Finger Lakes Regional Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Finger Lakes Regional Airport clear sky chart from 2005-11-06 to 2026-06-16.

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% 11% 4 9% 6% 5% 5% 4 5% 7% 29%	138090
	Night	17% 13% 4 10% 6% 5% 4 3 5% 6% 27%	133902
Transparency	Day	53% 7% 12% 19% 9% 1	141634
	Night	57% 6% 11% 17% 9% 1	138445
Seeing	Day	23% 16% 29% 20% 10% 3	16637
	Night	24% 15% 27% 25% 9% 1	25931

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	17% 16% 7% 22% 7% 4 5% 3 3 3 13%	4661
	11th to 20th	Day	12% 19% 8% 17% 11% 6% 4 3 4 4 12%	4709
	21st to end	Day	13% 14% 6% 15% 12% 10% 6% 3 4 5% 13%	5780
February	1st to 10th	Day	17% 15% 7% 14% 9% 6% 5% 4 4 4 15%	1890
	11th to 20th	Day	15% 17% 8% 15% 7% 6% 5% 3 5% 5% 14%	1845
	21st to end	Day	20% 14% 4 13% 8% 5% 5% 5% 4 5% 19%	1730
March	1st to 10th	Day	18% 15% 4 11% 7% 5% 4 3 3 4 25%	4764
	11th to 20th	Day	11% 17% 5% 9% 5% 4 4 3 4 6% 31%	5090
	21st to end	Day	17% 12% 5% 11% 6% 5% 5% 3 4 5% 27%	5770
April	1st to 10th	Day	19% 13% 4 8% 6% 4 5% 3 4 6% 28%	2520
	11th to 20th	Day	20% 10% 3 7% 5% 4 5% 4 5% 6% 34%	2494
	21st to end	Day	20% 12% 3 7% 4 4 4 3 5% 6% 32%	2591
May	1st to 10th	Day	25% 9% 3 7% 5% 4 5% 4 5% 6% 28%	8013
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 3 6% 7% 34%	8221
	21st to end	Day	20% 8% 3 7% 4 4 4 4 6% 8% 33%	9060
June	1st to 10th	Day	16% 8% 3 6% 4 4 5% 4 6% 8% 36%	2940
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 5% 7% 9% 37%	2870
	21st to end	Day	13% 6% 3 6% 5% 5% 6% 4 7% 9% 37%	2800
July	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 4 7% 10% 39%	6360
	11th to 20th	Day	8% 6% 2 7% 5% 5% 6% 5% 8% 11% 36%	6360
	21st to end	Day	10% 5% 2 6% 4 5% 6% 4 6% 8% 43%	6848
August	1st to 10th	Day	16% 6% 2 6% 4 5% 4 5% 6% 8% 37%	4234
	11th to 20th	Day	14% 7% 3 8% 6% 6% 5% 4 7% 8% 33%	4113
	21st to end	Day	12% 7% 2 7% 4 5% 5% 4 5% 7% 41%	4312
September	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 6% 8% 42%	2400
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 8% 44%	2400
	21st to end	Day	16% 7% 3 8% 5% 5% 5% 4 5% 7% 34%	2113
October	1st to 10th	Day	15% 9% 3 7% 5% 4 5% 3 6% 7% 37%	2000
	11th to 20th	Day	20% 8% 4 8% 5% 5% 5% 4 6% 7% 30%	2000
	21st to end	Day	23% 13% 3 8% 6% 4 4 4 5% 6% 24%	2150
November	1st to 10th	Day	14% 12% 3 9% 6% 5% 5% 3 5% 7% 31%	1851
	11th to 20th	Day	14% 15% 6% 10% 6% 5% 4 4 5% 6% 25%	1727
	21st to end	Day	20% 15% 4 9% 6% 4 4 5% 5% 7% 20%	1680
December	1st to 10th	Day	20% 18% 6% 16% 7% 5% 4 3 5% 5% 11%	2680
	11th to 20th	Day	19% 16% 7% 15% 5% 4 4 3 4 5% 19%	3066
	21st to end	Day	22% 16% 5% 13% 8% 5% 5% 3 4 6% 14%	4048
January	1st to 10th	Night	16% 18% 8% 22% 7% 5% 4 2 3 4 11%	8234
	11th to 20th	Night	13% 22% 8% 18% 8% 5% 4 3 4 4 11%	8175
	21st to end	Night	15% 15% 7% 12% 9% 7% 6% 4 5% 5% 16%	8401
February	1st to 10th	Night	17% 15% 6% 12% 8% 6% 5% 4 5% 5% 18%	2730
	11th to 20th	Night	16% 17% 5% 13% 7% 6% 5% 4 4 5% 18%	2659
	21st to end	Night	18% 13% 6% 14% 6% 4 4 4 5% 5% 21%	2076
March	1st to 10th	Night	17% 12% 6% 12% 7% 4 4 3 5% 6% 25%	5278
	11th to 20th	Night	17% 17% 3 8% 4 3 3 3 5% 6% 30%	5089
	21st to end	Night	21% 11% 5% 11% 5% 4 4 3 5% 5% 26%	5402
April	1st to 10th	Night	20% 12% 4 8% 5% 4 5% 4 5% 6% 27%	2100
	11th to 20th	Night	21% 10% 2 7% 5% 4 4 3 4 6% 33%	2075
	21st to end	Night	18% 9% 3 7% 5% 3 4 3 6% 7% 35%	2047
May	1st to 10th	Night	27% 10% 3 8% 5% 4 5% 3 4 6% 25%	4884
	11th to 20th	Night	18% 9% 3 7% 4 5% 4 3 6% 7% 35%	4639
	21st to end	Night	20% 8% 3 6% 5% 4 4 4 6% 6% 34%	5114
June	1st to 10th	Night	16% 6% 3 7% 4 5% 4 4 6% 8% 37%	1680
	11th to 20th	Night	12% 7% 3 7% 4 5% 5% 4 7% 8% 39%	1640
	21st to end	Night	12% 7% 2 6% 5% 5% 5% 5% 5% 7% 42%	1600
July	1st to 10th	Night	10% 7% 3 8% 5% 4 5% 4 7% 11% 37%	3600
	11th to 20th	Night	10% 6% 3 6% 4 5% 5% 4 6% 9% 43%	3600
	21st to end	Night	11% 6% 2 6% 4 4 5% 4 7% 8% 45%	3987
August	1st to 10th	Night	14% 7% 3 7% 4 4 4 4 6% 8% 39%	2915
	11th to 20th	Night	17% 6% 2 7% 5% 5% 4 4 5% 6% 39%	2903
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 7% 8% 44%	3586
September	1st to 10th	Night	14% 6% 2 7% 4 4 5% 3 5% 8% 43%	2000
	11th to 20th	Night	14% 5% 2 6% 4 3 4 3 5% 7% 46%	2000
	21st to end	Night	17% 8% 3 6% 4 4 5% 5% 6% 6% 36%	2283
October	1st to 10th	Night	19% 8% 3 8% 6% 4 4 4 5% 6% 35%	2400
	11th to 20th	Night	21% 8% 3 7% 4 4 4 3 5% 7% 32%	2400
	21st to end	Night	26% 11% 4 9% 5% 4 4 3 4 5% 26%	2690
November	1st to 10th	Night	16% 13% 4 7% 5% 4 4 3 5% 5% 33%	2667
	11th to 20th	Night	17% 13% 4 8% 6% 4 5% 3 5% 7% 27%	2890
	21st to end	Night	18% 18% 4 8% 5% 5% 5% 4 5% 6% 22%	2940
December	1st to 10th	Night	17% 21% 8% 13% 6% 5% 5% 3 5% 5% 12%	4720
	11th to 20th	Night	21% 17% 6% 12% 6% 4 4 3 3 5% 19%	5348
	21st to end	Night	25% 18% 4 10% 5% 5% 5% 3 5% 5% 14%	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	76% 6% 10% 6% 2	4662
	11th to 20th	Day	75% 5% 8% 6% 5% 1	4739
	21st to end	Day	74% 5% 9% 9% 3	5780
February	1st to 10th	Day	73% 6% 9% 9% 3	1890
	11th to 20th	Day	73% 6% 7% 11% 2	1854
	21st to end	Day	68% 7% 9% 12% 4	1730
March	1st to 10th	Day	62% 6% 10% 15% 6%	4767
	11th to 20th	Day	53% 6% 18% 13% 9% 1	5090
	21st to end	Day	58% 6% 7% 18% 10% 1	5770
April	1st to 10th	Day	57% 6% 10% 16% 10% 1	2520
	11th to 20th	Day	52% 6% 11% 18% 12% 1	2494
	21st to end	Day	52% 6% 8% 19% 13% 2	2591
May	1st to 10th	Day	56% 7% 10% 18% 9% 1	8023
	11th to 20th	Day	48% 7% 10% 24% 10% 1	8225
	21st to end	Day	48% 6% 12% 22% 11% 1	9061
June	1st to 10th	Day	44% 9% 11% 20% 16% 1	2940
	11th to 20th	Day	42% 8% 14% 23% 12% 1	2870
	21st to end	Day	42% 10% 14% 21% 13% 1	2800
July	1st to 10th	Day	39% 7% 13% 27% 13% 1	6290
	11th to 20th	Day	38% 9% 16% 24% 13% 1	6285
	21st to end	Day	36% 8% 13% 28% 14% 1	6651
August	1st to 10th	Day	44% 8% 13% 21% 14% 1	4221
	11th to 20th	Day	46% 9% 15% 23% 7%	4152
	21st to end	Day	41% 6% 11% 32% 8% 1	4312
September	1st to 10th	Day	39% 8% 11% 28% 12% 1	2400
	11th to 20th	Day	38% 7% 12% 26% 16% 1	2400
	21st to end	Day	48% 8% 11% 22% 10% 1	2113
October	1st to 10th	Day	41% 6% 14% 26% 13%	3260
	11th to 20th	Day	47% 6% 15% 20% 12%	3240
	21st to end	Day	47% 7% 15% 23% 7% 1	3452
November	1st to 10th	Day	52% 8% 12% 17% 9% 1	1851
	11th to 20th	Day	58% 7% 13% 14% 7% 1	1727
	21st to end	Day	63% 9% 14% 13% 2	1680
December	1st to 10th	Day	75% 6% 11% 7% 1	2680
	11th to 20th	Day	68% 7% 10% 9% 6%	3066
	21st to end	Day	73% 6% 12% 8% 2	4048
January	1st to 10th	Night	78% 6% 7% 6% 3	8234
	11th to 20th	Night	76% 5% 7% 7% 5%	8220
	21st to end	Night	70% 5% 8% 9% 7%	8401
February	1st to 10th	Night	67% 7% 10% 11% 6%	2730
	11th to 20th	Night	67% 7% 10% 12% 4	2661
	21st to end	Night	65% 6% 10% 12% 7%	2076
March	1st to 10th	Night	60% 5% 13% 15% 7%	5288
	11th to 20th	Night	53% 7% 16% 15% 6% 3	5090
	21st to end	Night	59% 5% 7% 19% 9% 1	5402
April	1st to 10th	Night	57% 7% 10% 17% 8% 1	2100
	11th to 20th	Night	53% 6% 10% 16% 14% 1	2075
	21st to end	Night	47% 7% 10% 19% 13% 3	2047
May	1st to 10th	Night	60% 6% 8% 14% 10% 2	4890
	11th to 20th	Night	47% 8% 11% 22% 11% 1	4640
	21st to end	Night	48% 6% 12% 19% 13% 2	5115
June	1st to 10th	Night	44% 7% 11% 22% 15% 1	1680
	11th to 20th	Night	40% 8% 14% 21% 15% 2	1640
	21st to end	Night	40% 9% 11% 25% 15% 1	1600
July	1st to 10th	Night	41% 7% 15% 21% 15% 2	3560
	11th to 20th	Night	37% 7% 14% 26% 14% 1	3552
	21st to end	Night	35% 7% 12% 28% 18% 1	3869
August	1st to 10th	Night	41% 8% 14% 25% 11% 1	2904
	11th to 20th	Night	43% 8% 13% 26% 9%	2930
	21st to end	Night	35% 7% 14% 32% 11% 1	3586
September	1st to 10th	Night	39% 7% 13% 26% 13% 2	2000
	11th to 20th	Night	36% 6% 13% 29% 16% 1	2000
	21st to end	Night	45% 8% 12% 22% 12% 1	2283
October	1st to 10th	Night	50% 6% 9% 24% 11%	3920
	11th to 20th	Night	48% 6% 12% 19% 14% 1	3899
	21st to end	Night	48% 6% 13% 25% 7% 1	4338
November	1st to 10th	Night	53% 7% 11% 19% 9% 2	2667
	11th to 20th	Night	55% 8% 13% 16% 7% 2	2890
	21st to end	Night	63% 7% 13% 14% 3	2940
December	1st to 10th	Night	74% 7% 10% 8% 1	4720
	11th to 20th	Night	68% 5% 8% 12% 6%	5348
	21st to end	Night	71% 7% 8% 10% 4	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	32% 22% 32% 10% 5%	220
	11th to 20th	Day	32% 26% 28% 13% 1	231
	21st to end	Day	28% 22% 35% 13% 2 1	363
February	1st to 10th	Day	31% 25% 33% 9% 1	330
	11th to 20th	Day	33% 25% 36% 5%	332
	21st to end	Day	35% 19% 33% 12% 1	446
March	1st to 10th	Day	26% 23% 30% 18% 2 1	540
	11th to 20th	Day	32% 22% 27% 14% 4	540
	21st to end	Day	32% 21% 28% 13% 5% 1	594
April	1st to 10th	Day	33% 19% 27% 14% 7%	540
	11th to 20th	Day	28% 23% 26% 13% 8% 3	532
	21st to end	Day	30% 17% 28% 16% 7% 1	540
May	1st to 10th	Day	26% 15% 32% 18% 7% 2	543
	11th to 20th	Day	21% 14% 29% 24% 10% 2	567
	21st to end	Day	20% 12% 31% 22% 12% 3	617
June	1st to 10th	Day	20% 12% 28% 24% 14% 2	570
	11th to 20th	Day	17% 12% 31% 25% 13% 1	550
	21st to end	Day	16% 12% 36% 26% 8% 3	530
July	1st to 10th	Day	11% 9% 27% 32% 16% 5%	525
	11th to 20th	Day	12% 10% 25% 30% 20% 4	524
	21st to end	Day	12% 6% 35% 31% 13% 3	576
August	1st to 10th	Day	13% 6% 25% 31% 19% 6%	526
	11th to 20th	Day	16% 6% 29% 25% 16% 8%	519
	21st to end	Day	13% 9% 29% 24% 17% 8%	583
September	1st to 10th	Day	18% 12% 20% 26% 16% 9%	530
	11th to 20th	Day	11% 9% 22% 23% 23% 11%	530
	21st to end	Day	19% 14% 26% 22% 15% 5%	530
October	1st to 10th	Day	22% 12% 26% 21% 15% 5%	530
	11th to 20th	Day	25% 18% 30% 17% 8% 2	530
	21st to end	Day	32% 17% 30% 18% 4	555
November	1st to 10th	Day	26% 21% 27% 19% 7% 1	425
	11th to 20th	Day	29% 25% 28% 14% 2 1	267
	21st to end	Day	37% 24% 28% 11%	220
December	1st to 10th	Day	31% 25% 32% 8% 4	220
	11th to 20th	Day	31% 27% 30% 10% 1	220
	21st to end	Day	33% 21% 36% 9% 2	242
January	1st to 10th	Night	29% 24% 30% 15% 3	840
	11th to 20th	Night	29% 23% 28% 16% 3 1	840
	21st to end	Night	22% 23% 34% 18% 3	924
February	1st to 10th	Night	26% 22% 31% 19% 2	840
	11th to 20th	Night	26% 23% 34% 15% 2	823
	21st to end	Night	28% 19% 33% 17% 3	692
March	1st to 10th	Night	27% 18% 30% 21% 3	840
	11th to 20th	Night	27% 22% 26% 22% 3	840
	21st to end	Night	28% 16% 29% 20% 7% 1	924
April	1st to 10th	Night	28% 15% 31% 22% 3	840
	11th to 20th	Night	26% 16% 27% 23% 7% 1	831
	21st to end	Night	23% 13% 29% 27% 8%	787
May	1st to 10th	Night	27% 8% 23% 31% 9% 1	501
	11th to 20th	Night	17% 8% 28% 37% 9% 1	414
	21st to end	Night	15% 7% 27% 35% 15%	455
June	1st to 10th	Night	18% 7% 22% 37% 15% 1	420
	11th to 20th	Night	15% 8% 24% 38% 15%	410
	21st to end	Night	15% 6% 26% 43% 10% 1	400
July	1st to 10th	Night	9% 4 20% 45% 19% 2	390
	11th to 20th	Night	11% 4 19% 44% 22% 1	388
	21st to end	Night	11% 5% 22% 46% 14% 1	462
August	1st to 10th	Night	12% 3 23% 37% 23% 2	597
	11th to 20th	Night	14% 4 15% 38% 25% 3	609
	21st to end	Night	13% 6% 21% 37% 22% 2	880
September	1st to 10th	Night	16% 6% 23% 34% 18% 3	800
	11th to 20th	Night	16% 5% 18% 31% 25% 6%	800
	21st to end	Night	20% 10% 23% 26% 18% 3	800
October	1st to 10th	Night	23% 9% 27% 20% 19% 2	800
	11th to 20th	Night	25% 14% 30% 24% 7% 1	800
	21st to end	Night	32% 15% 29% 21% 4	880
November	1st to 10th	Night	28% 14% 30% 21% 6%	820
	11th to 20th	Night	26% 20% 31% 17% 5% 2	840
	21st to end	Night	29% 21% 27% 18% 5%	840
December	1st to 10th	Night	32% 22% 27% 16% 3	840
	11th to 20th	Night	28% 23% 29% 17% 3	840
	21st to end	Night	35% 21% 28% 15% 2	924

Page generated at 2026-06-13 02:31:44. Version ac07

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