Lexington Trails
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lexington Trails clear sky chart from 2005-11-06 to 2026-04-02.

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	15% 9% 3 7% 5% 4 5% 4 5% 7% 36%	131840
	Night	15% 10% 3 8% 5% 4 4 3 5% 7% 37%	129926
Transparency	Day	46% 4 10% 23% 15% 2	135493
	Night	46% 4 10% 22% 16% 2	134343
Seeing	Day	19% 13% 27% 22% 13% 6%	17087
	Night	19% 11% 25% 27% 15% 2	26744

By Month

Percentage Cloud Cover SE (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	16% 16% 7% 9% 4 3 4 3 4 5% 27%	4793
	11th to 20th	Day	12% 12% 4 16% 5% 4 3 2 3 4 34%	5280
	21st to end	Day	18% 13% 6% 9% 6% 5% 5% 3 4 5% 25%	5780
February	1st to 10th	Day	18% 14% 4 8% 4 3 3 2 4 5% 33%	2032
	11th to 20th	Day	18% 12% 4 8% 6% 4 4 3 4 5% 33%	2048
	21st to end	Day	18% 12% 4 8% 4 4 4 3 4 7% 32%	1730
March	1st to 10th	Day	19% 14% 4 7% 4 3 3 3 3 5% 35%	4613
	11th to 20th	Day	13% 9% 3 6% 4 4 4 4 6% 7% 40%	5090
	21st to end	Day	17% 9% 3 6% 4 4 5% 4 5% 7% 35%	5586
April	1st to 10th	Day	17% 9% 2 7% 4 4 4 4 5% 8% 36%	2379
	11th to 20th	Day	17% 8% 2 6% 4 4 4 4 5% 6% 39%	2408
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 3 5% 6% 37%	2600
May	1st to 10th	Day	20% 9% 2 8% 5% 5% 5% 4 7% 8% 27%	5862
	11th to 20th	Day	20% 9% 2 7% 4 4 4 4 5% 7% 33%	5861
	21st to end	Day	14% 7% 2 8% 5% 6% 6% 5% 7% 9% 31%	6433
June	1st to 10th	Day	12% 6% 2 6% 6% 5% 5% 4 6% 7% 41%	2600
	11th to 20th	Day	9% 5% 2 6% 6% 5% 6% 4 6% 8% 43%	2758
	21st to end	Day	9% 5% 3 6% 5% 6% 5% 4 6% 9% 41%	2800
July	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 6% 9% 41%	6360
	11th to 20th	Day	10% 5% 2 6% 5% 5% 6% 5% 8% 11% 37%	6051
	21st to end	Day	11% 7% 4 8% 6% 6% 7% 5% 8% 8% 29%	6424
August	1st to 10th	Day	8% 4 2 6% 4 4 5% 4 7% 10% 45%	4234
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 11% 40%	4149
	21st to end	Day	6% 4 2 5% 4 4 5% 4 6% 8% 54%	4312
September	1st to 10th	Day	13% 5% 2 6% 4 5% 5% 3 4 7% 47%	2280
	11th to 20th	Day	8% 4 2 7% 4 4 4 3 6% 8% 50%	2200
	21st to end	Day	16% 6% 2 6% 4 3 4 3 4 6% 47%	2200
October	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 5% 6% 52%	2200
	11th to 20th	Day	13% 6% 2 6% 4 3 4 3 5% 6% 48%	2048
	21st to end	Day	20% 7% 2 6% 4 4 3 3 4 7% 40%	2049
November	1st to 10th	Day	11% 7% 2 5% 3 3 3 3 3 5% 53%	1852
	11th to 20th	Day	15% 12% 3 7% 4 4 4 3 4 6% 39%	1890
	21st to end	Day	19% 12% 4 6% 4 4 3 3 4 5% 37%	1890
December	1st to 10th	Day	18% 12% 4 6% 5% 3 3 3 3 4 39%	3020
	11th to 20th	Day	18% 14% 5% 8% 5% 5% 4 4 4 4 29%	3463
	21st to end	Day	22% 18% 4 9% 5% 5% 4 3 4 5% 20%	4565
January	1st to 10th	Night	14% 15% 5% 14% 6% 5% 4 3 5% 6% 24%	8001
	11th to 20th	Night	13% 14% 6% 14% 6% 4 4 3 4 4 27%	7680
	21st to end	Night	18% 12% 4 9% 6% 4 3 3 4 5% 33%	8401
February	1st to 10th	Night	20% 13% 5% 9% 4 4 3 3 5% 5% 28%	2584
	11th to 20th	Night	19% 12% 4 9% 5% 4 4 3 4 5% 32%	2458
	21st to end	Night	21% 13% 4 8% 5% 3 3 3 4 5% 31%	2076
March	1st to 10th	Night	19% 14% 3 6% 4 4 3 3 4 5% 36%	5459
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 7% 44%	5090
	21st to end	Night	17% 9% 3 9% 5% 5% 5% 3 5% 7% 32%	5588
April	1st to 10th	Night	15% 8% 3 6% 4 5% 6% 4 6% 7% 37%	2062
	11th to 20th	Night	15% 8% 3 6% 4 4 4 3 5% 6% 41%	1939
	21st to end	Night	17% 8% 2 7% 4 4 4 4 5% 8% 37%	1800
May	1st to 10th	Night	19% 12% 4 7% 5% 5% 4 4 5% 7% 28%	4033
	11th to 20th	Night	17% 7% 2 7% 5% 5% 5% 5% 7% 9% 32%	4032
	21st to end	Night	13% 7% 2 6% 5% 4 4 4 7% 8% 38%	4421
June	1st to 10th	Night	9% 4 2 5% 5% 4 4 4 6% 8% 50%	1800
	11th to 20th	Night	8% 5% 2 6% 4 4 3 3 6% 11% 46%	1635
	21st to end	Night	6% 5% 1 5% 3 5% 5% 5% 8% 9% 48%	1600
July	1st to 10th	Night	8% 5% 2 6% 5% 4 4 3 6% 8% 48%	3618
	11th to 20th	Night	8% 5% 2 7% 5% 5% 5% 4 6% 10% 42%	3894
	21st to end	Night	10% 6% 3 7% 6% 5% 6% 5% 6% 10% 37%	4427
August	1st to 10th	Night	8% 5% 2 6% 3 4 5% 3 6% 10% 48%	2915
	11th to 20th	Night	7% 6% 3 7% 4 5% 4 4 7% 9% 45%	2897
	21st to end	Night	4 3 1 5% 2 3 3 3 5% 9% 61%	3586
September	1st to 10th	Night	12% 4 2 5% 3 3 3 3 5% 8% 52%	2099
	11th to 20th	Night	8% 5% 1 5% 3 3 4 3 5% 9% 53%	2200
	21st to end	Night	14% 5% 2 6% 3 4 4 2 4 6% 50%	2200
October	1st to 10th	Night	9% 5% 2 4 3 4 3 3 5% 6% 56%	2200
	11th to 20th	Night	13% 6% 2 5% 3 4 4 3 5% 6% 48%	2350
	21st to end	Night	18% 8% 2 5% 3 4 4 3 4 5% 42%	2790
November	1st to 10th	Night	13% 7% 2 5% 3 3 3 3 5% 6% 49%	2666
	11th to 20th	Night	15% 9% 3 6% 4 4 3 3 5% 7% 41%	2730
	21st to end	Night	20% 12% 3 6% 4 4 4 3 4 6% 35%	2730
December	1st to 10th	Night	18% 12% 3 8% 4 3 3 2 3 4 38%	4380
	11th to 20th	Night	20% 14% 5% 8% 4 4 3 3 4 6% 30%	4952
	21st to end	Night	21% 19% 6% 10% 5% 5% 4 3 4 5% 18%	6633

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	60% 2 11% 19% 8%	4794
	11th to 20th	Day	56% 2 7% 18% 15% 3	5280
	21st to end	Day	62% 2 8% 19% 6% 3	5780
February	1st to 10th	Day	55% 3 8% 22% 10% 1	2032
	11th to 20th	Day	55% 3 8% 21% 11% 2	2058
	21st to end	Day	53% 2 10% 22% 10% 2	1730
March	1st to 10th	Day	53% 2 6% 18% 14% 6%	4613
	11th to 20th	Day	43% 3 9% 27% 16% 2	5090
	21st to end	Day	48% 3 13% 21% 13% 1	5586
April	1st to 10th	Day	47% 4 10% 23% 14% 2	2379
	11th to 20th	Day	46% 3 9% 23% 16% 3	2408
	21st to end	Day	48% 4 10% 24% 12% 2	2600
May	1st to 10th	Day	53% 5% 12% 18% 10% 1	5897
	11th to 20th	Day	51% 4 11% 23% 11%	5865
	21st to end	Day	46% 5% 13% 21% 13% 1	6447
June	1st to 10th	Day	41% 5% 10% 24% 18% 2	2600
	11th to 20th	Day	39% 5% 14% 22% 18% 2	2758
	21st to end	Day	38% 6% 13% 22% 16% 4	2800
July	1st to 10th	Day	39% 5% 10% 24% 20% 1	6291
	11th to 20th	Day	39% 8% 14% 26% 13% 1	5978
	21st to end	Day	49% 8% 11% 18% 12% 1	6240
August	1st to 10th	Day	33% 6% 14% 35% 12% 1	4221
	11th to 20th	Day	36% 5% 11% 32% 14% 1	4188
	21st to end	Day	28% 5% 13% 31% 21% 3	4311
September	1st to 10th	Day	37% 5% 10% 22% 20% 6%	2280
	11th to 20th	Day	32% 5% 11% 25% 25% 3	2200
	21st to end	Day	39% 4 9% 23% 23% 2	2200
October	1st to 10th	Day	22% 3 7% 30% 35% 3	3590
	11th to 20th	Day	29% 3 8% 29% 29% 2	3314
	21st to end	Day	35% 2 10% 27% 24% 3	3286
November	1st to 10th	Day	34% 3 9% 29% 21% 3	1852
	11th to 20th	Day	47% 3 7% 23% 18% 3	1890
	21st to end	Day	51% 3 8% 23% 16% 1	1890
December	1st to 10th	Day	50% 2 9% 24% 14%	3020
	11th to 20th	Day	60% 3 8% 20% 9% 1	3460
	21st to end	Day	67% 3 10% 13% 7% 1	4565
January	1st to 10th	Night	62% 3 9% 17% 8%	8002
	11th to 20th	Night	61% 3 6% 14% 13% 3	7680
	21st to end	Night	55% 2 9% 21% 11% 1	8401
February	1st to 10th	Night	59% 3 10% 20% 8% 1	2584
	11th to 20th	Night	56% 3 8% 21% 12% 1	2459
	21st to end	Night	56% 3 11% 17% 11% 3	2076
March	1st to 10th	Night	52% 2 5% 24% 13% 3	5459
	11th to 20th	Night	40% 3 9% 27% 19% 1	5090
	21st to end	Night	52% 4 7% 25% 12% 1	5588
April	1st to 10th	Night	46% 5% 11% 22% 15% 2	2062
	11th to 20th	Night	43% 3 9% 20% 19% 6%	1939
	21st to end	Night	45% 4 11% 23% 14% 3	1800
May	1st to 10th	Night	55% 5% 11% 19% 8% 2	4060
	11th to 20th	Night	48% 6% 13% 24% 9% 1	4033
	21st to end	Night	40% 6% 17% 21% 13% 3	4429
June	1st to 10th	Night	32% 4 14% 27% 20% 4	1800
	11th to 20th	Night	32% 5% 15% 23% 20% 4	1635
	21st to end	Night	29% 8% 17% 23% 18% 5%	1600
July	1st to 10th	Night	34% 6% 11% 24% 22% 3	3580
	11th to 20th	Night	36% 8% 14% 26% 14% 2	3847
	21st to end	Night	41% 7% 13% 23% 14% 2	4297
August	1st to 10th	Night	32% 5% 14% 34% 12% 1	2904
	11th to 20th	Night	34% 6% 10% 31% 18% 1	2924
	21st to end	Night	21% 4 14% 35% 22% 4	3586
September	1st to 10th	Night	31% 4 13% 24% 22% 6%	2099
	11th to 20th	Night	28% 5% 10% 26% 26% 4	2200
	21st to end	Night	36% 4 8% 23% 25% 3	2200
October	1st to 10th	Night	22% 3 6% 24% 42% 3	3590
	11th to 20th	Night	26% 3 8% 25% 35% 3	3823
	21st to end	Night	33% 2 7% 22% 28% 7%	4503
November	1st to 10th	Night	37% 3 9% 24% 24% 4	2666
	11th to 20th	Night	44% 3 8% 21% 20% 4	2730
	21st to end	Night	52% 2 10% 21% 13% 1	2730
December	1st to 10th	Night	51% 2 10% 23% 12%	4380
	11th to 20th	Night	57% 2 12% 19% 10% 1	4954
	21st to end	Night	69% 3 8% 14% 5%	6633

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	25% 23% 35% 12% 4 1	330
	11th to 20th	Day	29% 30% 31% 10% 1	330
	21st to end	Day	28% 28% 32% 10% 1	363
February	1st to 10th	Day	29% 24% 33% 11% 2	330
	11th to 20th	Day	32% 29% 31% 6% 2 1	330
	21st to end	Day	32% 19% 39% 8% 2	273
March	1st to 10th	Day	26% 28% 34% 9% 3	337
	11th to 20th	Day	28% 22% 31% 13% 5%	540
	21st to end	Day	30% 22% 29% 15% 4	594
April	1st to 10th	Day	25% 20% 30% 16% 8% 1	504
	11th to 20th	Day	25% 18% 29% 18% 7% 3	492
	21st to end	Day	23% 16% 37% 15% 8% 1	500
May	1st to 10th	Day	25% 13% 34% 16% 8% 4	503
	11th to 20th	Day	22% 11% 28% 24% 10% 5%	527
	21st to end	Day	15% 11% 27% 24% 15% 7%	573
June	1st to 10th	Day	14% 9% 24% 30% 16% 6%	530
	11th to 20th	Day	10% 9% 25% 32% 17% 7%	688
	21st to end	Day	11% 7% 28% 28% 18% 8%	730
July	1st to 10th	Day	15% 4 19% 27% 22% 14%	721
	11th to 20th	Day	10% 5% 21% 31% 21% 11%	593
	21st to end	Day	12% 3 17% 33% 22% 13%	576
August	1st to 10th	Day	11% 4 18% 30% 23% 15%	526
	11th to 20th	Day	11% 3 19% 34% 22% 10%	519
	21st to end	Day	9% 4 16% 33% 25% 13%	583
September	1st to 10th	Day	13% 5% 17% 30% 26% 9%	530
	11th to 20th	Day	9% 4 16% 30% 26% 15%	530
	21st to end	Day	21% 7% 21% 22% 22% 7%	530
October	1st to 10th	Day	11% 8% 25% 28% 21% 7%	530
	11th to 20th	Day	17% 14% 31% 21% 13% 4	530
	21st to end	Day	22% 13% 37% 22% 5% 1	432
November	1st to 10th	Day	17% 15% 36% 24% 5% 3	330
	11th to 20th	Day	24% 23% 28% 20% 4 1	330
	21st to end	Day	29% 16% 35% 16% 3	330
December	1st to 10th	Day	26% 22% 37% 11% 4	330
	11th to 20th	Day	24% 22% 36% 14% 5%	330
	21st to end	Day	30% 19% 35% 12% 3	363
January	1st to 10th	Night	22% 22% 31% 20% 4	974
	11th to 20th	Night	30% 21% 31% 16% 2	840
	21st to end	Night	25% 19% 34% 20% 2	924
February	1st to 10th	Night	28% 15% 33% 22% 2	840
	11th to 20th	Night	27% 21% 31% 20% 1	823
	21st to end	Night	30% 16% 36% 17% 1	692
March	1st to 10th	Night	27% 17% 29% 24% 4	840
	11th to 20th	Night	25% 17% 31% 20% 6% 1	840
	21st to end	Night	25% 14% 32% 24% 6%	924
April	1st to 10th	Night	18% 15% 35% 26% 6%	655
	11th to 20th	Night	18% 14% 32% 25% 9% 1	593
	21st to end	Night	19% 10% 35% 28% 7% 1	600
May	1st to 10th	Night	21% 11% 30% 25% 13% 1	600
	11th to 20th	Night	19% 7% 21% 33% 17% 2	591
	21st to end	Night	11% 3 23% 34% 25% 4	650
June	1st to 10th	Night	12% 3 20% 39% 24% 3	600
	11th to 20th	Night	10% 4 18% 41% 25% 4	600
	21st to end	Night	7% 4 23% 37% 26% 3	600
July	1st to 10th	Night	13% 2 14% 32% 31% 10%	585
	11th to 20th	Night	7% 2 14% 37% 36% 4	582
	21st to end	Night	11% 2 11% 39% 33% 5%	657
August	1st to 10th	Night	9% 2 9% 37% 38% 5%	597
	11th to 20th	Night	7% 3 10% 39% 35% 6%	594
	21st to end	Night	7% 2 12% 33% 39% 7%	660
September	1st to 10th	Night	13% 3 12% 36% 30% 5%	699
	11th to 20th	Night	9% 4 15% 32% 35% 6%	800
	21st to end	Night	16% 7% 18% 31% 26% 2	800
October	1st to 10th	Night	11% 6% 20% 34% 25% 4	800
	11th to 20th	Night	17% 10% 24% 33% 14% 2	800
	21st to end	Night	21% 12% 30% 25% 11% 1	880
November	1st to 10th	Night	17% 11% 28% 28% 15% 1	820
	11th to 20th	Night	21% 16% 29% 24% 9% 1	840
	21st to end	Night	26% 14% 24% 26% 8% 1	840
December	1st to 10th	Night	29% 15% 30% 21% 5%	840
	11th to 20th	Night	27% 15% 29% 23% 6% 1	840
	21st to end	Night	31% 16% 29% 20% 3	924

Page generated at 2026-03-30 02:18:39. Version ac07

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