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 2024-11-06.

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 6% 7% 39%	101394
	Night	12% 8% 3 8% 4 4 4 3 5% 7% 42%	97753
Transparency	Day	41% 7% 13% 23% 14% 2	105034
	Night	40% 6% 13% 24% 16% 2	102253
Seeing	Day	15% 10% 29% 28% 15% 3	15846
	Night	15% 9% 32% 32% 11% 1	25679

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% 21% 7% 6% 5% 4 4 5% 21%	2537
	11th to 20th	Day	9% 14% 5% 12% 7% 6% 7% 4 8% 6% 23%	2850
	21st to end	Day	13% 16% 8% 17% 5% 4 4 3 4 5% 20%	3135
February	1st to 10th	Day	12% 14% 5% 11% 6% 4 5% 4 4 7% 30%	1710
	11th to 20th	Day	12% 10% 3 8% 5% 6% 4 3 5% 7% 37%	1664
	21st to end	Day	14% 10% 4 9% 6% 5% 4 3 4 6% 35%	1522
March	1st to 10th	Day	18% 9% 3 6% 4 4 3 2 4 5% 42%	3436
	11th to 20th	Day	11% 8% 3 7% 4 4 4 4 5% 6% 45%	3480
	21st to end	Day	23% 13% 6% 9% 5% 4 4 3 5% 5% 23%	3814
April	1st to 10th	Day	16% 11% 3 7% 3 4 4 4 5% 6% 36%	2264
	11th to 20th	Day	16% 9% 3 8% 4 5% 4 3 5% 6% 37%	2254
	21st to end	Day	22% 8% 2 7% 4 4 4 3 6% 6% 35%	2418
May	1st to 10th	Day	18% 8% 2 7% 5% 5% 6% 4 6% 7% 31%	4082
	11th to 20th	Day	15% 6% 3 6% 5% 5% 4 4 6% 7% 39%	4302
	21st to end	Day	13% 7% 2 5% 5% 4 4 3 5% 8% 42%	4824
June	1st to 10th	Day	9% 5% 3 6% 5% 4 4 4 6% 9% 44%	2660
	11th to 20th	Day	9% 5% 2 5% 5% 4 4 4 7% 11% 45%	2660
	21st to end	Day	9% 6% 2 6% 5% 6% 5% 4 7% 8% 43%	2660
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 7% 9% 38%	4440
	11th to 20th	Day	5% 3 2 4 4 4 4 3 6% 8% 57%	4359
	21st to end	Day	4 4 2 5% 5% 6% 6% 5% 8% 11% 44%	4465
August	1st to 10th	Day	8% 5% 2 5% 4 4 6% 4 6% 10% 46%	4104
	11th to 20th	Day	13% 8% 3 6% 4 4 4 4 6% 8% 40%	4041
	21st to end	Day	7% 5% 3 6% 5% 5% 5% 4 6% 7% 48%	4258
September	1st to 10th	Day	13% 5% 1 5% 3 2 3 2 4 6% 55%	2280
	11th to 20th	Day	10% 4 2 5% 3 4 4 4 6% 8% 50%	2209
	21st to end	Day	11% 4 2 4 3 4 4 4 5% 7% 52%	2023
October	1st to 10th	Day	13% 7% 2 6% 4 3 2 2 4 6% 50%	1900
	11th to 20th	Day	15% 7% 2 5% 3 4 3 3 4 5% 47%	1900
	21st to end	Day	14% 9% 3 7% 4 3 4 3 5% 7% 42%	2090
November	1st to 10th	Day	12% 6% 2 5% 4 3 4 4 6% 6% 48%	1792
	11th to 20th	Day	13% 8% 4 7% 5% 3 3 4 5% 7% 40%	1520
	21st to end	Day	15% 10% 3 5% 5% 4 3 3 5% 7% 40%	1520
December	1st to 10th	Day	11% 12% 4 9% 5% 5% 4 3 5% 6% 36%	1520
	11th to 20th	Day	11% 11% 4 9% 6% 5% 5% 4 6% 7% 34%	1918
	21st to end	Day	21% 15% 8% 13% 5% 4 3 4 4 5% 20%	2783
January	1st to 10th	Night	10% 12% 5% 20% 7% 5% 4 3 5% 5% 25%	4414
	11th to 20th	Night	10% 14% 6% 11% 6% 5% 7% 4 8% 6% 25%	4120
	21st to end	Night	13% 17% 6% 13% 5% 5% 4 3 4 6% 24%	4532
February	1st to 10th	Night	11% 12% 5% 10% 6% 4 5% 3 5% 6% 33%	2470
	11th to 20th	Night	11% 11% 3 7% 5% 4 4 4 5% 6% 40%	2403
	21st to end	Night	12% 9% 4 9% 5% 5% 4 3 3 5% 41%	1949
March	1st to 10th	Night	14% 9% 3 6% 3 3 3 2 4 5% 48%	3419
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 5% 7% 51%	3480
	21st to end	Night	20% 12% 5% 12% 5% 5% 4 3 5% 6% 23%	3817
April	1st to 10th	Night	14% 7% 2 7% 4 3 3 3 5% 7% 44%	1915
	11th to 20th	Night	15% 8% 3 7% 4 4 3 3 5% 6% 42%	1875
	21st to end	Night	18% 8% 2 6% 4 3 4 3 5% 7% 41%	1760
May	1st to 10th	Night	19% 7% 2 5% 4 5% 4 3 5% 7% 40%	2823
	11th to 20th	Night	13% 7% 2 5% 4 4 3 3 5% 7% 47%	2602
	21st to end	Night	13% 6% 2 5% 5% 4 4 4 6% 8% 44%	2743
June	1st to 10th	Night	8% 4 1 5% 4 5% 3 3 5% 8% 52%	1520
	11th to 20th	Night	7% 5% 2 5% 4 3 4 3 7% 9% 50%	1520
	21st to end	Night	8% 4 2 5% 4 4 4 4 6% 8% 50%	1520
July	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 7% 9% 47%	2530
	11th to 20th	Night	4 2 1 3 3 3 4 3 6% 9% 62%	2594
	21st to end	Night	5% 3 1 6% 4 4 4 6% 9% 9% 48%	3098
August	1st to 10th	Night	5% 4 2 5% 3 4 3 3 6% 9% 55%	2836
	11th to 20th	Night	10% 5% 2 5% 3 4 3 3 4 6% 54%	2798
	21st to end	Night	8% 5% 2 4 3 3 3 3 5% 9% 56%	3400
September	1st to 10th	Night	9% 5% 2 5% 3 3 3 3 4 6% 59%	1900
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 5% 7% 55%	1966
	21st to end	Night	10% 4 2 4 2 3 3 3 5% 6% 58%	2137
October	1st to 10th	Night	12% 6% 2 6% 3 2 2 3 4 7% 52%	2280
	11th to 20th	Night	14% 6% 2 5% 3 4 4 2 4 6% 50%	2280
	21st to end	Night	16% 7% 2 6% 3 3 3 3 4 5% 46%	2508
November	1st to 10th	Night	10% 5% 2 5% 3 4 4 3 4 7% 54%	2401
	11th to 20th	Night	13% 8% 2 7% 4 3 3 3 5% 7% 45%	2660
	21st to end	Night	15% 10% 2 5% 4 4 3 3 4 5% 43%	2660
December	1st to 10th	Night	11% 11% 3 9% 6% 5% 4 3 5% 6% 36%	2660
	11th to 20th	Night	11% 11% 3 9% 6% 4 4 3 4 6% 39%	3279
	21st to end	Night	19% 17% 8% 12% 4 4 3 3 3 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	62% 8% 11% 13% 6%	2538
	11th to 20th	Day	58% 5% 10% 21% 6%	2850
	21st to end	Day	66% 7% 10% 13% 4	3135
February	1st to 10th	Day	54% 5% 13% 18% 9% 1	1710
	11th to 20th	Day	47% 6% 14% 21% 10% 2	1673
	21st to end	Day	50% 5% 12% 20% 11% 2	1522
March	1st to 10th	Day	45% 5% 10% 23% 14% 2	3436
	11th to 20th	Day	38% 7% 13% 23% 16% 2	3480
	21st to end	Day	61% 8% 13% 13% 4 1	3814
April	1st to 10th	Day	47% 7% 11% 25% 9% 1	2264
	11th to 20th	Day	46% 7% 11% 21% 12% 2	2254
	21st to end	Day	48% 6% 12% 21% 12% 1	2418
May	1st to 10th	Day	46% 11% 14% 16% 12% 1	4120
	11th to 20th	Day	41% 9% 11% 27% 12% 1	4306
	21st to end	Day	38% 8% 13% 23% 17% 1	4837
June	1st to 10th	Day	35% 9% 17% 22% 15% 2	2660
	11th to 20th	Day	32% 7% 16% 23% 20% 2	2660
	21st to end	Day	37% 9% 14% 25% 14% 2	2660
July	1st to 10th	Day	41% 6% 15% 27% 9% 2	4371
	11th to 20th	Day	25% 6% 15% 33% 20% 2	4284
	21st to end	Day	29% 8% 20% 25% 16% 2	4325
August	1st to 10th	Day	33% 7% 16% 27% 16% 1	4090
	11th to 20th	Day	41% 6% 13% 26% 13% 1	4080
	21st to end	Day	34% 5% 16% 27% 16% 2	4257
September	1st to 10th	Day	31% 5% 13% 26% 21% 4	2280
	11th to 20th	Day	30% 6% 15% 30% 18% 1	2209
	21st to end	Day	32% 6% 11% 31% 19% 1	2023
October	1st to 10th	Day	22% 3 7% 26% 40% 2	3160
	11th to 20th	Day	27% 3 8% 32% 24% 5%	3140
	21st to end	Day	38% 4 10% 28% 17% 3	3428
November	1st to 10th	Day	34% 6% 17% 22% 18% 2	1792
	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	59% 6% 12% 14% 9%	4414
	11th to 20th	Night	56% 5% 13% 15% 10% 1	4120
	21st to end	Night	60% 6% 13% 14% 7% 1	4532
February	1st to 10th	Night	51% 5% 13% 21% 10% 1	2470
	11th to 20th	Night	44% 6% 11% 25% 12% 2	2404
	21st to end	Night	46% 4 11% 21% 16% 3	1949
March	1st to 10th	Night	38% 6% 10% 26% 18% 2	3419
	11th to 20th	Night	32% 7% 11% 32% 15% 4	3480
	21st to end	Night	59% 11% 16% 10% 4 1	3817
April	1st to 10th	Night	40% 6% 11% 26% 15% 2	1915
	11th to 20th	Night	43% 6% 10% 22% 16% 3	1875
	21st to end	Night	43% 6% 15% 21% 14% 2	1760
May	1st to 10th	Night	42% 8% 11% 21% 17% 1	2850
	11th to 20th	Night	36% 7% 12% 27% 15% 3	2603
	21st to end	Night	35% 9% 12% 22% 18% 3	2751
June	1st to 10th	Night	30% 7% 15% 27% 17% 3	1520
	11th to 20th	Night	28% 7% 15% 22% 22% 5%	1520
	21st to end	Night	30% 7% 14% 26% 19% 3	1520
July	1st to 10th	Night	32% 5% 16% 32% 13% 2	2490
	11th to 20th	Night	19% 5% 19% 34% 20% 2	2546
	21st to end	Night	27% 10% 20% 25% 17% 2	2999
August	1st to 10th	Night	26% 6% 17% 33% 17% 2	2826
	11th to 20th	Night	31% 6% 15% 31% 16% 2	2825
	21st to end	Night	27% 6% 17% 29% 16% 6%	3400
September	1st to 10th	Night	27% 6% 11% 27% 25% 4	1900
	11th to 20th	Night	28% 5% 12% 33% 20% 2	1966
	21st to end	Night	27% 5% 9% 32% 24% 3	2137
October	1st to 10th	Night	21% 4 6% 23% 44% 3	3800
	11th to 20th	Night	27% 4 8% 27% 27% 7%	3779
	21st to end	Night	41% 4 10% 25% 19% 2	4120
November	1st to 10th	Night	31% 5% 16% 25% 19% 4	2401
	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% 40% 22% 5%	270
	21st to end	Day	20% 11% 38% 26% 5%	297
February	1st to 10th	Day	19% 17% 38% 21% 3 1	270
	11th to 20th	Day	18% 16% 38% 21% 6% 1	270
	21st to end	Day	24% 12% 44% 17% 3	225
March	1st to 10th	Day	20% 14% 43% 17% 6%	270
	11th to 20th	Day	24% 11% 35% 21% 8%	270
	21st to end	Day	33% 19% 28% 17% 3	297
April	1st to 10th	Day	24% 14% 35% 20% 6%	444
	11th to 20th	Day	21% 16% 31% 22% 10%	452
	21st to end	Day	25% 13% 29% 23% 7% 2	598
May	1st to 10th	Day	21% 13% 35% 20% 10% 1	653
	11th to 20th	Day	20% 14% 28% 24% 12% 2	675
	21st to end	Day	17% 9% 26% 30% 14% 4	734
June	1st to 10th	Day	7% 7% 24% 33% 24% 5%	680
	11th to 20th	Day	11% 5% 30% 33% 17% 5%	680
	21st to end	Day	10% 8% 34% 31% 15% 3	680
July	1st to 10th	Day	7% 5% 18% 31% 29% 10%	671
	11th to 20th	Day	5% 4 25% 37% 23% 6%	668
	21st to end	Day	7% 2 19% 41% 26% 6%	739
August	1st to 10th	Day	9% 3 22% 36% 25% 5%	676
	11th to 20th	Day	13% 3 17% 36% 26% 6%	665
	21st to end	Day	9% 4 20% 37% 24% 7%	591
September	1st to 10th	Day	14% 4 22% 31% 21% 7%	490
	11th to 20th	Day	8% 4 23% 37% 22% 6%	419
	21st to end	Day	12% 9% 26% 34% 17% 2	300
October	1st to 10th	Day	18% 7% 30% 24% 16% 5%	300
	11th to 20th	Day	17% 22% 33% 19% 8% 2	300
	21st to end	Day	19% 16% 34% 22% 6% 2	330
November	1st to 10th	Day	17% 9% 43% 20% 8% 2	285
	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% 27% 8% 1	950
	21st to end	Night	19% 11% 36% 29% 5%	1045
February	1st to 10th	Night	17% 11% 37% 29% 5%	950
	11th to 20th	Night	17% 10% 38% 29% 5%	929
	21st to end	Night	18% 13% 39% 25% 3 2	693
March	1st to 10th	Night	18% 13% 38% 24% 7% 1	570
	11th to 20th	Night	19% 8% 38% 28% 7% 1	570
	21st to end	Night	25% 13% 36% 21% 5% 1	627
April	1st to 10th	Night	18% 12% 42% 26% 3	570
	11th to 20th	Night	18% 14% 36% 26% 5% 1	563
	21st to end	Night	20% 9% 37% 25% 8% 1	570
May	1st to 10th	Night	18% 9% 34% 31% 8% 1	570
	11th to 20th	Night	16% 8% 33% 32% 10% 1	561
	21st to end	Night	17% 6% 25% 37% 15%	617
June	1st to 10th	Night	8% 4 25% 46% 17% 1	570
	11th to 20th	Night	10% 4 28% 46% 13%	570
	21st to end	Night	8% 6% 31% 40% 14%	570
July	1st to 10th	Night	6% 2 14% 44% 32% 2	555
	11th to 20th	Night	4 2 18% 49% 26% 1	552
	21st to end	Night	4 2 16% 51% 25% 1	624
August	1st to 10th	Night	8% 2 18% 47% 23% 3	567
	11th to 20th	Night	7% 2 19% 44% 25% 2	564
	21st to end	Night	9% 3 17% 44% 25% 2	627
September	1st to 10th	Night	11% 4 20% 39% 23% 2	570
	11th to 20th	Night	12% 2 21% 40% 22% 3	570
	21st to end	Night	11% 6% 26% 39% 17% 1	617
October	1st to 10th	Night	16% 7% 29% 31% 16% 1	760
	11th to 20th	Night	17% 11% 33% 31% 8%	760
	21st to end	Night	20% 11% 33% 28% 7%	836
November	1st to 10th	Night	14% 9% 38% 30% 9%	787
	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

Page generated at 2024-11-03 12:19:06. Version ac07

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