Van Meter State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Van Meter State Park clear sky chart from 2005-11-06 to 2025-10-04.

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% 7% 3 7% 4 4 4 3 5% 7% 44%	126436
	Night	12% 7% 3 7% 4 4 4 3 5% 7% 45%	123195
Transparency	Day	38% 6% 12% 25% 16% 2	130042
	Night	38% 5% 11% 25% 18% 3	127666
Seeing	Day	14% 9% 26% 28% 18% 5%	16974
	Night	15% 8% 30% 33% 13% 1	26722

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	15% 11% 4 10% 5% 5% 4 3 5% 6% 33%	3907
	11th to 20th	Day	8% 9% 4 9% 5% 7% 6% 3 4 5% 39%	4080
	21st to end	Day	15% 14% 4 10% 5% 4 4 3 3 4 35%	4488
February	1st to 10th	Day	15% 11% 4 9% 5% 4 4 3 5% 7% 33%	1800
	11th to 20th	Day	14% 10% 4 7% 5% 3 4 3 5% 5% 39%	1754
	21st to end	Day	12% 9% 4 6% 5% 3 3 3 6% 6% 43%	1670
March	1st to 10th	Day	15% 9% 3 5% 3 2 2 2 3 4 51%	4936
	11th to 20th	Day	10% 6% 2 6% 3 3 4 3 4 7% 52%	4980
	21st to end	Day	15% 11% 3 8% 5% 4 4 4 5% 8% 32%	5462
April	1st to 10th	Day	15% 8% 2 6% 4 3 4 3 6% 6% 42%	2385
	11th to 20th	Day	15% 9% 3 7% 4 3 4 4 5% 6% 40%	2374
	21st to end	Day	20% 8% 3 7% 5% 5% 5% 3 5% 6% 33%	2434
May	1st to 10th	Day	13% 7% 2 6% 4 4 5% 4 6% 8% 39%	5862
	11th to 20th	Day	14% 6% 3 6% 5% 3 4 3 5% 7% 43%	5967
	21st to end	Day	17% 7% 2 6% 4 4 4 4 5% 6% 41%	6935
June	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 11% 47%	2800
	11th to 20th	Day	8% 5% 2 6% 4 4 4 4 7% 9% 46%	2800
	21st to end	Day	6% 5% 2 6% 4 4 4 4 7% 9% 48%	2800
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 46%	6360
	11th to 20th	Day	8% 5% 2 7% 4 4 5% 4 6% 9% 45%	5932
	21st to end	Day	7% 5% 2 6% 5% 4 5% 4 7% 11% 42%	6422
August	1st to 10th	Day	5% 3 2 4 3 4 5% 4 7% 11% 51%	4234
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 8% 47%	4143
	21st to end	Day	5% 5% 2 4 4 3 5% 4 7% 8% 54%	4312
September	1st to 10th	Day	11% 4 2 5% 3 3 4 4 5% 7% 53%	2400
	11th to 20th	Day	10% 4 2 5% 4 4 4 3 6% 8% 51%	2346
	21st to end	Day	9% 5% 2 5% 4 4 3 4 4 6% 55%	2115
October	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 6% 54%	1930
	11th to 20th	Day	13% 7% 1 5% 3 3 3 3 4 5% 54%	1900
	21st to end	Day	17% 7% 3 6% 3 3 3 3 4 6% 45%	2090
November	1st to 10th	Day	11% 7% 2 5% 3 3 3 3 4 7% 52%	1928
	11th to 20th	Day	15% 7% 2 6% 4 3 3 2 5% 6% 48%	1690
	21st to end	Day	17% 10% 3 7% 3 3 2 3 4 5% 43%	1600
December	1st to 10th	Day	6% 7% 3 7% 4 3 3 3 4 6% 53%	2610
	11th to 20th	Day	12% 7% 4 9% 4 3 3 3 4 5% 45%	3008
	21st to end	Day	18% 19% 8% 11% 5% 4 4 2 4 4 22%	3982
January	1st to 10th	Night	12% 11% 5% 14% 5% 5% 4 3 4 4 33%	6054
	11th to 20th	Night	11% 9% 4 10% 5% 7% 4 4 5% 5% 37%	5900
	21st to end	Night	14% 11% 5% 10% 5% 4 4 3 4 4 37%	6490
February	1st to 10th	Night	14% 10% 4 8% 6% 4 4 3 5% 5% 36%	2600
	11th to 20th	Night	14% 9% 4 7% 5% 4 4 3 5% 6% 41%	2533
	21st to end	Night	13% 8% 4 6% 3 3 2 4 5% 7% 45%	1973
March	1st to 10th	Night	17% 10% 3 5% 3 3 3 2 4 4 46%	4919
	11th to 20th	Night	10% 7% 2 4 3 3 3 3 4 7% 54%	4980
	21st to end	Night	15% 9% 4 8% 5% 4 4 4 6% 7% 33%	5467
April	1st to 10th	Night	12% 7% 2 5% 4 3 4 3 6% 6% 49%	2014
	11th to 20th	Night	14% 7% 2 6% 5% 4 3 3 4 7% 46%	1975
	21st to end	Night	17% 9% 2 7% 4 4 3 3 5% 6% 40%	1962
May	1st to 10th	Night	15% 7% 3 7% 4 4 4 4 5% 8% 39%	4053
	11th to 20th	Night	13% 6% 2 6% 3 3 4 3 6% 8% 46%	3944
	21st to end	Night	14% 6% 2 6% 4 4 4 3 5% 6% 45%	3942
June	1st to 10th	Night	6% 4 1 4 4 3 4 4 5% 10% 54%	1600
	11th to 20th	Night	6% 3 3 4 5% 5% 4 3 6% 11% 50%	1600
	21st to end	Night	4 3 1 4 4 3 4 5% 7% 9% 56%	1600
July	1st to 10th	Night	9% 5% 2 6% 4 3 4 3 6% 9% 49%	3618
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 4 7% 9% 48%	4026
	21st to end	Night	6% 4 2 6% 4 5% 5% 4 8% 12% 44%	4449
August	1st to 10th	Night	3 3 1 3 3 3 4 4 6% 11% 60%	2926
	11th to 20th	Night	11% 6% 2 5% 3 3 3 2 5% 8% 52%	2915
	21st to end	Night	4 3 1 5% 3 4 5% 4 6% 8% 57%	3586
September	1st to 10th	Night	10% 4 2 5% 3 2 3 3 4 6% 57%	2000
	11th to 20th	Night	10% 4 2 4 3 3 4 4 6% 8% 53%	2050
	21st to end	Night	8% 4 2 5% 4 3 3 3 5% 7% 57%	2265
October	1st to 10th	Night	10% 4 2 4 3 3 4 3 4 5% 58%	2317
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 5% 55%	2280
	21st to end	Night	16% 8% 2 4 3 3 3 3 4 4 50%	2508
November	1st to 10th	Night	11% 5% 1 4 3 3 3 2 4 6% 58%	2367
	11th to 20th	Night	12% 7% 2 5% 4 3 3 2 5% 6% 51%	2707
	21st to end	Night	17% 8% 2 5% 3 3 3 3 3 5% 47%	2800
December	1st to 10th	Night	8% 6% 2 6% 4 3 4 3 5% 6% 52%	4580
	11th to 20th	Night	14% 8% 4 7% 4 4 4 2 5% 6% 43%	5199
	21st to end	Night	22% 15% 5% 9% 4 4 3 2 3 5% 26%	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	52% 5% 11% 21% 9% 2	3908
	11th to 20th	Day	48% 4 11% 20% 13% 4	4080
	21st to end	Day	54% 4 10% 14% 16% 2	4488
February	1st to 10th	Day	52% 5% 12% 21% 10% 1	1800
	11th to 20th	Day	46% 5% 11% 21% 14% 3	1763
	21st to end	Day	42% 5% 12% 23% 16% 2	1670
March	1st to 10th	Day	39% 3 7% 26% 22% 3	4936
	11th to 20th	Day	32% 5% 9% 24% 24% 5%	4980
	21st to end	Day	49% 7% 16% 22% 5%	5464
April	1st to 10th	Day	41% 6% 12% 26% 14% 1	2385
	11th to 20th	Day	44% 5% 12% 24% 13% 2	2374
	21st to end	Day	50% 6% 12% 21% 11%	2434
May	1st to 10th	Day	40% 8% 15% 23% 13% 1	5900
	11th to 20th	Day	40% 6% 13% 25% 13% 2	5971
	21st to end	Day	42% 6% 9% 27% 15% 1	6949
June	1st to 10th	Day	31% 8% 16% 30% 14% 1	2800
	11th to 20th	Day	33% 8% 13% 28% 16% 2	2800
	21st to end	Day	30% 7% 17% 28% 14% 4	2800
July	1st to 10th	Day	35% 6% 12% 27% 17% 2	6291
	11th to 20th	Day	34% 6% 16% 27% 15% 1	5862
	21st to end	Day	33% 8% 17% 32% 10% 1	6240
August	1st to 10th	Day	25% 7% 18% 32% 16% 1	4220
	11th to 20th	Day	34% 6% 14% 29% 15% 1	4182
	21st to end	Day	27% 6% 16% 33% 14% 5%	4311
September	1st to 10th	Day	30% 6% 13% 25% 20% 6%	2400
	11th to 20th	Day	31% 7% 11% 26% 22% 3	2346
	21st to end	Day	31% 5% 10% 28% 23% 3	2115
October	1st to 10th	Day	19% 3 6% 20% 41% 10%	3190
	11th to 20th	Day	22% 3 4 23% 40% 9%	3140
	21st to end	Day	36% 3 8% 24% 26% 2	3428
November	1st to 10th	Day	34% 4 13% 25% 20% 4	1928
	11th to 20th	Day	38% 4 10% 25% 21% 3	1690
	21st to end	Day	45% 3 9% 28% 15%	1600
December	1st to 10th	Day	33% 5% 16% 31% 16%	2610
	11th to 20th	Day	42% 4 14% 29% 10% 1	3005
	21st to end	Day	67% 4 11% 12% 5% 1	3982
January	1st to 10th	Night	55% 4 10% 21% 9% 1	6054
	11th to 20th	Night	48% 4 11% 20% 13% 3	5900
	21st to end	Night	51% 4 10% 17% 16% 3	6490
February	1st to 10th	Night	49% 5% 12% 20% 12% 3	2600
	11th to 20th	Night	44% 5% 11% 21% 17% 2	2534
	21st to end	Night	39% 4 11% 22% 19% 4	1973
March	1st to 10th	Night	43% 4 8% 21% 22% 3	4919
	11th to 20th	Night	31% 4 7% 26% 26% 6%	4980
	21st to end	Night	48% 6% 13% 23% 8% 2	5467
April	1st to 10th	Night	36% 6% 10% 26% 19% 4	2014
	11th to 20th	Night	39% 5% 9% 27% 16% 4	1975
	21st to end	Night	44% 6% 10% 23% 16% 1	1962
May	1st to 10th	Night	41% 8% 15% 22% 14% 1	4080
	11th to 20th	Night	36% 6% 12% 26% 15% 5%	3945
	21st to end	Night	38% 7% 10% 23% 21% 1	3950
June	1st to 10th	Night	26% 7% 15% 31% 17% 4	1600
	11th to 20th	Night	28% 8% 12% 26% 21% 5%	1600
	21st to end	Night	22% 7% 16% 31% 19% 5%	1600
July	1st to 10th	Night	31% 5% 12% 27% 22% 2	3580
	11th to 20th	Night	30% 7% 16% 29% 17% 2	3977
	21st to end	Night	30% 8% 18% 35% 9% 1	4320
August	1st to 10th	Night	18% 6% 20% 31% 23% 2	2916
	11th to 20th	Night	32% 5% 12% 29% 21% 1	2942
	21st to end	Night	23% 6% 15% 34% 17% 4	3586
September	1st to 10th	Night	28% 5% 11% 24% 25% 7%	2000
	11th to 20th	Night	30% 6% 10% 27% 23% 4	2050
	21st to end	Night	28% 5% 9% 27% 27% 4	2265
October	1st to 10th	Night	17% 3 6% 20% 45% 9%	3837
	11th to 20th	Night	23% 3 5% 23% 31% 14%	3779
	21st to end	Night	34% 4 8% 27% 26% 2	4120
November	1st to 10th	Night	29% 4 13% 26% 22% 5%	2367
	11th to 20th	Night	35% 3 9% 26% 23% 4	2707
	21st to end	Night	42% 4 9% 27% 16% 2	2800
December	1st to 10th	Night	33% 4 12% 35% 14% 1	4580
	11th to 20th	Night	42% 4 14% 25% 14% 1	5201
	21st to end	Night	62% 4 12% 15% 5% 1	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% 16% 35% 22% 8% 1	300
	11th to 20th	Day	28% 15% 37% 18% 2	300
	21st to end	Day	16% 15% 42% 22% 5%	330
February	1st to 10th	Day	24% 11% 44% 18% 3	300
	11th to 20th	Day	20% 18% 37% 17% 7%	300
	21st to end	Day	16% 18% 42% 17% 6%	249
March	1st to 10th	Day	17% 13% 46% 22% 3	300
	11th to 20th	Day	24% 15% 29% 27% 5%	300
	21st to end	Day	31% 20% 29% 16% 4	330
April	1st to 10th	Day	21% 16% 32% 23% 7% 1	485
	11th to 20th	Day	21% 15% 32% 25% 7% 1	492
	21st to end	Day	23% 11% 32% 24% 9% 1	534
May	1st to 10th	Day	15% 12% 34% 28% 10% 1	703
	11th to 20th	Day	20% 8% 27% 27% 13% 4	725
	21st to end	Day	17% 8% 25% 28% 18% 6%	789
June	1st to 10th	Day	8% 3 17% 35% 27% 10%	730
	11th to 20th	Day	10% 3 22% 36% 23% 7%	730
	21st to end	Day	6% 5% 30% 36% 19% 4	730
July	1st to 10th	Day	10% 3 13% 28% 32% 14%	721
	11th to 20th	Day	7% 2 19% 34% 28% 10%	718
	21st to end	Day	8% 3 13% 31% 34% 11%	794
August	1st to 10th	Day	7% 2 17% 37% 30% 8%	726
	11th to 20th	Day	9% 3 14% 34% 31% 9%	700
	21st to end	Day	9% 2 13% 29% 33% 15%	583
September	1st to 10th	Day	12% 2 14% 34% 29% 10%	530
	11th to 20th	Day	10% 3 12% 32% 32% 12%	476
	21st to end	Day	11% 5% 24% 28% 22% 9%	330
October	1st to 10th	Day	15% 5% 26% 28% 16% 10%	309
	11th to 20th	Day	11% 16% 37% 25% 10% 2	300
	21st to end	Day	25% 15% 28% 25% 6% 1	330
November	1st to 10th	Day	18% 8% 32% 28% 11% 3	300
	11th to 20th	Day	16% 17% 33% 22% 10% 2	300
	21st to end	Day	24% 13% 30% 25% 7%	300
December	1st to 10th	Day	11% 16% 38% 23% 10% 2	300
	11th to 20th	Day	16% 17% 36% 21% 9% 1	300
	21st to end	Day	24% 16% 39% 18% 3	330
January	1st to 10th	Night	15% 12% 39% 27% 7%	1000
	11th to 20th	Night	17% 13% 39% 25% 5% 1	1000
	21st to end	Night	17% 11% 39% 29% 4	1100
February	1st to 10th	Night	17% 12% 41% 26% 3	1000
	11th to 20th	Night	19% 12% 38% 27% 4	979
	21st to end	Night	19% 11% 44% 21% 4	653
March	1st to 10th	Night	19% 13% 39% 25% 4	600
	11th to 20th	Night	21% 9% 36% 27% 6% 1	600
	21st to end	Night	25% 11% 36% 24% 4	660
April	1st to 10th	Night	15% 13% 38% 30% 5%	600
	11th to 20th	Night	17% 11% 34% 30% 8%	593
	21st to end	Night	19% 9% 36% 29% 7%	600
May	1st to 10th	Night	16% 6% 32% 36% 9%	600
	11th to 20th	Night	17% 5% 27% 36% 15% 1	591
	21st to end	Night	13% 5% 26% 34% 19% 2	650
June	1st to 10th	Night	8% 2 18% 47% 22% 4	600
	11th to 20th	Night	7% 1 21% 48% 21% 2	600
	21st to end	Night	4 4 25% 46% 20% 1	600
July	1st to 10th	Night	10% 3 8% 41% 35% 3	585
	11th to 20th	Night	6% 2 15% 40% 35% 2	582
	21st to end	Night	7% 1 13% 41% 36% 2	657
August	1st to 10th	Night	6% 1 13% 47% 30% 2	597
	11th to 20th	Night	7% 2 12% 40% 35% 3	594
	21st to end	Night	7% 1 9% 42% 38% 3	660
September	1st to 10th	Night	12% 1 16% 41% 27% 4	600
	11th to 20th	Night	11% 2 15% 41% 27% 5%	600
	21st to end	Night	8% 5% 20% 39% 25% 3	665
October	1st to 10th	Night	12% 5% 25% 35% 20% 3	773
	11th to 20th	Night	16% 8% 33% 32% 10%	760
	21st to end	Night	20% 10% 33% 27% 9%	836
November	1st to 10th	Night	14% 9% 31% 36% 9%	780
	11th to 20th	Night	15% 11% 38% 28% 8%	907
	21st to end	Night	21% 11% 34% 28% 6%	1000
December	1st to 10th	Night	16% 10% 38% 30% 6% 1	1000
	11th to 20th	Night	20% 9% 35% 32% 5%	1000
	21st to end	Night	22% 13% 36% 27% 3	1100

Page generated at 2025-10-01 00:39:07. Version ac07

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