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 2024-12-09.

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 4 4 5% 7% 38%	101814
	Night	15% 9% 3 7% 4 4 4 3 5% 7% 39%	97886
Transparency	Day	44% 4 10% 24% 16% 2	105511
	Night	44% 4 10% 23% 17% 2	102328
Seeing	Day	19% 13% 27% 23% 13% 6%	15369
	Night	19% 11% 25% 28% 15% 2	24974

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	15% 18% 7% 9% 4 3 4 3 4 6% 27%	2577
	11th to 20th	Day	18% 13% 4 15% 5% 6% 4 2 3 4 27%	2840
	21st to end	Day	27% 16% 8% 7% 4 3 3 2 3 4 22%	3124
February	1st to 10th	Day	18% 15% 4 9% 4 3 3 2 4 5% 32%	1838
	11th to 20th	Day	17% 12% 4 8% 6% 4 4 3 4 5% 33%	1848
	21st to end	Day	20% 12% 4 7% 5% 4 4 3 4 6% 31%	1570
March	1st to 10th	Day	24% 14% 3 7% 4 3 3 2 3 5% 31%	3139
	11th to 20th	Day	14% 8% 3 6% 4 4 4 3 5% 7% 43%	3480
	21st to end	Day	17% 9% 3 6% 4 4 5% 4 5% 7% 37%	3815
April	1st to 10th	Day	16% 9% 2 7% 4 4 4 4 5% 8% 37%	2249
	11th to 20th	Day	18% 8% 2 6% 4 4 3 4 4 6% 40%	2286
	21st to end	Day	17% 7% 3 6% 5% 5% 5% 3 5% 6% 37%	2470
May	1st to 10th	Day	21% 9% 2 8% 5% 4 5% 3 7% 7% 29%	4082
	11th to 20th	Day	21% 8% 2 6% 4 4 4 3 5% 7% 38%	4081
	21st to end	Day	11% 7% 2 8% 5% 6% 6% 5% 8% 9% 34%	4476
June	1st to 10th	Day	12% 6% 2 6% 6% 5% 5% 4 6% 8% 41%	2470
	11th to 20th	Day	9% 5% 2 6% 6% 5% 5% 4 6% 8% 44%	2620
	21st to end	Day	9% 5% 3 6% 5% 6% 5% 4 6% 9% 41%	2660
July	1st to 10th	Day	13% 7% 2 6% 4 4 5% 4 6% 9% 38%	4440
	11th to 20th	Day	8% 4 2 5% 5% 5% 5% 5% 7% 11% 46%	4229
	21st to end	Day	13% 8% 4 9% 6% 6% 6% 5% 7% 8% 28%	4466
August	1st to 10th	Day	8% 4 2 6% 4 4 5% 4 7% 10% 45%	4104
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 11% 40%	4020
	21st to end	Day	6% 4 2 5% 4 4 5% 4 5% 8% 53%	4180
September	1st to 10th	Day	14% 5% 2 6% 4 5% 5% 4 4 7% 46%	2166
	11th to 20th	Day	9% 5% 2 7% 4 4 4 3 6% 8% 49%	2090
	21st to end	Day	16% 6% 2 5% 4 3 3 3 4 6% 47%	2090
October	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 5% 6% 51%	2090
	11th to 20th	Day	13% 7% 2 6% 4 3 4 3 5% 6% 47%	1946
	21st to end	Day	19% 7% 2 6% 4 4 4 3 4 7% 40%	1947
November	1st to 10th	Day	11% 7% 2 5% 3 3 3 3 3 5% 54%	1762
	11th to 20th	Day	15% 11% 3 7% 4 3 4 3 4 6% 40%	1800
	21st to end	Day	18% 11% 4 6% 4 4 3 3 4 5% 38%	1800
December	1st to 10th	Day	21% 14% 4 7% 6% 3 3 4 4 4 30%	1782
	11th to 20th	Day	16% 15% 5% 8% 5% 4 4 4 4 5% 32%	2153
	21st to end	Day	20% 20% 4 9% 6% 5% 4 3 4 5% 21%	3124
January	1st to 10th	Night	15% 17% 6% 11% 5% 4 4 4 4 6% 23%	4308
	11th to 20th	Night	17% 16% 5% 14% 6% 4 3 3 4 4 25%	4120
	21st to end	Night	26% 16% 5% 7% 5% 3 3 2 4 4 25%	4532
February	1st to 10th	Night	21% 13% 5% 9% 4 4 3 3 4 5% 28%	2338
	11th to 20th	Night	18% 11% 3 9% 5% 4 4 3 4 5% 32%	2218
	21st to end	Night	22% 14% 4 8% 5% 3 3 3 4 5% 29%	1884
March	1st to 10th	Night	22% 14% 3 6% 4 4 3 3 4 5% 32%	3713
	11th to 20th	Night	14% 7% 3 5% 3 3 3 3 5% 7% 46%	3480
	21st to end	Night	16% 8% 3 7% 5% 4 4 3 5% 6% 39%	3817
April	1st to 10th	Night	13% 8% 3 6% 4 5% 6% 4 7% 7% 37%	1948
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 5% 6% 41%	1841
	21st to end	Night	18% 8% 2 7% 4 4 4 4 5% 8% 38%	1710
May	1st to 10th	Night	19% 13% 4 8% 5% 5% 4 4 6% 7% 26%	2813
	11th to 20th	Night	18% 7% 2 5% 4 4 4 4 6% 8% 38%	2812
	21st to end	Night	10% 6% 2 5% 4 4 4 5% 7% 9% 45%	3079
June	1st to 10th	Night	9% 4 2 4 5% 4 4 4 6% 9% 49%	1710
	11th to 20th	Night	7% 5% 2 6% 4 4 3 4 7% 12% 47%	1553
	21st to end	Night	6% 5% 1 5% 3 5% 5% 5% 8% 9% 47%	1520
July	1st to 10th	Night	10% 5% 2 6% 5% 4 4 3 5% 8% 47%	2530
	11th to 20th	Night	6% 4 1 6% 4 4 4 4 6% 10% 52%	2729
	21st to end	Night	12% 7% 3 8% 6% 5% 6% 4 6% 9% 35%	3087
August	1st to 10th	Night	8% 4 2 6% 3 4 5% 3 6% 10% 48%	2825
	11th to 20th	Night	7% 6% 3 7% 4 5% 4 4 7% 9% 45%	2806
	21st to end	Night	4 2 1 5% 2 3 4 3 5% 10% 61%	3476
September	1st to 10th	Night	13% 4 2 5% 3 3 3 3 5% 8% 51%	1994
	11th to 20th	Night	8% 5% 1 5% 3 3 4 3 5% 9% 53%	2090
	21st to end	Night	14% 5% 2 6% 3 4 4 2 4 6% 50%	2090
October	1st to 10th	Night	9% 5% 2 4 3 4 3 3 5% 6% 56%	2090
	11th to 20th	Night	14% 6% 2 5% 3 4 4 3 5% 7% 47%	2232
	21st to end	Night	18% 8% 2 5% 3 4 4 3 4 5% 42%	2650
November	1st to 10th	Night	13% 7% 2 5% 3 3 3 3 5% 6% 49%	2536
	11th to 20th	Night	15% 9% 3 6% 4 4 3 3 5% 7% 40%	2600
	21st to end	Night	19% 11% 3 6% 4 4 4 4 4 6% 35%	2600
December	1st to 10th	Night	20% 13% 4 7% 5% 3 4 3 4 5% 32%	2581
	11th to 20th	Night	18% 13% 5% 8% 4 4 3 3 4 6% 33%	3042
	21st to end	Night	19% 19% 5% 10% 6% 5% 4 3 5% 5% 19%	4532

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 12% 15% 10% 1	2578
	11th to 20th	Day	64% 2 7% 18% 8% 1	2840
	21st to end	Day	67% 2 7% 19% 4 1	3124
February	1st to 10th	Day	56% 3 8% 21% 11% 2	1838
	11th to 20th	Day	55% 3 8% 21% 11% 2	1858
	21st to end	Day	54% 3 10% 21% 10% 2	1570
March	1st to 10th	Day	57% 3 8% 18% 10% 4	3139
	11th to 20th	Day	42% 2 11% 26% 17% 2	3480
	21st to end	Day	47% 3 12% 23% 13% 1	3815
April	1st to 10th	Day	46% 4 10% 24% 14% 2	2249
	11th to 20th	Day	45% 3 8% 22% 17% 4	2286
	21st to end	Day	47% 4 10% 24% 12% 2	2470
May	1st to 10th	Day	53% 4 13% 21% 8% 1	4120
	11th to 20th	Day	48% 4 12% 22% 13% 1	4085
	21st to end	Day	43% 6% 14% 19% 17% 2	4489
June	1st to 10th	Day	41% 5% 10% 25% 17% 2	2470
	11th to 20th	Day	37% 5% 14% 23% 18% 2	2620
	21st to end	Day	39% 6% 13% 22% 16% 4	2660
July	1st to 10th	Day	42% 5% 10% 22% 19% 2	4371
	11th to 20th	Day	31% 6% 11% 33% 18% 1	4156
	21st to end	Day	52% 6% 11% 17% 13% 2	4324
August	1st to 10th	Day	32% 6% 14% 35% 12% 1	4091
	11th to 20th	Day	37% 5% 11% 32% 15% 1	4059
	21st to end	Day	28% 5% 14% 30% 20% 3	4179
September	1st to 10th	Day	38% 5% 10% 21% 20% 6%	2166
	11th to 20th	Day	33% 4 11% 25% 23% 3	2090
	21st to end	Day	39% 4 9% 24% 22% 2	2090
October	1st to 10th	Day	22% 3 7% 31% 34% 3	3480
	11th to 20th	Day	29% 3 8% 29% 29% 2	3212
	21st to end	Day	34% 2 10% 27% 24% 3	3184
November	1st to 10th	Day	34% 3 9% 29% 22% 4	1762
	11th to 20th	Day	46% 3 7% 23% 18% 3	1800
	21st to end	Day	50% 3 8% 23% 17% 1	1800
December	1st to 10th	Day	58% 2 10% 19% 9% 1	1782
	11th to 20th	Day	55% 3 8% 20% 14% 1	2150
	21st to end	Day	67% 3 9% 13% 8% 1	3124
January	1st to 10th	Night	62% 3 9% 17% 9% 1	4308
	11th to 20th	Night	65% 2 9% 16% 8% 1	4120
	21st to end	Night	63% 2 8% 18% 8% 1	4532
February	1st to 10th	Night	58% 3 10% 20% 8% 1	2338
	11th to 20th	Night	54% 3 8% 21% 13% 1	2219
	21st to end	Night	58% 3 11% 15% 10% 3	1884
March	1st to 10th	Night	56% 3 6% 22% 11% 1	3713
	11th to 20th	Night	39% 3 11% 27% 18% 2	3480
	21st to end	Night	46% 4 9% 28% 13% 1	3817
April	1st to 10th	Night	44% 5% 10% 23% 15% 2	1948
	11th to 20th	Night	43% 3 9% 19% 20% 6%	1841
	21st to end	Night	46% 4 12% 23% 13% 3	1710
May	1st to 10th	Night	57% 4 11% 19% 7% 2	2840
	11th to 20th	Night	44% 6% 14% 26% 9% 1	2813
	21st to end	Night	32% 7% 15% 25% 17% 4	3087
June	1st to 10th	Night	32% 4 14% 27% 18% 4	1710
	11th to 20th	Night	31% 5% 16% 23% 21% 4	1553
	21st to end	Night	29% 8% 17% 24% 17% 5%	1520
July	1st to 10th	Night	35% 6% 11% 23% 19% 4	2490
	11th to 20th	Night	28% 6% 12% 32% 19% 2	2679
	21st to end	Night	45% 6% 12% 22% 12% 3	2988
August	1st to 10th	Night	32% 5% 14% 35% 13% 2	2814
	11th to 20th	Night	34% 6% 10% 31% 18% 1	2833
	21st to end	Night	21% 4 14% 35% 22% 4	3476
September	1st to 10th	Night	32% 4 13% 24% 21% 6%	1994
	11th to 20th	Night	29% 5% 11% 25% 26% 4	2090
	21st to end	Night	36% 4 8% 24% 25% 3	2090
October	1st to 10th	Night	22% 3 6% 24% 42% 3	3480
	11th to 20th	Night	27% 3 8% 25% 35% 3	3705
	21st to end	Night	33% 2 7% 22% 28% 7%	4363
November	1st to 10th	Night	37% 3 9% 24% 24% 4	2536
	11th to 20th	Night	45% 3 8% 20% 21% 4	2600
	21st to end	Night	51% 3 10% 22% 14% 1	2600
December	1st to 10th	Night	56% 2 10% 21% 11% 1	2581
	11th to 20th	Night	54% 2 10% 21% 12% 1	3044
	21st to end	Night	68% 3 9% 13% 7%	4532

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	23% 23% 36% 13% 4 1	270
	11th to 20th	Day	30% 27% 31% 11% 1	270
	21st to end	Day	30% 27% 31% 10% 2	297
February	1st to 10th	Day	30% 27% 30% 10% 2	270
	11th to 20th	Day	32% 29% 30% 7% 1 1	270
	21st to end	Day	36% 16% 40% 7% 2	225
March	1st to 10th	Day	26% 29% 33% 9% 2	276
	11th to 20th	Day	27% 23% 30% 13% 5%	460
	21st to end	Day	31% 21% 29% 14% 5%	506
April	1st to 10th	Day	23% 21% 29% 17% 8% 1	460
	11th to 20th	Day	26% 18% 28% 19% 7% 3	452
	21st to end	Day	24% 16% 38% 13% 8% 1	460
May	1st to 10th	Day	25% 13% 34% 16% 7% 4	463
	11th to 20th	Day	21% 10% 29% 24% 11% 5%	487
	21st to end	Day	14% 10% 27% 25% 16% 8%	529
June	1st to 10th	Day	14% 10% 23% 30% 16% 7%	490
	11th to 20th	Day	10% 8% 25% 32% 18% 7%	640
	21st to end	Day	11% 7% 29% 28% 17% 7%	680
July	1st to 10th	Day	15% 4 19% 26% 21% 15%	671
	11th to 20th	Day	10% 5% 22% 31% 22% 11%	550
	21st to end	Day	13% 3 18% 33% 20% 12%	532
August	1st to 10th	Day	12% 4 17% 31% 23% 14%	486
	11th to 20th	Day	11% 4 20% 36% 20% 9%	479
	21st to end	Day	9% 3 16% 34% 25% 13%	539
September	1st to 10th	Day	13% 4 16% 32% 25% 9%	490
	11th to 20th	Day	10% 4 17% 31% 24% 14%	490
	21st to end	Day	21% 7% 22% 22% 21% 7%	490
October	1st to 10th	Day	11% 8% 25% 30% 19% 6%	490
	11th to 20th	Day	18% 15% 31% 20% 12% 4	490
	21st to end	Day	21% 13% 38% 22% 5% 1	396
November	1st to 10th	Day	16% 15% 35% 25% 5% 4	300
	11th to 20th	Day	23% 23% 29% 20% 5% 1	300
	21st to end	Day	28% 17% 34% 17% 4	300
December	1st to 10th	Day	25% 22% 36% 12% 4	294
	11th to 20th	Day	23% 21% 36% 15% 6%	270
	21st to end	Day	29% 20% 35% 11% 4	297
January	1st to 10th	Night	23% 23% 31% 19% 5%	882
	11th to 20th	Night	31% 21% 30% 16% 3	760
	21st to end	Night	26% 19% 32% 20% 2	836
February	1st to 10th	Night	29% 16% 32% 22% 2	760
	11th to 20th	Night	26% 21% 32% 20% 1	743
	21st to end	Night	31% 16% 35% 17% 1	628
March	1st to 10th	Night	26% 18% 29% 23% 4	760
	11th to 20th	Night	25% 17% 31% 20% 6% 1	760
	21st to end	Night	25% 13% 32% 24% 6%	836
April	1st to 10th	Night	17% 15% 35% 27% 6%	618
	11th to 20th	Night	18% 14% 32% 25% 10% 1	563
	21st to end	Night	20% 10% 36% 27% 7% 1	570
May	1st to 10th	Night	21% 11% 30% 23% 14% 1	570
	11th to 20th	Night	19% 7% 21% 33% 18% 2	561
	21st to end	Night	11% 3 23% 34% 26% 4	617
June	1st to 10th	Night	11% 3 20% 38% 24% 3	570
	11th to 20th	Night	9% 4 18% 41% 25% 3	570
	21st to end	Night	7% 4 24% 37% 25% 3	570
July	1st to 10th	Night	13% 2 14% 31% 30% 10%	555
	11th to 20th	Night	7% 2 14% 38% 35% 4	552
	21st to end	Night	11% 2 11% 40% 32% 4	624
August	1st to 10th	Night	10% 2 8% 37% 38% 5%	567
	11th to 20th	Night	7% 3 10% 40% 34% 5%	564
	21st to end	Night	7% 1 13% 32% 40% 7%	627
September	1st to 10th	Night	14% 4 12% 36% 30% 5%	664
	11th to 20th	Night	9% 4 15% 32% 34% 6%	760
	21st to end	Night	16% 7% 19% 31% 26% 2	760
October	1st to 10th	Night	11% 6% 21% 34% 24% 4	760
	11th to 20th	Night	18% 10% 25% 31% 14% 2	760
	21st to end	Night	21% 12% 29% 25% 11% 1	836
November	1st to 10th	Night	17% 12% 27% 27% 16% 2	780
	11th to 20th	Night	21% 16% 29% 24% 9% 1	800
	21st to end	Night	26% 14% 25% 27% 8% 1	800
December	1st to 10th	Night	29% 15% 30% 21% 5%	795
	11th to 20th	Night	26% 15% 29% 23% 6% 1	760
	21st to end	Night	31% 16% 29% 20% 4	836

Page generated at 2024-12-06 03:54:48. Version ac07

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