Canmore
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canmore clear sky chart from 2005-11-05 to 2024-10-14.

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	6% 9% 3 10% 6% 6% 6% 5% 7% 8% 33%	101741
	Night	4 7% 3 9% 6% 5% 6% 5% 8% 10% 37%	96899
Transparency	Day	43% 13% 16% 18% 9% 1	101494
	Night	38% 13% 19% 20% 9% 2	96792
Seeing	Day	18% 22% 32% 19% 7% 1	15213
	Night	11% 21% 37% 22% 8% 1	24175

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 15% 8% 8% 7% 6% 12% 12% 27%	2219
	11th to 20th	Day	4 3 12% 6% 6% 7% 6% 8% 11% 38%	2355
	21st to end	Day	5% 3 8% 5% 6% 6% 7% 11% 13% 37%	2794
February	1st to 10th	Day	1 7% 2 11% 9% 8% 7% 6% 9% 10% 29%	1520
	11th to 20th	Day	1 7% 3 13% 8% 8% 7% 6% 8% 10% 30%	1616
	21st to end	Day	8% 4 15% 9% 8% 8% 7% 8% 9% 25%	1570
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	7% 10% 3 8% 5% 6% 6% 5% 7% 8% 35%	2039
	11th to 20th	Day	4 9% 4 9% 5% 5% 6% 5% 9% 9% 35%	1647
	21st to end	Day	2 9% 4 11% 5% 6% 6% 5% 8% 9% 35%	1782
November	1st to 10th	Day	2 11% 4 10% 6% 6% 5% 5% 8% 11% 33%	1616
	11th to 20th	Day	1 5% 3 8% 5% 6% 6% 7% 10% 12% 39%	1386
	21st to end	Day	1 6% 2 9% 6% 6% 5% 6% 10% 11% 39%	1330
December	1st to 10th	Day	1 5% 3 10% 8% 5% 6% 6% 8% 11% 38%	1330
	11th to 20th	Day	1 5% 2 10% 7% 7% 7% 5% 10% 12% 33%	1682
	21st to end	Day	5% 4 9% 6% 5% 6% 5% 8% 11% 42%	2442
January	1st to 10th	Night	5% 5% 15% 8% 8% 7% 6% 10% 12% 23%	4726
	11th to 20th	Night	4 2 10% 8% 8% 7% 8% 9% 11% 33%	4573
	21st to end	Night	1 5% 4 9% 6% 6% 7% 6% 10% 13% 33%	4862
February	1st to 10th	Night	1 7% 3 11% 8% 8% 9% 7% 8% 10% 28%	2660
	11th to 20th	Night	7% 5% 13% 8% 5% 6% 6% 9% 10% 31%	2448
	21st to end	Night	6% 4 12% 10% 7% 7% 6% 8% 9% 31%	1884
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	6% 10% 3 7% 4 4 5% 4 7% 9% 43%	2137
	11th to 20th	Night	3 9% 3 7% 5% 5% 4 6% 7% 10% 41%	2391
	21st to end	Night	2 8% 5% 10% 6% 5% 5% 6% 9% 10% 34%	2574
November	1st to 10th	Night	2 10% 4 9% 7% 6% 6% 5% 9% 11% 31%	2443
	11th to 20th	Night	1 7% 3 7% 5% 6% 6% 7% 9% 12% 36%	2793
	21st to end	Night	7% 3 10% 7% 6% 6% 5% 9% 12% 34%	2850
December	1st to 10th	Night	1 7% 3 9% 7% 6% 6% 7% 9% 13% 34%	2850
	11th to 20th	Night	4 3 10% 7% 8% 7% 7% 10% 15% 28%	3510
	21st to end	Night	6% 4 9% 6% 6% 7% 6% 9% 13% 34%	5214

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	37% 20% 16% 17% 8% 2	2219
	11th to 20th	Day	38% 12% 15% 15% 14% 5%	2378
	21st to end	Day	32% 19% 24% 19% 6% 1	2794
February	1st to 10th	Day	43% 16% 16% 15% 7% 3	1520
	11th to 20th	Day	44% 16% 16% 16% 7% 1	1624
	21st to end	Day	50% 14% 14% 13% 8% 1	1570
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	41% 14% 14% 21% 8% 1	2039
	11th to 20th	Day	39% 13% 19% 19% 8% 1	1647
	21st to end	Day	40% 14% 20% 17% 9%	1782
November	1st to 10th	Day	42% 16% 21% 15% 6% 1	1616
	11th to 20th	Day	31% 20% 25% 17% 7% 1	1386
	21st to end	Day	34% 18% 24% 17% 6% 2	1330
December	1st to 10th	Day	36% 16% 21% 16% 10% 1	1330
	11th to 20th	Day	35% 17% 25% 16% 6% 1	1684
	21st to end	Day	31% 13% 16% 21% 14% 5%	2442
January	1st to 10th	Night	45% 17% 17% 15% 5% 1	4726
	11th to 20th	Night	38% 12% 16% 14% 12% 8%	4612
	21st to end	Night	36% 18% 23% 15% 7% 1	4862
February	1st to 10th	Night	43% 17% 16% 14% 8% 2	2660
	11th to 20th	Night	42% 14% 19% 15% 8% 1	2450
	21st to end	Night	43% 12% 15% 18% 10% 1	1884
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	35% 12% 18% 23% 11%	2137
	11th to 20th	Night	34% 15% 20% 22% 9% 1	2391
	21st to end	Night	39% 16% 17% 21% 7%	2574
November	1st to 10th	Night	40% 18% 19% 15% 7% 2	2443
	11th to 20th	Night	32% 19% 23% 17% 8% 1	2793
	21st to end	Night	36% 17% 21% 16% 7% 3	2850
December	1st to 10th	Night	35% 18% 19% 17% 9% 2	2850
	11th to 20th	Night	37% 17% 25% 14% 6%	3507
	21st to end	Night	33% 15% 20% 17% 10% 5%	5214

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% 21% 38% 17% 4 3	180
	11th to 20th	Day	9% 31% 38% 16% 6% 1	180
	21st to end	Day	10% 34% 36% 13% 5% 2	198
February	1st to 10th	Day	25% 23% 32% 13% 4 2	180
	11th to 20th	Day	13% 20% 44% 19% 5% 1	254
	21st to end	Day	18% 24% 36% 18% 4 1	382
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	18% 26% 30% 22% 3 1	279
	21st to end	Day	20% 29% 36% 11% 4 1	297
November	1st to 10th	Day	17% 32% 34% 10% 5% 1	270
	11th to 20th	Day	14% 30% 45% 8% 2	206
	21st to end	Day	16% 28% 29% 16% 8% 4	180
December	1st to 10th	Day	13% 31% 31% 17% 6% 2	180
	11th to 20th	Day	9% 35% 38% 14% 3 1	180
	21st to end	Day	11% 28% 38% 19% 4 1	198
January	1st to 10th	Night	10% 30% 46% 11% 2	950
	11th to 20th	Night	8% 29% 45% 15% 3 1	874
	21st to end	Night	8% 32% 41% 15% 4	836
February	1st to 10th	Night	12% 24% 38% 19% 7% 1	760
	11th to 20th	Night	8% 22% 44% 20% 5%	744
	21st to end	Night	9% 17% 43% 22% 8%	628
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	12% 21% 38% 24% 5% 1	734
	21st to end	Night	12% 26% 39% 19% 4	792
November	1st to 10th	Night	12% 29% 42% 13% 3	778
	11th to 20th	Night	11% 33% 43% 11% 2 1	950
	21st to end	Night	10% 30% 40% 16% 3 1	950
December	1st to 10th	Night	8% 31% 39% 17% 5%	950
	11th to 20th	Night	8% 30% 44% 14% 4	950
	21st to end	Night	7% 27% 46% 14% 5%	1045

Page generated at 2024-10-11 08:49:57. Version ac07

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