Montauk Point State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Montauk Point State Park clear sky chart from 2005-11-06 to 2026-10-29.

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	16% 8% 2 6% 4 4 4 3 5% 7% 42%	149014
	Night	17% 8% 3 6% 4 4 4 3 5% 6% 39%	143040
Transparency	Day	41% 7% 13% 22% 15% 2	152562
	Night	44% 6% 12% 21% 15% 2	147581
Seeing	Day	18% 7% 24% 30% 17% 4	17727
	Night	20% 10% 27% 27% 14% 2	26634

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% 8% 2 6% 4 4 4 3 5% 6% 45%	4661
	11th to 20th	Day	17% 7% 2 6% 3 4 3 3 4 5% 46%	4650
	21st to end	Day	16% 9% 3 5% 3 4 4 3 4 5% 44%	5124
February	1st to 10th	Day	17% 8% 3 6% 6% 4 5% 5% 5% 7% 36%	2056
	11th to 20th	Day	14% 8% 3 7% 3 4 4 3 5% 6% 42%	2048
	21st to end	Day	19% 8% 3 6% 3 3 4 3 5% 7% 39%	1730
March	1st to 10th	Day	20% 8% 2 4 3 3 3 2 4 6% 45%	4576
	11th to 20th	Day	13% 10% 2 4 3 3 3 3 5% 7% 46%	4826
	21st to end	Day	21% 10% 2 5% 4 3 4 3 4 5% 38%	5977
April	1st to 10th	Day	19% 8% 2 5% 3 3 4 3 5% 6% 42%	2520
	11th to 20th	Day	17% 7% 2 5% 2 3 4 3 5% 7% 44%	2494
	21st to end	Day	18% 6% 2 5% 4 3 4 4 5% 7% 42%	2686
May	1st to 10th	Day	25% 10% 3 6% 3 3 3 3 4 7% 32%	7639
	11th to 20th	Day	18% 9% 3 6% 4 3 3 2 4 6% 42%	7659
	21st to end	Day	21% 9% 3 7% 3 3 4 3 5% 7% 33%	9060
June	1st to 10th	Day	16% 6% 1 5% 4 4 4 4 6% 8% 41%	2940
	11th to 20th	Day	13% 7% 2 7% 3 4 5% 4 6% 9% 41%	2940
	21st to end	Day	12% 7% 2 5% 3 3 5% 4 7% 9% 44%	2940
July	1st to 10th	Day	16% 8% 2 6% 4 4 4 4 6% 9% 38%	8280
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 6% 10% 42%	8280
	21st to end	Day	16% 6% 2 5% 4 3 4 3 5% 7% 46%	8993
August	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 6% 10% 37%	6041
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 5% 8% 49%	5673
	21st to end	Day	10% 4 2 5% 4 4 5% 4 6% 8% 49%	6080
September	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 5% 7% 47%	2520
	11th to 20th	Day	11% 6% 2 5% 3 3 3 2 4 7% 54%	2321
	21st to end	Day	20% 7% 2 5% 4 4 4 3 5% 7% 39%	2310
October	1st to 10th	Day	19% 6% 2 5% 3 3 3 3 4 6% 47%	2310
	11th to 20th	Day	15% 7% 2 5% 3 2 3 2 5% 8% 48%	2085
	21st to end	Day	17% 6% 2 6% 4 4 3 4 5% 6% 43%	2052
November	1st to 10th	Day	16% 6% 2 4 4 4 4 3 4 5% 48%	1851
	11th to 20th	Day	16% 6% 2 4 4 3 4 3 6% 6% 46%	1890
	21st to end	Day	17% 8% 3 5% 4 4 3 3 5% 6% 41%	1890
December	1st to 10th	Day	14% 9% 3 7% 4 4 3 3 4 5% 44%	2798
	11th to 20th	Day	20% 9% 2 5% 3 3 2 2 3 5% 45%	3066
	21st to end	Day	20% 11% 4 9% 4 3 3 2 3 5% 36%	4048
January	1st to 10th	Night	15% 8% 3 6% 4 3 3 2 4 5% 46%	8234
	11th to 20th	Night	17% 9% 3 8% 4 4 4 3 4 4 40%	8235
	21st to end	Night	17% 9% 3 8% 5% 4 5% 4 5% 6% 35%	9039
February	1st to 10th	Night	15% 10% 3 7% 5% 4 4 3 5% 6% 37%	2562
	11th to 20th	Night	19% 8% 2 6% 3 4 3 4 6% 7% 38%	2458
	21st to end	Night	19% 8% 3 7% 5% 4 4 3 4 5% 37%	2076
March	1st to 10th	Night	22% 9% 2 5% 3 3 4 3 5% 5% 40%	5484
	11th to 20th	Night	16% 10% 3 6% 4 3 4 3 5% 5% 40%	5353
	21st to end	Night	21% 9% 2 5% 4 4 4 3 5% 5% 35%	5181
April	1st to 10th	Night	20% 8% 3 6% 3 3 4 3 5% 6% 39%	2100
	11th to 20th	Night	17% 7% 2 7% 3 4 4 4 5% 6% 42%	2075
	21st to end	Night	19% 8% 3 5% 4 4 4 3 4 6% 39%	1932
May	1st to 10th	Night	23% 11% 3 7% 4 3 3 3 4 6% 32%	5259
	11th to 20th	Night	21% 10% 3 6% 3 3 4 3 6% 7% 34%	5235
	21st to end	Night	23% 10% 4 8% 5% 4 5% 3 5% 6% 28%	5122
June	1st to 10th	Night	16% 9% 3 5% 5% 4 5% 3 5% 6% 39%	1680
	11th to 20th	Night	18% 6% 2 5% 4 4 4 3 6% 8% 39%	1680
	21st to end	Night	13% 8% 2 6% 5% 4 5% 3 6% 9% 39%	1680
July	1st to 10th	Night	19% 11% 3 7% 4 4 4 4 6% 8% 31%	4680
	11th to 20th	Night	14% 8% 3 6% 4 5% 4 4 7% 8% 37%	4680
	21st to end	Night	14% 7% 2 6% 4 4 5% 3 5% 8% 41%	5084
August	1st to 10th	Night	17% 7% 3 7% 4 5% 6% 5% 7% 8% 32%	4060
	11th to 20th	Night	10% 6% 2 6% 4 5% 6% 5% 7% 8% 42%	4369
	21st to end	Night	11% 4 1 5% 4 4 4 4 6% 8% 49%	5045
September	1st to 10th	Night	14% 7% 2 6% 3 5% 5% 4 6% 7% 40%	2100
	11th to 20th	Night	13% 5% 2 6% 3 3 3 3 4 6% 51%	2298
	21st to end	Night	20% 7% 2 7% 5% 5% 4 3 4 5% 38%	2310
October	1st to 10th	Night	19% 6% 2 6% 4 3 4 3 4 6% 43%	2310
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 5% 6% 47%	2531
	21st to end	Night	19% 7% 3 6% 4 4 4 3 4 6% 41%	2965
November	1st to 10th	Night	15% 7% 2 6% 4 4 4 2 4 7% 46%	2667
	11th to 20th	Night	17% 8% 2 5% 3 4 4 3 5% 6% 42%	2730
	21st to end	Night	15% 7% 2 5% 4 4 4 4 5% 7% 43%	2730
December	1st to 10th	Night	16% 10% 4 6% 5% 4 4 3 4 5% 39%	4598
	11th to 20th	Night	24% 9% 2 6% 3 3 3 2 4 5% 40%	5348
	21st to end	Night	19% 9% 3 7% 4 3 3 3 4 5% 40%	7150

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	39% 5% 12% 25% 17% 1	4662
	11th to 20th	Day	41% 5% 10% 20% 18% 6%	4680
	21st to end	Day	42% 5% 11% 24% 17% 1	5124
February	1st to 10th	Day	47% 6% 14% 19% 13% 1	2056
	11th to 20th	Day	42% 6% 11% 24% 14% 2	2057
	21st to end	Day	45% 4 13% 20% 15% 3	1730
March	1st to 10th	Day	42% 5% 12% 17% 14% 9%	4579
	11th to 20th	Day	37% 5% 16% 29% 13% 1	4826
	21st to end	Day	48% 5% 9% 16% 18% 5%	5977
April	1st to 10th	Day	42% 6% 12% 19% 18% 3	2520
	11th to 20th	Day	39% 5% 12% 22% 19% 3	2494
	21st to end	Day	41% 6% 10% 21% 18% 3	2686
May	1st to 10th	Day	52% 7% 14% 16% 10% 1	7651
	11th to 20th	Day	45% 6% 13% 23% 13% 1	7663
	21st to end	Day	48% 8% 12% 19% 11% 1	9061
June	1st to 10th	Day	40% 9% 11% 23% 16% 1	2940
	11th to 20th	Day	39% 8% 14% 24% 14% 1	2940
	21st to end	Day	36% 9% 14% 24% 15% 1	2940
July	1st to 10th	Day	43% 10% 15% 19% 12% 1	8210
	11th to 20th	Day	37% 8% 15% 28% 12% 1	8205
	21st to end	Day	38% 7% 12% 23% 19% 1	8795
August	1st to 10th	Day	42% 9% 20% 19% 9%	6027
	11th to 20th	Day	33% 7% 18% 33% 8% 1	5712
	21st to end	Day	32% 8% 16% 28% 16% 1	6080
September	1st to 10th	Day	37% 7% 13% 24% 19% 1	2520
	11th to 20th	Day	31% 6% 13% 24% 23% 3	2321
	21st to end	Day	45% 7% 10% 20% 17% 1	2310
October	1st to 10th	Day	34% 5% 11% 24% 21% 5%	3700
	11th to 20th	Day	29% 5% 11% 25% 28% 3	3301
	21st to end	Day	31% 5% 16% 28% 18% 2	3252
November	1st to 10th	Day	39% 4 15% 20% 19% 2	1851
	11th to 20th	Day	37% 6% 15% 21% 19% 2	1890
	21st to end	Day	44% 6% 13% 26% 10% 2	1890
December	1st to 10th	Day	42% 5% 16% 25% 11% 1	2798
	11th to 20th	Day	44% 4 13% 18% 18% 4	3066
	21st to end	Day	50% 6% 9% 19% 14% 2	4048
January	1st to 10th	Night	40% 4 12% 27% 16% 2	8234
	11th to 20th	Night	46% 4 11% 20% 15% 4	8280
	21st to end	Night	48% 6% 11% 19% 14% 2	9039
February	1st to 10th	Night	48% 6% 12% 21% 12% 2	2562
	11th to 20th	Night	45% 5% 11% 22% 14% 3	2460
	21st to end	Night	48% 5% 8% 22% 14% 3	2076
March	1st to 10th	Night	46% 5% 11% 18% 14% 7%	5494
	11th to 20th	Night	45% 6% 14% 22% 11% 3	5354
	21st to end	Night	49% 5% 7% 12% 22% 5%	5181
April	1st to 10th	Night	46% 5% 11% 18% 17% 4	2100
	11th to 20th	Night	43% 6% 12% 18% 20% 2	2075
	21st to end	Night	45% 6% 10% 18% 17% 4	1932
May	1st to 10th	Night	52% 6% 14% 15% 11% 1	5265
	11th to 20th	Night	48% 7% 14% 20% 9% 3	5236
	21st to end	Night	54% 8% 10% 18% 9% 1	5123
June	1st to 10th	Night	45% 7% 12% 19% 17% 1	1680
	11th to 20th	Night	42% 7% 13% 23% 14% 1	1680
	21st to end	Night	41% 7% 13% 24% 14% 1	1680
July	1st to 10th	Night	51% 7% 11% 19% 12% 1	4640
	11th to 20th	Night	42% 9% 14% 25% 10% 1	4632
	21st to end	Night	39% 7% 15% 22% 15% 1	4967
August	1st to 10th	Night	47% 9% 19% 15% 9% 1	4050
	11th to 20th	Night	36% 9% 20% 29% 7%	4396
	21st to end	Night	32% 7% 16% 30% 15% 1	5045
September	1st to 10th	Night	42% 6% 10% 24% 16% 2	2100
	11th to 20th	Night	35% 5% 12% 23% 23% 3	2298
	21st to end	Night	49% 6% 8% 18% 17% 3	2310
October	1st to 10th	Night	38% 6% 11% 26% 17% 3	3700
	11th to 20th	Night	27% 5% 10% 24% 30% 4	4054
	21st to end	Night	33% 5% 14% 25% 22% 2	4715
November	1st to 10th	Night	40% 6% 12% 22% 18% 3	2667
	11th to 20th	Night	43% 5% 11% 20% 17% 3	2730
	21st to end	Night	40% 7% 14% 27% 11% 2	2730
December	1st to 10th	Night	45% 8% 13% 22% 10% 1	4598
	11th to 20th	Night	49% 4 11% 19% 15% 2	5348
	21st to end	Night	46% 5% 11% 19% 17% 2	7150

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	18% 20% 32% 22% 6% 1	220
	11th to 20th	Day	17% 20% 42% 17% 4	220
	21st to end	Day	19% 13% 41% 19% 6% 2	242
February	1st to 10th	Day	23% 9% 39% 23% 6%	496
	11th to 20th	Day	21% 14% 41% 23% 2	536
	21st to end	Day	22% 13% 34% 25% 5% 1	446
March	1st to 10th	Day	20% 11% 36% 26% 7%	540
	11th to 20th	Day	15% 13% 36% 29% 6% 1	540
	21st to end	Day	22% 9% 35% 26% 7% 1	594
April	1st to 10th	Day	24% 8% 31% 26% 10% 1	540
	11th to 20th	Day	19% 8% 28% 35% 9% 1	532
	21st to end	Day	22% 6% 22% 39% 10% 2	540
May	1st to 10th	Day	23% 8% 26% 31% 10% 1	543
	11th to 20th	Day	18% 3 26% 36% 15% 2	567
	21st to end	Day	21% 4 15% 31% 24% 5%	617
June	1st to 10th	Day	16% 2 18% 35% 25% 3	570
	11th to 20th	Day	14% 3 19% 37% 24% 3	570
	21st to end	Day	14% 2 15% 37% 27% 4	570
July	1st to 10th	Day	15% 4 8% 35% 33% 6%	565
	11th to 20th	Day	10% 3 10% 36% 33% 9%	564
	21st to end	Day	14% 3 12% 37% 30% 4	620
August	1st to 10th	Day	12% 2 12% 34% 33% 8%	566
	11th to 20th	Day	14% 2 9% 34% 33% 8%	559
	21st to end	Day	11% 2 13% 37% 28% 10%	627
September	1st to 10th	Day	17% 3 16% 32% 24% 9%	570
	11th to 20th	Day	15% 2 17% 30% 26% 10%	570
	21st to end	Day	24% 4 18% 32% 18% 3	570
October	1st to 10th	Day	22% 6% 19% 28% 18% 8%	570
	11th to 20th	Day	17% 8% 24% 32% 16% 3	531
	21st to end	Day	23% 8% 26% 27% 13% 3	486
November	1st to 10th	Day	15% 10% 26% 32% 13% 4	425
	11th to 20th	Day	20% 14% 31% 26% 8%	430
	21st to end	Day	19% 16% 33% 23% 9% 1	430
December	1st to 10th	Day	17% 15% 34% 26% 7%	299
	11th to 20th	Day	23% 16% 37% 19% 5%	220
	21st to end	Day	23% 15% 31% 21% 8% 2	242
January	1st to 10th	Night	20% 18% 37% 20% 4	840
	11th to 20th	Night	27% 18% 33% 19% 4	840
	21st to end	Night	21% 17% 40% 19% 3 1	924
February	1st to 10th	Night	20% 15% 41% 22% 2	840
	11th to 20th	Night	23% 16% 41% 17% 3	823
	21st to end	Night	23% 15% 36% 21% 5%	692
March	1st to 10th	Night	23% 13% 34% 24% 7%	840
	11th to 20th	Night	20% 10% 35% 28% 6% 2	840
	21st to end	Night	23% 9% 35% 25% 8% 1	924
April	1st to 10th	Night	24% 8% 31% 29% 7% 1	840
	11th to 20th	Night	19% 7% 29% 33% 11%	831
	21st to end	Night	22% 4 26% 32% 13% 1	672
May	1st to 10th	Night	22% 7% 22% 33% 13% 3	630
	11th to 20th	Night	20% 5% 28% 35% 11% 1	622
	21st to end	Night	24% 2 14% 32% 25% 3	463
June	1st to 10th	Night	17% 4 17% 36% 24% 2	420
	11th to 20th	Night	20% 3 16% 33% 26% 1	420
	21st to end	Night	17% 2 11% 39% 29% 2	420
July	1st to 10th	Night	16% 4 10% 37% 29% 4	410
	11th to 20th	Night	13% 2 10% 38% 31% 6%	408
	21st to end	Night	13% 3 12% 38% 30% 3	460
August	1st to 10th	Night	11% 2 12% 38% 32% 5%	591
	11th to 20th	Night	12% 3 10% 35% 33% 7%	743
	21st to end	Night	14% 3 12% 34% 30% 8%	924
September	1st to 10th	Night	16% 2 16% 33% 27% 6%	840
	11th to 20th	Night	15% 3 17% 30% 26% 8%	840
	21st to end	Night	23% 5% 20% 30% 19% 4	840
October	1st to 10th	Night	23% 6% 22% 25% 19% 5%	840
	11th to 20th	Night	19% 9% 27% 29% 14% 2	840
	21st to end	Night	21% 10% 32% 25% 10% 2	913
November	1st to 10th	Night	17% 11% 29% 28% 12% 2	820
	11th to 20th	Night	22% 16% 31% 22% 8% 1	840
	21st to end	Night	18% 17% 31% 25% 8% 1	840
December	1st to 10th	Night	24% 17% 32% 20% 6% 1	840
	11th to 20th	Night	23% 20% 33% 18% 5%	840
	21st to end	Night	23% 16% 37% 20% 4	924

Page generated at 2026-10-26 04:37:48. Version ac07

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