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 2025-02-25.

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 9% 6% 5% 5% 4 6% 8% 35%	112155
	Night	7% 10% 4 10% 6% 5% 6% 4 6% 8% 33%	115175
Transparency	Day	44% 8% 16% 23% 9% 1	111898
	Night	46% 8% 15% 21% 9% 1	115078
Seeing	Day	13% 7% 25% 31% 18% 6%	15674
	Night	13% 6% 29% 35% 15% 2	24928

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 11% 5% 13% 9% 6% 6% 4 6% 7% 29%	3179
	11th to 20th	Day	4 10% 5% 11% 7% 6% 7% 6% 7% 9% 29%	3159
	21st to end	Day	5% 10% 5% 9% 5% 5% 4 4 5% 10% 37%	3889
February	1st to 10th	Day	8% 13% 5% 11% 7% 6% 5% 4 7% 8% 26%	1600
	11th to 20th	Day	6% 15% 5% 12% 7% 7% 6% 5% 6% 6% 26%	1716
	21st to end	Day	4 12% 5% 13% 9% 6% 7% 5% 6% 7% 27%	1529
March	1st to 10th	Day	4 12% 6% 16% 9% 6% 6% 3 5% 7% 25%	3138
	11th to 20th	Day	6% 11% 3 6% 4 4 4 4 7% 11% 40%	3453
	21st to end	Day	8% 19% 6% 14% 5% 5% 4 3 6% 6% 24%	3881
April	1st to 10th	Day	9% 13% 4 9% 7% 5% 6% 4 7% 7% 29%	2356
	11th to 20th	Day	12% 14% 4 9% 6% 5% 5% 4 7% 7% 28%	2440
	21st to end	Day	13% 10% 3 8% 7% 5% 5% 4 5% 9% 31%	2470
May	1st to 10th	Day	17% 12% 4 7% 5% 5% 5% 4 6% 7% 28%	4507
	11th to 20th	Day	12% 11% 3 9% 6% 6% 5% 4 7% 8% 29%	4694
	21st to end	Day	15% 8% 3 9% 6% 6% 6% 5% 7% 8% 27%	5161
June	1st to 10th	Day	16% 7% 3 7% 6% 5% 5% 5% 7% 8% 32%	2850
	11th to 20th	Day	19% 8% 3 8% 6% 6% 5% 5% 7% 7% 25%	2850
	21st to end	Day	10% 5% 2 6% 5% 6% 5% 5% 8% 10% 38%	2850
July	1st to 10th	Day	9% 5% 2 4 3 4 4 4 6% 9% 51%	4740
	11th to 20th	Day	9% 4 1 5% 4 4 4 4 6% 10% 49%	4740
	21st to end	Day	8% 5% 2 5% 3 4 4 4 6% 9% 50%	5138
August	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 8% 43%	4415
	11th to 20th	Day	8% 5% 2 6% 5% 4 6% 5% 8% 10% 41%	4119
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 44%	4521
September	1st to 10th	Day	12% 6% 2 6% 4 5% 6% 4 6% 7% 43%	2391
	11th to 20th	Day	15% 8% 2 6% 3 3 4 3 6% 8% 42%	2090
	21st to end	Day	8% 8% 2 7% 4 4 4 4 6% 8% 44%	2090
October	1st to 10th	Day	8% 8% 3 7% 5% 5% 5% 3 6% 7% 41%	3312
	11th to 20th	Day	8% 8% 3 7% 5% 6% 5% 5% 7% 8% 38%	2889
	21st to end	Day	8% 9% 4 8% 6% 5% 5% 5% 6% 6% 39%	3101
November	1st to 10th	Day	8% 16% 5% 10% 6% 5% 6% 3 7% 7% 27%	1582
	11th to 20th	Day	6% 13% 5% 12% 6% 5% 6% 3 5% 6% 33%	1475
	21st to end	Day	5% 11% 4 12% 7% 6% 6% 4 7% 8% 30%	1400
December	1st to 10th	Day	9% 14% 4 11% 7% 8% 5% 4 6% 8% 24%	2290
	11th to 20th	Day	7% 13% 5% 14% 9% 6% 5% 5% 5% 6% 25%	2642
	21st to end	Day	3 7% 3 10% 7% 5% 5% 4 7% 9% 41%	3498
January	1st to 10th	Night	3 12% 6% 14% 8% 6% 6% 4 6% 7% 25%	6766
	11th to 20th	Night	3 10% 5% 12% 8% 6% 6% 6% 5% 7% 34%	6739
	21st to end	Night	4 12% 4 9% 6% 5% 5% 4 6% 9% 34%	7109
February	1st to 10th	Night	6% 12% 4 13% 8% 7% 5% 5% 6% 7% 27%	2800
	11th to 20th	Night	6% 14% 4 12% 8% 5% 7% 5% 7% 8% 25%	2570
	21st to end	Night	5% 12% 4 9% 8% 6% 6% 4 6% 7% 32%	2017
March	1st to 10th	Night	4 10% 5% 16% 8% 7% 6% 5% 7% 8% 24%	3736
	11th to 20th	Night	6% 9% 3 7% 6% 6% 6% 5% 8% 9% 36%	3526
	21st to end	Night	7% 16% 9% 18% 7% 5% 5% 3 6% 6% 19%	3771
April	1st to 10th	Night	8% 13% 4 9% 6% 6% 6% 4 6% 8% 29%	1824
	11th to 20th	Night	11% 13% 3 10% 6% 6% 5% 5% 6% 7% 28%	1691
	21st to end	Night	11% 11% 4 8% 5% 4 4 4 7% 8% 33%	1710
May	1st to 10th	Night	23% 11% 4 9% 4 4 4 3 5% 5% 27%	2454
	11th to 20th	Night	11% 9% 4 9% 6% 6% 6% 5% 7% 8% 30%	2199
	21st to end	Night	16% 9% 3 10% 6% 7% 7% 6% 6% 8% 22%	2414
June	1st to 10th	Night	18% 9% 3 7% 6% 5% 6% 5% 7% 7% 28%	1330
	11th to 20th	Night	16% 10% 4 9% 5% 6% 6% 6% 7% 7% 23%	1330
	21st to end	Night	8% 6% 2 8% 5% 6% 6% 6% 9% 8% 36%	1330
July	1st to 10th	Night	12% 5% 3 6% 5% 5% 5% 4 6% 8% 42%	2220
	11th to 20th	Night	6% 5% 2 6% 5% 5% 6% 4 6% 10% 45%	2220
	21st to end	Night	9% 6% 2 5% 4 4 5% 4 7% 10% 45%	2414
August	1st to 10th	Night	12% 7% 2 5% 4 4 6% 4 6% 8% 41%	2514
	11th to 20th	Night	8% 6% 2 6% 4 5% 6% 5% 8% 11% 39%	2715
	21st to end	Night	11% 6% 2 6% 4 5% 4 4 7% 9% 42%	3146
September	1st to 10th	Night	11% 5% 2 7% 5% 4 5% 4 6% 6% 44%	1787
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 6% 7% 42%	2090
	21st to end	Night	9% 7% 3 7% 5% 4 5% 3 5% 8% 44%	2090
October	1st to 10th	Night	7% 7% 2 7% 4 5% 5% 4 6% 9% 43%	3662
	11th to 20th	Night	7% 9% 2 8% 5% 5% 6% 4 6% 9% 39%	4024
	21st to end	Night	7% 12% 4 8% 5% 6% 5% 4 6% 8% 35%	4457
November	1st to 10th	Night	9% 15% 4 10% 6% 4 5% 4 6% 7% 29%	2697
	11th to 20th	Night	7% 13% 4 11% 7% 6% 6% 5% 6% 7% 28%	2925
	21st to end	Night	6% 12% 4 11% 7% 5% 5% 4 7% 9% 30%	3000
December	1st to 10th	Night	9% 14% 4 12% 6% 6% 5% 4 5% 7% 26%	4890
	11th to 20th	Night	6% 14% 6% 14% 7% 6% 6% 4 7% 8% 23%	5550
	21st to end	Night	3 8% 3 9% 6% 5% 6% 5% 7% 8% 40%	7458

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	53% 7% 11% 18% 11% 1	3179
	11th to 20th	Day	48% 7% 9% 14% 17% 4	3180
	21st to end	Day	43% 6% 17% 27% 7%	3889
February	1st to 10th	Day	53% 6% 14% 16% 11% 1	1600
	11th to 20th	Day	55% 8% 12% 16% 8% 1	1725
	21st to end	Day	54% 6% 11% 19% 10% 1	1529
March	1st to 10th	Day	56% 8% 13% 14% 9%	3138
	11th to 20th	Day	35% 8% 18% 22% 15% 1	3454
	21st to end	Day	59% 7% 12% 17% 6%	3881
April	1st to 10th	Day	50% 10% 15% 17% 8%	2356
	11th to 20th	Day	51% 8% 12% 20% 9%	2440
	21st to end	Day	49% 9% 13% 22% 6% 2	2470
May	1st to 10th	Day	53% 8% 11% 23% 5%	4507
	11th to 20th	Day	47% 11% 14% 20% 8%	4698
	21st to end	Day	49% 12% 16% 16% 7% 1	5162
June	1st to 10th	Day	46% 10% 16% 21% 7% 1	2850
	11th to 20th	Day	54% 9% 15% 17% 5% 1	2850
	21st to end	Day	38% 12% 22% 23% 6% 1	2850
July	1st to 10th	Day	29% 7% 18% 30% 13% 2	4666
	11th to 20th	Day	30% 8% 18% 35% 9%	4659
	21st to end	Day	29% 8% 19% 27% 14% 2	4976
August	1st to 10th	Day	37% 10% 18% 28% 7%	4397
	11th to 20th	Day	33% 10% 24% 26% 8%	4160
	21st to end	Day	34% 8% 25% 27% 6% 1	4520
September	1st to 10th	Day	38% 7% 20% 23% 9% 3	2391
	11th to 20th	Day	40% 6% 16% 30% 8% 1	2090
	21st to end	Day	37% 8% 17% 24% 11% 3	2090
October	1st to 10th	Day	41% 6% 20% 27% 6% 1	3312
	11th to 20th	Day	41% 7% 17% 23% 11% 1	2889
	21st to end	Day	42% 7% 11% 32% 7%	3101
November	1st to 10th	Day	54% 7% 13% 18% 6% 1	1582
	11th to 20th	Day	51% 7% 13% 20% 9% 1	1475
	21st to end	Day	50% 9% 16% 18% 6% 2	1400
December	1st to 10th	Day	58% 6% 16% 14% 5% 1	2290
	11th to 20th	Day	57% 8% 16% 14% 4 1	2644
	21st to end	Day	38% 6% 11% 25% 16% 3	3498
January	1st to 10th	Night	55% 7% 12% 17% 7% 2	6766
	11th to 20th	Night	48% 6% 12% 15% 15% 3	6780
	21st to end	Night	43% 7% 18% 23% 8% 1	7109
February	1st to 10th	Night	54% 7% 10% 19% 10% 1	2800
	11th to 20th	Night	54% 7% 12% 15% 11% 1	2571
	21st to end	Night	49% 7% 11% 20% 11% 2	2017
March	1st to 10th	Night	52% 8% 12% 19% 8%	3736
	11th to 20th	Night	39% 10% 19% 19% 11% 2	3526
	21st to end	Night	63% 8% 10% 14% 5% 1	3771
April	1st to 10th	Night	49% 9% 13% 18% 9% 1	1824
	11th to 20th	Night	51% 7% 12% 21% 8% 1	1691
	21st to end	Night	44% 8% 17% 22% 8% 1	1710
May	1st to 10th	Night	56% 8% 9% 20% 6%	2454
	11th to 20th	Night	44% 12% 14% 22% 9%	2199
	21st to end	Night	54% 12% 15% 12% 6% 1	2414
June	1st to 10th	Night	51% 10% 13% 18% 7% 1	1330
	11th to 20th	Night	54% 10% 14% 16% 5% 1	1330
	21st to end	Night	40% 10% 19% 23% 7% 1	1330
July	1st to 10th	Night	36% 10% 18% 21% 14% 1	2185
	11th to 20th	Night	32% 10% 17% 31% 8% 3	2178
	21st to end	Night	31% 8% 20% 28% 12% 1	2337
August	1st to 10th	Night	36% 9% 18% 31% 5%	2507
	11th to 20th	Night	34% 11% 23% 24% 6% 1	2740
	21st to end	Night	36% 9% 20% 27% 6% 1	3146
September	1st to 10th	Night	37% 8% 16% 25% 11% 3	1787
	11th to 20th	Night	40% 6% 16% 27% 9% 3	2090
	21st to end	Night	37% 7% 15% 25% 13% 3	2090
October	1st to 10th	Night	37% 7% 20% 25% 11% 1	3662
	11th to 20th	Night	40% 7% 16% 29% 8% 1	4024
	21st to end	Night	45% 7% 15% 26% 6% 1	4457
November	1st to 10th	Night	52% 7% 13% 20% 7% 1	2697
	11th to 20th	Night	51% 7% 13% 18% 9% 1	2925
	21st to end	Night	49% 7% 17% 18% 7% 2	3000
December	1st to 10th	Night	56% 6% 15% 16% 6% 1	4890
	11th to 20th	Night	58% 7% 15% 15% 5%	5547
	21st to end	Night	38% 6% 12% 25% 16% 3	7458

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	5% 10% 25% 36% 17% 8%	200
	11th to 20th	Day	7% 7% 32% 35% 17% 4	200
	21st to end	Day	9% 10% 30% 27% 18% 6%	220
February	1st to 10th	Day	14% 7% 24% 36% 15% 6%	200
	11th to 20th	Day	12% 6% 32% 34% 12% 4	281
	21st to end	Day	7% 5% 31% 37% 15% 6%	317
March	1st to 10th	Day	10% 10% 34% 27% 16% 4	460
	11th to 20th	Day	9% 7% 31% 33% 14% 6%	460
	21st to end	Day	15% 7% 30% 27% 16% 5%	506
April	1st to 10th	Day	13% 12% 33% 28% 10% 4	460
	11th to 20th	Day	17% 10% 25% 29% 13% 5%	452
	21st to end	Day	17% 8% 26% 32% 13% 3	460
May	1st to 10th	Day	16% 10% 23% 31% 16% 4	567
	11th to 20th	Day	11% 8% 21% 36% 20% 3	675
	21st to end	Day	16% 5% 21% 29% 21% 7%	734
June	1st to 10th	Day	18% 7% 23% 35% 15% 3	680
	11th to 20th	Day	21% 8% 23% 27% 17% 5%	680
	21st to end	Day	12% 4 22% 30% 24% 9%	680
July	1st to 10th	Day	13% 5% 14% 34% 24% 9%	671
	11th to 20th	Day	14% 6% 16% 33% 24% 7%	668
	21st to end	Day	8% 4 19% 31% 29% 9%	739
August	1st to 10th	Day	12% 5% 18% 32% 25% 9%	501
	11th to 20th	Day	9% 5% 20% 34% 26% 6%	477
	21st to end	Day	11% 8% 18% 31% 24% 8%	539
September	1st to 10th	Day	14% 8% 26% 27% 21% 4	490
	11th to 20th	Day	20% 6% 24% 26% 19% 4	490
	21st to end	Day	11% 13% 30% 29% 14% 4	490
October	1st to 10th	Day	18% 6% 25% 29% 14% 7%	390
	11th to 20th	Day	10% 11% 31% 31% 14% 3	300
	21st to end	Day	14% 12% 33% 28% 11% 2	330
November	1st to 10th	Day	16% 7% 28% 31% 13% 5%	300
	11th to 20th	Day	14% 6% 37% 31% 12% 1	237
	21st to end	Day	7% 9% 35% 30% 12% 8%	200
December	1st to 10th	Day	13% 5% 35% 25% 17% 6%	200
	11th to 20th	Day	11% 8% 33% 30% 17% 3	200
	21st to end	Day	9% 6% 22% 36% 22% 6%	220
January	1st to 10th	Night	10% 6% 35% 33% 14% 2	1000
	11th to 20th	Night	12% 8% 33% 34% 11% 2	1000
	21st to end	Night	13% 10% 31% 33% 11% 2	946
February	1st to 10th	Night	10% 10% 25% 35% 18% 2	800
	11th to 20th	Night	11% 5% 34% 34% 15% 1	784
	21st to end	Night	10% 5% 26% 38% 17% 4	646
March	1st to 10th	Night	10% 5% 32% 37% 14% 3	760
	11th to 20th	Night	10% 5% 32% 36% 14% 3	760
	21st to end	Night	14% 5% 27% 38% 14% 3	836
April	1st to 10th	Night	13% 7% 31% 32% 15% 2	684
	11th to 20th	Night	15% 8% 28% 37% 11% 1	563
	21st to end	Night	15% 8% 27% 35% 14% 1	570
May	1st to 10th	Night	19% 7% 24% 36% 12% 2	437
	11th to 20th	Night	13% 5% 25% 35% 20% 1	374
	21st to end	Night	22% 6% 20% 33% 16% 3	411
June	1st to 10th	Night	20% 9% 24% 31% 14% 2	380
	11th to 20th	Night	22% 4 25% 33% 16% 1	380
	21st to end	Night	11% 3 22% 39% 22% 2	380
July	1st to 10th	Night	14% 2 13% 46% 24% 2	370
	11th to 20th	Night	11% 3 19% 42% 24% 1	368
	21st to end	Night	10% 6% 14% 39% 30% 2	416
August	1st to 10th	Night	13% 3 18% 33% 30% 3	378
	11th to 20th	Night	11% 5% 16% 42% 24% 2	504
	21st to end	Night	11% 4 20% 41% 23%	627
September	1st to 10th	Night	13% 4 20% 42% 19% 2	636
	11th to 20th	Night	18% 3 20% 39% 18% 1	760
	21st to end	Night	12% 5% 28% 38% 16% 2	760
October	1st to 10th	Night	15% 5% 27% 37% 15% 2	760
	11th to 20th	Night	14% 6% 31% 35% 12% 2	760
	21st to end	Night	14% 9% 31% 35% 11%	836
November	1st to 10th	Night	15% 7% 34% 32% 11% 1	942
	11th to 20th	Night	12% 8% 37% 31% 11% 2	1000
	21st to end	Night	11% 5% 38% 33% 11% 2	1000
December	1st to 10th	Night	13% 7% 33% 31% 13% 3	1000
	11th to 20th	Night	9% 7% 35% 35% 12% 2	1000
	21st to end	Night	11% 3 35% 33% 15% 2	1100

Page generated at 2025-02-22 04:51:36. Version ac07

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