Bladen Lake State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bladen Lake State Forest 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	12% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	126736
	Night	12% 7% 2 6% 4 4 4 4 6% 7% 43%	124228
Transparency	Day	41% 6% 11% 19% 17% 6%	130339
	Night	38% 6% 11% 18% 19% 6%	128694
Seeing	Day	17% 11% 25% 25% 16% 6%	17107
	Night	16% 9% 25% 32% 16% 2	27298

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% 6% 2 5% 3 3 2 2 4 5% 55%	4056
	11th to 20th	Day	12% 5% 2 5% 3 3 3 2 3 5% 56%	4060
	21st to end	Day	12% 10% 3 7% 5% 4 3 3 4 5% 43%	4466
February	1st to 10th	Day	17% 8% 3 5% 4 4 4 3 4 6% 42%	1800
	11th to 20th	Day	20% 7% 3 5% 3 3 3 3 3 6% 44%	1814
	21st to end	Day	16% 8% 2 6% 5% 4 4 4 5% 6% 42%	1800
March	1st to 10th	Day	21% 8% 2 7% 4 4 4 4 4 5% 38%	4935
	11th to 20th	Day	11% 4 2 5% 3 3 4 4 5% 6% 53%	4980
	21st to end	Day	13% 6% 2 5% 4 4 5% 3 5% 5% 48%	5465
April	1st to 10th	Day	10% 5% 2 4 4 3 4 4 6% 8% 51%	2333
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 7% 50%	2374
	21st to end	Day	10% 5% 2 6% 5% 5% 4 4 5% 7% 48%	2400
May	1st to 10th	Day	8% 6% 3 8% 5% 6% 6% 5% 7% 11% 34%	5621
	11th to 20th	Day	18% 8% 3 7% 5% 5% 6% 4 6% 9% 29%	5861
	21st to end	Day	11% 5% 2 6% 5% 5% 6% 5% 7% 8% 40%	6433
June	1st to 10th	Day	11% 7% 3 9% 6% 5% 7% 4 7% 8% 34%	2600
	11th to 20th	Day	10% 4 2 7% 6% 6% 7% 5% 7% 10% 36%	2600
	21st to end	Day	8% 6% 2 8% 6% 6% 7% 6% 10% 10% 31%	2600
July	1st to 10th	Day	9% 7% 4 10% 7% 7% 8% 6% 8% 11% 25%	5900
	11th to 20th	Day	8% 7% 3 10% 6% 7% 7% 6% 8% 13% 26%	5900
	21st to end	Day	9% 7% 3 9% 7% 6% 7% 5% 9% 11% 25%	6424
August	1st to 10th	Day	22% 11% 3 9% 6% 6% 6% 4 6% 8% 17%	4234
	11th to 20th	Day	10% 8% 3 9% 6% 5% 6% 5% 7% 9% 31%	3952
	21st to end	Day	7% 5% 3 7% 4 5% 5% 5% 6% 9% 43%	4312
September	1st to 10th	Day	10% 5% 2 7% 5% 6% 5% 5% 7% 10% 38%	2400
	11th to 20th	Day	14% 8% 3 8% 4 5% 5% 5% 6% 8% 35%	2290
	21st to end	Day	17% 7% 3 8% 4 4 4 4 6% 7% 36%	2140
October	1st to 10th	Day	14% 7% 2 6% 4 5% 4 3 4 6% 45%	2000
	11th to 20th	Day	11% 5% 2 5% 3 3 3 3 5% 6% 54%	2000
	21st to end	Day	12% 5% 2 5% 3 4 3 2 4 5% 56%	2200
November	1st to 10th	Day	11% 6% 2 4 3 3 3 3 4 6% 54%	2057
	11th to 20th	Day	14% 6% 2 4 3 3 3 2 4 5% 52%	2100
	21st to end	Day	12% 5% 2 6% 4 3 3 3 4 6% 51%	1969
December	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 3 5% 5% 51%	2758
	11th to 20th	Day	14% 7% 2 6% 4 4 3 3 4 6% 47%	3436
	21st to end	Day	14% 7% 2 6% 4 4 4 3 5% 7% 44%	4466
January	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 4 5% 55%	5889
	11th to 20th	Night	13% 6% 2 6% 4 4 3 3 4 5% 50%	5900
	21st to end	Night	13% 9% 2 7% 4 3 4 3 5% 6% 45%	6490
February	1st to 10th	Night	16% 7% 2 6% 3 4 4 3 5% 5% 45%	2600
	11th to 20th	Night	18% 8% 2 6% 4 3 3 3 5% 5% 42%	2469
	21st to end	Night	15% 5% 2 6% 4 4 4 3 6% 6% 45%	1827
March	1st to 10th	Night	20% 9% 3 6% 4 4 4 2 4 5% 39%	4918
	11th to 20th	Night	12% 5% 2 5% 3 3 4 4 6% 7% 49%	4980
	21st to end	Night	13% 5% 1 5% 3 4 4 3 5% 6% 50%	5467
April	1st to 10th	Night	12% 5% 2 6% 3 3 4 3 6% 7% 49%	2065
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 3 5% 6% 51%	1975
	21st to end	Night	9% 4 2 6% 4 4 5% 4 6% 6% 50%	2000
May	1st to 10th	Night	8% 6% 3 7% 5% 4 4 5% 7% 12% 39%	4316
	11th to 20th	Night	16% 8% 3 7% 5% 5% 4 4 6% 9% 34%	4032
	21st to end	Night	12% 6% 2 6% 5% 4 5% 4 7% 8% 41%	4421
June	1st to 10th	Night	10% 6% 3 6% 4 6% 5% 5% 7% 11% 36%	1800
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 4 8% 9% 39%	1800
	21st to end	Night	7% 5% 2 6% 6% 6% 6% 5% 9% 12% 37%	1800
July	1st to 10th	Night	9% 7% 3 8% 6% 6% 7% 5% 8% 11% 29%	4058
	11th to 20th	Night	9% 8% 4 8% 5% 6% 6% 5% 9% 15% 25%	4057
	21st to end	Night	11% 8% 4 9% 6% 6% 7% 5% 8% 10% 26%	4427
August	1st to 10th	Night	19% 10% 3 8% 5% 5% 5% 5% 6% 9% 24%	2915
	11th to 20th	Night	9% 7% 3 8% 5% 6% 6% 5% 8% 9% 34%	3062
	21st to end	Night	6% 4 2 7% 4 5% 5% 4 7% 11% 44%	3586
September	1st to 10th	Night	9% 6% 2 6% 4 5% 5% 5% 7% 8% 42%	2000
	11th to 20th	Night	12% 7% 2 6% 5% 5% 5% 4 6% 7% 41%	2105
	21st to end	Night	17% 8% 3 6% 4 4 4 4 5% 6% 39%	2259
October	1st to 10th	Night	13% 7% 2 6% 4 4 3 4 5% 6% 46%	2400
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 6% 55%	2400
	21st to end	Night	11% 5% 2 4 3 3 4 3 4 6% 55%	2640
November	1st to 10th	Night	13% 6% 2 4 4 3 4 3 4 5% 54%	2461
	11th to 20th	Night	15% 7% 2 4 2 3 3 3 6% 6% 50%	2520
	21st to end	Night	12% 6% 2 5% 3 3 4 3 5% 7% 50%	2646
December	1st to 10th	Night	12% 7% 2 5% 3 3 3 3 4 5% 53%	4539
	11th to 20th	Night	15% 8% 2 6% 4 4 4 4 5% 6% 43%	4914
	21st to end	Night	13% 6% 2 5% 4 4 4 4 5% 6% 47%	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	34% 2 5% 19% 32% 8%	4057
	11th to 20th	Day	32% 3 4 16% 32% 12%	4060
	21st to end	Day	44% 4 5% 14% 22% 11%	4466
February	1st to 10th	Day	44% 3 9% 19% 20% 5%	1800
	11th to 20th	Day	44% 3 5% 18% 23% 7%	1823
	21st to end	Day	42% 4 9% 18% 19% 8%	1800
March	1st to 10th	Day	49% 4 7% 13% 19% 9%	4935
	11th to 20th	Day	31% 4 7% 14% 28% 15%	4980
	21st to end	Day	38% 4 8% 20% 22% 9%	5465
April	1st to 10th	Day	31% 5% 9% 23% 25% 7%	2333
	11th to 20th	Day	33% 4 9% 23% 22% 9%	2374
	21st to end	Day	35% 6% 11% 22% 22% 5%	2400
May	1st to 10th	Day	41% 9% 16% 24% 9% 1	5653
	11th to 20th	Day	50% 8% 11% 20% 11% 1	5865
	21st to end	Day	38% 8% 12% 20% 19% 3	6447
June	1st to 10th	Day	45% 7% 12% 21% 14% 1	2600
	11th to 20th	Day	40% 10% 15% 21% 12% 2	2600
	21st to end	Day	41% 10% 17% 20% 10% 2	2600
July	1st to 10th	Day	47% 12% 20% 16% 4 1	5835
	11th to 20th	Day	46% 14% 26% 10% 3 1	5831
	21st to end	Day	47% 12% 15% 17% 8%	6240
August	1st to 10th	Day	64% 8% 13% 10% 4	4221
	11th to 20th	Day	46% 9% 13% 21% 11%	3991
	21st to end	Day	36% 7% 15% 30% 11% 1	4312
September	1st to 10th	Day	40% 8% 14% 19% 15% 5%	2400
	11th to 20th	Day	46% 7% 10% 15% 18% 4	2290
	21st to end	Day	46% 6% 10% 19% 15% 4	2140
October	1st to 10th	Day	39% 4 7% 21% 24% 6%	3260
	11th to 20th	Day	21% 3 5% 19% 26% 26%	3240
	21st to end	Day	27% 4 5% 21% 29% 14%	3538
November	1st to 10th	Day	32% 3 8% 19% 28% 10%	2057
	11th to 20th	Day	36% 3 6% 19% 27% 9%	2100
	21st to end	Day	35% 3 8% 21% 24% 8%	1969
December	1st to 10th	Day	36% 4 8% 17% 23% 12%	2758
	11th to 20th	Day	40% 4 10% 19% 19% 7%	3433
	21st to end	Day	39% 4 11% 22% 22% 2	4466
January	1st to 10th	Night	32% 3 5% 17% 37% 7%	5889
	11th to 20th	Night	37% 3 5% 14% 33% 7%	5900
	21st to end	Night	41% 4 5% 15% 26% 9%	6490
February	1st to 10th	Night	41% 3 8% 19% 21% 7%	2600
	11th to 20th	Night	45% 4 7% 16% 21% 7%	2471
	21st to end	Night	39% 5% 7% 18% 21% 10%	1827
March	1st to 10th	Night	48% 4 6% 12% 23% 6%	4918
	11th to 20th	Night	33% 6% 7% 12% 26% 17%	4980
	21st to end	Night	36% 5% 9% 21% 22% 7%	5467
April	1st to 10th	Night	35% 4 12% 18% 23% 9%	2065
	11th to 20th	Night	34% 5% 11% 22% 20% 9%	1975
	21st to end	Night	33% 6% 12% 24% 20% 5%	2000
May	1st to 10th	Night	36% 8% 19% 23% 11% 2	4346
	11th to 20th	Night	45% 8% 15% 20% 12% 1	4033
	21st to end	Night	38% 8% 14% 22% 16% 1	4429
June	1st to 10th	Night	41% 9% 17% 22% 10% 1	1800
	11th to 20th	Night	39% 8% 17% 24% 10% 1	1800
	21st to end	Night	36% 11% 19% 24% 8% 1	1800
July	1st to 10th	Night	45% 11% 24% 15% 4 1	4015
	11th to 20th	Night	45% 14% 30% 9% 3	4006
	21st to end	Night	49% 10% 16% 18% 6%	4297
August	1st to 10th	Night	56% 9% 20% 13% 3	2904
	11th to 20th	Night	41% 12% 20% 20% 7%	3089
	21st to end	Night	32% 8% 16% 33% 11% 1	3586
September	1st to 10th	Night	37% 8% 18% 19% 15% 4	2000
	11th to 20th	Night	41% 8% 12% 19% 16% 3	2105
	21st to end	Night	46% 5% 12% 20% 13% 3	2259
October	1st to 10th	Night	39% 5% 8% 19% 23% 5%	3920
	11th to 20th	Night	22% 3 4 16% 25% 30%	3899
	21st to end	Night	26% 4 7% 24% 26% 15%	4252
November	1st to 10th	Night	34% 3 7% 18% 27% 11%	2461
	11th to 20th	Night	35% 3 8% 17% 26% 11%	2520
	21st to end	Night	34% 4 8% 22% 25% 7%	2646
December	1st to 10th	Night	34% 3 7% 13% 30% 12%	4539
	11th to 20th	Night	42% 5% 12% 16% 18% 7%	4916
	21st to end	Night	38% 5% 10% 23% 22% 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	22% 26% 35% 15% 2	300
	11th to 20th	Day	22% 22% 35% 16% 4	300
	21st to end	Day	25% 22% 37% 12% 3	330
February	1st to 10th	Day	24% 20% 38% 15% 3	300
	11th to 20th	Day	33% 20% 34% 11% 2	361
	21st to end	Day	23% 19% 34% 21% 3	414
March	1st to 10th	Day	23% 19% 31% 20% 6% 1	500
	11th to 20th	Day	21% 24% 34% 15% 5% 1	500
	21st to end	Day	19% 19% 38% 17% 5% 1	550
April	1st to 10th	Day	22% 17% 32% 21% 6% 1	500
	11th to 20th	Day	14% 17% 31% 21% 12% 5%	492
	21st to end	Day	14% 12% 31% 25% 15% 3	500
May	1st to 10th	Day	11% 17% 32% 24% 12% 4	503
	11th to 20th	Day	16% 8% 24% 30% 15% 6%	527
	21st to end	Day	18% 5% 19% 28% 20% 10%	573
June	1st to 10th	Day	15% 4 22% 32% 23% 5%	530
	11th to 20th	Day	12% 3 21% 31% 23% 10%	530
	21st to end	Day	9% 3 17% 36% 26% 10%	530
July	1st to 10th	Day	12% 3 12% 29% 31% 14%	525
	11th to 20th	Day	13% 1 8% 35% 33% 12%	524
	21st to end	Day	7% 3 13% 35% 33% 9%	576
August	1st to 10th	Day	16% 5% 15% 27% 25% 12%	526
	11th to 20th	Day	16% 3 12% 28% 28% 15%	519
	21st to end	Day	14% 3 14% 33% 23% 13%	583
September	1st to 10th	Day	11% 3 19% 31% 22% 14%	530
	11th to 20th	Day	18% 5% 14% 31% 22% 8%	530
	21st to end	Day	20% 4 21% 30% 16% 9%	530
October	1st to 10th	Day	18% 5% 24% 28% 18% 7%	530
	11th to 20th	Day	14% 12% 25% 29% 17% 4	530
	21st to end	Day	14% 11% 27% 25% 18% 4	583
November	1st to 10th	Day	16% 9% 30% 30% 12% 4	535
	11th to 20th	Day	18% 14% 35% 23% 9% 1	540
	21st to end	Day	14% 18% 35% 22% 10% 1	409
December	1st to 10th	Day	22% 19% 35% 18% 6%	246
	11th to 20th	Day	20% 17% 36% 18% 8% 2	321
	21st to end	Day	22% 17% 36% 15% 6% 3	330
January	1st to 10th	Night	20% 18% 32% 23% 6%	800
	11th to 20th	Night	18% 16% 28% 32% 6%	800
	21st to end	Night	20% 15% 34% 27% 3	880
February	1st to 10th	Night	21% 15% 33% 25% 6%	800
	11th to 20th	Night	24% 19% 33% 22% 2	783
	21st to end	Night	21% 17% 31% 27% 5%	660
March	1st to 10th	Night	20% 13% 35% 27% 5%	800
	11th to 20th	Night	18% 14% 37% 25% 6% 1	800
	21st to end	Night	17% 15% 37% 25% 6%	880
April	1st to 10th	Night	17% 17% 37% 24% 6%	800
	11th to 20th	Night	14% 14% 34% 29% 10%	791
	21st to end	Night	13% 9% 36% 34% 8% 1	800
May	1st to 10th	Night	10% 9% 38% 32% 11%	730
	11th to 20th	Night	17% 7% 24% 40% 12% 1	591
	21st to end	Night	12% 2 15% 41% 27% 3	650
June	1st to 10th	Night	12% 3 20% 44% 19% 2	600
	11th to 20th	Night	12% 2 16% 37% 27% 5%	600
	21st to end	Night	9% 2 17% 40% 29% 3	600
July	1st to 10th	Night	9% 2 11% 42% 33% 4	585
	11th to 20th	Night	9% 2 8% 40% 35% 6%	582
	21st to end	Night	9% 2 11% 46% 29% 4	657
August	1st to 10th	Night	16% 2 10% 38% 30% 5%	597
	11th to 20th	Night	13% 1 9% 37% 33% 6%	703
	21st to end	Night	12% 2 14% 35% 31% 7%	880
September	1st to 10th	Night	11% 3 11% 41% 30% 4	800
	11th to 20th	Night	16% 3 16% 35% 26% 4	800
	21st to end	Night	23% 3 17% 33% 22% 3	800
October	1st to 10th	Night	16% 4 21% 32% 24% 4	800
	11th to 20th	Night	16% 6% 26% 30% 19% 3	800
	21st to end	Night	14% 8% 26% 32% 18% 3	880
November	1st to 10th	Night	15% 8% 25% 33% 15% 3	820
	11th to 20th	Night	20% 10% 29% 27% 12% 1	840
	21st to end	Night	16% 12% 28% 30% 13% 2	840
December	1st to 10th	Night	22% 12% 27% 32% 7%	840
	11th to 20th	Night	19% 11% 27% 34% 10%	829
	21st to end	Night	20% 13% 28% 29% 9% 1	880

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