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 2025-01-22.

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% 5% 5% 5% 4 6% 7% 32%	105180
	Night	16% 10% 3 8% 5% 5% 4 4 5% 6% 33%	104205
Transparency	Day	51% 4 11% 22% 11% 1	108665
	Night	51% 4 12% 21% 11% 1	108796
Seeing	Day	22% 16% 30% 20% 9% 3	14897
	Night	21% 13% 27% 28% 10% 1	24036

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	11% 14% 5% 12% 7% 6% 5% 4 5% 5% 26%	2597
	11th to 20th	Day	12% 14% 5% 17% 9% 5% 4 4 4 5% 20%	2600
	21st to end	Day	13% 15% 6% 12% 7% 7% 5% 4 5% 6% 21%	2809
February	1st to 10th	Day	11% 12% 5% 10% 8% 7% 5% 4 7% 6% 25%	1710
	11th to 20th	Day	9% 12% 5% 10% 7% 6% 5% 4 7% 7% 28%	1796
	21st to end	Day	16% 12% 4 9% 6% 6% 5% 3 5% 6% 28%	1570
March	1st to 10th	Day	19% 17% 5% 11% 5% 5% 4 3 4 5% 23%	3116
	11th to 20th	Day	12% 14% 5% 10% 6% 6% 5% 5% 6% 6% 27%	3284
	21st to end	Day	16% 12% 3 8% 5% 4 4 3 4 5% 36%	4161
April	1st to 10th	Day	20% 12% 2 7% 5% 4 4 3 4 6% 33%	2280
	11th to 20th	Day	18% 10% 3 7% 5% 4 5% 3 5% 5% 35%	2254
	21st to end	Day	22% 9% 3 8% 5% 5% 5% 3 5% 5% 29%	2394
May	1st to 10th	Day	22% 11% 3 8% 5% 5% 4 3 4 6% 28%	4259
	11th to 20th	Day	17% 9% 3 8% 6% 5% 5% 4 5% 7% 30%	4398
	21st to end	Day	14% 5% 2 7% 5% 5% 5% 5% 6% 8% 38%	4837
June	1st to 10th	Day	18% 6% 3 8% 6% 6% 5% 5% 7% 8% 28%	2660
	11th to 20th	Day	16% 7% 3 6% 6% 6% 5% 5% 6% 8% 34%	2660
	21st to end	Day	19% 7% 3 7% 5% 5% 5% 5% 8% 7% 30%	2660
July	1st to 10th	Day	12% 5% 2 6% 6% 5% 6% 5% 7% 9% 37%	4440
	11th to 20th	Day	12% 6% 2 5% 5% 5% 6% 5% 7% 10% 38%	4440
	21st to end	Day	15% 5% 2 6% 5% 6% 6% 5% 7% 8% 36%	4814
August	1st to 10th	Day	16% 5% 2 7% 5% 5% 6% 5% 6% 8% 35%	4423
	11th to 20th	Day	16% 5% 2 7% 6% 6% 6% 5% 7% 9% 29%	3829
	21st to end	Day	15% 5% 2 6% 4 4 5% 5% 7% 8% 38%	4180
September	1st to 10th	Day	13% 5% 2 5% 5% 4 5% 4 6% 8% 42%	2280
	11th to 20th	Day	14% 6% 2 5% 3 4 4 3 6% 7% 46%	2195
	21st to end	Day	19% 5% 3 6% 3 4 4 4 7% 8% 38%	2090
October	1st to 10th	Day	23% 8% 3 7% 5% 5% 3 4 5% 5% 33%	1975
	11th to 20th	Day	17% 9% 3 7% 4 4 4 4 6% 6% 36%	1887
	21st to end	Day	22% 11% 3 8% 6% 4 4 3 5% 6% 28%	1881
November	1st to 10th	Day	13% 9% 3 8% 5% 6% 4 4 6% 7% 35%	1761
	11th to 20th	Day	14% 9% 3 8% 6% 6% 6% 4 5% 5% 34%	1794
	21st to end	Day	18% 11% 5% 9% 5% 5% 5% 4 6% 6% 28%	1600
December	1st to 10th	Day	16% 18% 6% 11% 7% 5% 5% 3 4 5% 19%	2600
	11th to 20th	Day	18% 14% 5% 9% 5% 5% 4 4 5% 6% 26%	2986
	21st to end	Day	18% 15% 4 9% 6% 5% 4 3 4 5% 27%	3960
January	1st to 10th	Night	14% 12% 4 10% 7% 6% 5% 3 5% 6% 28%	4569
	11th to 20th	Night	10% 13% 5% 18% 10% 6% 5% 4 5% 6% 19%	4580
	21st to end	Night	16% 14% 5% 11% 6% 4 4 4 5% 5% 25%	4867
February	1st to 10th	Night	11% 12% 5% 12% 7% 6% 5% 5% 6% 6% 25%	2470
	11th to 20th	Night	9% 11% 4 9% 8% 6% 6% 4 6% 7% 31%	2270
	21st to end	Night	14% 11% 4 10% 5% 4 5% 3 6% 7% 31%	1884
March	1st to 10th	Night	22% 13% 2 6% 5% 4 5% 4 5% 5% 27%	3724
	11th to 20th	Night	13% 12% 4 10% 6% 5% 5% 4 5% 5% 32%	3671
	21st to end	Night	15% 10% 3 10% 6% 4 4 3 4 4 36%	3471
April	1st to 10th	Night	18% 9% 3 7% 5% 4 4 4 5% 6% 34%	1900
	11th to 20th	Night	18% 10% 3 7% 5% 4 4 4 6% 7% 33%	1875
	21st to end	Night	20% 8% 3 7% 4 3 4 4 5% 5% 35%	1786
May	1st to 10th	Night	25% 10% 3 7% 5% 4 5% 4 6% 6% 26%	2710
	11th to 20th	Night	20% 11% 4 9% 5% 4 3 3 4 5% 31%	2495
	21st to end	Night	14% 6% 2 6% 5% 4 5% 4 7% 8% 38%	2738
June	1st to 10th	Night	18% 6% 2 6% 4 4 5% 4 5% 8% 38%	1520
	11th to 20th	Night	18% 6% 2 5% 4 4 4 4 5% 8% 40%	1520
	21st to end	Night	17% 6% 2 6% 4 5% 5% 4 6% 7% 37%	1520
July	1st to 10th	Night	12% 6% 2 7% 5% 6% 5% 5% 5% 7% 39%	2520
	11th to 20th	Night	14% 5% 1 5% 4 4 4 4 6% 8% 45%	2520
	21st to end	Night	12% 7% 2 5% 4 4 5% 4 6% 7% 43%	2739
August	1st to 10th	Night	18% 7% 2 6% 5% 4 4 4 5% 5% 39%	2506
	11th to 20th	Night	16% 6% 2 6% 5% 4 4 3 6% 7% 40%	2963
	21st to end	Night	10% 4 2 5% 5% 4 5% 5% 6% 9% 46%	3476
September	1st to 10th	Night	12% 5% 2 5% 5% 4 3 4 6% 8% 46%	1900
	11th to 20th	Night	14% 5% 2 5% 2 4 4 4 4 6% 51%	1985
	21st to end	Night	17% 6% 1 6% 3 4 4 4 6% 6% 44%	2090
October	1st to 10th	Night	19% 8% 3 8% 6% 5% 4 3 5% 6% 34%	2202
	11th to 20th	Night	16% 6% 3 7% 5% 5% 6% 3 6% 6% 37%	2291
	21st to end	Night	21% 9% 3 7% 5% 4 5% 4 5% 7% 30%	2717
November	1st to 10th	Night	13% 9% 3 7% 5% 5% 5% 4 6% 6% 37%	2537
	11th to 20th	Night	17% 9% 3 8% 5% 5% 4 3 5% 6% 36%	2605
	21st to end	Night	15% 11% 3 8% 5% 5% 5% 4 6% 7% 30%	2800
December	1st to 10th	Night	14% 14% 5% 12% 5% 5% 5% 4 7% 7% 20%	4580
	11th to 20th	Night	21% 15% 4 9% 5% 4 4 3 4 4 27%	5208
	21st to end	Night	19% 15% 5% 10% 5% 5% 3 3 4 5% 27%	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	60% 2 9% 22% 6% 1	2598
	11th to 20th	Day	67% 3 7% 15% 6% 1	2600
	21st to end	Day	65% 2 12% 14% 7% 1	2809
February	1st to 10th	Day	58% 5% 11% 19% 6% 2	1710
	11th to 20th	Day	56% 4 10% 17% 12% 2	1805
	21st to end	Day	58% 3 10% 16% 11% 2	1570
March	1st to 10th	Day	65% 2 8% 13% 10% 2	3119
	11th to 20th	Day	58% 2 12% 16% 10% 2	3284
	21st to end	Day	53% 2 5% 16% 21% 3	4161
April	1st to 10th	Day	53% 3 9% 20% 12% 3	2280
	11th to 20th	Day	51% 4 8% 20% 16% 2	2254
	21st to end	Day	57% 3 9% 17% 11% 3	2394
May	1st to 10th	Day	59% 2 7% 20% 11% 1	4273
	11th to 20th	Day	54% 2 13% 21% 9% 1	4402
	21st to end	Day	43% 3 11% 29% 12% 1	4837
June	1st to 10th	Day	52% 5% 12% 20% 10% 1	2660
	11th to 20th	Day	47% 5% 12% 22% 13% 2	2660
	21st to end	Day	50% 5% 13% 20% 11% 1	2660
July	1st to 10th	Day	42% 6% 15% 24% 13%	4370
	11th to 20th	Day	39% 6% 15% 31% 9%	4365
	21st to end	Day	44% 6% 13% 25% 11%	4661
August	1st to 10th	Day	46% 5% 16% 22% 11%	4409
	11th to 20th	Day	48% 7% 16% 24% 6%	3868
	21st to end	Day	40% 6% 15% 27% 11% 1	4180
September	1st to 10th	Day	39% 6% 10% 32% 13% 1	2280
	11th to 20th	Day	37% 4 10% 31% 18% 1	2195
	21st to end	Day	42% 4 14% 24% 13% 2	2090
October	1st to 10th	Day	47% 4 9% 26% 13% 1	3274
	11th to 20th	Day	43% 3 13% 25% 14% 2	3115
	21st to end	Day	43% 4 12% 31% 9% 1	3081
November	1st to 10th	Day	47% 5% 14% 21% 12%	1761
	11th to 20th	Day	50% 4 10% 18% 15% 3	1794
	21st to end	Day	56% 4 14% 18% 7% 1	1600
December	1st to 10th	Day	66% 5% 9% 16% 3	2600
	11th to 20th	Day	58% 3 11% 17% 10%	2986
	21st to end	Day	61% 3 7% 16% 13% 1	3960
January	1st to 10th	Night	57% 3 14% 18% 8%	4569
	11th to 20th	Night	67% 3 9% 12% 8% 1	4580
	21st to end	Night	63% 2 8% 17% 8% 1	4867
February	1st to 10th	Night	58% 5% 11% 17% 8% 1	2470
	11th to 20th	Night	53% 4 10% 20% 13% 1	2272
	21st to end	Night	53% 2 11% 21% 10% 2	1884
March	1st to 10th	Night	60% 2 8% 18% 11% 1	3734
	11th to 20th	Night	55% 2 11% 19% 11% 2	3672
	21st to end	Night	53% 3 5% 18% 18% 3	3471
April	1st to 10th	Night	52% 4 8% 22% 13% 2	1900
	11th to 20th	Night	51% 3 10% 21% 13% 1	1875
	21st to end	Night	50% 4 9% 20% 14% 3	1786
May	1st to 10th	Night	59% 2 9% 17% 11% 1	2716
	11th to 20th	Night	57% 3 11% 19% 10% 1	2496
	21st to end	Night	44% 3 14% 23% 15% 2	2739
June	1st to 10th	Night	46% 4 15% 22% 12% 1	1520
	11th to 20th	Night	43% 4 16% 22% 13% 2	1520
	21st to end	Night	46% 5% 13% 25% 10% 1	1520
July	1st to 10th	Night	42% 6% 15% 23% 13% 1	2480
	11th to 20th	Night	38% 6% 16% 28% 12%	2472
	21st to end	Night	38% 7% 14% 29% 11% 1	2651
August	1st to 10th	Night	46% 6% 15% 23% 10%	2496
	11th to 20th	Night	43% 5% 17% 27% 8%	2990
	21st to end	Night	32% 7% 18% 31% 11% 1	3476
September	1st to 10th	Night	36% 6% 14% 31% 12% 1	1900
	11th to 20th	Night	35% 3 12% 32% 18% 1	1985
	21st to end	Night	40% 4 14% 28% 13% 2	2090
October	1st to 10th	Night	49% 4 10% 24% 11%	3670
	11th to 20th	Night	41% 3 12% 26% 14% 3	3802
	21st to end	Night	46% 4 13% 28% 8% 1	4467
November	1st to 10th	Night	47% 4 13% 22% 12% 2	2537
	11th to 20th	Night	49% 3 11% 21% 13% 3	2605
	21st to end	Night	53% 5% 15% 19% 8% 1	2800
December	1st to 10th	Night	61% 6% 13% 17% 3	4580
	11th to 20th	Night	61% 3 8% 15% 13% 1	5208
	21st to end	Night	62% 3 8% 15% 11% 2	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	22% 20% 33% 19% 7%	200
	11th to 20th	Day	25% 26% 33% 13% 2 1	200
	21st to end	Day	17% 23% 38% 18% 5%	208
February	1st to 10th	Day	27% 37% 25% 9% 1	270
	11th to 20th	Day	23% 31% 32% 12% 2	404
	21st to end	Day	30% 18% 33% 16% 3	382
March	1st to 10th	Day	25% 20% 33% 18% 4	460
	11th to 20th	Day	29% 22% 30% 14% 4 1	460
	21st to end	Day	30% 24% 22% 15% 8% 1	506
April	1st to 10th	Day	34% 17% 28% 14% 6%	460
	11th to 20th	Day	31% 21% 24% 14% 7% 3	452
	21st to end	Day	33% 16% 32% 11% 6% 2	460
May	1st to 10th	Day	29% 18% 29% 13% 7% 3	463
	11th to 20th	Day	20% 16% 32% 23% 6% 2	487
	21st to end	Day	19% 14% 33% 23% 10% 2	529
June	1st to 10th	Day	23% 15% 31% 20% 9% 2	490
	11th to 20th	Day	17% 14% 37% 22% 9% 1	490
	21st to end	Day	22% 13% 34% 20% 8% 2	490
July	1st to 10th	Day	14% 9% 29% 32% 13% 3	485
	11th to 20th	Day	16% 8% 34% 27% 13% 2	484
	21st to end	Day	14% 9% 34% 30% 10% 2	532
August	1st to 10th	Day	12% 10% 29% 29% 14% 6%	486
	11th to 20th	Day	16% 7% 28% 26% 15% 7%	479
	21st to end	Day	13% 13% 28% 25% 15% 6%	539
September	1st to 10th	Day	16% 9% 28% 26% 13% 8%	490
	11th to 20th	Day	13% 11% 24% 23% 16% 12%	490
	21st to end	Day	21% 9% 29% 23% 11% 7%	490
October	1st to 10th	Day	26% 14% 25% 17% 13% 5%	490
	11th to 20th	Day	21% 18% 26% 24% 10% 1	483
	21st to end	Day	29% 14% 28% 22% 6%	429
November	1st to 10th	Day	23% 19% 24% 23% 10% 1	395
	11th to 20th	Day	23% 21% 28% 19% 7% 1	394
	21st to end	Day	27% 23% 33% 15% 4	200
December	1st to 10th	Day	26% 25% 26% 18% 4 1	200
	11th to 20th	Day	29% 27% 31% 13% 2	200
	21st to end	Day	28% 21% 30% 16% 5%	220
January	1st to 10th	Night	22% 19% 33% 24% 3	800
	11th to 20th	Night	22% 18% 32% 24% 4	800
	21st to end	Night	16% 20% 34% 25% 5%	841
February	1st to 10th	Night	19% 18% 37% 23% 2	760
	11th to 20th	Night	18% 21% 36% 22% 3	743
	21st to end	Night	23% 19% 34% 21% 3	628
March	1st to 10th	Night	22% 17% 33% 25% 3	760
	11th to 20th	Night	25% 18% 28% 24% 5%	760
	21st to end	Night	23% 16% 28% 25% 7% 1	836
April	1st to 10th	Night	25% 14% 30% 26% 5%	760
	11th to 20th	Night	24% 20% 27% 21% 7% 1	751
	21st to end	Night	27% 14% 28% 23% 8%	646
May	1st to 10th	Night	30% 12% 25% 22% 10%	498
	11th to 20th	Night	19% 13% 27% 31% 9% 1	374
	21st to end	Night	17% 9% 25% 36% 14% 1	411
June	1st to 10th	Night	22% 6% 27% 31% 14%	380
	11th to 20th	Night	17% 6% 24% 37% 15%	380
	21st to end	Night	19% 7% 26% 34% 13% 1	380
July	1st to 10th	Night	14% 4 20% 42% 19% 2	370
	11th to 20th	Night	12% 4 21% 41% 19% 2	368
	21st to end	Night	13% 5% 20% 44% 18% 1	416
August	1st to 10th	Night	12% 3 19% 42% 23% 1	378
	11th to 20th	Night	15% 4 18% 38% 22% 3	664
	21st to end	Night	15% 5% 19% 38% 21% 2	836
September	1st to 10th	Night	14% 6% 22% 38% 17% 3	760
	11th to 20th	Night	15% 8% 21% 30% 22% 5%	760
	21st to end	Night	18% 7% 26% 27% 18% 3	760
October	1st to 10th	Night	23% 12% 20% 27% 16% 2	760
	11th to 20th	Night	20% 12% 24% 32% 12% 1	760
	21st to end	Night	26% 12% 28% 27% 8%	836
November	1st to 10th	Night	20% 15% 29% 27% 8% 1	780
	11th to 20th	Night	23% 17% 27% 24% 7% 2	800
	21st to end	Night	22% 18% 29% 24% 6%	800
December	1st to 10th	Night	26% 17% 32% 21% 4	800
	11th to 20th	Night	26% 17% 28% 23% 6%	800
	21st to end	Night	26% 16% 32% 23% 3	880

Page generated at 2025-01-19 03:06:43. Version ac07

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