Claresholm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Claresholm 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	7% 7% 3 7% 5% 5% 5% 4 6% 9% 42%	141958
	Night	6% 8% 3 8% 5% 5% 5% 4 6% 8% 42%	139119
Transparency	Day	36% 8% 15% 25% 13% 3	141663
	Night	38% 8% 16% 24% 12% 2	138997
Seeing	Day	12% 14% 27% 27% 16% 5%	17493
	Night	11% 12% 32% 31% 13% 1	26630

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% 5% 13% 6% 5% 5% 4 6% 9% 35%	4125
	11th to 20th	Day	2 8% 4 8% 6% 6% 5% 4 7% 8% 43%	4317
	21st to end	Day	2 6% 4 11% 5% 5% 5% 4 6% 9% 43%	5186
February	1st to 10th	Day	4 10% 5% 10% 7% 8% 6% 4 7% 7% 33%	1722
	11th to 20th	Day	4 12% 5% 9% 6% 6% 6% 5% 7% 9% 32%	1845
	21st to end	Day	4 11% 6% 9% 8% 5% 5% 5% 6% 8% 35%	1688
March	1st to 10th	Day	3 9% 3 8% 6% 5% 4 4 6% 11% 40%	4618
	11th to 20th	Day	4 9% 3 8% 5% 5% 5% 4 6% 7% 43%	5100
	21st to end	Day	7% 17% 7% 11% 5% 5% 5% 4 6% 9% 24%	5623
April	1st to 10th	Day	7% 14% 4 9% 7% 6% 5% 4 6% 7% 31%	2579
	11th to 20th	Day	10% 13% 4 8% 5% 5% 5% 4 7% 8% 32%	2700
	21st to end	Day	10% 11% 3 7% 6% 5% 5% 4 6% 8% 34%	2730
May	1st to 10th	Day	11% 10% 3 6% 4 4 4 4 6% 8% 41%	7768
	11th to 20th	Day	10% 8% 3 9% 6% 7% 7% 5% 7% 9% 30%	8755
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 9% 38%	9649
June	1st to 10th	Day	13% 8% 2 7% 5% 6% 6% 4 6% 8% 34%	3150
	11th to 20th	Day	16% 8% 2 6% 6% 5% 6% 5% 7% 8% 30%	3150
	21st to end	Day	8% 4 2 5% 4 5% 6% 5% 7% 8% 46%	3150
July	1st to 10th	Day	7% 4 2 5% 3 4 4 4 7% 8% 52%	6781
	11th to 20th	Day	7% 3 1 4 4 4 5% 4 7% 10% 51%	6780
	21st to end	Day	6% 3 2 4 3 3 4 4 6% 8% 57%	7113
August	1st to 10th	Day	8% 5% 2 5% 4 5% 5% 4 7% 10% 46%	4510
	11th to 20th	Day	6% 3 2 4 4 4 5% 4 6% 9% 52%	4158
	21st to end	Day	8% 2 1 4 3 3 4 4 6% 8% 57%	4664
September	1st to 10th	Day	10% 5% 2 5% 3 4 4 2 5% 6% 54%	2460
	11th to 20th	Day	12% 5% 2 5% 3 4 4 3 5% 8% 50%	2200
	21st to end	Day	9% 6% 2 4 4 4 4 4 5% 8% 50%	2200
October	1st to 10th	Day	7% 6% 2 6% 4 4 4 5% 8% 9% 45%	3445
	11th to 20th	Day	5% 7% 2 5% 3 3 4 4 7% 11% 50%	3065
	21st to end	Day	5% 8% 2 6% 4 4 5% 5% 6% 8% 46%	3200
November	1st to 10th	Day	9% 11% 5% 9% 5% 4 3 4 6% 8% 36%	1738
	11th to 20th	Day	4 10% 3 8% 5% 5% 5% 3 6% 9% 43%	1672
	21st to end	Day	4 10% 5% 9% 4 3 4 5% 7% 11% 37%	1470
December	1st to 10th	Day	1 8% 4 10% 6% 5% 5% 4 7% 9% 40%	2360
	11th to 20th	Day	3 8% 4 11% 6% 6% 6% 5% 7% 9% 34%	2712
	21st to end	Day	3 9% 4 11% 5% 4 4 4 5% 8% 42%	3575
January	1st to 10th	Night	3 12% 5% 11% 6% 6% 6% 4 6% 8% 33%	8768
	11th to 20th	Night	2 7% 3 10% 6% 6% 6% 5% 7% 8% 40%	8627
	21st to end	Night	2 7% 5% 11% 6% 5% 6% 4 6% 8% 40%	8994
February	1st to 10th	Night	4 10% 4 12% 6% 6% 6% 4 6% 8% 33%	2898
	11th to 20th	Night	4 13% 5% 11% 6% 5% 6% 5% 6% 8% 32%	2662
	21st to end	Night	3 12% 5% 9% 7% 5% 4 4 5% 7% 38%	2116
March	1st to 10th	Night	2 7% 4 11% 7% 5% 5% 3 6% 11% 39%	5496
	11th to 20th	Night	3 8% 3 10% 5% 5% 4 4 7% 9% 41%	5118
	21st to end	Night	9% 17% 6% 10% 5% 4 4 4 6% 9% 25%	5578
April	1st to 10th	Night	8% 13% 4 8% 5% 4 4 4 6% 7% 38%	2040
	11th to 20th	Night	9% 10% 3 10% 5% 5% 5% 4 7% 6% 35%	1871
	21st to end	Night	10% 10% 3 10% 6% 5% 5% 5% 6% 5% 37%	1890
May	1st to 10th	Night	12% 11% 3 6% 4 4 4 3 5% 8% 41%	5170
	11th to 20th	Night	10% 7% 3 9% 5% 5% 5% 4 7% 9% 34%	4105
	21st to end	Night	10% 5% 2 7% 5% 5% 5% 4 7% 8% 40%	4522
June	1st to 10th	Night	13% 7% 2 5% 5% 4 5% 5% 6% 7% 40%	1470
	11th to 20th	Night	17% 6% 2 7% 5% 5% 4 4 6% 8% 37%	1470
	21st to end	Night	7% 4 2 4 3 5% 5% 5% 7% 7% 50%	1470
July	1st to 10th	Night	5% 3 1 4 3 4 5% 4 7% 10% 54%	3180
	11th to 20th	Night	6% 3 2 5% 4 4 4 4 6% 8% 54%	3180
	21st to end	Night	7% 4 2 5% 4 3 3 3 5% 6% 57%	3726
August	1st to 10th	Night	8% 4 2 5% 4 5% 5% 4 7% 8% 48%	2641
	11th to 20th	Night	4 4 2 6% 5% 4 6% 5% 7% 10% 47%	2901
	21st to end	Night	6% 3 1 4 3 4 4 3 6% 8% 60%	3245
September	1st to 10th	Night	8% 3 1 5% 3 3 4 3 5% 7% 56%	1936
	11th to 20th	Night	11% 6% 2 4 3 2 3 3 4 7% 54%	2200
	21st to end	Night	9% 6% 2 4 3 3 4 3 6% 7% 52%	2200
October	1st to 10th	Night	7% 5% 1 5% 3 3 4 4 5% 7% 56%	3750
	11th to 20th	Night	5% 5% 2 5% 3 4 5% 4 6% 9% 52%	4078
	21st to end	Night	5% 7% 2 7% 4 4 5% 4 6% 8% 49%	4600
November	1st to 10th	Night	8% 13% 3 7% 5% 4 4 5% 6% 8% 38%	2759
	11th to 20th	Night	3 9% 3 7% 5% 5% 6% 5% 7% 9% 41%	2945
	21st to end	Night	4 11% 4 7% 4 4 4 4 7% 10% 40%	3150
December	1st to 10th	Night	3 9% 3 8% 6% 5% 6% 5% 8% 10% 39%	5040
	11th to 20th	Night	3 9% 5% 9% 6% 6% 6% 5% 8% 9% 33%	5700
	21st to end	Night	4 10% 5% 9% 5% 4 5% 5% 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	44% 9% 14% 20% 11% 3	4125
	11th to 20th	Day	38% 7% 14% 23% 14% 4	4338
	21st to end	Day	34% 9% 13% 30% 13% 1	5187
February	1st to 10th	Day	48% 8% 15% 17% 10% 2	1722
	11th to 20th	Day	45% 9% 15% 19% 9% 3	1854
	21st to end	Day	47% 8% 13% 19% 12% 1	1688
March	1st to 10th	Day	34% 9% 14% 25% 17% 1	4618
	11th to 20th	Day	37% 8% 16% 24% 15% 1	5101
	21st to end	Day	53% 10% 18% 15% 5%	5623
April	1st to 10th	Day	49% 8% 15% 20% 7% 1	2579
	11th to 20th	Day	46% 8% 15% 20% 8% 2	2700
	21st to end	Day	44% 8% 15% 21% 10% 1	2730
May	1st to 10th	Day	40% 6% 10% 26% 16% 2	7768
	11th to 20th	Day	43% 10% 15% 23% 9% 2	8759
	21st to end	Day	37% 10% 16% 27% 10% 1	9650
June	1st to 10th	Day	43% 9% 16% 19% 11% 2	3150
	11th to 20th	Day	47% 9% 14% 19% 10% 2	3150
	21st to end	Day	31% 9% 19% 28% 11% 3	3150
July	1st to 10th	Day	26% 7% 15% 26% 21% 6%	6707
	11th to 20th	Day	26% 8% 19% 30% 14% 3	6699
	21st to end	Day	24% 6% 15% 26% 18% 11%	6913
August	1st to 10th	Day	30% 8% 17% 29% 13% 2	4493
	11th to 20th	Day	26% 8% 21% 33% 10% 2	4197
	21st to end	Day	23% 5% 13% 39% 17% 2	4663
September	1st to 10th	Day	30% 6% 14% 25% 17% 8%	2460
	11th to 20th	Day	33% 8% 14% 28% 14% 3	2200
	21st to end	Day	31% 7% 15% 31% 14% 3	2200
October	1st to 10th	Day	32% 8% 14% 33% 12% 1	3445
	11th to 20th	Day	28% 6% 21% 25% 17% 2	3065
	21st to end	Day	33% 8% 12% 29% 13% 4	3200
November	1st to 10th	Day	46% 8% 13% 22% 11% 1	1738
	11th to 20th	Day	39% 8% 20% 22% 11% 1	1672
	21st to end	Day	39% 9% 19% 21% 9% 2	1470
December	1st to 10th	Day	41% 8% 16% 25% 8% 2	2360
	11th to 20th	Day	44% 9% 20% 20% 6% 1	2714
	21st to end	Day	39% 7% 12% 22% 18% 1	3575
January	1st to 10th	Night	48% 8% 12% 21% 10% 2	8769
	11th to 20th	Night	40% 7% 16% 21% 13% 3	8668
	21st to end	Night	39% 8% 16% 25% 11% 1	8994
February	1st to 10th	Night	47% 9% 13% 16% 13% 2	2898
	11th to 20th	Night	48% 9% 12% 20% 10% 2	2663
	21st to end	Night	46% 7% 14% 21% 10% 2	2116
March	1st to 10th	Night	37% 9% 17% 23% 12% 2	5496
	11th to 20th	Night	36% 10% 17% 23% 13%	5118
	21st to end	Night	54% 8% 16% 15% 6%	5578
April	1st to 10th	Night	43% 9% 14% 23% 11% 1	2040
	11th to 20th	Night	45% 9% 12% 23% 10% 1	1871
	21st to end	Night	45% 9% 13% 22% 9% 2	1890
May	1st to 10th	Night	43% 5% 12% 26% 12% 2	5167
	11th to 20th	Night	39% 11% 13% 26% 9% 1	4105
	21st to end	Night	37% 11% 15% 26% 9% 1	4526
June	1st to 10th	Night	41% 8% 16% 22% 12% 1	1470
	11th to 20th	Night	43% 7% 16% 22% 10% 2	1470
	21st to end	Night	29% 9% 18% 28% 14% 2	1470
July	1st to 10th	Night	24% 8% 20% 21% 21% 6%	3145
	11th to 20th	Night	27% 7% 19% 29% 12% 5%	3138
	21st to end	Night	28% 6% 15% 25% 16% 11%	3621
August	1st to 10th	Night	30% 9% 17% 25% 16% 3	2633
	11th to 20th	Night	30% 9% 17% 28% 14% 2	2928
	21st to end	Night	22% 6% 13% 37% 19% 4	3245
September	1st to 10th	Night	27% 5% 16% 29% 17% 6%	1936
	11th to 20th	Night	30% 6% 14% 27% 17% 4	2200
	21st to end	Night	30% 7% 16% 28% 16% 4	2200
October	1st to 10th	Night	26% 6% 11% 32% 22% 3	3750
	11th to 20th	Night	29% 6% 18% 25% 18% 3	4078
	21st to end	Night	33% 6% 13% 31% 16% 1	4600
November	1st to 10th	Night	43% 8% 15% 21% 11% 1	2759
	11th to 20th	Night	36% 10% 18% 20% 15% 1	2945
	21st to end	Night	38% 8% 21% 20% 10% 3	3150
December	1st to 10th	Night	40% 10% 19% 19% 10% 2	5040
	11th to 20th	Night	43% 11% 22% 18% 6%	5697
	21st to end	Night	39% 8% 14% 23% 13% 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	6% 16% 30% 30% 10% 7%	220
	11th to 20th	Day	10% 16% 31% 25% 13% 4	220
	21st to end	Day	6% 20% 37% 24% 10% 2	242
February	1st to 10th	Day	10% 22% 33% 22% 10% 3	242
	11th to 20th	Day	11% 14% 30% 32% 11% 3	330
	21st to end	Day	12% 22% 30% 25% 10% 1	404
March	1st to 10th	Day	10% 23% 32% 21% 9% 4	540
	11th to 20th	Day	10% 19% 30% 27% 10% 3	540
	21st to end	Day	12% 21% 35% 21% 9% 2	594
April	1st to 10th	Day	13% 21% 31% 22% 10% 2	540
	11th to 20th	Day	16% 16% 29% 21% 15% 3	532
	21st to end	Day	16% 19% 27% 23% 11% 4	540
May	1st to 10th	Day	16% 10% 27% 28% 15% 5%	560
	11th to 20th	Day	17% 10% 21% 27% 19% 6%	775
	21st to end	Day	18% 9% 19% 27% 21% 7%	844
June	1st to 10th	Day	14% 15% 26% 27% 15% 3	780
	11th to 20th	Day	18% 12% 24% 29% 13% 3	780
	21st to end	Day	10% 7% 25% 31% 21% 6%	780
July	1st to 10th	Day	9% 5% 23% 33% 24% 6%	722
	11th to 20th	Day	7% 8% 23% 35% 22% 5%	718
	21st to end	Day	5% 7% 26% 35% 21% 6%	684
August	1st to 10th	Day	9% 8% 21% 33% 23% 7%	527
	11th to 20th	Day	6% 7% 26% 30% 24% 8%	517
	21st to end	Day	9% 10% 25% 28% 19% 9%	583
September	1st to 10th	Day	11% 10% 27% 27% 16% 8%	530
	11th to 20th	Day	13% 10% 24% 28% 17% 7%	530
	21st to end	Day	15% 19% 28% 25% 10% 3	530
October	1st to 10th	Day	15% 12% 23% 26% 19% 6%	440
	11th to 20th	Day	12% 18% 27% 21% 15% 6%	330
	21st to end	Day	15% 21% 26% 25% 10% 2	363
November	1st to 10th	Day	18% 20% 29% 21% 10% 2	330
	11th to 20th	Day	14% 20% 31% 26% 9% 1	324
	21st to end	Day	7% 22% 29% 24% 10% 7%	220
December	1st to 10th	Day	9% 18% 30% 25% 13% 5%	220
	11th to 20th	Day	11% 19% 38% 20% 8% 3	220
	21st to end	Day	11% 14% 30% 29% 13% 4	242
January	1st to 10th	Night	11% 21% 32% 27% 8% 1	1050
	11th to 20th	Night	10% 15% 35% 30% 8% 1	1002
	21st to end	Night	9% 14% 37% 31% 9% 1	924
February	1st to 10th	Night	9% 17% 33% 27% 12% 3	840
	11th to 20th	Night	9% 10% 36% 34% 9% 2	824
	21st to end	Night	10% 12% 32% 29% 16% 2	692
March	1st to 10th	Night	9% 13% 35% 30% 11% 2	840
	11th to 20th	Night	9% 15% 34% 31% 9% 2	840
	21st to end	Night	11% 12% 34% 30% 10% 2	924
April	1st to 10th	Night	13% 12% 34% 29% 10% 2	780
	11th to 20th	Night	15% 10% 35% 29% 10%	623
	21st to end	Night	14% 12% 30% 33% 11% 1	630
May	1st to 10th	Night	14% 10% 27% 33% 15%	599
	11th to 20th	Night	13% 7% 23% 35% 21% 1	414
	21st to end	Night	18% 6% 22% 31% 21% 1	455
June	1st to 10th	Night	15% 10% 26% 34% 14% 2	420
	11th to 20th	Night	18% 7% 29% 31% 14%	420
	21st to end	Night	8% 5% 24% 41% 20% 1	420
July	1st to 10th	Night	8% 4 19% 43% 27% 1	390
	11th to 20th	Night	7% 3 23% 46% 21% 1	388
	21st to end	Night	5% 3 23% 42% 25% 1	438
August	1st to 10th	Night	9% 2 17% 41% 28% 2	417
	11th to 20th	Night	8% 3 20% 43% 25% 2	594
	21st to end	Night	8% 5% 24% 42% 19% 1	660
September	1st to 10th	Night	10% 4 24% 36% 24% 3	697
	11th to 20th	Night	13% 5% 24% 33% 22% 2	800
	21st to end	Night	12% 8% 34% 30% 13% 3	800
October	1st to 10th	Night	14% 9% 26% 33% 17% 2	800
	11th to 20th	Night	12% 11% 31% 30% 14% 2	800
	21st to end	Night	11% 14% 36% 28% 10% 1	880
November	1st to 10th	Night	17% 15% 38% 22% 8%	914
	11th to 20th	Night	11% 20% 38% 24% 6% 2	1050
	21st to end	Night	10% 17% 37% 26% 8% 2	1050
December	1st to 10th	Night	10% 13% 35% 29% 11% 2	1050
	11th to 20th	Night	8% 17% 38% 28% 8% 1	1050
	21st to end	Night	11% 16% 35% 28% 10% 2	1155

Page generated at 2026-06-28 00:10:44. Version ac07

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