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 2024-11-28.

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%	101257
	Night	12% 7% 2 6% 4 3 4 3 5% 7% 47%	98346
Transparency	Day	38% 5% 12% 26% 17% 3	104908
	Night	36% 4 11% 26% 19% 4	102835
Seeing	Day	16% 7% 25% 28% 19% 5%	15691
	Night	16% 8% 29% 32% 14% 1	25533

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	16% 9% 4 8% 4 4 4 3 4 5% 39%	2847
	11th to 20th	Day	12% 13% 4 9% 4 7% 4 2 4 4 37%	2850
	21st to end	Day	18% 14% 4 8% 3 3 3 2 4 5% 36%	3135
February	1st to 10th	Day	15% 12% 4 8% 5% 4 4 3 4 5% 37%	1710
	11th to 20th	Day	14% 10% 4 7% 3 4 4 3 5% 5% 41%	1664
	21st to end	Day	16% 10% 3 6% 4 4 4 3 5% 6% 39%	1631
March	1st to 10th	Day	16% 10% 3 6% 3 3 3 2 4 4 47%	3436
	11th to 20th	Day	14% 8% 2 5% 3 3 3 3 4 6% 50%	3480
	21st to end	Day	18% 12% 3 7% 5% 4 4 3 4 6% 34%	3814
April	1st to 10th	Day	14% 7% 3 6% 5% 3 4 3 4 6% 45%	2234
	11th to 20th	Day	17% 7% 2 5% 4 4 4 4 5% 7% 42%	2254
	21st to end	Day	21% 8% 3 7% 4 4 4 3 5% 6% 35%	2316
May	1st to 10th	Day	17% 8% 3 7% 5% 4 4 4 5% 7% 36%	4082
	11th to 20th	Day	15% 8% 3 6% 5% 4 4 3 5% 7% 41%	4082
	21st to end	Day	12% 6% 2 6% 4 5% 5% 3 6% 8% 42%	4689
June	1st to 10th	Day	6% 5% 2 5% 4 4 5% 4 7% 10% 49%	2660
	11th to 20th	Day	8% 4 2 5% 5% 5% 5% 4 6% 9% 48%	2660
	21st to end	Day	5% 3 1 4 4 4 4 4 7% 10% 54%	2660
July	1st to 10th	Day	11% 7% 3 7% 4 4 4 3 6% 8% 43%	4201
	11th to 20th	Day	4 4 2 6% 4 4 5% 4 6% 9% 51%	4120
	21st to end	Day	6% 4 2 5% 5% 5% 6% 5% 9% 12% 42%	4465
August	1st to 10th	Day	4 4 1 5% 4 4 5% 4 6% 10% 53%	4104
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 6% 7% 47%	4019
	21st to end	Day	6% 3 1 4 3 4 4 3 5% 9% 58%	4180
September	1st to 10th	Day	11% 5% 2 5% 4 3 3 3 5% 7% 52%	2280
	11th to 20th	Day	10% 5% 2 5% 4 4 3 3 5% 7% 52%	2181
	21st to end	Day	8% 5% 2 6% 3 3 4 3 5% 7% 55%	2033
October	1st to 10th	Day	12% 5% 2 5% 3 3 3 2 3 6% 57%	1900
	11th to 20th	Day	14% 5% 2 5% 3 3 2 2 3 5% 55%	1900
	21st to end	Day	18% 7% 3 6% 3 3 3 2 3 5% 47%	2090
November	1st to 10th	Day	12% 7% 2 4 3 3 2 3 4 6% 54%	1958
	11th to 20th	Day	16% 7% 2 4 3 3 3 2 4 6% 49%	1761
	21st to end	Day	17% 9% 3 5% 3 3 3 2 3 6% 46%	1576
December	1st to 10th	Day	13% 10% 4 7% 3 3 4 3 4 6% 44%	1520
	11th to 20th	Day	14% 11% 3 7% 5% 4 4 2 4 4 43%	1918
	21st to end	Day	19% 16% 5% 8% 3 3 4 3 4 6% 27%	2847
January	1st to 10th	Night	10% 10% 4 13% 5% 4 3 2 3 5% 40%	4108
	11th to 20th	Night	13% 9% 3 10% 7% 8% 5% 3 3 4 34%	4120
	21st to end	Night	20% 14% 4 7% 3 3 3 3 3 5% 36%	4532
February	1st to 10th	Night	13% 11% 4 7% 5% 4 3 4 5% 6% 38%	2470
	11th to 20th	Night	14% 9% 3 7% 4 3 3 3 4 6% 43%	2403
	21st to end	Night	16% 9% 4 6% 3 3 3 3 4 6% 43%	1835
March	1st to 10th	Night	16% 9% 2 5% 4 3 3 3 4 5% 46%	3419
	11th to 20th	Night	13% 6% 2 5% 3 2 3 3 4 7% 52%	3480
	21st to end	Night	17% 8% 4 9% 4 4 4 4 5% 6% 35%	3817
April	1st to 10th	Night	11% 7% 2 6% 3 3 3 3 5% 7% 51%	1944
	11th to 20th	Night	14% 8% 2 6% 3 3 4 3 4 6% 47%	1875
	21st to end	Night	18% 7% 2 8% 5% 4 3 2 4 6% 41%	1860
May	1st to 10th	Night	16% 7% 3 6% 4 4 5% 4 5% 6% 40%	2823
	11th to 20th	Night	14% 8% 2 6% 4 3 4 3 6% 8% 41%	2823
	21st to end	Night	11% 5% 2 5% 4 3 4 3 4 7% 51%	2875
June	1st to 10th	Night	7% 3 1 5% 3 3 4 4 7% 10% 55%	1520
	11th to 20th	Night	4 4 1 4 4 4 4 4 9% 10% 51%	1520
	21st to end	Night	4 3 1 3 3 3 3 3 7% 10% 60%	1520
July	1st to 10th	Night	11% 7% 2 6% 3 3 3 2 5% 10% 46%	2750
	11th to 20th	Night	3 3 1 4 4 3 4 3 6% 11% 59%	2850
	21st to end	Night	5% 4 2 5% 4 4 4 4 7% 12% 50%	3098
August	1st to 10th	Night	3 2 1 3 2 3 3 4 5% 9% 64%	2836
	11th to 20th	Night	9% 5% 3 6% 4 4 4 3 5% 6% 52%	2819
	21st to end	Night	3 3 1 4 3 4 4 4 6% 8% 59%	3476
September	1st to 10th	Night	11% 3 2 4 3 3 2 3 4 7% 58%	1900
	11th to 20th	Night	10% 4 2 5% 3 3 4 3 6% 6% 53%	1995
	21st to end	Night	8% 4 2 5% 4 3 4 4 4 6% 58%	2126
October	1st to 10th	Night	8% 4 1 4 3 3 3 3 4 6% 60%	2280
	11th to 20th	Night	14% 4 1 4 3 3 3 3 3 5% 56%	2280
	21st to end	Night	16% 6% 1 5% 4 3 3 3 4 5% 51%	2508
November	1st to 10th	Night	12% 5% 2 3 3 2 3 2 4 6% 58%	2340
	11th to 20th	Night	11% 7% 2 5% 4 3 3 3 3 6% 52%	2630
	21st to end	Night	16% 8% 2 4 3 3 3 2 4 5% 48%	2759
December	1st to 10th	Night	14% 10% 3 5% 4 4 3 4 5% 5% 44%	2660
	11th to 20th	Night	15% 9% 3 6% 4 3 3 3 5% 6% 43%	3279
	21st to end	Night	20% 18% 5% 9% 4 3 3 3 3 4 29%	4816

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	47% 5% 7% 27% 13%	2848
	11th to 20th	Day	50% 6% 10% 23% 11%	2850
	21st to end	Day	52% 4 9% 18% 16% 1	3135
February	1st to 10th	Day	51% 4 10% 23% 11% 2	1710
	11th to 20th	Day	45% 3 13% 21% 15% 3	1673
	21st to end	Day	46% 4 9% 23% 14% 5%	1631
March	1st to 10th	Day	42% 3 8% 23% 21% 3	3436
	11th to 20th	Day	36% 4 11% 28% 17% 4	3480
	21st to end	Day	50% 6% 17% 20% 6% 1	3814
April	1st to 10th	Day	41% 4 12% 24% 16% 2	2234
	11th to 20th	Day	42% 5% 12% 24% 15% 1	2254
	21st to end	Day	49% 5% 11% 23% 11% 1	2316
May	1st to 10th	Day	47% 6% 12% 21% 13% 1	4120
	11th to 20th	Day	42% 7% 13% 24% 14%	4086
	21st to end	Day	39% 7% 11% 29% 13% 1	4702
June	1st to 10th	Day	30% 6% 19% 27% 16% 2	2660
	11th to 20th	Day	31% 8% 14% 30% 15% 2	2660
	21st to end	Day	25% 6% 17% 33% 15% 4	2660
July	1st to 10th	Day	39% 6% 12% 24% 17% 3	4137
	11th to 20th	Day	29% 6% 12% 34% 17% 2	4051
	21st to end	Day	30% 9% 21% 29% 11% 1	4325
August	1st to 10th	Day	26% 5% 18% 28% 22% 1	4090
	11th to 20th	Day	35% 6% 16% 27% 14% 1	4058
	21st to end	Day	25% 5% 14% 39% 14% 4	4179
September	1st to 10th	Day	33% 4 12% 26% 18% 7%	2280
	11th to 20th	Day	32% 4 9% 26% 27% 2	2181
	21st to end	Day	30% 4 10% 28% 23% 4	2033
October	1st to 10th	Day	19% 2 6% 21% 38% 15%	3160
	11th to 20th	Day	22% 2 3 24% 39% 10%	3140
	21st to end	Day	36% 3 7% 26% 25% 3	3428
November	1st to 10th	Day	32% 4 10% 28% 21% 4	1958
	11th to 20th	Day	38% 2 9% 24% 22% 5%	1761
	21st to end	Day	42% 3 9% 28% 18% 1	1576
December	1st to 10th	Day	41% 4 10% 31% 12% 1	1520
	11th to 20th	Day	46% 3 10% 27% 13% 2	1915
	21st to end	Day	59% 4 10% 18% 8% 1	2847
January	1st to 10th	Night	47% 4 13% 23% 12% 1	4108
	11th to 20th	Night	53% 4 9% 23% 11% 1	4120
	21st to end	Night	53% 3 11% 21% 11% 1	4532
February	1st to 10th	Night	47% 4 10% 23% 14% 2	2470
	11th to 20th	Night	43% 3 11% 24% 16% 3	2404
	21st to end	Night	43% 3 7% 23% 17% 6%	1835
March	1st to 10th	Night	41% 4 9% 21% 20% 5%	3419
	11th to 20th	Night	33% 4 10% 24% 26% 3	3480
	21st to end	Night	47% 7% 13% 24% 8% 1	3817
April	1st to 10th	Night	34% 4 11% 23% 23% 4	1944
	11th to 20th	Night	38% 4 9% 25% 19% 5%	1875
	21st to end	Night	44% 4 10% 26% 14% 1	1860
May	1st to 10th	Night	42% 8% 13% 20% 15% 2	2850
	11th to 20th	Night	40% 8% 13% 27% 11% 1	2824
	21st to end	Night	32% 6% 12% 27% 21% 1	2883
June	1st to 10th	Night	24% 6% 17% 31% 18% 3	1520
	11th to 20th	Night	24% 8% 14% 30% 21% 3	1520
	21st to end	Night	18% 4 16% 33% 22% 6%	1520
July	1st to 10th	Night	36% 4 12% 26% 19% 3	2705
	11th to 20th	Night	20% 4 11% 39% 23% 3	2796
	21st to end	Night	26% 6% 19% 34% 14% 1	2999
August	1st to 10th	Night	17% 6% 19% 32% 23% 3	2826
	11th to 20th	Night	34% 4 10% 31% 20% 1	2846
	21st to end	Night	22% 5% 13% 38% 18% 4	3476
September	1st to 10th	Night	26% 5% 11% 29% 22% 8%	1900
	11th to 20th	Night	31% 5% 10% 24% 26% 5%	1995
	21st to end	Night	27% 4 7% 27% 30% 4	2126
October	1st to 10th	Night	16% 3 6% 21% 42% 13%	3800
	11th to 20th	Night	23% 3 5% 23% 29% 17%	3779
	21st to end	Night	31% 3 7% 31% 25% 3	4120
November	1st to 10th	Night	29% 4 11% 28% 22% 6%	2340
	11th to 20th	Night	35% 3 6% 26% 25% 5%	2630
	21st to end	Night	39% 3 8% 27% 19% 3	2759
December	1st to 10th	Night	42% 4 12% 24% 16% 1	2660
	11th to 20th	Night	43% 3 10% 29% 14% 1	3281
	21st to end	Night	60% 4 8% 17% 9% 2	4816

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% 33% 29% 6%	270
	11th to 20th	Day	29% 11% 44% 15% 1	270
	21st to end	Day	18% 10% 48% 19% 4	297
February	1st to 10th	Day	24% 14% 37% 22% 3	270
	11th to 20th	Day	20% 19% 39% 16% 6%	270
	21st to end	Day	24% 16% 40% 15% 4	225
March	1st to 10th	Day	19% 17% 40% 20% 4	270
	11th to 20th	Day	27% 10% 37% 19% 7%	270
	21st to end	Day	35% 11% 35% 12% 6% 2	297
April	1st to 10th	Day	19% 16% 35% 22% 7% 1	414
	11th to 20th	Day	22% 12% 36% 22% 7%	452
	21st to end	Day	25% 9% 33% 22% 10%	496
May	1st to 10th	Day	21% 9% 35% 27% 8% 1	653
	11th to 20th	Day	20% 8% 25% 30% 14% 4	675
	21st to end	Day	17% 5% 28% 26% 18% 7%	734
June	1st to 10th	Day	7% 2 15% 38% 29% 9%	680
	11th to 20th	Day	10% 3 19% 39% 24% 5%	680
	21st to end	Day	6% 4 27% 35% 25% 5%	680
July	1st to 10th	Day	12% 1 12% 30% 32% 14%	671
	11th to 20th	Day	4 2 15% 37% 32% 10%	668
	21st to end	Day	9% 2 12% 32% 34% 11%	739
August	1st to 10th	Day	9% 2 11% 37% 34% 7%	676
	11th to 20th	Day	10% 2 14% 35% 31% 7%	656
	21st to end	Day	10% 1 9% 29% 38% 14%	539
September	1st to 10th	Day	11% 3 9% 32% 35% 9%	490
	11th to 20th	Day	8% 2 14% 39% 27% 10%	391
	21st to end	Day	14% 3 20% 32% 24% 7%	300
October	1st to 10th	Day	13% 5% 24% 29% 20% 8%	300
	11th to 20th	Day	16% 12% 32% 29% 9% 2	300
	21st to end	Day	29% 9% 32% 22% 6% 1	330
November	1st to 10th	Day	19% 10% 35% 24% 8% 4	300
	11th to 20th	Day	19% 16% 31% 21% 11% 1	300
	21st to end	Day	26% 12% 28% 28% 6%	291
December	1st to 10th	Day	16% 9% 41% 22% 9% 3	270
	11th to 20th	Day	23% 10% 35% 24% 6% 1	270
	21st to end	Day	24% 18% 36% 22% 1	297
January	1st to 10th	Night	17% 14% 36% 28% 6%	950
	11th to 20th	Night	20% 15% 35% 24% 5%	950
	21st to end	Night	18% 12% 38% 29% 4	1045
February	1st to 10th	Night	20% 12% 38% 25% 4	950
	11th to 20th	Night	19% 13% 38% 27% 3	929
	21st to end	Night	23% 14% 39% 20% 4	579
March	1st to 10th	Night	18% 12% 39% 27% 4	570
	11th to 20th	Night	23% 10% 30% 31% 5% 1	570
	21st to end	Night	25% 10% 35% 26% 4	627
April	1st to 10th	Night	16% 10% 33% 34% 6% 1	570
	11th to 20th	Night	20% 11% 30% 32% 7%	563
	21st to end	Night	21% 6% 38% 27% 8%	570
May	1st to 10th	Night	16% 7% 32% 34% 11%	570
	11th to 20th	Night	17% 3 25% 37% 16% 1	561
	21st to end	Night	14% 4 26% 33% 21% 2	617
June	1st to 10th	Night	8% 2 15% 41% 32% 2	570
	11th to 20th	Night	6% 1 21% 44% 25% 3	570
	21st to end	Night	5% 1 22% 48% 21% 1	570
July	1st to 10th	Night	11% 1 10% 37% 35% 5%	555
	11th to 20th	Night	3 1 13% 42% 38% 4	552
	21st to end	Night	8% 1 11% 39% 39% 3	624
August	1st to 10th	Night	7% 1 11% 42% 35% 3	567
	11th to 20th	Night	8% 1 10% 48% 29% 4	564
	21st to end	Night	5% 1 10% 36% 43% 4	627
September	1st to 10th	Night	12% 1 13% 41% 29% 5%	570
	11th to 20th	Night	13% 3 13% 38% 29% 5%	570
	21st to end	Night	10% 3 21% 39% 23% 4	606
October	1st to 10th	Night	10% 4 25% 35% 23% 3	760
	11th to 20th	Night	16% 7% 34% 33% 10% 1	760
	21st to end	Night	19% 11% 32% 29% 9% 1	836
November	1st to 10th	Night	14% 8% 36% 30% 11% 1	780
	11th to 20th	Night	17% 12% 37% 26% 8%	900
	21st to end	Night	20% 11% 36% 24% 8%	986
December	1st to 10th	Night	20% 10% 36% 27% 6%	950
	11th to 20th	Night	24% 8% 33% 31% 5%	950
	21st to end	Night	22% 13% 35% 26% 3	1045

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