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 2026-09-29.

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%	149269
	Night	10% 6% 2 5% 3 3 4 3 5% 7% 52%	142562
Transparency	Day	35% 4 11% 26% 20% 4	152933
	Night	32% 4 11% 27% 21% 5%	146965
Seeing	Day	14% 10% 31% 28% 14% 3	18261
	Night	13% 10% 34% 32% 11% 1	28008

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	12% 8% 2 8% 4 4 4 3 5% 7% 43%	5289
	11th to 20th	Day	5% 8% 3 7% 5% 6% 4 3 4 6% 47%	5310
	21st to end	Day	10% 11% 4 7% 3 3 4 3 4 5% 47%	5812
February	1st to 10th	Day	10% 12% 3 7% 5% 4 3 3 3 7% 43%	1890
	11th to 20th	Day	8% 8% 3 8% 5% 5% 4 3 5% 6% 45%	1978
	21st to end	Day	8% 6% 3 6% 4 3 5% 3 5% 7% 49%	1730
March	1st to 10th	Day	10% 7% 2 5% 3 3 3 2 4 6% 55%	4998
	11th to 20th	Day	9% 6% 2 4 3 3 3 2 4 6% 60%	5090
	21st to end	Day	11% 7% 3 7% 5% 4 5% 3 5% 7% 42%	5583
April	1st to 10th	Day	12% 8% 2 5% 3 4 3 3 5% 6% 50%	2314
	11th to 20th	Day	13% 7% 3 6% 4 4 4 3 5% 7% 45%	2581
	21st to end	Day	18% 8% 2 6% 5% 3 4 3 5% 6% 39%	2730
May	1st to 10th	Day	17% 8% 3 6% 3 3 3 3 4 5% 44%	7617
	11th to 20th	Day	10% 5% 2 5% 3 3 3 3 5% 6% 54%	7627
	21st to end	Day	20% 6% 2 6% 4 4 4 3 5% 7% 38%	8392
June	1st to 10th	Day	6% 4 1 5% 4 5% 5% 4 7% 9% 50%	2730
	11th to 20th	Day	8% 4 1 5% 5% 5% 5% 3 6% 8% 51%	2730
	21st to end	Day	6% 4 1 5% 4 4 4 4 7% 8% 53%	2730
July	1st to 10th	Day	7% 4 2 5% 5% 5% 6% 5% 7% 9% 46%	7680
	11th to 20th	Day	7% 3 1 4 4 4 5% 4 6% 8% 55%	7680
	21st to end	Day	7% 4 2 6% 4 5% 5% 5% 7% 9% 44%	8337
August	1st to 10th	Day	5% 4 2 6% 5% 5% 5% 3 5% 6% 54%	6014
	11th to 20th	Day	7% 5% 2 6% 4 4 5% 4 6% 9% 48%	5948
	21st to end	Day	5% 3 1 4 3 4 4 3 6% 9% 57%	6433
September	1st to 10th	Day	13% 4 2 4 3 3 4 3 5% 6% 54%	2349
	11th to 20th	Day	9% 5% 2 5% 3 4 4 4 5% 6% 53%	2310
	21st to end	Day	10% 6% 2 5% 4 3 4 3 5% 5% 53%	2288
October	1st to 10th	Day	11% 3 2 5% 3 3 4 3 4 6% 55%	2085
	11th to 20th	Day	10% 5% 1 4 3 2 2 2 4 5% 62%	2000
	21st to end	Day	14% 7% 1 5% 3 3 3 3 4 4 54%	2200
November	1st to 10th	Day	8% 5% 2 5% 3 2 3 3 4 7% 59%	1936
	11th to 20th	Day	9% 6% 1 4 4 3 3 3 4 6% 57%	1890
	21st to end	Day	14% 4 2 5% 3 3 3 2 4 5% 55%	1890
December	1st to 10th	Day	6% 4 2 4 3 3 4 3 5% 6% 61%	3030
	11th to 20th	Day	8% 6% 3 6% 3 4 4 3 3 5% 56%	3481
	21st to end	Day	17% 11% 6% 12% 4 3 3 3 4 5% 31%	4587
January	1st to 10th	Night	12% 9% 3 10% 5% 4 3 3 4 6% 43%	7634
	11th to 20th	Night	5% 6% 2 5% 4 5% 4 3 4 6% 55%	7680
	21st to end	Night	13% 9% 3 6% 4 4 3 3 4 5% 46%	8402
February	1st to 10th	Night	10% 10% 3 7% 5% 4 3 3 5% 6% 45%	2730
	11th to 20th	Night	10% 9% 2 6% 4 4 4 3 4 6% 48%	2547
	21st to end	Night	9% 6% 2 5% 3 3 4 4 5% 6% 53%	2076
March	1st to 10th	Night	11% 7% 2 4 2 3 3 2 4 5% 57%	5079
	11th to 20th	Night	7% 4 1 4 2 3 4 3 6% 7% 60%	5090
	21st to end	Night	12% 6% 2 6% 4 4 4 3 5% 7% 47%	5588
April	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 7% 53%	2305
	11th to 20th	Night	11% 7% 2 5% 3 3 3 4 6% 6% 51%	1985
	21st to end	Night	15% 6% 3 5% 3 3 4 3 5% 8% 45%	1890
May	1st to 10th	Night	15% 8% 2 4 3 3 3 3 4 7% 49%	5266
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 5% 7% 53%	5265
	21st to end	Night	21% 5% 2 4 3 3 3 3 5% 6% 46%	5793
June	1st to 10th	Night	6% 3 1 4 3 4 4 5% 6% 11% 53%	1890
	11th to 20th	Night	5% 3 2 4 4 4 4 4 7% 10% 52%	1890
	21st to end	Night	6% 3 1 5% 3 3 4 4 6% 8% 57%	1890
July	1st to 10th	Night	6% 4 2 6% 4 4 4 4 7% 10% 51%	5308
	11th to 20th	Night	5% 3 1 4 4 3 4 3 5% 9% 58%	5307
	21st to end	Night	8% 4 2 6% 5% 5% 5% 4 8% 10% 44%	5770
August	1st to 10th	Night	3 3 1 5% 4 4 5% 4 6% 9% 56%	4156
	11th to 20th	Night	6% 3 1 5% 4 4 5% 4 7% 10% 51%	4118
	21st to end	Night	4 2 1 3 3 3 3 3 5% 9% 64%	4707
September	1st to 10th	Night	10% 3 1 4 3 3 2 2 4 6% 59%	2267
	11th to 20th	Night	8% 4 2 4 3 3 4 3 6% 6% 56%	2310
	21st to end	Night	7% 4 2 5% 3 3 3 3 4 7% 60%	2288
October	1st to 10th	Night	10% 4 2 5% 3 3 4 3 4 6% 55%	2293
	11th to 20th	Night	10% 4 2 4 3 3 3 2 4 5% 60%	2400
	21st to end	Night	14% 5% 2 4 3 3 3 2 4 5% 56%	2640
November	1st to 10th	Night	9% 4 2 4 2 3 2 2 4 5% 63%	2579
	11th to 20th	Night	8% 5% 1 4 3 2 3 2 5% 7% 59%	2730
	21st to end	Night	13% 6% 2 4 3 2 2 3 4 5% 56%	2730
December	1st to 10th	Night	5% 4 2 5% 3 3 3 3 4 5% 62%	4380
	11th to 20th	Night	9% 6% 2 5% 3 3 3 3 5% 6% 54%	4946
	21st to end	Night	17% 10% 4 9% 4 4 3 2 4 5% 38%	6633

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	42% 3 11% 27% 15% 2	5290
	11th to 20th	Day	39% 3 12% 23% 20% 3	5310
	21st to end	Day	42% 3 10% 26% 16% 4	5812
February	1st to 10th	Day	43% 4 12% 25% 12% 4	1890
	11th to 20th	Day	41% 4 12% 25% 14% 4	1987
	21st to end	Day	34% 5% 10% 24% 22% 6%	1730
March	1st to 10th	Day	32% 3 7% 20% 26% 12%	4998
	11th to 20th	Day	27% 3 8% 22% 28% 12%	5090
	21st to end	Day	40% 5% 12% 32% 9% 2	5585
April	1st to 10th	Day	36% 4 11% 24% 20% 4	2314
	11th to 20th	Day	40% 5% 12% 22% 18% 4	2581
	21st to end	Day	46% 5% 11% 26% 12% 1	2730
May	1st to 10th	Day	43% 4 8% 22% 21% 2	7655
	11th to 20th	Day	31% 4 9% 24% 27% 5%	7631
	21st to end	Day	46% 5% 11% 21% 16% 1	8405
June	1st to 10th	Day	28% 8% 16% 30% 16% 3	2730
	11th to 20th	Day	31% 6% 13% 28% 19% 4	2730
	21st to end	Day	27% 6% 15% 27% 20% 5%	2730
July	1st to 10th	Day	34% 4 11% 26% 21% 3	7616
	11th to 20th	Day	28% 4 13% 28% 19% 9%	7611
	21st to end	Day	34% 4 14% 33% 13% 1	8155
August	1st to 10th	Day	32% 4 10% 24% 26% 5%	6000
	11th to 20th	Day	34% 4 15% 30% 15% 2	5987
	21st to end	Day	25% 3 18% 34% 16% 4	6432
September	1st to 10th	Day	32% 5% 12% 23% 21% 8%	2349
	11th to 20th	Day	31% 5% 11% 28% 21% 3	2310
	21st to end	Day	32% 5% 9% 24% 26% 4	2288
October	1st to 10th	Day	21% 3 7% 18% 43% 9%	3397
	11th to 20th	Day	17% 2 7% 32% 32% 10%	3240
	21st to end	Day	29% 3 8% 26% 28% 6%	3538
November	1st to 10th	Day	26% 4 11% 30% 22% 7%	1936
	11th to 20th	Day	30% 3 9% 28% 25% 5%	1890
	21st to end	Day	33% 3 10% 30% 21% 3	1890
December	1st to 10th	Day	25% 3 10% 40% 21% 1	3030
	11th to 20th	Day	33% 3 9% 35% 19% 2	3479
	21st to end	Day	56% 4 8% 23% 9% 1	4587
January	1st to 10th	Night	45% 3 10% 25% 17% 1	7635
	11th to 20th	Night	31% 3 10% 29% 22% 4	7680
	21st to end	Night	42% 2 10% 21% 20% 5%	8402
February	1st to 10th	Night	40% 4 13% 24% 15% 4	2730
	11th to 20th	Night	37% 5% 11% 26% 17% 4	2548
	21st to end	Night	32% 6% 8% 22% 24% 9%	2076
March	1st to 10th	Night	31% 3 6% 24% 27% 8%	5079
	11th to 20th	Night	24% 4 7% 18% 34% 12%	5090
	21st to end	Night	37% 5% 15% 30% 12% 2	5588
April	1st to 10th	Night	32% 4 12% 22% 24% 5%	2305
	11th to 20th	Night	34% 5% 12% 24% 21% 4	1985
	21st to end	Night	38% 6% 14% 23% 16% 3	1890
May	1st to 10th	Night	36% 5% 11% 25% 20% 3	5293
	11th to 20th	Night	31% 4 12% 24% 21% 7%	5266
	21st to end	Night	40% 5% 14% 25% 15% 1	5805
June	1st to 10th	Night	25% 8% 20% 28% 16% 3	1890
	11th to 20th	Night	25% 7% 16% 31% 19% 3	1890
	21st to end	Night	24% 6% 15% 31% 19% 5%	1890
July	1st to 10th	Night	29% 4 14% 28% 21% 3	5265
	11th to 20th	Night	25% 3 16% 28% 21% 8%	5256
	21st to end	Night	34% 5% 12% 37% 12%	5641
August	1st to 10th	Night	25% 3 14% 26% 25% 7%	4146
	11th to 20th	Night	29% 4 17% 31% 18% 2	4145
	21st to end	Night	19% 3 19% 38% 17% 4	4707
September	1st to 10th	Night	27% 4 11% 26% 23% 9%	2267
	11th to 20th	Night	29% 4 11% 26% 25% 5%	2310
	21st to end	Night	27% 4 10% 24% 30% 6%	2288
October	1st to 10th	Night	20% 4 6% 15% 47% 9%	3748
	11th to 20th	Night	19% 2 5% 28% 32% 14%	3899
	21st to end	Night	28% 3 7% 25% 32% 5%	4252
November	1st to 10th	Night	25% 3 9% 29% 25% 8%	2579
	11th to 20th	Night	26% 3 10% 30% 26% 5%	2730
	21st to end	Night	32% 4 11% 28% 21% 5%	2730
December	1st to 10th	Night	25% 3 14% 37% 21% 1	4380
	11th to 20th	Night	31% 3 11% 31% 22% 3	4947
	21st to end	Night	50% 4 8% 25% 12% 2	6633

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% 32% 25% 8% 1	330
	11th to 20th	Day	19% 17% 42% 19% 3	330
	21st to end	Day	12% 13% 44% 25% 4 1	363
February	1st to 10th	Day	21% 19% 40% 16% 4	330
	11th to 20th	Day	19% 16% 42% 18% 4	330
	21st to end	Day	14% 25% 45% 14% 2 1	273
March	1st to 10th	Day	22% 15% 42% 17% 4	330
	11th to 20th	Day	25% 13% 41% 17% 4	330
	21st to end	Day	21% 25% 38% 13% 2 1	363
April	1st to 10th	Day	22% 22% 36% 16% 4	334
	11th to 20th	Day	19% 16% 41% 19% 4	619
	21st to end	Day	23% 18% 34% 17% 5% 1	750
May	1st to 10th	Day	18% 14% 37% 22% 8% 1	753
	11th to 20th	Day	18% 13% 30% 23% 13% 3	775
	21st to end	Day	20% 8% 30% 25% 14% 3	844
June	1st to 10th	Day	6% 6% 26% 36% 21% 4	780
	11th to 20th	Day	8% 5% 34% 36% 15% 3	780
	21st to end	Day	7% 8% 36% 36% 12% 1	780
July	1st to 10th	Day	10% 2 18% 35% 27% 8%	771
	11th to 20th	Day	4 4 17% 43% 27% 6%	768
	21st to end	Day	9% 3 16% 38% 28% 6%	849
August	1st to 10th	Day	7% 4 22% 37% 27% 3	776
	11th to 20th	Day	9% 1 19% 41% 24% 5%	765
	21st to end	Day	9% 2 17% 37% 28% 7%	789
September	1st to 10th	Day	12% 3 14% 38% 28% 4	399
	11th to 20th	Day	7% 3 26% 38% 21% 4	360
	21st to end	Day	14% 6% 28% 30% 17% 4	354
October	1st to 10th	Day	11% 7% 35% 27% 15% 5%	330
	11th to 20th	Day	7% 18% 42% 25% 7% 1	330
	21st to end	Day	25% 13% 34% 20% 6% 2	363
November	1st to 10th	Day	13% 14% 39% 25% 9%	330
	11th to 20th	Day	16% 20% 31% 22% 9% 1	330
	21st to end	Day	20% 13% 38% 21% 8% 1	330
December	1st to 10th	Day	10% 15% 39% 28% 5% 2	330
	11th to 20th	Day	15% 14% 40% 24% 7%	330
	21st to end	Day	18% 19% 40% 18% 4	363
January	1st to 10th	Night	13% 12% 41% 28% 6%	1050
	11th to 20th	Night	12% 16% 39% 28% 5% 1	1050
	21st to end	Night	14% 13% 40% 30% 3	1155
February	1st to 10th	Night	15% 12% 43% 26% 4	1050
	11th to 20th	Night	16% 15% 39% 27% 4	913
	21st to end	Night	14% 16% 41% 25% 4	692
March	1st to 10th	Night	15% 12% 41% 28% 4	656
	11th to 20th	Night	18% 13% 38% 25% 6%	630
	21st to end	Night	22% 13% 41% 20% 4	693
April	1st to 10th	Night	16% 14% 41% 24% 4	630
	11th to 20th	Night	17% 17% 36% 26% 4	623
	21st to end	Night	18% 13% 39% 23% 6% 1	630
May	1st to 10th	Night	18% 10% 35% 30% 7%	630
	11th to 20th	Night	15% 8% 30% 34% 12%	621
	21st to end	Night	14% 8% 29% 33% 14% 2	683
June	1st to 10th	Night	6% 5% 30% 38% 20% 1	630
	11th to 20th	Night	6% 5% 36% 39% 14%	630
	21st to end	Night	5% 4 37% 43% 10% 1	630
July	1st to 10th	Night	8% 2 19% 42% 27% 2	615
	11th to 20th	Night	3 2 21% 49% 22% 3	612
	21st to end	Night	9% 2 18% 41% 29% 1	690
August	1st to 10th	Night	5% 2 21% 46% 24% 1	627
	11th to 20th	Night	8% 2 17% 49% 24% 1	624
	21st to end	Night	7% 1 17% 44% 30% 2	693
September	1st to 10th	Night	11% 3 21% 43% 19% 2	630
	11th to 20th	Night	10% 3 26% 38% 21% 2	630
	21st to end	Night	8% 5% 28% 39% 19% 1	624
October	1st to 10th	Night	12% 6% 29% 34% 18% 1	693
	11th to 20th	Night	14% 8% 41% 30% 7%	800
	21st to end	Night	18% 11% 33% 28% 10%	880
November	1st to 10th	Night	11% 10% 36% 31% 12%	939
	11th to 20th	Night	11% 13% 38% 29% 7%	1050
	21st to end	Night	17% 12% 32% 32% 7%	1050
December	1st to 10th	Night	13% 11% 38% 32% 6% 1	1050
	11th to 20th	Night	17% 12% 39% 27% 5%	1050
	21st to end	Night	16% 15% 35% 29% 5%	1155

Page generated at 2026-09-26 03:18:42. Version ac07

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