Taber
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Taber 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% 7% 3 7% 4 4 5% 4 6% 8% 44%	141946
	Night	6% 9% 3 8% 5% 5% 5% 4 6% 8% 41%	139175
Transparency	Day	37% 5% 14% 28% 14% 3	141645
	Night	40% 5% 15% 25% 12% 2	139059
Seeing	Day	13% 10% 28% 27% 17% 5%	17607
	Night	12% 11% 34% 30% 11% 1	26796

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	4 14% 5% 10% 6% 6% 6% 5% 7% 9% 29%	4125
	11th to 20th	Day	4 10% 4 8% 5% 6% 8% 5% 7% 7% 36%	4135
	21st to end	Day	2 7% 5% 10% 6% 6% 5% 3 5% 7% 44%	5186
February	1st to 10th	Day	7% 13% 4 12% 7% 6% 5% 4 5% 7% 30%	1804
	11th to 20th	Day	6% 12% 3 11% 6% 7% 6% 6% 7% 8% 29%	1845
	21st to end	Day	4 11% 5% 11% 7% 5% 5% 5% 6% 8% 35%	1620
March	1st to 10th	Day	4 10% 4 8% 5% 5% 5% 4 7% 8% 41%	4741
	11th to 20th	Day	5% 8% 3 9% 5% 5% 5% 4 6% 8% 41%	5109
	21st to end	Day	9% 15% 5% 11% 6% 5% 6% 5% 7% 8% 25%	5607
April	1st to 10th	Day	9% 12% 3 9% 5% 5% 6% 4 6% 7% 34%	2560
	11th to 20th	Day	11% 12% 3 8% 5% 4 5% 4 6% 7% 34%	2700
	21st to end	Day	11% 9% 3 7% 6% 4 4 5% 6% 8% 37%	2730
May	1st to 10th	Day	13% 8% 3 5% 4 4 4 4 6% 8% 42%	7864
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 5% 8% 10% 35%	8581
	21st to end	Day	11% 5% 2 6% 4 5% 6% 4 6% 9% 42%	9649
June	1st to 10th	Day	13% 6% 3 6% 5% 5% 4 5% 6% 9% 40%	3150
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 5% 7% 9% 34%	3150
	21st to end	Day	8% 3 1 5% 4 4 4 4 6% 9% 52%	3150
July	1st to 10th	Day	6% 3 1 5% 3 4 4 3 6% 7% 59%	6781
	11th to 20th	Day	7% 3 2 4 3 4 4 3 6% 9% 56%	6780
	21st to end	Day	6% 3 1 3 2 2 3 3 4 7% 65%	7290
August	1st to 10th	Day	8% 5% 2 4 3 3 4 4 6% 9% 51%	4385
	11th to 20th	Day	5% 3 2 5% 4 4 4 4 6% 8% 56%	4158
	21st to end	Day	7% 3 1 3 3 3 3 3 5% 7% 61%	4664
September	1st to 10th	Day	10% 4 1 4 3 3 3 2 5% 6% 58%	2480
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 4 8% 50%	2200
	21st to end	Day	9% 6% 1 5% 4 3 4 4 5% 7% 51%	2200
October	1st to 10th	Day	7% 7% 2 6% 4 4 4 3 7% 8% 47%	3353
	11th to 20th	Day	5% 7% 2 6% 3 4 4 3 6% 8% 52%	3190
	21st to end	Day	7% 6% 2 5% 4 4 4 5% 7% 6% 50%	3200
November	1st to 10th	Day	12% 13% 3 7% 5% 5% 4 4 5% 8% 35%	1678
	11th to 20th	Day	6% 9% 3 8% 6% 5% 5% 4 6% 7% 40%	1680
	21st to end	Day	5% 11% 5% 11% 5% 5% 4 4 7% 10% 34%	1554
December	1st to 10th	Day	6% 14% 4 8% 8% 5% 5% 3 5% 7% 35%	2360
	11th to 20th	Day	4 11% 4 9% 7% 7% 6% 5% 6% 7% 35%	2712
	21st to end	Day	4 9% 4 9% 6% 4 5% 4 5% 7% 42%	3575
January	1st to 10th	Night	4 13% 5% 10% 6% 5% 5% 4 6% 9% 33%	8768
	11th to 20th	Night	4 10% 4 9% 5% 5% 5% 4 6% 7% 40%	8779
	21st to end	Night	3 8% 4 10% 6% 5% 6% 4 6% 7% 41%	9036
February	1st to 10th	Night	7% 13% 4 11% 6% 5% 5% 4 6% 7% 32%	2815
	11th to 20th	Night	6% 12% 4 11% 6% 5% 6% 5% 6% 8% 31%	2662
	21st to end	Night	5% 13% 5% 9% 5% 5% 5% 4 5% 8% 35%	2182
March	1st to 10th	Night	3 8% 4 10% 6% 4 5% 4 7% 10% 39%	5373
	11th to 20th	Night	5% 6% 4 9% 6% 6% 6% 5% 7% 9% 38%	5110
	21st to end	Night	12% 17% 5% 10% 5% 5% 5% 4 6% 8% 24%	5610
April	1st to 10th	Night	9% 12% 4 8% 5% 4 4 5% 6% 7% 35%	2057
	11th to 20th	Night	10% 10% 3 8% 6% 4 5% 4 7% 8% 35%	1871
	21st to end	Night	10% 10% 3 7% 5% 5% 6% 4 7% 7% 35%	1890
May	1st to 10th	Night	14% 9% 3 6% 4 4 4 4 5% 7% 40%	5084
	11th to 20th	Night	10% 7% 3 8% 6% 6% 6% 4 7% 9% 34%	4284
	21st to end	Night	12% 6% 2 7% 6% 6% 6% 4 6% 8% 37%	4522
June	1st to 10th	Night	14% 7% 3 8% 4 4 4 4 6% 8% 39%	1470
	11th to 20th	Night	13% 5% 2 6% 5% 6% 5% 4 7% 8% 37%	1470
	21st to end	Night	7% 3 1 5% 4 5% 5% 5% 7% 9% 49%	1470
July	1st to 10th	Night	5% 2 1 3 4 4 5% 3 6% 9% 56%	3180
	11th to 20th	Night	6% 4 1 4 3 3 4 4 6% 9% 55%	3180
	21st to end	Night	5% 4 2 5% 3 3 3 4 5% 7% 59%	3550
August	1st to 10th	Night	9% 4 2 5% 4 4 4 4 5% 8% 52%	2768
	11th to 20th	Night	4 3 1 5% 4 5% 6% 5% 8% 11% 47%	2901
	21st to end	Night	8% 4 1 4 3 3 3 3 5% 7% 60%	3245
September	1st to 10th	Night	9% 5% 2 5% 3 4 3 4 5% 7% 53%	1918
	11th to 20th	Night	11% 5% 1 5% 4 4 3 3 6% 7% 51%	2200
	21st to end	Night	7% 6% 2 6% 4 4 4 4 6% 7% 51%	2200
October	1st to 10th	Night	7% 5% 2 5% 4 4 4 3 6% 7% 54%	3838
	11th to 20th	Night	6% 7% 2 6% 4 4 4 4 6% 9% 49%	3955
	21st to end	Night	5% 6% 3 7% 5% 5% 6% 4 6% 8% 46%	4600
November	1st to 10th	Night	10% 12% 3 7% 5% 5% 4 4 5% 7% 36%	2820
	11th to 20th	Night	5% 10% 3 8% 5% 5% 5% 4 7% 7% 41%	2940
	21st to end	Night	5% 11% 4 9% 5% 5% 4 4 6% 8% 40%	3064
December	1st to 10th	Night	4 12% 4 9% 7% 6% 7% 5% 7% 7% 33%	5040
	11th to 20th	Night	4 11% 5% 11% 6% 6% 6% 5% 7% 9% 32%	5700
	21st to end	Night	4 9% 4 8% 4 4 5% 4 5% 8% 44%	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	50% 6% 16% 22% 6% 1	4125
	11th to 20th	Day	46% 6% 16% 16% 13% 3	4156
	21st to end	Day	40% 4 16% 30% 8% 1	5187
February	1st to 10th	Day	53% 5% 14% 18% 10% 1	1804
	11th to 20th	Day	50% 6% 13% 20% 9% 1	1854
	21st to end	Day	47% 6% 14% 21% 11% 2	1620
March	1st to 10th	Day	38% 6% 11% 28% 17%	4741
	11th to 20th	Day	39% 5% 17% 25% 13%	5110
	21st to end	Day	55% 8% 15% 15% 6%	5607
April	1st to 10th	Day	47% 7% 13% 24% 9% 1	2560
	11th to 20th	Day	48% 5% 11% 26% 9% 2	2700
	21st to end	Day	44% 5% 14% 25% 11% 1	2730
May	1st to 10th	Day	40% 4 10% 28% 15% 4	7864
	11th to 20th	Day	41% 6% 12% 28% 11% 1	8585
	21st to end	Day	36% 6% 13% 31% 14%	9650
June	1st to 10th	Day	40% 6% 17% 22% 13% 2	3150
	11th to 20th	Day	44% 6% 14% 23% 12% 2	3150
	21st to end	Day	28% 6% 17% 34% 13% 3	3150
July	1st to 10th	Day	25% 4 15% 26% 24% 6%	6707
	11th to 20th	Day	26% 5% 18% 30% 17% 5%	6699
	21st to end	Day	20% 4 13% 31% 20% 12%	7084
August	1st to 10th	Day	27% 5% 12% 35% 18% 2	4368
	11th to 20th	Day	25% 5% 16% 39% 13% 2	4197
	21st to end	Day	22% 4 12% 40% 19% 3	4663
September	1st to 10th	Day	27% 3 13% 29% 18% 9%	2480
	11th to 20th	Day	34% 4 12% 31% 15% 3	2200
	21st to end	Day	32% 5% 13% 32% 15% 3	2200
October	1st to 10th	Day	33% 5% 12% 34% 14% 2	3353
	11th to 20th	Day	30% 5% 16% 32% 16% 1	3190
	21st to end	Day	33% 5% 11% 36% 13% 2	3200
November	1st to 10th	Day	48% 6% 14% 22% 8% 2	1678
	11th to 20th	Day	42% 5% 19% 24% 9% 1	1680
	21st to end	Day	45% 6% 18% 22% 8% 2	1554
December	1st to 10th	Day	50% 5% 15% 23% 5% 2	2360
	11th to 20th	Day	47% 6% 19% 23% 4 1	2714
	21st to end	Day	40% 5% 14% 24% 16% 1	3575
January	1st to 10th	Night	46% 5% 17% 22% 9% 1	8769
	11th to 20th	Night	43% 5% 19% 20% 13% 1	8820
	21st to end	Night	41% 4 17% 27% 10%	9036
February	1st to 10th	Night	50% 5% 13% 18% 12% 1	2815
	11th to 20th	Night	50% 6% 14% 18% 11% 1	2663
	21st to end	Night	47% 4 17% 20% 10% 2	2182
March	1st to 10th	Night	39% 6% 18% 23% 13% 1	5373
	11th to 20th	Night	40% 6% 16% 28% 10%	5110
	21st to end	Night	56% 7% 16% 15% 5% 1	5610
April	1st to 10th	Night	45% 6% 15% 23% 10%	2057
	11th to 20th	Night	44% 6% 12% 24% 13% 1	1871
	21st to end	Night	45% 6% 13% 26% 10% 1	1890
May	1st to 10th	Night	43% 4 9% 29% 11% 4	5081
	11th to 20th	Night	42% 7% 12% 25% 14% 1	4284
	21st to end	Night	41% 9% 11% 28% 10% 1	4526
June	1st to 10th	Night	42% 7% 12% 25% 13% 1	1470
	11th to 20th	Night	41% 6% 14% 24% 12% 2	1470
	21st to end	Night	29% 5% 16% 33% 14% 3	1470
July	1st to 10th	Night	22% 6% 18% 25% 22% 7%	3145
	11th to 20th	Night	26% 5% 16% 29% 17% 6%	3138
	21st to end	Night	25% 3 14% 28% 19% 11%	3451
August	1st to 10th	Night	30% 5% 11% 31% 17% 6%	2760
	11th to 20th	Night	28% 7% 17% 28% 17% 3	2928
	21st to end	Night	24% 4 11% 36% 21% 4	3245
September	1st to 10th	Night	30% 5% 10% 28% 20% 8%	1918
	11th to 20th	Night	31% 5% 13% 28% 17% 6%	2200
	21st to end	Night	31% 4 12% 32% 18% 3	2200
October	1st to 10th	Night	29% 4 11% 35% 18% 3	3838
	11th to 20th	Night	32% 4 15% 30% 16% 3	3955
	21st to end	Night	35% 5% 11% 34% 14% 1	4600
November	1st to 10th	Night	47% 6% 14% 23% 9% 2	2820
	11th to 20th	Night	40% 6% 19% 23% 12%	2940
	21st to end	Night	43% 5% 21% 21% 9% 1	3064
December	1st to 10th	Night	49% 6% 17% 19% 8% 1	5040
	11th to 20th	Night	47% 7% 24% 18% 4 1	5697
	21st to end	Night	38% 4 13% 26% 16% 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	15% 14% 34% 20% 10% 7%	220
	11th to 20th	Day	11% 15% 35% 25% 12% 1	220
	21st to end	Day	10% 17% 38% 25% 7% 2	242
February	1st to 10th	Day	19% 14% 31% 25% 8% 2	286
	11th to 20th	Day	12% 13% 39% 26% 8% 2	330
	21st to end	Day	14% 17% 28% 27% 12% 1	336
March	1st to 10th	Day	12% 15% 35% 23% 11% 4	540
	11th to 20th	Day	14% 14% 31% 25% 12% 4	540
	21st to end	Day	14% 14% 35% 24% 10% 3	594
April	1st to 10th	Day	15% 17% 30% 26% 11% 1	540
	11th to 20th	Day	14% 14% 30% 28% 12% 1	532
	21st to end	Day	17% 12% 24% 29% 15% 4	540
May	1st to 10th	Day	14% 9% 28% 23% 20% 6%	627
	11th to 20th	Day	17% 7% 22% 29% 20% 6%	775
	21st to end	Day	18% 7% 20% 25% 23% 7%	844
June	1st to 10th	Day	16% 10% 24% 28% 17% 5%	780
	11th to 20th	Day	16% 11% 28% 28% 14% 2	780
	21st to end	Day	10% 5% 23% 33% 22% 6%	780
July	1st to 10th	Day	7% 2 23% 33% 28% 8%	722
	11th to 20th	Day	8% 4 25% 37% 20% 5%	718
	21st to end	Day	4 6% 20% 36% 26% 9%	758
August	1st to 10th	Day	7% 4 20% 32% 28% 9%	527
	11th to 20th	Day	6% 3 22% 30% 28% 10%	517
	21st to end	Day	10% 7% 23% 25% 27% 8%	583
September	1st to 10th	Day	11% 9% 26% 28% 22% 5%	530
	11th to 20th	Day	12% 9% 24% 30% 18% 7%	530
	21st to end	Day	13% 11% 32% 27% 11% 5%	530
October	1st to 10th	Day	15% 10% 24% 29% 17% 5%	387
	11th to 20th	Day	13% 15% 31% 25% 13% 3	330
	21st to end	Day	18% 16% 33% 21% 9% 2	363
November	1st to 10th	Day	24% 13% 33% 19% 9% 2	330
	11th to 20th	Day	13% 18% 39% 22% 8% 1	330
	21st to end	Day	11% 19% 33% 22% 10% 5%	264
December	1st to 10th	Day	13% 20% 36% 21% 9% 1	220
	11th to 20th	Day	16% 19% 38% 18% 8% 1	220
	21st to end	Day	17% 12% 31% 26% 9% 4	242
January	1st to 10th	Night	12% 16% 40% 23% 8% 1	1050
	11th to 20th	Night	13% 16% 36% 26% 8% 1	1050
	21st to end	Night	12% 17% 40% 23% 6% 2	940
February	1st to 10th	Night	15% 11% 33% 28% 11% 2	840
	11th to 20th	Night	11% 12% 38% 29% 10% 1	824
	21st to end	Night	13% 11% 31% 28% 14% 2	692
March	1st to 10th	Night	11% 12% 34% 31% 11% 2	840
	11th to 20th	Night	12% 13% 36% 29% 9% 2	840
	21st to end	Night	14% 13% 34% 28% 10% 1	924
April	1st to 10th	Night	14% 11% 38% 26% 10% 1	725
	11th to 20th	Night	17% 7% 36% 31% 9%	623
	21st to end	Night	15% 9% 31% 34% 10% 1	630
May	1st to 10th	Night	13% 8% 30% 32% 17% 1	630
	11th to 20th	Night	12% 6% 28% 36% 16% 1	478
	21st to end	Night	21% 7% 22% 31% 18% 2	455
June	1st to 10th	Night	17% 11% 28% 29% 14% 1	420
	11th to 20th	Night	15% 9% 35% 28% 13%	420
	21st to end	Night	9% 5% 30% 41% 14% 2	420
July	1st to 10th	Night	6% 4 21% 48% 21%	390
	11th to 20th	Night	9% 3 27% 43% 17%	388
	21st to end	Night	5% 4 22% 45% 23% 2	438
August	1st to 10th	Night	8% 2 21% 45% 22% 2	492
	11th to 20th	Night	8% 4 22% 43% 22% 1	594
	21st to end	Night	7% 5% 28% 40% 20% 1	660
September	1st to 10th	Night	11% 5% 26% 42% 15% 2	623
	11th to 20th	Night	13% 5% 25% 37% 19% 1	800
	21st to end	Night	10% 9% 32% 34% 13% 2	800
October	1st to 10th	Night	14% 7% 29% 34% 15% 1	800
	11th to 20th	Night	14% 10% 36% 29% 10% 2	800
	21st to end	Night	11% 17% 38% 26% 9%	880
November	1st to 10th	Night	18% 13% 41% 23% 5%	975
	11th to 20th	Night	12% 17% 43% 22% 6%	1050
	21st to end	Night	10% 13% 42% 27% 7% 1	1050
December	1st to 10th	Night	14% 13% 37% 26% 9% 2	1050
	11th to 20th	Night	10% 15% 40% 25% 7% 1	1050
	21st to end	Night	13% 14% 39% 25% 7% 2	1155

Page generated at 2026-06-28 00:10:42. Version ac07

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