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 2025-02-21.

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%	108748
	Night	17% 13% 4 10% 5% 4 4 3 5% 6% 27%	109813
Transparency	Day	52% 7% 12% 19% 9% 1	112339
	Night	56% 7% 11% 17% 8% 1	114385
Seeing	Day	23% 15% 29% 20% 10% 3	14900
	Night	23% 14% 27% 25% 9% 1	24304

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	14% 16% 7% 24% 8% 4 5% 3 3 3 12%	3597
	11th to 20th	Day	14% 20% 8% 17% 9% 5% 4 3 4 4 12%	3615
	21st to end	Day	16% 15% 6% 14% 8% 7% 6% 3 4 5% 15%	4466
February	1st to 10th	Day	17% 15% 7% 14% 9% 6% 4 4 4 4 15%	1800
	11th to 20th	Day	14% 16% 8% 16% 7% 6% 5% 4 5% 5% 14%	1755
	21st to end	Day	20% 12% 4 13% 8% 5% 5% 5% 4 5% 19%	1570
March	1st to 10th	Day	20% 14% 5% 9% 5% 5% 4 3 4 5% 27%	3244
	11th to 20th	Day	11% 19% 5% 9% 5% 4 4 4 5% 6% 29%	3480
	21st to end	Day	17% 10% 5% 10% 6% 5% 5% 3 5% 6% 29%	3939
April	1st to 10th	Day	19% 13% 4 7% 6% 4 5% 3 4 6% 29%	2280
	11th to 20th	Day	20% 9% 3 6% 5% 4 4 4 5% 6% 35%	2254
	21st to end	Day	20% 12% 3 7% 4 4 4 3 5% 6% 32%	2344
May	1st to 10th	Day	21% 10% 2 7% 5% 4 4 3 4 6% 33%	4313
	11th to 20th	Day	16% 8% 3 8% 6% 5% 5% 4 6% 7% 32%	4398
	21st to end	Day	12% 6% 2 6% 4 4 4 4 6% 8% 42%	4837
June	1st to 10th	Day	16% 8% 3 6% 5% 4 5% 4 6% 8% 35%	2660
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 5% 7% 9% 38%	2660
	21st to end	Day	13% 6% 3 6% 5% 5% 6% 4 7% 9% 37%	2660
July	1st to 10th	Day	10% 5% 2 5% 5% 5% 5% 5% 7% 12% 38%	4440
	11th to 20th	Day	9% 6% 2 6% 5% 5% 6% 5% 8% 11% 37%	4440
	21st to end	Day	9% 5% 3 7% 5% 6% 7% 4 8% 9% 37%	4764
August	1st to 10th	Day	17% 6% 2 7% 4 5% 4 5% 6% 8% 35%	4104
	11th to 20th	Day	14% 7% 3 8% 6% 6% 5% 4 7% 8% 32%	3985
	21st to end	Day	12% 7% 3 7% 4 5% 5% 4 5% 7% 40%	4180
September	1st to 10th	Day	15% 7% 2 6% 4 5% 4 4 6% 8% 41%	2280
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 5% 7% 43%	2280
	21st to end	Day	16% 7% 3 8% 5% 5% 5% 4 5% 7% 34%	2008
October	1st to 10th	Day	16% 9% 3 7% 5% 4 5% 3 6% 7% 35%	1900
	11th to 20th	Day	20% 8% 4 7% 4 5% 5% 4 6% 6% 30%	1900
	21st to end	Day	23% 13% 3 8% 6% 4 4 4 5% 6% 24%	2043
November	1st to 10th	Day	14% 11% 3 8% 6% 5% 5% 3 5% 7% 31%	1761
	11th to 20th	Day	15% 14% 6% 10% 6% 5% 4 4 5% 6% 26%	1645
	21st to end	Day	21% 15% 4 9% 6% 4 4 5% 4 7% 21%	1600
December	1st to 10th	Day	20% 18% 7% 16% 7% 5% 4 3 5% 5% 11%	2600
	11th to 20th	Day	19% 16% 7% 15% 5% 4 4 3 4 5% 19%	2986
	21st to end	Day	22% 16% 5% 13% 8% 5% 5% 3 4 6% 14%	3960
January	1st to 10th	Night	15% 18% 7% 24% 7% 5% 4 3 3 4 11%	6349
	11th to 20th	Night	12% 21% 8% 18% 7% 5% 4 3 4 4 12%	6269
	21st to end	Night	18% 18% 8% 13% 7% 5% 5% 4 4 4 16%	6490
February	1st to 10th	Night	18% 16% 6% 12% 7% 5% 5% 4 5% 5% 19%	2600
	11th to 20th	Night	15% 16% 5% 14% 7% 6% 5% 4 4 5% 18%	2529
	21st to end	Night	19% 12% 5% 14% 6% 4 5% 4 5% 5% 22%	1885
March	1st to 10th	Night	19% 12% 4 9% 6% 4 4 3 4 6% 29%	3578
	11th to 20th	Night	18% 21% 4 9% 5% 4 4 3 4 5% 23%	3479
	21st to end	Night	20% 10% 5% 9% 4 4 4 3 5% 5% 30%	3691
April	1st to 10th	Night	20% 12% 4 7% 5% 4 5% 3 5% 6% 29%	1900
	11th to 20th	Night	20% 9% 2 7% 5% 4 4 3 5% 6% 34%	1875
	21st to end	Night	18% 9% 3 7% 5% 3 4 3 6% 7% 35%	1853
May	1st to 10th	Night	24% 9% 4 7% 5% 4 5% 4 4 6% 29%	2626
	11th to 20th	Night	17% 8% 3 8% 4 5% 4 3 6% 8% 34%	2495
	21st to end	Night	12% 6% 2 6% 5% 4 5% 5% 6% 7% 42%	2738
June	1st to 10th	Night	16% 6% 3 7% 4 5% 5% 4 7% 8% 36%	1520
	11th to 20th	Night	12% 7% 3 7% 4 5% 5% 4 7% 9% 39%	1520
	21st to end	Night	12% 7% 2 6% 4 5% 5% 5% 5% 7% 42%	1520
July	1st to 10th	Night	10% 7% 3 8% 5% 4 5% 4 6% 9% 39%	2520
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 4 6% 9% 45%	2520
	21st to end	Night	12% 6% 2 7% 4 4 5% 4 7% 8% 41%	2786
August	1st to 10th	Night	14% 7% 3 7% 4 4 4 4 6% 8% 39%	2825
	11th to 20th	Night	17% 6% 2 7% 5% 5% 4 4 6% 6% 38%	2812
	21st to end	Night	9% 6% 2 7% 4 4 5% 4 7% 8% 44%	3476
September	1st to 10th	Night	14% 6% 2 7% 4 4 5% 3 5% 8% 42%	1900
	11th to 20th	Night	15% 5% 2 6% 4 3 4 3 5% 7% 46%	1900
	21st to end	Night	17% 8% 3 6% 4 4 5% 4 6% 7% 36%	2169
October	1st to 10th	Night	19% 8% 3 8% 6% 4 4 4 5% 6% 33%	2280
	11th to 20th	Night	21% 9% 3 7% 4 4 4 3 5% 7% 32%	2280
	21st to end	Night	26% 11% 4 9% 5% 4 4 3 4 5% 25%	2555
November	1st to 10th	Night	16% 13% 4 7% 5% 4 4 3 5% 5% 34%	2537
	11th to 20th	Night	17% 13% 4 8% 5% 4 5% 3 5% 7% 28%	2752
	21st to end	Night	19% 18% 4 8% 5% 5% 5% 4 5% 7% 22%	2800
December	1st to 10th	Night	17% 21% 8% 13% 6% 5% 5% 3 5% 4 12%	4580
	11th to 20th	Night	21% 18% 6% 11% 6% 4 4 3 3 4 19%	5208
	21st to end	Night	25% 18% 4 10% 5% 5% 5% 3 5% 5% 15%	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	76% 6% 8% 7% 2	3598
	11th to 20th	Day	75% 6% 9% 6% 4 1	3645
	21st to end	Day	71% 6% 11% 9% 3	4466
February	1st to 10th	Day	72% 6% 9% 9% 3	1800
	11th to 20th	Day	72% 6% 7% 11% 2	1764
	21st to end	Day	67% 7% 9% 11% 5% 1	1570
March	1st to 10th	Day	60% 8% 9% 19% 4	3247
	11th to 20th	Day	55% 7% 16% 12% 8% 1	3480
	21st to end	Day	53% 8% 9% 22% 8% 1	3939
April	1st to 10th	Day	56% 6% 10% 17% 10% 1	2280
	11th to 20th	Day	50% 6% 11% 19% 13% 2	2254
	21st to end	Day	52% 6% 8% 18% 13% 2	2344
May	1st to 10th	Day	51% 7% 10% 18% 12% 1	4326
	11th to 20th	Day	49% 9% 12% 22% 7% 1	4402
	21st to end	Day	38% 8% 13% 25% 14% 2	4837
June	1st to 10th	Day	45% 9% 11% 19% 15% 1	2660
	11th to 20th	Day	41% 8% 14% 23% 13% 1	2660
	21st to end	Day	42% 10% 13% 21% 12% 1	2660
July	1st to 10th	Day	38% 8% 15% 27% 12% 1	4370
	11th to 20th	Day	36% 9% 17% 26% 12%	4365
	21st to end	Day	39% 10% 15% 23% 11% 1	4612
August	1st to 10th	Day	45% 8% 13% 20% 13% 1	4091
	11th to 20th	Day	46% 9% 16% 23% 6%	4024
	21st to end	Day	42% 6% 11% 32% 8% 1	4180
September	1st to 10th	Day	40% 8% 11% 27% 12% 1	2280
	11th to 20th	Day	39% 7% 12% 25% 16% 1	2280
	21st to end	Day	48% 8% 11% 22% 10% 1	2008
October	1st to 10th	Day	42% 6% 14% 25% 12%	3160
	11th to 20th	Day	46% 6% 15% 20% 12%	3140
	21st to end	Day	47% 7% 15% 23% 7% 1	3345
November	1st to 10th	Day	52% 8% 12% 17% 10% 1	1761
	11th to 20th	Day	57% 7% 13% 14% 7% 1	1645
	21st to end	Day	62% 9% 14% 13% 2	1600
December	1st to 10th	Day	76% 6% 11% 7% 1	2600
	11th to 20th	Day	68% 7% 10% 9% 6%	2986
	21st to end	Day	72% 6% 12% 8% 2	3960
January	1st to 10th	Night	78% 7% 7% 6% 2	6349
	11th to 20th	Night	74% 6% 8% 8% 4	6314
	21st to end	Night	71% 5% 8% 7% 8% 1	6490
February	1st to 10th	Night	66% 7% 10% 11% 6%	2600
	11th to 20th	Night	67% 8% 10% 11% 4 1	2531
	21st to end	Night	63% 7% 11% 12% 7%	1885
March	1st to 10th	Night	56% 6% 12% 19% 6%	3588
	11th to 20th	Night	60% 8% 11% 15% 5%	3480
	21st to end	Night	54% 6% 8% 21% 10% 1	3691
April	1st to 10th	Night	56% 7% 10% 18% 8% 2	1900
	11th to 20th	Night	53% 6% 10% 16% 14% 1	1875
	21st to end	Night	48% 7% 10% 18% 13% 3	1853
May	1st to 10th	Night	54% 8% 11% 15% 9% 4	2632
	11th to 20th	Night	46% 10% 14% 20% 8% 1	2496
	21st to end	Night	36% 10% 14% 19% 18% 2	2739
June	1st to 10th	Night	44% 7% 12% 21% 14% 1	1520
	11th to 20th	Night	40% 8% 14% 22% 15% 2	1520
	21st to end	Night	40% 9% 10% 25% 15% 1	1520
July	1st to 10th	Night	41% 7% 13% 21% 15% 3	2480
	11th to 20th	Night	35% 7% 15% 29% 13% 1	2472
	21st to end	Night	39% 8% 12% 24% 15% 2	2697
August	1st to 10th	Night	42% 8% 14% 26% 10% 1	2814
	11th to 20th	Night	44% 9% 14% 26% 8%	2839
	21st to end	Night	35% 7% 14% 32% 11% 1	3476
September	1st to 10th	Night	39% 7% 13% 25% 13% 2	1900
	11th to 20th	Night	37% 6% 13% 27% 16% 1	1900
	21st to end	Night	45% 8% 12% 22% 12% 1	2169
October	1st to 10th	Night	51% 6% 10% 23% 11%	3800
	11th to 20th	Night	48% 6% 12% 19% 15% 1	3779
	21st to end	Night	48% 6% 13% 26% 7% 1	4203
November	1st to 10th	Night	52% 7% 11% 19% 9% 2	2537
	11th to 20th	Night	54% 8% 13% 16% 7% 2	2752
	21st to end	Night	62% 7% 13% 14% 4	2800
December	1st to 10th	Night	75% 6% 10% 8% 1	4580
	11th to 20th	Night	68% 6% 8% 11% 6%	5208
	21st to end	Night	70% 8% 8% 10% 4	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	31% 21% 34% 10% 5%	200
	11th to 20th	Day	31% 25% 28% 14% 1	210
	21st to end	Day	26% 23% 36% 12% 2 1	330
February	1st to 10th	Day	31% 26% 34% 8% 1	300
	11th to 20th	Day	33% 25% 36% 5%	302
	21st to end	Day	34% 19% 32% 13% 2	382
March	1st to 10th	Day	24% 22% 31% 20% 3 1	460
	11th to 20th	Day	28% 23% 29% 16% 5%	460
	21st to end	Day	31% 21% 28% 14% 5% 2	506
April	1st to 10th	Day	31% 17% 28% 15% 8%	460
	11th to 20th	Day	28% 20% 25% 14% 9% 4	452
	21st to end	Day	31% 17% 27% 17% 8% 1	460
May	1st to 10th	Day	24% 14% 32% 19% 8% 3	463
	11th to 20th	Day	20% 12% 30% 25% 10% 2	487
	21st to end	Day	17% 11% 31% 24% 14% 4	529
June	1st to 10th	Day	21% 13% 27% 24% 12% 2	490
	11th to 20th	Day	15% 11% 30% 27% 15% 2	490
	21st to end	Day	16% 12% 35% 26% 9% 3	490
July	1st to 10th	Day	11% 9% 26% 33% 16% 5%	485
	11th to 20th	Day	12% 10% 25% 30% 21% 4	484
	21st to end	Day	12% 6% 35% 31% 14% 3	532
August	1st to 10th	Day	14% 7% 26% 29% 19% 6%	486
	11th to 20th	Day	16% 6% 30% 24% 16% 8%	479
	21st to end	Day	14% 9% 27% 24% 17% 9%	539
September	1st to 10th	Day	18% 11% 20% 26% 16% 9%	490
	11th to 20th	Day	12% 10% 23% 22% 22% 11%	490
	21st to end	Day	19% 14% 24% 22% 15% 5%	490
October	1st to 10th	Day	23% 12% 27% 19% 15% 4	490
	11th to 20th	Day	25% 17% 30% 18% 9% 2	490
	21st to end	Day	32% 17% 31% 17% 4	514
November	1st to 10th	Day	25% 19% 28% 20% 7% 1	395
	11th to 20th	Day	28% 25% 29% 15% 2 1	245
	21st to end	Day	36% 24% 28% 12% 1	200
December	1st to 10th	Day	31% 24% 33% 9% 4 1	200
	11th to 20th	Day	30% 26% 32% 11% 2	200
	21st to end	Day	30% 20% 37% 10% 2	220
January	1st to 10th	Night	29% 24% 30% 15% 3	800
	11th to 20th	Night	28% 23% 29% 17% 3 1	800
	21st to end	Night	22% 22% 34% 19% 3	880
February	1st to 10th	Night	28% 22% 31% 18% 2	800
	11th to 20th	Night	26% 23% 35% 15% 2	783
	21st to end	Night	28% 19% 33% 17% 3	629
March	1st to 10th	Night	27% 18% 29% 22% 4	760
	11th to 20th	Night	26% 21% 26% 23% 4	760
	21st to end	Night	27% 15% 29% 21% 7% 1	836
April	1st to 10th	Night	28% 14% 31% 23% 4	760
	11th to 20th	Night	25% 15% 28% 23% 7% 1	751
	21st to end	Night	23% 13% 28% 27% 8%	713
May	1st to 10th	Night	26% 8% 22% 33% 10% 1	453
	11th to 20th	Night	17% 7% 29% 36% 9% 1	374
	21st to end	Night	13% 7% 27% 35% 17%	411
June	1st to 10th	Night	17% 7% 23% 37% 16% 1	380
	11th to 20th	Night	14% 8% 23% 39% 16%	380
	21st to end	Night	15% 5% 27% 43% 9% 1	380
July	1st to 10th	Night	9% 4 19% 46% 20% 2	370
	11th to 20th	Night	11% 4 17% 45% 23% 1	368
	21st to end	Night	11% 5% 22% 45% 15% 1	439
August	1st to 10th	Night	12% 4 23% 36% 23% 2	567
	11th to 20th	Night	14% 4 16% 38% 25% 3	578
	21st to end	Night	12% 6% 21% 37% 22% 2	836
September	1st to 10th	Night	17% 6% 23% 33% 18% 3	760
	11th to 20th	Night	16% 5% 19% 30% 24% 6%	760
	21st to end	Night	19% 11% 23% 26% 18% 3	760
October	1st to 10th	Night	24% 9% 27% 20% 18% 2	760
	11th to 20th	Night	25% 14% 29% 24% 7% 1	760
	21st to end	Night	32% 15% 29% 21% 3	836
November	1st to 10th	Night	27% 14% 30% 22% 7%	780
	11th to 20th	Night	25% 20% 31% 17% 5% 2	800
	21st to end	Night	28% 20% 27% 19% 5%	800
December	1st to 10th	Night	32% 22% 27% 16% 3	800
	11th to 20th	Night	28% 22% 29% 18% 4	800
	21st to end	Night	34% 21% 28% 15% 2	880

Page generated at 2025-02-18 03:26:33. Version ac07

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