Lac Lovering
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Lovering clear sky chart from 2005-11-06 to 2026-05-17.

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	17% 12% 4 10% 6% 5% 5% 4 5% 6% 26%	131814
	Night	16% 13% 5% 11% 7% 6% 5% 3 5% 5% 25%	131015
Transparency	Day	57% 5% 11% 18% 8% 1	135282
	Night	61% 5% 11% 16% 7% 1	135634
Seeing	Day	27% 17% 29% 18% 8% 2	16563
	Night	25% 14% 26% 25% 9% 1	25543

By Month

Percentage Cloud Cover NE (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	11% 17% 10% 20% 8% 7% 5% 2 3 3 13%	4661
	11th to 20th	Day	8% 18% 8% 20% 13% 7% 5% 3 4 4 10%	4650
	21st to end	Day	8% 14% 7% 14% 9% 13% 6% 4 6% 5% 14%	5124
February	1st to 10th	Day	12% 17% 6% 15% 10% 7% 5% 3 4 4 18%	1765
	11th to 20th	Day	11% 18% 7% 17% 9% 5% 4 4 4 4 17%	2047
	21st to end	Day	12% 18% 6% 12% 8% 7% 4 4 4 5% 21%	1730
March	1st to 10th	Day	18% 14% 7% 15% 7% 5% 5% 3 4 3 19%	4576
	11th to 20th	Day	13% 17% 5% 10% 5% 4 5% 3 5% 5% 27%	4779
	21st to end	Day	19% 14% 6% 11% 5% 4 3 2 3 4 27%	6050
April	1st to 10th	Day	20% 17% 5% 9% 5% 3 4 3 4 5% 25%	2520
	11th to 20th	Day	18% 14% 4 8% 5% 5% 4 3 4 4 32%	2525
	21st to end	Day	22% 12% 3 8% 5% 4 5% 4 5% 6% 28%	2730
May	1st to 10th	Day	28% 12% 3 8% 5% 4 4 3 5% 5% 21%	6124
	11th to 20th	Day	19% 8% 3 8% 6% 5% 5% 4 6% 7% 28%	6402
	21st to end	Day	19% 8% 3 7% 5% 5% 5% 4 7% 7% 30%	6949
June	1st to 10th	Day	25% 8% 3 6% 5% 4 5% 4 6% 7% 27%	2800
	11th to 20th	Day	17% 6% 2 6% 5% 5% 5% 4 6% 8% 35%	2800
	21st to end	Day	21% 9% 3 7% 5% 5% 6% 4 6% 7% 29%	2800
July	1st to 10th	Day	14% 7% 3 8% 6% 5% 6% 5% 8% 10% 28%	6360
	11th to 20th	Day	12% 5% 3 7% 5% 5% 6% 5% 7% 9% 36%	6360
	21st to end	Day	14% 6% 2 6% 4 4 5% 5% 5% 9% 41%	6926
August	1st to 10th	Day	17% 8% 3 8% 6% 6% 6% 5% 7% 8% 29%	4532
	11th to 20th	Day	16% 6% 3 8% 5% 6% 6% 5% 7% 10% 29%	4160
	21st to end	Day	16% 7% 2 6% 4 5% 5% 4 6% 7% 37%	4312
September	1st to 10th	Day	15% 5% 3 6% 4 4 5% 4 5% 7% 41%	2400
	11th to 20th	Day	16% 6% 2 5% 3 4 3 3 4 8% 44%	2249
	21st to end	Day	18% 8% 3 6% 4 4 5% 4 6% 9% 35%	2200
October	1st to 10th	Day	20% 11% 3 6% 5% 5% 5% 4 5% 7% 30%	2167
	11th to 20th	Day	18% 12% 3 9% 4 5% 4 4 6% 7% 28%	1890
	21st to end	Day	24% 19% 5% 8% 4 4 4 3 3 3 24%	1980
November	1st to 10th	Day	17% 17% 5% 8% 5% 5% 4 3 4 6% 27%	1851
	11th to 20th	Day	16% 18% 6% 11% 5% 4 4 4 4 4 23%	1890
	21st to end	Day	18% 19% 6% 12% 6% 5% 3 4 5% 6% 16%	1711
December	1st to 10th	Day	13% 20% 8% 21% 9% 5% 3 3 3 3 11%	2680
	11th to 20th	Day	17% 17% 7% 14% 5% 4 3 3 4 5% 20%	3066
	21st to end	Day	18% 15% 6% 14% 5% 6% 5% 3 5% 4 18%	4048
January	1st to 10th	Night	11% 19% 9% 19% 9% 7% 4 2 3 3 14%	8234
	11th to 20th	Night	9% 17% 8% 20% 12% 8% 5% 3 4 4 11%	8235
	21st to end	Night	8% 14% 6% 14% 9% 10% 7% 5% 6% 5% 17%	9057
February	1st to 10th	Night	11% 16% 5% 17% 9% 5% 5% 4 4 5% 19%	2851
	11th to 20th	Night	11% 15% 7% 16% 9% 7% 5% 3 5% 4 20%	2458
	21st to end	Night	12% 17% 5% 10% 7% 6% 5% 4 3 4 26%	2076
March	1st to 10th	Night	18% 14% 5% 11% 6% 6% 4 2 4 4 24%	5484
	11th to 20th	Night	15% 15% 5% 11% 6% 4 4 4 5% 5% 24%	5400
	21st to end	Night	15% 15% 5% 13% 8% 5% 4 3 3 4 24%	5121
April	1st to 10th	Night	21% 13% 5% 8% 5% 4 4 3 4 5% 27%	2100
	11th to 20th	Night	20% 13% 3 7% 4 3 5% 3 4 5% 32%	2044
	21st to end	Night	20% 11% 3 8% 6% 4 4 3 4 6% 32%	1890
May	1st to 10th	Night	26% 13% 4 8% 5% 5% 4 3 4 5% 24%	4079
	11th to 20th	Night	24% 8% 3 7% 5% 5% 4 4 6% 5% 30%	3623
	21st to end	Night	18% 9% 3 8% 5% 5% 4 4 5% 6% 33%	3926
June	1st to 10th	Night	25% 9% 2 5% 4 4 4 3 6% 7% 31%	1600
	11th to 20th	Night	18% 7% 3 6% 4 4 5% 5% 7% 7% 37%	1600
	21st to end	Night	19% 8% 3 6% 5% 4 5% 5% 7% 8% 31%	1600
July	1st to 10th	Night	11% 7% 3 9% 5% 6% 7% 5% 7% 9% 30%	3600
	11th to 20th	Night	15% 7% 2 7% 5% 5% 5% 3 5% 8% 38%	3600
	21st to end	Night	11% 7% 2 7% 5% 5% 5% 5% 7% 7% 40%	3926
August	1st to 10th	Night	20% 8% 3 7% 4 4 4 3 5% 8% 35%	2586
	11th to 20th	Night	13% 6% 2 9% 5% 6% 6% 5% 7% 8% 34%	2870
	21st to end	Night	15% 6% 2 7% 4 5% 4 3 5% 7% 40%	3585
September	1st to 10th	Night	15% 5% 2 6% 5% 5% 4 3 5% 7% 42%	2000
	11th to 20th	Night	15% 5% 2 5% 3 4 5% 4 5% 6% 47%	2150
	21st to end	Night	19% 6% 2 5% 4 4 4 3 5% 7% 41%	2200
October	1st to 10th	Night	20% 8% 2 7% 5% 4 4 3 5% 7% 34%	2230
	11th to 20th	Night	19% 11% 3 9% 5% 4 4 3 5% 5% 30%	2510
	21st to end	Night	23% 13% 4 8% 5% 4 4 4 4 6% 26%	2860
November	1st to 10th	Night	18% 14% 4 7% 6% 5% 5% 3 4 6% 28%	2667
	11th to 20th	Night	17% 14% 6% 11% 5% 4 4 2 4 5% 27%	2730
	21st to end	Night	17% 16% 7% 13% 6% 4 4 3 4 4 21%	2905
December	1st to 10th	Night	14% 22% 8% 20% 8% 5% 4 2 3 3 9%	4720
	11th to 20th	Night	19% 18% 5% 16% 7% 5% 4 3 4 4 14%	5348
	21st to end	Night	18% 17% 5% 12% 7% 5% 5% 3 6% 5% 17%	7150

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	79% 2 10% 8% 1	4662
	11th to 20th	Day	78% 4 7% 8% 3 1	4680
	21st to end	Day	71% 4 8% 10% 8%	5124
February	1st to 10th	Day	72% 3 5% 13% 6% 1	1765
	11th to 20th	Day	72% 3 8% 12% 5% 1	2056
	21st to end	Day	66% 3 9% 13% 7% 2	1730
March	1st to 10th	Day	71% 3 7% 9% 7% 3	4579
	11th to 20th	Day	59% 4 13% 13% 10% 1	4779
	21st to end	Day	62% 3 6% 14% 13% 1	6050
April	1st to 10th	Day	63% 3 8% 17% 9% 1	2520
	11th to 20th	Day	57% 3 7% 20% 13% 1	2525
	21st to end	Day	58% 4 8% 18% 9% 2	2730
May	1st to 10th	Day	65% 4 9% 16% 6%	6135
	11th to 20th	Day	55% 6% 14% 17% 7% 1	6406
	21st to end	Day	51% 6% 12% 21% 9% 1	6949
June	1st to 10th	Day	55% 5% 12% 19% 9% 1	2800
	11th to 20th	Day	46% 6% 11% 25% 11% 1	2800
	21st to end	Day	53% 6% 12% 20% 8% 1	2800
July	1st to 10th	Day	48% 8% 16% 21% 8%	6290
	11th to 20th	Day	41% 9% 14% 28% 8%	6285
	21st to end	Day	39% 7% 14% 33% 8%	6728
August	1st to 10th	Day	51% 7% 15% 21% 6%	4518
	11th to 20th	Day	48% 8% 18% 20% 5%	4199
	21st to end	Day	43% 7% 16% 20% 12% 2	4312
September	1st to 10th	Day	41% 5% 13% 30% 10% 1	2400
	11th to 20th	Day	40% 4 12% 30% 14% 1	2249
	21st to end	Day	45% 6% 15% 22% 11% 1	2200
October	1st to 10th	Day	47% 6% 14% 24% 9%	3531
	11th to 20th	Day	53% 4 15% 22% 6%	3054
	21st to end	Day	53% 3 14% 21% 8% 1	3180
November	1st to 10th	Day	59% 5% 11% 18% 7% 1	1851
	11th to 20th	Day	64% 4 11% 12% 7% 2	1890
	21st to end	Day	69% 4 13% 11% 2	1711
December	1st to 10th	Day	79% 4 8% 7% 2	2680
	11th to 20th	Day	67% 4 8% 16% 5%	3066
	21st to end	Day	70% 3 7% 11% 8%	4048
January	1st to 10th	Night	77% 3 9% 8% 2	8234
	11th to 20th	Night	79% 3 8% 6% 3	8280
	21st to end	Night	69% 4 8% 10% 9%	9057
February	1st to 10th	Night	69% 4 8% 13% 5%	2851
	11th to 20th	Night	70% 3 7% 14% 6%	2460
	21st to end	Night	63% 4 9% 15% 9% 1	2076
March	1st to 10th	Night	66% 3 8% 12% 9% 2	5494
	11th to 20th	Night	61% 4 13% 13% 7% 1	5401
	21st to end	Night	66% 2 5% 16% 10% 1	5121
April	1st to 10th	Night	60% 3 8% 17% 11% 1	2100
	11th to 20th	Night	56% 4 7% 20% 13% 1	2044
	21st to end	Night	55% 3 9% 18% 12% 2	1890
May	1st to 10th	Night	64% 4 10% 15% 6% 1	4085
	11th to 20th	Night	55% 6% 11% 19% 7% 1	3624
	21st to end	Night	52% 6% 12% 19% 11% 1	3927
June	1st to 10th	Night	53% 5% 12% 21% 10% 1	1600
	11th to 20th	Night	45% 6% 12% 23% 11% 3	1600
	21st to end	Night	49% 7% 14% 20% 9% 1	1600
July	1st to 10th	Night	46% 9% 17% 20% 7%	3560
	11th to 20th	Night	43% 7% 14% 29% 8%	3552
	21st to end	Night	40% 8% 16% 27% 9%	3809
August	1st to 10th	Night	49% 6% 14% 26% 5%	2576
	11th to 20th	Night	46% 10% 19% 18% 8%	2897
	21st to end	Night	42% 7% 14% 24% 13%	3585
September	1st to 10th	Night	42% 6% 14% 27% 11% 1	2000
	11th to 20th	Night	37% 5% 16% 30% 12% 1	2150
	21st to end	Night	43% 6% 13% 25% 12% 1	2200
October	1st to 10th	Night	49% 6% 12% 24% 9%	3646
	11th to 20th	Night	50% 5% 13% 22% 9%	4085
	21st to end	Night	52% 4 14% 20% 8% 1	4610
November	1st to 10th	Night	59% 4 12% 17% 7% 1	2667
	11th to 20th	Night	62% 4 10% 15% 8% 2	2730
	21st to end	Night	68% 4 11% 13% 4	2905
December	1st to 10th	Night	82% 4 6% 7% 1	4720
	11th to 20th	Night	75% 3 6% 11% 6%	5348
	21st to end	Night	69% 3 8% 13% 6%	7150

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	26% 22% 32% 16% 4	220
	11th to 20th	Day	29% 22% 34% 10% 4 1	220
	21st to end	Day	27% 20% 32% 14% 5% 1	242
February	1st to 10th	Day	33% 24% 28% 11% 4	265
	11th to 20th	Day	27% 27% 30% 13% 3	535
	21st to end	Day	30% 22% 32% 14% 2	446
March	1st to 10th	Day	32% 20% 29% 15% 4	540
	11th to 20th	Day	33% 23% 26% 13% 4	540
	21st to end	Day	35% 21% 24% 13% 5% 1	594
April	1st to 10th	Day	36% 18% 26% 14% 5% 1	540
	11th to 20th	Day	37% 20% 23% 13% 5% 2	532
	21st to end	Day	33% 17% 30% 13% 5% 2	540
May	1st to 10th	Day	36% 18% 24% 14% 7% 1	543
	11th to 20th	Day	25% 16% 30% 19% 7% 3	551
	21st to end	Day	20% 20% 31% 22% 6% 1	573
June	1st to 10th	Day	31% 13% 31% 18% 7% 1	530
	11th to 20th	Day	21% 14% 32% 21% 9% 2	530
	21st to end	Day	24% 13% 35% 19% 7% 2	530
July	1st to 10th	Day	18% 12% 31% 26% 9% 2	525
	11th to 20th	Day	16% 10% 37% 26% 9% 2	524
	21st to end	Day	18% 12% 35% 25% 10% 1	576
August	1st to 10th	Day	16% 10% 28% 29% 15% 2	526
	11th to 20th	Day	16% 8% 31% 24% 16% 5%	519
	21st to end	Day	20% 14% 25% 24% 13% 5%	583
September	1st to 10th	Day	18% 11% 30% 23% 12% 6%	530
	11th to 20th	Day	18% 9% 22% 23% 20% 8%	530
	21st to end	Day	19% 13% 25% 23% 15% 5%	530
October	1st to 10th	Day	24% 17% 24% 18% 12% 6%	530
	11th to 20th	Day	29% 18% 25% 17% 11% 1	469
	21st to end	Day	37% 17% 25% 16% 6%	462
November	1st to 10th	Day	34% 18% 28% 16% 4	425
	11th to 20th	Day	30% 20% 28% 15% 6% 1	430
	21st to end	Day	33% 22% 30% 12% 2	251
December	1st to 10th	Day	29% 23% 27% 15% 6% 1	220
	11th to 20th	Day	35% 24% 29% 11% 1	220
	21st to end	Day	33% 23% 26% 14% 4	242
January	1st to 10th	Night	27% 20% 32% 18% 3	840
	11th to 20th	Night	25% 22% 31% 18% 5%	840
	21st to end	Night	20% 19% 33% 23% 5%	924
February	1st to 10th	Night	24% 19% 30% 23% 5%	840
	11th to 20th	Night	23% 22% 32% 21% 3	823
	21st to end	Night	27% 17% 31% 23% 2	692
March	1st to 10th	Night	28% 18% 29% 22% 3	840
	11th to 20th	Night	29% 19% 25% 21% 6%	840
	21st to end	Night	28% 18% 26% 21% 6% 1	924
April	1st to 10th	Night	32% 15% 27% 21% 5%	840
	11th to 20th	Night	29% 16% 26% 22% 7%	800
	21st to end	Night	30% 15% 26% 22% 6%	630
May	1st to 10th	Night	27% 13% 28% 25% 7% 1	604
	11th to 20th	Night	24% 9% 29% 29% 9% 1	406
	21st to end	Night	20% 10% 29% 32% 9%	433
June	1st to 10th	Night	29% 7% 25% 29% 10% 1	400
	11th to 20th	Night	22% 6% 27% 33% 13% 1	400
	21st to end	Night	19% 9% 25% 37% 10%	400
July	1st to 10th	Night	16% 4 29% 35% 15% 1	390
	11th to 20th	Night	15% 4 23% 40% 17% 1	388
	21st to end	Night	15% 5% 20% 43% 17%	438
August	1st to 10th	Night	17% 5% 15% 40% 23% 1	398
	11th to 20th	Night	17% 4 22% 36% 20% 2	590
	21st to end	Night	17% 6% 21% 34% 19% 2	879
September	1st to 10th	Night	19% 7% 23% 36% 14% 1	800
	11th to 20th	Night	18% 8% 19% 30% 23% 3	800
	21st to end	Night	22% 9% 27% 24% 17% 2	800
October	1st to 10th	Night	27% 11% 20% 27% 13% 2	800
	11th to 20th	Night	28% 13% 25% 24% 9% 1	800
	21st to end	Night	32% 15% 27% 22% 4	880
November	1st to 10th	Night	29% 16% 29% 20% 5%	820
	11th to 20th	Night	27% 18% 28% 17% 9% 1	840
	21st to end	Night	29% 21% 27% 17% 5% 1	840
December	1st to 10th	Night	32% 20% 27% 17% 4	840
	11th to 20th	Night	31% 20% 27% 17% 5%	840
	21st to end	Night	32% 20% 25% 19% 3	924

Page generated at 2026-05-14 01:58:59. Version ac07

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