Clayton Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clayton Lake State Park clear sky chart from 2005-11-06 to 2026-05-02.

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	4 4 1 4 3 3 4 3 6% 7% 60%	140146
	Night	4 4 2 4 3 3 4 3 5% 7% 59%	139785
Transparency	Day	21% 5% 10% 21% 28% 15%	135215
	Night	23% 5% 9% 21% 27% 15%	135723
Seeing	Day	7% 9% 30% 32% 17% 4	17320
	Night	6% 8% 37% 36% 11% 1	27419

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	3 7% 2 7% 3 3 3 3 5% 7% 56%	4720
	11th to 20th	Day	1 4 2 5% 2 2 2 2 4 5% 70%	4938
	21st to end	Day	4 6% 2 4 3 3 3 3 4 5% 63%	5958
February	1st to 10th	Day	2 5% 2 5% 3 4 4 3 5% 7% 59%	2100
	11th to 20th	Day	2 6% 2 6% 4 4 4 3 4 6% 58%	2049
	21st to end	Day	2 3 1 4 2 2 3 3 4 6% 68%	1730
March	1st to 10th	Day	3 5% 2 3 3 3 3 2 4 5% 67%	4600
	11th to 20th	Day	6% 7% 2 6% 3 3 4 3 4 6% 57%	4772
	21st to end	Day	2 5% 1 4 3 4 4 3 6% 8% 60%	6101
April	1st to 10th	Day	3 4 1 4 3 2 4 3 5% 6% 64%	2520
	11th to 20th	Day	5% 5% 2 5% 3 3 3 4 4 7% 60%	2491
	21st to end	Day	6% 4 1 4 3 3 3 3 6% 8% 59%	2520
May	1st to 10th	Day	11% 5% 1 4 3 3 4 3 5% 7% 55%	5790
	11th to 20th	Day	5% 3 1 4 3 3 3 3 5% 6% 64%	5862
	21st to end	Day	6% 4 1 4 2 3 4 4 7% 8% 58%	6571
June	1st to 10th	Day	4 3 1 3 3 3 6% 5% 9% 10% 54%	2800
	11th to 20th	Day	3 2 1 3 2 3 4 4 6% 8% 64%	2800
	21st to end	Day	5% 4 2 5% 3 4 5% 5% 8% 8% 52%	2800
July	1st to 10th	Day	4 3 1 4 4 5% 6% 5% 7% 10% 52%	6339
	11th to 20th	Day	2 3 1 3 3 5% 5% 5% 7% 11% 55%	6340
	21st to end	Day	4 3 1 5% 4 5% 6% 5% 8% 10% 50%	6626
August	1st to 10th	Day	4 4 2 5% 4 5% 6% 5% 8% 11% 48%	5348
	11th to 20th	Day	3 2 1 4 4 4 5% 5% 8% 11% 54%	5366
	21st to end	Day	4 4 2 5% 4 5% 5% 5% 7% 10% 50%	5984
September	1st to 10th	Day	5% 4 2 5% 3 3 4 3 6% 9% 57%	2400
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 8% 61%	2275
	21st to end	Day	5% 3 1 3 2 2 3 3 5% 6% 68%	2200
October	1st to 10th	Day	4 3 1 4 2 2 3 2 4 4 73%	3590
	11th to 20th	Day	6% 4 2 3 2 3 3 2 4 5% 65%	3260
	21st to end	Day	3 4 1 2 2 1 2 1 2 4 78%	3360
November	1st to 10th	Day	3 3 1 2 2 2 3 3 4 6% 72%	1853
	11th to 20th	Day	2 3 1 3 2 2 3 2 4 5% 71%	1890
	21st to end	Day	5% 6% 1 3 3 2 2 2 3 6% 66%	1890
December	1st to 10th	Day	1 3 1 3 2 2 2 2 3 5% 76%	3030
	11th to 20th	Day	2 3 1 4 3 3 3 3 5% 7% 66%	3181
	21st to end	Day	2 4 1 5% 3 3 3 3 4 6% 67%	4092
January	1st to 10th	Night	2 7% 3 7% 4 4 4 3 5% 6% 54%	8201
	11th to 20th	Night	1 4 2 5% 3 3 3 3 3 6% 68%	8093
	21st to end	Night	3 5% 2 6% 4 3 3 3 4 6% 60%	8240
February	1st to 10th	Night	3 5% 2 5% 3 3 4 3 5% 7% 61%	2520
	11th to 20th	Night	4 7% 2 6% 5% 3 4 3 6% 6% 54%	2458
	21st to end	Night	4 4 1 3 2 2 3 3 5% 7% 66%	2076
March	1st to 10th	Night	4 4 2 3 3 2 2 2 3 5% 68%	5494
	11th to 20th	Night	5% 6% 2 6% 4 3 4 3 4 5% 58%	5412
	21st to end	Night	3 5% 1 4 3 3 4 3 5% 8% 61%	5094
April	1st to 10th	Night	4 4 1 3 2 3 3 3 5% 6% 64%	2100
	11th to 20th	Night	5% 5% 2 4 3 3 4 3 5% 7% 58%	2077
	21st to end	Night	7% 5% 2 4 3 3 3 3 6% 6% 59%	2100
May	1st to 10th	Night	12% 6% 2 4 2 2 3 3 4 5% 57%	4210
	11th to 20th	Night	7% 4 1 3 2 3 3 3 5% 6% 63%	4053
	21st to end	Night	9% 4 1 4 3 4 4 3 5% 7% 57%	4321
June	1st to 10th	Night	5% 3 1 5% 3 4 4 5% 8% 10% 52%	1600
	11th to 20th	Night	2 2 1 4 3 4 4 4 6% 8% 62%	1600
	21st to end	Night	4 4 2 6% 4 3 6% 5% 8% 10% 49%	1600
July	1st to 10th	Night	6% 5% 2 4 4 4 5% 5% 7% 11% 48%	3640
	11th to 20th	Night	2 3 2 6% 4 5% 6% 4 8% 15% 45%	3640
	21st to end	Night	6% 4 2 6% 5% 5% 6% 5% 9% 13% 40%	4240
August	1st to 10th	Night	6% 5% 2 5% 4 4 5% 4 7% 12% 47%	4464
	11th to 20th	Night	3 3 1 4 4 5% 7% 6% 10% 14% 41%	4483
	21st to end	Night	8% 7% 3 6% 5% 5% 6% 5% 7% 9% 39%	4993
September	1st to 10th	Night	5% 4 1 4 3 4 4 4 6% 9% 57%	2000
	11th to 20th	Night	6% 4 2 3 2 3 4 3 5% 7% 60%	2124
	21st to end	Night	5% 3 1 4 3 3 3 2 4 6% 65%	2200
October	1st to 10th	Night	5% 2 1 3 2 2 3 3 4 5% 69%	3590
	11th to 20th	Night	9% 2 1 3 2 3 4 3 5% 7% 61%	3883
	21st to end	Night	5% 3 1 2 2 2 3 2 3 5% 73%	4405
November	1st to 10th	Night	3 3 1 2 2 2 2 3 4 6% 71%	2665
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 5% 74%	2730
	21st to end	Night	3 4 2 3 2 3 2 3 5% 7% 65%	2730
December	1st to 10th	Night	1 5% 2 4 2 2 3 2 4 5% 72%	4380
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 7% 69%	5241
	21st to end	Night	2 4 2 5% 4 4 4 3 5% 6% 61%	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	28% 5% 4 21% 33% 9%	4723
	11th to 20th	Day	17% 3 10% 18% 31% 19%	4938
	21st to end	Day	23% 4 5% 17% 38% 13%	5958
February	1st to 10th	Day	23% 5% 9% 22% 25% 16%	2100
	11th to 20th	Day	25% 4 9% 23% 25% 14%	2059
	21st to end	Day	17% 3 6% 20% 30% 26%	1730
March	1st to 10th	Day	20% 3 4 11% 30% 32%	4600
	11th to 20th	Day	27% 5% 5% 15% 30% 18%	4772
	21st to end	Day	20% 5% 7% 27% 34% 7%	6101
April	1st to 10th	Day	19% 4 8% 20% 30% 18%	2520
	11th to 20th	Day	24% 5% 8% 21% 22% 20%	2494
	21st to end	Day	22% 5% 10% 23% 28% 12%	2520
May	1st to 10th	Day	27% 6% 12% 20% 20% 14%	5790
	11th to 20th	Day	20% 5% 8% 15% 22% 30%	5866
	21st to end	Day	21% 7% 12% 19% 19% 21%	6572
June	1st to 10th	Day	20% 9% 17% 23% 20% 12%	2800
	11th to 20th	Day	15% 5% 11% 19% 27% 23%	2800
	21st to end	Day	25% 7% 11% 22% 20% 15%	2800
July	1st to 10th	Day	24% 8% 14% 22% 25% 7%	6271
	11th to 20th	Day	20% 7% 17% 28% 23% 5%	6265
	21st to end	Day	25% 8% 16% 24% 22% 5%	6432
August	1st to 10th	Day	29% 8% 18% 21% 18% 5%	3892
	11th to 20th	Day	22% 7% 12% 22% 28% 9%	3882
	21st to end	Day	23% 7% 15% 25% 24% 6%	4311
September	1st to 10th	Day	23% 6% 12% 23% 22% 14%	2400
	11th to 20th	Day	22% 5% 9% 21% 25% 18%	2275
	21st to end	Day	18% 3 9% 20% 34% 17%	2200
October	1st to 10th	Day	17% 3 5% 17% 36% 21%	3590
	11th to 20th	Day	23% 3 9% 17% 31% 17%	3260
	21st to end	Day	14% 1 4 16% 43% 22%	3360
November	1st to 10th	Day	14% 4 7% 21% 31% 23%	1853
	11th to 20th	Day	16% 3 5% 24% 34% 18%	1890
	21st to end	Day	21% 2 7% 17% 29% 23%	1890
December	1st to 10th	Day	13% 2 6% 25% 39% 14%	3030
	11th to 20th	Day	18% 3 4 18% 42% 15%	3179
	21st to end	Day	18% 5% 7% 25% 28% 17%	4092
January	1st to 10th	Night	30% 4 5% 25% 28% 8%	8202
	11th to 20th	Night	19% 4 8% 20% 31% 18%	8093
	21st to end	Night	25% 5% 7% 16% 34% 13%	8240
February	1st to 10th	Night	22% 4 8% 21% 29% 15%	2520
	11th to 20th	Night	30% 5% 8% 21% 24% 13%	2458
	21st to end	Night	18% 3 5% 20% 34% 21%	2076
March	1st to 10th	Night	20% 2 4 13% 28% 33%	5494
	11th to 20th	Night	26% 6% 7% 16% 24% 21%	5412
	21st to end	Night	20% 5% 9% 28% 27% 11%	5094
April	1st to 10th	Night	20% 4 8% 23% 27% 17%	2100
	11th to 20th	Night	24% 5% 11% 22% 23% 16%	2077
	21st to end	Night	24% 7% 13% 24% 20% 13%	2100
May	1st to 10th	Night	28% 6% 9% 22% 17% 18%	4207
	11th to 20th	Night	20% 7% 9% 19% 18% 27%	4054
	21st to end	Night	26% 7% 12% 16% 15% 24%	4322
June	1st to 10th	Night	24% 9% 18% 25% 12% 12%	1600
	11th to 20th	Night	18% 7% 14% 20% 20% 21%	1600
	21st to end	Night	26% 9% 13% 23% 17% 12%	1600
July	1st to 10th	Night	28% 9% 15% 24% 19% 6%	3600
	11th to 20th	Night	26% 8% 19% 29% 16% 3	3592
	21st to end	Night	31% 8% 17% 25% 14% 4	4121
August	1st to 10th	Night	34% 8% 17% 20% 17% 4	3244
	11th to 20th	Night	27% 9% 14% 26% 20% 4	3243
	21st to end	Night	33% 8% 13% 25% 17% 4	3597
September	1st to 10th	Night	24% 7% 16% 21% 22% 10%	2000
	11th to 20th	Night	23% 5% 12% 22% 23% 16%	2124
	21st to end	Night	20% 4 8% 21% 32% 14%	2200
October	1st to 10th	Night	18% 4 6% 17% 36% 19%	3590
	11th to 20th	Night	24% 3 8% 19% 27% 19%	3883
	21st to end	Night	16% 2 4 19% 40% 19%	4405
November	1st to 10th	Night	15% 3 8% 19% 32% 23%	2665
	11th to 20th	Night	14% 3 5% 24% 38% 17%	2730
	21st to end	Night	19% 3 7% 20% 28% 22%	2730
December	1st to 10th	Night	17% 3 6% 24% 41% 10%	4380
	11th to 20th	Night	16% 3 4 20% 39% 17%	5242
	21st to end	Night	21% 6% 8% 21% 29% 15%	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	7% 12% 34% 36% 10% 2	330
	11th to 20th	Day	7% 13% 38% 27% 12% 3	330
	21st to end	Day	5% 13% 36% 30% 13% 2	363
February	1st to 10th	Day	5% 15% 45% 24% 10% 1	330
	11th to 20th	Day	9% 12% 48% 22% 7% 2	330
	21st to end	Day	8% 13% 44% 29% 6%	273
March	1st to 10th	Day	6% 13% 44% 28% 8% 1	330
	11th to 20th	Day	14% 16% 33% 26% 10% 1	369
	21st to end	Day	12% 22% 37% 20% 8% 1	594
April	1st to 10th	Day	8% 21% 38% 24% 8% 1	540
	11th to 20th	Day	12% 22% 39% 21% 5% 1	532
	21st to end	Day	15% 19% 37% 22% 6% 1	540
May	1st to 10th	Day	9% 13% 38% 28% 11% 2	650
	11th to 20th	Day	9% 10% 37% 28% 13% 4	725
	21st to end	Day	8% 10% 38% 32% 10% 1	789
June	1st to 10th	Day	6% 6% 27% 35% 22% 5%	730
	11th to 20th	Day	5% 5% 32% 37% 18% 3	730
	21st to end	Day	7% 5% 25% 38% 19% 5%	730
July	1st to 10th	Day	7% 2 17% 38% 28% 7%	721
	11th to 20th	Day	3 1 11% 42% 33% 10%	718
	21st to end	Day	5% 1 10% 40% 34% 11%	738
August	1st to 10th	Day	5% 2 15% 37% 31% 10%	527
	11th to 20th	Day	4 3 16% 44% 25% 7%	517
	21st to end	Day	5% 2 14% 46% 25% 8%	583
September	1st to 10th	Day	7% 1 21% 39% 26% 6%	530
	11th to 20th	Day	5% 2 24% 39% 20% 9%	405
	21st to end	Day	8% 4 25% 30% 25% 8%	330
October	1st to 10th	Day	9% 8% 25% 34% 18% 6%	330
	11th to 20th	Day	6% 9% 33% 29% 16% 7%	330
	21st to end	Day	11% 9% 28% 31% 16% 5%	363
November	1st to 10th	Day	8% 10% 31% 34% 13% 4	330
	11th to 20th	Day	7% 11% 27% 35% 17% 3	330
	21st to end	Day	10% 14% 38% 22% 12% 5%	330
December	1st to 10th	Day	4 11% 40% 31% 12% 3	330
	11th to 20th	Day	8% 11% 37% 32% 12% 1	330
	21st to end	Day	9% 14% 39% 29% 7% 1	363
January	1st to 10th	Night	5% 10% 40% 35% 8% 1	1050
	11th to 20th	Night	5% 9% 41% 34% 9% 2	997
	21st to end	Night	5% 7% 47% 31% 10% 1	924
February	1st to 10th	Night	4 11% 46% 30% 9%	840
	11th to 20th	Night	8% 13% 51% 22% 6% 1	824
	21st to end	Night	8% 11% 53% 25% 3	692
March	1st to 10th	Night	6% 13% 46% 30% 5%	840
	11th to 20th	Night	8% 13% 38% 33% 7% 1	821
	21st to end	Night	6% 13% 54% 22% 5%	693
April	1st to 10th	Night	6% 12% 51% 27% 3	630
	11th to 20th	Night	8% 15% 51% 25% 2	623
	21st to end	Night	9% 12% 43% 31% 5%	630
May	1st to 10th	Night	9% 12% 39% 33% 6%	603
	11th to 20th	Night	9% 8% 38% 33% 11% 1	591
	21st to end	Night	7% 9% 46% 30% 7% 1	650
June	1st to 10th	Night	5% 6% 33% 41% 14% 1	600
	11th to 20th	Night	3 5% 45% 38% 9%	600
	21st to end	Night	5% 4 33% 43% 15%	600
July	1st to 10th	Night	5% 2 20% 51% 19% 2	585
	11th to 20th	Night	3 2 15% 50% 27% 2	582
	21st to end	Night	8% 2 14% 48% 27% 2	657
August	1st to 10th	Night	6% 1 16% 43% 31% 3	597
	11th to 20th	Night	8% 1 13% 54% 23% 1	594
	21st to end	Night	6% 2 17% 49% 23% 2	660
September	1st to 10th	Night	7% 2 19% 53% 19% 1	600
	11th to 20th	Night	9% 2 32% 40% 15% 1	600
	21st to end	Night	7% 6% 29% 40% 16% 2	600
October	1st to 10th	Night	10% 6% 32% 41% 11% 1	600
	11th to 20th	Night	5% 6% 41% 32% 12% 3	785
	21st to end	Night	8% 8% 34% 34% 13% 3	971
November	1st to 10th	Night	5% 7% 35% 40% 10% 2	1025
	11th to 20th	Night	4 8% 41% 36% 11% 1	1050
	21st to end	Night	6% 10% 35% 36% 13% 1	1050
December	1st to 10th	Night	4 9% 40% 35% 11% 1	1050
	11th to 20th	Night	6% 9% 39% 37% 8% 1	1050
	21st to end	Night	6% 13% 41% 31% 8% 1	1155

Page generated at 2026-04-29 00:21:47. Version ac07

Copyright © 2026 Attilla Danko.