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 2025-08-05.

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% 7% 2 6% 4 4 4 3 5% 8% 41%	125721
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 42%	122343
Transparency	Day	26% 40% 8% 14% 11% 2	129248
	Night	26% 39% 7% 14% 11% 2	126903
Seeing	Day	17% 5% 23% 32% 18% 4	15978
	Night	19% 8% 29% 29% 14% 2	25075

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 4 3 3 3 3 4 6% 53%	3597
	11th to 20th	Day	13% 9% 2 6% 5% 4 4 3 5% 6% 45%	3570
	21st to end	Day	18% 10% 4 7% 4 4 4 3 4 4 40%	4305
February	1st to 10th	Day	16% 8% 3 7% 4 4 4 3 5% 7% 39%	1828
	11th to 20th	Day	15% 7% 3 7% 4 4 4 2 4 6% 44%	1948
	21st to end	Day	19% 8% 3 6% 4 4 4 3 5% 6% 39%	1650
March	1st to 10th	Day	22% 6% 2 5% 3 3 4 2 5% 6% 43%	4476
	11th to 20th	Day	12% 8% 2 6% 4 5% 4 4 6% 8% 42%	4745
	21st to end	Day	17% 6% 3 6% 4 3 3 3 5% 6% 43%	5957
April	1st to 10th	Day	19% 8% 3 6% 4 3 4 4 5% 7% 39%	2400
	11th to 20th	Day	17% 6% 2 6% 4 4 4 3 6% 7% 41%	2374
	21st to end	Day	17% 6% 2 5% 4 4 5% 4 5% 7% 41%	2427
May	1st to 10th	Day	27% 8% 2 5% 3 4 4 3 5% 8% 29%	5886
	11th to 20th	Day	23% 9% 2 6% 4 4 3 3 4 6% 35%	6219
	21st to end	Day	21% 7% 2 5% 4 4 4 4 6% 8% 35%	6949
June	1st to 10th	Day	16% 7% 2 5% 4 4 4 5% 7% 9% 38%	2800
	11th to 20th	Day	15% 7% 1 6% 5% 4 5% 4 6% 9% 39%	2800
	21st to end	Day	11% 5% 2 6% 5% 4 4 4 6% 9% 43%	2800
July	1st to 10th	Day	10% 7% 3 7% 5% 5% 5% 5% 7% 10% 37%	6360
	11th to 20th	Day	10% 7% 3 7% 5% 5% 6% 4 8% 12% 33%	6360
	21st to end	Day	12% 7% 3 6% 4 4 5% 4 6% 9% 41%	6926
August	1st to 10th	Day	18% 6% 2 6% 4 4 5% 4 6% 9% 34%	4190
	11th to 20th	Day	13% 5% 2 5% 4 4 5% 4 7% 9% 42%	3730
	21st to end	Day	9% 5% 2 5% 3 4 5% 4 6% 9% 48%	4180
September	1st to 10th	Day	13% 4 3 5% 4 4 4 4 5% 7% 46%	2280
	11th to 20th	Day	12% 5% 2 5% 3 3 4 3 5% 8% 50%	2190
	21st to end	Day	19% 7% 2 5% 4 3 4 4 5% 5% 41%	2090
October	1st to 10th	Day	20% 5% 2 6% 3 4 3 3 5% 7% 42%	2000
	11th to 20th	Day	15% 4 2 5% 4 4 4 3 6% 7% 48%	1900
	21st to end	Day	19% 6% 2 5% 3 3 3 3 4 7% 45%	1933
November	1st to 10th	Day	13% 6% 2 6% 3 3 2 2 4 6% 52%	1761
	11th to 20th	Day	16% 5% 2 5% 3 3 4 3 5% 5% 49%	1800
	21st to end	Day	16% 6% 2 5% 4 4 3 4 5% 6% 46%	1744
December	1st to 10th	Day	15% 7% 2 5% 4 3 3 3 5% 7% 46%	2600
	11th to 20th	Day	21% 8% 2 4 3 2 2 2 3 7% 45%	2986
	21st to end	Day	17% 7% 3 6% 5% 4 3 3 5% 6% 40%	3960
January	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 51%	6349
	11th to 20th	Night	15% 8% 2 5% 4 3 3 3 4 5% 48%	6315
	21st to end	Night	18% 9% 2 6% 4 4 4 4 5% 6% 39%	6648
February	1st to 10th	Night	18% 8% 3 5% 4 4 4 3 4 6% 41%	2570
	11th to 20th	Night	18% 8% 3 6% 4 3 4 3 4 5% 42%	2338
	21st to end	Night	20% 7% 2 5% 4 3 4 3 5% 5% 42%	1980
March	1st to 10th	Night	19% 9% 3 5% 3 3 3 3 4 6% 44%	5364
	11th to 20th	Night	14% 11% 3 5% 4 4 3 3 4 6% 44%	5211
	21st to end	Night	18% 9% 3 7% 4 3 4 3 4 5% 39%	4974
April	1st to 10th	Night	19% 8% 3 6% 5% 4 5% 3 5% 7% 37%	2000
	11th to 20th	Night	19% 8% 3 6% 4 3 4 4 5% 7% 39%	1975
	21st to end	Night	18% 7% 3 6% 3 3 4 4 4 6% 43%	1970
May	1st to 10th	Night	26% 10% 4 7% 4 4 4 3 5% 7% 27%	4054
	11th to 20th	Night	23% 9% 3 6% 4 4 3 3 4 6% 35%	3716
	21st to end	Night	22% 9% 2 6% 4 3 4 3 5% 7% 34%	3926
June	1st to 10th	Night	17% 7% 2 5% 4 4 4 4 6% 8% 40%	1600
	11th to 20th	Night	14% 7% 3 6% 5% 4 4 4 7% 9% 38%	1600
	21st to end	Night	10% 6% 1 6% 5% 4 5% 5% 8% 9% 40%	1600
July	1st to 10th	Night	10% 7% 4 9% 6% 6% 5% 5% 6% 8% 35%	3600
	11th to 20th	Night	14% 10% 3 7% 5% 4 5% 4 7% 9% 32%	3600
	21st to end	Night	14% 6% 2 6% 4 4 4 4 6% 8% 42%	3926
August	1st to 10th	Night	22% 6% 2 7% 3 4 5% 4 6% 7% 31%	2779
	11th to 20th	Night	14% 7% 3 7% 5% 5% 4 4 6% 7% 39%	3097
	21st to end	Night	8% 5% 2 5% 3 4 4 3 6% 8% 52%	3476
September	1st to 10th	Night	14% 5% 2 6% 4 4 4 4 5% 6% 44%	1900
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 7% 52%	1990
	21st to end	Night	18% 6% 2 6% 4 4 3 3 5% 7% 42%	2090
October	1st to 10th	Night	19% 6% 2 6% 4 5% 3 3 5% 6% 42%	2176
	11th to 20th	Night	14% 4 2 5% 3 3 3 3 5% 7% 50%	2280
	21st to end	Night	20% 7% 2 5% 3 3 3 3 4 5% 44%	2664
November	1st to 10th	Night	12% 5% 2 6% 4 4 3 3 4 6% 52%	2537
	11th to 20th	Night	19% 5% 2 5% 3 3 3 3 4 5% 48%	2600
	21st to end	Night	15% 6% 2 5% 4 3 4 3 6% 6% 46%	2654
December	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 5% 5% 48%	4580
	11th to 20th	Night	25% 7% 2 4 3 3 3 3 4 4 43%	5208
	21st to end	Night	19% 9% 3 6% 4 3 4 3 5% 5% 41%	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	22% 27% 5% 25% 19% 2	3598
	11th to 20th	Day	29% 27% 7% 18% 14% 5%	3600
	21st to end	Day	36% 30% 8% 15% 10% 1	4305
February	1st to 10th	Day	19% 63% 6% 8% 4	1828
	11th to 20th	Day	18% 60% 3 9% 8% 1	1957
	21st to end	Day	17% 62% 5% 9% 5% 2	1650
March	1st to 10th	Day	29% 30% 8% 14% 12% 7%	4479
	11th to 20th	Day	27% 31% 10% 20% 9% 3	4745
	21st to end	Day	29% 31% 8% 9% 19% 4	5957
April	1st to 10th	Day	19% 62% 4 7% 6% 1	2400
	11th to 20th	Day	14% 63% 5% 9% 7% 1	2374
	21st to end	Day	15% 63% 4 9% 7% 1	2427
May	1st to 10th	Day	41% 32% 12% 8% 5%	5897
	11th to 20th	Day	37% 29% 9% 15% 9%	6223
	21st to end	Day	34% 31% 8% 16% 11%	6949
June	1st to 10th	Day	16% 63% 4 8% 8%	2800
	11th to 20th	Day	16% 62% 4 10% 7%	2800
	21st to end	Day	13% 63% 6% 9% 8% 1	2800
July	1st to 10th	Day	34% 31% 8% 15% 12%	6290
	11th to 20th	Day	34% 32% 15% 13% 6%	6285
	21st to end	Day	29% 28% 9% 17% 17% 1	6728
August	1st to 10th	Day	31% 39% 10% 14% 5%	4176
	11th to 20th	Day	22% 40% 9% 23% 5%	3766
	21st to end	Day	15% 39% 9% 23% 13% 1	4180
September	1st to 10th	Day	14% 61% 7% 10% 7%	2280
	11th to 20th	Day	15% 60% 5% 9% 11%	2190
	21st to end	Day	21% 61% 4 7% 6%	2090
October	1st to 10th	Day	19% 38% 9% 13% 16% 5%	3325
	11th to 20th	Day	10% 37% 8% 15% 26% 4	3140
	21st to end	Day	13% 37% 11% 19% 18% 2	3158
November	1st to 10th	Day	17% 56% 7% 9% 9% 2	1761
	11th to 20th	Day	14% 57% 3 12% 13% 2	1800
	21st to end	Day	15% 57% 7% 14% 6% 1	1744
December	1st to 10th	Day	25% 36% 10% 19% 9% 1	2600
	11th to 20th	Day	30% 31% 7% 19% 11% 3	2986
	21st to end	Day	32% 29% 6% 18% 13% 2	3960
January	1st to 10th	Night	25% 26% 6% 20% 19% 4	6349
	11th to 20th	Night	27% 27% 9% 18% 14% 5%	6360
	21st to end	Night	36% 29% 6% 13% 12% 3	6648
February	1st to 10th	Night	17% 62% 6% 10% 3 1	2570
	11th to 20th	Night	18% 60% 3 8% 9% 2	2340
	21st to end	Night	18% 62% 4 7% 7% 2	1980
March	1st to 10th	Night	33% 29% 6% 15% 9% 8%	5374
	11th to 20th	Night	29% 30% 10% 19% 9% 3	5212
	21st to end	Night	35% 30% 4 9% 18% 4	4974
April	1st to 10th	Night	20% 62% 3 8% 6% 1	2000
	11th to 20th	Night	15% 63% 5% 8% 8% 1	1975
	21st to end	Night	17% 62% 3 9% 7% 1	1970
May	1st to 10th	Night	42% 32% 10% 10% 5% 1	4060
	11th to 20th	Night	39% 31% 9% 11% 9% 1	3717
	21st to end	Night	37% 30% 8% 15% 8% 1	3927
June	1st to 10th	Night	16% 63% 3 8% 10%	1600
	11th to 20th	Night	16% 62% 5% 11% 6%	1600
	21st to end	Night	15% 62% 5% 10% 8% 1	1600
July	1st to 10th	Night	36% 30% 8% 15% 10% 1	3560
	11th to 20th	Night	37% 30% 12% 16% 6%	3552
	21st to end	Night	30% 28% 11% 18% 14% 1	3809
August	1st to 10th	Night	37% 40% 10% 9% 4 1	2769
	11th to 20th	Night	27% 40% 8% 19% 6%	3127
	21st to end	Night	15% 38% 7% 25% 15% 1	3476
September	1st to 10th	Night	15% 62% 6% 11% 6% 1	1900
	11th to 20th	Night	14% 60% 5% 9% 10% 2	1990
	21st to end	Night	22% 60% 4 8% 6% 1	2090
October	1st to 10th	Night	22% 39% 8% 15% 15% 2	3631
	11th to 20th	Night	10% 37% 6% 18% 26% 4	3779
	21st to end	Night	13% 37% 8% 22% 17% 2	4389
November	1st to 10th	Night	17% 56% 5% 11% 9% 2	2537
	11th to 20th	Night	16% 57% 3 9% 11% 3	2600
	21st to end	Night	15% 58% 6% 13% 7% 1	2654
December	1st to 10th	Night	25% 36% 7% 22% 8% 2	4580
	11th to 20th	Night	32% 32% 6% 17% 10% 3	5208
	21st to end	Night	34% 28% 7% 13% 14% 3	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	15% 14% 42% 21% 8% 1	200
	11th to 20th	Day	14% 15% 48% 19% 4 1	200
	21st to end	Day	20% 7% 39% 25% 8% 1	295
February	1st to 10th	Day	23% 7% 35% 30% 5%	328
	11th to 20th	Day	20% 13% 38% 26% 2	496
	21st to end	Day	22% 10% 34% 28% 5% 1	414
March	1st to 10th	Day	16% 10% 37% 30% 7%	500
	11th to 20th	Day	16% 6% 41% 29% 7% 1	500
	21st to end	Day	21% 6% 34% 29% 8% 1	550
April	1st to 10th	Day	22% 7% 32% 30% 9%	500
	11th to 20th	Day	19% 9% 24% 35% 11% 1	492
	21st to end	Day	20% 7% 27% 34% 11% 1	500
May	1st to 10th	Day	27% 5% 23% 32% 11% 2	503
	11th to 20th	Day	21% 2 20% 39% 15% 2	527
	21st to end	Day	19% 3 14% 31% 28% 5%	573
June	1st to 10th	Day	18% 2 17% 37% 23% 3	530
	11th to 20th	Day	16% 2 19% 38% 22% 4	530
	21st to end	Day	13% 2 14% 39% 28% 4	530
July	1st to 10th	Day	11% 3 9% 37% 33% 8%	525
	11th to 20th	Day	8% 2 9% 35% 36% 9%	524
	21st to end	Day	12% 2 11% 38% 33% 4	576
August	1st to 10th	Day	11% 1 7% 41% 32% 7%	502
	11th to 20th	Day	14% 2 9% 33% 36% 7%	479
	21st to end	Day	12% 1 13% 36% 29% 10%	539
September	1st to 10th	Day	16% 2 14% 32% 25% 10%	490
	11th to 20th	Day	13% 2 12% 33% 29% 10%	490
	21st to end	Day	24% 2 18% 33% 18% 5%	490
October	1st to 10th	Day	24% 3 16% 29% 22% 6%	490
	11th to 20th	Day	16% 5% 26% 29% 20% 4	490
	21st to end	Day	20% 7% 29% 26% 16% 3	456
November	1st to 10th	Day	14% 7% 25% 34% 16% 3	395
	11th to 20th	Day	16% 11% 35% 28% 10%	400
	21st to end	Day	19% 10% 33% 27% 10% 1	344
December	1st to 10th	Day	18% 8% 40% 24% 11%	200
	11th to 20th	Day	24% 16% 29% 24% 7% 1	200
	21st to end	Day	24% 8% 31% 23% 13%	220
January	1st to 10th	Night	18% 16% 42% 20% 4	800
	11th to 20th	Night	24% 13% 35% 24% 5%	800
	21st to end	Night	18% 14% 43% 22% 3	880
February	1st to 10th	Night	22% 13% 38% 25% 3	800
	11th to 20th	Night	22% 15% 40% 20% 1	783
	21st to end	Night	21% 12% 38% 25% 5%	660
March	1st to 10th	Night	20% 10% 40% 24% 6%	800
	11th to 20th	Night	20% 9% 37% 27% 7% 1	800
	21st to end	Night	20% 7% 36% 29% 7% 1	880
April	1st to 10th	Night	20% 7% 36% 29% 7% 1	800
	11th to 20th	Night	20% 6% 30% 35% 9%	791
	21st to end	Night	19% 4 30% 36% 10% 1	770
May	1st to 10th	Night	23% 6% 25% 32% 13% 2	600
	11th to 20th	Night	21% 3 25% 37% 12% 1	457
	21st to end	Night	20% 3 13% 34% 24% 5%	433
June	1st to 10th	Night	20% 3 15% 36% 23% 3	400
	11th to 20th	Night	16% 1 14% 43% 25% 2	400
	21st to end	Night	9% 2 16% 45% 26% 2	400
July	1st to 10th	Night	12% 4 12% 36% 33% 4	390
	11th to 20th	Night	11% 3 11% 35% 34% 6%	388
	21st to end	Night	10% 2 14% 39% 31% 3	438
August	1st to 10th	Night	11% 2 10% 41% 32% 3	523
	11th to 20th	Night	14% 2 12% 33% 34% 5%	750
	21st to end	Night	13% 2 12% 34% 32% 6%	836
September	1st to 10th	Night	17% 2 18% 32% 25% 6%	760
	11th to 20th	Night	16% 3 14% 34% 26% 7%	760
	21st to end	Night	22% 1 20% 33% 20% 4	760
October	1st to 10th	Night	23% 6% 23% 25% 19% 5%	760
	11th to 20th	Night	16% 8% 26% 34% 14% 2	760
	21st to end	Night	23% 6% 31% 27% 11% 1	836
November	1st to 10th	Night	14% 7% 33% 30% 13% 2	780
	11th to 20th	Night	20% 11% 33% 25% 11% 1	800
	21st to end	Night	16% 14% 36% 25% 8% 1	800
December	1st to 10th	Night	24% 14% 33% 22% 7% 1	800
	11th to 20th	Night	23% 11% 37% 25% 4	800
	21st to end	Night	22% 10% 39% 24% 4	880

Page generated at 2025-08-02 01:32:26. Version ac07

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