Canmore
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canmore clear sky chart from 2005-11-06 to 2026-07-01.

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	6% 9% 3 9% 6% 6% 6% 5% 7% 9% 35%	142185
	Night	3 7% 3 9% 6% 5% 6% 5% 8% 10% 39%	138887
Transparency	Day	39% 13% 18% 20% 9% 1	141897
	Night	35% 13% 21% 21% 9% 1	138758
Seeing	Day	19% 22% 32% 19% 7% 1	17389
	Night	11% 21% 38% 22% 7% 1	26422

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	2 3 14% 7% 7% 7% 6% 11% 12% 31%	4125
	11th to 20th	Day	4 3 9% 6% 6% 6% 5% 6% 8% 46%	4415
	21st to end	Day	3 2 8% 4 5% 5% 5% 9% 12% 45%	5186
February	1st to 10th	Day	1 6% 2 11% 9% 8% 7% 6% 10% 11% 30%	1680
	11th to 20th	Day	1 6% 3 12% 7% 8% 7% 6% 8% 10% 31%	1792
	21st to end	Day	7% 5% 14% 8% 8% 8% 7% 8% 9% 26%	1730
March	1st to 10th	Day	6% 5% 12% 8% 7% 6% 5% 6% 9% 37%	4618
	11th to 20th	Day	1 8% 4 10% 7% 6% 6% 5% 8% 10% 33%	4944
	21st to end	Day	3 17% 7% 17% 7% 6% 6% 4 6% 7% 20%	5844
April	1st to 10th	Day	3 14% 6% 15% 8% 7% 8% 5% 6% 6% 21%	2525
	11th to 20th	Day	4 16% 7% 15% 8% 5% 5% 4 6% 7% 22%	2700
	21st to end	Day	6% 17% 6% 12% 6% 6% 6% 4 6% 7% 23%	2730
May	1st to 10th	Day	7% 15% 3 7% 5% 4 5% 4 6% 7% 37%	8098
	11th to 20th	Day	7% 17% 5% 11% 7% 6% 7% 5% 7% 8% 21%	8689
	21st to end	Day	11% 10% 3 8% 6% 6% 6% 5% 6% 9% 29%	9649
June	1st to 10th	Day	16% 13% 4 8% 7% 6% 5% 4 6% 6% 25%	3150
	11th to 20th	Day	19% 12% 4 10% 8% 6% 6% 4 5% 6% 21%	3150
	21st to end	Day	12% 8% 3 9% 7% 6% 6% 6% 7% 8% 28%	3150
July	1st to 10th	Day	7% 6% 2 7% 5% 5% 6% 4 6% 7% 45%	6781
	11th to 20th	Day	10% 5% 2 6% 6% 5% 6% 5% 7% 8% 40%	6780
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 43%	7020
August	1st to 10th	Day	8% 6% 3 8% 6% 6% 6% 5% 7% 8% 38%	4541
	11th to 20th	Day	9% 4 2 6% 5% 5% 6% 5% 8% 9% 41%	4289
	21st to end	Day	9% 6% 2 6% 4 5% 4 4 6% 8% 46%	4664
September	1st to 10th	Day	8% 8% 3 7% 6% 5% 4 4 6% 7% 43%	2425
	11th to 20th	Day	9% 8% 2 8% 5% 4 4 4 6% 8% 41%	2233
	21st to end	Day	6% 7% 2 7% 6% 5% 5% 5% 7% 9% 40%	2200
October	1st to 10th	Day	5% 8% 3 7% 4 5% 5% 5% 7% 8% 43%	3508
	11th to 20th	Day	3 9% 3 8% 4 5% 6% 5% 8% 11% 39%	2932
	21st to end	Day	3 6% 3 7% 4 5% 5% 5% 7% 9% 45%	3200
November	1st to 10th	Day	2 11% 5% 10% 6% 6% 5% 5% 8% 11% 32%	1789
	11th to 20th	Day	1 5% 3 8% 5% 6% 7% 6% 10% 11% 39%	1531
	21st to end	Day	1 6% 3 9% 6% 6% 5% 6% 10% 12% 37%	1470
December	1st to 10th	Day	1 5% 4 8% 6% 5% 6% 6% 9% 12% 40%	2360
	11th to 20th	Day	1 5% 3 9% 6% 7% 7% 5% 9% 12% 38%	2712
	21st to end	Day	4 3 8% 6% 5% 7% 5% 8% 11% 42%	3575
January	1st to 10th	Night	4 4 15% 8% 7% 7% 5% 8% 11% 30%	8768
	11th to 20th	Night	3 3 9% 7% 6% 7% 6% 8% 11% 41%	8541
	21st to end	Night	4 3 8% 5% 5% 6% 6% 9% 11% 42%	8994
February	1st to 10th	Night	1 7% 3 10% 8% 8% 9% 7% 9% 10% 27%	2940
	11th to 20th	Night	6% 5% 13% 8% 5% 6% 6% 8% 10% 33%	2712
	21st to end	Night	6% 4 12% 9% 7% 7% 6% 8% 9% 31%	2076
March	1st to 10th	Night	7% 5% 11% 8% 7% 7% 5% 8% 10% 33%	5496
	11th to 20th	Night	1 7% 4 8% 5% 5% 5% 5% 8% 11% 40%	5274
	21st to end	Night	2 13% 7% 17% 6% 6% 5% 4 7% 10% 24%	5369
April	1st to 10th	Night	3 12% 6% 12% 7% 5% 5% 4 7% 9% 31%	2095
	11th to 20th	Night	3 13% 5% 13% 6% 4 5% 4 7% 8% 33%	1871
	21st to end	Night	4 13% 7% 11% 6% 6% 5% 4 6% 7% 32%	1890
May	1st to 10th	Night	8% 14% 3 6% 4 4 4 3 4 6% 44%	4811
	11th to 20th	Night	7% 13% 4 9% 5% 5% 5% 5% 7% 10% 30%	4169
	21st to end	Night	8% 7% 3 8% 5% 5% 5% 4 6% 9% 40%	4522
June	1st to 10th	Night	14% 9% 4 7% 6% 5% 5% 4 6% 7% 34%	1470
	11th to 20th	Night	16% 9% 3 7% 5% 4 4 4 6% 7% 33%	1470
	21st to end	Night	8% 5% 1 5% 5% 6% 5% 6% 8% 9% 42%	1470
July	1st to 10th	Night	6% 5% 2 5% 4 4 3 4 6% 8% 54%	3180
	11th to 20th	Night	10% 5% 2 4 3 3 4 4 6% 7% 52%	3180
	21st to end	Night	8% 6% 2 5% 3 3 4 3 5% 7% 54%	3822
August	1st to 10th	Night	9% 8% 2 8% 4 4 4 4 6% 8% 41%	2609
	11th to 20th	Night	7% 4 2 4 3 4 5% 4 7% 11% 50%	2765
	21st to end	Night	8% 6% 1 4 3 3 4 3 6% 9% 52%	3245
September	1st to 10th	Night	7% 7% 2 5% 3 3 4 4 5% 8% 53%	1973
	11th to 20th	Night	8% 7% 2 6% 4 3 4 4 7% 8% 45%	2166
	21st to end	Night	6% 9% 2 4 4 4 4 4 6% 9% 50%	2200
October	1st to 10th	Night	5% 9% 2 6% 4 4 5% 4 7% 9% 45%	3686
	11th to 20th	Night	3 7% 3 6% 4 5% 4 5% 7% 10% 47%	4216
	21st to end	Night	2 7% 3 8% 5% 4 5% 5% 8% 10% 44%	4600
November	1st to 10th	Night	2 10% 4 9% 6% 7% 6% 5% 9% 11% 31%	2707
	11th to 20th	Night	1 6% 3 8% 5% 6% 7% 6% 9% 13% 35%	3087
	21st to end	Night	7% 3 10% 7% 6% 6% 5% 9% 12% 35%	3150
December	1st to 10th	Night	1 6% 3 8% 6% 5% 6% 6% 9% 13% 40%	5040
	11th to 20th	Night	4 4 9% 7% 8% 8% 7% 10% 14% 28%	5700
	21st to end	Night	1 6% 3 9% 6% 6% 7% 6% 9% 13% 35%	7623

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	29% 19% 21% 20% 9% 1	4125
	11th to 20th	Day	30% 13% 21% 21% 12% 3	4438
	21st to end	Day	27% 14% 25% 22% 12%	5187
February	1st to 10th	Day	41% 16% 17% 15% 8% 3	1680
	11th to 20th	Day	43% 15% 16% 17% 8% 1	1800
	21st to end	Day	48% 14% 15% 15% 8% 1	1730
March	1st to 10th	Day	37% 14% 18% 13% 17% 1	4618
	11th to 20th	Day	34% 14% 24% 20% 8%	4945
	21st to end	Day	56% 13% 14% 10% 6%	5844
April	1st to 10th	Day	55% 15% 16% 10% 4	2525
	11th to 20th	Day	56% 12% 14% 13% 5%	2700
	21st to end	Day	56% 11% 14% 15% 4 1	2730
May	1st to 10th	Day	45% 8% 16% 24% 8%	8098
	11th to 20th	Day	50% 13% 16% 17% 4	8693
	21st to end	Day	43% 14% 20% 20% 3	9650
June	1st to 10th	Day	56% 10% 12% 15% 7% 1	3150
	11th to 20th	Day	59% 11% 11% 13% 5%	3150
	21st to end	Day	47% 13% 15% 17% 8% 1	3150
July	1st to 10th	Day	32% 10% 14% 21% 20% 3	6707
	11th to 20th	Day	36% 11% 16% 24% 11% 2	6699
	21st to end	Day	32% 10% 14% 23% 17% 2	6823
August	1st to 10th	Day	38% 11% 14% 25% 10% 1	4524
	11th to 20th	Day	34% 12% 20% 26% 7% 1	4331
	21st to end	Day	32% 10% 21% 27% 10% 1	4663
September	1st to 10th	Day	38% 9% 16% 23% 12% 2	2425
	11th to 20th	Day	39% 11% 15% 23% 12% 1	2233
	21st to end	Day	35% 15% 19% 22% 8% 1	2200
October	1st to 10th	Day	30% 15% 20% 27% 8%	3508
	11th to 20th	Day	32% 11% 23% 21% 11% 1	2932
	21st to end	Day	30% 11% 21% 30% 7%	3200
November	1st to 10th	Day	42% 15% 20% 15% 7% 1	1789
	11th to 20th	Day	31% 19% 25% 17% 7% 1	1531
	21st to end	Day	34% 17% 23% 18% 6% 2	1470
December	1st to 10th	Day	31% 17% 29% 16% 6% 1	2360
	11th to 20th	Day	31% 15% 28% 19% 5% 1	2714
	21st to end	Day	30% 11% 18% 24% 13% 3	3575
January	1st to 10th	Night	40% 15% 19% 18% 7% 1	8769
	11th to 20th	Night	31% 11% 22% 18% 12% 6%	8580
	21st to end	Night	29% 15% 23% 22% 10% 1	8994
February	1st to 10th	Night	42% 17% 16% 14% 9% 2	2940
	11th to 20th	Night	42% 13% 18% 16% 9% 2	2714
	21st to end	Night	42% 13% 16% 19% 10% 1	2076
March	1st to 10th	Night	37% 13% 23% 15% 11% 1	5496
	11th to 20th	Night	31% 12% 22% 23% 11%	5274
	21st to end	Night	51% 11% 16% 14% 7%	5369
April	1st to 10th	Night	46% 13% 19% 16% 6%	2095
	11th to 20th	Night	47% 11% 19% 17% 7%	1871
	21st to end	Night	48% 10% 16% 18% 6% 1	1890
May	1st to 10th	Night	41% 6% 14% 29% 9%	4808
	11th to 20th	Night	44% 9% 16% 28% 4	4169
	21st to end	Night	37% 10% 23% 23% 6%	4526
June	1st to 10th	Night	47% 10% 15% 21% 7%	1470
	11th to 20th	Night	49% 9% 16% 16% 10%	1470
	21st to end	Night	33% 12% 19% 26% 8% 1	1470
July	1st to 10th	Night	27% 10% 14% 28% 17% 3	3145
	11th to 20th	Night	29% 9% 20% 27% 13% 3	3138
	21st to end	Night	28% 8% 20% 24% 17% 4	3714
August	1st to 10th	Night	37% 10% 15% 28% 9% 1	2601
	11th to 20th	Night	26% 10% 31% 26% 7%	2789
	21st to end	Night	27% 8% 28% 29% 8%	3245
September	1st to 10th	Night	28% 8% 20% 30% 12% 2	1973
	11th to 20th	Night	34% 10% 17% 26% 11% 2	2166
	21st to end	Night	30% 10% 23% 26% 11%	2200
October	1st to 10th	Night	28% 13% 21% 26% 11%	3686
	11th to 20th	Night	27% 12% 23% 29% 9% 1	4216
	21st to end	Night	29% 13% 18% 32% 7%	4600
November	1st to 10th	Night	39% 18% 20% 16% 7% 1	2707
	11th to 20th	Night	33% 19% 22% 17% 9% 1	3087
	21st to end	Night	35% 17% 21% 18% 7% 3	3150
December	1st to 10th	Night	30% 16% 31% 16% 6% 1	5040
	11th to 20th	Night	35% 18% 26% 14% 6%	5697
	21st to end	Night	34% 13% 19% 20% 10% 3	7623

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	18% 20% 40% 15% 4 3	220
	11th to 20th	Day	13% 29% 38% 15% 5%	220
	21st to end	Day	13% 33% 38% 12% 4 2	242
February	1st to 10th	Day	25% 23% 33% 14% 5% 1	220
	11th to 20th	Day	11% 20% 45% 19% 4 1	310
	21st to end	Day	23% 24% 33% 16% 4 1	446
March	1st to 10th	Day	19% 30% 30% 15% 4 1	540
	11th to 20th	Day	20% 26% 35% 14% 4 2	540
	21st to end	Day	20% 28% 30% 16% 5% 2	594
April	1st to 10th	Day	19% 28% 35% 14% 4	540
	11th to 20th	Day	18% 26% 31% 17% 6% 1	532
	21st to end	Day	18% 24% 32% 18% 6% 2	540
May	1st to 10th	Day	19% 20% 31% 21% 8% 1	543
	11th to 20th	Day	19% 14% 27% 26% 12% 2	747
	21st to end	Day	24% 13% 25% 25% 10% 2	844
June	1st to 10th	Day	24% 19% 30% 20% 7% 1	780
	11th to 20th	Day	26% 21% 27% 19% 7% 1	780
	21st to end	Day	17% 17% 32% 22% 10% 2	780
July	1st to 10th	Day	16% 14% 32% 24% 13% 1	722
	11th to 20th	Day	16% 19% 31% 23% 9% 1	718
	21st to end	Day	10% 19% 33% 26% 9% 2	643
August	1st to 10th	Day	13% 17% 35% 25% 9% 2	527
	11th to 20th	Day	12% 21% 36% 24% 6% 1	517
	21st to end	Day	17% 19% 36% 21% 7% 2	583
September	1st to 10th	Day	19% 22% 33% 17% 8% 1	530
	11th to 20th	Day	18% 21% 36% 19% 5% 1	530
	21st to end	Day	28% 29% 26% 13% 3 1	530
October	1st to 10th	Day	22% 24% 31% 16% 7% 1	495
	11th to 20th	Day	22% 25% 31% 19% 2 1	330
	21st to end	Day	23% 29% 33% 10% 3 1	363
November	1st to 10th	Day	20% 32% 33% 10% 4 1	330
	11th to 20th	Day	19% 29% 41% 9% 3	251
	21st to end	Day	17% 26% 31% 15% 7% 3	220
December	1st to 10th	Day	16% 30% 34% 14% 5% 2	220
	11th to 20th	Day	15% 33% 36% 13% 3	220
	21st to end	Day	12% 28% 38% 17% 3 1	242
January	1st to 10th	Night	11% 30% 45% 11% 2	1050
	11th to 20th	Night	10% 28% 45% 13% 3 1	966
	21st to end	Night	8% 31% 43% 14% 3	924
February	1st to 10th	Night	12% 24% 39% 19% 6% 1	840
	11th to 20th	Night	8% 22% 46% 20% 5%	824
	21st to end	Night	12% 19% 41% 21% 7%	692
March	1st to 10th	Night	8% 23% 42% 21% 6%	840
	11th to 20th	Night	9% 23% 44% 18% 5%	840
	21st to end	Night	9% 20% 38% 23% 9% 1	924
April	1st to 10th	Night	11% 20% 35% 27% 6% 1	835
	11th to 20th	Night	9% 20% 36% 29% 7%	623
	21st to end	Night	13% 18% 37% 25% 7% 1	630
May	1st to 10th	Night	12% 12% 32% 34% 9%	455
	11th to 20th	Night	12% 9% 29% 32% 17% 1	414
	21st to end	Night	21% 9% 27% 25% 16% 2	455
June	1st to 10th	Night	19% 13% 34% 21% 11% 1	420
	11th to 20th	Night	21% 12% 32% 25% 10%	420
	21st to end	Night	11% 12% 27% 33% 16%	420
July	1st to 10th	Night	10% 7% 29% 38% 15% 1	390
	11th to 20th	Night	12% 12% 30% 33% 11% 1	388
	21st to end	Night	8% 8% 22% 45% 16%	438
August	1st to 10th	Night	10% 7% 21% 42% 19% 1	398
	11th to 20th	Night	11% 10% 24% 35% 18% 1	506
	21st to end	Night	12% 12% 29% 33% 14%	660
September	1st to 10th	Night	13% 12% 29% 32% 12% 2	773
	11th to 20th	Night	13% 14% 32% 27% 13% 3	800
	21st to end	Night	16% 22% 33% 20% 8% 1	800
October	1st to 10th	Night	14% 16% 38% 24% 8%	800
	11th to 20th	Night	14% 21% 38% 23% 5% 1	800
	21st to end	Night	14% 26% 39% 18% 4	880
November	1st to 10th	Night	13% 30% 41% 13% 3	862
	11th to 20th	Night	12% 31% 42% 12% 2 1	1050
	21st to end	Night	10% 30% 41% 16% 3 1	1050
December	1st to 10th	Night	10% 32% 38% 15% 5%	1050
	11th to 20th	Night	10% 29% 44% 13% 4	1050
	21st to end	Night	8% 28% 45% 14% 5%	1155

Page generated at 2026-06-28 00:10:46. Version ac07

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