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 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	5% 9% 4 9% 6% 6% 6% 5% 7% 8% 36%	112135
	Night	3 8% 4 9% 7% 7% 6% 5% 8% 9% 34%	115193
Transparency	Day	35% 13% 19% 21% 10% 2	111889
	Night	34% 15% 20% 20% 9% 2	115085
Seeing	Day	20% 23% 29% 18% 8% 2	15537
	Night	15% 20% 30% 24% 10% 1	24872

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 7% 7% 15% 10% 7% 7% 6% 9% 8% 24%	3179
	11th to 20th	Day	5% 4 13% 11% 9% 6% 6% 9% 9% 27%	3475
	21st to end	Day	1 7% 3 7% 6% 7% 8% 7% 10% 7% 37%	4004
February	1st to 10th	Day	2 9% 5% 13% 9% 8% 9% 6% 9% 11% 19%	1607
	11th to 20th	Day	2 13% 7% 15% 8% 6% 7% 6% 8% 8% 22%	1768
	21st to end	Day	2 11% 6% 16% 9% 8% 7% 6% 9% 7% 20%	1611
March	1st to 10th	Day	1 7% 5% 16% 8% 8% 6% 5% 10% 7% 28%	3138
	11th to 20th	Day	2 12% 6% 9% 6% 6% 6% 5% 6% 6% 37%	3427
	21st to end	Day	4 20% 8% 16% 8% 6% 5% 4 7% 5% 19%	3907
April	1st to 10th	Day	4 16% 6% 13% 9% 6% 6% 5% 7% 7% 21%	2294
	11th to 20th	Day	6% 17% 6% 13% 7% 5% 6% 5% 7% 6% 23%	2440
	21st to end	Day	9% 16% 5% 9% 6% 6% 5% 5% 6% 7% 27%	2470
May	1st to 10th	Day	13% 21% 4 9% 5% 5% 4 4 5% 5% 24%	4203
	11th to 20th	Day	8% 10% 3 7% 6% 7% 7% 6% 9% 9% 27%	4616
	21st to end	Day	14% 12% 3 8% 7% 7% 7% 6% 8% 9% 20%	5161
June	1st to 10th	Day	15% 10% 4 9% 8% 5% 5% 4 7% 6% 27%	2850
	11th to 20th	Day	15% 10% 3 10% 7% 6% 6% 5% 7% 7% 22%	2850
	21st to end	Day	8% 7% 3 7% 6% 5% 5% 5% 7% 8% 40%	2850
July	1st to 10th	Day	4 4 2 5% 4 5% 5% 4 6% 8% 54%	4740
	11th to 20th	Day	3 3 1 3 3 3 4 3 7% 7% 62%	4740
	21st to end	Day	2 2 1 4 3 4 4 4 6% 8% 63%	4828
August	1st to 10th	Day	8% 6% 2 5% 5% 5% 6% 4 7% 8% 45%	4401
	11th to 20th	Day	5% 4 1 5% 3 4 5% 4 6% 7% 55%	4037
	21st to end	Day	6% 4 1 4 4 4 4 4 6% 7% 55%	4521
September	1st to 10th	Day	9% 8% 2 5% 3 5% 5% 3 6% 7% 48%	2311
	11th to 20th	Day	10% 6% 3 6% 4 4 5% 5% 7% 9% 43%	2090
	21st to end	Day	7% 8% 3 6% 4 5% 6% 3 6% 7% 44%	2090
October	1st to 10th	Day	5% 8% 3 7% 4 4 4 3 5% 7% 50%	3402
	11th to 20th	Day	2 7% 2 8% 7% 7% 6% 5% 8% 10% 39%	2910
	21st to end	Day	5% 9% 4 9% 8% 9% 6% 4 6% 8% 33%	3101
November	1st to 10th	Day	6% 12% 5% 13% 8% 7% 7% 6% 7% 8% 23%	1719
	11th to 20th	Day	2 7% 5% 8% 8% 7% 7% 6% 10% 10% 29%	1565
	21st to end	Day	2 10% 3 10% 8% 8% 8% 5% 11% 10% 26%	1400
December	1st to 10th	Day	1 7% 4 8% 5% 7% 6% 6% 11% 11% 34%	2290
	11th to 20th	Day	1 8% 4 11% 10% 11% 8% 6% 11% 10% 20%	2642
	21st to end	Day	1 8% 5% 11% 7% 9% 9% 6% 9% 10% 25%	3498
January	1st to 10th	Night	1 7% 6% 15% 9% 8% 8% 7% 11% 9% 19%	6766
	11th to 20th	Night	4 4 12% 9% 8% 8% 6% 8% 11% 30%	6466
	21st to end	Night	1 10% 4 9% 7% 7% 7% 6% 9% 8% 34%	6952
February	1st to 10th	Night	2 10% 6% 12% 9% 7% 8% 7% 9% 9% 22%	2792
	11th to 20th	Night	1 11% 6% 13% 8% 6% 7% 5% 10% 9% 25%	2517
	21st to end	Night	1 10% 4 13% 9% 7% 8% 6% 9% 8% 25%	1937
March	1st to 10th	Night	1 5% 5% 16% 10% 8% 7% 5% 9% 9% 25%	3736
	11th to 20th	Night	2 9% 4 7% 6% 6% 6% 5% 8% 6% 41%	3552
	21st to end	Night	5% 19% 9% 14% 7% 6% 6% 5% 7% 6% 17%	3743
April	1st to 10th	Night	5% 11% 4 9% 5% 5% 7% 5% 9% 9% 30%	1886
	11th to 20th	Night	5% 11% 4 10% 7% 4 5% 5% 8% 9% 32%	1691
	21st to end	Night	6% 14% 4 8% 6% 6% 5% 4 8% 8% 34%	1710
May	1st to 10th	Night	11% 17% 3 9% 6% 5% 6% 4 5% 6% 30%	2749
	11th to 20th	Night	6% 7% 3 6% 4 4 6% 7% 9% 10% 37%	2277
	21st to end	Night	13% 13% 4 8% 4 5% 6% 4 9% 7% 27%	2414
June	1st to 10th	Night	10% 9% 3 8% 5% 6% 6% 6% 8% 7% 32%	1330
	11th to 20th	Night	13% 8% 2 8% 4 6% 7% 5% 7% 8% 30%	1330
	21st to end	Night	4 5% 2 6% 4 3 6% 5% 6% 8% 50%	1330
July	1st to 10th	Night	4 2 1 4 5% 5% 4 3 6% 7% 58%	2220
	11th to 20th	Night	2 3 1 5% 3 2 3 3 5% 6% 65%	2220
	21st to end	Night	2 3 1 3 3 2 3 3 4 6% 70%	2720
August	1st to 10th	Night	9% 10% 2 4 3 3 3 3 4 6% 54%	2529
	11th to 20th	Night	4 3 1 5% 4 4 5% 5% 8% 11% 52%	2802
	21st to end	Night	4 4 1 3 3 4 5% 4 6% 10% 56%	3146
September	1st to 10th	Night	7% 6% 1 4 3 3 4 4 5% 7% 56%	1864
	11th to 20th	Night	7% 7% 2 5% 4 4 5% 4 6% 9% 46%	2090
	21st to end	Night	6% 9% 2 6% 4 4 3 4 7% 9% 45%	2090
October	1st to 10th	Night	5% 6% 1 5% 4 6% 5% 3 6% 9% 50%	3574
	11th to 20th	Night	2 4 2 6% 6% 7% 5% 5% 7% 10% 45%	4014
	21st to end	Night	2 7% 3 9% 7% 10% 6% 5% 7% 9% 34%	4457
November	1st to 10th	Night	5% 12% 4 10% 6% 6% 7% 5% 10% 10% 25%	2559
	11th to 20th	Night	2 8% 4 11% 8% 8% 7% 7% 10% 10% 26%	2832
	21st to end	Night	2 10% 3 10% 7% 9% 7% 6% 11% 11% 25%	3000
December	1st to 10th	Night	1 6% 3 8% 6% 6% 7% 5% 11% 12% 34%	4890
	11th to 20th	Night	1 10% 6% 13% 9% 11% 9% 6% 10% 9% 16%	5550
	21st to end	Night	1 9% 5% 13% 9% 12% 8% 6% 9% 8% 21%	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	41% 17% 20% 16% 5% 1	3179
	11th to 20th	Day	44% 13% 18% 14% 8% 3	3499
	21st to end	Day	24% 21% 23% 21% 11%	4004
February	1st to 10th	Day	43% 20% 18% 11% 6% 2	1607
	11th to 20th	Day	46% 14% 20% 14% 5% 1	1777
	21st to end	Day	45% 15% 20% 13% 5% 2	1611
March	1st to 10th	Day	33% 18% 21% 17% 10% 1	3138
	11th to 20th	Day	31% 16% 29% 20% 4	3428
	21st to end	Day	53% 14% 19% 9% 5%	3907
April	1st to 10th	Day	48% 14% 19% 16% 3	2294
	11th to 20th	Day	50% 12% 18% 16% 4	2440
	21st to end	Day	47% 11% 18% 18% 5% 1	2470
May	1st to 10th	Day	56% 9% 13% 18% 4	4203
	11th to 20th	Day	40% 15% 18% 23% 5%	4620
	21st to end	Day	43% 18% 21% 13% 5%	5162
June	1st to 10th	Day	49% 11% 16% 18% 6%	2850
	11th to 20th	Day	50% 11% 16% 15% 7% 1	2850
	21st to end	Day	34% 10% 18% 23% 13% 1	2850
July	1st to 10th	Day	23% 8% 12% 26% 23% 7%	4666
	11th to 20th	Day	19% 7% 11% 27% 28% 8%	4659
	21st to end	Day	16% 5% 10% 27% 26% 15%	4675
August	1st to 10th	Day	34% 7% 14% 22% 18% 5%	4384
	11th to 20th	Day	25% 7% 19% 34% 13% 2	4076
	21st to end	Day	23% 7% 16% 38% 14% 2	4520
September	1st to 10th	Day	31% 7% 16% 24% 16% 6%	2311
	11th to 20th	Day	33% 9% 17% 26% 14% 2	2090
	21st to end	Day	31% 10% 23% 24% 11% 1	2090
October	1st to 10th	Day	30% 9% 22% 32% 7%	3402
	11th to 20th	Day	27% 13% 24% 21% 13% 1	2910
	21st to end	Day	33% 14% 21% 23% 9% 1	3101
November	1st to 10th	Day	43% 16% 21% 15% 5% 1	1719
	11th to 20th	Day	30% 22% 26% 15% 6%	1565
	21st to end	Day	38% 20% 21% 14% 6% 1	1400
December	1st to 10th	Day	29% 19% 27% 20% 5% 1	2290
	11th to 20th	Day	36% 22% 27% 12% 3	2644
	21st to end	Day	34% 17% 19% 21% 9% 1	3498
January	1st to 10th	Night	43% 18% 20% 15% 4 1	6766
	11th to 20th	Night	37% 13% 19% 16% 10% 5%	6504
	21st to end	Night	29% 21% 22% 19% 10%	6952
February	1st to 10th	Night	44% 16% 18% 13% 7% 2	2792
	11th to 20th	Night	42% 16% 21% 14% 6% 1	2518
	21st to end	Night	42% 15% 19% 17% 5% 1	1937
March	1st to 10th	Night	37% 19% 19% 18% 7%	3736
	11th to 20th	Night	28% 18% 29% 21% 4 1	3552
	21st to end	Night	53% 14% 19% 11% 2	3743
April	1st to 10th	Night	41% 13% 21% 16% 7%	1886
	11th to 20th	Night	41% 11% 20% 24% 4	1691
	21st to end	Night	42% 12% 18% 22% 6% 1	1710
May	1st to 10th	Night	50% 10% 14% 20% 5%	2749
	11th to 20th	Night	30% 13% 22% 27% 8%	2277
	21st to end	Night	42% 17% 20% 16% 6%	2414
June	1st to 10th	Night	41% 11% 23% 19% 5% 1	1330
	11th to 20th	Night	44% 11% 18% 18% 8% 1	1330
	21st to end	Night	25% 10% 21% 29% 13% 2	1330
July	1st to 10th	Night	21% 7% 19% 27% 18% 8%	2185
	11th to 20th	Night	19% 6% 13% 28% 25% 10%	2178
	21st to end	Night	15% 5% 11% 28% 28% 14%	2634
August	1st to 10th	Night	32% 6% 13% 25% 20% 4	2521
	11th to 20th	Night	24% 7% 24% 29% 15% 2	2829
	21st to end	Night	20% 8% 16% 37% 18% 1	3146
September	1st to 10th	Night	25% 7% 15% 31% 16% 6%	1864
	11th to 20th	Night	30% 9% 18% 27% 13% 2	2090
	21st to end	Night	29% 10% 23% 23% 12% 2	2090
October	1st to 10th	Night	25% 9% 19% 33% 14% 1	3574
	11th to 20th	Night	20% 13% 25% 27% 14% 2	4014
	21st to end	Night	29% 16% 20% 28% 6%	4457
November	1st to 10th	Night	40% 19% 21% 14% 6% 1	2559
	11th to 20th	Night	31% 23% 25% 14% 6%	2832
	21st to end	Night	35% 22% 22% 13% 7% 1	3000
December	1st to 10th	Night	29% 17% 30% 18% 6% 1	4890
	11th to 20th	Night	41% 23% 22% 11% 3	5547
	21st to end	Night	40% 18% 19% 16% 5% 2	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	21% 23% 32% 15% 6% 5%	200
	11th to 20th	Day	19% 24% 35% 19% 4 2	200
	21st to end	Day	16% 39% 30% 8% 5% 2	220
February	1st to 10th	Day	21% 28% 34% 12% 5%	205
	11th to 20th	Day	14% 26% 37% 17% 6%	313
	21st to end	Day	24% 29% 33% 12% 3	399
March	1st to 10th	Day	20% 34% 27% 13% 5% 1	460
	11th to 20th	Day	20% 26% 27% 17% 8% 1	460
	21st to end	Day	23% 33% 25% 13% 4 2	506
April	1st to 10th	Day	24% 29% 30% 14% 3	460
	11th to 20th	Day	21% 31% 26% 16% 5% 1	452
	21st to end	Day	25% 28% 26% 13% 7% 2	460
May	1st to 10th	Day	22% 21% 29% 18% 9% 2	463
	11th to 20th	Day	25% 17% 25% 19% 11% 4	623
	21st to end	Day	26% 15% 23% 22% 12% 2	734
June	1st to 10th	Day	20% 25% 27% 19% 8% 2	680
	11th to 20th	Day	28% 23% 23% 17% 8% 1	680
	21st to end	Day	13% 19% 27% 26% 13% 3	680
July	1st to 10th	Day	10% 15% 30% 26% 16% 3	671
	11th to 20th	Day	11% 17% 30% 29% 12% 2	668
	21st to end	Day	8% 17% 37% 25% 10% 3	556
August	1st to 10th	Day	11% 17% 33% 26% 9% 3	487
	11th to 20th	Day	7% 15% 38% 27% 10% 3	477
	21st to end	Day	13% 23% 34% 19% 9% 2	539
September	1st to 10th	Day	19% 24% 27% 20% 9% 2	490
	11th to 20th	Day	21% 18% 33% 18% 9% 1	490
	21st to end	Day	30% 24% 27% 12% 5% 1	490
October	1st to 10th	Day	22% 27% 26% 17% 8% 1	441
	11th to 20th	Day	25% 23% 25% 16% 9% 1	300
	21st to end	Day	29% 25% 25% 15% 5% 1	330
November	1st to 10th	Day	31% 29% 24% 13% 3	300
	11th to 20th	Day	29% 30% 32% 7% 1	283
	21st to end	Day	30% 22% 27% 12% 5% 5%	200
December	1st to 10th	Day	26% 30% 25% 14% 5% 1	200
	11th to 20th	Day	24% 31% 32% 12% 1 1	200
	21st to end	Day	20% 24% 32% 15% 8% 1	220
January	1st to 10th	Night	18% 27% 34% 17% 4	1000
	11th to 20th	Night	13% 26% 40% 17% 4	880
	21st to end	Night	11% 31% 36% 16% 4 1	880
February	1st to 10th	Night	13% 22% 36% 21% 7% 2	800
	11th to 20th	Night	13% 21% 38% 23% 5%	784
	21st to end	Night	15% 20% 32% 23% 9%	646
March	1st to 10th	Night	11% 23% 38% 19% 7% 1	760
	11th to 20th	Night	17% 21% 28% 27% 7% 1	760
	21st to end	Night	16% 19% 26% 28% 8% 2	836
April	1st to 10th	Night	15% 22% 29% 23% 10% 1	746
	11th to 20th	Night	14% 24% 27% 25% 9% 1	563
	21st to end	Night	15% 21% 32% 22% 10% 1	570
May	1st to 10th	Night	18% 15% 26% 26% 14% 1	511
	11th to 20th	Night	17% 10% 23% 29% 20% 2	374
	21st to end	Night	23% 10% 20% 27% 18% 1	411
June	1st to 10th	Night	17% 17% 24% 28% 13% 2	380
	11th to 20th	Night	21% 16% 28% 22% 12% 1	380
	21st to end	Night	7% 13% 24% 37% 19% 1	380
July	1st to 10th	Night	8% 6% 24% 36% 26%	370
	11th to 20th	Night	7% 9% 25% 40% 17% 1	368
	21st to end	Night	8% 8% 22% 37% 23% 1	416
August	1st to 10th	Night	11% 6% 17% 39% 26% 1	378
	11th to 20th	Night	8% 7% 22% 35% 25% 3	555
	21st to end	Night	10% 14% 25% 33% 16% 1	627
September	1st to 10th	Night	14% 10% 21% 31% 20% 4	717
	11th to 20th	Night	16% 12% 23% 28% 17% 5%	760
	21st to end	Night	19% 18% 26% 22% 12% 3	760
October	1st to 10th	Night	21% 16% 20% 30% 12% 1	760
	11th to 20th	Night	15% 21% 26% 27% 10% 1	760
	21st to end	Night	16% 26% 31% 21% 6% 1	836
November	1st to 10th	Night	21% 27% 31% 17% 4	804
	11th to 20th	Night	21% 29% 33% 15% 2 1	1000
	21st to end	Night	16% 25% 36% 17% 5% 1	1000
December	1st to 10th	Night	15% 26% 33% 20% 6% 1	1000
	11th to 20th	Night	14% 26% 39% 18% 3	1000
	21st to end	Night	15% 25% 36% 17% 6%	1100

Page generated at 2025-02-22 04:51:35. Version ac07

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