 14% 18% 12% 2	2725
June	1st to 10th	Day	35% 8% 17% 22% 15% 2	2520
	11th to 20th	Day	31% 8% 16% 24% 20% 2	2520
	21st to end	Day	37% 9% 14% 24% 14% 2	2520
July	1st to 10th	Day	29% 8% 16% 30% 14% 3	2451
	11th to 20th	Day	29% 9% 16% 26% 17% 3	2406
	21st to end	Day	28% 9% 16% 29% 16% 1	2405
August	1st to 10th	Day	35% 11% 17% 23% 13% 2	2314
	11th to 20th	Day	33% 7% 16% 29% 14% 2	2301
	21st to end	Day	32% 6% 11% 27% 19% 4	2426
September	1st to 10th	Day	32% 5% 13% 26% 20% 4	2160
	11th to 20th	Day	30% 7% 15% 30% 18% 1	2093
	21st to end	Day	32% 6% 12% 31% 19% 1	1917
October	1st to 10th	Day	38% 4 12% 26% 17% 2	1800
	11th to 20th	Day	41% 5% 8% 25% 18% 3	1800
	21st to end	Day	43% 5% 11% 23% 15% 2	1980
November	1st to 10th	Day	33% 6% 17% 22% 19% 2	1742
	11th to 20th	Day	42% 6% 13% 21% 17% 1	1520
	21st to end	Day	45% 5% 15% 23% 11% 1	1520
December	1st to 10th	Day	48% 6% 16% 19% 10% 1	1520
	11th to 20th	Day	49% 6% 18% 21% 7% 1	1915
	21st to end	Day	66% 6% 10% 13% 4 1	2783
January	1st to 10th	Night	45% 4 15% 20% 14%	2634
	11th to 20th	Night	56% 5% 15% 18% 6%	2406
	21st to end	Night	51% 6% 14% 17% 10% 1	2574
February	1st to 10th	Night	53% 4 12% 20% 10% 1	2340
	11th to 20th	Night	45% 6% 12% 24% 12% 2	2274
	21st to end	Night	47% 4 11% 19% 16% 2	1838
March	1st to 10th	Night	41% 5% 13% 28% 11% 1	1980
	11th to 20th	Night	44% 8% 11% 22% 14% 2	1980
	21st to end	Night	57% 6% 13% 15% 7% 1	2178
April	1st to 10th	Night	40% 6% 11% 25% 16% 2	1815
	11th to 20th	Night	44% 6% 11% 23% 15% 3	1775
	21st to end	Night	43% 6% 15% 21% 14% 2	1668
May	1st to 10th	Night	41% 9% 15% 20% 13% 1	1620
	11th to 20th	Night	39% 7% 15% 25% 12% 1	1471
	21st to end	Night	40% 8% 13% 23% 12% 4	1552
June	1st to 10th	Night	29% 7% 16% 28% 18% 3	1440
	11th to 20th	Night	28% 7% 16% 22% 22% 5%	1440
	21st to end	Night	29% 8% 15% 27% 19% 3	1440
July	1st to 10th	Night	21% 7% 19% 34% 17% 3	1400
	11th to 20th	Night	18% 6% 18% 36% 18% 4	1428
	21st to end	Night	20% 9% 19% 31% 18% 3	1673
August	1st to 10th	Night	30% 9% 16% 28% 15% 2	1601
	11th to 20th	Night	26% 8% 13% 32% 18% 3	1600
	21st to end	Night	25% 7% 12% 27% 21% 7%	1930
September	1st to 10th	Night	29% 6% 11% 25% 25% 4	1800
	11th to 20th	Night	28% 5% 12% 33% 20% 2	1862
	21st to end	Night	27% 5% 10% 32% 24% 2	2024
October	1st to 10th	Night	34% 6% 10% 26% 21% 3	2160
	11th to 20th	Night	37% 6% 10% 23% 20% 5%	2160
	21st to end	Night	40% 6% 12% 22% 19% 2	2376
November	1st to 10th	Night	31% 5% 16% 25% 19% 4	2329
	11th to 20th	Night	39% 6% 13% 26% 14% 2	2660
	21st to end	Night	44% 4 11% 26% 14% 1	2660
December	1st to 10th	Night	48% 5% 13% 24% 10% 1	2660
	11th to 20th	Night	45% 6% 13% 28% 7% 1	3281
	21st to end	Night	65% 6% 8% 14% 6%	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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	19% 14% 31% 26% 9% 2	270
	11th to 20th	Day	18% 14% 41% 21% 5%	255
	21st to end	Day	20% 11% 38% 26% 4	264
February	1st to 10th	Day	20% 18% 38% 21% 3 1	240
	11th to 20th	Day	20% 17% 39% 19% 4 1	240
	21st to end	Day	26% 11% 44% 16% 3 1	198
March	1st to 10th	Day	19% 15% 45% 15% 6%	240
	11th to 20th	Day	26% 9% 35% 21% 8%	240
	21st to end	Day	34% 19% 26% 17% 3	264
April	1st to 10th	Day	24% 14% 35% 21% 6%	404
	11th to 20th	Day	21% 15% 31% 22% 10%	412
	21st to end	Day	24% 14% 29% 24% 8% 2	550
May	1st to 10th	Day	21% 12% 35% 21% 10% 1	603
	11th to 20th	Day	20% 14% 29% 23% 12% 2	625
	21st to end	Day	17% 8% 24% 31% 15% 4	679
June	1st to 10th	Day	8% 6% 23% 33% 25% 6%	630
	11th to 20th	Day	10% 4 28% 35% 17% 5%	630
	21st to end	Day	10% 8% 32% 31% 16% 3	630
July	1st to 10th	Day	7% 4 16% 31% 31% 11%	621
	11th to 20th	Day	5% 4 24% 37% 23% 7%	618
	21st to end	Day	7% 2 19% 41% 26% 5%	684
August	1st to 10th	Day	9% 2 21% 36% 26% 6%	626
	11th to 20th	Day	13% 2 15% 37% 27% 6%	615
	21st to end	Day	9% 3 20% 36% 24% 7%	545
September	1st to 10th	Day	15% 4 22% 31% 20% 7%	450
	11th to 20th	Day	8% 3 25% 36% 22% 6%	383
	21st to end	Day	12% 9% 27% 33% 17% 2	270
October	1st to 10th	Day	19% 7% 29% 25% 15% 4	270
	11th to 20th	Day	18% 22% 33% 18% 8% 1	270
	21st to end	Day	20% 16% 32% 23% 7% 3	297
November	1st to 10th	Day	15% 10% 43% 20% 9% 3	270
	11th to 20th	Day	18% 19% 33% 21% 8% 1	270
	21st to end	Day	22% 11% 37% 23% 6%	270
December	1st to 10th	Day	11% 13% 43% 21% 10% 1	270
	11th to 20th	Day	15% 14% 38% 24% 8% 1	270
	21st to end	Day	25% 16% 40% 15% 4	297
January	1st to 10th	Night	14% 11% 37% 29% 9%	950
	11th to 20th	Night	18% 12% 34% 28% 8% 1	926
	21st to end	Night	19% 11% 36% 29% 5%	990
February	1st to 10th	Night	18% 12% 36% 29% 4	900
	11th to 20th	Night	17% 10% 38% 29% 6%	879
	21st to end	Night	18% 13% 38% 25% 3 2	654
March	1st to 10th	Night	18% 13% 37% 24% 7% 1	540
	11th to 20th	Night	19% 7% 36% 28% 8% 1	540
	21st to end	Night	25% 13% 35% 21% 5% 1	594
April	1st to 10th	Night	17% 12% 42% 26% 3	540
	11th to 20th	Night	18% 15% 35% 27% 5% 1	533
	21st to end	Night	20% 9% 37% 26% 8% 1	540
May	1st to 10th	Night	18% 8% 34% 31% 8% 1	540
	11th to 20th	Night	17% 8% 33% 31% 10% 1	531
	21st to end	Night	17% 6% 25% 37% 16%	584
June	1st to 10th	Night	8% 3 24% 47% 17% 1	540
	11th to 20th	Night	10% 3 27% 46% 14%	540
	21st to end	Night	8% 5% 32% 41% 15%	540
July	1st to 10th	Night	6% 1 14% 44% 34% 2	525
	11th to 20th	Night	4 2 18% 49% 25% 1	522
	21st to end	Night	4 1 16% 52% 25% 1	591
August	1st to 10th	Night	8% 2 17% 47% 24% 3	537
	11th to 20th	Night	7% 2 18% 44% 27% 2	534
	21st to end	Night	9% 3 17% 44% 25% 2	594
September	1st to 10th	Night	12% 4 21% 38% 23% 2	540
	11th to 20th	Night	13% 2 21% 39% 22% 3	540
	21st to end	Night	11% 7% 27% 38% 17% 1	584
October	1st to 10th	Night	16% 6% 31% 31% 15% 1	720
	11th to 20th	Night	18% 11% 32% 32% 8%	720
	21st to end	Night	20% 11% 33% 28% 8%	792
November	1st to 10th	Night	13% 10% 39% 30% 9%	763
	11th to 20th	Night	17% 14% 39% 23% 6%	950
	21st to end	Night	19% 11% 35% 28% 7%	950
December	1st to 10th	Night	17% 12% 37% 28% 6%	950
	11th to 20th	Night	19% 9% 36% 29% 7%	950
	21st to end	Night	22% 12% 35% 26% 4	1045

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