Lake Warren State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Warren State Park clear sky chart from 2005-11-06 to 2025-12-18.

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% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	127121
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 44%	123922
Transparency	Day	39% 8% 13% 17% 17% 7%	130793
	Night	36% 7% 13% 17% 18% 8%	128319
Seeing	Day	13% 9% 23% 25% 20% 10%	16889
	Night	13% 8% 24% 33% 20% 3	26959

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% 5% 2 5% 3 3 3 3 5% 5% 54%	4056
	11th to 20th	Day	14% 5% 2 5% 3 3 3 3 4 7% 52%	4060
	21st to end	Day	13% 8% 3 6% 4 4 3 3 5% 7% 45%	4466
February	1st to 10th	Day	14% 6% 2 6% 5% 4 4 4 6% 7% 42%	1863
	11th to 20th	Day	19% 6% 2 5% 3 3 4 2 5% 7% 45%	1948
	21st to end	Day	14% 7% 2 5% 4 3 4 2 4 7% 47%	1723
March	1st to 10th	Day	20% 7% 3 7% 4 4 4 3 5% 6% 38%	4935
	11th to 20th	Day	8% 4 2 4 4 4 4 3 6% 7% 55%	4980
	21st to end	Day	14% 6% 2 6% 4 4 4 3 4 5% 47%	5465
April	1st to 10th	Day	8% 4 2 5% 5% 4 5% 4 6% 7% 51%	2200
	11th to 20th	Day	9% 6% 2 5% 4 4 4 3 5% 7% 50%	2322
	21st to end	Day	6% 5% 2 4 5% 4 4 4 7% 8% 52%	2485
May	1st to 10th	Day	9% 6% 2 7% 6% 5% 6% 4 7% 9% 38%	5862
	11th to 20th	Day	15% 7% 2 6% 4 5% 5% 4 7% 9% 35%	5861
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 10% 42%	6433
June	1st to 10th	Day	10% 7% 3 8% 7% 7% 7% 5% 7% 10% 30%	2600
	11th to 20th	Day	7% 5% 1 6% 6% 7% 6% 6% 10% 13% 35%	2600
	21st to end	Day	7% 5% 2 7% 6% 7% 6% 7% 9% 11% 33%	2600
July	1st to 10th	Day	12% 7% 4 10% 7% 7% 7% 6% 9% 10% 21%	5900
	11th to 20th	Day	4 3 2 7% 7% 8% 8% 7% 11% 15% 29%	5900
	21st to end	Day	6% 6% 3 9% 6% 7% 8% 6% 9% 13% 27%	6424
August	1st to 10th	Day	20% 6% 3 8% 7% 7% 7% 5% 7% 9% 20%	4234
	11th to 20th	Day	8% 5% 3 7% 5% 6% 7% 5% 9% 11% 32%	4174
	21st to end	Day	8% 6% 3 8% 7% 6% 7% 6% 7% 10% 34%	4226
September	1st to 10th	Day	9% 6% 2 7% 6% 6% 7% 6% 8% 9% 36%	2200
	11th to 20th	Day	13% 7% 2 7% 6% 5% 5% 5% 7% 7% 37%	2200
	21st to end	Day	16% 7% 3 6% 4 4 4 3 5% 8% 39%	2200
October	1st to 10th	Day	12% 6% 3 8% 4 5% 4 3 5% 7% 45%	2105
	11th to 20th	Day	10% 4 2 4 3 3 3 3 3 6% 60%	2000
	21st to end	Day	9% 6% 2 5% 3 3 3 3 4 5% 57%	2200
November	1st to 10th	Day	12% 5% 2 5% 3 4 3 4 5% 5% 53%	2057
	11th to 20th	Day	13% 6% 3 5% 3 3 3 2 4 6% 53%	2030
	21st to end	Day	13% 6% 2 5% 4 3 3 3 5% 7% 50%	1890
December	1st to 10th	Day	10% 4 2 6% 4 4 4 4 5% 6% 51%	3020
	11th to 20th	Day	13% 6% 2 5% 3 3 4 4 5% 6% 49%	3436
	21st to end	Day	19% 8% 3 6% 3 3 3 2 4 6% 42%	4466
January	1st to 10th	Night	11% 5% 2 4 3 4 3 3 4 5% 57%	5889
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 4 5% 7% 45%	5900
	21st to end	Night	13% 8% 3 6% 4 4 4 3 5% 6% 45%	6490
February	1st to 10th	Night	16% 6% 1 4 4 4 4 4 6% 6% 45%	2535
	11th to 20th	Night	16% 7% 3 6% 3 4 4 3 5% 5% 45%	2338
	21st to end	Night	11% 6% 3 6% 4 4 3 3 6% 7% 46%	1905
March	1st to 10th	Night	18% 8% 3 6% 4 4 3 4 4 6% 39%	4918
	11th to 20th	Night	11% 4 1 4 3 3 4 3 6% 8% 54%	4980
	21st to end	Night	12% 5% 2 5% 3 4 4 3 5% 7% 49%	5467
April	1st to 10th	Night	10% 5% 2 4 4 3 5% 4 5% 7% 50%	2200
	11th to 20th	Night	11% 4 2 5% 3 3 3 4 6% 8% 52%	2025
	21st to end	Night	7% 4 1 5% 4 3 5% 4 5% 8% 54%	1930
May	1st to 10th	Night	7% 6% 3 7% 5% 4 5% 5% 7% 12% 41%	4033
	11th to 20th	Night	15% 6% 2 5% 4 4 5% 4 7% 10% 38%	4032
	21st to end	Night	9% 5% 2 6% 4 4 4 4 6% 9% 46%	4421
June	1st to 10th	Night	10% 6% 2 7% 5% 5% 6% 5% 9% 13% 33%	1800
	11th to 20th	Night	7% 5% 2 6% 5% 5% 7% 5% 8% 12% 37%	1800
	21st to end	Night	6% 5% 2 6% 6% 5% 6% 7% 10% 11% 37%	1800
July	1st to 10th	Night	12% 8% 4 8% 6% 6% 7% 6% 8% 11% 25%	4058
	11th to 20th	Night	5% 5% 2 8% 6% 6% 7% 6% 9% 14% 34%	4057
	21st to end	Night	8% 7% 3 8% 7% 7% 7% 6% 9% 11% 27%	4427
August	1st to 10th	Night	21% 6% 3 7% 5% 6% 6% 5% 8% 11% 22%	2915
	11th to 20th	Night	8% 5% 3 7% 5% 6% 7% 5% 8% 11% 35%	2875
	21st to end	Night	7% 5% 2 5% 3 5% 5% 4 8% 11% 44%	3632
September	1st to 10th	Night	10% 6% 2 7% 5% 4 5% 4 8% 9% 40%	2200
	11th to 20th	Night	10% 6% 3 8% 5% 5% 5% 4 6% 8% 39%	2200
	21st to end	Night	14% 6% 3 5% 5% 4 5% 4 6% 9% 39%	2200
October	1st to 10th	Night	13% 6% 2 6% 4 3 4 3 5% 6% 47%	2293
	11th to 20th	Night	11% 5% 2 5% 2 2 3 2 4 5% 58%	2400
	21st to end	Night	10% 5% 2 4 4 3 3 3 4 6% 57%	2640
November	1st to 10th	Night	11% 6% 2 4 3 3 3 3 5% 7% 53%	2461
	11th to 20th	Night	14% 7% 2 4 3 2 3 3 5% 5% 52%	2587
	21st to end	Night	12% 5% 2 5% 3 4 4 3 5% 7% 49%	2730
December	1st to 10th	Night	12% 5% 2 5% 3 3 3 3 4 5% 55%	4380
	11th to 20th	Night	16% 8% 3 7% 4 3 3 2 4 5% 45%	4914
	21st to end	Night	17% 7% 2 5% 4 4 4 3 5% 6% 44%	6490

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	31% 6% 6% 16% 32% 10%	4057
	11th to 20th	Day	33% 4 5% 17% 30% 11%	4060
	21st to end	Day	39% 6% 5% 18% 20% 12%	4466
February	1st to 10th	Day	40% 6% 9% 19% 20% 6%	1863
	11th to 20th	Day	40% 5% 7% 16% 23% 9%	1958
	21st to end	Day	37% 6% 7% 17% 21% 11%	1723
March	1st to 10th	Day	46% 6% 7% 11% 20% 11%	4935
	11th to 20th	Day	26% 5% 10% 17% 22% 20%	4980
	21st to end	Day	40% 4 7% 16% 21% 12%	5465
April	1st to 10th	Day	31% 7% 12% 19% 22% 9%	2200
	11th to 20th	Day	33% 6% 9% 20% 19% 12%	2322
	21st to end	Day	28% 7% 12% 26% 23% 5%	2485
May	1st to 10th	Day	38% 9% 16% 22% 12% 2	5897
	11th to 20th	Day	43% 7% 18% 19% 12% 1	5865
	21st to end	Day	34% 9% 15% 19% 21% 2	6447
June	1st to 10th	Day	45% 11% 16% 16% 10% 1	2600
	11th to 20th	Day	36% 12% 21% 21% 8% 1	2600
	21st to end	Day	39% 14% 20% 17% 9% 1	2600
July	1st to 10th	Day	54% 11% 20% 12% 2 1	5835
	11th to 20th	Day	40% 14% 33% 11% 2	5831
	21st to end	Day	45% 13% 22% 17% 4	6240
August	1st to 10th	Day	58% 10% 20% 9% 3	4221
	11th to 20th	Day	38% 13% 18% 21% 10%	4213
	21st to end	Day	41% 10% 15% 26% 7% 1	4226
September	1st to 10th	Day	42% 13% 15% 13% 13% 5%	2200
	11th to 20th	Day	44% 9% 12% 16% 15% 4	2200
	21st to end	Day	44% 7% 12% 17% 16% 4	2200
October	1st to 10th	Day	40% 6% 8% 12% 24% 10%	3430
	11th to 20th	Day	17% 3 6% 12% 30% 32%	3240
	21st to end	Day	23% 4 6% 17% 34% 15%	3538
November	1st to 10th	Day	31% 6% 9% 15% 23% 15%	2057
	11th to 20th	Day	34% 4 7% 18% 25% 13%	2030
	21st to end	Day	35% 4 8% 21% 22% 9%	1890
December	1st to 10th	Day	33% 5% 10% 17% 24% 12%	3020
	11th to 20th	Day	36% 4 9% 26% 20% 6%	3433
	21st to end	Day	44% 4 6% 20% 22% 3	4466
January	1st to 10th	Night	29% 5% 7% 15% 34% 10%	5889
	11th to 20th	Night	37% 5% 6% 16% 27% 8%	5900
	21st to end	Night	39% 6% 7% 12% 25% 11%	6490
February	1st to 10th	Night	39% 5% 9% 19% 20% 9%	2535
	11th to 20th	Night	41% 6% 8% 15% 20% 10%	2339
	21st to end	Night	37% 6% 9% 17% 17% 14%	1905
March	1st to 10th	Night	44% 8% 7% 12% 16% 12%	4918
	11th to 20th	Night	28% 5% 9% 13% 25% 20%	4980
	21st to end	Night	34% 5% 10% 17% 21% 13%	5467
April	1st to 10th	Night	32% 7% 12% 20% 19% 10%	2200
	11th to 20th	Night	29% 6% 10% 22% 21% 12%	2025
	21st to end	Night	27% 6% 14% 25% 21% 6%	1930
May	1st to 10th	Night	33% 10% 19% 25% 12% 3	4060
	11th to 20th	Night	38% 9% 21% 20% 11% 1	4033
	21st to end	Night	32% 9% 16% 25% 17% 2	4429
June	1st to 10th	Night	37% 14% 20% 19% 9% 1	1800
	11th to 20th	Night	36% 13% 21% 24% 7%	1800
	21st to end	Night	32% 17% 25% 18% 7% 1	1800
July	1st to 10th	Night	50% 11% 20% 15% 3 1	4015
	11th to 20th	Night	39% 11% 37% 11% 2	4006
	21st to end	Night	46% 13% 21% 15% 5%	4297
August	1st to 10th	Night	52% 12% 24% 10% 2	2904
	11th to 20th	Night	38% 13% 22% 21% 6%	2902
	21st to end	Night	31% 10% 20% 33% 6%	3632
September	1st to 10th	Night	38% 12% 17% 18% 11% 4	2200
	11th to 20th	Night	39% 11% 16% 18% 13% 3	2200
	21st to end	Night	41% 9% 15% 19% 14% 3	2200
October	1st to 10th	Night	36% 5% 10% 16% 24% 8%	3748
	11th to 20th	Night	18% 3 5% 12% 26% 36%	3899
	21st to end	Night	24% 4 7% 18% 30% 17%	4252
November	1st to 10th	Night	31% 5% 10% 14% 24% 15%	2461
	11th to 20th	Night	34% 5% 6% 17% 25% 13%	2587
	21st to end	Night	35% 6% 9% 17% 22% 10%	2730
December	1st to 10th	Night	32% 5% 8% 14% 31% 10%	4380
	11th to 20th	Night	42% 4 10% 16% 20% 8%	4916
	21st to end	Night	41% 5% 6% 20% 24% 3	6490

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	15% 19% 45% 17% 3	300
	11th to 20th	Day	16% 18% 39% 18% 6% 2	300
	21st to end	Day	23% 25% 35% 13% 4	330
February	1st to 10th	Day	16% 21% 36% 21% 6%	300
	11th to 20th	Day	28% 17% 37% 16% 2	300
	21st to end	Day	17% 18% 39% 20% 5%	322
March	1st to 10th	Day	19% 17% 30% 22% 12% 1	500
	11th to 20th	Day	14% 17% 37% 23% 8% 1	500
	21st to end	Day	17% 14% 38% 20% 9% 1	550
April	1st to 10th	Day	13% 17% 31% 26% 11% 1	500
	11th to 20th	Day	11% 14% 28% 24% 16% 7%	492
	21st to end	Day	9% 9% 25% 27% 20% 9%	500
May	1st to 10th	Day	8% 12% 30% 25% 16% 8%	503
	11th to 20th	Day	14% 6% 22% 27% 21% 10%	527
	21st to end	Day	12% 6% 17% 27% 24% 15%	573
June	1st to 10th	Day	11% 3 17% 30% 26% 13%	530
	11th to 20th	Day	9% 4 15% 25% 26% 21%	530
	21st to end	Day	7% 2 12% 28% 30% 20%	530
July	1st to 10th	Day	8% 3 8% 23% 34% 25%	525
	11th to 20th	Day	6% 2 5% 21% 41% 26%	524
	21st to end	Day	6% 3 9% 25% 39% 18%	576
August	1st to 10th	Day	11% 5% 11% 24% 29% 19%	526
	11th to 20th	Day	9% 3 7% 22% 33% 27%	519
	21st to end	Day	13% 4 10% 25% 26% 21%	583
September	1st to 10th	Day	9% 3 14% 30% 28% 15%	530
	11th to 20th	Day	15% 5% 14% 29% 29% 8%	530
	21st to end	Day	17% 3 14% 28% 28% 9%	530
October	1st to 10th	Day	16% 5% 23% 29% 17% 10%	530
	11th to 20th	Day	12% 5% 22% 33% 21% 8%	530
	21st to end	Day	13% 8% 25% 30% 20% 5%	583
November	1st to 10th	Day	16% 7% 27% 26% 19% 4	535
	11th to 20th	Day	18% 12% 36% 23% 9% 2	470
	21st to end	Day	14% 15% 33% 28% 10% 1	330
December	1st to 10th	Day	21% 14% 35% 23% 6% 1	330
	11th to 20th	Day	19% 14% 33% 22% 11% 1	321
	21st to end	Day	28% 12% 33% 18% 9% 2	330
January	1st to 10th	Night	16% 15% 33% 30% 6% 1	800
	11th to 20th	Night	16% 13% 33% 30% 9%	800
	21st to end	Night	20% 13% 38% 26% 3	880
February	1st to 10th	Night	18% 12% 32% 31% 8%	800
	11th to 20th	Night	19% 15% 37% 26% 3	783
	21st to end	Night	15% 15% 35% 32% 3	660
March	1st to 10th	Night	15% 12% 35% 33% 6%	800
	11th to 20th	Night	14% 13% 36% 30% 7%	800
	21st to end	Night	12% 12% 38% 30% 7%	880
April	1st to 10th	Night	12% 12% 33% 33% 9%	800
	11th to 20th	Night	12% 11% 32% 31% 14% 1	791
	21st to end	Night	8% 8% 30% 39% 15%	730
May	1st to 10th	Night	6% 8% 26% 42% 17% 1	600
	11th to 20th	Night	10% 5% 23% 38% 20% 3	591
	21st to end	Night	9% 2 17% 37% 31% 3	650
June	1st to 10th	Night	11% 2 15% 41% 27% 4	600
	11th to 20th	Night	7% 3 12% 37% 32% 9%	600
	21st to end	Night	6% 3 10% 39% 37% 6%	600
July	1st to 10th	Night	8% 2 9% 34% 40% 7%	585
	11th to 20th	Night	9% 1 4 33% 44% 9%	582
	21st to end	Night	6% 1 9% 34% 44% 6%	657
August	1st to 10th	Night	13% 2 6% 31% 40% 9%	597
	11th to 20th	Night	9% 2 6% 28% 46% 9%	594
	21st to end	Night	13% 2 9% 31% 36% 9%	850
September	1st to 10th	Night	10% 3 12% 29% 40% 6%	800
	11th to 20th	Night	13% 3 13% 33% 35% 3	800
	21st to end	Night	18% 3 12% 33% 31% 3	800
October	1st to 10th	Night	16% 6% 17% 35% 23% 5%	800
	11th to 20th	Night	13% 5% 22% 34% 24% 3	800
	21st to end	Night	12% 5% 22% 35% 24% 2	880
November	1st to 10th	Night	12% 7% 23% 36% 18% 3	820
	11th to 20th	Night	17% 8% 28% 33% 13% 1	840
	21st to end	Night	14% 9% 28% 32% 16% 1	840
December	1st to 10th	Night	18% 10% 30% 31% 11% 1	840
	11th to 20th	Night	18% 9% 29% 31% 11% 1	829
	21st to end	Night	21% 11% 30% 29% 10%	880

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