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 2025-01-22.

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	12% 7% 3 6% 4 4 4 4 6% 7% 42%	104964
	Night	14% 7% 3 6% 4 4 4 3 5% 6% 43%	104474
Transparency	Day	40% 3 11% 27% 17% 3	108583
	Night	41% 2 10% 25% 19% 3	108996
Seeing	Day	15% 8% 23% 26% 19% 8%	15813
	Night	17% 8% 27% 32% 15% 2	25733

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	13% 10% 4 10% 5% 4 4 4 5% 5% 35%	2607
	11th to 20th	Day	14% 8% 3 6% 6% 6% 4 3 5% 6% 38%	2714
	21st to end	Day	23% 16% 4 7% 4 3 3 3 4 4 28%	3144
February	1st to 10th	Day	17% 10% 4 6% 4 4 4 3 5% 6% 36%	1777
	11th to 20th	Day	15% 10% 3 9% 4 4 4 3 5% 6% 38%	1848
	21st to end	Day	14% 10% 3 8% 4 3 4 4 5% 7% 38%	1570
March	1st to 10th	Day	20% 12% 4 6% 3 3 3 3 4 5% 37%	3120
	11th to 20th	Day	13% 7% 2 5% 4 3 3 3 5% 6% 49%	3398
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 5% 7% 38%	4115
April	1st to 10th	Day	11% 6% 2 7% 5% 4 4 4 7% 8% 43%	2280
	11th to 20th	Day	15% 9% 2 6% 5% 4 4 3 6% 6% 41%	2254
	21st to end	Day	17% 6% 2 7% 5% 4 5% 4 4 6% 39%	2280
May	1st to 10th	Day	13% 7% 3 6% 5% 6% 6% 5% 8% 10% 32%	3971
	11th to 20th	Day	17% 8% 2 6% 4 4 4 4 6% 7% 39%	4167
	21st to end	Day	9% 6% 2 7% 5% 5% 4 4 6% 8% 43%	4824
June	1st to 10th	Day	8% 6% 2 6% 4 5% 4 4 6% 9% 47%	2660
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 9% 50%	2660
	21st to end	Day	4 4 2 5% 5% 5% 4 5% 7% 11% 46%	2660
July	1st to 10th	Day	12% 4 2 5% 4 5% 5% 4 7% 9% 42%	4440
	11th to 20th	Day	5% 4 2 6% 5% 4 5% 4 8% 11% 46%	4440
	21st to end	Day	6% 6% 3 8% 6% 6% 7% 5% 7% 9% 37%	4702
August	1st to 10th	Day	5% 4 1 5% 4 4 4 3 6% 9% 54%	3945
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 43%	3729
	21st to end	Day	5% 5% 2 5% 4 4 4 4 6% 9% 53%	4180
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 5% 7% 49%	2280
	11th to 20th	Day	7% 6% 2 6% 4 4 4 4 5% 8% 48%	2202
	21st to end	Day	11% 4 2 4 4 3 4 4 6% 7% 52%	2090
October	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 6% 58%	1988
	11th to 20th	Day	12% 6% 2 5% 4 3 3 3 4 8% 51%	1900
	21st to end	Day	17% 7% 3 5% 3 4 3 2 4 6% 46%	2010
November	1st to 10th	Day	10% 6% 2 5% 4 4 4 3 4 5% 54%	1762
	11th to 20th	Day	14% 8% 2 5% 4 4 4 3 4 6% 47%	1800
	21st to end	Day	16% 10% 3 7% 4 3 3 3 4 5% 41%	1800
December	1st to 10th	Day	9% 10% 2 6% 4 3 3 3 3 6% 51%	2657
	11th to 20th	Day	13% 9% 4 8% 5% 4 4 4 5% 6% 38%	3008
	21st to end	Day	27% 15% 4 9% 5% 4 3 3 4 4 24%	3982
January	1st to 10th	Night	16% 8% 4 9% 5% 5% 5% 3 4 6% 35%	4568
	11th to 20th	Night	12% 11% 5% 11% 5% 6% 6% 4 4 4 32%	4471
	21st to end	Night	24% 13% 5% 9% 4 3 4 2 4 5% 27%	4546
February	1st to 10th	Night	17% 11% 4 9% 4 4 4 3 4 6% 34%	2400
	11th to 20th	Night	15% 8% 3 8% 5% 3 3 3 4 6% 42%	2218
	21st to end	Night	18% 8% 3 8% 4 4 4 4 5% 4 38%	1884
March	1st to 10th	Night	20% 11% 2 6% 4 4 3 2 4 5% 39%	3733
	11th to 20th	Night	13% 6% 3 6% 4 3 3 3 5% 6% 50%	3590
	21st to end	Night	16% 7% 3 7% 5% 5% 4 4 6% 7% 37%	3515
April	1st to 10th	Night	12% 6% 3 6% 5% 3 4 3 5% 6% 48%	1900
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 6% 7% 44%	1875
	21st to end	Night	18% 8% 2 6% 5% 4 5% 2 5% 4 40%	1900
May	1st to 10th	Night	17% 7% 2 6% 4 4 4 4 5% 8% 38%	2921
	11th to 20th	Night	14% 8% 3 6% 4 4 3 4 5% 6% 45%	2725
	21st to end	Night	9% 6% 3 6% 5% 5% 6% 4 7% 8% 41%	2743
June	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 9% 48%	1520
	11th to 20th	Night	3 4 2 4 3 4 5% 3 6% 10% 55%	1520
	21st to end	Night	4 3 2 4 4 4 5% 4 8% 10% 52%	1520
July	1st to 10th	Night	12% 5% 2 4 3 3 4 4 5% 9% 47%	2530
	11th to 20th	Night	5% 3 1 6% 4 4 4 4 5% 8% 56%	2530
	21st to end	Night	7% 6% 3 8% 6% 6% 6% 5% 6% 10% 38%	2857
August	1st to 10th	Night	4 3 1 4 3 4 4 4 5% 9% 59%	2986
	11th to 20th	Night	8% 4 2 6% 4 4 4 4 6% 8% 49%	3100
	21st to end	Night	4 4 2 4 3 4 4 3 6% 8% 59%	3476
September	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 5% 6% 54%	1900
	11th to 20th	Night	7% 5% 2 5% 4 4 4 3 6% 8% 52%	1957
	21st to end	Night	11% 4 2 4 4 4 4 3 4 7% 51%	2090
October	1st to 10th	Night	7% 4 1 5% 3 3 3 3 4 7% 59%	2189
	11th to 20th	Night	12% 4 2 6% 3 3 3 2 4 5% 55%	2280
	21st to end	Night	17% 8% 3 5% 3 3 3 3 3 5% 47%	2585
November	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 4 6% 55%	2536
	11th to 20th	Night	13% 7% 2 4 4 3 3 3 4 6% 50%	2600
	21st to end	Night	18% 8% 3 5% 4 3 3 2 4 6% 45%	2600
December	1st to 10th	Night	14% 8% 3 6% 4 3 3 4 5% 5% 46%	4514
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 4 6% 44%	5199
	21st to end	Night	25% 14% 4 9% 5% 4 4 3 4 4 24%	6996

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	52% 2 9% 27% 9% 1	2608
	11th to 20th	Day	48% 1 10% 23% 17% 1	2714
	21st to end	Day	62% 1 7% 19% 10% 1	3144
February	1st to 10th	Day	50% 2 10% 25% 11% 1	1777
	11th to 20th	Day	49% 3 10% 22% 14% 3	1858
	21st to end	Day	47% 2 9% 23% 15% 4	1570
March	1st to 10th	Day	51% 2 6% 22% 14% 5%	3120
	11th to 20th	Day	38% 1 10% 29% 16% 5%	3398
	21st to end	Day	47% 2 15% 24% 11% 1	4115
April	1st to 10th	Day	39% 4 11% 28% 17% 1	2280
	11th to 20th	Day	44% 2 9% 26% 16% 3	2254
	21st to end	Day	47% 3 10% 26% 12% 2	2280
May	1st to 10th	Day	47% 4 15% 26% 9% 1	4007
	11th to 20th	Day	46% 3 10% 29% 11% 1	4171
	21st to end	Day	40% 3 10% 23% 23% 1	4837
June	1st to 10th	Day	36% 3 13% 28% 17% 3	2660
	11th to 20th	Day	29% 5% 13% 27% 23% 3	2660
	21st to end	Day	30% 5% 18% 25% 17% 5%	2660
July	1st to 10th	Day	37% 4 12% 30% 14% 3	4371
	11th to 20th	Day	30% 3 13% 35% 16% 2	4365
	21st to end	Day	42% 3 15% 27% 11% 1	4554
August	1st to 10th	Day	27% 3 12% 41% 16%	3931
	11th to 20th	Day	37% 3 13% 27% 19% 1	3765
	21st to end	Day	29% 3 12% 37% 16% 3	4179
September	1st to 10th	Day	34% 3 10% 28% 19% 5%	2280
	11th to 20th	Day	34% 3 8% 28% 24% 3	2202
	21st to end	Day	32% 3 8% 27% 26% 4	2090
October	1st to 10th	Day	17% 2 5% 24% 43% 8%	3300
	11th to 20th	Day	24% 2 7% 22% 39% 6%	3140
	21st to end	Day	33% 2 5% 27% 29% 4	3287
November	1st to 10th	Day	33% 3 10% 28% 20% 6%	1762
	11th to 20th	Day	41% 2 8% 23% 20% 6%	1800
	21st to end	Day	48% 2 8% 25% 16% 2	1800
December	1st to 10th	Day	37% 1 12% 32% 18%	2657
	11th to 20th	Day	48% 2 9% 25% 14% 2	3005
	21st to end	Day	67% 1 10% 13% 6% 2	3982
January	1st to 10th	Night	51% 2 9% 26% 11% 1	4568
	11th to 20th	Night	56% 1 7% 22% 11% 1	4471
	21st to end	Night	62% 1 8% 20% 9% 1	4546
February	1st to 10th	Night	54% 3 8% 23% 12% 1	2400
	11th to 20th	Night	45% 3 9% 24% 18% 2	2219
	21st to end	Night	49% 2 10% 22% 14% 4	1884
March	1st to 10th	Night	50% 2 7% 22% 17% 2	3733
	11th to 20th	Night	37% 2 12% 24% 22% 4	3590
	21st to end	Night	47% 2 13% 29% 9% 1	3515
April	1st to 10th	Night	38% 3 10% 27% 18% 3	1900
	11th to 20th	Night	40% 2 10% 25% 20% 4	1875
	21st to end	Night	48% 2 9% 24% 15% 3	1900
May	1st to 10th	Night	46% 2 17% 23% 10% 1	2950
	11th to 20th	Night	42% 3 14% 26% 14% 1	2726
	21st to end	Night	40% 4 11% 26% 18% 2	2751
June	1st to 10th	Night	33% 4 13% 25% 21% 4	1520
	11th to 20th	Night	26% 3 11% 28% 26% 7%	1520
	21st to end	Night	26% 4 16% 27% 20% 7%	1520
July	1st to 10th	Night	35% 4 11% 28% 18% 4	2490
	11th to 20th	Night	27% 4 11% 36% 20% 3	2482
	21st to end	Night	41% 3 17% 25% 12% 1	2766
August	1st to 10th	Night	23% 3 17% 37% 19% 1	2976
	11th to 20th	Night	34% 3 14% 26% 22% 2	3130
	21st to end	Night	25% 2 12% 37% 21% 3	3476
September	1st to 10th	Night	33% 2 6% 30% 21% 7%	1900
	11th to 20th	Night	31% 3 6% 31% 24% 4	1957
	21st to end	Night	34% 3 7% 22% 29% 5%	2090
October	1st to 10th	Night	16% 2 5% 18% 49% 10%	3657
	11th to 20th	Night	23% 1 6% 22% 41% 7%	3779
	21st to end	Night	32% 1 7% 25% 26% 8%	4258
November	1st to 10th	Night	32% 2 10% 26% 24% 6%	2536
	11th to 20th	Night	36% 2 8% 25% 25% 5%	2600
	21st to end	Night	43% 2 9% 26% 19% 2	2600
December	1st to 10th	Night	41% 2 10% 30% 17% 1	4514
	11th to 20th	Night	44% 1 13% 23% 18%	5201
	21st to end	Night	65% 1 10% 16% 7% 1	6996

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	23% 17% 31% 21% 8%	300
	11th to 20th	Day	26% 16% 36% 19% 3	300
	21st to end	Day	19% 18% 38% 19% 5%	300
February	1st to 10th	Day	24% 12% 41% 17% 5%	270
	11th to 20th	Day	24% 18% 34% 16% 6% 1	270
	21st to end	Day	24% 19% 35% 20% 2	225
March	1st to 10th	Day	20% 17% 39% 19% 5% 1	270
	11th to 20th	Day	27% 11% 41% 16% 5%	270
	21st to end	Day	26% 15% 32% 19% 7% 1	469
April	1st to 10th	Day	17% 15% 33% 25% 9% 1	460
	11th to 20th	Day	20% 14% 29% 23% 12% 2	452
	21st to end	Day	22% 12% 32% 22% 11% 2	460
May	1st to 10th	Day	18% 14% 27% 28% 11% 3	463
	11th to 20th	Day	19% 7% 22% 28% 18% 6%	534
	21st to end	Day	10% 4 25% 33% 19% 10%	734
June	1st to 10th	Day	10% 5% 18% 27% 28% 12%	680
	11th to 20th	Day	8% 2 18% 35% 27% 11%	680
	21st to end	Day	7% 3 21% 35% 25% 9%	680
July	1st to 10th	Day	12% 2 11% 24% 28% 24%	671
	11th to 20th	Day	6% 2 10% 33% 34% 15%	668
	21st to end	Day	9% 4 9% 31% 33% 14%	739
August	1st to 10th	Day	10% 2 9% 31% 31% 18%	582
	11th to 20th	Day	10% 4 13% 29% 32% 12%	479
	21st to end	Day	11% 3 8% 24% 35% 20%	539
September	1st to 10th	Day	12% 2 13% 27% 32% 14%	490
	11th to 20th	Day	8% 2 8% 29% 36% 17%	490
	21st to end	Day	12% 6% 21% 25% 24% 12%	490
October	1st to 10th	Day	11% 5% 19% 35% 21% 9%	388
	11th to 20th	Day	15% 13% 31% 23% 14% 4	300
	21st to end	Day	25% 14% 29% 22% 9%	330
November	1st to 10th	Day	12% 9% 33% 25% 17% 4	300
	11th to 20th	Day	16% 17% 29% 24% 11% 2	300
	21st to end	Day	28% 11% 26% 24% 9% 2	300
December	1st to 10th	Day	15% 18% 36% 20% 7% 4	300
	11th to 20th	Day	22% 17% 30% 24% 7% 1	300
	21st to end	Day	30% 14% 35% 17% 4	330
January	1st to 10th	Night	20% 14% 36% 26% 4	1000
	11th to 20th	Night	22% 14% 38% 22% 4	1000
	21st to end	Night	20% 12% 40% 25% 2	1051
February	1st to 10th	Night	23% 12% 35% 28% 2	880
	11th to 20th	Night	20% 14% 39% 26% 2	743
	21st to end	Night	23% 14% 37% 25% 2	628
March	1st to 10th	Night	21% 12% 38% 25% 4	760
	11th to 20th	Night	22% 10% 34% 28% 6%	641
	21st to end	Night	24% 9% 30% 29% 7%	627
April	1st to 10th	Night	16% 12% 35% 31% 6%	570
	11th to 20th	Night	17% 10% 29% 31% 11% 1	563
	21st to end	Night	23% 7% 34% 26% 9% 1	570
May	1st to 10th	Night	18% 4 29% 36% 11% 1	570
	11th to 20th	Night	15% 4 23% 34% 20% 3	561
	21st to end	Night	9% 4 20% 40% 23% 4	617
June	1st to 10th	Night	11% 2 16% 40% 29% 1	570
	11th to 20th	Night	5% 1 17% 46% 27% 2	570
	21st to end	Night	5% 2 19% 42% 30% 2	570
July	1st to 10th	Night	10% 1 9% 32% 39% 8%	555
	11th to 20th	Night	6% 1 7% 43% 37% 5%	552
	21st to end	Night	8% 2 9% 41% 34% 6%	624
August	1st to 10th	Night	7% 2 7% 40% 38% 6%	567
	11th to 20th	Night	7% 2 8% 38% 39% 5%	564
	21st to end	Night	7% 1 6% 35% 45% 5%	627
September	1st to 10th	Night	13% 3 10% 35% 33% 6%	570
	11th to 20th	Night	9% 1 11% 37% 37% 6%	627
	21st to end	Night	13% 4 19% 33% 26% 5%	760
October	1st to 10th	Night	8% 4 21% 38% 24% 5%	760
	11th to 20th	Night	15% 7% 28% 32% 16% 2	760
	21st to end	Night	21% 10% 30% 31% 8%	836
November	1st to 10th	Night	13% 5% 34% 35% 11% 1	780
	11th to 20th	Night	17% 10% 33% 31% 9% 1	800
	21st to end	Night	22% 10% 33% 27% 9%	800
December	1st to 10th	Night	23% 11% 32% 30% 5%	960
	11th to 20th	Night	23% 7% 32% 32% 6%	1000
	21st to end	Night	28% 11% 35% 22% 4	1100

Page generated at 2025-01-19 02:06:46. Version ac07

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