Floyd Bennett Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Floyd Bennett Field clear sky chart from 2005-11-06 to 2024-03-23.

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% 6% 2 5% 5% 3 4 5% 5% 7% 42%	78627
	Night	17% 7% 3 5% 5% 3 4 4 5% 6% 42%	81249
Transparency	Day	40% 7% 13% 23% 16% 2	78332
	Night	42% 6% 12% 23% 16% 2	81078
Seeing	Day	18% 5% 24% 32% 18% 4	14144
	Night	19% 8% 29% 29% 14% 2	23442

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	15% 8% 2 4 4 3 3 3 4 6% 49%	2517
	11th to 20th	Day	15% 9% 3 5% 6% 4 5% 4 5% 6% 39%	2520
	21st to end	Day	21% 12% 4 6% 5% 3 4 3 4 5% 33%	3005
February	1st to 10th	Day	17% 8% 3 6% 4 3 4 4 5% 7% 40%	1736
	11th to 20th	Day	15% 6% 3 6% 5% 3 4 3 4 5% 46%	1848
	21st to end	Day	20% 7% 3 5% 4 3 5% 5% 5% 6% 38%	1570
March	1st to 10th	Day	16% 6% 3 5% 5% 2 4 4 4 7% 45%	1897
	11th to 20th	Day	14% 6% 2 5% 5% 3 5% 5% 5% 8% 41%	1990
	21st to end	Day	19% 7% 3 6% 5% 2 4 4 4 5% 41%	2387
April	1st to 10th	Day	18% 8% 3 5% 5% 3 3 4 5% 7% 41%	2160
	11th to 20th	Day	16% 5% 3 4 5% 3 4 5% 5% 7% 43%	2134
	21st to end	Day	19% 5% 3 4 4 3 5% 5% 5% 7% 40%	2183
May	1st to 10th	Day	23% 6% 2 5% 5% 3 4 4 5% 7% 37%	2340
	11th to 20th	Day	20% 5% 2 4 5% 3 4 5% 6% 8% 37%	2435
	21st to end	Day	16% 6% 2 4 5% 3 4 4 6% 9% 42%	2725
June	1st to 10th	Day	16% 6% 2 5% 4 3 4 6% 7% 10% 38%	2520
	11th to 20th	Day	15% 7% 2 5% 6% 3 5% 5% 6% 9% 38%	2520
	21st to end	Day	10% 4 3 5% 6% 3 4 6% 6% 10% 43%	2520
July	1st to 10th	Day	10% 5% 2 6% 5% 3 6% 6% 7% 9% 41%	2520
	11th to 20th	Day	9% 5% 2 5% 4 3 5% 6% 8% 10% 43%	2520
	21st to end	Day	12% 5% 3 5% 5% 4 6% 6% 7% 9% 39%	2744
August	1st to 10th	Day	9% 5% 2 5% 5% 4 6% 6% 7% 10% 42%	2356
	11th to 20th	Day	11% 5% 2 5% 5% 3 5% 6% 7% 8% 43%	2126
	21st to end	Day	12% 6% 3 5% 4 3 6% 5% 6% 9% 42%	2376
September	1st to 10th	Day	14% 4 3 5% 5% 3 4 4 5% 8% 45%	2160
	11th to 20th	Day	13% 4 2 4 4 3 3 4 5% 8% 50%	2075
	21st to end	Day	17% 6% 3 4 5% 3 4 5% 5% 6% 42%	1980
October	1st to 10th	Day	21% 5% 2 5% 4 3 3 4 5% 7% 42%	1895
	11th to 20th	Day	16% 4 2 4 5% 3 4 4 6% 7% 46%	1800
	21st to end	Day	20% 6% 3 4 4 3 3 4 4 6% 43%	1832
November	1st to 10th	Day	14% 6% 2 5% 4 2 3 3 4 6% 51%	1671
	11th to 20th	Day	17% 5% 3 4 4 2 4 4 5% 5% 48%	1710
	21st to end	Day	15% 6% 2 5% 4 2 4 4 5% 7% 46%	1657
December	1st to 10th	Day	18% 7% 2 6% 5% 3 4 4 5% 8% 39%	1520
	11th to 20th	Day	20% 7% 3 4 3 2 2 3 4 6% 46%	1906
	21st to end	Day	18% 8% 3 7% 6% 4 4 5% 6% 7% 33%	2772
January	1st to 10th	Night	17% 6% 2 4 4 2 3 4 4 5% 47%	4429
	11th to 20th	Night	17% 9% 3 5% 4 2 4 4 4 5% 43%	4440
	21st to end	Night	25% 10% 3 5% 4 2 4 3 4 5% 35%	4648
February	1st to 10th	Night	17% 7% 3 5% 5% 3 4 4 4 6% 42%	2442
	11th to 20th	Night	18% 7% 4 6% 4 2 5% 4 4 5% 42%	2218
	21st to end	Night	21% 6% 3 4 4 2 4 4 4 5% 43%	1884
March	1st to 10th	Night	17% 7% 3 4 4 2 3 4 4 7% 45%	2270
	11th to 20th	Night	16% 6% 3 5% 5% 3 4 4 5% 7% 42%	2186
	21st to end	Night	17% 8% 2 5% 6% 2 4 4 4 6% 42%	2013
April	1st to 10th	Night	18% 7% 3 6% 5% 3 5% 4 4 7% 39%	1800
	11th to 20th	Night	18% 7% 3 6% 4 2 4 4 5% 7% 40%	1775
	21st to end	Night	19% 7% 3 5% 4 2 4 4 4 6% 42%	1774
May	1st to 10th	Night	21% 9% 3 6% 5% 3 3 4 4 6% 35%	1620
	11th to 20th	Night	19% 7% 3 6% 5% 3 4 4 4 6% 39%	1472
	21st to end	Night	17% 8% 3 5% 5% 3 5% 3 5% 9% 39%	1550
June	1st to 10th	Night	18% 6% 2 5% 4 3 5% 4 6% 8% 39%	1440
	11th to 20th	Night	14% 6% 3 5% 6% 3 4 5% 7% 10% 39%	1440
	21st to end	Night	9% 6% 2 5% 6% 3 5% 5% 8% 9% 42%	1440
July	1st to 10th	Night	13% 5% 2 6% 5% 3 5% 6% 7% 8% 39%	1440
	11th to 20th	Night	10% 6% 2 4 6% 4 5% 6% 7% 9% 40%	1440
	21st to end	Night	11% 5% 2 5% 4 2 6% 6% 7% 9% 42%	1574
August	1st to 10th	Night	8% 5% 2 6% 5% 4 5% 7% 6% 9% 43%	1561
	11th to 20th	Night	12% 6% 3 5% 7% 4 5% 6% 6% 8% 38%	1774
	21st to end	Night	12% 6% 2 5% 5% 3 5% 5% 6% 8% 42%	1980
September	1st to 10th	Night	15% 5% 2 5% 5% 4 4 6% 6% 6% 42%	1800
	11th to 20th	Night	14% 5% 2 5% 4 2 3 3 5% 7% 52%	1885
	21st to end	Night	17% 6% 2 6% 5% 3 3 4 4 7% 43%	1980
October	1st to 10th	Night	20% 6% 2 6% 5% 4 3 3 5% 6% 41%	2061
	11th to 20th	Night	15% 4 2 5% 4 2 4 4 5% 7% 49%	2160
	21st to end	Night	21% 7% 3 5% 4 2 3 3 4 5% 43%	2523
November	1st to 10th	Night	12% 5% 2 5% 5% 3 4 4 4 6% 51%	2407
	11th to 20th	Night	20% 5% 2 4 4 2 3 3 4 5% 48%	2470
	21st to end	Night	15% 5% 2 4 4 3 4 4 6% 7% 47%	2521
December	1st to 10th	Night	21% 6% 3 4 4 3 4 4 5% 5% 40%	2660
	11th to 20th	Night	20% 6% 2 4 4 3 4 4 5% 6% 43%	3288
	21st to end	Night	20% 9% 3 6% 5% 3 4 4 5% 5% 37%	4884

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% 3 10% 30% 14% 3	2518
	11th to 20th	Day	44% 4 14% 22% 14% 2	2520
	21st to end	Day	53% 6% 9% 21% 9% 2	3005
February	1st to 10th	Day	44% 5% 14% 22% 14% 1	1736
	11th to 20th	Day	42% 4 9% 25% 17% 3	1857
	21st to end	Day	45% 5% 11% 22% 13% 4	1570
March	1st to 10th	Day	38% 5% 14% 24% 15% 3	1900
	11th to 20th	Day	38% 5% 14% 26% 15% 2	1990
	21st to end	Day	44% 6% 10% 19% 17% 4	2387
April	1st to 10th	Day	41% 5% 11% 20% 18% 5%	2160
	11th to 20th	Day	38% 6% 12% 23% 17% 3	2134
	21st to end	Day	41% 7% 11% 20% 17% 4	2183
May	1st to 10th	Day	46% 7% 10% 19% 15% 2	2340
	11th to 20th	Day	43% 7% 12% 20% 16% 2	2439
	21st to end	Day	39% 9% 16% 21% 13% 2	2725
June	1st to 10th	Day	39% 8% 16% 21% 14% 1	2520
	11th to 20th	Day	40% 9% 14% 23% 12% 2	2520
	21st to end	Day	35% 9% 16% 24% 16% 1	2520
July	1st to 10th	Day	36% 10% 14% 22% 17% 1	2450
	11th to 20th	Day	32% 9% 16% 26% 14% 2	2445
	21st to end	Day	35% 10% 13% 24% 16% 2	2591
August	1st to 10th	Day	31% 10% 17% 27% 14% 1	2342
	11th to 20th	Day	34% 10% 16% 24% 15% 2	2126
	21st to end	Day	35% 8% 14% 22% 19% 2	2376
September	1st to 10th	Day	36% 6% 15% 22% 19% 2	2160
	11th to 20th	Day	31% 6% 13% 25% 24% 2	2075
	21st to end	Day	41% 6% 11% 18% 21% 3	1980
October	1st to 10th	Day	41% 6% 11% 22% 17% 2	1895
	11th to 20th	Day	36% 5% 12% 25% 20% 2	1800
	21st to end	Day	42% 4 11% 22% 18% 2	1832
November	1st to 10th	Day	36% 4 13% 25% 20% 2	1671
	11th to 20th	Day	38% 5% 10% 23% 22% 3	1710
	21st to end	Day	38% 5% 14% 30% 12% 2	1657
December	1st to 10th	Day	45% 5% 15% 20% 14% 1	1520
	11th to 20th	Day	42% 3 14% 24% 15% 2	1906
	21st to end	Day	48% 7% 11% 24% 9%	2772
January	1st to 10th	Night	39% 4 11% 31% 12% 3	4429
	11th to 20th	Night	44% 4 12% 25% 13% 2	4440
	21st to end	Night	53% 4 8% 22% 12% 1	4648
February	1st to 10th	Night	43% 5% 14% 23% 12% 2	2442
	11th to 20th	Night	45% 5% 10% 19% 18% 4	2220
	21st to end	Night	44% 4 9% 23% 18% 3	1884
March	1st to 10th	Night	40% 4 12% 24% 15% 4	2280
	11th to 20th	Night	42% 5% 10% 22% 17% 4	2187
	21st to end	Night	44% 5% 9% 18% 19% 6%	2013
April	1st to 10th	Night	45% 5% 10% 20% 17% 4	1800
	11th to 20th	Night	43% 5% 10% 18% 22% 2	1775
	21st to end	Night	44% 6% 9% 20% 18% 5%	1774
May	1st to 10th	Night	50% 7% 11% 17% 14% 2	1620
	11th to 20th	Night	47% 7% 10% 16% 17% 3	1473
	21st to end	Night	44% 8% 15% 19% 12% 2	1551
June	1st to 10th	Night	43% 6% 10% 20% 19% 1	1440
	11th to 20th	Night	40% 8% 14% 25% 12% 1	1440
	21st to end	Night	36% 8% 15% 24% 15% 2	1440
July	1st to 10th	Night	41% 9% 14% 20% 14% 2	1400
	11th to 20th	Night	38% 8% 13% 26% 14% 2	1392
	21st to end	Night	35% 9% 16% 23% 14% 3	1486
August	1st to 10th	Night	34% 10% 18% 21% 14% 2	1551
	11th to 20th	Night	40% 9% 14% 25% 11% 1	1774
	21st to end	Night	38% 8% 14% 20% 18% 2	1980
September	1st to 10th	Night	41% 7% 11% 22% 18% 2	1800
	11th to 20th	Night	33% 5% 12% 23% 24% 3	1885
	21st to end	Night	42% 6% 7% 22% 20% 2	1980
October	1st to 10th	Night	45% 7% 11% 20% 15% 2	2061
	11th to 20th	Night	36% 5% 14% 27% 17% 2	2160
	21st to end	Night	45% 5% 10% 22% 18% 1	2523
November	1st to 10th	Night	36% 4 12% 24% 21% 4	2407
	11th to 20th	Night	41% 3 10% 23% 19% 4	2470
	21st to end	Night	37% 5% 13% 28% 16% 1	2521
December	1st to 10th	Night	46% 5% 13% 22% 13% 1	2660
	11th to 20th	Night	41% 6% 12% 20% 17% 3	3288
	21st to end	Night	46% 7% 12% 23% 12%	4884

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	15% 12% 41% 22% 9% 1	180
	11th to 20th	Day	14% 15% 48% 18% 4 1	180
	21st to end	Day	22% 7% 37% 25% 9% 2	265
February	1st to 10th	Day	25% 7% 33% 30% 5%	296
	11th to 20th	Day	19% 12% 39% 28% 3	456
	21st to end	Day	23% 11% 34% 27% 4 1	382
March	1st to 10th	Day	17% 10% 36% 30% 8%	460
	11th to 20th	Day	15% 6% 43% 28% 7% 2	460
	21st to end	Day	22% 6% 34% 28% 8% 1	470
April	1st to 10th	Day	20% 8% 31% 31% 9%	420
	11th to 20th	Day	19% 7% 23% 36% 13% 2	412
	21st to end	Day	23% 6% 29% 32% 9% 1	420
May	1st to 10th	Day	28% 4 24% 31% 10% 2	423
	11th to 20th	Day	20% 2 21% 40% 14% 2	447
	21st to end	Day	19% 2 14% 29% 30% 6%	485
June	1st to 10th	Day	19% 2 17% 35% 24% 3	450
	11th to 20th	Day	14% 2 20% 39% 21% 4	450
	21st to end	Day	12% 2 15% 40% 28% 3	450
July	1st to 10th	Day	12% 3 9% 36% 32% 8%	445
	11th to 20th	Day	8% 2 9% 34% 37% 10%	444
	21st to end	Day	12% 2 12% 39% 31% 5%	488
August	1st to 10th	Day	10% 1 7% 42% 32% 7%	446
	11th to 20th	Day	14% 1 9% 33% 36% 6%	439
	21st to end	Day	13% 1 13% 35% 28% 10%	495
September	1st to 10th	Day	16% 2 15% 32% 25% 10%	450
	11th to 20th	Day	14% 2 14% 34% 27% 9%	450
	21st to end	Day	22% 2 19% 34% 18% 5%	450
October	1st to 10th	Day	25% 3 17% 28% 22% 5%	450
	11th to 20th	Day	17% 5% 25% 29% 20% 3	450
	21st to end	Day	21% 7% 31% 25% 14% 2	421
November	1st to 10th	Day	15% 8% 26% 32% 17% 3	365
	11th to 20th	Day	17% 11% 36% 26% 9%	370
	21st to end	Day	18% 9% 32% 29% 11% 1	317
December	1st to 10th	Day	18% 8% 41% 22% 11%	180
	11th to 20th	Day	23% 17% 29% 26% 5% 1	180
	21st to end	Day	26% 9% 32% 21% 11% 1	198
January	1st to 10th	Night	19% 15% 42% 21% 4	760
	11th to 20th	Night	24% 13% 35% 24% 5%	760
	21st to end	Night	18% 14% 42% 22% 3	836
February	1st to 10th	Night	21% 13% 38% 26% 3	760
	11th to 20th	Night	22% 14% 42% 21% 1	743
	21st to end	Night	22% 12% 37% 24% 5%	628
March	1st to 10th	Night	20% 10% 40% 24% 6%	760
	11th to 20th	Night	19% 9% 38% 26% 6% 1	760
	21st to end	Night	20% 6% 36% 29% 7% 1	801
April	1st to 10th	Night	20% 6% 37% 29% 7% 1	720
	11th to 20th	Night	20% 5% 28% 37% 10%	711
	21st to end	Night	20% 5% 30% 35% 10% 1	694
May	1st to 10th	Night	23% 5% 25% 31% 13% 2	540
	11th to 20th	Night	21% 3 26% 37% 12% 1	411
	21st to end	Night	19% 3 13% 33% 26% 6%	389
June	1st to 10th	Night	21% 3 15% 35% 23% 3	360
	11th to 20th	Night	16% 1 14% 43% 24% 2	360
	21st to end	Night	8% 2 14% 47% 27% 1	360
July	1st to 10th	Night	12% 4 13% 37% 31% 4	350
	11th to 20th	Night	10% 3 10% 36% 34% 6%	348
	21st to end	Night	10% 2 15% 39% 30% 4	394
August	1st to 10th	Night	10% 1 11% 42% 33% 3	487
	11th to 20th	Night	14% 2 12% 33% 35% 5%	710
	21st to end	Night	14% 2 12% 35% 31% 6%	792
September	1st to 10th	Night	18% 2 18% 32% 25% 6%	720
	11th to 20th	Night	17% 3 15% 35% 25% 7%	720
	21st to end	Night	22% 1 20% 33% 20% 4	720
October	1st to 10th	Night	23% 6% 23% 25% 19% 5%	720
	11th to 20th	Night	17% 8% 25% 34% 15% 1	720
	21st to end	Night	24% 7% 32% 26% 10% 1	792
November	1st to 10th	Night	15% 7% 33% 29% 13% 2	740
	11th to 20th	Night	20% 12% 32% 24% 11% 1	760
	21st to end	Night	15% 13% 37% 25% 9% 1	760
December	1st to 10th	Night	24% 13% 33% 22% 6% 1	760
	11th to 20th	Night	22% 11% 38% 25% 4	760
	21st to end	Night	22% 10% 40% 24% 4	836

Page generated at 2024-03-19 23:31:06. Version ac07

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