Theodore Roosevelt National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Theodore Roosevelt National Park clear sky chart from 2005-11-06 to 2026-01-17.

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	9% 7% 3 7% 4 4 4 4 6% 7% 45%	136596
	Night	7% 7% 3 8% 5% 4 5% 4 6% 7% 44%	132515
Transparency	Day	37% 6% 14% 27% 14% 2	131248
	Night	38% 6% 15% 26% 14% 2	128870
Seeing	Day	12% 9% 30% 30% 15% 3	17699
	Night	11% 8% 34% 35% 11% 1	27776

By Month

Percentage Cloud Cover SW (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	5% 9% 5% 11% 8% 7% 6% 5% 7% 7% 30%	3718
	11th to 20th	Day	2 9% 3 13% 6% 6% 7% 5% 8% 10% 30%	3688
	21st to end	Day	2 8% 4 11% 6% 4 4 3 5% 7% 45%	4004
February	1st to 10th	Day	7% 13% 5% 10% 6% 5% 5% 4 6% 7% 32%	1695
	11th to 20th	Day	5% 12% 5% 11% 6% 5% 6% 5% 6% 7% 32%	1840
	21st to end	Day	4 12% 4 11% 7% 5% 5% 4 6% 8% 34%	1650
March	1st to 10th	Day	5% 7% 4 9% 5% 4 4 4 5% 6% 47%	4500
	11th to 20th	Day	6% 9% 4 8% 5% 5% 5% 5% 7% 9% 37%	4661
	21st to end	Day	13% 17% 5% 10% 5% 4 4 4 5% 6% 26%	5969
April	1st to 10th	Day	10% 9% 4 7% 6% 5% 4 4 6% 8% 38%	2400
	11th to 20th	Day	12% 11% 4 9% 6% 5% 5% 4 6% 5% 32%	2378
	21st to end	Day	14% 8% 3 6% 5% 4 4 5% 6% 8% 38%	2600
May	1st to 10th	Day	14% 7% 2 5% 3 4 4 4 5% 6% 47%	6296
	11th to 20th	Day	18% 6% 2 5% 4 4 4 4 6% 8% 39%	6298
	21st to end	Day	14% 5% 2 5% 3 4 4 3 5% 8% 47%	6925
June	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 7% 8% 45%	2800
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 5% 7% 8% 42%	2800
	21st to end	Day	6% 4 1 4 4 4 5% 3 7% 10% 53%	2800
July	1st to 10th	Day	6% 3 1 5% 4 4 5% 4 6% 8% 52%	6339
	11th to 20th	Day	9% 4 1 4 3 3 4 3 6% 7% 57%	6340
	21st to end	Day	7% 4 2 6% 4 4 5% 4 6% 9% 50%	6903
August	1st to 10th	Day	11% 4 2 4 3 4 4 3 5% 7% 52%	6232
	11th to 20th	Day	7% 4 1 6% 4 4 4 3 5% 8% 53%	5981
	21st to end	Day	7% 4 1 4 3 3 3 3 5% 6% 61%	5984
September	1st to 10th	Day	8% 5% 2 5% 2 3 3 2 5% 7% 59%	2400
	11th to 20th	Day	10% 5% 2 4 3 3 4 3 5% 9% 53%	2329
	21st to end	Day	11% 5% 2 4 2 3 3 2 4 6% 59%	2200
October	1st to 10th	Day	8% 4 2 3 3 3 3 3 5% 6% 61%	3371
	11th to 20th	Day	8% 6% 3 5% 4 3 3 3 4 8% 53%	3120
	21st to end	Day	8% 7% 3 5% 3 4 4 3 5% 7% 51%	3190
November	1st to 10th	Day	9% 11% 4 6% 4 4 5% 4 5% 6% 41%	1853
	11th to 20th	Day	5% 10% 3 8% 5% 5% 5% 4 6% 9% 41%	1754
	21st to end	Day	6% 9% 4 9% 5% 6% 6% 4 7% 6% 38%	1680
December	1st to 10th	Day	4 11% 6% 12% 6% 4 4 3 5% 7% 36%	2700
	11th to 20th	Day	8% 11% 5% 11% 4 6% 5% 4 5% 6% 34%	3106
	21st to end	Day	4 9% 4 9% 6% 5% 5% 5% 5% 7% 41%	4092
January	1st to 10th	Night	4 12% 6% 13% 7% 6% 5% 4 6% 6% 31%	6467
	11th to 20th	Night	3 8% 4 11% 7% 7% 8% 5% 8% 6% 32%	6425
	21st to end	Night	2 8% 5% 11% 5% 5% 6% 4 5% 6% 43%	6974
February	1st to 10th	Night	6% 12% 4 10% 7% 7% 6% 5% 6% 7% 31%	2721
	11th to 20th	Night	4 10% 4 10% 6% 5% 6% 4 7% 7% 36%	2445
	21st to end	Night	5% 10% 3 9% 6% 4 4 4 6% 9% 40%	1980
March	1st to 10th	Night	7% 8% 3 6% 4 4 4 4 6% 7% 48%	5374
	11th to 20th	Night	4 7% 3 8% 4 5% 5% 5% 8% 10% 41%	5318
	21st to end	Night	12% 15% 6% 11% 5% 5% 5% 4 6% 7% 23%	4984
April	1st to 10th	Night	10% 10% 2 6% 5% 3 5% 5% 7% 7% 41%	2000
	11th to 20th	Night	12% 10% 3 8% 4 4 5% 5% 7% 7% 36%	1969
	21st to end	Night	12% 7% 2 6% 4 5% 4 3 5% 7% 45%	1800
May	1st to 10th	Night	10% 5% 2 5% 3 4 4 3 5% 6% 53%	3668
	11th to 20th	Night	20% 6% 2 6% 4 4 4 4 5% 8% 37%	3617
	21st to end	Night	14% 6% 2 5% 3 4 4 3 5% 6% 48%	3972
June	1st to 10th	Night	10% 5% 2 4 3 4 5% 3 7% 8% 50%	1600
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 5% 9% 47%	1600
	21st to end	Night	5% 4 2 5% 3 4 4 4 5% 7% 58%	1600
July	1st to 10th	Night	7% 4 1 5% 3 3 4 4 7% 9% 52%	3640
	11th to 20th	Night	5% 3 1 3 3 2 3 4 5% 9% 62%	3640
	21st to end	Night	7% 4 1 5% 4 4 5% 4 6% 8% 52%	3970
August	1st to 10th	Night	7% 5% 1 4 4 3 4 3 6% 8% 55%	3580
	11th to 20th	Night	5% 3 1 5% 3 3 4 4 6% 8% 58%	3865
	21st to end	Night	8% 4 1 4 3 3 3 4 5% 7% 58%	4993
September	1st to 10th	Night	7% 2 2 3 2 2 3 3 5% 7% 64%	2000
	11th to 20th	Night	10% 4 1 5% 3 3 4 3 5% 8% 53%	2070
	21st to end	Night	11% 5% 2 4 3 3 3 3 4 7% 55%	2200
October	1st to 10th	Night	9% 5% 2 4 3 2 3 2 5% 7% 58%	3812
	11th to 20th	Night	8% 7% 2 5% 3 3 4 3 5% 9% 51%	3996
	21st to end	Night	8% 6% 3 6% 4 4 4 3 6% 7% 48%	4610
November	1st to 10th	Night	8% 8% 3 6% 5% 4 5% 4 6% 7% 44%	2665
	11th to 20th	Night	6% 10% 4 9% 6% 5% 4 3 5% 8% 42%	2861
	21st to end	Night	6% 7% 4 8% 6% 5% 5% 5% 6% 8% 41%	2940
December	1st to 10th	Night	5% 12% 6% 12% 6% 5% 5% 4 5% 6% 34%	4710
	11th to 20th	Night	6% 9% 4 11% 7% 6% 5% 4 5% 6% 36%	5321
	21st to end	Night	6% 9% 4 12% 5% 6% 4 4 5% 5% 40%	7128

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	50% 6% 18% 19% 6%	3719
	11th to 20th	Day	48% 6% 15% 13% 18% 1	3688
	21st to end	Day	40% 6% 19% 29% 6%	4004
February	1st to 10th	Day	51% 6% 12% 20% 11% 1	1695
	11th to 20th	Day	50% 8% 13% 18% 10% 2	1849
	21st to end	Day	46% 5% 15% 21% 11% 1	1650
March	1st to 10th	Day	37% 5% 12% 29% 15% 1	4500
	11th to 20th	Day	41% 7% 17% 25% 10%	4661
	21st to end	Day	58% 5% 15% 15% 6%	5969
April	1st to 10th	Day	42% 7% 16% 21% 12% 1	2400
	11th to 20th	Day	51% 7% 12% 20% 10%	2381
	21st to end	Day	43% 7% 15% 25% 9% 1	2600
May	1st to 10th	Day	36% 7% 12% 26% 18% 1	6296
	11th to 20th	Day	41% 7% 12% 26% 12%	6302
	21st to end	Day	35% 6% 14% 30% 15%	6926
June	1st to 10th	Day	36% 8% 16% 27% 12% 1	2800
	11th to 20th	Day	37% 8% 15% 27% 10% 3	2800
	21st to end	Day	25% 8% 20% 29% 16% 2	2800
July	1st to 10th	Day	28% 6% 15% 30% 18% 2	6271
	11th to 20th	Day	25% 4 10% 32% 24% 5%	6265
	21st to end	Day	30% 7% 12% 28% 20% 3	6705
August	1st to 10th	Day	27% 6% 11% 31% 17% 8%	4536
	11th to 20th	Day	32% 6% 14% 32% 13% 3	4327
	21st to end	Day	23% 4 11% 36% 24% 2	4311
September	1st to 10th	Day	27% 4 11% 32% 21% 5%	2400
	11th to 20th	Day	29% 6% 14% 31% 17% 3	2329
	21st to end	Day	29% 3 11% 31% 22% 3	2200
October	1st to 10th	Day	26% 4 8% 30% 26% 6%	3371
	11th to 20th	Day	32% 4 10% 36% 17% 1	3120
	21st to end	Day	33% 5% 11% 32% 17% 2	3190
November	1st to 10th	Day	44% 5% 12% 24% 13% 2	1853
	11th to 20th	Day	39% 6% 16% 25% 12% 2	1754
	21st to end	Day	44% 6% 20% 21% 8% 1	1680
December	1st to 10th	Day	48% 4 19% 21% 8% 1	2700
	11th to 20th	Day	51% 5% 17% 24% 3	3104
	21st to end	Day	42% 5% 10% 32% 11% 1	4092
January	1st to 10th	Night	52% 6% 15% 18% 8%	6467
	11th to 20th	Night	49% 5% 16% 16% 14% 1	6425
	21st to end	Night	42% 5% 20% 24% 8%	6974
February	1st to 10th	Night	51% 7% 15% 16% 11% 1	2721
	11th to 20th	Night	44% 7% 14% 22% 11% 1	2446
	21st to end	Night	41% 6% 16% 24% 11% 2	1980
March	1st to 10th	Night	34% 5% 12% 32% 16%	5374
	11th to 20th	Night	35% 7% 18% 29% 10%	5318
	21st to end	Night	58% 6% 15% 15% 6%	4984
April	1st to 10th	Night	39% 7% 14% 24% 14% 2	2000
	11th to 20th	Night	44% 7% 12% 23% 12% 1	1969
	21st to end	Night	38% 6% 15% 30% 11%	1800
May	1st to 10th	Night	30% 7% 11% 32% 17% 3	3668
	11th to 20th	Night	43% 8% 15% 21% 12% 1	3618
	21st to end	Night	36% 7% 13% 27% 16%	3972
June	1st to 10th	Night	31% 7% 15% 30% 15% 2	1600
	11th to 20th	Night	34% 9% 18% 25% 13% 2	1600
	21st to end	Night	25% 7% 18% 32% 17% 2	1600
July	1st to 10th	Night	27% 6% 18% 33% 14% 2	3600
	11th to 20th	Night	20% 5% 13% 33% 24% 5%	3592
	21st to end	Night	29% 7% 16% 29% 15% 4	3856
August	1st to 10th	Night	25% 5% 12% 30% 20% 9%	2600
	11th to 20th	Night	26% 6% 19% 31% 15% 3	2795
	21st to end	Night	26% 5% 10% 31% 24% 5%	3597
September	1st to 10th	Night	20% 5% 10% 34% 25% 7%	2000
	11th to 20th	Night	30% 6% 14% 28% 19% 4	2070
	21st to end	Night	29% 5% 12% 28% 24% 2	2200
October	1st to 10th	Night	27% 4 8% 26% 28% 7%	3812
	11th to 20th	Night	31% 4 8% 36% 19% 1	3996
	21st to end	Night	36% 4 10% 29% 17% 3	4610
November	1st to 10th	Night	38% 7% 12% 25% 16% 2	2665
	11th to 20th	Night	42% 5% 16% 26% 10% 2	2861
	21st to end	Night	40% 6% 20% 23% 10% 1	2940
December	1st to 10th	Night	50% 5% 20% 19% 5%	4710
	11th to 20th	Night	48% 6% 21% 20% 6%	5322
	21st to end	Night	46% 4 10% 25% 14% 1	7128

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	9% 10% 36% 28% 13% 4	330
	11th to 20th	Day	9% 13% 43% 23% 9% 2	318
	21st to end	Day	8% 16% 40% 27% 8% 1	330
February	1st to 10th	Day	13% 11% 40% 32% 4	300
	11th to 20th	Day	11% 10% 38% 31% 9% 1	300
	21st to end	Day	8% 14% 42% 27% 8% 1	249
March	1st to 10th	Day	17% 10% 37% 24% 9% 3	300
	11th to 20th	Day	13% 10% 35% 28% 10% 4	335
	21st to end	Day	14% 13% 32% 26% 12% 3	550
April	1st to 10th	Day	14% 14% 36% 27% 8% 1	500
	11th to 20th	Day	19% 16% 35% 21% 6% 2	499
	21st to end	Day	19% 9% 26% 31% 15% 1	700
May	1st to 10th	Day	16% 7% 26% 32% 15% 4	703
	11th to 20th	Day	19% 6% 22% 30% 18% 5%	725
	21st to end	Day	16% 8% 26% 26% 18% 5%	789
June	1st to 10th	Day	12% 9% 25% 29% 19% 4	730
	11th to 20th	Day	12% 10% 35% 28% 12% 2	730
	21st to end	Day	8% 6% 31% 32% 19% 3	730
July	1st to 10th	Day	6% 5% 23% 40% 23% 4	721
	11th to 20th	Day	8% 6% 25% 40% 18% 3	718
	21st to end	Day	6% 2 25% 39% 22% 5%	794
August	1st to 10th	Day	8% 5% 21% 37% 25% 5%	726
	11th to 20th	Day	7% 4 24% 36% 24% 5%	684
	21st to end	Day	9% 6% 24% 30% 24% 7%	583
September	1st to 10th	Day	9% 6% 31% 29% 19% 6%	530
	11th to 20th	Day	12% 8% 24% 36% 17% 3	459
	21st to end	Day	15% 8% 29% 27% 17% 5%	330
October	1st to 10th	Day	19% 7% 22% 28% 19% 4	330
	11th to 20th	Day	12% 13% 35% 24% 13% 3	330
	21st to end	Day	15% 15% 34% 24% 10% 2	363
November	1st to 10th	Day	14% 12% 39% 21% 13% 2	330
	11th to 20th	Day	12% 13% 33% 30% 11% 2	330
	21st to end	Day	9% 12% 35% 34% 10%	330
December	1st to 10th	Day	11% 14% 39% 25% 10% 1	330
	11th to 20th	Day	14% 12% 40% 26% 7% 1	330
	21st to end	Day	6% 12% 37% 33% 12% 1	363
January	1st to 10th	Night	8% 11% 42% 30% 9% 1	1050
	11th to 20th	Night	10% 15% 39% 28% 8% 1	1031
	21st to end	Night	9% 12% 40% 31% 8%	1100
February	1st to 10th	Night	11% 11% 37% 31% 9% 1	921
	11th to 20th	Night	8% 10% 40% 32% 9% 1	784
	21st to end	Night	8% 8% 37% 35% 11% 2	660
March	1st to 10th	Night	11% 11% 37% 34% 7% 1	800
	11th to 20th	Night	10% 7% 39% 34% 9% 1	790
	21st to end	Night	15% 7% 32% 35% 11%	660
April	1st to 10th	Night	13% 10% 34% 35% 8%	600
	11th to 20th	Night	15% 11% 36% 30% 8% 1	593
	21st to end	Night	15% 7% 29% 37% 12%	600
May	1st to 10th	Night	11% 6% 27% 41% 14% 1	600
	11th to 20th	Night	16% 4 27% 38% 15%	591
	21st to end	Night	18% 6% 26% 36% 13% 1	650
June	1st to 10th	Night	11% 9% 31% 36% 13% 1	600
	11th to 20th	Night	12% 8% 32% 37% 11% 1	600
	21st to end	Night	6% 5% 31% 44% 14% 1	600
July	1st to 10th	Night	5% 3 32% 45% 15%	585
	11th to 20th	Night	5% 5% 30% 49% 10%	582
	21st to end	Night	3 2 30% 51% 14%	657
August	1st to 10th	Night	7% 4 24% 49% 15% 1	597
	11th to 20th	Night	6% 3 24% 46% 20% 1	594
	21st to end	Night	8% 4 26% 44% 18% 1	660
September	1st to 10th	Night	8% 4 22% 48% 18% 1	600
	11th to 20th	Night	11% 5% 26% 42% 15% 1	600
	21st to end	Night	14% 5% 31% 36% 14% 1	600
October	1st to 10th	Night	17% 8% 28% 34% 13% 1	731
	11th to 20th	Night	14% 10% 29% 36% 11% 1	860
	21st to end	Night	13% 10% 37% 28% 10% 1	1100
November	1st to 10th	Night	12% 10% 35% 34% 9%	1025
	11th to 20th	Night	10% 10% 41% 30% 9%	1050
	21st to end	Night	8% 12% 39% 33% 8%	1050
December	1st to 10th	Night	9% 9% 41% 32% 9%	1050
	11th to 20th	Night	12% 13% 37% 31% 7% 1	1050
	21st to end	Night	15% 10% 36% 30% 9%	1155

Page generated at 2026-01-13 23:14:27. Version ac07

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