Champlain Belvédère
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Champlain Belvédère clear sky chart from 2005-11-06 to 2025-07-21.

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	17% 11% 4 8% 5% 5% 4 4 5% 6% 31%	120408
	Night	17% 12% 4 9% 5% 5% 4 3 5% 6% 30%	118671
Transparency	Day	33% 40% 7% 13% 6% 1	123931
	Night	35% 39% 7% 12% 6% 1	123309
Seeing	Day	25% 15% 30% 19% 8% 2	15308
	Night	24% 12% 28% 26% 10% 1	24392

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% 18% 7% 16% 7% 5% 4 3 3 4 19%	3597
	11th to 20th	Day	12% 16% 7% 15% 7% 6% 5% 3 5% 5% 21%	3570
	21st to end	Day	10% 17% 8% 14% 6% 6% 4 3 4 6% 21%	4140
February	1st to 10th	Day	13% 16% 6% 13% 7% 4 4 4 5% 5% 23%	1800
	11th to 20th	Day	12% 17% 6% 11% 6% 5% 4 4 5% 5% 26%	1753
	21st to end	Day	20% 12% 4 10% 6% 5% 4 4 5% 5% 24%	1647
March	1st to 10th	Day	20% 16% 4 10% 5% 5% 4 3 4 5% 24%	4493
	11th to 20th	Day	13% 12% 5% 9% 6% 5% 5% 4 5% 7% 29%	4980
	21st to end	Day	18% 11% 3 7% 6% 4 3 3 4 5% 35%	5758
April	1st to 10th	Day	22% 13% 3 7% 4 4 3 3 4 6% 31%	2400
	11th to 20th	Day	23% 10% 3 7% 4 3 4 3 4 4 35%	2374
	21st to end	Day	22% 10% 4 7% 5% 4 4 3 4 4 31%	2548
May	1st to 10th	Day	23% 10% 3 8% 5% 5% 5% 4 5% 6% 26%	6346
	11th to 20th	Day	17% 8% 3 9% 6% 5% 5% 3 5% 7% 31%	6318
	21st to end	Day	22% 9% 3 7% 4 4 4 3 5% 7% 32%	6949
June	1st to 10th	Day	22% 9% 3 7% 5% 5% 5% 4 5% 6% 30%	2800
	11th to 20th	Day	14% 6% 2 6% 6% 5% 5% 5% 5% 7% 39%	2800
	21st to end	Day	19% 7% 2 6% 5% 6% 5% 4 8% 6% 32%	2800
July	1st to 10th	Day	12% 6% 2 8% 5% 5% 6% 5% 7% 9% 34%	4580
	11th to 20th	Day	14% 5% 2 6% 5% 5% 5% 4 6% 7% 40%	4580
	21st to end	Day	12% 6% 2 5% 4 4 4 4 6% 8% 46%	4814
August	1st to 10th	Day	14% 6% 3 8% 5% 6% 5% 4 6% 8% 36%	4345
	11th to 20th	Day	18% 6% 2 6% 4 4 4 4 7% 9% 37%	4012
	21st to end	Day	13% 5% 2 6% 4 4 5% 4 7% 9% 40%	4180
September	1st to 10th	Day	14% 6% 2 6% 5% 4 4 3 6% 7% 43%	2280
	11th to 20th	Day	13% 6% 2 5% 5% 4 4 3 5% 7% 47%	2280
	21st to end	Day	19% 6% 2 7% 4 3 4 3 6% 6% 40%	2024
October	1st to 10th	Day	21% 9% 3 7% 4 4 4 3 5% 6% 34%	1900
	11th to 20th	Day	23% 10% 3 7% 5% 5% 5% 3 5% 7% 28%	1900
	21st to end	Day	25% 10% 3 7% 5% 4 4 4 4 6% 27%	1938
November	1st to 10th	Day	15% 10% 3 8% 5% 5% 4 3 6% 8% 33%	1756
	11th to 20th	Day	19% 13% 3 7% 6% 4 6% 3 5% 6% 26%	1600
	21st to end	Day	22% 15% 4 10% 7% 5% 4 3 5% 5% 20%	1600
December	1st to 10th	Day	21% 21% 7% 10% 4 5% 4 4 5% 5% 13%	2600
	11th to 20th	Day	18% 17% 6% 11% 6% 4 4 3 4 3 25%	2986
	21st to end	Day	23% 18% 5% 11% 5% 4 4 2 3 5% 20%	3960
January	1st to 10th	Night	14% 23% 8% 13% 6% 4 3 3 4 4 19%	6349
	11th to 20th	Night	11% 16% 6% 15% 8% 6% 5% 3 4 5% 21%	6315
	21st to end	Night	11% 18% 6% 14% 7% 7% 5% 3 4 4 21%	6812
February	1st to 10th	Night	13% 15% 6% 12% 7% 5% 4 4 5% 5% 24%	2600
	11th to 20th	Night	13% 14% 6% 12% 7% 5% 4 3 4 5% 28%	2533
	21st to end	Night	16% 14% 4 9% 6% 4 5% 3 5% 5% 28%	1981
March	1st to 10th	Night	22% 15% 5% 9% 5% 4 4 3 3 4 28%	5346
	11th to 20th	Night	12% 13% 5% 9% 5% 5% 5% 4 6% 8% 28%	4979
	21st to end	Night	18% 11% 3 9% 5% 4 3 3 5% 6% 33%	5160
April	1st to 10th	Night	20% 11% 4 8% 5% 4 3 4 4 6% 32%	2000
	11th to 20th	Night	18% 9% 4 7% 5% 3 5% 3 4 5% 35%	1975
	21st to end	Night	21% 10% 3 7% 4 4 4 3 4 6% 34%	1867
May	1st to 10th	Night	22% 10% 3 8% 5% 5% 5% 4 6% 7% 25%	3594
	11th to 20th	Night	16% 7% 3 7% 5% 4 4 4 5% 6% 38%	3575
	21st to end	Night	20% 8% 3 7% 5% 5% 5% 4 5% 6% 31%	3926
June	1st to 10th	Night	16% 7% 2 7% 6% 5% 5% 5% 6% 8% 34%	1600
	11th to 20th	Night	14% 5% 2 6% 5% 4 4 3 7% 7% 43%	1600
	21st to end	Night	19% 7% 2 5% 5% 6% 4 4 5% 8% 35%	1600
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 6% 5% 6% 7% 35%	2600
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 6% 8% 42%	2600
	21st to end	Night	11% 5% 2 6% 4 5% 5% 4 7% 7% 45%	2739
August	1st to 10th	Night	13% 7% 2 7% 4 4 5% 4 6% 8% 39%	2568
	11th to 20th	Night	16% 7% 2 5% 4 3 4 4 6% 7% 41%	2785
	21st to end	Night	14% 5% 2 6% 5% 5% 4 4 6% 8% 41%	3476
September	1st to 10th	Night	12% 6% 2 6% 4 4 4 4 5% 6% 48%	1900
	11th to 20th	Night	15% 5% 2 5% 3 3 4 4 5% 5% 50%	1900
	21st to end	Night	19% 6% 2 6% 4 3 3 2 4 6% 44%	2150
October	1st to 10th	Night	19% 7% 2 6% 4 4 4 4 5% 6% 39%	2280
	11th to 20th	Night	21% 8% 2 7% 6% 5% 5% 3 5% 6% 31%	2280
	21st to end	Night	24% 9% 3 8% 5% 5% 5% 4 4 6% 28%	2659
November	1st to 10th	Night	19% 10% 3 7% 4 5% 4 4 5% 6% 32%	2538
	11th to 20th	Night	19% 11% 3 9% 5% 5% 5% 3 5% 5% 29%	2800
	21st to end	Night	21% 13% 5% 9% 6% 5% 5% 3 4 6% 23%	2800
December	1st to 10th	Night	19% 17% 5% 12% 6% 5% 5% 4 5% 6% 16%	4580
	11th to 20th	Night	24% 14% 5% 11% 6% 4 3 2 3 4 26%	5208
	21st to end	Night	25% 19% 4 10% 4 4 3 3 3 4 21%	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	50% 30% 6% 9% 4 1	3598
	11th to 20th	Day	49% 27% 9% 8% 6%	3600
	21st to end	Day	49% 30% 6% 9% 6% 1	4140
February	1st to 10th	Day	26% 61% 3 6% 3 1	1800
	11th to 20th	Day	24% 60% 3 7% 5%	1762
	21st to end	Day	23% 62% 4 4 6% 2	1647
March	1st to 10th	Day	47% 30% 5% 7% 9% 2	4496
	11th to 20th	Day	37% 30% 13% 11% 7% 1	4980
	21st to end	Day	38% 28% 5% 14% 14% 1	5758
April	1st to 10th	Day	22% 62% 3 6% 7% 1	2400
	11th to 20th	Day	21% 62% 2 9% 5% 1	2374
	21st to end	Day	22% 61% 3 7% 7%	2548
May	1st to 10th	Day	43% 31% 6% 14% 5% 1	6357
	11th to 20th	Day	38% 32% 10% 13% 7%	6322
	21st to end	Day	40% 30% 7% 15% 8%	6949
June	1st to 10th	Day	20% 62% 3 10% 5%	2800
	11th to 20th	Day	18% 62% 5% 9% 6% 1	2800
	21st to end	Day	18% 60% 4 12% 5% 1	2800
July	1st to 10th	Day	30% 36% 10% 16% 8%	4510
	11th to 20th	Day	26% 36% 9% 24% 4	4505
	21st to end	Day	22% 37% 9% 24% 8%	4661
August	1st to 10th	Day	30% 38% 11% 15% 6%	4331
	11th to 20th	Day	28% 38% 9% 20% 5%	4051
	21st to end	Day	24% 39% 11% 18% 7%	4180
September	1st to 10th	Day	16% 60% 8% 11% 5%	2280
	11th to 20th	Day	13% 60% 5% 15% 6% 1	2280
	21st to end	Day	15% 59% 7% 13% 7%	2024
October	1st to 10th	Day	30% 38% 8% 21% 3	3160
	11th to 20th	Day	26% 38% 10% 19% 7%	3140
	21st to end	Day	30% 38% 14% 14% 4	3176
November	1st to 10th	Day	27% 56% 6% 8% 2 1	1756
	11th to 20th	Day	24% 57% 4 10% 4 1	1600
	21st to end	Day	30% 57% 5% 3 4 1	1600
December	1st to 10th	Day	47% 36% 8% 8% 1	2600
	11th to 20th	Day	46% 32% 7% 10% 6%	2986
	21st to end	Day	51% 27% 4 13% 4	3960
January	1st to 10th	Night	52% 27% 8% 9% 3	6349
	11th to 20th	Night	48% 29% 9% 11% 3	6360
	21st to end	Night	52% 28% 5% 5% 9% 1	6812
February	1st to 10th	Night	23% 62% 3 8% 3	2600
	11th to 20th	Night	23% 60% 3 9% 5%	2535
	21st to end	Night	22% 61% 3 8% 6%	1981
March	1st to 10th	Night	45% 29% 4 10% 9% 3	5356
	11th to 20th	Night	37% 32% 12% 11% 6% 2	4980
	21st to end	Night	39% 28% 6% 15% 9% 2	5160
April	1st to 10th	Night	21% 62% 3 8% 6% 1	2000
	11th to 20th	Night	20% 62% 2 9% 7%	1975
	21st to end	Night	20% 61% 4 7% 7% 1	1867
May	1st to 10th	Night	43% 33% 6% 14% 4 1	3600
	11th to 20th	Night	34% 31% 10% 14% 9%	3576
	21st to end	Night	41% 30% 8% 12% 8%	3927
June	1st to 10th	Night	18% 62% 3 11% 6% 1	1600
	11th to 20th	Night	14% 62% 4 11% 8% 1	1600
	21st to end	Night	19% 60% 3 11% 7% 1	1600
July	1st to 10th	Night	34% 37% 9% 11% 9%	2560
	11th to 20th	Night	27% 36% 8% 23% 5%	2552
	21st to end	Night	23% 37% 10% 20% 10%	2651
August	1st to 10th	Night	28% 38% 9% 18% 6%	2558
	11th to 20th	Night	29% 39% 9% 20% 3	2812
	21st to end	Night	26% 39% 8% 16% 8% 2	3476
September	1st to 10th	Night	13% 60% 5% 16% 6%	1900
	11th to 20th	Night	14% 60% 5% 15% 5% 1	1900
	21st to end	Night	15% 59% 4 14% 7%	2150
October	1st to 10th	Night	22% 37% 10% 23% 8%	3800
	11th to 20th	Night	25% 37% 11% 20% 7%	3779
	21st to end	Night	30% 38% 12% 14% 6%	4371
November	1st to 10th	Night	25% 56% 6% 9% 3	2538
	11th to 20th	Night	25% 57% 5% 10% 4	2800
	21st to end	Night	27% 57% 5% 7% 4	2800
December	1st to 10th	Night	44% 37% 9% 9% 2	4580
	11th to 20th	Night	45% 31% 4 10% 9% 1	5208
	21st to end	Night	51% 26% 3 10% 9%	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	27% 18% 36% 17% 3	200
	11th to 20th	Day	30% 14% 40% 14% 2 2	200
	21st to end	Day	22% 19% 36% 18% 4	258
February	1st to 10th	Day	35% 22% 31% 9% 2	300
	11th to 20th	Day	31% 28% 35% 6% 1	300
	21st to end	Day	34% 20% 30% 14% 1	411
March	1st to 10th	Day	30% 18% 32% 14% 5%	500
	11th to 20th	Day	28% 21% 33% 14% 4 1	500
	21st to end	Day	32% 19% 30% 15% 4 1	550
April	1st to 10th	Day	34% 23% 25% 13% 5%	500
	11th to 20th	Day	36% 19% 22% 14% 8% 1	492
	21st to end	Day	33% 20% 29% 12% 5% 1	500
May	1st to 10th	Day	27% 16% 32% 16% 7% 2	503
	11th to 20th	Day	18% 18% 33% 20% 9% 2	527
	21st to end	Day	24% 13% 32% 20% 9% 2	573
June	1st to 10th	Day	27% 12% 32% 20% 8% 1	530
	11th to 20th	Day	19% 14% 31% 23% 10% 3	530
	21st to end	Day	25% 12% 32% 21% 8% 2	530
July	1st to 10th	Day	13% 8% 34% 30% 12% 3	525
	11th to 20th	Day	14% 10% 35% 26% 12% 3	524
	21st to end	Day	14% 6% 34% 30% 12% 4	532
August	1st to 10th	Day	16% 8% 27% 30% 15% 4	486
	11th to 20th	Day	18% 4 25% 31% 14% 8%	479
	21st to end	Day	15% 11% 29% 26% 12% 6%	539
September	1st to 10th	Day	18% 10% 29% 23% 13% 7%	490
	11th to 20th	Day	15% 9% 24% 21% 19% 11%	490
	21st to end	Day	20% 12% 28% 22% 13% 4	490
October	1st to 10th	Day	25% 14% 24% 23% 10% 3	490
	11th to 20th	Day	28% 17% 31% 17% 7% 1	490
	21st to end	Day	33% 14% 28% 21% 3	459
November	1st to 10th	Day	27% 16% 31% 18% 7% 1	390
	11th to 20th	Day	27% 28% 29% 13% 4 1	200
	21st to end	Day	30% 22% 33% 12% 3 2	200
December	1st to 10th	Day	36% 12% 36% 14% 3	200
	11th to 20th	Day	28% 25% 34% 11% 3	200
	21st to end	Day	33% 20% 32% 11% 3 1	220
January	1st to 10th	Night	28% 16% 32% 20% 4	800
	11th to 20th	Night	29% 16% 28% 21% 6% 1	800
	21st to end	Night	20% 14% 36% 25% 5%	880
February	1st to 10th	Night	22% 20% 31% 24% 3	800
	11th to 20th	Night	22% 18% 37% 18% 4	783
	21st to end	Night	25% 17% 30% 24% 4	660
March	1st to 10th	Night	26% 16% 33% 22% 5%	800
	11th to 20th	Night	25% 17% 33% 20% 5%	800
	21st to end	Night	26% 16% 29% 22% 7%	880
April	1st to 10th	Night	28% 16% 28% 24% 4	800
	11th to 20th	Night	25% 18% 28% 21% 7% 1	791
	21st to end	Night	27% 14% 28% 22% 8%	667
May	1st to 10th	Night	25% 9% 26% 30% 9% 2	400
	11th to 20th	Night	21% 10% 27% 31% 11%	394
	21st to end	Night	18% 7% 37% 27% 11%	433
June	1st to 10th	Night	21% 6% 28% 35% 11%	400
	11th to 20th	Night	17% 8% 25% 36% 14% 2	400
	21st to end	Night	22% 6% 24% 34% 15% 1	400
July	1st to 10th	Night	12% 3 28% 38% 18%	390
	11th to 20th	Night	14% 3 20% 46% 18% 1	388
	21st to end	Night	10% 3 24% 44% 18% 2	416
August	1st to 10th	Night	13% 5% 18% 41% 22% 1	414
	11th to 20th	Night	16% 3 15% 37% 25% 3	564
	21st to end	Night	15% 5% 23% 36% 19% 2	836
September	1st to 10th	Night	16% 6% 29% 29% 20% 1	760
	11th to 20th	Night	17% 6% 19% 30% 24% 3	760
	21st to end	Night	21% 7% 25% 26% 18% 2	760
October	1st to 10th	Night	23% 10% 24% 25% 16% 1	760
	11th to 20th	Night	27% 11% 27% 25% 9% 1	760
	21st to end	Night	29% 12% 29% 24% 5%	836
November	1st to 10th	Night	28% 12% 24% 26% 8% 1	780
	11th to 20th	Night	25% 16% 33% 16% 9% 1	800
	21st to end	Night	30% 18% 24% 22% 6%	800
December	1st to 10th	Night	31% 14% 31% 21% 4	800
	11th to 20th	Night	29% 17% 27% 21% 5% 1	800
	21st to end	Night	34% 14% 30% 17% 4	880

Page generated at 2025-07-18 01:09:57. Version ac07

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