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 2025-02-25.

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%	112230
	Night	3 7% 3 9% 6% 5% 6% 5% 8% 10% 38%	115105
Transparency	Day	41% 13% 17% 19% 9% 1	111983
	Night	36% 13% 20% 21% 9% 1	114998
Seeing	Day	18% 22% 32% 19% 7% 1	15528
	Night	11% 21% 37% 22% 8% 1	24780

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	3 2 14% 7% 7% 7% 6% 11% 11% 32%	3179
	11th to 20th	Day	4 4 11% 7% 7% 7% 5% 7% 9% 38%	3385
	21st to end	Day	3 2 7% 4 5% 5% 6% 10% 12% 46%	4004
February	1st to 10th	Day	1 6% 2 11% 9% 8% 7% 6% 10% 10% 29%	1600
	11th to 20th	Day	1 7% 3 12% 8% 8% 7% 6% 8% 10% 30%	1704
	21st to end	Day	8% 4 14% 9% 8% 8% 7% 8% 8% 25%	1611
March	1st to 10th	Day	4 4 13% 11% 8% 6% 5% 6% 9% 33%	3138
	11th to 20th	Day	2 9% 4 9% 6% 5% 6% 4 7% 10% 39%	3380
	21st to end	Day	1 18% 8% 18% 8% 6% 5% 4 6% 7% 19%	3992
April	1st to 10th	Day	3 15% 7% 15% 9% 7% 8% 5% 6% 6% 20%	2285
	11th to 20th	Day	5% 16% 6% 16% 8% 5% 5% 4 6% 7% 21%	2440
	21st to end	Day	6% 17% 6% 12% 6% 6% 6% 4 6% 7% 23%	2470
May	1st to 10th	Day	11% 22% 5% 9% 5% 4 5% 5% 5% 6% 23%	4375
	11th to 20th	Day	8% 14% 5% 11% 6% 5% 6% 5% 8% 8% 25%	4655
	21st to end	Day	15% 15% 5% 12% 7% 7% 7% 5% 6% 6% 16%	5161
June	1st to 10th	Day	17% 13% 4 8% 7% 6% 6% 4 6% 6% 23%	2850
	11th to 20th	Day	21% 13% 4 10% 8% 6% 6% 4 5% 5% 20%	2850
	21st to end	Day	11% 8% 3 8% 7% 6% 6% 5% 7% 8% 29%	2850
July	1st to 10th	Day	8% 6% 2 7% 6% 5% 6% 4 6% 7% 44%	4740
	11th to 20th	Day	6% 5% 2 6% 6% 5% 6% 5% 7% 7% 45%	4740
	21st to end	Day	4 4 2 5% 5% 5% 5% 5% 7% 9% 50%	4894
August	1st to 10th	Day	8% 6% 2 8% 6% 6% 6% 5% 7% 8% 38%	4401
	11th to 20th	Day	9% 4 2 6% 5% 5% 6% 5% 8% 9% 41%	4155
	21st to end	Day	9% 7% 2 6% 5% 5% 4 4 6% 8% 45%	4521
September	1st to 10th	Day	9% 9% 3 7% 6% 5% 4 4 6% 7% 43%	2304
	11th to 20th	Day	9% 8% 2 8% 5% 4 4 4 6% 8% 40%	2122
	21st to end	Day	6% 7% 2 7% 6% 5% 5% 5% 8% 9% 39%	2090
October	1st to 10th	Day	5% 9% 3 7% 4 5% 5% 5% 7% 8% 43%	3401
	11th to 20th	Day	3 9% 3 7% 4 5% 6% 5% 8% 11% 39%	2842
	21st to end	Day	3 7% 3 7% 4 5% 5% 5% 7% 9% 45%	3101
November	1st to 10th	Day	2 11% 5% 10% 6% 6% 5% 5% 8% 11% 33%	1702
	11th to 20th	Day	1 5% 3 8% 5% 6% 6% 7% 10% 12% 38%	1458
	21st to end	Day	1 6% 3 9% 6% 6% 5% 6% 10% 11% 38%	1400
December	1st to 10th	Day	1 5% 4 8% 6% 5% 6% 6% 8% 12% 40%	2290
	11th to 20th	Day	5% 3 9% 6% 7% 7% 5% 9% 12% 38%	2642
	21st to end	Day	4 3 8% 6% 5% 7% 5% 8% 11% 42%	3498
January	1st to 10th	Night	4 4 15% 8% 7% 7% 5% 9% 12% 27%	6766
	11th to 20th	Night	4 3 12% 8% 7% 7% 6% 8% 11% 33%	6557
	21st to end	Night	4 3 8% 5% 5% 6% 5% 9% 11% 42%	6952
February	1st to 10th	Night	1 7% 2 11% 8% 8% 9% 7% 9% 10% 28%	2800
	11th to 20th	Night	6% 5% 13% 8% 5% 6% 6% 8% 10% 32%	2580
	21st to end	Night	6% 4 12% 9% 7% 8% 6% 8% 9% 31%	1937
March	1st to 10th	Night	4 3 12% 10% 9% 7% 6% 8% 10% 31%	3736
	11th to 20th	Night	1 7% 4 8% 5% 5% 4 5% 8% 10% 45%	3598
	21st to end	Night	2 14% 8% 17% 6% 6% 5% 4 5% 8% 24%	3657
April	1st to 10th	Night	3 12% 5% 12% 7% 5% 5% 4 7% 9% 30%	1895
	11th to 20th	Night	3 13% 4 13% 6% 4 6% 4 7% 8% 33%	1691
	21st to end	Night	4 13% 7% 10% 5% 5% 5% 4 6% 7% 32%	1710
May	1st to 10th	Night	11% 21% 5% 8% 5% 4 4 3 5% 5% 30%	2585
	11th to 20th	Night	6% 9% 3 9% 6% 5% 6% 5% 8% 9% 34%	2236
	21st to end	Night	12% 10% 4 10% 6% 6% 5% 4 6% 7% 31%	2414
June	1st to 10th	Night	15% 9% 3 7% 6% 5% 5% 4 6% 7% 34%	1330
	11th to 20th	Night	17% 9% 4 8% 5% 5% 4 4 6% 7% 31%	1330
	21st to end	Night	8% 4 1 5% 5% 5% 5% 6% 8% 9% 43%	1330
July	1st to 10th	Night	5% 5% 2 5% 4 4 4 4 6% 8% 55%	2220
	11th to 20th	Night	5% 4 1 3 2 3 4 4 6% 8% 59%	2220
	21st to end	Night	3 4 1 4 4 3 4 4 5% 7% 62%	2657
August	1st to 10th	Night	9% 9% 3 8% 4 4 4 4 6% 8% 42%	2529
	11th to 20th	Night	7% 4 2 4 3 4 4 4 7% 11% 50%	2679
	21st to end	Night	8% 6% 1 4 3 3 4 3 6% 9% 51%	3146
September	1st to 10th	Night	8% 7% 2 5% 3 3 4 4 6% 8% 52%	1874
	11th to 20th	Night	9% 8% 3 6% 4 4 5% 4 7% 8% 44%	2057
	21st to end	Night	6% 9% 2 4 4 4 4 4 6% 9% 49%	2090
October	1st to 10th	Night	5% 9% 2 6% 4 4 5% 4 7% 9% 45%	3573
	11th to 20th	Night	3 7% 3 5% 4 5% 4 5% 7% 11% 47%	4086
	21st to end	Night	2 7% 3 8% 5% 4 5% 5% 8% 10% 43%	4457
November	1st to 10th	Night	2 10% 4 9% 6% 6% 6% 5% 9% 11% 31%	2575
	11th to 20th	Night	1 6% 4 8% 5% 6% 6% 7% 9% 13% 35%	2940
	21st to end	Night	7% 3 10% 7% 6% 6% 5% 9% 12% 34%	3000
December	1st to 10th	Night	1 6% 3 8% 5% 5% 6% 5% 9% 13% 41%	4890
	11th to 20th	Night	4 4 9% 7% 8% 7% 7% 10% 15% 28%	5550
	21st to end	Night	1 6% 3 9% 6% 6% 7% 6% 9% 13% 34%	7458

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	34% 18% 18% 20% 9% 1	3179
	11th to 20th	Day	37% 13% 18% 17% 11% 3	3408
	21st to end	Day	24% 16% 26% 22% 12% 1	4004
February	1st to 10th	Day	42% 16% 17% 15% 7% 3	1600
	11th to 20th	Day	43% 15% 16% 17% 7% 1	1712
	21st to end	Day	49% 14% 14% 14% 8% 1	1611
March	1st to 10th	Day	41% 16% 17% 12% 13% 1	3138
	11th to 20th	Day	33% 15% 27% 19% 5%	3381
	21st to end	Day	60% 14% 11% 10% 6%	3992
April	1st to 10th	Day	56% 15% 15% 9% 4	2285
	11th to 20th	Day	58% 12% 13% 13% 5%	2440
	21st to end	Day	58% 11% 14% 13% 4 1	2470
May	1st to 10th	Day	60% 9% 12% 16% 3	4375
	11th to 20th	Day	48% 14% 15% 19% 5%	4659
	21st to end	Day	58% 15% 14% 9% 3	5162
June	1st to 10th	Day	58% 10% 12% 14% 6% 1	2850
	11th to 20th	Day	62% 11% 11% 12% 5%	2850
	21st to end	Day	46% 13% 15% 16% 8% 1	2850
July	1st to 10th	Day	34% 9% 12% 17% 23% 5%	4666
	11th to 20th	Day	31% 11% 14% 26% 16% 3	4659
	21st to end	Day	26% 9% 13% 24% 25% 3	4739
August	1st to 10th	Day	38% 11% 14% 25% 10% 1	4384
	11th to 20th	Day	34% 12% 20% 26% 7% 1	4197
	21st to end	Day	32% 10% 21% 27% 9% 1	4520
September	1st to 10th	Day	39% 9% 15% 23% 12% 2	2304
	11th to 20th	Day	39% 11% 15% 22% 12% 1	2122
	21st to end	Day	35% 15% 19% 21% 8% 1	2090
October	1st to 10th	Day	30% 15% 19% 27% 8%	3401
	11th to 20th	Day	33% 11% 24% 21% 11% 1	2842
	21st to end	Day	31% 11% 21% 30% 7%	3101
November	1st to 10th	Day	42% 15% 21% 15% 7% 1	1702
	11th to 20th	Day	31% 19% 25% 17% 7% 1	1458
	21st to end	Day	34% 17% 24% 17% 6% 2	1400
December	1st to 10th	Day	31% 17% 29% 16% 6% 1	2290
	11th to 20th	Day	31% 15% 29% 19% 5% 1	2644
	21st to end	Day	31% 11% 18% 23% 13% 3	3498
January	1st to 10th	Night	44% 14% 17% 19% 5% 1	6766
	11th to 20th	Night	36% 12% 19% 16% 11% 6%	6596
	21st to end	Night	30% 15% 22% 21% 11% 1	6952
February	1st to 10th	Night	43% 17% 16% 14% 9% 2	2800
	11th to 20th	Night	42% 14% 18% 15% 8% 2	2582
	21st to end	Night	43% 13% 15% 18% 10% 1	1937
March	1st to 10th	Night	38% 16% 22% 14% 10% 1	3736
	11th to 20th	Night	30% 13% 26% 23% 7% 1	3598
	21st to end	Night	56% 10% 12% 17% 5% 1	3657
April	1st to 10th	Night	47% 13% 19% 15% 6%	1895
	11th to 20th	Night	48% 11% 18% 16% 7% 1	1691
	21st to end	Night	48% 10% 16% 18% 6% 1	1710
May	1st to 10th	Night	55% 8% 11% 22% 4	2585
	11th to 20th	Night	41% 10% 18% 27% 5%	2236
	21st to end	Night	48% 11% 17% 18% 6%	2414
June	1st to 10th	Night	48% 10% 15% 20% 6% 1	1330
	11th to 20th	Night	51% 8% 16% 15% 9%	1330
	21st to end	Night	32% 13% 19% 26% 9% 1	1330
July	1st to 10th	Night	26% 10% 14% 24% 21% 5%	2185
	11th to 20th	Night	21% 8% 18% 32% 16% 4	2178
	21st to end	Night	20% 7% 15% 29% 23% 5%	2573
August	1st to 10th	Night	37% 9% 15% 29% 9% 1	2521
	11th to 20th	Night	26% 10% 31% 26% 7%	2703
	21st to end	Night	27% 9% 28% 28% 7%	3146
September	1st to 10th	Night	29% 8% 20% 29% 12% 2	1874
	11th to 20th	Night	35% 10% 18% 24% 11% 2	2057
	21st to end	Night	30% 10% 23% 25% 11%	2090
October	1st to 10th	Night	28% 13% 21% 26% 12%	3573
	11th to 20th	Night	27% 12% 23% 30% 8% 1	4086
	21st to end	Night	30% 13% 18% 32% 7%	4457
November	1st to 10th	Night	39% 18% 19% 15% 6% 2	2575
	11th to 20th	Night	32% 19% 22% 17% 9% 1	2940
	21st to end	Night	36% 17% 21% 17% 7% 3	3000
December	1st to 10th	Night	29% 16% 32% 16% 6% 1	4890
	11th to 20th	Night	36% 18% 26% 14% 7%	5547
	21st to end	Night	34% 13% 19% 20% 11% 3	7458

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	16% 20% 41% 17% 4 3	200
	11th to 20th	Day	10% 31% 38% 16% 6% 1	200
	21st to end	Day	11% 34% 37% 12% 4 2	220
February	1st to 10th	Day	24% 24% 32% 15% 5% 2	200
	11th to 20th	Day	11% 20% 45% 19% 4 1	282
	21st to end	Day	20% 24% 35% 17% 4 1	399
March	1st to 10th	Day	15% 32% 31% 16% 4 2	460
	11th to 20th	Day	16% 27% 36% 16% 4 2	460
	21st to end	Day	16% 28% 32% 16% 5% 2	506
April	1st to 10th	Day	19% 28% 34% 15% 4	460
	11th to 20th	Day	18% 24% 31% 19% 7% 1	452
	21st to end	Day	19% 24% 33% 16% 6% 2	460
May	1st to 10th	Day	20% 18% 30% 22% 8% 2	463
	11th to 20th	Day	19% 12% 27% 27% 13% 2	649
	21st to end	Day	25% 12% 25% 25% 11% 2	734
June	1st to 10th	Day	23% 18% 30% 21% 7% 1	680
	11th to 20th	Day	27% 20% 27% 19% 7% 1	680
	21st to end	Day	17% 16% 32% 22% 11% 2	680
July	1st to 10th	Day	16% 13% 31% 24% 14% 1	671
	11th to 20th	Day	15% 20% 31% 23% 10% 1	668
	21st to end	Day	10% 19% 33% 27% 9% 2	596
August	1st to 10th	Day	14% 16% 35% 24% 9% 2	487
	11th to 20th	Day	12% 19% 37% 24% 7% 1	477
	21st to end	Day	18% 19% 35% 20% 6% 1	539
September	1st to 10th	Day	20% 24% 33% 15% 7% 1	490
	11th to 20th	Day	19% 22% 36% 16% 5% 1	490
	21st to end	Day	28% 29% 26% 14% 3 1	490
October	1st to 10th	Day	24% 23% 30% 16% 6% 1	457
	11th to 20th	Day	20% 26% 30% 20% 3 1	300
	21st to end	Day	22% 28% 34% 12% 4 1	330
November	1st to 10th	Day	18% 32% 34% 11% 4 1	300
	11th to 20th	Day	17% 29% 42% 8% 3	228
	21st to end	Day	17% 27% 30% 16% 8% 4	200
December	1st to 10th	Day	14% 31% 34% 15% 5% 2	200
	11th to 20th	Day	10% 34% 39% 14% 3 1	200
	21st to end	Day	12% 26% 39% 19% 4 1	220
January	1st to 10th	Night	10% 30% 45% 12% 2	1000
	11th to 20th	Night	8% 29% 45% 14% 3 1	920
	21st to end	Night	8% 32% 42% 14% 3	880
February	1st to 10th	Night	11% 24% 39% 19% 7% 1	800
	11th to 20th	Night	8% 21% 45% 20% 5%	784
	21st to end	Night	11% 18% 42% 22% 8%	646
March	1st to 10th	Night	6% 23% 44% 21% 6% 1	760
	11th to 20th	Night	8% 23% 43% 19% 6% 1	760
	21st to end	Night	8% 19% 38% 24% 10% 1	836
April	1st to 10th	Night	12% 19% 34% 28% 6% 1	755
	11th to 20th	Night	9% 18% 34% 30% 7% 1	563
	21st to end	Night	13% 18% 37% 25% 7% 1	570
May	1st to 10th	Night	13% 11% 32% 33% 10%	412
	11th to 20th	Night	12% 8% 28% 33% 18% 1	374
	21st to end	Night	23% 9% 24% 26% 17% 2	411
June	1st to 10th	Night	20% 13% 32% 22% 12% 1	380
	11th to 20th	Night	22% 13% 31% 25% 10%	380
	21st to end	Night	11% 13% 26% 33% 17% 1	380
July	1st to 10th	Night	10% 7% 28% 39% 15% 1	370
	11th to 20th	Night	12% 12% 30% 33% 12% 1	368
	21st to end	Night	8% 8% 21% 46% 16%	416
August	1st to 10th	Night	10% 7% 20% 42% 20% 1	378
	11th to 20th	Night	11% 9% 24% 35% 19% 1	480
	21st to end	Night	12% 12% 29% 31% 14%	627
September	1st to 10th	Night	14% 13% 31% 30% 12% 2	734
	11th to 20th	Night	13% 14% 33% 24% 13% 3	760
	21st to end	Night	16% 22% 32% 20% 8% 1	760
October	1st to 10th	Night	15% 15% 37% 24% 8%	760
	11th to 20th	Night	13% 21% 38% 23% 5% 1	760
	21st to end	Night	12% 25% 40% 19% 4	836
November	1st to 10th	Night	12% 30% 42% 13% 3	820
	11th to 20th	Night	11% 33% 42% 11% 2 1	1000
	21st to end	Night	10% 30% 40% 16% 3 1	1000
December	1st to 10th	Night	9% 32% 38% 16% 5%	1000
	11th to 20th	Night	8% 29% 45% 14% 4	1000
	21st to end	Night	8% 27% 45% 14% 5%	1100

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