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 2026-09-14.

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% 16% 6% 13% 7% 6% 5% 4 5% 6% 23%	154163
	Night	6% 15% 7% 14% 7% 6% 5% 4 6% 6% 22%	145639
Transparency	Day	60% 6% 12% 15% 6% 1	153866
	Night	60% 7% 13% 13% 6% 1	145520
Seeing	Day	23% 20% 29% 19% 8% 2	18567
	Night	15% 17% 35% 23% 9% 1	26731

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 13% 9% 27% 11% 9% 6% 4 6% 5% 9%	3527
	11th to 20th	Day	3 14% 7% 15% 7% 5% 4 4 5% 6% 30%	4234
	21st to end	Day	3 19% 8% 17% 7% 5% 5% 4 5% 8% 20%	5186
February	1st to 10th	Day	4 15% 10% 17% 7% 6% 7% 3 6% 6% 19%	1680
	11th to 20th	Day	1 14% 7% 21% 9% 6% 6% 5% 6% 5% 18%	1721
	21st to end	Day	2 13% 10% 19% 10% 8% 5% 4 6% 6% 17%	1730
March	1st to 10th	Day	1 17% 8% 17% 10% 7% 6% 5% 7% 7% 16%	4618
	11th to 20th	Day	2 15% 11% 21% 7% 6% 5% 3 5% 5% 20%	4750
	21st to end	Day	4 22% 10% 20% 7% 5% 5% 3 5% 4 15%	6094
April	1st to 10th	Day	4 22% 12% 18% 9% 6% 5% 4 4 3 12%	2520
	11th to 20th	Day	4 21% 9% 17% 8% 5% 5% 3 5% 5% 17%	2644
	21st to end	Day	7% 25% 7% 14% 6% 5% 4 4 5% 5% 18%	2866
May	1st to 10th	Day	6% 17% 5% 11% 5% 5% 5% 4 6% 8% 28%	8195
	11th to 20th	Day	9% 22% 6% 14% 8% 6% 6% 4 6% 7% 13%	8577
	21st to end	Day	13% 21% 5% 11% 6% 4 4 4 5% 6% 20%	9649
June	1st to 10th	Day	19% 16% 5% 11% 6% 6% 5% 4 5% 6% 18%	3328
	11th to 20th	Day	21% 19% 5% 12% 7% 6% 5% 4 5% 5% 12%	3360
	21st to end	Day	17% 14% 6% 12% 7% 6% 5% 3 5% 6% 19%	3360
July	1st to 10th	Day	14% 11% 4 9% 6% 6% 5% 4 5% 6% 29%	9420
	11th to 20th	Day	15% 8% 3 8% 5% 5% 6% 5% 5% 6% 33%	9264
	21st to end	Day	14% 10% 3 9% 5% 6% 5% 4 5% 6% 31%	9034
August	1st to 10th	Day	13% 8% 3 8% 6% 6% 6% 4 6% 6% 34%	6441
	11th to 20th	Day	13% 10% 5% 11% 7% 7% 6% 4 6% 7% 26%	6367
	21st to end	Day	15% 12% 4 8% 5% 5% 5% 3 5% 7% 31%	6484
September	1st to 10th	Day	16% 12% 4 9% 5% 4 4 4 5% 5% 33%	2520
	11th to 20th	Day	13% 15% 4 8% 5% 5% 5% 3 5% 6% 33%	2357
	21st to end	Day	16% 19% 3 9% 5% 4 4 4 5% 6% 26%	2200
October	1st to 10th	Day	11% 24% 5% 11% 5% 4 4 3 6% 6% 20%	3359
	11th to 20th	Day	12% 23% 9% 10% 4 4 4 3 5% 7% 20%	2974
	21st to end	Day	4 20% 11% 13% 6% 5% 4 3 5% 5% 25%	3200
November	1st to 10th	Day	6% 20% 8% 14% 9% 7% 6% 4 5% 5% 16%	1722
	11th to 20th	Day	3 15% 8% 14% 7% 5% 6% 6% 7% 7% 23%	1470
	21st to end	Day	3 17% 7% 14% 9% 8% 5% 5% 7% 7% 18%	1470
December	1st to 10th	Day	4 18% 7% 19% 8% 7% 7% 5% 6% 6% 14%	2360
	11th to 20th	Day	3 15% 8% 18% 8% 8% 7% 5% 5% 7% 15%	2424
	21st to end	Day	1 17% 9% 18% 7% 6% 5% 4 6% 7% 20%	3058
January	1st to 10th	Night	1 16% 10% 29% 12% 7% 6% 3 4 4 9%	9366
	11th to 20th	Night	3 14% 7% 13% 7% 5% 6% 4 5% 6% 28%	8708
	21st to end	Night	3 18% 8% 18% 8% 7% 5% 4 5% 5% 19%	8994
February	1st to 10th	Night	4 19% 8% 17% 9% 5% 6% 4 6% 5% 17%	2940
	11th to 20th	Night	3 15% 7% 19% 9% 7% 6% 5% 5% 6% 19%	2780
	21st to end	Night	2 14% 7% 15% 11% 7% 6% 5% 6% 7% 20%	2076
March	1st to 10th	Night	2 16% 7% 17% 10% 7% 7% 5% 6% 6% 17%	5496
	11th to 20th	Night	2 14% 11% 21% 8% 5% 5% 4 7% 6% 17%	5469
	21st to end	Night	4 18% 9% 19% 8% 6% 5% 3 5% 5% 18%	5121
April	1st to 10th	Night	2 18% 9% 18% 10% 6% 5% 4 6% 6% 15%	2100
	11th to 20th	Night	3 16% 6% 14% 7% 7% 6% 5% 6% 7% 23%	1927
	21st to end	Night	6% 19% 5% 11% 6% 6% 6% 4 6% 6% 26%	1751
May	1st to 10th	Night	5% 16% 4 10% 6% 4 5% 4 7% 10% 31%	4724
	11th to 20th	Night	9% 20% 5% 12% 6% 6% 5% 4 7% 7% 18%	4283
	21st to end	Night	11% 18% 4 10% 5% 5% 5% 4 6% 7% 25%	4522
June	1st to 10th	Night	15% 14% 3 9% 8% 5% 5% 5% 5% 6% 26%	1288
	11th to 20th	Night	19% 13% 3 8% 8% 6% 6% 6% 6% 7% 18%	1260
	21st to end	Night	12% 10% 4 8% 7% 6% 6% 6% 7% 6% 28%	1260
July	1st to 10th	Night	15% 10% 3 6% 4 4 4 4 5% 8% 38%	3540
	11th to 20th	Night	16% 8% 2 6% 3 4 4 4 6% 7% 40%	3693
	21st to end	Night	17% 8% 3 6% 4 4 4 4 6% 8% 36%	5031
August	1st to 10th	Night	12% 8% 3 7% 4 5% 4 4 6% 8% 39%	3709
	11th to 20th	Night	11% 8% 3 8% 6% 5% 6% 5% 7% 9% 33%	3677
	21st to end	Night	16% 10% 3 8% 5% 5% 5% 4 6% 8% 30%	4665
September	1st to 10th	Night	14% 10% 3 7% 4 4 4 4 6% 7% 37%	2100
	11th to 20th	Night	13% 12% 3 8% 4 4 4 3 5% 6% 37%	2110
	21st to end	Night	12% 14% 3 8% 5% 6% 5% 4 6% 7% 30%	2200
October	1st to 10th	Night	7% 26% 7% 9% 5% 5% 5% 4 6% 6% 18%	3838
	11th to 20th	Night	10% 18% 9% 10% 5% 5% 4 4 6% 7% 23%	4174
	21st to end	Night	5% 19% 11% 14% 7% 4 4 3 4 7% 21%	4600
November	1st to 10th	Night	7% 19% 9% 14% 8% 8% 5% 4 6% 5% 14%	2775
	11th to 20th	Night	3 16% 7% 14% 10% 7% 6% 5% 7% 7% 17%	3148
	21st to end	Night	3 16% 7% 16% 10% 8% 6% 5% 5% 6% 17%	3150
December	1st to 10th	Night	5% 18% 9% 19% 9% 7% 8% 5% 5% 4 12%	5040
	11th to 20th	Night	3 17% 11% 20% 10% 7% 6% 5% 6% 5% 10%	5984
	21st to end	Night	2 17% 10% 18% 7% 5% 5% 4 7% 8% 18%	8140

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	75% 6% 9% 7% 2 1	3527
	11th to 20th	Day	54% 6% 10% 17% 9% 4	4258
	21st to end	Day	63% 8% 15% 10% 4	5187
February	1st to 10th	Day	67% 5% 8% 8% 9% 2	1680
	11th to 20th	Day	68% 5% 8% 12% 6% 1	1729
	21st to end	Day	67% 6% 9% 11% 5% 2	1730
March	1st to 10th	Day	67% 6% 8% 11% 8%	4618
	11th to 20th	Day	66% 6% 10% 14% 4	4750
	21st to end	Day	70% 6% 7% 11% 5% 1	6094
April	1st to 10th	Day	76% 6% 10% 7% 2	2520
	11th to 20th	Day	69% 7% 11% 10% 3	2644
	21st to end	Day	69% 7% 9% 13% 2	2866
May	1st to 10th	Day	52% 6% 20% 18% 4	8195
	11th to 20th	Day	63% 7% 14% 12% 3	8581
	21st to end	Day	63% 7% 17% 11% 3	9650
June	1st to 10th	Day	65% 6% 10% 12% 5% 1	3328
	11th to 20th	Day	71% 6% 11% 9% 3	3360
	21st to end	Day	64% 6% 13% 12% 4 1	3360
July	1st to 10th	Day	52% 5% 10% 19% 12% 2	9341
	11th to 20th	Day	48% 6% 9% 20% 15% 1	9177
	21st to end	Day	50% 6% 11% 20% 11% 2	8839
August	1st to 10th	Day	48% 6% 14% 24% 9%	6424
	11th to 20th	Day	53% 8% 14% 21% 4	6409
	21st to end	Day	51% 6% 14% 23% 5%	6483
September	1st to 10th	Day	54% 5% 14% 21% 5% 1	2520
	11th to 20th	Day	53% 5% 15% 17% 10%	2357
	21st to end	Day	60% 6% 13% 14% 6% 1	2200
October	1st to 10th	Day	64% 6% 14% 12% 4	3359
	11th to 20th	Day	64% 7% 13% 14% 2	2974
	21st to end	Day	62% 7% 16% 13% 3	3200
November	1st to 10th	Day	71% 7% 9% 9% 3 1	1722
	11th to 20th	Day	60% 10% 14% 10% 6% 1	1470
	21st to end	Day	63% 8% 13% 7% 4 4	1470
December	1st to 10th	Day	69% 11% 8% 7% 4 1	2360
	11th to 20th	Day	67% 8% 10% 10% 3 1	2426
	21st to end	Day	61% 8% 10% 13% 8%	3058
January	1st to 10th	Night	77% 7% 7% 5% 3 1	9367
	11th to 20th	Night	56% 6% 9% 12% 14% 3	8746
	21st to end	Night	66% 7% 11% 11% 4	8994
February	1st to 10th	Night	68% 6% 8% 8% 8% 3	2940
	11th to 20th	Night	65% 8% 8% 10% 7% 1	2782
	21st to end	Night	61% 7% 10% 15% 6% 2	2076
March	1st to 10th	Night	64% 7% 8% 13% 7% 1	5496
	11th to 20th	Night	65% 7% 11% 14% 3	5470
	21st to end	Night	66% 6% 9% 12% 7%	5121
April	1st to 10th	Night	69% 7% 12% 10% 2	2100
	11th to 20th	Night	60% 6% 16% 13% 5%	1927
	21st to end	Night	59% 8% 12% 16% 4	1751
May	1st to 10th	Night	48% 6% 24% 19% 2	4721
	11th to 20th	Night	61% 7% 12% 15% 4	4283
	21st to end	Night	55% 7% 21% 14% 2	4526
June	1st to 10th	Night	57% 8% 16% 12% 6% 1	1288
	11th to 20th	Night	64% 8% 13% 12% 3	1260
	21st to end	Night	53% 8% 19% 14% 4 1	1260
July	1st to 10th	Night	44% 6% 13% 24% 12% 1	3510
	11th to 20th	Night	42% 5% 11% 24% 18% 1	3657
	21st to end	Night	43% 6% 17% 23% 8% 2	4922
August	1st to 10th	Night	40% 8% 16% 31% 5%	3701
	11th to 20th	Night	42% 10% 23% 21% 3	3701
	21st to end	Night	50% 7% 20% 18% 4	4665
September	1st to 10th	Night	45% 6% 19% 22% 6% 1	2100
	11th to 20th	Night	48% 6% 17% 20% 8%	2110
	21st to end	Night	52% 9% 16% 16% 6% 1	2200
October	1st to 10th	Night	63% 9% 14% 11% 2	3838
	11th to 20th	Night	61% 6% 16% 14% 3	4174
	21st to end	Night	64% 7% 17% 9% 3	4600
November	1st to 10th	Night	71% 8% 10% 7% 3 1	2775
	11th to 20th	Night	64% 10% 10% 8% 6% 1	3148
	21st to end	Night	65% 9% 9% 9% 5% 3	3150
December	1st to 10th	Night	74% 8% 6% 6% 5% 1	5040
	11th to 20th	Night	73% 8% 8% 8% 3	5981
	21st to end	Night	64% 8% 11% 11% 5% 1	8140

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	15% 22% 36% 19% 6% 1	220
	11th to 20th	Day	18% 25% 32% 20% 3 2	220
	21st to end	Day	20% 25% 37% 13% 3 2	242
February	1st to 10th	Day	23% 22% 35% 14% 5% 2	220
	11th to 20th	Day	13% 26% 34% 20% 6% 1	301
	21st to end	Day	21% 25% 32% 15% 6% 1	446
March	1st to 10th	Day	23% 25% 30% 13% 8% 2	540
	11th to 20th	Day	21% 28% 29% 15% 4 2	540
	21st to end	Day	20% 27% 28% 17% 6% 2	594
April	1st to 10th	Day	25% 22% 32% 16% 5% 1	540
	11th to 20th	Day	19% 24% 30% 19% 7% 1	532
	21st to end	Day	22% 24% 26% 17% 8% 2	540
May	1st to 10th	Day	23% 17% 34% 17% 7% 2	543
	11th to 20th	Day	18% 15% 25% 27% 12% 3	712
	21st to end	Day	23% 14% 23% 24% 14% 3	844
June	1st to 10th	Day	27% 18% 30% 18% 6% 1	958
	11th to 20th	Day	28% 17% 27% 18% 8% 1	990
	21st to end	Day	24% 14% 26% 22% 12% 3	990
July	1st to 10th	Day	24% 15% 26% 23% 11% 1	976
	11th to 20th	Day	23% 15% 29% 24% 8% 2	920
	21st to end	Day	19% 16% 29% 23% 10% 3	660
August	1st to 10th	Day	21% 12% 31% 23% 10% 3	567
	11th to 20th	Day	22% 19% 33% 16% 8% 2	557
	21st to end	Day	24% 16% 30% 19% 8% 3	627
September	1st to 10th	Day	27% 18% 28% 19% 8% 1	570
	11th to 20th	Day	23% 21% 27% 22% 5% 2	543
	21st to end	Day	38% 26% 18% 13% 4 1	530
October	1st to 10th	Day	31% 21% 24% 15% 7% 2	530
	11th to 20th	Day	29% 24% 26% 14% 5% 1	359
	21st to end	Day	28% 21% 30% 16% 5%	363
November	1st to 10th	Day	32% 25% 27% 11% 4 1	271
	11th to 20th	Day	26% 25% 31% 13% 4 1	220
	21st to end	Day	20% 25% 26% 19% 8% 3	220
December	1st to 10th	Day	17% 30% 26% 17% 5% 4	220
	11th to 20th	Day	20% 29% 31% 15% 4 1	220
	21st to end	Day	14% 20% 36% 19% 7% 2	242
January	1st to 10th	Night	14% 23% 43% 16% 4 1	1160
	11th to 20th	Night	13% 23% 43% 16% 4 1	988
	21st to end	Night	13% 26% 41% 15% 5% 1	924
February	1st to 10th	Night	14% 20% 35% 24% 6% 1	840
	11th to 20th	Night	9% 20% 42% 23% 6%	824
	21st to end	Night	14% 14% 36% 25% 9% 1	692
March	1st to 10th	Night	11% 19% 39% 21% 9% 1	840
	11th to 20th	Night	10% 23% 40% 20% 6%	840
	21st to end	Night	9% 17% 33% 28% 11% 1	924
April	1st to 10th	Night	10% 19% 31% 30% 9% 1	840
	11th to 20th	Night	9% 14% 40% 24% 12% 1	679
	21st to end	Night	15% 14% 30% 31% 10% 1	491
May	1st to 10th	Night	16% 9% 25% 34% 14% 1	420
	11th to 20th	Night	12% 9% 23% 34% 20% 2	414
	21st to end	Night	19% 10% 23% 26% 20% 2	455
June	1st to 10th	Night	20% 7% 33% 25% 14% 1	420
	11th to 20th	Night	24% 9% 27% 26% 14%	420
	21st to end	Night	17% 8% 25% 30% 19% 1	420
July	1st to 10th	Night	20% 7% 23% 36% 13%	410
	11th to 20th	Night	20% 9% 23% 32% 15%	408
	21st to end	Night	15% 8% 20% 38% 19%	460
August	1st to 10th	Night	16% 5% 18% 37% 22% 2	418
	11th to 20th	Night	14% 9% 20% 36% 18% 1	416
	21st to end	Night	20% 10% 28% 29% 12% 1	727
September	1st to 10th	Night	20% 10% 29% 26% 14% 1	840
	11th to 20th	Night	18% 11% 25% 28% 16% 2	812
	21st to end	Night	24% 17% 28% 21% 8% 2	800
October	1st to 10th	Night	18% 16% 32% 23% 9% 1	800
	11th to 20th	Night	18% 17% 36% 23% 6% 1	800
	21st to end	Night	17% 19% 40% 18% 4	880
November	1st to 10th	Night	19% 23% 38% 14% 5%	820
	11th to 20th	Night	16% 24% 44% 13% 3 1	1048
	21st to end	Night	14% 21% 43% 16% 4 2	1050
December	1st to 10th	Night	14% 23% 40% 17% 6%	1050
	11th to 20th	Night	13% 24% 42% 15% 5%	1125
	21st to end	Night	10% 20% 45% 18% 6% 1	1276

Page generated at 2026-09-11 02:11:51. Version ac07

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