Okotoks
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Okotoks 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	8% 8% 3 8% 5% 5% 5% 4 6% 8% 40%	142076
	Night	6% 9% 3 9% 5% 5% 5% 4 6% 8% 39%	139013
Transparency	Day	39% 6% 15% 26% 12% 2	141779
	Night	40% 6% 15% 24% 13% 2	138893
Seeing	Day	13% 11% 29% 29% 15% 4	17486
	Night	11% 8% 32% 35% 13% 2	26578

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 9% 6% 12% 7% 7% 6% 5% 7% 8% 31%	4125
	11th to 20th	Day	2 7% 3 9% 5% 5% 4 4 7% 7% 46%	4273
	21st to end	Day	2 6% 3 10% 5% 4 4 4 6% 11% 45%	5186
February	1st to 10th	Day	3 10% 5% 13% 7% 5% 6% 5% 7% 8% 31%	1680
	11th to 20th	Day	3 11% 5% 11% 7% 7% 7% 5% 7% 8% 30%	1845
	21st to end	Day	2 11% 5% 11% 6% 7% 5% 5% 5% 9% 34%	1691
March	1st to 10th	Day	3 9% 4 11% 6% 6% 4 3 5% 11% 39%	4618
	11th to 20th	Day	5% 10% 4 9% 5% 4 5% 4 5% 8% 42%	5058
	21st to end	Day	7% 20% 7% 13% 5% 4 5% 4 6% 7% 23%	5686
April	1st to 10th	Day	8% 15% 4 9% 6% 5% 6% 4 6% 7% 30%	2572
	11th to 20th	Day	10% 13% 5% 9% 6% 4 5% 4 6% 8% 30%	2700
	21st to end	Day	12% 12% 3 8% 5% 4 5% 4 7% 8% 32%	2730
May	1st to 10th	Day	11% 10% 3 6% 4 4 5% 5% 6% 8% 38%	7945
	11th to 20th	Day	10% 10% 4 9% 6% 6% 6% 5% 8% 8% 28%	8755
	21st to end	Day	12% 6% 2 7% 6% 5% 6% 5% 6% 8% 36%	9649
June	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 5% 7% 7% 32%	3150
	11th to 20th	Day	18% 8% 3 7% 6% 5% 5% 5% 6% 9% 28%	3150
	21st to end	Day	9% 5% 2 5% 5% 5% 5% 5% 8% 10% 41%	3150
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 5% 7% 9% 50%	6781
	11th to 20th	Day	10% 4 2 5% 4 4 4 4 7% 9% 48%	6780
	21st to end	Day	8% 5% 2 5% 3 4 4 4 5% 8% 52%	7158
August	1st to 10th	Day	9% 6% 2 5% 4 4 5% 4 8% 9% 43%	4541
	11th to 20th	Day	7% 5% 2 4 4 4 5% 5% 7% 10% 46%	4188
	21st to end	Day	9% 4 1 4 3 3 4 3 6% 8% 55%	4664
September	1st to 10th	Day	10% 5% 1 6% 4 4 4 3 4 7% 51%	2470
	11th to 20th	Day	12% 7% 2 5% 3 4 4 3 5% 7% 46%	2200
	21st to end	Day	7% 8% 2 6% 4 4 4 3 6% 8% 47%	2200
October	1st to 10th	Day	6% 7% 2 7% 5% 4 5% 4 6% 9% 45%	3453
	11th to 20th	Day	5% 7% 2 6% 5% 4 4 4 8% 11% 44%	3011
	21st to end	Day	6% 8% 3 6% 5% 4 5% 4 6% 7% 46%	3200
November	1st to 10th	Day	8% 14% 4 8% 6% 4 4 5% 5% 8% 34%	1733
	11th to 20th	Day	5% 12% 4 7% 5% 4 4 4 6% 8% 40%	1617
	21st to end	Day	3 12% 5% 9% 5% 4 6% 5% 7% 10% 34%	1470
December	1st to 10th	Day	2 9% 5% 11% 7% 5% 5% 5% 7% 7% 36%	2360
	11th to 20th	Day	2 9% 4 11% 6% 6% 6% 5% 6% 9% 35%	2712
	21st to end	Day	4 10% 4 9% 5% 5% 5% 4 5% 8% 42%	3575
January	1st to 10th	Night	3 12% 5% 13% 8% 6% 6% 4 7% 8% 29%	8768
	11th to 20th	Night	2 6% 4 11% 6% 6% 6% 5% 6% 9% 40%	8682
	21st to end	Night	2 7% 3 11% 6% 6% 5% 4 6% 8% 41%	8994
February	1st to 10th	Night	3 10% 5% 11% 7% 6% 6% 5% 7% 8% 32%	2940
	11th to 20th	Night	4 13% 6% 10% 6% 6% 6% 4 6% 9% 31%	2662
	21st to end	Night	2 10% 5% 11% 9% 7% 5% 4 5% 7% 35%	2113
March	1st to 10th	Night	2 8% 4 12% 7% 6% 6% 4 6% 10% 35%	5496
	11th to 20th	Night	3 9% 4 10% 6% 6% 5% 4 6% 8% 40%	5160
	21st to end	Night	9% 19% 6% 11% 6% 5% 4 4 6% 7% 23%	5527
April	1st to 10th	Night	8% 15% 4 8% 5% 5% 5% 4 6% 7% 32%	2047
	11th to 20th	Night	10% 12% 5% 10% 6% 4 4 4 6% 6% 33%	1871
	21st to end	Night	10% 11% 4 8% 6% 5% 6% 4 6% 8% 34%	1890
May	1st to 10th	Night	12% 11% 3 7% 4 4 4 3 5% 7% 41%	4975
	11th to 20th	Night	11% 9% 4 9% 5% 5% 5% 5% 6% 11% 31%	4105
	21st to end	Night	10% 6% 3 7% 5% 6% 6% 5% 7% 9% 37%	4522
June	1st to 10th	Night	14% 7% 3 8% 5% 5% 4 4 6% 8% 36%	1470
	11th to 20th	Night	16% 9% 3 7% 5% 4 5% 5% 6% 8% 32%	1470
	21st to end	Night	8% 5% 2 4 4 5% 5% 4 9% 9% 47%	1470
July	1st to 10th	Night	7% 5% 2 7% 5% 5% 3 3 6% 7% 49%	3180
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 4 6% 8% 50%	3180
	21st to end	Night	11% 5% 2 5% 3 3 3 3 5% 7% 52%	3684
August	1st to 10th	Night	10% 6% 2 6% 4 4 4 4 7% 8% 44%	2609
	11th to 20th	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 10% 44%	2870
	21st to end	Night	7% 4 1 4 3 3 4 3 6% 9% 55%	3245
September	1st to 10th	Night	9% 6% 2 5% 3 3 4 3 6% 7% 52%	1927
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 5% 6% 51%	2200
	21st to end	Night	9% 7% 2 4 3 4 4 4 6% 8% 49%	2200
October	1st to 10th	Night	7% 6% 2 5% 3 4 4 4 5% 8% 52%	3742
	11th to 20th	Night	6% 6% 2 5% 4 4 4 3 6% 8% 50%	4135
	21st to end	Night	5% 8% 3 7% 5% 5% 5% 4 6% 7% 47%	4600
November	1st to 10th	Night	7% 12% 4 9% 5% 6% 4 4 5% 7% 36%	2765
	11th to 20th	Night	4 10% 4 8% 6% 4 5% 4 7% 8% 40%	3001
	21st to end	Night	4 10% 4 9% 5% 5% 5% 4 7% 9% 38%	3150
December	1st to 10th	Night	2 9% 4 8% 6% 6% 7% 6% 9% 9% 34%	5040
	11th to 20th	Night	2 10% 4 12% 8% 6% 6% 5% 7% 8% 31%	5700
	21st to end	Night	4 11% 4 9% 5% 5% 5% 4 6% 8% 40%	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	46% 6% 12% 20% 12% 3	4125
	11th to 20th	Day	36% 4 15% 25% 17% 4	4294
	21st to end	Day	32% 5% 15% 32% 15% 1	5187
February	1st to 10th	Day	48% 7% 13% 19% 11% 3	1680
	11th to 20th	Day	47% 6% 13% 21% 10% 2	1854
	21st to end	Day	47% 4 14% 20% 14% 1	1691
March	1st to 10th	Day	39% 7% 13% 23% 17% 1	4618
	11th to 20th	Day	39% 5% 13% 26% 16% 1	5059
	21st to end	Day	57% 7% 15% 15% 6%	5686
April	1st to 10th	Day	50% 6% 14% 21% 8% 1	2572
	11th to 20th	Day	49% 5% 13% 22% 10% 1	2700
	21st to end	Day	47% 5% 14% 23% 10% 1	2730
May	1st to 10th	Day	42% 4 10% 27% 15% 2	7945
	11th to 20th	Day	47% 7% 12% 23% 8% 2	8759
	21st to end	Day	41% 6% 16% 25% 10% 1	9650
June	1st to 10th	Day	47% 6% 15% 19% 11% 2	3150
	11th to 20th	Day	50% 5% 16% 19% 8% 2	3150
	21st to end	Day	34% 7% 20% 26% 11% 2	3150
July	1st to 10th	Day	28% 6% 18% 28% 17% 4	6707
	11th to 20th	Day	31% 5% 21% 29% 12% 1	6699
	21st to end	Day	29% 4 15% 26% 17% 8%	6956
August	1st to 10th	Day	33% 6% 17% 35% 8% 1	4524
	11th to 20th	Day	30% 7% 25% 29% 8% 1	4227
	21st to end	Day	26% 5% 17% 36% 15% 1	4663
September	1st to 10th	Day	32% 4 15% 26% 17% 5%	2470
	11th to 20th	Day	36% 5% 15% 28% 14% 2	2200
	21st to end	Day	35% 4 15% 30% 13% 3	2200
October	1st to 10th	Day	33% 5% 17% 35% 9% 1	3453
	11th to 20th	Day	32% 4 20% 27% 14% 3	3011
	21st to end	Day	35% 6% 11% 33% 13% 3	3200
November	1st to 10th	Day	47% 7% 12% 21% 11% 2	1733
	11th to 20th	Day	41% 5% 17% 24% 11% 1	1617
	21st to end	Day	41% 7% 18% 22% 10% 3	1470
December	1st to 10th	Day	44% 6% 14% 26% 8% 2	2360
	11th to 20th	Day	43% 7% 21% 20% 8% 1	2714
	21st to end	Day	40% 4 10% 24% 18% 4	3575
January	1st to 10th	Night	50% 5% 12% 21% 10% 2	8769
	11th to 20th	Night	39% 5% 17% 21% 12% 5%	8723
	21st to end	Night	39% 4 17% 25% 14% 1	8994
February	1st to 10th	Night	47% 6% 12% 20% 13% 3	2940
	11th to 20th	Night	48% 6% 13% 19% 12% 2	2663
	21st to end	Night	47% 5% 11% 23% 12% 3	2113
March	1st to 10th	Night	42% 7% 16% 21% 12% 2	5496
	11th to 20th	Night	39% 7% 15% 23% 15% 1	5160
	21st to end	Night	57% 7% 12% 14% 9% 1	5527
April	1st to 10th	Night	48% 7% 12% 22% 11% 1	2047
	11th to 20th	Night	49% 5% 12% 23% 9% 1	1871
	21st to end	Night	47% 6% 14% 23% 9% 2	1890
May	1st to 10th	Night	43% 4 11% 26% 15% 1	4972
	11th to 20th	Night	45% 6% 14% 26% 8% 1	4105
	21st to end	Night	41% 6% 17% 27% 8% 1	4526
June	1st to 10th	Night	44% 5% 15% 24% 12% 1	1470
	11th to 20th	Night	46% 6% 15% 21% 10% 3	1470
	21st to end	Night	31% 5% 22% 28% 12% 1	1470
July	1st to 10th	Night	32% 6% 16% 23% 20% 2	3145
	11th to 20th	Night	29% 7% 21% 32% 8% 3	3138
	21st to end	Night	31% 5% 16% 26% 16% 7%	3581
August	1st to 10th	Night	35% 6% 16% 28% 13% 2	2601
	11th to 20th	Night	32% 7% 22% 27% 10% 1	2897
	21st to end	Night	24% 5% 18% 35% 15% 2	3245
September	1st to 10th	Night	29% 5% 16% 29% 16% 5%	1927
	11th to 20th	Night	33% 5% 15% 30% 14% 4	2200
	21st to end	Night	32% 4 17% 28% 15% 4	2200
October	1st to 10th	Night	29% 5% 15% 29% 19% 2	3742
	11th to 20th	Night	30% 5% 19% 25% 19% 3	4135
	21st to end	Night	35% 5% 12% 33% 15% 1	4600
November	1st to 10th	Night	46% 6% 13% 21% 12% 2	2765
	11th to 20th	Night	39% 6% 16% 22% 15% 1	3001
	21st to end	Night	40% 6% 17% 23% 11% 4	3150
December	1st to 10th	Night	41% 9% 20% 20% 9% 2	5040
	11th to 20th	Night	47% 7% 21% 17% 8%	5697
	21st to end	Night	40% 4 11% 25% 16% 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	2 9% 30% 36% 14% 9%	220
	11th to 20th	Day	9% 8% 38% 30% 12% 3	220
	21st to end	Day	7% 10% 24% 44% 12% 3	242
February	1st to 10th	Day	7% 12% 37% 29% 12% 3	220
	11th to 20th	Day	6% 7% 36% 36% 13% 2	330
	21st to end	Day	7% 14% 34% 31% 14% 1	407
March	1st to 10th	Day	8% 16% 39% 24% 11% 3	540
	11th to 20th	Day	9% 14% 33% 30% 11% 2	540
	21st to end	Day	13% 19% 34% 23% 9% 3	594
April	1st to 10th	Day	14% 17% 35% 24% 8% 2	540
	11th to 20th	Day	17% 15% 29% 26% 10% 2	532
	21st to end	Day	16% 19% 30% 21% 11% 3	540
May	1st to 10th	Day	18% 10% 29% 25% 14% 4	572
	11th to 20th	Day	19% 10% 24% 27% 17% 3	775
	21st to end	Day	18% 8% 23% 27% 20% 4	844
June	1st to 10th	Day	17% 11% 29% 30% 12% 3	780
	11th to 20th	Day	19% 11% 29% 28% 11% 2	780
	21st to end	Day	12% 7% 26% 31% 19% 4	780
July	1st to 10th	Day	10% 6% 25% 33% 22% 4	722
	11th to 20th	Day	11% 6% 26% 34% 19% 3	718
	21st to end	Day	7% 7% 29% 31% 21% 5%	703
August	1st to 10th	Day	9% 7% 28% 33% 18% 5%	527
	11th to 20th	Day	9% 6% 28% 33% 18% 6%	517
	21st to end	Day	11% 7% 26% 30% 18% 8%	583
September	1st to 10th	Day	12% 9% 28% 28% 16% 8%	530
	11th to 20th	Day	17% 8% 25% 28% 17% 6%	530
	21st to end	Day	13% 17% 28% 29% 10% 3	530
October	1st to 10th	Day	13% 10% 26% 31% 16% 4	448
	11th to 20th	Day	14% 11% 32% 25% 14% 5%	330
	21st to end	Day	13% 13% 39% 23% 10% 3	363
November	1st to 10th	Day	19% 11% 29% 30% 8% 3	330
	11th to 20th	Day	12% 15% 33% 29% 8% 3	297
	21st to end	Day	8% 13% 28% 32% 12% 8%	220
December	1st to 10th	Day	7% 9% 34% 30% 16% 3	220
	11th to 20th	Day	5% 12% 42% 27% 10% 4	220
	21st to end	Day	8% 6% 28% 33% 22% 3	242
January	1st to 10th	Night	9% 10% 36% 33% 10% 1	1050
	11th to 20th	Night	8% 8% 38% 34% 11% 1	1018
	21st to end	Night	9% 10% 35% 36% 9% 1	924
February	1st to 10th	Night	8% 10% 33% 33% 12% 3	840
	11th to 20th	Night	10% 7% 33% 37% 12% 1	824
	21st to end	Night	7% 6% 32% 35% 17% 2	692
March	1st to 10th	Night	8% 7% 35% 34% 13% 3	840
	11th to 20th	Night	8% 10% 36% 34% 10% 2	840
	21st to end	Night	11% 9% 32% 35% 10% 3	924
April	1st to 10th	Night	13% 11% 31% 31% 12% 1	787
	11th to 20th	Night	15% 10% 35% 31% 9%	623
	21st to end	Night	17% 9% 31% 33% 11%	630
May	1st to 10th	Night	16% 11% 24% 32% 17%	545
	11th to 20th	Night	14% 9% 23% 33% 20% 1	414
	21st to end	Night	20% 6% 22% 35% 16% 1	455
June	1st to 10th	Night	17% 8% 26% 35% 12% 1	420
	11th to 20th	Night	19% 6% 30% 31% 12% 1	420
	21st to end	Night	11% 5% 20% 40% 24% 1	420
July	1st to 10th	Night	11% 3 17% 43% 24% 1	390
	11th to 20th	Night	10% 3 20% 43% 22% 2	388
	21st to end	Night	7% 3 21% 43% 23% 2	438
August	1st to 10th	Night	12% 3 14% 39% 31% 2	398
	11th to 20th	Night	9% 4 18% 46% 22% 2	575
	21st to end	Night	9% 5% 23% 41% 22% 1	660
September	1st to 10th	Night	12% 3 26% 35% 20% 3	708
	11th to 20th	Night	18% 3 19% 36% 21% 3	800
	21st to end	Night	11% 6% 34% 36% 10% 3	800
October	1st to 10th	Night	15% 4 28% 36% 14% 3	800
	11th to 20th	Night	12% 7% 32% 33% 13% 3	800
	21st to end	Night	11% 8% 34% 36% 10% 1	880
November	1st to 10th	Night	13% 10% 39% 29% 8% 1	920
	11th to 20th	Night	10% 13% 39% 30% 7% 2	1050
	21st to end	Night	9% 7% 40% 33% 10% 2	1050
December	1st to 10th	Night	8% 8% 36% 33% 11% 3	1050
	11th to 20th	Night	6% 8% 41% 35% 9% 1	1050
	21st to end	Night	9% 7% 36% 34% 11% 2	1155

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

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