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 2025-06-10.

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% 8% 2 6% 4 4 4 3 5% 7% 41%	119091
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	119116
Transparency	Day	41% 7% 13% 22% 15% 2	122682
	Night	44% 6% 12% 20% 15% 2	123686
Seeing	Day	18% 7% 24% 30% 17% 4	15880
	Night	20% 10% 27% 27% 13% 2	24919

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% 7% 2 5% 4 4 4 3 5% 6% 48%	3597
	11th to 20th	Day	16% 8% 2 5% 3 4 3 3 5% 5% 46%	3570
	21st to end	Day	19% 9% 4 6% 4 4 4 3 4 4 40%	3960
February	1st to 10th	Day	18% 9% 3 6% 5% 4 5% 5% 5% 7% 35%	1958
	11th to 20th	Day	14% 8% 3 7% 3 4 4 3 5% 6% 41%	1948
	21st to end	Day	19% 8% 3 6% 3 3 4 2 5% 7% 39%	1650
March	1st to 10th	Day	20% 8% 2 4 3 3 3 2 4 6% 45%	4476
	11th to 20th	Day	13% 10% 2 4 3 3 3 3 5% 7% 47%	4722
	21st to end	Day	21% 10% 2 5% 4 3 4 3 4 5% 38%	5848
April	1st to 10th	Day	19% 8% 2 5% 4 3 4 3 5% 6% 41%	2400
	11th to 20th	Day	18% 7% 2 5% 3 3 3 3 5% 7% 44%	2374
	21st to end	Day	18% 6% 2 5% 4 3 4 4 6% 7% 41%	2558
May	1st to 10th	Day	26% 11% 3 6% 3 3 3 3 5% 8% 28%	5886
	11th to 20th	Day	20% 9% 3 6% 4 3 3 2 4 6% 39%	5895
	21st to end	Day	19% 9% 3 7% 3 3 4 3 5% 8% 37%	6949
June	1st to 10th	Day	17% 6% 1 6% 4 4 5% 4 6% 8% 39%	2786
	11th to 20th	Day	13% 7% 2 7% 3 4 5% 4 6% 9% 41%	2660
	21st to end	Day	12% 7% 2 5% 3 3 5% 4 7% 9% 43%	2660
July	1st to 10th	Day	14% 9% 3 7% 4 4 4 4 6% 8% 36%	4440
	11th to 20th	Day	12% 6% 2 5% 5% 4 5% 4 6% 10% 42%	4440
	21st to end	Day	18% 7% 2 6% 4 4 4 4 6% 8% 36%	4814
August	1st to 10th	Day	17% 7% 2 6% 5% 4 5% 3 6% 8% 37%	4117
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 3 5% 8% 47%	3855
	21st to end	Day	7% 3 2 5% 4 4 5% 4 5% 8% 53%	4180
September	1st to 10th	Day	13% 6% 2 5% 4 4 3 3 5% 7% 47%	2280
	11th to 20th	Day	11% 6% 1 5% 3 3 3 3 4 7% 54%	2100
	21st to end	Day	19% 7% 2 5% 4 4 4 3 5% 7% 40%	2090
October	1st to 10th	Day	20% 6% 2 6% 3 3 3 3 5% 6% 44%	2090
	11th to 20th	Day	14% 7% 2 5% 3 2 3 3 5% 7% 49%	1886
	21st to end	Day	18% 6% 2 6% 4 4 3 4 5% 6% 42%	1881
November	1st to 10th	Day	17% 6% 2 4 4 4 4 3 4 5% 48%	1761
	11th to 20th	Day	16% 6% 2 4 4 3 3 4 6% 6% 46%	1800
	21st to end	Day	17% 8% 3 5% 4 4 3 3 5% 6% 41%	1800
December	1st to 10th	Day	14% 9% 3 7% 4 4 3 3 4 5% 44%	2714
	11th to 20th	Day	20% 9% 3 5% 3 3 2 2 3 5% 45%	2986
	21st to end	Day	20% 11% 4 9% 4 3 3 2 3 5% 36%	3960
January	1st to 10th	Night	15% 6% 3 5% 4 3 3 3 5% 6% 48%	6349
	11th to 20th	Night	16% 10% 3 7% 4 4 4 3 4 4 42%	6315
	21st to end	Night	19% 10% 3 8% 4 4 4 4 5% 6% 33%	6978
February	1st to 10th	Night	16% 10% 3 7% 5% 4 4 3 5% 6% 36%	2440
	11th to 20th	Night	20% 8% 2 6% 4 4 4 4 6% 7% 38%	2338
	21st to end	Night	19% 8% 3 7% 5% 4 4 4 4 5% 37%	1980
March	1st to 10th	Night	22% 9% 2 5% 3 3 4 3 5% 5% 40%	5364
	11th to 20th	Night	16% 10% 3 6% 4 3 4 3 5% 5% 40%	5237
	21st to end	Night	21% 9% 2 5% 4 4 4 3 5% 5% 36%	5068
April	1st to 10th	Night	20% 9% 3 6% 3 3 4 3 5% 7% 38%	2000
	11th to 20th	Night	18% 7% 2 7% 3 4 3 4 4 6% 42%	1975
	21st to end	Night	19% 8% 3 5% 4 4 4 3 5% 6% 39%	1840
May	1st to 10th	Night	25% 12% 4 7% 4 3 3 3 4 7% 27%	4054
	11th to 20th	Night	24% 10% 3 6% 4 3 4 3 6% 7% 30%	4033
	21st to end	Night	21% 10% 4 8% 4 4 5% 3 5% 6% 30%	3934
June	1st to 10th	Night	16% 9% 3 5% 5% 4 5% 4 5% 6% 37%	1598
	11th to 20th	Night	18% 6% 2 5% 4 3 3 3 6% 8% 41%	1520
	21st to end	Night	13% 8% 2 6% 5% 4 5% 3 6% 9% 39%	1520
July	1st to 10th	Night	17% 12% 3 6% 4 4 4 4 6% 7% 30%	2520
	11th to 20th	Night	12% 7% 3 6% 4 6% 5% 5% 8% 10% 35%	2520
	21st to end	Night	20% 9% 2 6% 5% 4 5% 3 5% 7% 33%	2739
August	1st to 10th	Night	20% 8% 3 8% 4 5% 5% 5% 7% 6% 30%	2780
	11th to 20th	Night	9% 5% 2 6% 4 5% 6% 5% 8% 8% 42%	2969
	21st to end	Night	8% 4 1 5% 3 4 4 3 5% 8% 55%	3476
September	1st to 10th	Night	14% 7% 2 6% 3 5% 5% 4 6% 6% 41%	1900
	11th to 20th	Night	13% 6% 2 6% 3 3 3 3 4 7% 51%	2079
	21st to end	Night	18% 7% 2 7% 5% 5% 4 3 4 5% 39%	2090
October	1st to 10th	Night	20% 7% 2 6% 4 3 4 3 4 6% 40%	2090
	11th to 20th	Night	15% 6% 2 6% 3 3 4 3 5% 6% 47%	2290
	21st to end	Night	20% 7% 3 6% 4 4 4 3 4 6% 39%	2717
November	1st to 10th	Night	15% 7% 2 6% 4 4 4 2 4 7% 45%	2537
	11th to 20th	Night	18% 8% 3 5% 3 4 4 3 4 6% 42%	2600
	21st to end	Night	15% 7% 2 5% 4 4 4 4 5% 7% 42%	2600
December	1st to 10th	Night	16% 10% 4 6% 4 4 4 3 4 5% 39%	4462
	11th to 20th	Night	24% 9% 2 6% 3 3 3 2 4 4 39%	5208
	21st to end	Night	19% 9% 2 7% 4 3 3 3 4 5% 40%	6996

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	36% 5% 9% 28% 20% 2	3598
	11th to 20th	Day	40% 6% 11% 20% 17% 7%	3600
	21st to end	Day	48% 5% 10% 21% 15% 1	3960
February	1st to 10th	Day	47% 6% 15% 19% 12% 1	1958
	11th to 20th	Day	43% 6% 11% 24% 14% 3	1957
	21st to end	Day	45% 4 13% 19% 15% 3	1650
March	1st to 10th	Day	41% 5% 12% 17% 14% 10%	4479
	11th to 20th	Day	37% 5% 16% 29% 13% 1	4722
	21st to end	Day	48% 5% 9% 16% 18% 5%	5848
April	1st to 10th	Day	42% 6% 12% 19% 17% 3	2400
	11th to 20th	Day	40% 5% 11% 22% 19% 3	2374
	21st to end	Day	41% 6% 10% 21% 18% 4	2558
May	1st to 10th	Day	55% 8% 16% 13% 8% 1	5897
	11th to 20th	Day	48% 6% 13% 19% 13% 1	5899
	21st to end	Day	45% 9% 12% 21% 12% 1	6949
June	1st to 10th	Day	41% 9% 11% 23% 15% 1	2786
	11th to 20th	Day	38% 8% 15% 24% 14% 1	2660
	21st to end	Day	36% 9% 14% 25% 15% 1	2660
July	1st to 10th	Day	44% 11% 12% 17% 14% 1	4370
	11th to 20th	Day	37% 9% 17% 24% 12% 1	4365
	21st to end	Day	45% 8% 14% 18% 14% 2	4661
August	1st to 10th	Day	45% 8% 17% 21% 9%	4103
	11th to 20th	Day	36% 8% 15% 31% 10% 1	3894
	21st to end	Day	28% 8% 16% 29% 19% 1	4180
September	1st to 10th	Day	36% 7% 13% 23% 20% 1	2280
	11th to 20th	Day	31% 6% 13% 24% 23% 3	2100
	21st to end	Day	44% 7% 9% 21% 18% 1	2090
October	1st to 10th	Day	35% 5% 11% 23% 20% 5%	3480
	11th to 20th	Day	27% 5% 12% 25% 29% 3	3102
	21st to end	Day	31% 5% 17% 28% 17% 2	3081
November	1st to 10th	Day	40% 4 15% 20% 19% 2	1761
	11th to 20th	Day	38% 6% 15% 21% 19% 3	1800
	21st to end	Day	43% 6% 13% 26% 10% 2	1800
December	1st to 10th	Day	42% 5% 16% 25% 11% 1	2714
	11th to 20th	Day	45% 4 13% 17% 17% 4	2986
	21st to end	Day	50% 6% 9% 19% 14% 2	3960
January	1st to 10th	Night	37% 5% 10% 28% 17% 3	6349
	11th to 20th	Night	45% 4 12% 20% 14% 4	6360
	21st to end	Night	50% 6% 12% 18% 13% 2	6978
February	1st to 10th	Night	48% 6% 13% 21% 11% 2	2440
	11th to 20th	Night	46% 5% 11% 21% 14% 3	2340
	21st to end	Night	47% 5% 9% 22% 14% 4	1980
March	1st to 10th	Night	46% 5% 11% 18% 13% 7%	5374
	11th to 20th	Night	45% 6% 14% 22% 11% 3	5238
	21st to end	Night	49% 5% 7% 12% 22% 5%	5068
April	1st to 10th	Night	46% 5% 11% 18% 16% 4	2000
	11th to 20th	Night	43% 6% 11% 18% 20% 2	1975
	21st to end	Night	45% 6% 10% 18% 17% 4	1840
May	1st to 10th	Night	57% 7% 14% 12% 9% 1	4060
	11th to 20th	Night	53% 7% 13% 15% 8% 3	4034
	21st to end	Night	51% 10% 12% 17% 10% 1	3935
June	1st to 10th	Night	45% 8% 12% 18% 16% 1	1598
	11th to 20th	Night	40% 7% 13% 24% 14% 1	1520
	21st to end	Night	41% 8% 13% 25% 14% 1	1520
July	1st to 10th	Night	51% 8% 11% 18% 12% 1	2480
	11th to 20th	Night	39% 10% 18% 23% 9% 1	2472
	21st to end	Night	49% 7% 15% 14% 13% 1	2651
August	1st to 10th	Night	50% 8% 17% 16% 8% 1	2770
	11th to 20th	Night	35% 10% 19% 27% 9%	2996
	21st to end	Night	26% 7% 17% 31% 19% 1	3476
September	1st to 10th	Night	41% 6% 10% 23% 17% 2	1900
	11th to 20th	Night	35% 5% 12% 23% 23% 2	2079
	21st to end	Night	47% 6% 8% 18% 18% 3	2090
October	1st to 10th	Night	39% 6% 11% 26% 16% 3	3480
	11th to 20th	Night	27% 5% 10% 24% 31% 4	3813
	21st to end	Night	33% 5% 14% 25% 22% 2	4467
November	1st to 10th	Night	40% 6% 12% 21% 18% 4	2537
	11th to 20th	Night	44% 5% 11% 20% 17% 3	2600
	21st to end	Night	40% 7% 14% 26% 11% 2	2600
December	1st to 10th	Night	45% 8% 13% 22% 10% 1	4462
	11th to 20th	Night	49% 4 11% 20% 15% 1	5208
	21st to end	Night	46% 5% 11% 19% 17% 2	6996

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	19% 22% 32% 20% 7% 1	200
	11th to 20th	Day	18% 17% 42% 19% 5%	200
	21st to end	Day	19% 13% 39% 20% 7% 2	220
February	1st to 10th	Day	24% 10% 39% 21% 6%	458
	11th to 20th	Day	21% 15% 41% 21% 2	496
	21st to end	Day	22% 14% 34% 24% 6% 1	414
March	1st to 10th	Day	19% 11% 37% 26% 7%	500
	11th to 20th	Day	15% 13% 36% 28% 6% 1	500
	21st to end	Day	22% 9% 34% 25% 8% 1	550
April	1st to 10th	Day	24% 8% 31% 26% 10% 1	500
	11th to 20th	Day	20% 8% 30% 34% 8% 1	492
	21st to end	Day	22% 6% 23% 37% 10% 2	500
May	1st to 10th	Day	23% 9% 26% 31% 10% 1	503
	11th to 20th	Day	18% 3 28% 35% 14% 1	527
	21st to end	Day	20% 3 15% 31% 25% 5%	573
June	1st to 10th	Day	17% 2 18% 36% 24% 3	526
	11th to 20th	Day	13% 2 19% 37% 26% 4	490
	21st to end	Day	14% 2 16% 38% 25% 4	490
July	1st to 10th	Day	15% 4 8% 35% 31% 7%	485
	11th to 20th	Day	10% 3 9% 37% 33% 9%	484
	21st to end	Day	14% 2 11% 39% 30% 3	532
August	1st to 10th	Day	12% 2 12% 36% 31% 7%	486
	11th to 20th	Day	15% 2 9% 34% 32% 8%	479
	21st to end	Day	11% 1 13% 35% 28% 11%	539
September	1st to 10th	Day	17% 2 17% 30% 24% 10%	490
	11th to 20th	Day	15% 3 17% 29% 24% 11%	490
	21st to end	Day	25% 3 19% 33% 17% 3	490
October	1st to 10th	Day	24% 7% 18% 27% 18% 6%	490
	11th to 20th	Day	15% 8% 25% 31% 18% 3	457
	21st to end	Day	24% 7% 26% 28% 12% 3	429
November	1st to 10th	Day	15% 8% 26% 33% 14% 4	395
	11th to 20th	Day	21% 13% 32% 26% 9%	400
	21st to end	Day	19% 16% 33% 22% 9% 1	400
December	1st to 10th	Day	18% 15% 35% 25% 7%	275
	11th to 20th	Day	24% 17% 36% 19% 6%	200
	21st to end	Day	23% 12% 33% 21% 9% 2	220
January	1st to 10th	Night	20% 19% 37% 20% 4	800
	11th to 20th	Night	27% 17% 33% 19% 4	800
	21st to end	Night	21% 15% 40% 20% 3 1	880
February	1st to 10th	Night	21% 15% 40% 22% 2	800
	11th to 20th	Night	24% 16% 42% 15% 3	783
	21st to end	Night	23% 15% 36% 21% 5%	660
March	1st to 10th	Night	22% 13% 35% 23% 6%	800
	11th to 20th	Night	20% 10% 35% 28% 5% 2	800
	21st to end	Night	23% 9% 34% 25% 8% 1	880
April	1st to 10th	Night	24% 8% 31% 30% 7% 1	800
	11th to 20th	Night	20% 7% 29% 32% 11% 1	791
	21st to end	Night	23% 4 27% 31% 13% 1	640
May	1st to 10th	Night	23% 7% 21% 33% 13% 3	600
	11th to 20th	Night	21% 5% 28% 34% 11% 1	592
	21st to end	Night	23% 2 14% 31% 26% 3	441
June	1st to 10th	Night	17% 3 18% 37% 23% 2	400
	11th to 20th	Night	20% 3 15% 32% 28% 1	380
	21st to end	Night	16% 3 12% 40% 28% 1	380
July	1st to 10th	Night	15% 4 10% 38% 29% 4	370
	11th to 20th	Night	13% 2 9% 39% 32% 5%	368
	21st to end	Night	14% 2 13% 39% 30% 3	416
August	1st to 10th	Night	10% 1 13% 39% 32% 5%	535
	11th to 20th	Night	12% 3 10% 35% 32% 7%	671
	21st to end	Night	13% 2 11% 33% 31% 9%	836
September	1st to 10th	Night	17% 1 16% 32% 27% 7%	760
	11th to 20th	Night	16% 3 17% 30% 25% 9%	760
	21st to end	Night	21% 4 21% 31% 19% 4	760
October	1st to 10th	Night	25% 6% 21% 25% 19% 4	760
	11th to 20th	Night	18% 9% 27% 29% 14% 2	760
	21st to end	Night	22% 10% 31% 25% 10% 2	836
November	1st to 10th	Night	18% 10% 29% 28% 13% 2	780
	11th to 20th	Night	23% 14% 31% 23% 8% 1	800
	21st to end	Night	19% 17% 31% 24% 8% 1	800
December	1st to 10th	Night	24% 17% 32% 20% 6% 1	800
	11th to 20th	Night	24% 19% 33% 19% 5%	800
	21st to end	Night	23% 14% 37% 20% 4	880

Page generated at 2025-06-07 10:28:14. Version ac07

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