Jasper Maligne Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jasper Maligne Lake clear sky chart from 2005-11-06 to 2025-05-11.

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	9% 17% 7% 14% 7% 6% 5% 4 5% 6% 22%	117022
	Night	6% 16% 7% 15% 8% 6% 5% 4 6% 6% 21%	120617
Transparency	Day	62% 6% 11% 13% 6% 1	116766
	Night	62% 7% 12% 12% 6% 1	120520
Seeing	Day	23% 19% 29% 19% 8% 2	16607
	Night	14% 17% 36% 23% 9% 1	25140

By Month

Percentage Cloud Cover NW (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	1 12% 9% 22% 10% 11% 7% 5% 6% 6% 10%	2719
	11th to 20th	Day	3 14% 7% 18% 8% 6% 4 5% 5% 5% 24%	3246
	21st to end	Day	3 20% 8% 18% 7% 5% 4 3 5% 6% 21%	4004
February	1st to 10th	Day	4 15% 10% 17% 7% 6% 7% 4 6% 6% 19%	1600
	11th to 20th	Day	2 14% 7% 22% 10% 6% 6% 5% 6% 5% 18%	1637
	21st to end	Day	2 13% 9% 19% 11% 8% 5% 4 6% 6% 18%	1650
March	1st to 10th	Day	1 17% 8% 17% 9% 7% 6% 5% 7% 7% 17%	4518
	11th to 20th	Day	2 15% 11% 20% 7% 6% 5% 3 5% 5% 21%	4648
	21st to end	Day	4 22% 10% 20% 7% 5% 5% 3 5% 4 15%	5962
April	1st to 10th	Day	4 21% 12% 18% 9% 6% 5% 4 4 3 12%	2400
	11th to 20th	Day	4 21% 9% 17% 8% 6% 5% 3 5% 5% 17%	2517
	21st to end	Day	7% 25% 7% 14% 6% 5% 4 4 5% 5% 18%	2730
May	1st to 10th	Day	9% 24% 6% 12% 5% 4 4 3 5% 6% 21%	4560
	11th to 20th	Day	12% 20% 5% 12% 6% 5% 5% 4 6% 7% 19%	4601
	21st to end	Day	14% 29% 5% 13% 7% 4 4 3 4 4 13%	5161
June	1st to 10th	Day	19% 15% 4 11% 7% 6% 5% 4 5% 6% 17%	3011
	11th to 20th	Day	22% 19% 5% 13% 7% 6% 5% 4 5% 4 12%	3040
	21st to end	Day	17% 13% 6% 12% 7% 5% 5% 3 5% 6% 20%	3040
July	1st to 10th	Day	15% 11% 3 8% 5% 5% 4 3 4 5% 35%	5060
	11th to 20th	Day	12% 7% 3 8% 6% 5% 5% 4 5% 6% 39%	4974
	21st to end	Day	17% 11% 4 9% 6% 5% 5% 4 5% 6% 29%	4853
August	1st to 10th	Day	15% 8% 3 9% 6% 6% 6% 4 5% 6% 32%	4401
	11th to 20th	Day	14% 9% 4 11% 7% 7% 6% 4 6% 6% 27%	4330
	21st to end	Day	18% 14% 4 9% 5% 5% 5% 3 5% 5% 28%	4464
September	1st to 10th	Day	17% 12% 4 9% 5% 4 4 4 5% 4 31%	2280
	11th to 20th	Day	13% 15% 4 8% 5% 5% 4 3 5% 6% 31%	2204
	21st to end	Day	15% 19% 3 10% 5% 4 4 4 5% 6% 26%	2090
October	1st to 10th	Day	11% 24% 5% 11% 5% 4 4 3 6% 6% 20%	3256
	11th to 20th	Day	12% 23% 9% 10% 4 4 4 3 5% 7% 20%	2883
	21st to end	Day	4 20% 11% 13% 6% 5% 4 3 5% 5% 25%	3101
November	1st to 10th	Day	6% 19% 8% 14% 10% 7% 6% 4 5% 5% 16%	1639
	11th to 20th	Day	3 15% 8% 15% 7% 5% 6% 6% 7% 7% 23%	1400
	21st to end	Day	3 17% 7% 15% 9% 7% 4 5% 7% 7% 19%	1400
December	1st to 10th	Day	4 17% 7% 18% 8% 7% 7% 5% 6% 6% 15%	2290
	11th to 20th	Day	2 15% 8% 17% 8% 8% 7% 5% 5% 8% 15%	2361
	21st to end	Day	1 17% 9% 18% 7% 6% 5% 4 6% 7% 21%	2992
January	1st to 10th	Night	1 14% 9% 26% 12% 7% 6% 4 4 5% 11%	7226
	11th to 20th	Night	3 13% 8% 15% 8% 6% 6% 5% 6% 6% 24%	6682
	21st to end	Night	4 20% 9% 17% 9% 6% 4 3 5% 5% 19%	6952
February	1st to 10th	Night	4 18% 8% 17% 10% 5% 7% 4 6% 5% 17%	2800
	11th to 20th	Night	3 16% 7% 19% 9% 7% 6% 5% 5% 6% 19%	2644
	21st to end	Night	2 14% 7% 14% 10% 7% 6% 5% 7% 7% 20%	1980
March	1st to 10th	Night	1 16% 7% 17% 10% 7% 7% 5% 6% 6% 18%	5376
	11th to 20th	Night	2 14% 11% 21% 8% 5% 5% 4 7% 6% 17%	5351
	21st to end	Night	4 18% 9% 18% 8% 6% 5% 4 5% 5% 18%	5011
April	1st to 10th	Night	2 18% 9% 17% 10% 6% 5% 4 6% 6% 15%	2000
	11th to 20th	Night	3 16% 6% 14% 7% 7% 5% 5% 7% 7% 24%	1834
	21st to end	Night	6% 20% 5% 11% 5% 6% 6% 4 6% 6% 25%	1668
May	1st to 10th	Night	6% 21% 5% 12% 7% 5% 4 3 6% 8% 23%	2620
	11th to 20th	Night	11% 20% 5% 9% 4 5% 4 4 6% 6% 24%	2298
	21st to end	Night	14% 24% 5% 13% 6% 5% 5% 3 4 5% 16%	2414
June	1st to 10th	Night	16% 14% 3 9% 8% 4 5% 5% 5% 6% 26%	1166
	11th to 20th	Night	19% 13% 4 8% 8% 6% 6% 6% 6% 8% 17%	1140
	21st to end	Night	13% 10% 4 8% 6% 6% 6% 6% 8% 6% 29%	1140
July	1st to 10th	Night	15% 9% 2 6% 4 4 4 3 4 6% 42%	1900
	11th to 20th	Night	11% 6% 2 4 3 4 4 4 6% 7% 50%	1983
	21st to end	Night	18% 8% 3 6% 5% 4 4 4 5% 8% 36%	2696
August	1st to 10th	Night	12% 8% 3 7% 5% 5% 4 4 6% 9% 37%	2529
	11th to 20th	Night	14% 8% 3 8% 6% 5% 6% 4 6% 8% 32%	2497
	21st to end	Night	17% 11% 2 7% 5% 4 5% 4 6% 7% 32%	3202
September	1st to 10th	Night	14% 10% 3 7% 4 4 4 4 6% 7% 36%	1900
	11th to 20th	Night	14% 12% 3 8% 5% 4 4 3 5% 6% 36%	1976
	21st to end	Night	12% 13% 3 8% 5% 6% 5% 4 6% 7% 30%	2090
October	1st to 10th	Night	7% 27% 6% 9% 5% 5% 5% 4 7% 6% 18%	3721
	11th to 20th	Night	11% 18% 9% 10% 5% 5% 4 4 6% 7% 22%	4045
	21st to end	Night	5% 19% 11% 14% 7% 5% 4 3 4 7% 21%	4457
November	1st to 10th	Night	8% 18% 9% 14% 9% 8% 6% 4 6% 5% 14%	2640
	11th to 20th	Night	3 16% 7% 15% 10% 7% 6% 5% 7% 7% 17%	2998
	21st to end	Night	3 16% 7% 16% 10% 8% 6% 5% 5% 6% 17%	3000
December	1st to 10th	Night	5% 17% 8% 19% 9% 8% 8% 5% 5% 4 13%	4890
	11th to 20th	Night	2 17% 12% 19% 10% 7% 7% 5% 6% 6% 10%	5827
	21st to end	Night	2 17% 10% 18% 7% 5% 5% 4 7% 8% 18%	7964

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% 7% 9% 9% 3 1	2719
	11th to 20th	Day	61% 6% 6% 10% 11% 5%	3270
	21st to end	Day	64% 7% 16% 9% 4	4004
February	1st to 10th	Day	67% 6% 8% 7% 9% 3	1600
	11th to 20th	Day	67% 6% 8% 12% 6% 1	1645
	21st to end	Day	67% 6% 9% 12% 5% 2	1650
March	1st to 10th	Day	66% 6% 8% 11% 9%	4518
	11th to 20th	Day	65% 6% 10% 14% 4	4648
	21st to end	Day	70% 6% 7% 11% 5% 1	5962
April	1st to 10th	Day	76% 6% 9% 7% 2	2400
	11th to 20th	Day	69% 7% 11% 11% 2	2517
	21st to end	Day	69% 7% 9% 13% 2	2730
May	1st to 10th	Day	64% 5% 13% 14% 4	4560
	11th to 20th	Day	63% 7% 12% 14% 5%	4605
	21st to end	Day	74% 5% 10% 8% 3	5162
June	1st to 10th	Day	66% 7% 10% 12% 4 1	3011
	11th to 20th	Day	72% 6% 11% 8% 2	3040
	21st to end	Day	64% 6% 14% 12% 4 1	3040
July	1st to 10th	Day	50% 5% 9% 17% 15% 4	4981
	11th to 20th	Day	43% 6% 12% 23% 15% 1	4887
	21st to end	Day	54% 6% 10% 16% 12% 3	4700
August	1st to 10th	Day	50% 6% 13% 24% 7%	4384
	11th to 20th	Day	54% 8% 14% 19% 5%	4372
	21st to end	Day	57% 5% 13% 20% 4	4463
September	1st to 10th	Day	56% 5% 13% 19% 5% 1	2280
	11th to 20th	Day	54% 5% 15% 16% 9%	2204
	21st to end	Day	60% 6% 13% 14% 6% 1	2090
October	1st to 10th	Day	63% 6% 14% 12% 4	3256
	11th to 20th	Day	64% 7% 14% 14% 1	2883
	21st to end	Day	62% 7% 15% 13% 3	3101
November	1st to 10th	Day	71% 7% 9% 9% 4 1	1639
	11th to 20th	Day	60% 10% 14% 9% 6% 1	1400
	21st to end	Day	63% 8% 14% 7% 4 4	1400
December	1st to 10th	Day	68% 12% 8% 8% 4 1	2290
	11th to 20th	Day	66% 9% 10% 10% 3 1	2363
	21st to end	Day	61% 8% 10% 13% 8%	2992
January	1st to 10th	Night	73% 8% 7% 7% 3 1	7226
	11th to 20th	Night	60% 6% 6% 10% 15% 4	6720
	21st to end	Night	68% 6% 12% 11% 3 1	6952
February	1st to 10th	Night	68% 6% 8% 7% 8% 3	2800
	11th to 20th	Night	65% 8% 9% 10% 7% 1	2646
	21st to end	Night	59% 7% 9% 16% 7% 2	1980
March	1st to 10th	Night	63% 7% 8% 13% 8% 1	5376
	11th to 20th	Night	64% 7% 11% 14% 3	5352
	21st to end	Night	66% 6% 9% 12% 7%	5011
April	1st to 10th	Night	69% 8% 12% 11% 2	2000
	11th to 20th	Night	59% 7% 15% 14% 5%	1834
	21st to end	Night	60% 8% 12% 16% 4	1668
May	1st to 10th	Night	60% 6% 15% 16% 3	2620
	11th to 20th	Night	58% 9% 12% 15% 7%	2298
	21st to end	Night	70% 6% 11% 10% 3	2414
June	1st to 10th	Night	56% 8% 17% 12% 6% 1	1166
	11th to 20th	Night	65% 9% 13% 11% 3	1140
	21st to end	Night	52% 8% 20% 15% 5% 1	1140
July	1st to 10th	Night	45% 4 12% 19% 19% 1	1870
	11th to 20th	Night	34% 6% 12% 26% 22%	1947
	21st to end	Night	46% 5% 14% 22% 9% 4	2611
August	1st to 10th	Night	40% 9% 16% 31% 3	2521
	11th to 20th	Night	45% 10% 21% 20% 4	2521
	21st to end	Night	50% 8% 22% 16% 4	3202
September	1st to 10th	Night	47% 6% 18% 22% 6% 1	1900
	11th to 20th	Night	50% 6% 16% 19% 8%	1976
	21st to end	Night	52% 9% 15% 16% 6% 1	2090
October	1st to 10th	Night	63% 9% 14% 11% 2	3721
	11th to 20th	Night	61% 6% 16% 14% 2	4045
	21st to end	Night	64% 7% 17% 9% 3	4457
November	1st to 10th	Night	71% 8% 10% 7% 3 1	2640
	11th to 20th	Night	64% 11% 10% 8% 6% 1	2998
	21st to end	Night	65% 9% 9% 9% 5% 3	3000
December	1st to 10th	Night	74% 8% 6% 6% 5% 1	4890
	11th to 20th	Night	72% 8% 9% 8% 3	5824
	21st to end	Night	64% 8% 11% 11% 5% 1	7964

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	13% 22% 37% 21% 7% 1	200
	11th to 20th	Day	16% 25% 32% 22% 4 3	200
	21st to end	Day	20% 25% 37% 13% 4 2	220
February	1st to 10th	Day	22% 21% 36% 15% 5% 2	200
	11th to 20th	Day	14% 23% 35% 21% 6% 1	277
	21st to end	Day	19% 25% 33% 16% 6% 1	414
March	1st to 10th	Day	19% 25% 31% 14% 8% 2	500
	11th to 20th	Day	17% 29% 31% 16% 5% 2	500
	21st to end	Day	19% 27% 29% 17% 6% 2	550
April	1st to 10th	Day	26% 21% 31% 16% 5% 1	500
	11th to 20th	Day	18% 24% 30% 20% 7% 1	492
	21st to end	Day	23% 24% 25% 18% 8% 2	500
May	1st to 10th	Day	24% 16% 33% 17% 7% 2	503
	11th to 20th	Day	16% 14% 25% 29% 13% 3	619
	21st to end	Day	22% 12% 23% 24% 15% 3	734
June	1st to 10th	Day	25% 17% 30% 19% 7% 1	841
	11th to 20th	Day	29% 16% 28% 18% 8% 1	870
	21st to end	Day	23% 13% 26% 23% 12% 2	870
July	1st to 10th	Day	23% 13% 26% 25% 13% 1	856
	11th to 20th	Day	22% 13% 30% 24% 9% 2	805
	21st to end	Day	19% 14% 29% 24% 11% 3	568
August	1st to 10th	Day	21% 10% 31% 24% 11% 4	487
	11th to 20th	Day	20% 19% 35% 17% 8% 1	477
	21st to end	Day	27% 17% 31% 17% 7% 1	539
September	1st to 10th	Day	29% 18% 28% 18% 7% 1	490
	11th to 20th	Day	25% 22% 27% 21% 4 2	490
	21st to end	Day	37% 26% 19% 14% 4 1	490
October	1st to 10th	Day	30% 21% 25% 16% 7% 2	490
	11th to 20th	Day	30% 24% 26% 15% 4 2	328
	21st to end	Day	25% 20% 32% 18% 5%	330
November	1st to 10th	Day	31% 24% 28% 11% 4 2	247
	11th to 20th	Day	26% 24% 32% 13% 4 1	200
	21st to end	Day	20% 27% 25% 18% 8% 3	200
December	1st to 10th	Day	14% 29% 29% 19% 6% 4	200
	11th to 20th	Day	15% 30% 34% 17% 5% 1	200
	21st to end	Day	11% 20% 37% 21% 8% 3	220
January	1st to 10th	Night	12% 21% 44% 17% 4 1	1100
	11th to 20th	Night	11% 23% 44% 17% 4 1	939
	21st to end	Night	13% 25% 41% 16% 5% 1	880
February	1st to 10th	Night	14% 19% 36% 25% 7% 1	800
	11th to 20th	Night	9% 19% 42% 23% 6% 1	784
	21st to end	Night	13% 14% 37% 26% 9% 1	660
March	1st to 10th	Night	9% 19% 41% 21% 9% 1	800
	11th to 20th	Night	8% 23% 41% 21% 6% 1	800
	21st to end	Night	9% 17% 33% 29% 11% 1	880
April	1st to 10th	Night	10% 19% 31% 30% 10% 1	800
	11th to 20th	Night	9% 15% 39% 24% 12% 1	646
	21st to end	Night	15% 14% 29% 32% 9% 1	468
May	1st to 10th	Night	17% 10% 24% 33% 15% 1	400
	11th to 20th	Night	10% 9% 24% 35% 20% 2	375
	21st to end	Night	19% 10% 22% 26% 21% 2	411
June	1st to 10th	Night	21% 6% 33% 25% 14% 1	380
	11th to 20th	Night	24% 9% 27% 25% 14%	380
	21st to end	Night	17% 8% 24% 30% 19% 1	380
July	1st to 10th	Night	20% 5% 23% 37% 15% 1	370
	11th to 20th	Night	20% 8% 22% 33% 16%	368
	21st to end	Night	15% 7% 20% 39% 19%	416
August	1st to 10th	Night	16% 4 18% 37% 23% 2	378
	11th to 20th	Night	15% 8% 20% 36% 19% 1	376
	21st to end	Night	21% 11% 29% 28% 11% 1	657
September	1st to 10th	Night	20% 10% 30% 26% 13% 1	760
	11th to 20th	Night	19% 12% 26% 27% 15% 2	760
	21st to end	Night	23% 16% 29% 22% 9% 2	760
October	1st to 10th	Night	18% 16% 33% 24% 9% 1	760
	11th to 20th	Night	18% 16% 36% 23% 6% 1	760
	21st to end	Night	16% 19% 41% 19% 5%	836
November	1st to 10th	Night	18% 23% 40% 14% 5%	780
	11th to 20th	Night	15% 24% 44% 13% 3 1	998
	21st to end	Night	14% 22% 43% 16% 4 2	1000
December	1st to 10th	Night	13% 23% 41% 17% 6%	1000
	11th to 20th	Night	11% 24% 44% 16% 6%	1068
	21st to end	Night	10% 19% 46% 19% 6% 1	1210

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