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 2025-01-07.

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 4 6% 7% 60%	108782
	Night	4 4 2 4 3 3 4 3 5% 7% 60%	108965
Transparency	Day	21% 6% 10% 21% 28% 14%	108530
	Night	22% 6% 10% 22% 26% 14%	108807
Seeing	Day	7% 9% 29% 33% 18% 5%	15569
	Night	6% 8% 37% 36% 12% 1	25655

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	2 5% 2 6% 3 4 3 3 5% 7% 59%	2586
	11th to 20th	Day	2 3 1 4 3 3 3 3 5% 6% 67%	2640
	21st to end	Day	4 6% 2 5% 4 3 3 4 6% 6% 58%	3208
February	1st to 10th	Day	3 5% 2 5% 3 4 4 3 5% 7% 58%	1900
	11th to 20th	Day	3 6% 2 6% 3 3 4 3 4 6% 60%	1849
	21st to end	Day	2 4 1 4 2 3 4 3 4 7% 66%	1570
March	1st to 10th	Day	2 4 2 3 3 3 3 2 5% 6% 67%	3130
	11th to 20th	Day	8% 7% 2 5% 3 3 4 3 4 6% 54%	3258
	21st to end	Day	3 7% 2 4 4 4 4 3 6% 8% 56%	4165
April	1st to 10th	Day	3 4 1 3 3 2 4 3 5% 6% 65%	2280
	11th to 20th	Day	6% 5% 2 5% 3 3 3 4 4 7% 59%	2251
	21st to end	Day	6% 5% 1 4 3 3 4 3 6% 8% 58%	2280
May	1st to 10th	Day	7% 6% 1 4 3 3 3 3 5% 6% 59%	4039
	11th to 20th	Day	8% 4 2 5% 4 3 3 4 6% 7% 55%	4082
	21st to end	Day	4 3 1 3 2 3 4 4 7% 7% 63%	4575
June	1st to 10th	Day	4 3 1 3 3 3 5% 5% 9% 10% 55%	2660
	11th to 20th	Day	3 2 1 3 2 3 4 4 6% 8% 63%	2660
	21st to end	Day	4 4 2 5% 3 4 5% 5% 8% 8% 52%	2660
July	1st to 10th	Day	5% 4 1 4 4 5% 6% 5% 7% 9% 52%	4430
	11th to 20th	Day	2 2 1 4 4 5% 5% 5% 7% 11% 55%	4430
	21st to end	Day	4 3 1 4 4 4 6% 5% 8% 10% 49%	4606
August	1st to 10th	Day	5% 4 2 5% 4 5% 5% 4 7% 10% 47%	3784
	11th to 20th	Day	3 2 2 4 4 4 4 5% 7% 9% 56%	3726
	21st to end	Day	3 3 1 4 4 5% 5% 5% 7% 10% 54%	4180
September	1st to 10th	Day	5% 4 2 5% 3 3 4 3 6% 8% 57%	2280
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 8% 61%	2161
	21st to end	Day	5% 3 1 3 2 2 3 2 4 6% 69%	2090
October	1st to 10th	Day	4 3 1 4 2 2 3 2 4 4 72%	3480
	11th to 20th	Day	6% 4 2 3 2 3 3 2 4 5% 65%	3160
	21st to end	Day	3 4 1 2 2 1 1 1 2 4 78%	3256
November	1st to 10th	Day	3 3 1 2 2 2 3 3 4 6% 71%	1763
	11th to 20th	Day	2 4 1 3 2 2 3 2 4 5% 71%	1800
	21st to end	Day	5% 6% 1 4 3 2 2 3 3 6% 66%	1800
December	1st to 10th	Day	1 3 1 3 2 2 2 2 3 5% 77%	2940
	11th to 20th	Day	2 3 1 4 3 3 3 3 5% 7% 66%	3099
	21st to end	Day	2 4 1 5% 3 3 3 3 4 6% 67%	4004
January	1st to 10th	Night	2 5% 2 6% 5% 5% 4 4 5% 5% 55%	4502
	11th to 20th	Night	2 4 2 4 3 4 4 4 5% 7% 62%	4357
	21st to end	Night	2 5% 2 5% 3 3 3 3 5% 7% 60%	4456
February	1st to 10th	Night	3 5% 2 5% 3 3 5% 3 5% 7% 60%	2280
	11th to 20th	Night	4 7% 2 6% 5% 4 4 3 5% 6% 55%	2218
	21st to end	Night	5% 4 1 3 2 2 3 3 5% 8% 64%	1884
March	1st to 10th	Night	3 4 2 4 3 2 2 3 4 5% 69%	3734
	11th to 20th	Night	6% 6% 2 7% 4 3 4 3 4 6% 54%	3695
	21st to end	Night	4 7% 1 5% 3 3 3 3 5% 7% 58%	3477
April	1st to 10th	Night	4 4 1 3 2 3 3 3 5% 7% 65%	1900
	11th to 20th	Night	5% 5% 2 5% 4 3 3 3 6% 8% 57%	1877
	21st to end	Night	7% 5% 1 4 3 3 3 4 6% 6% 59%	1900
May	1st to 10th	Night	7% 5% 1 3 2 3 3 3 4 5% 64%	2928
	11th to 20th	Night	9% 5% 1 5% 3 4 4 4 5% 7% 51%	2823
	21st to end	Night	6% 3 1 3 3 3 4 4 5% 7% 61%	3007
June	1st to 10th	Night	5% 3 1 4 3 4 4 5% 8% 10% 53%	1520
	11th to 20th	Night	2 2 1 4 3 4 4 4 6% 8% 63%	1520
	21st to end	Night	4 4 2 5% 4 3 6% 5% 8% 10% 49%	1520
July	1st to 10th	Night	5% 5% 1 3 4 4 5% 5% 7% 11% 50%	2540
	11th to 20th	Night	3 3 2 6% 4 4 5% 4 8% 13% 49%	2540
	21st to end	Night	7% 4 2 6% 4 5% 5% 5% 8% 10% 45%	2950
August	1st to 10th	Night	8% 5% 2 6% 5% 5% 5% 4 7% 12% 41%	3155
	11th to 20th	Night	4 3 1 5% 4 5% 6% 6% 10% 13% 42%	3113
	21st to end	Night	3 4 2 6% 5% 5% 7% 7% 9% 10% 42%	3487
September	1st to 10th	Night	5% 4 1 4 3 4 4 4 5% 9% 58%	1900
	11th to 20th	Night	6% 4 2 3 3 3 4 3 5% 7% 60%	2018
	21st to end	Night	5% 3 1 4 3 3 3 2 4 5% 66%	2090
October	1st to 10th	Night	5% 2 1 3 2 2 3 3 4 5% 69%	3480
	11th to 20th	Night	9% 2 1 3 2 3 3 3 5% 7% 61%	3764
	21st to end	Night	5% 3 1 2 2 2 3 2 3 5% 73%	4268
November	1st to 10th	Night	3 3 1 3 2 2 2 3 4 6% 71%	2535
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 4 74%	2600
	21st to end	Night	3 5% 2 3 2 3 2 3 5% 6% 65%	2600
December	1st to 10th	Night	1 5% 2 3 2 2 3 2 3 5% 72%	4250
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 7% 69%	5103
	21st to end	Night	2 4 2 5% 4 4 5% 3 5% 6% 60%	6974

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	23% 7% 7% 25% 31% 9%	2587
	11th to 20th	Day	16% 4 15% 25% 32% 8%	2640
	21st to end	Day	24% 6% 8% 26% 28% 8%	3208
February	1st to 10th	Day	24% 5% 10% 22% 25% 14%	1900
	11th to 20th	Day	25% 4 9% 23% 24% 15%	1859
	21st to end	Day	18% 3 6% 20% 30% 23%	1570
March	1st to 10th	Day	18% 4 6% 15% 32% 26%	3130
	11th to 20th	Day	28% 7% 7% 20% 28% 10%	3258
	21st to end	Day	23% 7% 9% 21% 32% 9%	4165
April	1st to 10th	Day	19% 5% 9% 20% 28% 19%	2280
	11th to 20th	Day	25% 5% 8% 21% 22% 19%	2254
	21st to end	Day	23% 6% 10% 24% 27% 11%	2280
May	1st to 10th	Day	23% 7% 10% 19% 20% 20%	4039
	11th to 20th	Day	26% 7% 11% 21% 22% 13%	4086
	21st to end	Day	16% 8% 13% 17% 22% 24%	4575
June	1st to 10th	Day	19% 9% 17% 23% 20% 12%	2660
	11th to 20th	Day	15% 6% 11% 18% 26% 24%	2660
	21st to end	Day	25% 7% 12% 22% 19% 15%	2660
July	1st to 10th	Day	25% 8% 12% 23% 24% 8%	4361
	11th to 20th	Day	19% 8% 16% 22% 28% 7%	4355
	21st to end	Day	25% 8% 14% 21% 25% 7%	4459
August	1st to 10th	Day	29% 9% 18% 21% 18% 6%	3772
	11th to 20th	Day	22% 7% 12% 22% 28% 9%	3762
	21st to end	Day	23% 7% 15% 25% 25% 6%	4179
September	1st to 10th	Day	24% 6% 11% 22% 22% 15%	2280
	11th to 20th	Day	23% 5% 9% 20% 25% 19%	2161
	21st to end	Day	18% 3 8% 20% 34% 17%	2090
October	1st to 10th	Day	17% 3 5% 17% 36% 21%	3480
	11th to 20th	Day	23% 3 9% 17% 31% 17%	3160
	21st to end	Day	14% 1 4 16% 43% 23%	3256
November	1st to 10th	Day	15% 4 7% 20% 31% 24%	1763
	11th to 20th	Day	16% 3 6% 25% 33% 18%	1800
	21st to end	Day	21% 3 7% 15% 30% 24%	1800
December	1st to 10th	Day	12% 2 6% 26% 39% 15%	2940
	11th to 20th	Day	18% 3 5% 18% 41% 14%	3097
	21st to end	Day	18% 5% 7% 25% 29% 16%	4004
January	1st to 10th	Night	27% 6% 8% 25% 27% 7%	4502
	11th to 20th	Night	20% 6% 11% 25% 26% 11%	4357
	21st to end	Night	21% 7% 11% 23% 31% 7%	4456
February	1st to 10th	Night	23% 5% 9% 21% 29% 13%	2280
	11th to 20th	Night	30% 5% 8% 21% 24% 13%	2218
	21st to end	Night	19% 2 5% 20% 33% 20%	1884
March	1st to 10th	Night	18% 3 6% 17% 25% 31%	3734
	11th to 20th	Night	28% 8% 9% 21% 22% 13%	3695
	21st to end	Night	23% 6% 9% 23% 26% 12%	3477
April	1st to 10th	Night	18% 4 9% 23% 26% 19%	1900
	11th to 20th	Night	24% 6% 12% 22% 22% 15%	1877
	21st to end	Night	24% 7% 14% 25% 18% 13%	1900
May	1st to 10th	Night	22% 7% 10% 21% 16% 26%	2928
	11th to 20th	Night	28% 9% 12% 23% 16% 12%	2824
	21st to end	Night	20% 8% 13% 15% 19% 25%	3008
June	1st to 10th	Night	23% 9% 17% 26% 13% 12%	1520
	11th to 20th	Night	18% 6% 13% 19% 21% 22%	1520
	21st to end	Night	25% 9% 13% 23% 17% 12%	1520
July	1st to 10th	Night	26% 8% 16% 25% 18% 7%	2500
	11th to 20th	Night	24% 8% 18% 25% 21% 4	2492
	21st to end	Night	31% 8% 15% 22% 18% 6%	2858
August	1st to 10th	Night	34% 8% 17% 20% 17% 4	3144
	11th to 20th	Night	27% 9% 14% 26% 20% 4	3143
	21st to end	Night	32% 8% 13% 25% 17% 4	3487
September	1st to 10th	Night	24% 7% 16% 21% 22% 11%	1900
	11th to 20th	Night	23% 5% 12% 21% 23% 16%	2018
	21st to end	Night	20% 4 8% 20% 33% 14%	2090
October	1st to 10th	Night	18% 4 6% 17% 36% 19%	3480
	11th to 20th	Night	24% 3 8% 19% 28% 18%	3764
	21st to end	Night	17% 2 3 19% 40% 19%	4268
November	1st to 10th	Night	15% 4 8% 19% 31% 23%	2535
	11th to 20th	Night	14% 3 5% 24% 37% 17%	2600
	21st to end	Night	20% 4 6% 19% 29% 23%	2600
December	1st to 10th	Night	16% 3 6% 24% 41% 10%	4250
	11th to 20th	Night	16% 3 4 20% 39% 17%	5104
	21st to end	Night	22% 6% 8% 21% 29% 14%	6974

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% 10% 34% 37% 10% 2	288
	11th to 20th	Day	9% 13% 36% 27% 13% 2	270
	21st to end	Day	4 12% 35% 30% 15% 3	297
February	1st to 10th	Day	6% 14% 43% 25% 10% 1	270
	11th to 20th	Day	7% 11% 47% 24% 8% 2	270
	21st to end	Day	10% 16% 45% 25% 4	225
March	1st to 10th	Day	4 13% 45% 29% 8% 1	270
	11th to 20th	Day	13% 16% 32% 26% 11% 1	305
	21st to end	Day	13% 23% 37% 19% 8% 1	506
April	1st to 10th	Day	7% 21% 40% 24% 7% 1	460
	11th to 20th	Day	12% 21% 38% 21% 6% 1	452
	21st to end	Day	14% 19% 36% 23% 7% 1	460
May	1st to 10th	Day	8% 14% 39% 28% 10% 2	598
	11th to 20th	Day	9% 9% 36% 28% 14% 4	675
	21st to end	Day	7% 10% 39% 32% 11% 1	734
June	1st to 10th	Day	5% 6% 26% 36% 22% 5%	680
	11th to 20th	Day	6% 4 32% 38% 18% 3	680
	21st to end	Day	7% 5% 24% 39% 20% 5%	680
July	1st to 10th	Day	7% 2 17% 37% 29% 8%	671
	11th to 20th	Day	3 1 11% 42% 33% 11%	668
	21st to end	Day	5% 1 8% 39% 35% 11%	686
August	1st to 10th	Day	5% 3 13% 37% 32% 11%	487
	11th to 20th	Day	4 3 17% 44% 25% 7%	477
	21st to end	Day	4 2 13% 47% 26% 9%	539
September	1st to 10th	Day	6% 1 20% 40% 26% 7%	490
	11th to 20th	Day	6% 2 23% 39% 22% 9%	371
	21st to end	Day	9% 4 24% 29% 26% 9%	300
October	1st to 10th	Day	10% 7% 24% 34% 20% 6%	300
	11th to 20th	Day	6% 7% 31% 30% 18% 7%	300
	21st to end	Day	12% 8% 28% 31% 16% 5%	330
November	1st to 10th	Day	9% 11% 30% 33% 14% 4	300
	11th to 20th	Day	7% 11% 28% 34% 17% 3	300
	21st to end	Day	10% 15% 35% 23% 13% 5%	300
December	1st to 10th	Day	3 11% 40% 30% 13% 3	300
	11th to 20th	Day	8% 10% 38% 32% 12%	300
	21st to end	Day	10% 14% 39% 29% 7% 1	330
January	1st to 10th	Night	4 9% 40% 36% 9% 1	981
	11th to 20th	Night	5% 9% 40% 34% 9% 2	903
	21st to end	Night	5% 7% 46% 31% 11% 1	836
February	1st to 10th	Night	5% 11% 45% 30% 9%	760
	11th to 20th	Night	7% 11% 52% 23% 6% 1	744
	21st to end	Night	8% 12% 53% 24% 3	628
March	1st to 10th	Night	6% 12% 46% 30% 5% 1	760
	11th to 20th	Night	8% 13% 38% 33% 8% 1	743
	21st to end	Night	6% 14% 54% 21% 5%	627
April	1st to 10th	Night	6% 12% 52% 27% 4	570
	11th to 20th	Night	8% 13% 50% 26% 2	563
	21st to end	Night	9% 12% 42% 31% 6%	570
May	1st to 10th	Night	8% 12% 40% 33% 7%	570
	11th to 20th	Night	9% 7% 37% 34% 11% 1	561
	21st to end	Night	6% 9% 47% 29% 7% 1	617
June	1st to 10th	Night	5% 6% 33% 42% 14% 1	570
	11th to 20th	Night	3 5% 45% 38% 9%	570
	21st to end	Night	5% 4 32% 44% 15%	570
July	1st to 10th	Night	6% 2 19% 51% 21% 2	555
	11th to 20th	Night	3 1 15% 51% 27% 2	552
	21st to end	Night	8% 1 13% 48% 27% 2	624
August	1st to 10th	Night	6% 1 14% 42% 33% 3	567
	11th to 20th	Night	8% 1 13% 53% 24% 1	564
	21st to end	Night	5% 2 17% 50% 24% 3	627
September	1st to 10th	Night	6% 2 19% 53% 20% 1	570
	11th to 20th	Night	9% 2 33% 39% 16% 1	570
	21st to end	Night	7% 6% 29% 39% 17% 2	570
October	1st to 10th	Night	9% 5% 31% 42% 11% 1	570
	11th to 20th	Night	5% 6% 39% 34% 13% 3	746
	21st to end	Night	8% 8% 34% 33% 14% 3	922
November	1st to 10th	Night	6% 7% 34% 41% 11% 2	975
	11th to 20th	Night	4 9% 41% 35% 11% 1	1000
	21st to end	Night	6% 10% 35% 35% 13% 1	1000
December	1st to 10th	Night	4 9% 40% 35% 12% 1	1000
	11th to 20th	Night	6% 9% 40% 37% 8% 1	1000
	21st to end	Night	7% 14% 40% 31% 8% 1	1100

Page generated at 2025-01-04 01:24:02. Version ac07

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