Brownington State Wildlife Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brownington State Wildlife Area clear sky chart from 2005-11-06 to 2026-02-01.

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 3 5% 7% 45%	127207
	Night	12% 7% 3 6% 4 3 4 3 5% 7% 47%	125045
Transparency	Day	38% 5% 11% 26% 17% 3	130819
	Night	37% 4 10% 26% 19% 4	129509
Seeing	Day	16% 7% 26% 28% 18% 5%	17260
	Night	16% 8% 29% 32% 14% 1	27200

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	18% 9% 3 8% 5% 4 4 3 4 5% 37%	4167
	11th to 20th	Day	8% 11% 4 9% 4 7% 4 3 5% 5% 40%	4170
	21st to end	Day	16% 12% 3 7% 3 3 4 3 4 5% 40%	4587
February	1st to 10th	Day	16% 12% 4 8% 5% 4 4 3 4 5% 37%	1800
	11th to 20th	Day	15% 10% 4 7% 3 5% 4 2 5% 5% 40%	1754
	21st to end	Day	15% 10% 3 6% 4 4 4 3 5% 6% 40%	1715
March	1st to 10th	Day	14% 9% 3 5% 3 3 2 3 4 5% 50%	4936
	11th to 20th	Day	11% 6% 2 4 3 3 3 3 4 6% 54%	4980
	21st to end	Day	14% 10% 3 7% 5% 5% 4 4 5% 7% 35%	5462
April	1st to 10th	Day	15% 7% 3 6% 5% 3 4 3 4 6% 44%	2352
	11th to 20th	Day	17% 8% 2 5% 3 4 4 4 5% 6% 42%	2374
	21st to end	Day	21% 8% 3 8% 4 4 4 3 5% 6% 35%	2438
May	1st to 10th	Day	16% 7% 2 7% 5% 4 4 4 5% 8% 38%	5862
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 3 6% 8% 43%	5862
	21st to end	Day	19% 7% 2 5% 4 4 4 3 5% 7% 40%	6744
June	1st to 10th	Day	7% 5% 2 5% 4 4 5% 4 6% 10% 49%	2800
	11th to 20th	Day	9% 4 2 5% 5% 5% 5% 4 6% 9% 47%	2800
	21st to end	Day	5% 3 1 4 4 4 4 4 7% 10% 53%	2800
July	1st to 10th	Day	9% 6% 3 6% 4 4 4 3 6% 8% 47%	6023
	11th to 20th	Day	7% 5% 2 7% 5% 4 5% 4 7% 10% 44%	5900
	21st to end	Day	6% 4 2 5% 5% 5% 6% 5% 9% 11% 42%	6422
August	1st to 10th	Day	4 4 1 5% 4 4 5% 4 6% 10% 53%	4234
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 6% 7% 47%	4148
	21st to end	Day	6% 4 2 4 3 4 4 4 5% 8% 57%	4312
September	1st to 10th	Day	11% 5% 2 5% 4 3 3 3 5% 7% 51%	2400
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 5% 7% 51%	2296
	21st to end	Day	8% 5% 2 5% 3 4 4 3 5% 6% 54%	2140
October	1st to 10th	Day	12% 5% 2 5% 3 3 3 2 4 6% 57%	2000
	11th to 20th	Day	14% 5% 2 5% 3 3 2 2 3 5% 55%	2000
	21st to end	Day	19% 7% 3 6% 3 3 2 2 3 5% 46%	2200
November	1st to 10th	Day	12% 7% 2 4 3 3 2 3 4 6% 55%	2058
	11th to 20th	Day	16% 7% 2 4 3 3 3 2 4 6% 49%	1849
	21st to end	Day	18% 9% 3 5% 3 3 3 2 4 6% 44%	1680
December	1st to 10th	Day	9% 8% 3 7% 3 3 3 3 5% 5% 51%	2690
	11th to 20th	Day	12% 8% 3 6% 4 3 4 3 4 5% 49%	3088
	21st to end	Day	20% 21% 6% 9% 3 3 3 2 3 5% 25%	4164
January	1st to 10th	Night	14% 10% 5% 13% 6% 4 3 2 3 4 35%	6018
	11th to 20th	Night	11% 8% 3 11% 6% 6% 4 3 3 4 40%	6030
	21st to end	Night	16% 11% 3 7% 3 3 3 3 3 6% 41%	6633
February	1st to 10th	Night	14% 11% 4 7% 5% 4 3 4 5% 6% 38%	2601
	11th to 20th	Night	14% 10% 3 7% 4 3 3 3 4 6% 42%	2533
	21st to end	Night	15% 8% 3 6% 3 3 3 3 4 6% 44%	1928
March	1st to 10th	Night	16% 9% 3 5% 4 3 3 3 4 5% 46%	4919
	11th to 20th	Night	11% 6% 2 4 3 2 3 3 4 7% 54%	4980
	21st to end	Night	14% 7% 3 8% 4 5% 5% 4 6% 7% 38%	5467
April	1st to 10th	Night	11% 7% 2 5% 3 3 3 3 5% 7% 50%	2046
	11th to 20th	Night	14% 8% 2 6% 3 3 4 3 4 6% 47%	1975
	21st to end	Night	18% 7% 2 7% 5% 4 3 2 4 7% 41%	1958
May	1st to 10th	Night	17% 7% 3 6% 3 3 4 3 5% 7% 42%	4053
	11th to 20th	Night	13% 8% 2 6% 3 3 4 3 5% 9% 45%	4053
	21st to end	Night	16% 6% 2 5% 3 3 4 3 4 6% 48%	4130
June	1st to 10th	Night	7% 3 1 5% 3 3 4 4 7% 9% 54%	1600
	11th to 20th	Night	5% 4 1 4 4 4 4 4 9% 11% 51%	1600
	21st to end	Night	4 3 1 3 3 3 4 3 7% 10% 60%	1600
July	1st to 10th	Night	9% 6% 2 6% 4 3 4 3 6% 10% 47%	3936
	11th to 20th	Night	5% 4 2 5% 4 4 4 3 6% 11% 52%	4077
	21st to end	Night	5% 4 2 5% 4 4 5% 5% 8% 12% 48%	4449
August	1st to 10th	Night	3 2 1 3 2 3 3 4 5% 9% 64%	2926
	11th to 20th	Night	9% 5% 3 6% 4 4 4 3 5% 6% 52%	2910
	21st to end	Night	3 3 1 4 3 4 4 4 6% 8% 59%	3586
September	1st to 10th	Night	11% 4 2 4 3 3 3 3 5% 7% 57%	2000
	11th to 20th	Night	10% 4 1 5% 4 3 5% 3 6% 7% 52%	2100
	21st to end	Night	8% 4 2 4 3 3 4 4 5% 6% 57%	2238
October	1st to 10th	Night	8% 4 1 4 3 3 3 3 4 6% 60%	2400
	11th to 20th	Night	14% 4 1 5% 3 3 3 3 3 5% 55%	2400
	21st to end	Night	17% 6% 1 5% 4 2 3 3 4 5% 50%	2640
November	1st to 10th	Night	12% 5% 2 3 3 2 3 2 4 6% 58%	2460
	11th to 20th	Night	11% 7% 2 5% 4 3 3 3 3 6% 53%	2762
	21st to end	Night	17% 9% 2 5% 3 3 3 2 4 5% 48%	2940
December	1st to 10th	Night	10% 8% 2 5% 3 3 3 3 5% 5% 52%	4720
	11th to 20th	Night	15% 9% 3 6% 3 3 3 3 4 6% 45%	5339
	21st to end	Night	21% 18% 5% 9% 4 3 3 2 3 4 28%	7038

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	50% 4 8% 25% 12% 1	4168
	11th to 20th	Day	45% 4 8% 24% 15% 4	4170
	21st to end	Day	48% 3 9% 18% 16% 6%	4587
February	1st to 10th	Day	52% 4 10% 23% 11% 2	1800
	11th to 20th	Day	47% 3 13% 20% 15% 3	1763
	21st to end	Day	45% 4 8% 24% 14% 5%	1715
March	1st to 10th	Day	39% 3 7% 23% 23% 6%	4936
	11th to 20th	Day	32% 4 8% 23% 25% 8%	4980
	21st to end	Day	49% 5% 16% 24% 5% 1	5464
April	1st to 10th	Day	42% 4 11% 24% 16% 3	2352
	11th to 20th	Day	42% 5% 12% 25% 15% 1	2374
	21st to end	Day	50% 5% 11% 23% 11% 1	2438
May	1st to 10th	Day	44% 6% 12% 23% 14% 1	5900
	11th to 20th	Day	39% 6% 13% 24% 15% 3	5866
	21st to end	Day	44% 6% 10% 27% 13% 1	6758
June	1st to 10th	Day	31% 6% 18% 27% 17% 2	2800
	11th to 20th	Day	32% 7% 14% 30% 15% 2	2800
	21st to end	Day	25% 6% 17% 33% 15% 4	2800
July	1st to 10th	Day	35% 5% 12% 25% 21% 2	5959
	11th to 20th	Day	34% 6% 13% 31% 14% 1	5831
	21st to end	Day	30% 8% 19% 32% 10%	6240
August	1st to 10th	Day	26% 5% 18% 29% 21% 1	4220
	11th to 20th	Day	35% 6% 16% 28% 15% 1	4187
	21st to end	Day	26% 5% 13% 39% 14% 4	4311
September	1st to 10th	Day	33% 4 12% 26% 18% 7%	2400
	11th to 20th	Day	33% 4 9% 27% 25% 2	2296
	21st to end	Day	31% 4 10% 27% 24% 4	2140
October	1st to 10th	Day	19% 2 6% 21% 38% 14%	3260
	11th to 20th	Day	23% 2 3 24% 39% 9%	3240
	21st to end	Day	36% 3 7% 26% 24% 3	3538
November	1st to 10th	Day	32% 3 10% 30% 21% 4	2058
	11th to 20th	Day	38% 2 9% 24% 22% 5%	1849
	21st to end	Day	43% 3 9% 28% 17% 1	1680
December	1st to 10th	Day	35% 3 10% 36% 15% 1	2690
	11th to 20th	Day	40% 2 10% 31% 16% 2	3085
	21st to end	Day	64% 3 10% 16% 6% 1	4164
January	1st to 10th	Night	54% 3 10% 21% 11% 1	6018
	11th to 20th	Night	49% 3 7% 24% 14% 3	6030
	21st to end	Night	46% 3 9% 20% 16% 5%	6633
February	1st to 10th	Night	47% 4 10% 23% 14% 2	2601
	11th to 20th	Night	45% 3 11% 23% 16% 3	2534
	21st to end	Night	42% 3 7% 24% 18% 6%	1928
March	1st to 10th	Night	43% 3 7% 20% 23% 5%	4919
	11th to 20th	Night	31% 3 7% 22% 30% 7%	4980
	21st to end	Night	43% 6% 13% 25% 11% 2	5467
April	1st to 10th	Night	34% 4 12% 23% 23% 4	2046
	11th to 20th	Night	38% 4 9% 26% 19% 5%	1975
	21st to end	Night	45% 4 10% 26% 13% 1	1958
May	1st to 10th	Night	42% 6% 14% 22% 14% 1	4080
	11th to 20th	Night	36% 6% 13% 23% 16% 6%	4054
	21st to end	Night	37% 5% 10% 26% 20% 2	4138
June	1st to 10th	Night	25% 6% 17% 31% 18% 3	1600
	11th to 20th	Night	25% 8% 14% 30% 21% 3	1600
	21st to end	Night	19% 4 17% 33% 22% 6%	1600
July	1st to 10th	Night	33% 5% 13% 25% 22% 2	3893
	11th to 20th	Night	27% 5% 12% 37% 17% 2	4026
	21st to end	Night	26% 6% 17% 38% 12% 1	4320
August	1st to 10th	Night	17% 6% 19% 33% 22% 3	2916
	11th to 20th	Night	34% 4 10% 32% 19% 1	2937
	21st to end	Night	22% 5% 13% 38% 18% 4	3586
September	1st to 10th	Night	27% 5% 11% 29% 21% 7%	2000
	11th to 20th	Night	31% 5% 10% 25% 25% 5%	2100
	21st to end	Night	27% 5% 7% 26% 30% 5%	2238
October	1st to 10th	Night	16% 3 6% 21% 42% 13%	3920
	11th to 20th	Night	24% 2 5% 23% 29% 16%	3899
	21st to end	Night	31% 3 7% 31% 25% 3	4252
November	1st to 10th	Night	29% 4 10% 29% 22% 6%	2460
	11th to 20th	Night	34% 3 7% 26% 25% 5%	2762
	21st to end	Night	40% 3 9% 27% 18% 3	2940
December	1st to 10th	Night	35% 3 11% 35% 15% 1	4720
	11th to 20th	Night	42% 3 10% 27% 17% 2	5341
	21st to end	Night	62% 3 9% 19% 7% 1	7038

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% 11% 36% 27% 5%	330
	11th to 20th	Day	24% 15% 45% 15% 1	330
	21st to end	Day	18% 11% 49% 18% 4	363
February	1st to 10th	Day	24% 15% 39% 20% 3	300
	11th to 20th	Day	21% 19% 38% 15% 5%	300
	21st to end	Day	22% 17% 41% 15% 4	249
March	1st to 10th	Day	20% 16% 39% 21% 4	300
	11th to 20th	Day	27% 11% 37% 19% 6%	300
	21st to end	Day	32% 11% 38% 12% 5% 2	330
April	1st to 10th	Day	23% 16% 33% 21% 6% 1	452
	11th to 20th	Day	23% 13% 35% 22% 7%	492
	21st to end	Day	24% 9% 33% 23% 10%	538
May	1st to 10th	Day	20% 9% 34% 27% 8% 1	703
	11th to 20th	Day	19% 9% 25% 29% 14% 3	725
	21st to end	Day	18% 5% 28% 26% 17% 7%	789
June	1st to 10th	Day	8% 2 16% 36% 28% 9%	730
	11th to 20th	Day	10% 2 19% 38% 25% 5%	730
	21st to end	Day	6% 4 26% 36% 24% 4	730
July	1st to 10th	Day	11% 1 12% 30% 32% 14%	721
	11th to 20th	Day	4 2 16% 37% 31% 10%	718
	21st to end	Day	9% 2 12% 32% 34% 11%	794
August	1st to 10th	Day	8% 2 12% 38% 33% 7%	726
	11th to 20th	Day	10% 2 13% 35% 33% 8%	705
	21st to end	Day	10% 1 9% 29% 37% 13%	583
September	1st to 10th	Day	11% 3 10% 34% 34% 9%	530
	11th to 20th	Day	8% 3 13% 38% 28% 10%	426
	21st to end	Day	14% 4 19% 30% 26% 8%	330
October	1st to 10th	Day	13% 5% 24% 30% 21% 8%	330
	11th to 20th	Day	16% 13% 32% 28% 9% 2	330
	21st to end	Day	30% 9% 32% 21% 6% 1	363
November	1st to 10th	Day	18% 10% 36% 24% 8% 4	330
	11th to 20th	Day	19% 16% 32% 20% 11% 1	330
	21st to end	Day	28% 12% 28% 26% 6%	330
December	1st to 10th	Day	15% 11% 42% 21% 8% 2	330
	11th to 20th	Day	20% 12% 40% 22% 6% 1	330
	21st to end	Day	25% 16% 37% 21% 1	363
January	1st to 10th	Night	17% 14% 36% 27% 5%	1050
	11th to 20th	Night	19% 15% 37% 23% 5%	1050
	21st to end	Night	18% 12% 39% 27% 3	1155
February	1st to 10th	Night	20% 13% 38% 25% 3	1001
	11th to 20th	Night	20% 13% 38% 26% 3	979
	21st to end	Night	22% 14% 40% 21% 3	608
March	1st to 10th	Night	19% 12% 38% 27% 4	600
	11th to 20th	Night	23% 11% 31% 30% 5% 1	600
	21st to end	Night	24% 10% 37% 25% 4	660
April	1st to 10th	Night	17% 10% 34% 33% 6% 1	600
	11th to 20th	Night	20% 11% 30% 31% 7%	593
	21st to end	Night	21% 6% 37% 27% 8%	600
May	1st to 10th	Night	17% 7% 31% 34% 11%	600
	11th to 20th	Night	16% 4 26% 36% 16% 1	591
	21st to end	Night	14% 4 27% 33% 21% 2	650
June	1st to 10th	Night	8% 2 16% 40% 31% 3	600
	11th to 20th	Night	7% 1 20% 43% 26% 3	600
	21st to end	Night	5% 2 23% 48% 21% 1	600
July	1st to 10th	Night	11% 1 10% 38% 35% 5%	585
	11th to 20th	Night	3 1 13% 42% 37% 4	582
	21st to end	Night	8% 1 11% 39% 39% 3	657
August	1st to 10th	Night	7% 2 11% 43% 34% 3	597
	11th to 20th	Night	8% 1 10% 47% 31% 4	594
	21st to end	Night	5% 1 10% 37% 42% 5%	660
September	1st to 10th	Night	12% 1 13% 41% 29% 4	600
	11th to 20th	Night	12% 3 12% 38% 30% 5%	600
	21st to end	Night	9% 3 20% 39% 24% 4	638
October	1st to 10th	Night	10% 4 25% 36% 23% 3	800
	11th to 20th	Night	16% 7% 34% 33% 10% 1	800
	21st to end	Night	20% 11% 32% 29% 8% 1	880
November	1st to 10th	Night	14% 9% 36% 30% 11% 1	820
	11th to 20th	Night	17% 12% 38% 26% 8%	945
	21st to end	Night	21% 12% 35% 24% 7%	1050
December	1st to 10th	Night	20% 11% 36% 27% 6%	1050
	11th to 20th	Night	23% 9% 34% 29% 5%	1050
	21st to end	Night	23% 12% 35% 26% 3	1155

Page generated at 2026-01-29 00:21:40. Version ac07

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