Schroon Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Schroon Lake clear sky chart from 2005-11-06 to 2026-05-17.

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% 9% 3 8% 6% 5% 5% 4 6% 7% 31%	131871
	Night	15% 10% 4 9% 5% 5% 5% 4 5% 6% 32%	130973
Transparency	Day	52% 4 11% 21% 11% 1	135338
	Night	52% 4 11% 20% 11% 1	135580
Seeing	Day	23% 17% 30% 20% 8% 3	16597
	Night	21% 14% 28% 27% 10% 1	25715

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	9% 13% 5% 17% 8% 6% 5% 4 5% 5% 23%	4661
	11th to 20th	Day	9% 17% 6% 15% 8% 6% 5% 4 4 5% 20%	4650
	21st to end	Day	9% 12% 5% 11% 8% 7% 6% 4 5% 6% 27%	5181
February	1st to 10th	Day	11% 12% 4 11% 8% 6% 5% 4 7% 6% 27%	1890
	11th to 20th	Day	10% 12% 5% 10% 8% 5% 5% 4 7% 7% 28%	1991
	21st to end	Day	15% 13% 4 9% 6% 6% 5% 3 5% 5% 28%	1730
March	1st to 10th	Day	17% 14% 5% 12% 5% 5% 4 3 4 5% 26%	4576
	11th to 20th	Day	14% 12% 4 8% 5% 5% 5% 4 5% 7% 31%	4804
	21st to end	Day	20% 12% 3 7% 5% 5% 4 4 4 4 32%	6097
April	1st to 10th	Day	19% 12% 3 7% 5% 4 5% 3 4 6% 32%	2520
	11th to 20th	Day	17% 11% 3 7% 5% 4 5% 3 5% 5% 35%	2494
	21st to end	Day	21% 9% 3 8% 5% 5% 4 3 5% 5% 31%	2646
May	1st to 10th	Day	32% 11% 3 7% 5% 4 4 3 4 5% 22%	6244
	11th to 20th	Day	18% 10% 3 9% 6% 5% 5% 3 5% 7% 29%	6402
	21st to end	Day	21% 7% 3 7% 5% 5% 5% 4 6% 7% 30%	6949
June	1st to 10th	Day	19% 6% 2 8% 6% 6% 5% 5% 7% 8% 29%	2800
	11th to 20th	Day	16% 7% 3 6% 6% 6% 5% 5% 6% 8% 33%	2800
	21st to end	Day	19% 7% 3 7% 5% 5% 5% 4 8% 8% 31%	2800
July	1st to 10th	Day	12% 5% 2 7% 6% 5% 6% 5% 7% 9% 35%	6360
	11th to 20th	Day	12% 5% 2 5% 5% 5% 6% 5% 6% 9% 39%	6360
	21st to end	Day	14% 5% 2 6% 4 5% 6% 4 7% 8% 40%	6926
August	1st to 10th	Day	15% 5% 2 7% 5% 5% 6% 5% 6% 8% 35%	4563
	11th to 20th	Day	16% 5% 2 7% 6% 6% 6% 5% 7% 9% 29%	3952
	21st to end	Day	15% 5% 2 6% 4 4 5% 5% 7% 9% 38%	4312
September	1st to 10th	Day	13% 5% 2 5% 4 4 5% 4 6% 8% 43%	2400
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 5% 7% 47%	2310
	21st to end	Day	19% 6% 2 5% 3 4 4 4 7% 8% 38%	2200
October	1st to 10th	Day	22% 8% 3 7% 5% 4 3 4 5% 5% 35%	2079
	11th to 20th	Day	17% 9% 3 7% 4 4 4 4 6% 6% 36%	1986
	21st to end	Day	21% 11% 3 8% 5% 4 4 3 5% 6% 29%	1980
November	1st to 10th	Day	14% 9% 3 8% 5% 6% 4 4 6% 7% 34%	1851
	11th to 20th	Day	14% 9% 3 8% 6% 5% 6% 4 6% 5% 33%	1883
	21st to end	Day	17% 11% 5% 9% 5% 5% 5% 4 6% 6% 28%	1680
December	1st to 10th	Day	16% 18% 6% 11% 7% 5% 5% 3 4 5% 19%	2680
	11th to 20th	Day	18% 14% 5% 9% 5% 5% 4 4 5% 6% 26%	3066
	21st to end	Day	18% 15% 4 10% 6% 4 4 3 4 5% 27%	4048
January	1st to 10th	Night	11% 13% 5% 14% 6% 5% 5% 4 5% 5% 26%	8234
	11th to 20th	Night	8% 15% 7% 17% 9% 7% 5% 4 5% 6% 17%	8235
	21st to end	Night	10% 10% 5% 10% 8% 7% 7% 5% 6% 8% 26%	8997
February	1st to 10th	Night	10% 11% 5% 13% 7% 6% 5% 5% 5% 6% 27%	2730
	11th to 20th	Night	9% 11% 4 10% 8% 6% 6% 5% 6% 7% 30%	2514
	21st to end	Night	13% 12% 5% 10% 5% 4 5% 3 6% 7% 30%	2076
March	1st to 10th	Night	20% 11% 3 8% 5% 5% 5% 4 6% 5% 27%	5484
	11th to 20th	Night	13% 11% 3 9% 5% 5% 5% 4 5% 6% 35%	5371
	21st to end	Night	19% 10% 3 10% 6% 4 4 3 4 5% 32%	5077
April	1st to 10th	Night	19% 9% 3 8% 5% 4 4 4 5% 5% 33%	2100
	11th to 20th	Night	18% 10% 3 7% 5% 4 4 4 5% 7% 33%	2075
	21st to end	Night	19% 8% 3 7% 4 3 4 4 5% 6% 37%	1974
May	1st to 10th	Night	31% 11% 3 7% 4 4 4 3 5% 5% 22%	3960
	11th to 20th	Night	18% 12% 3 9% 5% 4 4 3 5% 6% 30%	3623
	21st to end	Night	17% 8% 2 8% 6% 5% 5% 4 6% 7% 31%	3926
June	1st to 10th	Night	19% 6% 2 6% 4 4 4 4 5% 8% 39%	1600
	11th to 20th	Night	18% 6% 2 5% 4 4 4 4 5% 8% 40%	1600
	21st to end	Night	17% 6% 2 6% 4 5% 5% 4 7% 7% 38%	1600
July	1st to 10th	Night	11% 5% 2 7% 5% 6% 5% 5% 6% 8% 40%	3600
	11th to 20th	Night	14% 6% 2 7% 5% 5% 4 4 5% 8% 41%	3600
	21st to end	Night	10% 6% 2 5% 4 4 4 4 5% 7% 50%	3926
August	1st to 10th	Night	17% 7% 2 6% 5% 4 4 4 5% 5% 40%	2586
	11th to 20th	Night	16% 6% 2 6% 5% 4 4 3 6% 7% 41%	3059
	21st to end	Night	10% 4 2 5% 5% 4 5% 5% 6% 9% 46%	3586
September	1st to 10th	Night	12% 5% 2 5% 5% 4 3 4 6% 8% 47%	2000
	11th to 20th	Night	13% 5% 2 5% 3 4 4 4 4 6% 51%	2090
	21st to end	Night	17% 6% 1 6% 3 4 4 4 6% 6% 44%	2200
October	1st to 10th	Night	18% 8% 2 8% 5% 5% 4 3 5% 6% 35%	2318
	11th to 20th	Night	16% 6% 2 7% 5% 5% 6% 3 6% 6% 38%	2412
	21st to end	Night	20% 9% 3 7% 5% 4 5% 4 5% 7% 30%	2860
November	1st to 10th	Night	14% 9% 3 7% 5% 5% 5% 4 6% 6% 37%	2667
	11th to 20th	Night	17% 9% 3 8% 5% 5% 5% 3 5% 6% 36%	2735
	21st to end	Night	15% 11% 3 8% 6% 5% 5% 4 6% 7% 30%	2940
December	1st to 10th	Night	14% 14% 5% 12% 5% 5% 6% 4 7% 7% 20%	4720
	11th to 20th	Night	21% 15% 4 9% 5% 4 4 3 4 4 27%	5348
	21st to end	Night	19% 15% 5% 10% 5% 5% 3 3 4 5% 27%	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	63% 3 10% 18% 5% 1	4662
	11th to 20th	Day	65% 4 7% 12% 10% 2	4680
	21st to end	Day	55% 5% 10% 18% 11% 2	5181
February	1st to 10th	Day	56% 4 11% 19% 8% 2	1890
	11th to 20th	Day	55% 4 10% 18% 11% 2	2000
	21st to end	Day	58% 4 9% 16% 12% 2	1730
March	1st to 10th	Day	61% 2 8% 13% 10% 6%	4579
	11th to 20th	Day	53% 2 15% 17% 9% 4	4804
	21st to end	Day	57% 2 5% 13% 19% 4	6097
April	1st to 10th	Day	54% 3 9% 19% 12% 3	2520
	11th to 20th	Day	51% 4 8% 19% 16% 2	2494
	21st to end	Day	55% 3 9% 18% 12% 3	2646
May	1st to 10th	Day	66% 3 6% 16% 8% 1	6255
	11th to 20th	Day	56% 3 13% 18% 9% 1	6406
	21st to end	Day	53% 5% 10% 23% 9% 1	6949
June	1st to 10th	Day	52% 5% 12% 20% 11% 1	2800
	11th to 20th	Day	47% 5% 12% 22% 13% 1	2800
	21st to end	Day	49% 5% 13% 20% 11% 1	2800
July	1st to 10th	Day	43% 7% 15% 22% 13%	6290
	11th to 20th	Day	39% 7% 14% 28% 12%	6285
	21st to end	Day	41% 6% 12% 32% 9%	6728
August	1st to 10th	Day	45% 5% 16% 22% 12%	4549
	11th to 20th	Day	47% 7% 15% 24% 6%	3991
	21st to end	Day	40% 6% 15% 27% 11% 1	4312
September	1st to 10th	Day	38% 5% 10% 33% 13% 1	2400
	11th to 20th	Day	36% 4 10% 31% 18% 1	2310
	21st to end	Day	43% 4 14% 24% 14% 2	2200
October	1st to 10th	Day	46% 4 9% 27% 14% 1	3378
	11th to 20th	Day	43% 3 13% 25% 14% 2	3214
	21st to end	Day	43% 4 12% 31% 9% 1	3180
November	1st to 10th	Day	48% 5% 14% 21% 13%	1851
	11th to 20th	Day	50% 4 10% 18% 14% 3	1883
	21st to end	Day	56% 4 14% 18% 7% 1	1680
December	1st to 10th	Day	65% 5% 9% 16% 4	2680
	11th to 20th	Day	58% 3 11% 17% 10%	3066
	21st to end	Day	62% 2 7% 16% 12% 1	4048
January	1st to 10th	Night	59% 3 13% 15% 9% 1	8234
	11th to 20th	Night	67% 4 8% 10% 9% 2	8280
	21st to end	Night	53% 5% 10% 16% 13% 2	8997
February	1st to 10th	Night	56% 5% 11% 18% 9% 1	2730
	11th to 20th	Night	53% 4 10% 20% 12% 1	2516
	21st to end	Night	54% 3 11% 21% 10% 2	2076
March	1st to 10th	Night	58% 3 9% 14% 13% 3	5494
	11th to 20th	Night	51% 2 15% 18% 10% 2	5372
	21st to end	Night	56% 3 5% 17% 16% 3	5077
April	1st to 10th	Night	52% 4 8% 20% 14% 2	2100
	11th to 20th	Night	52% 3 10% 20% 14% 1	2075
	21st to end	Night	49% 3 9% 21% 15% 3	1974
May	1st to 10th	Night	65% 3 8% 15% 8% 1	3966
	11th to 20th	Night	55% 4 11% 20% 9% 1	3624
	21st to end	Night	52% 4 12% 19% 11% 1	3927
June	1st to 10th	Night	46% 4 15% 21% 13% 1	1600
	11th to 20th	Night	43% 4 16% 22% 13% 2	1600
	21st to end	Night	45% 5% 13% 26% 10% 1	1600
July	1st to 10th	Night	41% 6% 17% 24% 12%	3560
	11th to 20th	Night	41% 6% 14% 25% 13%	3552
	21st to end	Night	33% 6% 14% 35% 11% 1	3809
August	1st to 10th	Night	45% 6% 15% 23% 11%	2576
	11th to 20th	Night	42% 5% 17% 27% 8%	3086
	21st to end	Night	33% 7% 18% 31% 11% 1	3586
September	1st to 10th	Night	36% 6% 14% 31% 12% 1	2000
	11th to 20th	Night	34% 3 12% 32% 18%	2090
	21st to end	Night	40% 4 13% 27% 14% 2	2200
October	1st to 10th	Night	48% 4 10% 25% 12% 1	3786
	11th to 20th	Night	40% 3 12% 26% 15% 3	3923
	21st to end	Night	46% 5% 13% 27% 8% 1	4610
November	1st to 10th	Night	48% 4 12% 22% 12% 2	2667
	11th to 20th	Night	50% 4 11% 21% 12% 3	2735
	21st to end	Night	53% 5% 14% 19% 8% 1	2940
December	1st to 10th	Night	61% 6% 13% 17% 4	4720
	11th to 20th	Night	61% 3 8% 15% 13% 1	5348
	21st to end	Night	62% 2 8% 15% 11% 2	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	21% 20% 34% 18% 7%	220
	11th to 20th	Day	26% 28% 31% 12% 2 1	220
	21st to end	Day	19% 26% 35% 15% 4	252
February	1st to 10th	Day	26% 35% 25% 12% 2	330
	11th to 20th	Day	25% 29% 32% 12% 2	479
	21st to end	Day	29% 21% 33% 15% 2	446
March	1st to 10th	Day	26% 22% 32% 17% 4	540
	11th to 20th	Day	32% 21% 29% 13% 4 1	540
	21st to end	Day	31% 25% 22% 13% 7% 1	594
April	1st to 10th	Day	36% 19% 27% 13% 6%	540
	11th to 20th	Day	32% 23% 24% 13% 6% 2	532
	21st to end	Day	31% 17% 33% 10% 6% 2	540
May	1st to 10th	Day	33% 19% 28% 11% 6% 3	543
	11th to 20th	Day	21% 17% 33% 22% 6% 2	551
	21st to end	Day	21% 14% 32% 23% 9% 2	573
June	1st to 10th	Day	23% 15% 32% 20% 8% 2	530
	11th to 20th	Day	17% 15% 36% 22% 8% 1	530
	21st to end	Day	21% 14% 35% 20% 8% 2	530
July	1st to 10th	Day	13% 11% 30% 31% 13% 3	525
	11th to 20th	Day	16% 8% 34% 28% 12% 2	524
	21st to end	Day	15% 9% 34% 29% 10% 3	576
August	1st to 10th	Day	11% 10% 28% 30% 14% 6%	526
	11th to 20th	Day	16% 8% 29% 26% 15% 7%	519
	21st to end	Day	12% 13% 30% 25% 15% 6%	583
September	1st to 10th	Day	15% 9% 28% 26% 13% 8%	530
	11th to 20th	Day	12% 11% 24% 25% 17% 12%	530
	21st to end	Day	21% 9% 30% 22% 11% 6%	530
October	1st to 10th	Day	24% 14% 25% 18% 14% 5%	530
	11th to 20th	Day	21% 18% 26% 24% 10% 1	522
	21st to end	Day	29% 13% 29% 22% 6%	462
November	1st to 10th	Day	26% 19% 24% 22% 9%	425
	11th to 20th	Day	23% 21% 28% 20% 7% 1	423
	21st to end	Day	26% 25% 31% 15% 3	220
December	1st to 10th	Day	26% 25% 28% 17% 4 1	220
	11th to 20th	Day	29% 27% 31% 11% 1	220
	21st to end	Day	29% 22% 30% 16% 4	242
January	1st to 10th	Night	22% 19% 33% 24% 3	840
	11th to 20th	Night	23% 19% 31% 23% 4	840
	21st to end	Night	16% 21% 33% 24% 6%	924
February	1st to 10th	Night	19% 17% 37% 25% 3	840
	11th to 20th	Night	18% 21% 37% 21% 3	823
	21st to end	Night	22% 19% 35% 21% 3	692
March	1st to 10th	Night	23% 18% 33% 23% 3	840
	11th to 20th	Night	25% 19% 28% 24% 4	840
	21st to end	Night	24% 17% 28% 24% 6% 1	924
April	1st to 10th	Night	27% 15% 29% 25% 4	840
	11th to 20th	Night	25% 20% 27% 20% 7%	831
	21st to end	Night	26% 14% 29% 23% 7%	714
May	1st to 10th	Night	30% 12% 26% 22% 9%	550
	11th to 20th	Night	19% 13% 28% 30% 9%	406
	21st to end	Night	17% 9% 25% 35% 13% 1	433
June	1st to 10th	Night	22% 6% 27% 31% 14%	400
	11th to 20th	Night	18% 7% 25% 37% 15%	400
	21st to end	Night	18% 7% 26% 34% 14% 1	400
July	1st to 10th	Night	14% 4 19% 43% 18% 2	390
	11th to 20th	Night	13% 4 21% 41% 19% 2	388
	21st to end	Night	12% 5% 20% 45% 17% 1	438
August	1st to 10th	Night	12% 3 19% 41% 24% 1	398
	11th to 20th	Night	15% 4 18% 38% 23% 3	700
	21st to end	Night	15% 5% 20% 38% 21% 2	880
September	1st to 10th	Night	14% 6% 22% 38% 17% 3	800
	11th to 20th	Night	15% 7% 20% 31% 23% 5%	800
	21st to end	Night	19% 7% 26% 28% 18% 3	800
October	1st to 10th	Night	23% 12% 20% 27% 17% 2	800
	11th to 20th	Night	20% 12% 24% 32% 11% 1	800
	21st to end	Night	26% 12% 27% 27% 8%	880
November	1st to 10th	Night	21% 15% 30% 26% 8%	820
	11th to 20th	Night	24% 17% 26% 24% 7% 2	840
	21st to end	Night	23% 18% 29% 24% 6%	840
December	1st to 10th	Night	25% 17% 32% 21% 4	840
	11th to 20th	Night	27% 18% 28% 22% 6%	840
	21st to end	Night	27% 16% 31% 22% 3	924

Page generated at 2026-05-14 01:58:55. Version ac07

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