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 2025-01-22.

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% 27%	105217
	Night	17% 13% 5% 11% 6% 5% 4 3 5% 5% 26%	104151
Transparency	Day	56% 5% 12% 19% 8% 1	108703
	Night	60% 4 11% 17% 7% 1	108754
Seeing	Day	26% 17% 28% 18% 8% 2	14874
	Night	25% 14% 26% 25% 9% 1	23875

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	14% 19% 8% 20% 7% 5% 5% 2 3 3 14%	2597
	11th to 20th	Day	13% 15% 8% 19% 12% 6% 3 2 4 5% 14%	2600
	21st to end	Day	12% 19% 8% 14% 7% 9% 4 3 4 4 16%	2780
February	1st to 10th	Day	12% 19% 6% 14% 9% 7% 5% 3 4 3 17%	1596
	11th to 20th	Day	11% 19% 7% 16% 8% 5% 5% 4 4 4 17%	1847
	21st to end	Day	12% 18% 5% 12% 8% 7% 4 4 5% 5% 21%	1570
March	1st to 10th	Day	21% 16% 5% 11% 7% 5% 4 3 4 4 22%	3116
	11th to 20th	Day	14% 22% 6% 11% 6% 4 4 2 4 4 23%	3274
	21st to end	Day	16% 15% 6% 11% 4 4 3 2 3 4 32%	4129
April	1st to 10th	Day	20% 17% 4 9% 5% 3 4 3 4 5% 25%	2280
	11th to 20th	Day	18% 13% 3 7% 5% 5% 4 3 4 4 33%	2282
	21st to end	Day	22% 13% 3 8% 5% 4 5% 4 4 6% 27%	2470
May	1st to 10th	Day	24% 10% 3 7% 5% 5% 4 3 5% 6% 28%	4184
	11th to 20th	Day	19% 7% 3 9% 7% 5% 6% 4 6% 7% 29%	4398
	21st to end	Day	14% 7% 3 7% 5% 6% 5% 4 7% 8% 34%	4837
June	1st to 10th	Day	25% 8% 3 6% 5% 4 5% 4 6% 7% 27%	2660
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 4 6% 8% 35%	2660
	21st to end	Day	21% 9% 3 7% 5% 5% 6% 4 6% 6% 29%	2660
July	1st to 10th	Day	13% 7% 3 7% 6% 4 6% 5% 7% 10% 33%	4440
	11th to 20th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 9% 33%	4440
	21st to end	Day	15% 6% 3 6% 4 4 5% 5% 5% 8% 39%	4814
August	1st to 10th	Day	17% 8% 3 8% 6% 6% 6% 5% 7% 8% 28%	4393
	11th to 20th	Day	17% 7% 3 8% 5% 5% 6% 5% 7% 10% 29%	4030
	21st to end	Day	16% 7% 3 6% 4 5% 5% 4 6% 7% 37%	4180
September	1st to 10th	Day	16% 6% 3 6% 4 4 5% 4 5% 8% 40%	2280
	11th to 20th	Day	17% 6% 2 5% 4 4 3 3 4 8% 43%	2137
	21st to end	Day	18% 8% 3 6% 4 4 4 4 6% 9% 35%	2090
October	1st to 10th	Day	21% 11% 3 6% 5% 5% 5% 4 5% 6% 28%	2059
	11th to 20th	Day	18% 12% 3 9% 5% 5% 4 4 6% 6% 28%	1796
	21st to end	Day	24% 18% 5% 8% 4 4 4 3 3 3 25%	1881
November	1st to 10th	Day	16% 15% 5% 8% 5% 5% 4 3 4 6% 28%	1761
	11th to 20th	Day	17% 18% 5% 11% 5% 4 4 4 4 4 24%	1800
	21st to end	Day	18% 19% 6% 12% 6% 5% 3 3 5% 6% 17%	1630
December	1st to 10th	Day	14% 21% 8% 21% 9% 5% 3 3 3 3 11%	2600
	11th to 20th	Day	17% 18% 7% 13% 5% 4 3 3 4 5% 21%	2986
	21st to end	Day	19% 15% 6% 14% 5% 6% 5% 3 5% 4 18%	3960
January	1st to 10th	Night	13% 19% 8% 19% 8% 5% 4 3 4 3 14%	4569
	11th to 20th	Night	10% 16% 8% 18% 11% 7% 5% 3 4 4 14%	4580
	21st to end	Night	13% 20% 7% 15% 7% 6% 4 3 4 4 18%	4899
February	1st to 10th	Night	12% 17% 5% 16% 10% 5% 5% 4 4 4 18%	2580
	11th to 20th	Night	11% 15% 7% 15% 8% 7% 5% 3 5% 4 20%	2218
	21st to end	Night	13% 17% 5% 10% 7% 6% 5% 4 3 5% 26%	1884
March	1st to 10th	Night	21% 15% 5% 8% 5% 5% 4 2 4 4 27%	3724
	11th to 20th	Night	17% 18% 5% 11% 6% 4 4 3 4 4 24%	3685
	21st to end	Night	15% 16% 5% 12% 7% 5% 3 3 3 4 28%	3500
April	1st to 10th	Night	21% 13% 4 8% 5% 4 4 3 5% 5% 28%	1900
	11th to 20th	Night	20% 13% 3 6% 4 4 5% 3 4 5% 33%	1847
	21st to end	Night	21% 11% 3 8% 6% 4 5% 3 4 6% 31%	1710
May	1st to 10th	Night	23% 11% 3 7% 5% 5% 4 4 4 6% 28%	2784
	11th to 20th	Night	21% 9% 3 7% 5% 5% 4 4 6% 5% 31%	2495
	21st to end	Night	16% 6% 3 7% 5% 5% 4 4 5% 7% 38%	2738
June	1st to 10th	Night	25% 8% 2 5% 4 4 4 3 6% 7% 31%	1520
	11th to 20th	Night	18% 7% 3 6% 3 3 5% 5% 7% 7% 37%	1520
	21st to end	Night	20% 8% 3 6% 5% 4 5% 4 7% 8% 31%	1520
July	1st to 10th	Night	11% 8% 3 9% 5% 6% 6% 5% 7% 8% 32%	2520
	11th to 20th	Night	14% 7% 2 7% 5% 5% 5% 4 5% 8% 38%	2520
	21st to end	Night	13% 8% 2 7% 5% 5% 4 4 6% 6% 38%	2739
August	1st to 10th	Night	21% 8% 3 7% 4 4 4 3 5% 8% 33%	2506
	11th to 20th	Night	14% 6% 2 9% 5% 6% 6% 5% 7% 8% 33%	2780
	21st to end	Night	15% 6% 2 7% 4 5% 4 4 5% 7% 40%	3475
September	1st to 10th	Night	16% 5% 2 6% 5% 5% 4 3 5% 7% 41%	1900
	11th to 20th	Night	15% 5% 2 5% 3 4 5% 4 6% 6% 46%	2042
	21st to end	Night	20% 6% 2 5% 4 4 4 3 5% 7% 41%	2090
October	1st to 10th	Night	20% 9% 3 8% 5% 4 4 3 6% 7% 32%	2118
	11th to 20th	Night	19% 11% 3 9% 5% 4 5% 3 5% 5% 29%	2384
	21st to end	Night	23% 13% 4 8% 5% 4 4 4 4 6% 26%	2717
November	1st to 10th	Night	18% 13% 4 7% 6% 5% 5% 3 5% 6% 28%	2537
	11th to 20th	Night	17% 13% 5% 10% 5% 5% 4 2 5% 5% 28%	2600
	21st to end	Night	17% 16% 7% 13% 6% 4 4 3 4 4 22%	2766
December	1st to 10th	Night	15% 22% 9% 20% 7% 5% 4 2 3 3 9%	4580
	11th to 20th	Night	20% 18% 5% 16% 6% 5% 4 3 4 4 14%	5208
	21st to end	Night	18% 17% 5% 12% 7% 5% 5% 3 6% 5% 17%	6996

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	77% 2 10% 9% 1	2598
	11th to 20th	Day	76% 3 7% 10% 3 1	2600
	21st to end	Day	74% 2 9% 11% 4 1	2780
February	1st to 10th	Day	73% 3 6% 12% 5% 1	1596
	11th to 20th	Day	73% 3 8% 10% 5% 1	1856
	21st to end	Day	66% 3 10% 13% 7% 2	1570
March	1st to 10th	Day	68% 3 8% 12% 8% 1	3119
	11th to 20th	Day	67% 3 8% 11% 9% 2	3274
	21st to end	Day	59% 2 6% 17% 15% 2	4129
April	1st to 10th	Day	63% 3 8% 16% 9% 2	2280
	11th to 20th	Day	55% 4 7% 21% 12% 1	2282
	21st to end	Day	59% 4 8% 17% 9% 2	2470
May	1st to 10th	Day	58% 3 11% 19% 8% 1	4198
	11th to 20th	Day	55% 5% 16% 16% 7% 1	4402
	21st to end	Day	46% 5% 13% 24% 10% 1	4837
June	1st to 10th	Day	55% 5% 12% 19% 8% 1	2660
	11th to 20th	Day	47% 5% 12% 24% 11% 1	2660
	21st to end	Day	54% 6% 12% 19% 8%	2660
July	1st to 10th	Day	43% 7% 16% 25% 9%	4370
	11th to 20th	Day	44% 8% 15% 29% 4	4365
	21st to end	Day	43% 7% 13% 30% 7%	4661
August	1st to 10th	Day	52% 7% 16% 20% 5%	4379
	11th to 20th	Day	49% 8% 19% 19% 5%	4069
	21st to end	Day	43% 7% 16% 20% 13% 2	4180
September	1st to 10th	Day	42% 5% 13% 28% 10% 1	2280
	11th to 20th	Day	41% 3 12% 29% 13% 1	2137
	21st to end	Day	45% 6% 15% 23% 10% 1	2090
October	1st to 10th	Day	48% 6% 14% 23% 8%	3423
	11th to 20th	Day	53% 4 15% 22% 6%	2960
	21st to end	Day	53% 3 14% 22% 8% 1	3081
November	1st to 10th	Day	58% 5% 11% 18% 7% 1	1761
	11th to 20th	Day	64% 4 10% 12% 8% 2	1800
	21st to end	Day	68% 4 13% 12% 2	1630
December	1st to 10th	Day	80% 4 8% 7% 2	2600
	11th to 20th	Day	66% 4 8% 16% 5%	2986
	21st to end	Day	70% 3 7% 11% 8%	3960
January	1st to 10th	Night	78% 3 11% 6% 2	4569
	11th to 20th	Night	77% 3 10% 8% 2	4580
	21st to end	Night	74% 3 9% 10% 4 1	4899
February	1st to 10th	Night	70% 4 8% 12% 5%	2580
	11th to 20th	Night	70% 3 8% 14% 6%	2220
	21st to end	Night	63% 4 9% 14% 9% 1	1884
March	1st to 10th	Night	63% 3 9% 15% 7% 2	3734
	11th to 20th	Night	65% 3 8% 13% 9% 1	3686
	21st to end	Night	64% 2 5% 18% 10% 1	3500
April	1st to 10th	Night	60% 3 9% 17% 11% 1	1900
	11th to 20th	Night	55% 4 8% 21% 13% 1	1847
	21st to end	Night	56% 3 9% 18% 12% 2	1710
May	1st to 10th	Night	58% 4 11% 18% 8% 1	2790
	11th to 20th	Night	54% 5% 13% 18% 8% 1	2496
	21st to end	Night	46% 5% 13% 20% 15% 1	2739
June	1st to 10th	Night	52% 4 12% 21% 9% 1	1520
	11th to 20th	Night	44% 6% 13% 24% 10% 3	1520
	21st to end	Night	50% 7% 14% 20% 8% 1	1520
July	1st to 10th	Night	46% 8% 14% 22% 10%	2480
	11th to 20th	Night	43% 6% 15% 29% 6%	2472
	21st to end	Night	45% 7% 15% 24% 9%	2651
August	1st to 10th	Night	50% 6% 14% 25% 4	2496
	11th to 20th	Night	46% 10% 19% 17% 7%	2807
	21st to end	Night	42% 7% 14% 24% 13%	3475
September	1st to 10th	Night	42% 6% 14% 26% 12% 1	1900
	11th to 20th	Night	38% 5% 17% 29% 11% 1	2042
	21st to end	Night	42% 6% 14% 25% 11% 1	2090
October	1st to 10th	Night	51% 6% 12% 24% 8%	3534
	11th to 20th	Night	51% 5% 13% 22% 9%	3959
	21st to end	Night	51% 4 15% 20% 8% 1	4467
November	1st to 10th	Night	59% 4 12% 17% 7% 1	2537
	11th to 20th	Night	60% 4 10% 16% 8% 2	2600
	21st to end	Night	67% 4 11% 14% 4	2766
December	1st to 10th	Night	82% 4 6% 6% 1	4580
	11th to 20th	Night	75% 3 6% 11% 6%	5208
	21st to end	Night	69% 3 8% 13% 6%	6996

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% 23% 31% 16% 5%	200
	11th to 20th	Day	29% 21% 35% 10% 5% 1	200
	21st to end	Day	25% 21% 31% 16% 7% 1	200
February	1st to 10th	Day	38% 25% 24% 9% 3	216
	11th to 20th	Day	26% 29% 31% 11% 3	455
	21st to end	Day	30% 22% 31% 15% 2	382
March	1st to 10th	Day	33% 18% 28% 17% 4	460
	11th to 20th	Day	31% 24% 26% 14% 5%	460
	21st to end	Day	33% 20% 25% 14% 6% 1	506
April	1st to 10th	Day	36% 18% 24% 16% 5% 1	460
	11th to 20th	Day	35% 20% 24% 13% 6% 3	452
	21st to end	Day	33% 16% 31% 13% 5% 2	460
May	1st to 10th	Day	34% 17% 24% 15% 8% 1	463
	11th to 20th	Day	24% 16% 30% 19% 8% 3	487
	21st to end	Day	19% 20% 31% 23% 6% 2	529
June	1st to 10th	Day	31% 13% 30% 18% 7% 1	490
	11th to 20th	Day	22% 14% 31% 22% 9% 2	490
	21st to end	Day	25% 13% 34% 19% 7% 2	490
July	1st to 10th	Day	19% 12% 31% 27% 9% 3	485
	11th to 20th	Day	17% 10% 36% 26% 9% 2	484
	21st to end	Day	19% 11% 35% 26% 10% 1	532
August	1st to 10th	Day	18% 10% 29% 27% 14% 2	486
	11th to 20th	Day	17% 8% 31% 24% 16% 4	479
	21st to end	Day	20% 13% 24% 25% 13% 6%	539
September	1st to 10th	Day	18% 11% 30% 22% 12% 6%	490
	11th to 20th	Day	18% 10% 22% 22% 20% 7%	490
	21st to end	Day	19% 13% 26% 23% 15% 5%	490
October	1st to 10th	Day	25% 17% 23% 17% 12% 6%	490
	11th to 20th	Day	29% 18% 24% 16% 11% 1	435
	21st to end	Day	37% 17% 25% 16% 6%	429
November	1st to 10th	Day	33% 17% 28% 17% 5%	395
	11th to 20th	Day	30% 20% 28% 15% 6% 2	400
	21st to end	Day	33% 20% 31% 13% 3	230
December	1st to 10th	Day	30% 23% 27% 14% 7% 1	200
	11th to 20th	Day	37% 23% 28% 12% 1 1	200
	21st to end	Day	35% 22% 26% 13% 4	220
January	1st to 10th	Night	27% 20% 31% 18% 3	800
	11th to 20th	Night	25% 21% 31% 18% 5%	800
	21st to end	Night	20% 19% 33% 23% 5%	841
February	1st to 10th	Night	25% 19% 29% 23% 4	760
	11th to 20th	Night	22% 22% 32% 20% 3	743
	21st to end	Night	27% 17% 31% 23% 2	628
March	1st to 10th	Night	28% 16% 29% 23% 4	760
	11th to 20th	Night	29% 18% 26% 22% 6%	760
	21st to end	Night	28% 17% 25% 21% 7% 1	836
April	1st to 10th	Night	31% 14% 27% 22% 5%	760
	11th to 20th	Night	28% 16% 26% 22% 7%	723
	21st to end	Night	31% 14% 26% 22% 6%	570
May	1st to 10th	Night	27% 11% 28% 26% 7% 1	546
	11th to 20th	Night	24% 9% 29% 29% 8% 1	374
	21st to end	Night	19% 9% 29% 32% 10%	411
June	1st to 10th	Night	29% 7% 24% 29% 11% 1	380
	11th to 20th	Night	21% 5% 26% 33% 13% 1	380
	21st to end	Night	19% 9% 24% 36% 11%	380
July	1st to 10th	Night	16% 4 29% 35% 15% 1	370
	11th to 20th	Night	14% 4 24% 39% 17% 1	368
	21st to end	Night	15% 4 19% 43% 18%	416
August	1st to 10th	Night	18% 5% 15% 40% 22% 1	378
	11th to 20th	Night	17% 4 22% 36% 19% 2	560
	21st to end	Night	17% 6% 20% 34% 20% 2	835
September	1st to 10th	Night	19% 7% 23% 36% 14% 1	760
	11th to 20th	Night	19% 8% 19% 29% 22% 3	760
	21st to end	Night	22% 9% 27% 24% 17% 2	760
October	1st to 10th	Night	28% 11% 19% 26% 13% 2	760
	11th to 20th	Night	28% 13% 25% 23% 10% 1	760
	21st to end	Night	32% 15% 27% 22% 4	836
November	1st to 10th	Night	28% 16% 30% 21% 5% 1	780
	11th to 20th	Night	26% 18% 28% 18% 9% 1	800
	21st to end	Night	29% 21% 27% 17% 5% 1	800
December	1st to 10th	Night	32% 20% 27% 17% 4	800
	11th to 20th	Night	31% 19% 27% 17% 5%	800
	21st to end	Night	32% 20% 26% 19% 4	880

Page generated at 2025-01-19 03:06:48. Version ac07

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