Washington County State Recreational Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Washington County State Recreational Area clear sky chart from 2005-11-06 to 2026-05-17.

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	11% 7% 3 6% 4 4 4 4 6% 8% 42%	131850
	Night	13% 7% 3 7% 4 4 4 3 5% 7% 43%	131205
Transparency	Day	41% 2 11% 27% 17% 3	135427
	Night	41% 2 10% 25% 19% 3	135706
Seeing	Day	15% 8% 24% 26% 19% 8%	17584
	Night	16% 8% 27% 32% 15% 2	27484

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% 10% 4 11% 5% 5% 5% 4 5% 6% 35%	4691
	11th to 20th	Day	8% 7% 3 7% 5% 6% 4 3 5% 7% 45%	4908
	21st to end	Day	17% 12% 4 7% 5% 4 4 3 4 6% 35%	5812
February	1st to 10th	Day	16% 10% 4 6% 4 4 4 4 5% 6% 36%	1965
	11th to 20th	Day	16% 10% 3 9% 4 4 4 3 4 6% 37%	2048
	21st to end	Day	13% 10% 3 8% 4 3 4 4 5% 7% 39%	1730
March	1st to 10th	Day	17% 11% 3 5% 3 2 3 3 3 5% 45%	4580
	11th to 20th	Day	10% 7% 2 5% 3 3 4 3 5% 7% 51%	4963
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 6% 7% 38%	6019
April	1st to 10th	Day	12% 6% 2 7% 5% 4 4 4 7% 8% 42%	2520
	11th to 20th	Day	15% 9% 3 6% 5% 4 4 3 6% 6% 41%	2494
	21st to end	Day	16% 6% 2 7% 5% 4 5% 4 4 7% 39%	2520
May	1st to 10th	Day	16% 8% 3 7% 5% 5% 6% 4 7% 10% 29%	5821
	11th to 20th	Day	15% 8% 3 7% 4 5% 5% 4 6% 7% 36%	6067
	21st to end	Day	12% 6% 2 7% 5% 5% 4 4 6% 8% 40%	6935
June	1st to 10th	Day	8% 6% 2 6% 4 5% 4 4 6% 8% 47%	2800
	11th to 20th	Day	6% 4 2 5% 4 4 6% 4 7% 9% 48%	2800
	21st to end	Day	4 4 2 5% 5% 5% 4 5% 8% 11% 46%	2800
July	1st to 10th	Day	10% 4 2 5% 4 5% 5% 4 6% 9% 46%	6360
	11th to 20th	Day	5% 4 2 7% 6% 5% 6% 5% 9% 11% 39%	6360
	21st to end	Day	5% 5% 3 7% 6% 6% 6% 5% 8% 11% 38%	6771
August	1st to 10th	Day	5% 4 1 5% 4 4 4 3 6% 9% 55%	4070
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 44%	3849
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 9% 53%	4312
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 5% 7% 50%	2400
	11th to 20th	Day	7% 6% 2 6% 4 4 4 4 6% 8% 49%	2318
	21st to end	Day	11% 4 2 5% 4 3 4 4 6% 6% 52%	2200
October	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 6% 58%	2092
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 4 7% 52%	2000
	21st to end	Day	18% 7% 2 5% 3 4 3 2 4 6% 46%	2116
November	1st to 10th	Day	10% 6% 2 5% 4 4 4 3 4 6% 54%	1852
	11th to 20th	Day	14% 8% 2 5% 4 3 4 3 4 6% 47%	1890
	21st to end	Day	17% 10% 3 7% 4 3 3 3 4 5% 40%	1890
December	1st to 10th	Day	9% 9% 2 6% 4 3 3 3 3 6% 51%	2739
	11th to 20th	Day	13% 9% 4 8% 5% 4 4 4 5% 6% 39%	3088
	21st to end	Day	26% 15% 4 9% 5% 4 3 3 4 4 24%	4070
January	1st to 10th	Night	14% 10% 4 9% 4 4 5% 3 4 6% 37%	8232
	11th to 20th	Night	10% 9% 4 9% 4 5% 5% 3 4 5% 42%	8063
	21st to end	Night	17% 10% 4 8% 5% 4 4 3 4 6% 36%	8402
February	1st to 10th	Night	17% 11% 4 8% 4 4 4 3 5% 6% 35%	2652
	11th to 20th	Night	16% 8% 3 8% 5% 3 3 3 4 6% 41%	2458
	21st to end	Night	17% 7% 3 8% 4 4 4 4 5% 5% 40%	2076
March	1st to 10th	Night	16% 10% 3 7% 4 4 4 3 4 5% 39%	5493
	11th to 20th	Night	11% 7% 3 6% 4 3 3 3 4 7% 49%	5260
	21st to end	Night	16% 7% 3 7% 5% 5% 4 3 5% 7% 37%	5151
April	1st to 10th	Night	12% 6% 2 6% 4 3 4 3 5% 7% 47%	2100
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 6% 7% 44%	2075
	21st to end	Night	18% 8% 2 6% 5% 4 5% 2 5% 5% 40%	2100
May	1st to 10th	Night	16% 8% 3 8% 5% 4 4 4 6% 9% 33%	4291
	11th to 20th	Night	12% 7% 3 6% 4 5% 4 4 6% 8% 41%	3960
	21st to end	Night	13% 6% 3 6% 5% 5% 5% 4 6% 8% 39%	3942
June	1st to 10th	Night	8% 6% 2 6% 4 4 5% 4 6% 8% 47%	1600
	11th to 20th	Night	3 4 2 5% 3 4 5% 4 6% 9% 54%	1600
	21st to end	Night	4 3 2 4 4 4 5% 4 7% 10% 52%	1600
July	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 5% 8% 49%	3618
	11th to 20th	Night	6% 4 2 7% 5% 5% 5% 4 6% 9% 47%	3617
	21st to end	Night	5% 5% 2 6% 5% 5% 6% 5% 7% 13% 41%	4096
August	1st to 10th	Night	4 3 1 5% 3 4 4 4 5% 9% 59%	3081
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 6% 8% 50%	3200
	21st to end	Night	4 3 2 4 3 4 4 3 6% 8% 59%	3586
September	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 5% 6% 53%	2000
	11th to 20th	Night	6% 5% 2 5% 4 4 4 4 6% 8% 52%	2060
	21st to end	Night	11% 5% 2 4 4 4 4 3 4 7% 51%	2200
October	1st to 10th	Night	7% 4 1 5% 3 3 3 3 4 7% 60%	2304
	11th to 20th	Night	12% 4 2 6% 3 3 3 2 4 5% 56%	2400
	21st to end	Night	18% 7% 3 5% 3 3 3 3 3 5% 46%	2721
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 4 6% 55%	2666
	11th to 20th	Night	13% 7% 2 4 4 3 3 3 4 6% 51%	2730
	21st to end	Night	18% 8% 3 6% 4 3 3 2 4 6% 44%	2730
December	1st to 10th	Night	14% 9% 3 6% 4 3 3 3 5% 5% 45%	4652
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 4 6% 44%	5339
	21st to end	Night	25% 14% 4 9% 5% 4 4 3 4 4 25%	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	53% 1 11% 26% 8% 1	4692
	11th to 20th	Day	40% 2 8% 27% 19% 3	4908
	21st to end	Day	53% 1 10% 19% 12% 5%	5812
February	1st to 10th	Day	49% 2 12% 25% 11% 1	1965
	11th to 20th	Day	50% 3 9% 21% 15% 3	2058
	21st to end	Day	46% 2 9% 24% 15% 3	1730
March	1st to 10th	Day	44% 1 5% 23% 23% 4	4580
	11th to 20th	Day	35% 1 8% 30% 21% 5%	4963
	21st to end	Day	46% 2 13% 28% 11% 1	6021
April	1st to 10th	Day	41% 3 11% 27% 16% 1	2520
	11th to 20th	Day	44% 2 10% 26% 15% 3	2494
	21st to end	Day	46% 3 10% 28% 12% 2	2520
May	1st to 10th	Day	51% 3 12% 22% 11% 1	5857
	11th to 20th	Day	47% 3 10% 27% 12% 1	6071
	21st to end	Day	43% 2 10% 23% 20% 1	6949
June	1st to 10th	Day	36% 3 12% 29% 17% 3	2800
	11th to 20th	Day	31% 5% 13% 26% 23% 2	2800
	21st to end	Day	30% 5% 18% 25% 17% 5%	2800
July	1st to 10th	Day	35% 3 11% 31% 18% 3	6291
	11th to 20th	Day	38% 3 16% 30% 12% 1	6285
	21st to end	Day	39% 3 18% 28% 11% 1	6578
August	1st to 10th	Day	27% 3 12% 41% 16%	4056
	11th to 20th	Day	36% 3 13% 28% 18% 1	3885
	21st to end	Day	29% 3 12% 37% 17% 3	4311
September	1st to 10th	Day	34% 3 10% 29% 19% 5%	2400
	11th to 20th	Day	33% 3 8% 28% 25% 3	2318
	21st to end	Day	33% 3 8% 26% 27% 4	2200
October	1st to 10th	Day	17% 2 5% 24% 44% 8%	3404
	11th to 20th	Day	24% 2 7% 22% 39% 6%	3240
	21st to end	Day	33% 2 5% 26% 29% 4	3393
November	1st to 10th	Day	33% 3 10% 29% 20% 6%	1852
	11th to 20th	Day	41% 2 8% 24% 20% 6%	1890
	21st to end	Day	48% 1 8% 25% 16% 1	1890
December	1st to 10th	Day	37% 1 12% 31% 18%	2739
	11th to 20th	Day	48% 2 9% 25% 15% 2	3085
	21st to end	Day	67% 1 10% 14% 6% 1	4070
January	1st to 10th	Night	50% 1 13% 27% 9%	8233
	11th to 20th	Night	46% 2 5% 24% 21% 3	8063
	21st to end	Night	52% 1 10% 19% 17% 1	8402
February	1st to 10th	Night	52% 2 8% 24% 12% 1	2652
	11th to 20th	Night	46% 2 9% 24% 17% 2	2459
	21st to end	Night	46% 2 9% 24% 15% 4	2076
March	1st to 10th	Night	49% 2 5% 21% 21% 2	5493
	11th to 20th	Night	38% 2 10% 23% 22% 6%	5260
	21st to end	Night	48% 1 11% 27% 11% 1	5151
April	1st to 10th	Night	38% 3 11% 27% 18% 3	2100
	11th to 20th	Night	40% 2 11% 24% 19% 4	2075
	21st to end	Night	48% 1 9% 25% 15% 3	2100
May	1st to 10th	Night	49% 3 16% 21% 10% 1	4320
	11th to 20th	Night	43% 3 14% 25% 14% 1	3961
	21st to end	Night	44% 3 11% 25% 15% 3	3950
June	1st to 10th	Night	35% 3 13% 25% 21% 3	1600
	11th to 20th	Night	27% 3 11% 27% 25% 6%	1600
	21st to end	Night	26% 4 15% 28% 19% 7%	1600
July	1st to 10th	Night	34% 4 9% 27% 23% 3	3580
	11th to 20th	Night	34% 4 15% 30% 14% 2	3572
	21st to end	Night	35% 3 21% 28% 12% 1	3978
August	1st to 10th	Night	24% 3 17% 37% 19% 1	3071
	11th to 20th	Night	33% 3 14% 26% 22% 2	3230
	21st to end	Night	24% 2 12% 37% 22% 3	3586
September	1st to 10th	Night	34% 2 7% 30% 21% 7%	2000
	11th to 20th	Night	31% 2 7% 31% 25% 4	2060
	21st to end	Night	34% 3 7% 21% 29% 6%	2200
October	1st to 10th	Night	16% 2 5% 18% 49% 10%	3772
	11th to 20th	Night	23% 1 6% 22% 41% 6%	3899
	21st to end	Night	33% 1 6% 25% 26% 8%	4394
November	1st to 10th	Night	32% 2 10% 26% 24% 5%	2666
	11th to 20th	Night	36% 2 8% 26% 24% 5%	2730
	21st to end	Night	44% 2 9% 26% 18% 2	2730
December	1st to 10th	Night	42% 2 10% 30% 16% 1	4652
	11th to 20th	Night	44% 1 12% 24% 18%	5341
	21st to end	Night	65% 1 10% 16% 7% 1	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	21% 17% 32% 22% 8%	330
	11th to 20th	Day	25% 16% 38% 18% 3	330
	21st to end	Day	18% 19% 41% 18% 4	363
February	1st to 10th	Day	22% 12% 42% 18% 5%	330
	11th to 20th	Day	24% 18% 38% 15% 5% 1	330
	21st to end	Day	23% 19% 36% 20% 3	273
March	1st to 10th	Day	21% 16% 38% 19% 5% 1	330
	11th to 20th	Day	27% 12% 41% 16% 4 1	330
	21st to end	Day	24% 15% 35% 19% 6% 1	553
April	1st to 10th	Day	18% 14% 34% 24% 8% 1	540
	11th to 20th	Day	21% 14% 30% 22% 11% 2	532
	21st to end	Day	20% 11% 32% 24% 11% 2	540
May	1st to 10th	Day	19% 13% 29% 27% 10% 3	543
	11th to 20th	Day	18% 8% 23% 28% 17% 5%	601
	21st to end	Day	11% 4 25% 33% 18% 9%	789
June	1st to 10th	Day	11% 4 19% 27% 27% 12%	730
	11th to 20th	Day	8% 2 17% 35% 26% 11%	730
	21st to end	Day	7% 3 20% 34% 27% 10%	730
July	1st to 10th	Day	11% 2 11% 24% 29% 24%	721
	11th to 20th	Day	7% 2 10% 34% 34% 14%	718
	21st to end	Day	9% 4 9% 30% 34% 14%	794
August	1st to 10th	Day	10% 1 10% 31% 31% 17%	627
	11th to 20th	Day	9% 3 12% 28% 33% 14%	519
	21st to end	Day	10% 3 9% 25% 34% 20%	583
September	1st to 10th	Day	12% 2 12% 29% 32% 14%	530
	11th to 20th	Day	7% 2 7% 28% 37% 18%	530
	21st to end	Day	13% 5% 20% 25% 25% 12%	530
October	1st to 10th	Day	10% 5% 18% 36% 23% 8%	422
	11th to 20th	Day	15% 13% 29% 24% 15% 4	330
	21st to end	Day	27% 15% 29% 21% 9%	363
November	1st to 10th	Day	12% 10% 33% 26% 15% 4	330
	11th to 20th	Day	18% 16% 30% 24% 11% 2	330
	21st to end	Day	29% 12% 25% 23% 9% 2	330
December	1st to 10th	Day	15% 18% 37% 20% 7% 4	330
	11th to 20th	Day	22% 17% 32% 23% 6% 1	330
	21st to end	Day	29% 13% 37% 17% 4	363
January	1st to 10th	Night	20% 13% 36% 27% 4	1050
	11th to 20th	Night	21% 14% 38% 22% 4	1050
	21st to end	Night	19% 12% 42% 25% 2	1155
February	1st to 10th	Night	22% 11% 37% 28% 1	972
	11th to 20th	Night	21% 14% 38% 25% 2	823
	21st to end	Night	21% 14% 38% 25% 2	692
March	1st to 10th	Night	21% 13% 37% 26% 3	840
	11th to 20th	Night	22% 11% 34% 28% 6%	709
	21st to end	Night	23% 10% 31% 29% 7%	693
April	1st to 10th	Night	16% 11% 36% 31% 6%	630
	11th to 20th	Night	17% 10% 31% 30% 10% 1	623
	21st to end	Night	23% 7% 33% 27% 10% 1	630
May	1st to 10th	Night	18% 4 29% 37% 11% 1	630
	11th to 20th	Night	15% 5% 24% 35% 19% 3	609
	21st to end	Night	9% 4 21% 40% 22% 4	650
June	1st to 10th	Night	12% 2 16% 41% 28% 1	600
	11th to 20th	Night	6% 1 17% 46% 27% 3	600
	21st to end	Night	5% 2 18% 41% 31% 2	600
July	1st to 10th	Night	10% 2 9% 33% 39% 8%	585
	11th to 20th	Night	6% 2 7% 44% 37% 5%	582
	21st to end	Night	8% 2 8% 40% 35% 6%	657
August	1st to 10th	Night	8% 2 7% 41% 37% 5%	597
	11th to 20th	Night	7% 2 8% 37% 41% 5%	594
	21st to end	Night	7% 1 6% 36% 44% 5%	660
September	1st to 10th	Night	13% 3 10% 36% 33% 6%	600
	11th to 20th	Night	8% 1 10% 37% 37% 6%	660
	21st to end	Night	13% 4 19% 33% 26% 5%	800
October	1st to 10th	Night	8% 4 21% 39% 24% 5%	800
	11th to 20th	Night	15% 7% 28% 32% 17% 2	800
	21st to end	Night	21% 10% 30% 31% 7%	880
November	1st to 10th	Night	13% 6% 35% 35% 11%	820
	11th to 20th	Night	16% 10% 33% 31% 9%	840
	21st to end	Night	23% 10% 32% 27% 8%	840
December	1st to 10th	Night	23% 11% 33% 29% 5%	1008
	11th to 20th	Night	22% 8% 32% 32% 6%	1050
	21st to end	Night	28% 10% 36% 23% 3	1155

Page generated at 2026-05-14 00:58:56. Version ac07

Copyright © 2026 Attilla Danko.