Tallgrass Prairie National Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tallgrass Prairie National Preserve clear sky chart from 2005-11-06 to 2025-05-26.

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	10% 6% 2 6% 4 4 4 3 5% 7% 49%	114750
	Night	10% 6% 2 5% 3 3 4 3 5% 7% 52%	114759
Transparency	Day	34% 5% 11% 26% 20% 4	118455
	Night	32% 4 11% 26% 22% 5%	119183
Seeing	Day	14% 10% 30% 28% 15% 3	16316
	Night	13% 10% 34% 32% 11% 1	26288

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	14% 8% 3 9% 4 4 4 4 5% 7% 38%	4077
	11th to 20th	Day	7% 9% 4 9% 5% 7% 5% 3 4 5% 42%	4080
	21st to end	Day	9% 10% 4 8% 4 3 4 3 4 6% 46%	4488
February	1st to 10th	Day	11% 12% 3 7% 5% 4 3 3 3 7% 42%	1800
	11th to 20th	Day	8% 8% 3 8% 6% 5% 4 3 5% 6% 45%	1881
	21st to end	Day	9% 6% 3 6% 4 3 5% 4 6% 7% 48%	1650
March	1st to 10th	Day	9% 7% 2 5% 3 3 3 3 4 6% 55%	4889
	11th to 20th	Day	9% 6% 1 3 3 3 3 2 4 6% 59%	4980
	21st to end	Day	11% 7% 3 7% 5% 4 5% 3 6% 7% 42%	5462
April	1st to 10th	Day	12% 8% 2 5% 3 3 3 3 5% 6% 50%	2204
	11th to 20th	Day	13% 7% 3 7% 4 4 4 3 5% 7% 44%	2457
	21st to end	Day	18% 8% 2 6% 4 3 4 3 5% 6% 40%	2600
May	1st to 10th	Day	18% 10% 3 7% 4 4 3 3 4 5% 39%	4212
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 5% 6% 46%	4212
	21st to end	Day	13% 6% 3 6% 5% 4 4 3 6% 7% 42%	4543
June	1st to 10th	Day	5% 3 1 5% 4 4 5% 4 7% 9% 52%	2470
	11th to 20th	Day	8% 4 1 5% 5% 4 4 3 6% 8% 51%	2470
	21st to end	Day	6% 3 1 4 4 4 4 4 6% 8% 55%	2470
July	1st to 10th	Day	11% 6% 2 5% 5% 4 5% 4 6% 8% 44%	4120
	11th to 20th	Day	6% 2 1 4 4 4 5% 4 7% 10% 53%	4120
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 8% 10% 44%	4465
August	1st to 10th	Day	6% 5% 2 6% 4 4 4 3 5% 7% 53%	4104
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 5% 8% 49%	4041
	21st to end	Day	4 3 1 4 3 4 4 3 5% 8% 60%	4418
September	1st to 10th	Day	13% 4 2 4 3 3 4 3 5% 6% 54%	2125
	11th to 20th	Day	9% 5% 2 5% 3 4 4 4 5% 6% 54%	2090
	21st to end	Day	9% 5% 2 5% 4 3 4 3 5% 5% 55%	2090
October	1st to 10th	Day	11% 3 3 5% 3 3 4 3 4 7% 54%	1981
	11th to 20th	Day	10% 5% 1 4 2 2 2 2 4 5% 63%	1900
	21st to end	Day	13% 7% 2 5% 3 2 3 3 4 4 54%	2090
November	1st to 10th	Day	8% 5% 2 5% 3 3 3 3 4 7% 58%	1842
	11th to 20th	Day	10% 6% 1 4 3 3 3 3 4 6% 57%	1800
	21st to end	Day	13% 5% 2 5% 3 3 3 2 4 5% 56%	1800
December	1st to 10th	Day	6% 4 1 3 3 3 3 3 5% 6% 62%	2940
	11th to 20th	Day	9% 6% 3 6% 3 4 4 3 3 5% 56%	3391
	21st to end	Day	17% 11% 6% 12% 4 3 3 3 4 5% 30%	4488
January	1st to 10th	Night	13% 9% 3 10% 5% 4 4 3 4 6% 40%	5888
	11th to 20th	Night	6% 7% 3 6% 5% 5% 5% 3 4 6% 50%	5900
	21st to end	Night	13% 9% 3 6% 3 3 3 3 3 5% 49%	6490
February	1st to 10th	Night	10% 10% 3 7% 4 4 3 4 5% 6% 44%	2600
	11th to 20th	Night	10% 9% 2 6% 4 3 4 4 4 6% 47%	2423
	21st to end	Night	9% 6% 2 5% 4 3 4 4 5% 6% 52%	1980
March	1st to 10th	Night	11% 7% 2 4 2 3 3 2 4 5% 57%	4968
	11th to 20th	Night	6% 4 1 4 2 3 4 3 6% 7% 60%	4980
	21st to end	Night	12% 6% 2 6% 4 4 4 3 5% 7% 47%	5467
April	1st to 10th	Night	11% 7% 2 5% 4 3 3 3 4 7% 53%	2195
	11th to 20th	Night	11% 7% 2 5% 3 3 3 3 6% 5% 51%	1889
	21st to end	Night	15% 6% 3 6% 3 3 5% 3 5% 7% 45%	1800
May	1st to 10th	Night	16% 9% 2 4 3 3 3 3 4 7% 45%	2913
	11th to 20th	Night	14% 6% 2 5% 3 3 4 2 5% 8% 47%	2913
	21st to end	Night	11% 5% 1 4 3 3 3 3 5% 8% 54%	3140
June	1st to 10th	Night	6% 3 1 4 3 3 4 5% 6% 11% 54%	1710
	11th to 20th	Night	4 3 2 4 4 4 4 5% 7% 10% 53%	1710
	21st to end	Night	5% 3 1 5% 3 3 4 4 6% 7% 58%	1710
July	1st to 10th	Night	8% 5% 2 5% 4 4 4 3 6% 8% 51%	2850
	11th to 20th	Night	2 3 1 4 4 3 4 4 6% 10% 58%	2850
	21st to end	Night	7% 4 2 5% 5% 5% 5% 4 8% 10% 44%	3098
August	1st to 10th	Night	3 4 1 5% 4 4 5% 4 7% 9% 55%	2836
	11th to 20th	Night	9% 4 1 6% 4 4 4 4 6% 7% 51%	2798
	21st to end	Night	5% 2 1 3 3 3 3 3 4 8% 65%	3245
September	1st to 10th	Night	10% 3 1 4 3 3 2 3 5% 6% 60%	2051
	11th to 20th	Night	9% 4 2 4 3 3 4 3 6% 7% 56%	2090
	21st to end	Night	7% 4 2 4 3 3 3 3 3 7% 61%	2090
October	1st to 10th	Night	10% 4 2 5% 3 3 4 3 4 6% 55%	2178
	11th to 20th	Night	10% 4 2 4 3 3 2 2 4 5% 61%	2280
	21st to end	Night	13% 5% 2 4 3 3 3 2 4 5% 57%	2508
November	1st to 10th	Night	10% 4 1 4 2 3 2 2 4 5% 63%	2453
	11th to 20th	Night	8% 5% 1 4 3 2 3 2 5% 7% 59%	2600
	21st to end	Night	12% 6% 2 4 3 2 2 3 4 5% 57%	2600
December	1st to 10th	Night	5% 4 2 5% 3 3 4 3 4 5% 63%	4250
	11th to 20th	Night	10% 6% 2 5% 3 3 3 3 5% 6% 53%	4816
	21st to end	Night	17% 10% 4 10% 4 4 3 2 4 5% 37%	6490

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	45% 4 12% 23% 14% 2	4078
	11th to 20th	Day	44% 4 10% 20% 19% 3	4080
	21st to end	Day	41% 3 10% 24% 16% 5%	4488
February	1st to 10th	Day	44% 4 12% 25% 11% 4	1800
	11th to 20th	Day	41% 4 12% 25% 14% 4	1890
	21st to end	Day	35% 5% 10% 24% 20% 6%	1650
March	1st to 10th	Day	32% 3 7% 20% 26% 13%	4889
	11th to 20th	Day	27% 4 9% 21% 28% 12%	4980
	21st to end	Day	41% 5% 12% 32% 9% 2	5464
April	1st to 10th	Day	35% 5% 11% 24% 20% 4	2204
	11th to 20th	Day	40% 5% 11% 23% 18% 3	2457
	21st to end	Day	45% 5% 11% 26% 12% 1	2600
May	1st to 10th	Day	48% 6% 9% 20% 14% 3	4250
	11th to 20th	Day	37% 6% 12% 24% 20% 1	4216
	21st to end	Day	39% 8% 13% 23% 15% 2	4555
June	1st to 10th	Day	26% 8% 16% 32% 15% 2	2470
	11th to 20th	Day	31% 6% 13% 28% 18% 4	2470
	21st to end	Day	25% 7% 15% 28% 21% 5%	2470
July	1st to 10th	Day	37% 6% 11% 23% 19% 4	4056
	11th to 20th	Day	26% 5% 13% 32% 19% 4	4051
	21st to end	Day	31% 6% 17% 26% 19% 1	4325
August	1st to 10th	Day	30% 5% 12% 25% 22% 6%	4090
	11th to 20th	Day	35% 4 15% 25% 17% 2	4080
	21st to end	Day	23% 4 16% 34% 18% 5%	4417
September	1st to 10th	Day	31% 5% 12% 23% 21% 8%	2125
	11th to 20th	Day	30% 5% 11% 28% 23% 3	2090
	21st to end	Day	30% 5% 9% 24% 27% 4	2090
October	1st to 10th	Day	20% 3 7% 17% 42% 9%	3293
	11th to 20th	Day	16% 2 7% 32% 32% 11%	3140
	21st to end	Day	28% 3 9% 26% 29% 6%	3428
November	1st to 10th	Day	27% 4 11% 29% 21% 7%	1842
	11th to 20th	Day	30% 4 9% 27% 26% 5%	1800
	21st to end	Day	32% 3 10% 29% 22% 3	1800
December	1st to 10th	Day	24% 3 10% 40% 21% 1	2940
	11th to 20th	Day	33% 3 9% 35% 19% 2	3389
	21st to end	Day	57% 4 8% 22% 8% 1	4488
January	1st to 10th	Night	46% 3 10% 26% 14% 2	5888
	11th to 20th	Night	36% 4 10% 25% 21% 4	5900
	21st to end	Night	40% 3 10% 21% 20% 7%	6490
February	1st to 10th	Night	41% 4 13% 24% 14% 4	2600
	11th to 20th	Night	38% 5% 11% 26% 17% 3	2424
	21st to end	Night	32% 6% 9% 22% 23% 8%	1980
March	1st to 10th	Night	30% 3 6% 24% 28% 8%	4968
	11th to 20th	Night	23% 5% 8% 18% 34% 12%	4980
	21st to end	Night	37% 5% 15% 30% 12% 2	5467
April	1st to 10th	Night	32% 5% 12% 22% 24% 5%	2195
	11th to 20th	Night	34% 5% 12% 24% 21% 3	1889
	21st to end	Night	38% 6% 14% 23% 17% 3	1800
May	1st to 10th	Night	38% 7% 14% 23% 14% 5%	2940
	11th to 20th	Night	35% 6% 15% 28% 15% 1	2914
	21st to end	Night	28% 7% 17% 30% 17% 1	3149
June	1st to 10th	Night	23% 9% 20% 30% 15% 3	1710
	11th to 20th	Night	24% 7% 16% 31% 18% 3	1710
	21st to end	Night	23% 6% 14% 32% 20% 5%	1710
July	1st to 10th	Night	31% 5% 15% 23% 21% 6%	2805
	11th to 20th	Night	21% 4 14% 32% 25% 3	2796
	21st to end	Night	31% 7% 16% 30% 15% 1	2999
August	1st to 10th	Night	25% 4 17% 26% 19% 9%	2826
	11th to 20th	Night	32% 5% 16% 25% 20% 2	2825
	21st to end	Night	19% 4 14% 38% 18% 5%	3245
September	1st to 10th	Night	26% 4 11% 26% 23% 10%	2051
	11th to 20th	Night	28% 5% 11% 25% 26% 6%	2090
	21st to end	Night	25% 4 9% 24% 31% 7%	2090
October	1st to 10th	Night	19% 4 6% 15% 47% 9%	3633
	11th to 20th	Night	18% 2 5% 28% 33% 14%	3779
	21st to end	Night	27% 3 7% 25% 32% 4	4120
November	1st to 10th	Night	25% 4 9% 29% 25% 8%	2453
	11th to 20th	Night	27% 3 10% 29% 26% 5%	2600
	21st to end	Night	30% 4 11% 28% 22% 5%	2600
December	1st to 10th	Night	24% 3 14% 37% 21% 1	4250
	11th to 20th	Night	31% 3 11% 31% 21% 3	4817
	21st to end	Night	50% 4 8% 25% 11% 2	6490

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% 16% 31% 25% 8% 1	300
	11th to 20th	Day	19% 16% 43% 19% 3	300
	21st to end	Day	12% 13% 45% 25% 5% 1	330
February	1st to 10th	Day	23% 19% 39% 15% 4	300
	11th to 20th	Day	18% 16% 44% 17% 5%	300
	21st to end	Day	14% 25% 45% 13% 2 1	249
March	1st to 10th	Day	21% 15% 43% 18% 4	300
	11th to 20th	Day	23% 13% 42% 16% 5%	300
	21st to end	Day	23% 25% 35% 13% 2 1	330
April	1st to 10th	Day	22% 22% 36% 16% 4	304
	11th to 20th	Day	19% 15% 41% 20% 4 1	575
	21st to end	Day	23% 19% 33% 18% 6% 2	700
May	1st to 10th	Day	19% 14% 36% 22% 8% 1	703
	11th to 20th	Day	19% 13% 28% 24% 14% 3	725
	21st to end	Day	20% 8% 31% 24% 14% 3	760
June	1st to 10th	Day	5% 5% 25% 37% 23% 5%	680
	11th to 20th	Day	8% 4 34% 37% 15% 3	680
	21st to end	Day	6% 8% 35% 37% 13% 1	680
July	1st to 10th	Day	11% 2 17% 34% 28% 8%	671
	11th to 20th	Day	4 4 18% 42% 27% 5%	668
	21st to end	Day	9% 2 16% 36% 31% 7%	739
August	1st to 10th	Day	7% 3 19% 38% 29% 3	676
	11th to 20th	Day	10% 2 18% 40% 25% 5%	665
	21st to end	Day	8% 2 17% 35% 30% 8%	686
September	1st to 10th	Day	10% 3 15% 38% 29% 5%	335
	11th to 20th	Day	6% 2 24% 40% 23% 4	300
	21st to end	Day	14% 6% 30% 30% 16% 4	300
October	1st to 10th	Day	12% 7% 34% 26% 16% 6%	300
	11th to 20th	Day	7% 18% 42% 25% 7% 1	300
	21st to end	Day	23% 13% 35% 21% 6% 2	330
November	1st to 10th	Day	14% 13% 36% 26% 10%	300
	11th to 20th	Day	18% 21% 30% 20% 9% 1	300
	21st to end	Day	19% 13% 37% 21% 8% 1	300
December	1st to 10th	Day	10% 15% 40% 28% 6% 2	300
	11th to 20th	Day	16% 14% 39% 23% 7%	300
	21st to end	Day	19% 20% 40% 17% 4	330
January	1st to 10th	Night	13% 11% 41% 29% 6%	1000
	11th to 20th	Night	13% 16% 38% 28% 5% 1	1000
	21st to end	Night	13% 13% 40% 31% 3	1100
February	1st to 10th	Night	16% 12% 43% 26% 3	1000
	11th to 20th	Night	16% 14% 39% 27% 4	869
	21st to end	Night	14% 16% 40% 26% 4	660
March	1st to 10th	Night	14% 12% 42% 28% 4	625
	11th to 20th	Night	18% 12% 39% 25% 6% 1	600
	21st to end	Night	23% 13% 40% 20% 5%	660
April	1st to 10th	Night	16% 14% 41% 24% 5%	600
	11th to 20th	Night	17% 17% 36% 26% 4	593
	21st to end	Night	18% 13% 39% 24% 6% 1	600
May	1st to 10th	Night	19% 9% 35% 31% 7%	600
	11th to 20th	Night	16% 8% 30% 34% 12% 1	591
	21st to end	Night	14% 8% 30% 33% 14% 2	634
June	1st to 10th	Night	6% 4 30% 38% 22% 1	570
	11th to 20th	Night	5% 4 36% 39% 15%	570
	21st to end	Night	5% 4 36% 44% 11% 1	570
July	1st to 10th	Night	8% 2 18% 42% 28% 2	555
	11th to 20th	Night	3 2 20% 50% 22% 3	552
	21st to end	Night	9% 2 17% 40% 30% 2	624
August	1st to 10th	Night	5% 1 18% 48% 26% 1	567
	11th to 20th	Night	8% 2 16% 49% 24% 1	564
	21st to end	Night	7% 1 18% 42% 31% 2	627
September	1st to 10th	Night	11% 3 21% 43% 19% 2	570
	11th to 20th	Night	10% 2 26% 38% 21% 2	570
	21st to end	Night	8% 6% 29% 39% 18% 1	570
October	1st to 10th	Night	12% 6% 28% 34% 18% 1	658
	11th to 20th	Night	13% 8% 41% 30% 7%	760
	21st to end	Night	16% 11% 33% 29% 10%	836
November	1st to 10th	Night	12% 10% 35% 32% 12%	893
	11th to 20th	Night	12% 14% 38% 28% 7%	1000
	21st to end	Night	16% 12% 33% 32% 7%	1000
December	1st to 10th	Night	13% 11% 39% 32% 6% 1	1000
	11th to 20th	Night	17% 11% 39% 28% 5%	1000
	21st to end	Night	16% 15% 36% 28% 5%	1100

Page generated at 2025-05-23 08:20:59. Version ac07

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