Lacombe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lacombe 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	9% 9% 3 8% 5% 5% 5% 4 6% 8% 36%	142277
	Night	7% 10% 4 10% 6% 5% 6% 4 6% 8% 33%	138804
Transparency	Day	43% 8% 16% 23% 9% 1	141976
	Night	46% 8% 15% 21% 9% 1	138688
Seeing	Day	13% 8% 25% 31% 18% 6%	17549
	Night	13% 6% 29% 35% 15% 2	26574

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 13% 5% 14% 9% 6% 6% 4 6% 7% 28%	4125
	11th to 20th	Day	3 8% 4 10% 6% 6% 6% 5% 7% 9% 35%	4119
	21st to end	Day	4 10% 5% 10% 5% 5% 4 4 5% 9% 37%	5043
February	1st to 10th	Day	7% 12% 5% 11% 7% 5% 5% 4 7% 8% 27%	1680
	11th to 20th	Day	6% 15% 4 11% 7% 6% 5% 5% 7% 6% 27%	1804
	21st to end	Day	4 12% 5% 13% 9% 6% 7% 5% 6% 8% 26%	1644
March	1st to 10th	Day	3 9% 5% 13% 7% 5% 5% 3 6% 10% 34%	4618
	11th to 20th	Day	6% 11% 5% 10% 5% 4 4 4 6% 10% 35%	5059
	21st to end	Day	10% 18% 6% 12% 6% 5% 5% 4 6% 7% 22%	5691
April	1st to 10th	Day	9% 13% 4 9% 7% 6% 6% 5% 7% 7% 29%	2604
	11th to 20th	Day	11% 14% 4 9% 6% 5% 5% 4 7% 7% 28%	2700
	21st to end	Day	13% 11% 3 9% 6% 5% 5% 4 5% 9% 32%	2730
May	1st to 10th	Day	10% 8% 3 6% 5% 5% 5% 4 6% 8% 39%	8356
	11th to 20th	Day	12% 11% 4 10% 6% 6% 6% 4 7% 8% 26%	8755
	21st to end	Day	12% 6% 3 8% 5% 5% 6% 4 6% 8% 35%	9649
June	1st to 10th	Day	16% 7% 3 7% 6% 5% 5% 5% 7% 8% 32%	3150
	11th to 20th	Day	18% 8% 3 8% 6% 6% 5% 5% 7% 7% 25%	3150
	21st to end	Day	11% 5% 2 6% 5% 6% 5% 5% 7% 9% 37%	3150
July	1st to 10th	Day	8% 5% 2 4 3 4 4 4 6% 9% 51%	6781
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 4 7% 9% 43%	6780
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	7376
August	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	4555
	11th to 20th	Day	8% 5% 2 6% 5% 4 6% 5% 8% 10% 40%	4252
	21st to end	Day	10% 5% 2 5% 4 4 5% 4 7% 8% 46%	4664
September	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 6% 7% 44%	2516
	11th to 20th	Day	15% 8% 2 5% 3 3 4 3 6% 8% 44%	2200
	21st to end	Day	8% 8% 2 7% 4 4 4 4 6% 8% 44%	2200
October	1st to 10th	Day	8% 8% 3 7% 5% 5% 5% 3 6% 7% 42%	3417
	11th to 20th	Day	8% 8% 3 7% 5% 6% 5% 5% 7% 8% 39%	2981
	21st to end	Day	8% 9% 4 8% 6% 5% 5% 5% 6% 6% 39%	3200
November	1st to 10th	Day	8% 16% 5% 10% 6% 5% 6% 3 7% 7% 27%	1663
	11th to 20th	Day	5% 13% 5% 11% 6% 5% 6% 3 5% 7% 33%	1548
	21st to end	Day	5% 11% 4 12% 7% 6% 6% 4 7% 8% 30%	1470
December	1st to 10th	Day	9% 14% 4 11% 7% 8% 5% 4 6% 8% 24%	2360
	11th to 20th	Day	7% 13% 5% 14% 9% 6% 5% 5% 5% 6% 25%	2712
	21st to end	Day	3 7% 3 10% 7% 5% 5% 4 7% 9% 40%	3575
January	1st to 10th	Night	6% 13% 6% 14% 8% 6% 6% 4 6% 7% 23%	8768
	11th to 20th	Night	2 9% 5% 10% 7% 6% 5% 5% 6% 7% 38%	8779
	21st to end	Night	4 10% 4 10% 6% 5% 6% 5% 7% 9% 33%	9193
February	1st to 10th	Night	6% 12% 4 12% 8% 7% 6% 5% 6% 7% 28%	2940
	11th to 20th	Night	6% 14% 4 12% 8% 5% 7% 5% 7% 8% 25%	2702
	21st to end	Night	5% 13% 5% 9% 8% 5% 6% 4 6% 7% 32%	2160
March	1st to 10th	Night	3 10% 4 12% 7% 6% 6% 5% 8% 9% 30%	5496
	11th to 20th	Night	4 10% 5% 10% 6% 7% 6% 6% 8% 9% 29%	5160
	21st to end	Night	9% 16% 8% 16% 6% 5% 5% 3 5% 6% 21%	5525
April	1st to 10th	Night	8% 14% 4 9% 6% 6% 6% 4 6% 8% 31%	2016
	11th to 20th	Night	11% 13% 3 10% 6% 6% 5% 5% 7% 7% 28%	1871
	21st to end	Night	11% 11% 4 8% 5% 4 4 4 7% 8% 33%	1890
May	1st to 10th	Night	14% 9% 3 8% 4 4 4 4 6% 6% 37%	4570
	11th to 20th	Night	12% 10% 4 11% 6% 6% 6% 5% 7% 8% 26%	4105
	21st to end	Night	11% 7% 3 9% 5% 6% 6% 5% 6% 9% 33%	4522
June	1st to 10th	Night	18% 9% 3 7% 6% 5% 5% 5% 7% 7% 27%	1470
	11th to 20th	Night	15% 10% 4 9% 6% 6% 6% 6% 7% 7% 23%	1470
	21st to end	Night	10% 6% 2 8% 6% 5% 6% 6% 8% 8% 36%	1470
July	1st to 10th	Night	10% 5% 3 6% 5% 5% 5% 5% 7% 9% 42%	3180
	11th to 20th	Night	10% 6% 2 7% 5% 5% 6% 3 6% 9% 41%	3180
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 7% 10% 41%	3467
August	1st to 10th	Night	13% 7% 2 5% 4 4 6% 4 6% 8% 41%	2593
	11th to 20th	Night	8% 6% 2 7% 4 5% 6% 5% 8% 11% 39%	2802
	21st to end	Night	11% 6% 2 6% 4 4 4 4 7% 8% 43%	3245
September	1st to 10th	Night	11% 5% 2 7% 5% 5% 5% 4 5% 7% 45%	1882
	11th to 20th	Night	14% 7% 2 5% 4 4 4 4 6% 7% 44%	2200
	21st to end	Night	9% 7% 3 7% 4 4 5% 3 5% 8% 44%	2200
October	1st to 10th	Night	7% 7% 2 7% 4 5% 5% 4 6% 9% 43%	3777
	11th to 20th	Night	7% 9% 2 8% 5% 5% 6% 4 6% 9% 39%	4152
	21st to end	Night	7% 11% 4 8% 5% 6% 5% 4 6% 8% 35%	4600
November	1st to 10th	Night	9% 15% 4 10% 6% 4 5% 4 6% 7% 29%	2835
	11th to 20th	Night	7% 12% 4 11% 7% 7% 6% 5% 6% 7% 28%	3071
	21st to end	Night	6% 13% 4 11% 7% 5% 5% 5% 7% 9% 30%	3150
December	1st to 10th	Night	9% 15% 4 12% 6% 6% 5% 4 5% 7% 26%	5040
	11th to 20th	Night	6% 14% 6% 14% 8% 6% 6% 4 7% 8% 22%	5700
	21st to end	Night	3 8% 3 9% 6% 5% 6% 5% 7% 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	54% 6% 10% 16% 13% 1	4125
	11th to 20th	Day	43% 6% 13% 16% 18% 4	4140
	21st to end	Day	43% 6% 17% 27% 6%	5044
February	1st to 10th	Day	51% 6% 14% 16% 12% 1	1680
	11th to 20th	Day	53% 7% 11% 17% 10% 1	1813
	21st to end	Day	55% 6% 11% 19% 9%	1644
March	1st to 10th	Day	44% 7% 17% 20% 11%	4618
	11th to 20th	Day	42% 8% 14% 21% 14%	5060
	21st to end	Day	58% 7% 10% 17% 7%	5691
April	1st to 10th	Day	50% 10% 14% 17% 8%	2604
	11th to 20th	Day	51% 7% 12% 20% 9% 1	2700
	21st to end	Day	48% 8% 13% 23% 6% 2	2730
May	1st to 10th	Day	40% 7% 12% 28% 12% 1	8356
	11th to 20th	Day	50% 9% 13% 20% 8%	8759
	21st to end	Day	42% 9% 19% 22% 7% 1	9650
June	1st to 10th	Day	46% 9% 16% 21% 7% 1	3150
	11th to 20th	Day	54% 9% 14% 18% 4	3150
	21st to end	Day	39% 11% 21% 23% 5% 1	3150
July	1st to 10th	Day	29% 7% 20% 32% 11% 1	6707
	11th to 20th	Day	36% 8% 19% 30% 7%	6699
	21st to end	Day	35% 8% 19% 26% 10% 1	7169
August	1st to 10th	Day	37% 10% 18% 28% 7%	4537
	11th to 20th	Day	33% 10% 24% 25% 7%	4293
	21st to end	Day	33% 8% 24% 27% 7% 1	4663
September	1st to 10th	Day	36% 7% 20% 25% 9% 3	2516
	11th to 20th	Day	39% 6% 15% 30% 9% 1	2200
	21st to end	Day	37% 8% 17% 25% 10% 3	2200
October	1st to 10th	Day	41% 5% 20% 28% 6% 1	3417
	11th to 20th	Day	41% 7% 16% 23% 12% 1	2981
	21st to end	Day	42% 7% 11% 32% 8%	3200
November	1st to 10th	Day	54% 7% 13% 18% 6% 2	1663
	11th to 20th	Day	50% 7% 14% 20% 9% 1	1548
	21st to end	Day	50% 9% 15% 18% 6% 2	1470
December	1st to 10th	Day	58% 6% 16% 13% 5% 1	2360
	11th to 20th	Day	57% 8% 16% 14% 4 1	2714
	21st to end	Day	38% 6% 11% 25% 16% 3	3575
January	1st to 10th	Night	58% 6% 11% 15% 9% 1	8769
	11th to 20th	Night	43% 6% 16% 18% 14% 3	8820
	21st to end	Night	44% 7% 19% 22% 7%	9193
February	1st to 10th	Night	53% 7% 10% 19% 10% 1	2940
	11th to 20th	Night	53% 7% 11% 15% 12% 1	2703
	21st to end	Night	49% 7% 11% 21% 11% 2	2160
March	1st to 10th	Night	45% 8% 17% 20% 10%	5496
	11th to 20th	Night	45% 9% 16% 20% 9% 1	5160
	21st to end	Night	62% 7% 8% 16% 6%	5525
April	1st to 10th	Night	48% 9% 14% 18% 10% 1	2016
	11th to 20th	Night	51% 7% 12% 21% 8% 1	1871
	21st to end	Night	44% 7% 16% 22% 9% 1	1890
May	1st to 10th	Night	45% 7% 10% 23% 14% 1	4567
	11th to 20th	Night	49% 11% 14% 18% 7%	4105
	21st to end	Night	44% 9% 20% 20% 7%	4526
June	1st to 10th	Night	51% 11% 13% 18% 7% 1	1470
	11th to 20th	Night	55% 10% 14% 16% 5% 1	1470
	21st to end	Night	40% 10% 19% 24% 6% 1	1470
July	1st to 10th	Night	35% 10% 20% 23% 11% 1	3145
	11th to 20th	Night	38% 9% 17% 29% 6% 2	3138
	21st to end	Night	36% 9% 22% 24% 9% 1	3369
August	1st to 10th	Night	37% 9% 18% 30% 5%	2586
	11th to 20th	Night	34% 11% 23% 24% 6% 1	2827
	21st to end	Night	35% 9% 20% 28% 7% 1	3245
September	1st to 10th	Night	37% 7% 16% 26% 11% 3	1882
	11th to 20th	Night	38% 6% 16% 27% 10% 3	2200
	21st to end	Night	36% 7% 15% 26% 13% 3	2200
October	1st to 10th	Night	37% 7% 20% 25% 11% 1	3777
	11th to 20th	Night	39% 7% 16% 29% 9% 1	4152
	21st to end	Night	45% 7% 15% 26% 6% 1	4600
November	1st to 10th	Night	51% 7% 13% 20% 7% 1	2835
	11th to 20th	Night	51% 8% 14% 18% 9% 1	3071
	21st to end	Night	48% 7% 17% 18% 7% 2	3150
December	1st to 10th	Night	57% 6% 15% 16% 6% 1	5040
	11th to 20th	Night	58% 7% 15% 15% 5%	5697
	21st to end	Night	39% 6% 12% 25% 15% 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% 10% 26% 35% 15% 7%	220
	11th to 20th	Day	7% 8% 31% 35% 15% 3	220
	21st to end	Day	9% 10% 30% 28% 17% 6%	242
February	1st to 10th	Day	13% 7% 25% 35% 14% 6%	220
	11th to 20th	Day	12% 6% 31% 34% 14% 4	309
	21st to end	Day	7% 5% 32% 36% 15% 6%	360
March	1st to 10th	Day	9% 10% 34% 28% 15% 4	540
	11th to 20th	Day	9% 8% 33% 31% 13% 5%	540
	21st to end	Day	16% 8% 30% 26% 15% 4	594
April	1st to 10th	Day	14% 12% 31% 29% 11% 5%	540
	11th to 20th	Day	17% 12% 27% 27% 14% 5%	532
	21st to end	Day	16% 9% 26% 31% 14% 4	540
May	1st to 10th	Day	14% 12% 24% 31% 15% 4	658
	11th to 20th	Day	12% 8% 21% 35% 20% 4	775
	21st to end	Day	15% 5% 21% 31% 21% 7%	844
June	1st to 10th	Day	18% 8% 22% 34% 15% 3	780
	11th to 20th	Day	20% 8% 23% 28% 17% 5%	780
	21st to end	Day	14% 4 21% 29% 23% 9%	780
July	1st to 10th	Day	13% 5% 15% 35% 23% 9%	722
	11th to 20th	Day	14% 6% 17% 32% 24% 7%	718
	21st to end	Day	9% 3 18% 31% 29% 9%	794
August	1st to 10th	Day	11% 6% 19% 30% 26% 9%	541
	11th to 20th	Day	9% 5% 22% 33% 25% 6%	517
	21st to end	Day	10% 8% 17% 30% 25% 9%	583
September	1st to 10th	Day	13% 8% 25% 28% 22% 5%	530
	11th to 20th	Day	19% 6% 23% 26% 22% 5%	530
	21st to end	Day	11% 12% 32% 28% 14% 4	530
October	1st to 10th	Day	17% 5% 26% 30% 15% 7%	425
	11th to 20th	Day	9% 11% 32% 30% 14% 3	330
	21st to end	Day	13% 13% 36% 27% 10% 1	363
November	1st to 10th	Day	15% 8% 31% 30% 12% 4	330
	11th to 20th	Day	13% 5% 38% 32% 12% 1	260
	21st to end	Day	7% 8% 35% 31% 12% 7%	220
December	1st to 10th	Day	12% 7% 35% 25% 15% 5%	220
	11th to 20th	Day	11% 8% 36% 28% 15% 2	220
	21st to end	Day	10% 7% 22% 36% 20% 5%	242
January	1st to 10th	Night	11% 6% 35% 33% 13% 2	1050
	11th to 20th	Night	12% 8% 34% 33% 11% 2	1050
	21st to end	Night	12% 10% 31% 33% 11% 2	993
February	1st to 10th	Night	10% 10% 26% 35% 18% 2	840
	11th to 20th	Night	11% 5% 34% 35% 14% 1	824
	21st to end	Night	10% 5% 27% 37% 16% 4	692
March	1st to 10th	Night	9% 5% 32% 38% 13% 3	840
	11th to 20th	Night	10% 5% 33% 36% 13% 3	840
	21st to end	Night	15% 5% 27% 37% 13% 2	924
April	1st to 10th	Night	14% 8% 30% 32% 15% 1	756
	11th to 20th	Night	15% 9% 28% 36% 10% 1	623
	21st to end	Night	16% 9% 27% 35% 14%	630
May	1st to 10th	Night	18% 7% 25% 37% 11% 1	483
	11th to 20th	Night	14% 5% 25% 34% 20% 1	414
	21st to end	Night	21% 6% 21% 33% 17% 3	455
June	1st to 10th	Night	20% 9% 24% 31% 14% 2	420
	11th to 20th	Night	20% 5% 25% 34% 15% 1	420
	21st to end	Night	13% 3 20% 39% 23% 2	420
July	1st to 10th	Night	13% 2 14% 46% 23% 2	390
	11th to 20th	Night	12% 3 19% 42% 23% 1	388
	21st to end	Night	10% 6% 14% 39% 30% 2	438
August	1st to 10th	Night	14% 3 18% 32% 30% 3	398
	11th to 20th	Night	11% 5% 17% 42% 24% 2	531
	21st to end	Night	10% 4 20% 42% 23%	660
September	1st to 10th	Night	12% 4 19% 42% 20% 2	670
	11th to 20th	Night	17% 3 19% 41% 19% 1	800
	21st to end	Night	12% 5% 29% 37% 15% 2	800
October	1st to 10th	Night	14% 5% 27% 37% 15% 2	800
	11th to 20th	Night	14% 7% 31% 35% 12% 2	800
	21st to end	Night	13% 9% 32% 34% 11%	880
November	1st to 10th	Night	15% 8% 34% 32% 10% 1	990
	11th to 20th	Night	12% 8% 36% 32% 11% 2	1050
	21st to end	Night	11% 5% 37% 34% 10% 2	1050
December	1st to 10th	Night	13% 8% 33% 31% 12% 3	1050
	11th to 20th	Night	10% 7% 36% 34% 11% 2	1050
	21st to end	Night	11% 3 35% 33% 14% 2	1155

Page generated at 2026-06-28 00:10:50. Version ac07

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