Crowsnest Pass
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crowsnest Pass 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	5% 8% 3 9% 6% 6% 6% 5% 7% 8% 36%	141913
	Night	3 8% 4 9% 7% 7% 6% 5% 8% 8% 35%	139161
Transparency	Day	35% 12% 18% 22% 11% 2	141626
	Night	34% 14% 20% 21% 9% 2	139031
Seeing	Day	21% 23% 29% 18% 8% 2	17400
	Night	16% 21% 30% 23% 10% 1	26523

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 6% 6% 14% 11% 13% 9% 6% 9% 8% 19%	4125
	11th to 20th	Day	4 4 12% 9% 8% 5% 5% 8% 9% 34%	4533
	21st to end	Day	1 6% 3 9% 8% 8% 7% 7% 9% 7% 36%	5186
February	1st to 10th	Day	2 9% 5% 13% 9% 8% 9% 6% 9% 11% 19%	1688
	11th to 20th	Day	2 13% 6% 15% 8% 6% 6% 6% 7% 8% 22%	1859
	21st to end	Day	2 11% 6% 16% 9% 7% 7% 6% 9% 7% 22%	1730
March	1st to 10th	Day	1 8% 5% 13% 7% 7% 6% 4 8% 8% 33%	4618
	11th to 20th	Day	1 10% 6% 13% 10% 8% 7% 5% 6% 5% 28%	5019
	21st to end	Day	3 18% 7% 18% 9% 7% 6% 4 7% 6% 16%	5730
April	1st to 10th	Day	4 15% 5% 13% 8% 6% 6% 5% 8% 7% 22%	2536
	11th to 20th	Day	5% 16% 6% 13% 7% 5% 6% 4 7% 7% 24%	2700
	21st to end	Day	8% 15% 5% 10% 6% 6% 5% 5% 6% 7% 28%	2730
May	1st to 10th	Day	8% 14% 3 8% 5% 4 4 4 5% 7% 37%	7796
	11th to 20th	Day	7% 11% 3 10% 8% 9% 7% 6% 8% 8% 22%	8595
	21st to end	Day	11% 8% 2 6% 5% 6% 6% 6% 8% 10% 32%	9649
June	1st to 10th	Day	14% 10% 4 9% 8% 5% 6% 4 7% 6% 28%	3150
	11th to 20th	Day	14% 10% 3 10% 7% 5% 6% 5% 7% 7% 25%	3150
	21st to end	Day	8% 7% 3 7% 6% 5% 5% 5% 7% 8% 39%	3150
July	1st to 10th	Day	5% 3 2 5% 4 4 5% 4 6% 8% 55%	6781
	11th to 20th	Day	6% 3 1 4 4 4 5% 4 7% 8% 55%	6780
	21st to end	Day	6% 3 1 3 3 3 4 3 7% 9% 58%	6926
August	1st to 10th	Day	7% 6% 2 5% 5% 5% 6% 4 7% 8% 44%	4541
	11th to 20th	Day	5% 4 1 5% 3 4 5% 4 6% 7% 55%	4167
	21st to end	Day	6% 4 1 5% 3 4 4 4 6% 8% 55%	4664
September	1st to 10th	Day	9% 7% 2 5% 3 4 5% 3 6% 7% 48%	2432
	11th to 20th	Day	10% 6% 3 5% 4 4 5% 5% 7% 9% 44%	2200
	21st to end	Day	7% 8% 3 6% 4 5% 6% 3 6% 7% 45%	2200
October	1st to 10th	Day	5% 8% 3 7% 4 4 4 3 5% 7% 50%	3509
	11th to 20th	Day	2 7% 2 8% 6% 7% 6% 5% 8% 10% 39%	3002
	21st to end	Day	4 9% 4 8% 8% 10% 7% 4 6% 8% 33%	3200
November	1st to 10th	Day	5% 12% 5% 13% 8% 7% 7% 6% 7% 8% 23%	1807
	11th to 20th	Day	2 8% 5% 9% 8% 7% 7% 6% 10% 10% 29%	1643
	21st to end	Day	2 10% 3 10% 8% 8% 8% 5% 10% 10% 26%	1470
December	1st to 10th	Day	1 7% 4 9% 5% 7% 6% 6% 11% 11% 33%	2360
	11th to 20th	Day	1 8% 4 11% 11% 11% 7% 6% 11% 9% 20%	2712
	21st to end	Day	1 7% 5% 11% 7% 9% 9% 6% 9% 11% 25%	3575
January	1st to 10th	Night	1 7% 5% 14% 9% 11% 10% 7% 10% 8% 18%	8768
	11th to 20th	Night	4 3 11% 9% 8% 7% 5% 7% 10% 36%	8422
	21st to end	Night	9% 4 10% 7% 8% 7% 6% 8% 8% 34%	8994
February	1st to 10th	Night	2 9% 5% 12% 9% 8% 8% 7% 9% 9% 21%	2931
	11th to 20th	Night	1 11% 6% 13% 8% 7% 7% 5% 9% 8% 25%	2646
	21st to end	Night	1 9% 4 13% 9% 8% 8% 5% 9% 8% 25%	2076
March	1st to 10th	Night	1 8% 5% 14% 8% 7% 6% 4 7% 8% 31%	5496
	11th to 20th	Night	1 7% 4 8% 9% 11% 8% 6% 8% 7% 32%	5200
	21st to end	Night	4 16% 8% 16% 8% 9% 6% 5% 6% 6% 16%	5483
April	1st to 10th	Night	5% 11% 5% 8% 5% 5% 7% 5% 9% 8% 32%	2084
	11th to 20th	Night	5% 11% 4 10% 7% 4 5% 5% 7% 8% 32%	1871
	21st to end	Night	5% 14% 4 8% 6% 6% 5% 3 8% 8% 34%	1890
May	1st to 10th	Night	8% 12% 2 7% 4 4 5% 4 5% 6% 43%	5129
	11th to 20th	Night	7% 10% 4 9% 6% 6% 6% 6% 7% 9% 31%	4251
	21st to end	Night	10% 9% 3 6% 5% 6% 6% 4 7% 7% 38%	4522
June	1st to 10th	Night	10% 10% 3 8% 5% 6% 6% 6% 7% 7% 33%	1470
	11th to 20th	Night	12% 9% 2 7% 4 6% 7% 5% 7% 8% 33%	1470
	21st to end	Night	5% 5% 2 6% 4 4 6% 5% 7% 8% 48%	1470
July	1st to 10th	Night	5% 2 1 4 4 5% 4 3 5% 6% 60%	3180
	11th to 20th	Night	5% 4 1 4 3 3 4 4 6% 7% 59%	3180
	21st to end	Night	7% 10% 1 3 2 2 3 3 4 5% 59%	3913
August	1st to 10th	Night	9% 10% 2 4 3 3 3 3 4 6% 54%	2609
	11th to 20th	Night	4 3 1 5% 4 4 5% 4 8% 10% 52%	2892
	21st to end	Night	4 4 1 3 3 4 5% 4 6% 9% 56%	3245
September	1st to 10th	Night	6% 6% 1 4 3 3 4 4 6% 7% 57%	1963
	11th to 20th	Night	7% 7% 2 5% 4 4 5% 4 6% 9% 47%	2200
	21st to end	Night	6% 9% 2 6% 4 4 3 4 6% 9% 46%	2200
October	1st to 10th	Night	5% 6% 1 5% 4 6% 5% 3 6% 9% 50%	3687
	11th to 20th	Night	2 5% 2 6% 6% 7% 5% 5% 7% 10% 45%	4142
	21st to end	Night	2 7% 3 8% 7% 10% 6% 5% 7% 10% 35%	4600
November	1st to 10th	Night	5% 12% 4 10% 7% 6% 7% 5% 10% 10% 25%	2690
	11th to 20th	Night	2 8% 4 12% 8% 8% 7% 7% 10% 10% 25%	2974
	21st to end	Night	2 10% 3 10% 7% 10% 7% 6% 10% 11% 25%	3150
December	1st to 10th	Night	1 6% 4 8% 6% 6% 7% 5% 11% 12% 34%	5040
	11th to 20th	Night	1 10% 6% 14% 9% 11% 9% 6% 10% 9% 16%	5700
	21st to end	Night	1 9% 5% 13% 9% 12% 8% 6% 9% 8% 21%	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	38% 21% 21% 15% 5% 1	4125
	11th to 20th	Day	38% 12% 20% 17% 10% 3	4557
	21st to end	Day	30% 17% 21% 21% 11%	5187
February	1st to 10th	Day	42% 19% 18% 11% 7% 1	1688
	11th to 20th	Day	46% 14% 20% 14% 5% 1	1868
	21st to end	Day	44% 15% 20% 14% 5% 2	1730
March	1st to 10th	Day	30% 15% 22% 18% 13% 2	4618
	11th to 20th	Day	34% 17% 22% 20% 7%	5020
	21st to end	Day	54% 15% 17% 9% 5%	5730
April	1st to 10th	Day	46% 14% 19% 17% 4	2536
	11th to 20th	Day	48% 12% 19% 16% 4	2700
	21st to end	Day	47% 11% 17% 19% 5% 1	2730
May	1st to 10th	Day	44% 8% 11% 25% 12%	7796
	11th to 20th	Day	41% 14% 15% 22% 7%	8599
	21st to end	Day	36% 12% 22% 23% 7%	9650
June	1st to 10th	Day	47% 11% 15% 18% 7% 1	3150
	11th to 20th	Day	48% 11% 16% 16% 9% 1	3150
	21st to end	Day	34% 10% 18% 24% 12% 1	3150
July	1st to 10th	Day	24% 7% 13% 24% 24% 8%	6707
	11th to 20th	Day	25% 7% 14% 27% 21% 6%	6699
	21st to end	Day	21% 5% 15% 29% 19% 10%	6731
August	1st to 10th	Day	34% 7% 14% 22% 18% 5%	4524
	11th to 20th	Day	25% 7% 19% 34% 13% 2	4206
	21st to end	Day	23% 7% 15% 38% 15% 2	4663
September	1st to 10th	Day	31% 7% 17% 24% 15% 5%	2432
	11th to 20th	Day	32% 9% 16% 27% 14% 2	2200
	21st to end	Day	30% 10% 23% 25% 11% 1	2200
October	1st to 10th	Day	30% 9% 22% 33% 7%	3509
	11th to 20th	Day	27% 13% 24% 21% 14% 1	3002
	21st to end	Day	32% 14% 21% 23% 9% 1	3200
November	1st to 10th	Day	43% 15% 21% 15% 5% 1	1807
	11th to 20th	Day	30% 22% 26% 15% 5%	1643
	21st to end	Day	38% 19% 22% 14% 6% 1	1470
December	1st to 10th	Day	30% 18% 26% 20% 5% 1	2360
	11th to 20th	Day	36% 22% 27% 12% 3	2714
	21st to end	Day	33% 17% 19% 21% 9% 1	3575
January	1st to 10th	Night	39% 19% 21% 17% 4	8769
	11th to 20th	Night	33% 12% 23% 18% 9% 4	8460
	21st to end	Night	31% 18% 21% 21% 9%	8994
February	1st to 10th	Night	44% 16% 18% 13% 7% 2	2931
	11th to 20th	Night	41% 16% 20% 15% 7% 1	2647
	21st to end	Night	41% 15% 18% 18% 6% 1	2076
March	1st to 10th	Night	37% 15% 19% 17% 10% 2	5496
	11th to 20th	Night	28% 18% 24% 22% 8%	5200
	21st to end	Night	51% 14% 21% 10% 4	5483
April	1st to 10th	Night	40% 13% 21% 18% 7%	2084
	11th to 20th	Night	41% 10% 20% 25% 5%	1871
	21st to end	Night	43% 11% 17% 22% 6% 1	1890
May	1st to 10th	Night	39% 7% 15% 28% 11%	5126
	11th to 20th	Night	37% 12% 17% 27% 7%	4251
	21st to end	Night	35% 12% 21% 25% 7%	4526
June	1st to 10th	Night	41% 10% 22% 20% 6% 1	1470
	11th to 20th	Night	42% 10% 18% 20% 10% 1	1470
	21st to end	Night	28% 10% 20% 29% 12% 1	1470
July	1st to 10th	Night	22% 6% 17% 26% 23% 6%	3145
	11th to 20th	Night	23% 6% 18% 27% 19% 7%	3138
	21st to end	Night	27% 5% 15% 24% 19% 10%	3803
August	1st to 10th	Night	32% 6% 14% 25% 20% 4	2601
	11th to 20th	Night	25% 7% 24% 28% 15% 2	2919
	21st to end	Night	20% 8% 16% 37% 18% 1	3245
September	1st to 10th	Night	24% 7% 16% 32% 15% 6%	1963
	11th to 20th	Night	29% 9% 18% 28% 13% 2	2200
	21st to end	Night	28% 10% 23% 25% 12% 2	2200
October	1st to 10th	Night	25% 9% 19% 33% 13% 1	3687
	11th to 20th	Night	20% 13% 24% 26% 15% 2	4142
	21st to end	Night	29% 16% 20% 29% 6%	4600
November	1st to 10th	Night	40% 18% 21% 15% 5% 1	2690
	11th to 20th	Night	33% 22% 24% 14% 6%	2974
	21st to end	Night	35% 22% 22% 13% 7% 1	3150
December	1st to 10th	Night	29% 17% 30% 18% 6% 1	5040
	11th to 20th	Night	42% 23% 22% 11% 3	5697
	21st to end	Night	39% 18% 19% 16% 5% 2	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	24% 24% 30% 13% 5% 5%	220
	11th to 20th	Day	21% 23% 35% 17% 3 1	220
	21st to end	Day	19% 38% 31% 7% 4 2	242
February	1st to 10th	Day	23% 29% 32% 11% 4	226
	11th to 20th	Day	15% 27% 35% 17% 6%	344
	21st to end	Day	28% 27% 31% 11% 3	446
March	1st to 10th	Day	23% 33% 26% 12% 5% 1	540
	11th to 20th	Day	26% 25% 26% 15% 7% 1	540
	21st to end	Day	27% 30% 25% 12% 4 1	594
April	1st to 10th	Day	25% 27% 30% 14% 3 1	540
	11th to 20th	Day	22% 30% 28% 14% 5% 1	532
	21st to end	Day	23% 26% 28% 14% 7% 1	540
May	1st to 10th	Day	21% 22% 30% 17% 8% 2	543
	11th to 20th	Day	25% 20% 24% 18% 10% 3	717
	21st to end	Day	25% 16% 25% 21% 12% 2	844
June	1st to 10th	Day	21% 26% 26% 18% 8% 1	780
	11th to 20th	Day	27% 24% 25% 17% 7% 1	780
	21st to end	Day	13% 19% 29% 24% 12% 3	780
July	1st to 10th	Day	11% 16% 31% 25% 15% 2	722
	11th to 20th	Day	11% 18% 30% 28% 11% 2	718
	21st to end	Day	9% 16% 37% 24% 10% 3	601
August	1st to 10th	Day	11% 18% 33% 27% 9% 3	527
	11th to 20th	Day	8% 17% 37% 26% 9% 3	517
	21st to end	Day	13% 22% 34% 19% 9% 3	583
September	1st to 10th	Day	18% 22% 27% 21% 10% 2	530
	11th to 20th	Day	20% 17% 32% 21% 9% 1	530
	21st to end	Day	30% 25% 28% 12% 5% 1	530
October	1st to 10th	Day	22% 27% 26% 17% 8% 1	478
	11th to 20th	Day	28% 23% 25% 15% 8% 1	330
	21st to end	Day	30% 26% 24% 14% 4 1	363
November	1st to 10th	Day	34% 28% 23% 12% 3	330
	11th to 20th	Day	30% 30% 32% 7% 1	311
	21st to end	Day	31% 23% 26% 11% 5% 5%	220
December	1st to 10th	Day	29% 29% 24% 13% 4 1	220
	11th to 20th	Day	29% 29% 30% 11% 1 1	220
	21st to end	Day	22% 26% 31% 13% 7% 1	242
January	1st to 10th	Night	20% 27% 33% 16% 4	1050
	11th to 20th	Night	15% 25% 40% 16% 4	924
	21st to end	Night	13% 31% 35% 16% 4 1	924
February	1st to 10th	Night	15% 22% 35% 20% 6% 2	840
	11th to 20th	Night	13% 21% 38% 22% 5%	824
	21st to end	Night	18% 20% 30% 23% 9%	692
March	1st to 10th	Night	13% 23% 38% 18% 7% 1	840
	11th to 20th	Night	20% 21% 27% 25% 6% 1	840
	21st to end	Night	18% 22% 25% 27% 7% 2	924
April	1st to 10th	Night	16% 22% 29% 23% 10% 1	824
	11th to 20th	Night	14% 24% 29% 24% 8%	623
	21st to end	Night	15% 20% 32% 23% 11%	630
May	1st to 10th	Night	17% 16% 27% 27% 13% 1	565
	11th to 20th	Night	18% 10% 23% 29% 18% 2	414
	21st to end	Night	22% 11% 22% 26% 18% 1	455
June	1st to 10th	Night	18% 16% 23% 27% 13% 2	420
	11th to 20th	Night	20% 17% 27% 24% 11%	420
	21st to end	Night	8% 13% 23% 36% 18% 1	420
July	1st to 10th	Night	8% 7% 24% 36% 25%	390
	11th to 20th	Night	8% 9% 24% 41% 16% 1	388
	21st to end	Night	10% 8% 23% 36% 22% 1	438
August	1st to 10th	Night	11% 6% 18% 38% 25% 1	398
	11th to 20th	Night	8% 8% 23% 35% 24% 2	585
	21st to end	Night	10% 14% 24% 35% 16% 1	660
September	1st to 10th	Night	13% 10% 21% 31% 21% 4	755
	11th to 20th	Night	16% 11% 22% 29% 17% 5%	800
	21st to end	Night	19% 18% 27% 22% 12% 3	800
October	1st to 10th	Night	21% 17% 21% 29% 12% 1	800
	11th to 20th	Night	17% 21% 26% 26% 10% 1	800
	21st to end	Night	18% 26% 30% 20% 5% 1	880
November	1st to 10th	Night	23% 27% 30% 16% 4	845
	11th to 20th	Night	22% 28% 32% 15% 2	1050
	21st to end	Night	17% 25% 36% 16% 5% 1	1050
December	1st to 10th	Night	17% 25% 33% 19% 6% 1	1050
	11th to 20th	Night	17% 26% 37% 17% 3	1050
	21st to end	Night	16% 26% 35% 17% 5%	1155

Page generated at 2026-06-28 00:10:48. Version ac07

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