Lac Georges
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Georges clear sky chart from 2005-11-06 to 2024-12-09.

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% 5% 4 4 4 5% 6% 32%	101878
	Night	16% 12% 4 9% 5% 4 4 3 5% 6% 31%	97918
Transparency	Day	53% 3 11% 22% 10% 1	105374
	Night	54% 3 11% 21% 9% 1	102511
Seeing	Day	24% 16% 31% 19% 8% 2	14498
	Night	23% 13% 30% 24% 9% 1	23634

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	15% 18% 7% 14% 8% 5% 4 3 3 3 19%	2517
	11th to 20th	Day	13% 13% 6% 17% 7% 6% 5% 3 5% 5% 20%	2520
	21st to end	Day	12% 18% 8% 16% 7% 5% 5% 3 4 4 18%	2900
February	1st to 10th	Day	12% 16% 5% 14% 7% 5% 5% 3 5% 5% 21%	1710
	11th to 20th	Day	11% 17% 6% 12% 5% 5% 4 3 5% 5% 26%	1663
	21st to end	Day	17% 15% 5% 11% 6% 5% 5% 3 4 5% 26%	1550
March	1st to 10th	Day	16% 18% 5% 10% 5% 5% 4 2 4 6% 26%	3144
	11th to 20th	Day	11% 18% 7% 11% 7% 4 4 3 4 5% 26%	3480
	21st to end	Day	11% 8% 3 8% 6% 4 4 3 5% 6% 41%	4001
April	1st to 10th	Day	21% 14% 3 8% 5% 4 3 3 4 6% 30%	2280
	11th to 20th	Day	22% 10% 3 7% 4 3 4 2 5% 5% 35%	2254
	21st to end	Day	22% 12% 4 8% 5% 4 4 3 3 4 31%	2443
May	1st to 10th	Day	20% 9% 3 8% 4 5% 5% 4 5% 7% 30%	4426
	11th to 20th	Day	16% 9% 3 8% 5% 4 4 3 5% 7% 35%	4398
	21st to end	Day	17% 7% 2 8% 5% 5% 4 4 6% 6% 36%	4837
June	1st to 10th	Day	21% 9% 3 7% 6% 4 4 4 5% 7% 29%	2660
	11th to 20th	Day	15% 6% 3 6% 5% 4 5% 4 6% 8% 38%	2660
	21st to end	Day	18% 7% 2 7% 6% 6% 5% 4 5% 7% 32%	2660
July	1st to 10th	Day	12% 7% 2 7% 6% 5% 6% 5% 7% 9% 33%	4440
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	4440
	21st to end	Day	11% 6% 2 6% 4 4 4 4 5% 8% 46%	4814
August	1st to 10th	Day	14% 6% 3 8% 6% 5% 6% 5% 7% 8% 34%	4340
	11th to 20th	Day	16% 7% 2 7% 5% 5% 5% 4 6% 7% 36%	4044
	21st to end	Day	12% 6% 2 6% 4 4 5% 5% 7% 10% 38%	4180
September	1st to 10th	Day	14% 7% 2 7% 4 3 4 3 5% 8% 43%	2280
	11th to 20th	Day	13% 6% 3 7% 4 4 4 3 5% 7% 44%	2280
	21st to end	Day	19% 7% 2 6% 4 4 3 4 6% 8% 37%	2019
October	1st to 10th	Day	20% 10% 2 6% 4 4 4 5% 5% 6% 34%	1900
	11th to 20th	Day	23% 11% 3 8% 6% 4 4 4 4 6% 27%	1900
	21st to end	Day	26% 11% 3 7% 6% 4 4 3 4 5% 27%	1946
November	1st to 10th	Day	15% 12% 3 7% 5% 5% 5% 4 6% 7% 32%	1730
	11th to 20th	Day	18% 14% 5% 11% 6% 4 4 3 5% 6% 24%	1600
	21st to end	Day	20% 17% 6% 12% 5% 4 5% 3 4 5% 19%	1600
December	1st to 10th	Day	20% 21% 6% 12% 6% 5% 5% 3 4 5% 15%	1584
	11th to 20th	Day	18% 15% 6% 12% 6% 4 3 3 5% 5% 23%	1906
	21st to end	Day	24% 21% 6% 13% 4 2 3 2 2 3 18%	2772
January	1st to 10th	Night	15% 19% 7% 14% 6% 5% 4 3 4 5% 20%	4429
	11th to 20th	Night	11% 14% 6% 14% 7% 5% 5% 4 5% 6% 22%	4440
	21st to end	Night	13% 18% 7% 13% 7% 6% 5% 3 4 4 20%	4754
February	1st to 10th	Night	11% 15% 5% 13% 9% 6% 5% 4 4 6% 22%	2470
	11th to 20th	Night	12% 14% 5% 11% 8% 5% 6% 4 4 5% 27%	2403
	21st to end	Night	12% 16% 4 10% 6% 6% 4 3 5% 6% 27%	1903
March	1st to 10th	Night	18% 14% 4 8% 5% 4 4 3 3 5% 31%	3692
	11th to 20th	Night	14% 19% 6% 10% 5% 4 4 3 5% 5% 24%	3479
	21st to end	Night	12% 10% 3 10% 4 4 4 3 5% 6% 39%	3631
April	1st to 10th	Night	20% 12% 3 8% 5% 4 5% 3 4 7% 30%	1900
	11th to 20th	Night	17% 11% 3 6% 4 4 4 4 5% 6% 36%	1875
	21st to end	Night	21% 11% 3 8% 4 4 3 3 4 5% 33%	1753
May	1st to 10th	Night	19% 10% 4 7% 5% 4 5% 4 6% 6% 30%	2514
	11th to 20th	Night	18% 8% 3 6% 4 4 5% 3 6% 7% 34%	2495
	21st to end	Night	14% 8% 3 7% 6% 5% 5% 4 6% 7% 37%	2738
June	1st to 10th	Night	18% 6% 2 6% 5% 5% 5% 5% 6% 9% 33%	1520
	11th to 20th	Night	13% 6% 3 6% 4 4 4 4 6% 6% 43%	1520
	21st to end	Night	18% 6% 3 5% 6% 5% 6% 4 6% 8% 35%	1520
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 5% 5% 5% 7% 37%	2520
	11th to 20th	Night	13% 6% 2 7% 4 5% 5% 4 7% 7% 40%	2520
	21st to end	Night	8% 6% 2 6% 5% 4 5% 4 6% 9% 46%	2739
August	1st to 10th	Night	11% 7% 3 8% 5% 5% 6% 4 5% 7% 39%	2587
	11th to 20th	Night	15% 7% 3 6% 4 4 4 4 5% 7% 40%	2785
	21st to end	Night	15% 6% 2 6% 4 5% 4 4 5% 7% 41%	3444
September	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 5% 6% 47%	1900
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 6% 8% 48%	1900
	21st to end	Night	18% 7% 2 6% 4 3 4 2 4 6% 43%	2158
October	1st to 10th	Night	19% 8% 3 6% 4 3 4 3 5% 6% 39%	2280
	11th to 20th	Night	20% 10% 3 8% 6% 5% 4 3 5% 7% 30%	2280
	21st to end	Night	22% 12% 3 9% 5% 5% 5% 3 4 5% 27%	2651
November	1st to 10th	Night	16% 12% 4 8% 5% 5% 4 4 5% 6% 31%	2567
	11th to 20th	Night	17% 13% 4 10% 5% 5% 5% 4 4 5% 27%	2800
	21st to end	Night	20% 15% 5% 12% 6% 4 5% 3 4 6% 21%	2800
December	1st to 10th	Night	18% 20% 6% 11% 7% 4 4 4 4 5% 17%	2779
	11th to 20th	Night	21% 16% 5% 11% 5% 4 4 3 3 4 25%	3288
	21st to end	Night	26% 21% 5% 12% 5% 3 3 2 3 3 17%	4884

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	71% 1 11% 11% 6%	2518
	11th to 20th	Day	68% 2 10% 14% 6%	2520
	21st to end	Day	71% 2 8% 11% 6% 1	2900
February	1st to 10th	Day	64% 3 8% 18% 5% 1	1710
	11th to 20th	Day	61% 2 11% 13% 10% 1	1672
	21st to end	Day	61% 2 10% 13% 11% 1	1550
March	1st to 10th	Day	63% 1 8% 16% 11% 1	3147
	11th to 20th	Day	63% 1 10% 15% 9% 2	3480
	21st to end	Day	46% 1 6% 26% 18% 3	4001
April	1st to 10th	Day	59% 2 6% 19% 12% 3	2280
	11th to 20th	Day	54% 2 6% 21% 15% 2	2254
	21st to end	Day	58% 2 7% 17% 13% 3	2443
May	1st to 10th	Day	55% 2 6% 24% 11% 2	4440
	11th to 20th	Day	51% 1 12% 24% 10% 1	4402
	21st to end	Day	49% 3 11% 20% 15% 2	4837
June	1st to 10th	Day	55% 3 10% 20% 11% 1	2660
	11th to 20th	Day	44% 4 11% 26% 12% 2	2660
	21st to end	Day	51% 5% 13% 21% 10% 1	2660
July	1st to 10th	Day	44% 6% 14% 26% 9%	4370
	11th to 20th	Day	41% 5% 16% 30% 8%	4365
	21st to end	Day	37% 5% 14% 33% 11%	4661
August	1st to 10th	Day	46% 6% 16% 25% 8%	4326
	11th to 20th	Day	46% 5% 15% 28% 6% 1	4083
	21st to end	Day	40% 6% 16% 26% 12% 1	4180
September	1st to 10th	Day	41% 4 13% 30% 12%	2280
	11th to 20th	Day	40% 4 12% 31% 12% 1	2280
	21st to end	Day	46% 4 15% 26% 9%	2019
October	1st to 10th	Day	50% 4 10% 29% 6% 1	3160
	11th to 20th	Day	52% 4 13% 23% 8%	3140
	21st to end	Day	53% 5% 18% 18% 6%	3184
November	1st to 10th	Day	51% 4 14% 24% 7% 1	1730
	11th to 20th	Day	61% 3 12% 15% 8% 1	1600
	21st to end	Day	69% 4 11% 10% 6% 1	1600
December	1st to 10th	Day	72% 4 10% 11% 4	1584
	11th to 20th	Day	65% 3 11% 14% 7%	1906
	21st to end	Day	75% 1 6% 14% 4	2772
January	1st to 10th	Night	69% 2 15% 11% 3	4429
	11th to 20th	Night	64% 2 14% 15% 5% 1	4440
	21st to end	Night	70% 3 9% 11% 7%	4754
February	1st to 10th	Night	64% 2 9% 17% 7% 1	2470
	11th to 20th	Night	60% 3 8% 21% 7% 1	2405
	21st to end	Night	58% 3 9% 20% 10% 1	1903
March	1st to 10th	Night	59% 1 10% 19% 9% 2	3702
	11th to 20th	Night	63% 1 10% 17% 7% 1	3480
	21st to end	Night	48% 2 6% 22% 18% 4	3631
April	1st to 10th	Night	56% 3 7% 19% 13% 2	1900
	11th to 20th	Night	49% 2 7% 24% 15% 2	1875
	21st to end	Night	55% 3 7% 18% 15% 3	1753
May	1st to 10th	Night	55% 2 9% 22% 10% 2	2520
	11th to 20th	Night	50% 3 10% 24% 11% 2	2496
	21st to end	Night	47% 2 10% 23% 16% 2	2739
June	1st to 10th	Night	47% 4 13% 27% 8% 1	1520
	11th to 20th	Night	41% 4 10% 29% 14% 2	1520
	21st to end	Night	46% 6% 13% 22% 12% 1	1520
July	1st to 10th	Night	45% 6% 15% 20% 13% 1	2480
	11th to 20th	Night	40% 6% 14% 30% 9%	2472
	21st to end	Night	34% 6% 15% 32% 12%	2651
August	1st to 10th	Night	43% 6% 15% 26% 11%	2577
	11th to 20th	Night	43% 5% 15% 29% 8%	2812
	21st to end	Night	41% 5% 15% 26% 12% 2	3444
September	1st to 10th	Night	39% 4 12% 31% 14% 1	1900
	11th to 20th	Night	35% 3 14% 36% 11% 1	1900
	21st to end	Night	44% 3 12% 30% 10%	2158
October	1st to 10th	Night	42% 4 13% 30% 13%	3800
	11th to 20th	Night	48% 4 15% 24% 8%	3779
	21st to end	Night	51% 5% 18% 18% 9%	4363
November	1st to 10th	Night	53% 3 13% 21% 9%	2567
	11th to 20th	Night	60% 3 10% 17% 9% 1	2800
	21st to end	Night	66% 3 11% 16% 4	2800
December	1st to 10th	Night	70% 4 8% 13% 4	2779
	11th to 20th	Night	65% 2 8% 17% 8% 1	3288
	21st to end	Night	75% 2 6% 13% 4	4884

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	23% 24% 32% 18% 3 1	180
	11th to 20th	Day	24% 16% 39% 16% 4 1	180
	21st to end	Day	22% 20% 34% 18% 6%	234
February	1st to 10th	Day	31% 23% 32% 11% 2	270
	11th to 20th	Day	26% 30% 34% 9%	270
	21st to end	Day	31% 24% 30% 14% 1 1	362
March	1st to 10th	Day	26% 20% 36% 13% 5%	460
	11th to 20th	Day	27% 22% 32% 16% 3 1	460
	21st to end	Day	30% 22% 29% 14% 5% 1	506
April	1st to 10th	Day	32% 20% 27% 15% 5% 1	460
	11th to 20th	Day	35% 20% 21% 13% 9% 2	452
	21st to end	Day	32% 20% 30% 13% 5% 1	460
May	1st to 10th	Day	29% 15% 32% 15% 6% 3	463
	11th to 20th	Day	21% 17% 31% 22% 6% 3	487
	21st to end	Day	23% 17% 33% 19% 7% 1	529
June	1st to 10th	Day	27% 11% 34% 20% 6% 2	490
	11th to 20th	Day	19% 13% 32% 23% 10% 3	490
	21st to end	Day	21% 12% 33% 22% 9% 2	490
July	1st to 10th	Day	13% 7% 35% 33% 10% 2	485
	11th to 20th	Day	14% 10% 37% 25% 11% 2	484
	21st to end	Day	13% 8% 34% 30% 12% 3	532
August	1st to 10th	Day	16% 8% 31% 27% 14% 4	486
	11th to 20th	Day	16% 6% 25% 33% 13% 7%	479
	21st to end	Day	18% 11% 29% 24% 12% 6%	539
September	1st to 10th	Day	17% 11% 32% 21% 14% 6%	490
	11th to 20th	Day	15% 11% 23% 23% 18% 9%	490
	21st to end	Day	22% 13% 28% 18% 13% 6%	490
October	1st to 10th	Day	25% 17% 23% 22% 10% 3	490
	11th to 20th	Day	28% 22% 29% 14% 6% 1	490
	21st to end	Day	32% 16% 31% 17% 5%	462
November	1st to 10th	Day	29% 18% 29% 19% 4 1	364
	11th to 20th	Day	28% 23% 31% 11% 7% 1	200
	21st to end	Day	31% 24% 29% 12% 4 1	200
December	1st to 10th	Day	31% 13% 40% 14% 3	196
	11th to 20th	Day	29% 29% 31% 9% 1 1	180
	21st to end	Day	31% 20% 36% 10% 3 1	198
January	1st to 10th	Night	28% 14% 37% 17% 4	760
	11th to 20th	Night	29% 17% 28% 21% 5%	760
	21st to end	Night	18% 13% 39% 23% 6%	836
February	1st to 10th	Night	20% 19% 37% 20% 4	760
	11th to 20th	Night	23% 19% 39% 16% 3	743
	21st to end	Night	23% 21% 29% 22% 4	628
March	1st to 10th	Night	26% 16% 33% 20% 4	760
	11th to 20th	Night	24% 17% 35% 18% 5% 1	760
	21st to end	Night	23% 17% 34% 19% 7%	836
April	1st to 10th	Night	27% 16% 30% 23% 5%	760
	11th to 20th	Night	26% 16% 30% 19% 7% 1	751
	21st to end	Night	27% 14% 30% 22% 6%	613
May	1st to 10th	Night	24% 12% 27% 27% 9% 1	380
	11th to 20th	Night	24% 10% 28% 30% 8%	374
	21st to end	Night	16% 9% 37% 27% 10%	411
June	1st to 10th	Night	21% 8% 32% 32% 7% 1	380
	11th to 20th	Night	17% 9% 28% 31% 14% 1	380
	21st to end	Night	18% 6% 30% 33% 13% 1	380
July	1st to 10th	Night	11% 4 30% 39% 16% 1	370
	11th to 20th	Night	14% 5% 27% 38% 17% 1	368
	21st to end	Night	10% 4 27% 44% 14% 1	416
August	1st to 10th	Night	12% 5% 23% 38% 21% 1	420
	11th to 20th	Night	12% 4 22% 38% 22% 3	564
	21st to end	Night	14% 7% 26% 33% 17% 2	817
September	1st to 10th	Night	17% 5% 29% 32% 16% 1	760
	11th to 20th	Night	16% 6% 23% 31% 19% 4	760
	21st to end	Night	21% 10% 25% 25% 17% 2	760
October	1st to 10th	Night	24% 12% 27% 22% 14% 1	760
	11th to 20th	Night	26% 12% 33% 21% 8% 1	760
	21st to end	Night	28% 15% 29% 22% 5%	836
November	1st to 10th	Night	25% 17% 28% 22% 7% 1	780
	11th to 20th	Night	27% 18% 30% 16% 9%	800
	21st to end	Night	32% 18% 25% 20% 4 1	800
December	1st to 10th	Night	30% 18% 30% 19% 3	795
	11th to 20th	Night	27% 19% 28% 20% 5% 1	760
	21st to end	Night	35% 16% 29% 16% 3	836

Page generated at 2024-12-06 03:54:52. Version ac07

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