Jasper Athabasca Glacier
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jasper Athabasca Glacier 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	5% 12% 6% 15% 8% 6% 6% 4 6% 7% 25%	154394
	Night	3 11% 6% 18% 10% 7% 6% 4 6% 7% 21%	145389
Transparency	Day	34% 37% 11% 13% 6% 1	154099
	Night	37% 38% 9% 10% 5% 1	145267
Seeing	Day	16% 19% 28% 23% 12% 3	18402
	Night	12% 18% 34% 23% 11% 1	26639

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	5% 5% 27% 15% 13% 9% 6% 8% 5% 8%	3622
	11th to 20th	Day	7% 3 16% 10% 7% 6% 5% 6% 5% 34%	4512
	21st to end	Day	9% 6% 30% 12% 7% 4 3 3 5% 21%	5186
February	1st to 10th	Day	1 12% 7% 26% 10% 7% 6% 4 5% 5% 15%	1680
	11th to 20th	Day	1 11% 7% 21% 12% 9% 7% 5% 6% 7% 14%	1746
	21st to end	Day	1 9% 6% 22% 16% 11% 8% 5% 6% 5% 12%	1730
March	1st to 10th	Day	8% 7% 22% 14% 9% 7% 5% 6% 8% 14%	4618
	11th to 20th	Day	1 9% 7% 24% 11% 7% 6% 5% 5% 5% 19%	4790
	21st to end	Day	1 12% 10% 25% 11% 7% 6% 5% 5% 5% 12%	6051
April	1st to 10th	Day	2 15% 9% 21% 12% 8% 7% 5% 5% 4 10%	2520
	11th to 20th	Day	2 17% 9% 18% 10% 8% 7% 4 4 6% 14%	2651
	21st to end	Day	3 19% 7% 18% 9% 7% 5% 4 6% 6% 16%	2830
May	1st to 10th	Day	3 15% 6% 11% 6% 5% 6% 4 7% 9% 29%	8195
	11th to 20th	Day	4 18% 7% 13% 6% 6% 7% 5% 8% 8% 16%	8569
	21st to end	Day	8% 16% 6% 12% 7% 5% 6% 4 6% 7% 22%	9649
June	1st to 10th	Day	14% 19% 6% 11% 7% 5% 6% 4 5% 6% 17%	3238
	11th to 20th	Day	14% 21% 6% 12% 6% 5% 5% 4 5% 7% 15%	3360
	21st to end	Day	11% 15% 5% 12% 7% 6% 5% 4 6% 6% 23%	3360
July	1st to 10th	Day	5% 7% 4 11% 6% 5% 5% 5% 6% 8% 38%	9420
	11th to 20th	Day	7% 7% 3 8% 5% 5% 5% 4 6% 8% 41%	9026
	21st to end	Day	5% 8% 4 10% 6% 5% 6% 4 6% 7% 39%	8986
August	1st to 10th	Day	6% 7% 3 8% 5% 5% 5% 4 7% 9% 42%	6441
	11th to 20th	Day	7% 8% 3 8% 7% 6% 6% 5% 7% 9% 34%	6349
	21st to end	Day	8% 10% 5% 11% 7% 6% 5% 4 5% 7% 32%	6461
September	1st to 10th	Day	7% 13% 4 11% 6% 6% 5% 4 6% 7% 31%	2520
	11th to 20th	Day	8% 16% 5% 10% 5% 4 4 4 6% 7% 31%	2342
	21st to end	Day	10% 22% 6% 11% 6% 5% 4 4 5% 6% 21%	2200
October	1st to 10th	Day	5% 15% 7% 17% 8% 6% 7% 5% 7% 7% 17%	3408
	11th to 20th	Day	6% 18% 9% 14% 7% 5% 5% 6% 6% 8% 16%	2965
	21st to end	Day	3 16% 7% 21% 10% 6% 5% 3 5% 6% 18%	3200
November	1st to 10th	Day	3 20% 11% 21% 11% 7% 4 4 4 4 11%	1764
	11th to 20th	Day	2 15% 8% 23% 12% 7% 5% 4 5% 4 15%	1470
	21st to end	Day	1 14% 8% 22% 12% 8% 6% 4 5% 5% 15%	1470
December	1st to 10th	Day	1 9% 6% 21% 10% 6% 6% 5% 7% 8% 20%	2360
	11th to 20th	Day	9% 7% 30% 15% 10% 5% 5% 6% 4 9%	2647
	21st to end	Day	6% 6% 25% 17% 10% 6% 4 5% 5% 16%	3058
January	1st to 10th	Night	6% 5% 28% 18% 10% 8% 5% 6% 5% 8%	9267
	11th to 20th	Night	6% 4 15% 10% 8% 8% 5% 7% 6% 30%	8445
	21st to end	Night	8% 8% 25% 12% 6% 5% 4 5% 6% 21%	8994
February	1st to 10th	Night	1 10% 7% 24% 11% 8% 6% 5% 7% 6% 15%	2940
	11th to 20th	Night	1 9% 8% 23% 13% 8% 6% 4 6% 5% 16%	2757
	21st to end	Night	9% 7% 20% 14% 9% 7% 5% 6% 7% 15%	2076
March	1st to 10th	Night	7% 6% 24% 11% 10% 9% 7% 8% 6% 13%	5496
	11th to 20th	Night	1 9% 7% 23% 11% 8% 8% 5% 6% 6% 15%	5429
	21st to end	Night	1 14% 10% 24% 12% 7% 6% 4 5% 5% 11%	5165
April	1st to 10th	Night	2 13% 10% 24% 11% 7% 6% 4 5% 6% 13%	2100
	11th to 20th	Night	1 18% 8% 17% 10% 7% 6% 5% 7% 6% 16%	1920
	21st to end	Night	4 16% 7% 15% 8% 6% 5% 5% 6% 7% 21%	1787
May	1st to 10th	Night	4 16% 5% 10% 5% 5% 5% 4 7% 9% 30%	4724
	11th to 20th	Night	5% 17% 7% 15% 7% 6% 6% 5% 7% 9% 16%	4289
	21st to end	Night	6% 16% 7% 10% 6% 5% 6% 4 6% 7% 27%	4522
June	1st to 10th	Night	14% 19% 5% 10% 4 5% 6% 4 7% 7% 20%	1378
	11th to 20th	Night	15% 21% 6% 14% 6% 5% 5% 5% 7% 6% 12%	1260
	21st to end	Night	12% 14% 5% 12% 7% 5% 5% 4 5% 7% 24%	1260
July	1st to 10th	Night	7% 10% 4 9% 5% 5% 5% 4 6% 6% 38%	3540
	11th to 20th	Night	7% 7% 3 7% 5% 5% 5% 4 6% 7% 44%	3918
	21st to end	Night	9% 10% 4 8% 5% 5% 4 3 6% 7% 38%	5067
August	1st to 10th	Night	7% 8% 3 10% 6% 6% 5% 4 6% 7% 37%	3709
	11th to 20th	Night	7% 6% 3 7% 5% 6% 7% 5% 8% 11% 34%	3696
	21st to end	Night	8% 11% 5% 13% 7% 5% 5% 4 5% 7% 30%	4690
September	1st to 10th	Night	10% 15% 6% 9% 4 4 4 3 6% 7% 33%	2100
	11th to 20th	Night	9% 16% 5% 10% 5% 5% 3 3 5% 7% 32%	2125
	21st to end	Night	9% 18% 7% 11% 4 5% 5% 3 5% 7% 25%	2200
October	1st to 10th	Night	4 14% 7% 16% 7% 6% 6% 5% 7% 7% 21%	3791
	11th to 20th	Night	5% 18% 8% 14% 6% 5% 5% 5% 7% 9% 18%	4184
	21st to end	Night	2 15% 8% 19% 9% 6% 5% 4 5% 8% 18%	4600
November	1st to 10th	Night	3 21% 10% 23% 11% 6% 5% 3 4 5% 10%	2738
	11th to 20th	Night	1 15% 8% 25% 14% 7% 5% 4 4 4 13%	3145
	21st to end	Night	1 13% 8% 22% 13% 8% 7% 4 5% 5% 13%	3150
December	1st to 10th	Night	1 11% 7% 22% 12% 9% 7% 4 6% 7% 14%	5040
	11th to 20th	Night	6% 8% 30% 15% 11% 8% 5% 6% 4 8%	5747
	21st to end	Night	8% 6% 25% 15% 10% 6% 5% 7% 7% 11%	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	54% 28% 9% 5% 2 1	3622
	11th to 20th	Day	32% 24% 10% 16% 13% 5%	4536
	21st to end	Day	44% 29% 10% 9% 7%	5187
February	1st to 10th	Day	25% 60% 4 4 7% 1	1680
	11th to 20th	Day	23% 60% 7% 5% 4 1	1754
	21st to end	Day	27% 60% 3 6% 3 2	1730
March	1st to 10th	Day	41% 34% 9% 7% 8% 1	4618
	11th to 20th	Day	43% 33% 10% 12% 3	4790
	21st to end	Day	50% 32% 8% 6% 4 1	6051
April	1st to 10th	Day	30% 60% 5% 3 1	2520
	11th to 20th	Day	27% 61% 8% 3 1	2651
	21st to end	Day	27% 60% 5% 7% 1	2830
May	1st to 10th	Day	33% 27% 19% 16% 5%	8195
	11th to 20th	Day	47% 28% 12% 11% 2	8573
	21st to end	Day	44% 27% 16% 11% 2	9650
June	1st to 10th	Day	22% 61% 7% 7% 3	3238
	11th to 20th	Day	24% 60% 5% 8% 3	3360
	21st to end	Day	22% 61% 5% 9% 3	3360
July	1st to 10th	Day	25% 24% 12% 23% 15% 1	9341
	11th to 20th	Day	28% 24% 8% 20% 18% 1	8941
	21st to end	Day	28% 26% 14% 21% 9% 1	8791
August	1st to 10th	Day	25% 30% 10% 27% 7%	6424
	11th to 20th	Day	28% 33% 16% 21% 3	6391
	21st to end	Day	32% 33% 13% 17% 5%	6460
September	1st to 10th	Day	21% 56% 9% 10% 3 1	2520
	11th to 20th	Day	25% 57% 6% 8% 5%	2342
	21st to end	Day	27% 59% 6% 5% 3 1	2200
October	1st to 10th	Day	36% 43% 13% 6% 2	3408
	11th to 20th	Day	39% 40% 10% 9% 1	2965
	21st to end	Day	37% 42% 11% 8% 2	3200
November	1st to 10th	Day	31% 57% 5% 4 3	1764
	11th to 20th	Day	27% 57% 8% 4 4 1	1470
	21st to end	Day	26% 57% 8% 4 3 3	1470
December	1st to 10th	Day	39% 41% 13% 4 2 1	2360
	11th to 20th	Day	51% 37% 6% 4 2	2649
	21st to end	Day	41% 34% 9% 9% 6% 1	3058
January	1st to 10th	Night	59% 26% 7% 4 2 1	9268
	11th to 20th	Night	32% 26% 9% 13% 14% 5%	8483
	21st to end	Night	43% 28% 11% 11% 6%	8994
February	1st to 10th	Night	24% 60% 4 4 5% 2	2940
	11th to 20th	Night	21% 61% 8% 4 4 1	2759
	21st to end	Night	24% 60% 5% 7% 3 2	2076
March	1st to 10th	Night	41% 35% 12% 6% 5% 1	5496
	11th to 20th	Night	41% 35% 9% 12% 2	5430
	21st to end	Night	52% 31% 6% 6% 3 1	5165
April	1st to 10th	Night	22% 64% 6% 6% 2	2100
	11th to 20th	Night	22% 61% 8% 6% 2	1920
	21st to end	Night	21% 61% 6% 7% 4	1787
May	1st to 10th	Night	32% 26% 17% 22% 3	4721
	11th to 20th	Night	48% 27% 11% 12% 2	4289
	21st to end	Night	38% 28% 18% 14% 2	4526
June	1st to 10th	Night	21% 60% 8% 7% 3	1378
	11th to 20th	Night	23% 61% 5% 7% 4	1260
	21st to end	Night	20% 59% 7% 10% 3	1260
July	1st to 10th	Night	34% 24% 11% 17% 15% 1	3510
	11th to 20th	Night	27% 23% 7% 23% 19% 1	3880
	21st to end	Night	34% 24% 10% 21% 11% 1	4957
August	1st to 10th	Night	30% 30% 10% 24% 5% 1	3701
	11th to 20th	Night	29% 32% 16% 21% 2	3720
	21st to end	Night	37% 30% 14% 15% 3	4690
September	1st to 10th	Night	22% 57% 8% 9% 4 1	2100
	11th to 20th	Night	23% 57% 5% 10% 4	2125
	21st to end	Night	25% 59% 7% 5% 3	2200
October	1st to 10th	Night	39% 45% 8% 5% 2	3791
	11th to 20th	Night	36% 41% 9% 11% 3	4184
	21st to end	Night	33% 44% 12% 8% 2 1	4600
November	1st to 10th	Night	34% 55% 3 5% 2 1	2738
	11th to 20th	Night	28% 58% 6% 3 4 1	3145
	21st to end	Night	26% 57% 7% 4 3 3	3150
December	1st to 10th	Night	46% 40% 7% 4 3	5040
	11th to 20th	Night	51% 37% 5% 6% 2	5744
	21st to end	Night	48% 32% 8% 7% 4 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	12% 24% 30% 21% 10% 2	220
	11th to 20th	Day	12% 27% 34% 17% 8% 2	220
	21st to end	Day	16% 26% 38% 13% 4 3	242
February	1st to 10th	Day	16% 31% 28% 15% 7% 3	220
	11th to 20th	Day	10% 23% 35% 21% 8% 3	313
	21st to end	Day	18% 24% 31% 19% 7% 1	446
March	1st to 10th	Day	18% 25% 30% 16% 9% 2	540
	11th to 20th	Day	14% 27% 32% 18% 6% 2	540
	21st to end	Day	15% 28% 28% 19% 7% 2	594
April	1st to 10th	Day	17% 22% 35% 19% 6% 1	540
	11th to 20th	Day	12% 28% 29% 20% 9% 2	532
	21st to end	Day	13% 22% 32% 20% 10% 3	540
May	1st to 10th	Day	17% 18% 30% 22% 11% 2	543
	11th to 20th	Day	14% 11% 24% 29% 16% 5%	704
	21st to end	Day	17% 15% 20% 25% 19% 5%	844
June	1st to 10th	Day	20% 15% 29% 23% 12% 1	868
	11th to 20th	Day	19% 14% 26% 26% 13% 2	990
	21st to end	Day	15% 9% 23% 28% 19% 5%	990
July	1st to 10th	Day	13% 9% 24% 32% 18% 4	976
	11th to 20th	Day	12% 10% 26% 29% 19% 5%	840
	21st to end	Day	8% 12% 24% 30% 18% 7%	650
August	1st to 10th	Day	10% 10% 20% 35% 19% 6%	567
	11th to 20th	Day	11% 12% 29% 32% 12% 4	557
	21st to end	Day	13% 15% 28% 24% 14% 5%	627
September	1st to 10th	Day	16% 19% 25% 23% 14% 2	570
	11th to 20th	Day	17% 16% 28% 26% 11% 2	543
	21st to end	Day	25% 26% 29% 14% 6% 1	530
October	1st to 10th	Day	22% 23% 28% 17% 8% 3	530
	11th to 20th	Day	20% 28% 25% 17% 9% 1	350
	21st to end	Day	19% 29% 28% 17% 6% 2	363
November	1st to 10th	Day	18% 34% 27% 13% 5% 2	291
	11th to 20th	Day	19% 25% 35% 16% 5% 1	220
	21st to end	Day	17% 24% 30% 17% 8% 5%	220
December	1st to 10th	Day	15% 25% 29% 16% 10% 5%	220
	11th to 20th	Day	15% 30% 31% 18% 5% 1	220
	21st to end	Day	12% 19% 37% 19% 10% 2	242
January	1st to 10th	Night	10% 26% 39% 19% 5% 1	1141
	11th to 20th	Night	10% 24% 42% 17% 5% 1	934
	21st to end	Night	6% 26% 43% 18% 6% 1	924
February	1st to 10th	Night	8% 24% 36% 23% 8% 2	840
	11th to 20th	Night	7% 19% 43% 23% 8% 1	824
	21st to end	Night	12% 15% 35% 25% 12% 2	692
March	1st to 10th	Night	8% 22% 37% 23% 10% 1	840
	11th to 20th	Night	8% 20% 42% 24% 6% 1	840
	21st to end	Night	9% 17% 39% 22% 12% 2	924
April	1st to 10th	Night	8% 16% 36% 28% 12% 1	840
	11th to 20th	Night	8% 15% 39% 27% 11% 1	672
	21st to end	Night	12% 16% 31% 27% 13% 1	527
May	1st to 10th	Night	14% 11% 27% 33% 14% 2	420
	11th to 20th	Night	12% 7% 26% 33% 20% 1	414
	21st to end	Night	20% 11% 21% 26% 19% 4	455
June	1st to 10th	Night	22% 12% 27% 25% 11% 3	420
	11th to 20th	Night	23% 14% 22% 24% 14% 2	420
	21st to end	Night	17% 8% 19% 28% 24% 5%	420
July	1st to 10th	Night	17% 4 22% 29% 23% 4	410
	11th to 20th	Night	15% 10% 20% 30% 23% 2	408
	21st to end	Night	10% 8% 18% 37% 25% 3	460
August	1st to 10th	Night	13% 6% 14% 37% 26% 4	418
	11th to 20th	Night	13% 5% 20% 33% 26% 3	422
	21st to end	Night	15% 10% 24% 34% 16% 1	740
September	1st to 10th	Night	18% 10% 26% 27% 17% 2	840
	11th to 20th	Night	16% 11% 20% 31% 17% 4	812
	21st to end	Night	21% 20% 27% 20% 9% 2	800
October	1st to 10th	Night	19% 15% 32% 24% 10% 1	800
	11th to 20th	Night	17% 21% 31% 24% 6% 1	800
	21st to end	Night	16% 23% 38% 17% 6% 1	880
November	1st to 10th	Night	15% 29% 34% 16% 6%	820
	11th to 20th	Night	13% 25% 41% 17% 4	1045
	21st to end	Night	11% 23% 41% 18% 5% 2	1050
December	1st to 10th	Night	10% 24% 42% 16% 9% 1	1050
	11th to 20th	Night	10% 24% 41% 18% 7%	1061
	21st to end	Night	7% 23% 42% 20% 8% 1	1276

Page generated at 2026-09-11 02:11:56. Version ac07

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