West Point(PE)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Point(PE) clear sky chart from 2005-11-06 to 2026-04-17.

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	17% 10% 4 8% 5% 4 4 3 5% 7% 33%	131716
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 31%	130598
Transparency	Day	49% 7% 13% 20% 9% 1	135247
	Night	53% 6% 12% 19% 9% 1	135155
Seeing	Day	20% 8% 26% 30% 14% 2	18717
	Night	23% 9% 30% 28% 9% 1	26372

By Month

Percentage Cloud Cover NE (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% 19% 6% 14% 7% 4 5% 3 5% 5% 19%	4093
	11th to 20th	Day	16% 16% 8% 12% 5% 4 4 2 3 5% 24%	4279
	21st to end	Day	7% 10% 4 8% 6% 4 5% 3 6% 7% 40%	5781
February	1st to 10th	Day	14% 13% 4 9% 5% 4 4 4 5% 6% 31%	1890
	11th to 20th	Day	14% 14% 4 9% 5% 5% 4 3 4 6% 31%	1843
	21st to end	Day	11% 13% 4 8% 5% 5% 5% 4 5% 6% 35%	1557
March	1st to 10th	Day	19% 12% 5% 12% 4 5% 4 3 4 6% 25%	5014
	11th to 20th	Day	16% 12% 4 11% 6% 5% 5% 5% 6% 6% 25%	5090
	21st to end	Day	24% 14% 4 8% 5% 4 4 3 5% 6% 24%	5587
April	1st to 10th	Day	20% 11% 3 7% 5% 5% 3 4 5% 6% 31%	2506
	11th to 20th	Day	20% 10% 3 6% 4 4 3 3 5% 7% 34%	2586
	21st to end	Day	22% 10% 4 7% 4 4 4 3 4 7% 31%	2600
May	1st to 10th	Day	22% 13% 3 8% 5% 4 4 3 5% 6% 27%	6132
	11th to 20th	Day	19% 10% 3 6% 4 3 4 3 5% 6% 36%	6318
	21st to end	Day	18% 9% 3 7% 4 4 4 4 5% 7% 34%	6948
June	1st to 10th	Day	22% 9% 3 7% 5% 4 4 4 5% 7% 29%	2970
	11th to 20th	Day	17% 7% 2 6% 5% 4 5% 5% 5% 7% 37%	3000
	21st to end	Day	23% 8% 3 6% 5% 4 5% 3 5% 7% 31%	3000
July	1st to 10th	Day	14% 8% 3 7% 5% 6% 5% 4 7% 9% 31%	6820
	11th to 20th	Day	14% 5% 2 7% 4 4 5% 4 6% 8% 43%	6733
	21st to end	Day	11% 6% 3 6% 4 4 5% 4 6% 8% 43%	6867
August	1st to 10th	Day	15% 7% 3 8% 5% 5% 5% 4 6% 7% 36%	4235
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 6% 8% 41%	4175
	21st to end	Day	13% 5% 2 5% 3 3 4 4 5% 8% 48%	4558
September	1st to 10th	Day	14% 5% 2 6% 4 3 4 4 6% 8% 45%	2400
	11th to 20th	Day	17% 7% 2 6% 4 4 4 3 4 5% 45%	2309
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 7% 44%	2147
October	1st to 10th	Day	16% 10% 3 6% 4 3 3 3 5% 7% 40%	2000
	11th to 20th	Day	19% 9% 3 9% 5% 4 4 3 5% 7% 31%	2000
	21st to end	Day	20% 11% 3 8% 6% 4 4 4 4 7% 30%	2158
November	1st to 10th	Day	20% 12% 4 7% 5% 5% 4 3 4 5% 30%	1645
	11th to 20th	Day	21% 14% 6% 8% 5% 5% 4 3 4 6% 24%	1680
	21st to end	Day	17% 17% 5% 11% 6% 5% 4 3 6% 5% 22%	1680
December	1st to 10th	Day	18% 13% 8% 15% 7% 4 3 3 4 3 24%	2690
	11th to 20th	Day	19% 15% 5% 11% 5% 4 3 2 3 3 30%	2872
	21st to end	Day	16% 13% 5% 16% 7% 5% 4 3 4 5% 21%	3553
January	1st to 10th	Night	15% 17% 6% 13% 6% 4 4 2 4 5% 24%	8831
	11th to 20th	Night	18% 17% 6% 10% 6% 4 4 3 4 5% 24%	8601
	21st to end	Night	7% 12% 4 7% 6% 4 5% 4 5% 6% 40%	8400
February	1st to 10th	Night	15% 14% 4 9% 5% 4 5% 4 5% 6% 29%	2730
	11th to 20th	Night	16% 14% 4 10% 6% 5% 4 3 5% 5% 28%	2663
	21st to end	Night	12% 14% 3 8% 6% 4 4 3 5% 5% 35%	2249
March	1st to 10th	Night	22% 14% 4 11% 6% 5% 4 3 4 4 23%	5043
	11th to 20th	Night	21% 15% 4 9% 5% 5% 4 3 4 5% 24%	5089
	21st to end	Night	28% 13% 4 8% 4 3 3 3 4 4 25%	5587
April	1st to 10th	Night	22% 14% 3 8% 5% 4 4 3 5% 4 26%	2113
	11th to 20th	Night	22% 11% 3 8% 5% 3 4 4 5% 6% 30%	1895
	21st to end	Night	23% 11% 3 8% 4 4 4 3 4 5% 30%	1800
May	1st to 10th	Night	27% 11% 4 7% 4 4 4 3 5% 5% 26%	3817
	11th to 20th	Night	21% 8% 2 7% 5% 4 4 3 5% 6% 36%	3596
	21st to end	Night	18% 8% 3 7% 5% 5% 5% 3 5% 7% 33%	3948
June	1st to 10th	Night	23% 11% 3 8% 4 4 3 3 5% 7% 30%	1446
	11th to 20th	Night	19% 7% 3 6% 5% 4 5% 4 6% 6% 36%	1400
	21st to end	Night	22% 9% 3 6% 5% 6% 5% 5% 5% 5% 29%	1400
July	1st to 10th	Night	16% 7% 3 9% 5% 6% 5% 5% 7% 8% 29%	3160
	11th to 20th	Night	11% 6% 2 8% 6% 5% 5% 4 6% 9% 37%	3201
	21st to end	Night	14% 5% 2 7% 4 4 4 4 6% 9% 41%	3991
August	1st to 10th	Night	17% 6% 3 9% 6% 6% 6% 4 6% 8% 30%	2915
	11th to 20th	Night	11% 6% 3 8% 5% 6% 5% 4 5% 8% 40%	2872
	21st to end	Night	11% 4 2 7% 6% 4 4 4 6% 7% 46%	3339
September	1st to 10th	Night	15% 6% 2 6% 4 3 5% 4 5% 7% 44%	2000
	11th to 20th	Night	16% 6% 2 6% 4 3 4 3 5% 5% 46%	2089
	21st to end	Night	16% 6% 2 6% 4 4 4 3 5% 6% 44%	2252
October	1st to 10th	Night	19% 7% 2 6% 4 3 3 3 5% 7% 40%	2400
	11th to 20th	Night	18% 10% 3 8% 5% 4 4 2 5% 7% 35%	2400
	21st to end	Night	23% 12% 3 7% 4 3 5% 3 4 5% 30%	2680
November	1st to 10th	Night	20% 14% 4 7% 5% 4 4 3 5% 6% 30%	2873
	11th to 20th	Night	22% 14% 4 9% 6% 4 4 3 4 6% 25%	2940
	21st to end	Night	23% 15% 4 10% 5% 4 4 3 4 5% 23%	2940
December	1st to 10th	Night	16% 12% 6% 11% 5% 4 4 3 5% 5% 30%	4720
	11th to 20th	Night	19% 15% 4 10% 6% 3 3 2 3 4 31%	5551
	21st to end	Night	21% 14% 5% 15% 5% 4 4 3 4 5% 21%	7667

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	64% 8% 11% 11% 6%	4094
	11th to 20th	Day	62% 5% 10% 13% 9% 1	4306
	21st to end	Day	42% 6% 12% 23% 16% 1	5781
February	1st to 10th	Day	52% 6% 13% 16% 12% 1	1890
	11th to 20th	Day	55% 6% 10% 19% 9% 1	1851
	21st to end	Day	47% 5% 14% 19% 12% 3	1557
March	1st to 10th	Day	58% 6% 10% 16% 9% 1	5018
	11th to 20th	Day	55% 9% 16% 13% 6% 1	5090
	21st to end	Day	60% 5% 7% 18% 8% 2	5587
April	1st to 10th	Day	53% 6% 9% 17% 12% 3	2506
	11th to 20th	Day	49% 6% 11% 20% 12% 1	2586
	21st to end	Day	51% 7% 12% 16% 12% 3	2600
May	1st to 10th	Day	56% 8% 10% 16% 9%	6143
	11th to 20th	Day	48% 7% 15% 24% 6%	6322
	21st to end	Day	45% 11% 13% 20% 10%	6948
June	1st to 10th	Day	52% 9% 13% 19% 7%	2970
	11th to 20th	Day	44% 9% 14% 23% 10% 1	3000
	21st to end	Day	51% 9% 13% 17% 9% 1	3000
July	1st to 10th	Day	46% 8% 19% 19% 8%	6745
	11th to 20th	Day	38% 7% 17% 29% 8% 1	6652
	21st to end	Day	37% 8% 19% 28% 7%	6671
August	1st to 10th	Day	47% 7% 14% 25% 7%	4222
	11th to 20th	Day	38% 10% 15% 25% 11% 1	4214
	21st to end	Day	33% 7% 17% 27% 15% 1	4558
September	1st to 10th	Day	36% 8% 18% 26% 12%	2400
	11th to 20th	Day	42% 6% 13% 25% 13% 1	2309
	21st to end	Day	40% 7% 12% 26% 14% 1	2147
October	1st to 10th	Day	42% 7% 15% 27% 8%	3260
	11th to 20th	Day	50% 6% 12% 25% 8%	3240
	21st to end	Day	43% 8% 17% 20% 11%	3461
November	1st to 10th	Day	55% 7% 11% 19% 7% 1	1645
	11th to 20th	Day	60% 7% 14% 12% 7%	1680
	21st to end	Day	63% 7% 15% 11% 4	1680
December	1st to 10th	Day	62% 8% 10% 17% 3	2690
	11th to 20th	Day	61% 4 10% 14% 9% 1	2871
	21st to end	Day	63% 7% 13% 12% 4 1	3553
January	1st to 10th	Night	60% 8% 11% 17% 4	8831
	11th to 20th	Night	61% 6% 11% 15% 7%	8649
	21st to end	Night	44% 5% 11% 21% 17% 2	8400
February	1st to 10th	Night	55% 6% 10% 16% 12% 2	2730
	11th to 20th	Night	58% 5% 10% 16% 10% 1	2666
	21st to end	Night	50% 5% 9% 22% 11% 3	2249
March	1st to 10th	Night	62% 6% 7% 13% 11% 1	5052
	11th to 20th	Night	60% 6% 11% 14% 8% 1	5090
	21st to end	Night	62% 4 6% 15% 11% 1	5587
April	1st to 10th	Night	60% 5% 8% 13% 11% 2	2113
	11th to 20th	Night	54% 6% 9% 19% 11% 1	1895
	21st to end	Night	56% 6% 9% 14% 14% 1	1800
May	1st to 10th	Night	59% 7% 9% 14% 10% 1	3823
	11th to 20th	Night	47% 7% 14% 22% 8% 1	3597
	21st to end	Night	46% 10% 16% 21% 7%	3949
June	1st to 10th	Night	53% 8% 14% 16% 9%	1446
	11th to 20th	Night	46% 8% 12% 23% 10% 1	1400
	21st to end	Night	55% 7% 12% 16% 9% 1	1400
July	1st to 10th	Night	51% 7% 15% 18% 9%	3125
	11th to 20th	Night	42% 8% 18% 25% 7%	3159
	21st to end	Night	39% 9% 20% 23% 9%	3873
August	1st to 10th	Night	53% 8% 14% 20% 6%	2903
	11th to 20th	Night	40% 9% 19% 21% 10%	2899
	21st to end	Night	36% 7% 16% 26% 14% 1	3338
September	1st to 10th	Night	38% 8% 12% 30% 13%	2000
	11th to 20th	Night	40% 5% 14% 28% 12% 1	2089
	21st to end	Night	40% 6% 12% 28% 13% 1	2252
October	1st to 10th	Night	47% 6% 13% 26% 8%	3920
	11th to 20th	Night	44% 7% 12% 26% 9%	3899
	21st to end	Night	49% 6% 14% 20% 11%	4328
November	1st to 10th	Night	56% 7% 13% 17% 7% 1	2873
	11th to 20th	Night	58% 7% 11% 16% 7% 1	2940
	21st to end	Night	62% 7% 12% 14% 5%	2940
December	1st to 10th	Night	54% 6% 12% 21% 7%	4720
	11th to 20th	Night	58% 5% 9% 17% 9% 1	5553
	21st to end	Night	64% 6% 12% 13% 5%	7667

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	24% 20% 27% 23% 6%	220
	11th to 20th	Day	23% 12% 40% 17% 7% 1	286
	21st to end	Day	15% 7% 39% 29% 10%	473
February	1st to 10th	Day	21% 10% 34% 26% 7% 2	430
	11th to 20th	Day	20% 9% 38% 26% 6% 1	426
	21st to end	Day	16% 9% 30% 32% 13% 1	355
March	1st to 10th	Day	19% 10% 36% 26% 7% 1	535
	11th to 20th	Day	17% 12% 31% 30% 9% 1	540
	21st to end	Day	25% 11% 30% 26% 7% 2	594
April	1st to 10th	Day	25% 11% 32% 25% 7%	540
	11th to 20th	Day	22% 9% 29% 29% 9% 1	516
	21st to end	Day	25% 9% 24% 29% 12% 2	500
May	1st to 10th	Day	27% 6% 26% 26% 12% 1	606
	11th to 20th	Day	21% 6% 23% 31% 18% 2	724
	21st to end	Day	21% 6% 25% 34% 11% 2	790
June	1st to 10th	Day	26% 7% 20% 32% 13% 2	730
	11th to 20th	Day	19% 5% 20% 37% 17% 3	730
	21st to end	Day	24% 5% 18% 32% 19% 3	730
July	1st to 10th	Day	15% 3 18% 38% 22% 3	720
	11th to 20th	Day	14% 4 17% 36% 25% 4	718
	21st to end	Day	13% 3 15% 42% 23% 3	772
August	1st to 10th	Day	11% 5% 12% 41% 25% 6%	526
	11th to 20th	Day	15% 4 15% 30% 29% 8%	519
	21st to end	Day	14% 5% 18% 34% 22% 6%	583
September	1st to 10th	Day	12% 5% 24% 36% 20% 3	530
	11th to 20th	Day	18% 9% 21% 28% 18% 6%	530
	21st to end	Day	18% 5% 28% 28% 16% 5%	500
October	1st to 10th	Day	20% 10% 20% 30% 17% 3	420
	11th to 20th	Day	23% 9% 26% 27% 14% 1	420
	21st to end	Day	23% 10% 35% 23% 8% 1	462
November	1st to 10th	Day	23% 13% 33% 23% 6% 1	425
	11th to 20th	Day	27% 15% 33% 18% 5% 1	430
	21st to end	Day	29% 12% 34% 21% 3 1	430
December	1st to 10th	Day	26% 14% 34% 21% 4	430
	11th to 20th	Day	24% 25% 31% 16% 3	335
	21st to end	Day	15% 18% 36% 24% 6%	242
January	1st to 10th	Night	23% 11% 36% 23% 6%	950
	11th to 20th	Night	23% 11% 35% 24% 7%	947
	21st to end	Night	18% 9% 38% 26% 8% 1	924
February	1st to 10th	Night	23% 8% 36% 24% 8% 1	840
	11th to 20th	Night	24% 8% 35% 27% 4 1	823
	21st to end	Night	19% 8% 32% 32% 9%	692
March	1st to 10th	Night	23% 9% 33% 31% 5%	840
	11th to 20th	Night	24% 7% 32% 27% 8% 1	840
	21st to end	Night	26% 10% 29% 26% 8% 1	924
April	1st to 10th	Night	27% 10% 28% 29% 5%	643
	11th to 20th	Night	27% 6% 29% 29% 10%	613
	21st to end	Night	27% 7% 27% 28% 9% 1	600
May	1st to 10th	Night	28% 5% 26% 29% 10% 2	600
	11th to 20th	Night	23% 5% 25% 29% 16% 2	592
	21st to end	Night	17% 7% 30% 37% 9% 1	649
June	1st to 10th	Night	26% 4 22% 36% 11%	446
	11th to 20th	Night	20% 4 21% 38% 15% 2	400
	21st to end	Night	24% 2 19% 40% 13% 2	400
July	1st to 10th	Night	16% 3 21% 40% 19% 1	390
	11th to 20th	Night	15% 2 21% 43% 18% 1	403
	21st to end	Night	17% 3 20% 44% 16% 1	656
August	1st to 10th	Night	16% 2 20% 42% 19% 1	598
	11th to 20th	Night	16% 2 18% 38% 23% 2	592
	21st to end	Night	14% 3 23% 36% 22% 2	660
September	1st to 10th	Night	18% 5% 27% 36% 15% 1	600
	11th to 20th	Night	16% 8% 22% 34% 18% 1	689
	21st to end	Night	18% 7% 28% 35% 12% 1	800
October	1st to 10th	Night	22% 6% 28% 30% 13% 1	800
	11th to 20th	Night	22% 10% 31% 25% 10% 1	800
	21st to end	Night	28% 14% 31% 23% 5%	886
November	1st to 10th	Night	26% 14% 34% 21% 5%	930
	11th to 20th	Night	27% 15% 31% 20% 6% 1	950
	21st to end	Night	30% 15% 30% 21% 4 1	950
December	1st to 10th	Night	27% 14% 37% 19% 4	950
	11th to 20th	Night	26% 20% 36% 15% 4	950
	21st to end	Night	26% 14% 34% 20% 5% 1	1045

Page generated at 2026-04-14 03:44:30. Version ac07

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