Theodore Roosevelt Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Theodore Roosevelt Nature Center 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	16% 7% 2 6% 4 4 4 4 5% 7% 40%	127273
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 42%	124409
Transparency	Day	27% 38% 8% 15% 11% 2	130800
	Night	28% 37% 7% 15% 11% 2	128969
Seeing	Day	21% 15% 32% 22% 9% 2	16536
	Night	21% 13% 31% 26% 9% 1	25738

By Month

Percentage Cloud Cover NE (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	13% 6% 1 5% 3 3 3 2 4 6% 52%	3677
	11th to 20th	Day	14% 8% 2 6% 4 4 4 4 4 6% 45%	3618
	21st to end	Day	18% 10% 4 7% 4 4 4 2 4 4 39%	4254
February	1st to 10th	Day	17% 9% 2 6% 4 4 4 3 4 7% 39%	1855
	11th to 20th	Day	15% 7% 2 7% 4 3 3 3 5% 6% 44%	1948
	21st to end	Day	20% 7% 3 6% 4 3 4 3 5% 5% 39%	1650
March	1st to 10th	Day	22% 7% 2 6% 3 3 3 3 4 5% 42%	4476
	11th to 20th	Day	12% 8% 3 6% 4 4 4 4 6% 8% 42%	4694
	21st to end	Day	18% 7% 2 6% 4 3 4 3 5% 6% 42%	5970
April	1st to 10th	Day	19% 8% 2 6% 4 4 4 3 5% 8% 37%	2400
	11th to 20th	Day	18% 6% 2 6% 5% 4 4 3 5% 8% 40%	2374
	21st to end	Day	18% 6% 2 5% 4 3 4 4 6% 8% 40%	2450
May	1st to 10th	Day	28% 9% 2 5% 3 3 4 3 6% 8% 29%	5886
	11th to 20th	Day	24% 9% 3 6% 4 3 3 3 4 6% 35%	6148
	21st to end	Day	21% 7% 2 5% 4 4 4 4 5% 8% 36%	6949
June	1st to 10th	Day	18% 6% 1 5% 4 4 4 4 6% 9% 38%	2800
	11th to 20th	Day	15% 7% 3 5% 4 4 5% 4 6% 8% 39%	2800
	21st to end	Day	11% 5% 2 6% 5% 4 4 4 6% 9% 43%	2800
July	1st to 10th	Day	11% 8% 2 7% 5% 5% 5% 4 7% 10% 36%	6360
	11th to 20th	Day	11% 7% 2 7% 5% 5% 5% 5% 8% 11% 34%	6360
	21st to end	Day	13% 7% 2 6% 4 4 5% 4 6% 9% 39%	6926
August	1st to 10th	Day	17% 7% 3 7% 4 5% 5% 4 7% 9% 34%	4286
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 7% 8% 41%	3850
	21st to end	Day	8% 5% 2 5% 3 4 5% 4 7% 10% 47%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 3 5% 7% 46%	2400
	11th to 20th	Day	11% 7% 2 4 3 3 3 4 4 8% 50%	2286
	21st to end	Day	19% 7% 3 6% 4 4 3 4 6% 5% 39%	2200
October	1st to 10th	Day	18% 6% 2 5% 4 3 4 3 4 7% 43%	2134
	11th to 20th	Day	16% 5% 2 4 5% 4 4 3 5% 6% 48%	2000
	21st to end	Day	18% 6% 2 6% 4 3 3 3 5% 7% 44%	2015
November	1st to 10th	Day	13% 6% 2 6% 3 3 3 3 4 5% 52%	1851
	11th to 20th	Day	15% 6% 2 4 3 3 3 3 4 6% 49%	1890
	21st to end	Day	16% 6% 2 6% 4 4 3 3 4 7% 45%	1860
December	1st to 10th	Day	15% 7% 2 6% 4 3 3 4 5% 7% 45%	2680
	11th to 20th	Day	22% 8% 2 4 3 2 2 3 3 5% 47%	3066
	21st to end	Day	18% 9% 2 6% 4 4 4 4 5% 6% 39%	4048
January	1st to 10th	Night	14% 6% 2 5% 3 3 3 2 4 6% 51%	6489
	11th to 20th	Night	14% 8% 2 6% 4 3 4 2 4 5% 48%	6400
	21st to end	Night	17% 10% 3 6% 4 4 4 3 5% 6% 39%	6698
February	1st to 10th	Night	18% 8% 2 5% 4 4 3 3 5% 5% 41%	2544
	11th to 20th	Night	18% 7% 3 6% 5% 3 4 3 4 5% 41%	2338
	21st to end	Night	19% 7% 2 5% 4 4 3 4 4 5% 42%	1980
March	1st to 10th	Night	20% 9% 2 5% 3 3 3 3 4 5% 44%	5364
	11th to 20th	Night	15% 9% 2 6% 4 3 4 3 5% 5% 43%	5233
	21st to end	Night	19% 9% 2 7% 5% 3 4 3 5% 5% 39%	4962
April	1st to 10th	Night	20% 6% 3 7% 4 4 4 3 5% 6% 37%	2000
	11th to 20th	Night	20% 8% 3 5% 3 3 5% 3 6% 6% 39%	1975
	21st to end	Night	18% 8% 3 6% 4 3 4 3 4 6% 42%	1950
May	1st to 10th	Night	26% 10% 3 8% 4 4 3 3 5% 8% 26%	4054
	11th to 20th	Night	23% 10% 3 6% 4 3 4 3 4 5% 34%	3787
	21st to end	Night	23% 8% 2 6% 4 4 3 3 4 7% 35%	3926
June	1st to 10th	Night	17% 7% 2 4 5% 5% 4 3 5% 7% 40%	1600
	11th to 20th	Night	15% 8% 2 5% 4 4 4 5% 6% 9% 39%	1600
	21st to end	Night	10% 6% 2 7% 5% 4 6% 4 8% 9% 39%	1600
July	1st to 10th	Night	12% 9% 3 9% 6% 5% 5% 4 6% 8% 34%	3600
	11th to 20th	Night	15% 10% 3 9% 5% 4 5% 4 6% 8% 31%	3600
	21st to end	Night	13% 7% 2 6% 4 4 4 4 6% 8% 41%	3926
August	1st to 10th	Night	23% 7% 2 6% 4 5% 4 4 6% 8% 32%	2829
	11th to 20th	Night	14% 6% 3 7% 5% 5% 5% 4 6% 7% 39%	3197
	21st to end	Night	8% 5% 2 5% 4 4 4 3 6% 8% 52%	3586
September	1st to 10th	Night	14% 6% 2 6% 4 4 5% 4 6% 6% 44%	2000
	11th to 20th	Night	12% 5% 2 5% 4 3 3 3 5% 6% 51%	2112
	21st to end	Night	18% 6% 2 7% 5% 4 4 3 4 7% 41%	2200
October	1st to 10th	Night	19% 7% 2 6% 3 4 4 2 4 6% 43%	2263
	11th to 20th	Night	16% 5% 2 6% 3 3 4 3 4 6% 50%	2400
	21st to end	Night	20% 6% 2 6% 3 3 3 3 5% 5% 44%	2825
November	1st to 10th	Night	11% 6% 2 5% 4 4 3 3 4 6% 51%	2667
	11th to 20th	Night	19% 6% 2 5% 3 3 2 3 4 6% 49%	2730
	21st to end	Night	15% 5% 2 4 5% 3 4 4 5% 6% 47%	2756
December	1st to 10th	Night	16% 7% 2 5% 4 3 4 3 4 6% 48%	4720
	11th to 20th	Night	25% 7% 2 5% 2 3 3 3 3 5% 44%	5348
	21st to end	Night	19% 8% 2 6% 3 4 4 3 5% 5% 42%	7150

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	25% 27% 4 25% 18% 2	3678
	11th to 20th	Day	30% 26% 7% 19% 13% 6%	3648
	21st to end	Day	39% 28% 7% 17% 10% 1	4254
February	1st to 10th	Day	18% 62% 7% 8% 4	1855
	11th to 20th	Day	18% 60% 2 11% 9% 1	1957
	21st to end	Day	17% 62% 5% 9% 5% 1	1650
March	1st to 10th	Day	34% 30% 7% 11% 10% 8%	4479
	11th to 20th	Day	27% 30% 10% 22% 9% 2	4694
	21st to end	Day	32% 30% 8% 8% 18% 5%	5970
April	1st to 10th	Day	21% 62% 3 7% 5% 1	2400
	11th to 20th	Day	17% 62% 4 9% 7% 1	2374
	21st to end	Day	17% 62% 3 10% 7% 1	2450
May	1st to 10th	Day	41% 30% 14% 9% 5%	5897
	11th to 20th	Day	38% 29% 8% 14% 10% 1	6152
	21st to end	Day	35% 30% 7% 17% 10% 1	6949
June	1st to 10th	Day	17% 62% 4 9% 8%	2800
	11th to 20th	Day	16% 62% 5% 9% 7%	2800
	21st to end	Day	14% 61% 5% 10% 9% 1	2800
July	1st to 10th	Day	34% 31% 9% 16% 11%	6290
	11th to 20th	Day	33% 30% 15% 15% 6%	6285
	21st to end	Day	31% 28% 8% 17% 16% 1	6728
August	1st to 10th	Day	32% 38% 9% 15% 5% 1	4272
	11th to 20th	Day	25% 38% 9% 25% 4	3886
	21st to end	Day	18% 37% 8% 21% 15% 1	4312
September	1st to 10th	Day	16% 57% 7% 11% 8% 1	2400
	11th to 20th	Day	16% 58% 4 11% 12%	2286
	21st to end	Day	24% 57% 5% 8% 6%	2200
October	1st to 10th	Day	20% 38% 8% 10% 19% 5%	3472
	11th to 20th	Day	13% 36% 6% 15% 26% 4	3240
	21st to end	Day	13% 36% 11% 19% 19% 2	3227
November	1st to 10th	Day	19% 53% 8% 10% 10% 1	1851
	11th to 20th	Day	15% 54% 3 12% 14% 2	1890
	21st to end	Day	17% 54% 7% 15% 5% 2	1860
December	1st to 10th	Day	26% 35% 10% 20% 8% 1	2680
	11th to 20th	Day	30% 30% 8% 16% 14% 2	3066
	21st to end	Day	36% 26% 5% 17% 12% 2	4048
January	1st to 10th	Night	26% 25% 6% 20% 20% 3	6489
	11th to 20th	Night	29% 26% 10% 17% 14% 5%	6445
	21st to end	Night	38% 28% 6% 13% 12% 3	6698
February	1st to 10th	Night	18% 61% 6% 11% 3 1	2544
	11th to 20th	Night	18% 60% 2 9% 10% 2	2340
	21st to end	Night	18% 62% 4 7% 7% 2	1980
March	1st to 10th	Night	35% 29% 6% 13% 9% 8%	5374
	11th to 20th	Night	30% 30% 10% 19% 9% 3	5234
	21st to end	Night	36% 29% 4 8% 19% 4	4962
April	1st to 10th	Night	20% 61% 3 8% 6% 1	2000
	11th to 20th	Night	15% 63% 5% 9% 7% 1	1975
	21st to end	Night	17% 62% 3 9% 8% 1	1950
May	1st to 10th	Night	44% 30% 10% 9% 6% 1	4060
	11th to 20th	Night	41% 29% 10% 10% 9% 1	3788
	21st to end	Night	38% 29% 8% 16% 7% 1	3927
June	1st to 10th	Night	17% 61% 2 9% 10%	1600
	11th to 20th	Night	17% 63% 4 11% 6%	1600
	21st to end	Night	15% 62% 4 11% 7% 2	1600
July	1st to 10th	Night	37% 30% 8% 17% 8% 1	3560
	11th to 20th	Night	40% 28% 11% 15% 6%	3552
	21st to end	Night	30% 27% 11% 18% 13% 1	3809
August	1st to 10th	Night	37% 37% 11% 10% 5% 1	2819
	11th to 20th	Night	27% 38% 9% 20% 6%	3227
	21st to end	Night	16% 37% 7% 26% 13% 1	3586
September	1st to 10th	Night	16% 57% 5% 13% 8% 1	2000
	11th to 20th	Night	16% 57% 4 10% 11% 2	2112
	21st to end	Night	24% 57% 3 9% 6% 1	2200
October	1st to 10th	Night	24% 36% 7% 16% 15% 2	3705
	11th to 20th	Night	11% 36% 5% 19% 26% 3	3899
	21st to end	Night	15% 35% 8% 23% 16% 2	4563
November	1st to 10th	Night	18% 53% 5% 12% 10% 2	2667
	11th to 20th	Night	17% 54% 3 10% 13% 3	2730
	21st to end	Night	16% 54% 6% 15% 8% 1	2756
December	1st to 10th	Night	26% 34% 8% 23% 8% 1	4720
	11th to 20th	Night	33% 30% 5% 18% 11% 3	5348
	21st to end	Night	35% 26% 6% 15% 14% 4	7150

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	29% 25% 31% 14% 2	220
	11th to 20th	Day	26% 29% 30% 13% 2	212
	21st to end	Day	23% 24% 37% 11% 4 1	283
February	1st to 10th	Day	27% 22% 37% 12% 2	355
	11th to 20th	Day	27% 21% 38% 13% 2	496
	21st to end	Day	28% 21% 34% 13% 4	414
March	1st to 10th	Day	24% 23% 33% 17% 3	500
	11th to 20th	Day	22% 22% 36% 16% 4 1	500
	21st to end	Day	30% 19% 33% 13% 4 1	550
April	1st to 10th	Day	28% 22% 31% 13% 5% 1	500
	11th to 20th	Day	26% 19% 32% 16% 6% 1	492
	21st to end	Day	28% 18% 33% 15% 4 1	500
May	1st to 10th	Day	30% 19% 30% 16% 5% 1	503
	11th to 20th	Day	21% 17% 35% 20% 6% 1	527
	21st to end	Day	20% 10% 31% 25% 12% 2	573
June	1st to 10th	Day	19% 11% 32% 27% 9% 2	530
	11th to 20th	Day	18% 11% 34% 27% 9% 2	530
	21st to end	Day	13% 10% 35% 28% 12% 2	530
July	1st to 10th	Day	12% 9% 26% 34% 14% 5%	525
	11th to 20th	Day	10% 6% 30% 34% 16% 4	524
	21st to end	Day	13% 10% 31% 30% 13% 3	576
August	1st to 10th	Day	13% 7% 28% 32% 14% 5%	526
	11th to 20th	Day	14% 5% 27% 35% 15% 4	519
	21st to end	Day	11% 8% 31% 30% 13% 6%	583
September	1st to 10th	Day	19% 7% 30% 24% 15% 4	530
	11th to 20th	Day	14% 7% 31% 25% 14% 9%	530
	21st to end	Day	23% 9% 30% 23% 11% 4	530
October	1st to 10th	Day	23% 10% 26% 21% 15% 5%	530
	11th to 20th	Day	19% 15% 31% 21% 11% 2	530
	21st to end	Day	22% 14% 35% 18% 9% 2	481
November	1st to 10th	Day	16% 16% 32% 25% 9% 2	425
	11th to 20th	Day	23% 23% 29% 18% 5% 1	430
	21st to end	Day	24% 18% 29% 22% 6% 1	400
December	1st to 10th	Day	26% 22% 33% 15% 4	220
	11th to 20th	Day	35% 20% 32% 10% 3	220
	21st to end	Day	29% 17% 36% 12% 7%	242
January	1st to 10th	Night	20% 21% 36% 19% 3	840
	11th to 20th	Night	26% 19% 29% 23% 3	825
	21st to end	Night	19% 20% 38% 21% 2	880
February	1st to 10th	Night	22% 18% 36% 22% 2	800
	11th to 20th	Night	25% 21% 37% 16% 2	783
	21st to end	Night	23% 21% 35% 17% 3	660
March	1st to 10th	Night	24% 18% 34% 19% 5%	800
	11th to 20th	Night	22% 17% 38% 19% 4 1	800
	21st to end	Night	23% 17% 36% 20% 4	880
April	1st to 10th	Night	25% 18% 34% 19% 5%	800
	11th to 20th	Night	23% 15% 34% 24% 5%	791
	21st to end	Night	22% 15% 33% 24% 5% 1	750
May	1st to 10th	Night	25% 11% 33% 24% 7% 1	600
	11th to 20th	Night	23% 14% 34% 26% 3	489
	21st to end	Night	22% 6% 23% 35% 12% 1	433
June	1st to 10th	Night	19% 7% 28% 33% 12% 1	400
	11th to 20th	Night	15% 8% 25% 38% 13% 1	400
	21st to end	Night	12% 6% 27% 45% 10% 1	400
July	1st to 10th	Night	12% 4 24% 43% 15% 1	390
	11th to 20th	Night	15% 4 22% 41% 15% 2	388
	21st to end	Night	12% 5% 23% 43% 16%	438
August	1st to 10th	Night	12% 3 26% 41% 17% 1	537
	11th to 20th	Night	15% 4 21% 37% 21% 2	790
	21st to end	Night	14% 5% 20% 38% 21% 2	880
September	1st to 10th	Night	16% 6% 25% 34% 17% 2	800
	11th to 20th	Night	15% 5% 23% 33% 19% 5%	800
	21st to end	Night	21% 6% 26% 30% 16% 2	800
October	1st to 10th	Night	22% 9% 24% 27% 15% 3	800
	11th to 20th	Night	18% 13% 28% 29% 11% 1	800
	21st to end	Night	24% 13% 31% 24% 8%	880
November	1st to 10th	Night	16% 13% 33% 26% 10% 1	820
	11th to 20th	Night	22% 15% 33% 21% 7%	840
	21st to end	Night	20% 18% 31% 25% 6% 1	840
December	1st to 10th	Night	26% 17% 33% 18% 5% 1	840
	11th to 20th	Night	25% 16% 35% 20% 4	840
	21st to end	Night	24% 16% 35% 21% 3	924

Page generated at 2026-01-14 01:14:31. Version ac07

Copyright © 2026 Attilla Danko.