La Vergne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the La Vergne clear sky chart from 2005-11-06 to 2025-07-21.

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	13% 7% 3 7% 5% 4 5% 4 6% 7% 39%	120425
	Night	13% 7% 3 7% 4 4 4 3 5% 7% 42%	118709
Transparency	Day	42% 6% 10% 22% 17% 3	124159
	Night	41% 5% 10% 22% 19% 4	123103
Seeing	Day	16% 9% 21% 24% 20% 10%	16045
	Night	17% 8% 23% 30% 19% 3	25652

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	14% 11% 7% 13% 5% 5% 4 3 5% 5% 29%	3617
	11th to 20th	Day	16% 8% 4 12% 5% 4 4 2 3 4 37%	3952
	21st to end	Day	19% 10% 5% 5% 3 3 4 3 5% 7% 36%	4877
February	1st to 10th	Day	18% 11% 3 8% 5% 4 4 3 4 5% 34%	2000
	11th to 20th	Day	20% 12% 4 8% 4 5% 3 3 4 5% 32%	1948
	21st to end	Day	20% 10% 3 6% 4 4 3 3 4 6% 38%	1650
March	1st to 10th	Day	15% 11% 4 9% 5% 4 4 3 4 6% 35%	4480
	11th to 20th	Day	12% 7% 3 7% 4 4 4 3 4 6% 47%	4787
	21st to end	Day	11% 7% 3 7% 5% 4 4 4 5% 7% 43%	5732
April	1st to 10th	Day	12% 6% 2 5% 4 4 5% 4 5% 7% 45%	2400
	11th to 20th	Day	12% 7% 3 7% 4 3 5% 3 5% 6% 45%	2374
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 5% 8% 40%	2450
May	1st to 10th	Day	18% 8% 3 7% 5% 5% 5% 5% 7% 9% 28%	5862
	11th to 20th	Day	15% 8% 4 9% 6% 5% 5% 4 6% 8% 31%	5861
	21st to end	Day	14% 8% 3 8% 5% 4 4 4 5% 7% 39%	6433
June	1st to 10th	Day	9% 6% 2 7% 5% 4 5% 5% 7% 9% 42%	2600
	11th to 20th	Day	5% 4 1 6% 4 5% 6% 5% 9% 10% 45%	2758
	21st to end	Day	5% 4 2 5% 7% 5% 6% 6% 9% 12% 40%	2800
July	1st to 10th	Day	6% 4 2 7% 7% 6% 7% 6% 8% 9% 38%	4580
	11th to 20th	Day	9% 5% 2 6% 6% 5% 6% 5% 7% 11% 37%	4415
	21st to end	Day	16% 9% 4 9% 6% 6% 7% 5% 7% 8% 24%	4466
August	1st to 10th	Day	4 3 1 5% 4 5% 5% 5% 7% 10% 51%	3923
	11th to 20th	Day	5% 4 2 6% 6% 6% 6% 5% 9% 11% 40%	3729
	21st to end	Day	6% 3 1 5% 4 4 5% 4 6% 8% 53%	4180
September	1st to 10th	Day	12% 6% 2 7% 5% 5% 4 4 7% 8% 41%	2242
	11th to 20th	Day	13% 6% 2 5% 5% 4 6% 3 5% 7% 44%	2090
	21st to end	Day	12% 5% 2 5% 4 4 4 4 5% 7% 49%	2090
October	1st to 10th	Day	10% 5% 1 5% 3 3 3 3 5% 7% 55%	2090
	11th to 20th	Day	12% 5% 2 6% 3 3 3 2 3 7% 53%	2066
	21st to end	Day	15% 7% 2 6% 4 3 4 3 4 5% 47%	1886
November	1st to 10th	Day	12% 5% 2 5% 3 2 3 3 4 6% 55%	1762
	11th to 20th	Day	14% 7% 2 6% 3 2 4 3 7% 6% 46%	1800
	21st to end	Day	14% 8% 2 5% 5% 4 4 3 5% 6% 44%	1800
December	1st to 10th	Day	15% 7% 2 7% 4 4 4 3 5% 5% 43%	2930
	11th to 20th	Day	18% 12% 4 9% 4 5% 4 3 4 5% 32%	3373
	21st to end	Day	17% 10% 5% 9% 5% 4 5% 4 6% 7% 27%	4422
January	1st to 10th	Night	15% 10% 4 11% 5% 4 4 4 5% 6% 33%	6348
	11th to 20th	Night	18% 10% 3 8% 5% 3 3 3 5% 4 40%	5975
	21st to end	Night	17% 11% 3 6% 4 3 3 3 4 6% 39%	6076
February	1st to 10th	Night	20% 10% 3 8% 5% 4 3 4 5% 5% 33%	2400
	11th to 20th	Night	23% 10% 3 8% 4 3 3 3 4 4 35%	2338
	21st to end	Night	22% 8% 3 7% 4 4 4 4 5% 5% 35%	1980
March	1st to 10th	Night	19% 10% 3 7% 4 5% 4 3 5% 6% 35%	5373
	11th to 20th	Night	11% 5% 2 5% 3 5% 4 4 5% 7% 50%	5171
	21st to end	Night	13% 7% 3 7% 5% 4 4 4 5% 7% 42%	5238
April	1st to 10th	Night	12% 5% 2 6% 4 4 5% 4 6% 7% 46%	2000
	11th to 20th	Night	15% 5% 2 4 3 3 4 3 5% 6% 48%	1975
	21st to end	Night	12% 7% 3 5% 4 4 5% 3 6% 7% 44%	1950
May	1st to 10th	Night	13% 9% 3 9% 5% 5% 5% 4 7% 7% 32%	4033
	11th to 20th	Night	13% 9% 4 9% 6% 5% 5% 4 6% 8% 31%	4032
	21st to end	Night	12% 6% 3 7% 6% 5% 5% 4 6% 9% 38%	4421
June	1st to 10th	Night	7% 5% 3 8% 5% 5% 4 4 6% 9% 45%	1800
	11th to 20th	Night	4 3 1 5% 4 4 4 5% 7% 12% 51%	1634
	21st to end	Night	3 4 1 5% 5% 4 6% 4 6% 12% 48%	1600
July	1st to 10th	Night	6% 4 2 6% 5% 5% 6% 5% 9% 12% 41%	2610
	11th to 20th	Night	6% 5% 2 6% 4 4 4 4 6% 12% 45%	2765
	21st to end	Night	10% 10% 4 11% 7% 7% 6% 5% 5% 8% 27%	3087
August	1st to 10th	Night	4 3 1 4 3 3 3 3 5% 9% 60%	3002
	11th to 20th	Night	5% 3 2 5% 4 5% 5% 5% 7% 11% 49%	3100
	21st to end	Night	5% 3 1 4 4 4 4 4 6% 7% 58%	3476
September	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 6% 7% 48%	1919
	11th to 20th	Night	11% 6% 3 5% 4 4 4 3 5% 7% 46%	2090
	21st to end	Night	11% 5% 2 5% 4 3 4 4 4 7% 52%	2090
October	1st to 10th	Night	10% 3 1 4 3 3 3 3 4 6% 60%	2090
	11th to 20th	Night	14% 5% 2 6% 3 3 4 3 4 6% 51%	2109
	21st to end	Night	15% 6% 2 5% 3 3 3 3 5% 6% 49%	2711
November	1st to 10th	Night	12% 5% 2 5% 4 4 3 2 5% 6% 52%	2536
	11th to 20th	Night	13% 7% 2 4 4 3 3 3 6% 7% 48%	2600
	21st to end	Night	16% 7% 2 5% 4 4 3 3 5% 6% 45%	2600
December	1st to 10th	Night	18% 11% 3 8% 4 3 3 3 4 4 40%	4250
	11th to 20th	Night	21% 10% 3 7% 3 3 3 2 4 4 40%	4822
	21st to end	Night	17% 11% 4 8% 6% 5% 5% 4 5% 6% 29%	6508

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	56% 3 11% 17% 11% 1	3618
	11th to 20th	Day	51% 3 6% 19% 21% 1	3952
	21st to end	Day	48% 3 8% 22% 15% 5%	4877
February	1st to 10th	Day	54% 4 7% 19% 14% 2	2000
	11th to 20th	Day	55% 4 7% 17% 13% 3	1958
	21st to end	Day	48% 4 9% 16% 17% 6%	1650
March	1st to 10th	Day	52% 4 5% 14% 17% 9%	4480
	11th to 20th	Day	40% 4 7% 21% 20% 8%	4787
	21st to end	Day	42% 4 9% 28% 16% 1	5734
April	1st to 10th	Day	38% 5% 11% 23% 19% 4	2400
	11th to 20th	Day	39% 5% 7% 22% 21% 6%	2374
	21st to end	Day	43% 5% 9% 26% 15% 2	2450
May	1st to 10th	Day	49% 9% 13% 18% 10% 1	5897
	11th to 20th	Day	50% 8% 13% 19% 10%	5865
	21st to end	Day	45% 6% 9% 21% 17% 2	6447
June	1st to 10th	Day	38% 8% 12% 23% 17% 2	2600
	11th to 20th	Day	31% 9% 16% 23% 18% 3	2758
	21st to end	Day	32% 10% 17% 20% 17% 4	2800
July	1st to 10th	Day	37% 11% 17% 25% 9% 2	4511
	11th to 20th	Day	38% 9% 17% 27% 8% 2	4341
	21st to end	Day	55% 10% 12% 16% 7% 1	4324
August	1st to 10th	Day	26% 8% 14% 33% 18% 1	3910
	11th to 20th	Day	34% 7% 15% 26% 16% 2	3765
	21st to end	Day	28% 7% 10% 30% 23% 2	4179
September	1st to 10th	Day	39% 8% 12% 19% 18% 5%	2242
	11th to 20th	Day	40% 6% 10% 22% 18% 3	2090
	21st to end	Day	35% 5% 11% 22% 21% 6%	2090
October	1st to 10th	Day	24% 3 6% 16% 41% 10%	3480
	11th to 20th	Day	24% 2 6% 23% 30% 14%	3410
	21st to end	Day	31% 3 7% 23% 28% 8%	3086
November	1st to 10th	Day	32% 4 8% 23% 28% 5%	1762
	11th to 20th	Day	37% 4 7% 23% 24% 5%	1800
	21st to end	Day	41% 3 7% 25% 19% 4	1800
December	1st to 10th	Day	43% 4 6% 26% 20% 1	2930
	11th to 20th	Day	56% 4 8% 18% 12% 3	3370
	21st to end	Day	54% 4 12% 22% 7% 2	4422
January	1st to 10th	Night	50% 4 11% 20% 14% 1	6348
	11th to 20th	Night	48% 3 8% 17% 21% 4	5975
	21st to end	Night	49% 2 6% 21% 17% 5%	6076
February	1st to 10th	Night	52% 5% 9% 18% 15% 1	2400
	11th to 20th	Night	54% 4 6% 18% 15% 4	2339
	21st to end	Night	51% 4 7% 15% 17% 5%	1980
March	1st to 10th	Night	50% 4 7% 14% 19% 6%	5373
	11th to 20th	Night	34% 4 8% 20% 20% 13%	5171
	21st to end	Night	43% 4 8% 26% 16% 2	5238
April	1st to 10th	Night	36% 5% 11% 24% 21% 3	2000
	11th to 20th	Night	36% 4 8% 21% 23% 8%	1975
	21st to end	Night	38% 6% 10% 25% 18% 2	1950
May	1st to 10th	Night	48% 7% 13% 21% 10% 1	4060
	11th to 20th	Night	50% 9% 13% 16% 12%	4033
	21st to end	Night	41% 9% 12% 22% 14% 1	4429
June	1st to 10th	Night	35% 7% 12% 26% 17% 3	1800
	11th to 20th	Night	24% 7% 17% 31% 18% 3	1634
	21st to end	Night	28% 9% 16% 28% 15% 4	1600
July	1st to 10th	Night	32% 9% 22% 26% 9% 2	2570
	11th to 20th	Night	32% 8% 18% 31% 8% 3	2717
	21st to end	Night	52% 10% 12% 16% 9% 1	2988
August	1st to 10th	Night	22% 5% 12% 38% 22% 1	2991
	11th to 20th	Night	26% 7% 20% 30% 15% 1	3130
	21st to end	Night	24% 7% 11% 32% 24% 2	3476
September	1st to 10th	Night	35% 6% 12% 23% 19% 5%	1919
	11th to 20th	Night	37% 6% 11% 18% 26% 2	2090
	21st to end	Night	31% 6% 11% 22% 23% 7%	2090
October	1st to 10th	Night	22% 3 8% 17% 37% 12%	3480
	11th to 20th	Night	22% 3 5% 22% 31% 17%	3492
	21st to end	Night	25% 2 7% 24% 30% 11%	4461
November	1st to 10th	Night	35% 3 7% 22% 25% 7%	2536
	11th to 20th	Night	35% 3 8% 20% 28% 7%	2600
	21st to end	Night	41% 3 8% 23% 20% 5%	2600
December	1st to 10th	Night	48% 3 6% 16% 24% 2	4250
	11th to 20th	Night	48% 2 6% 22% 19% 2	4824
	21st to end	Night	55% 4 10% 21% 10% 1	6508

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% 17% 37% 15% 6% 1	300
	11th to 20th	Day	29% 20% 31% 14% 5% 1	300
	21st to end	Day	22% 15% 41% 18% 4	330
February	1st to 10th	Day	26% 13% 37% 18% 5%	300
	11th to 20th	Day	34% 20% 30% 12% 4 1	300
	21st to end	Day	31% 17% 33% 14% 4	249
March	1st to 10th	Day	22% 15% 39% 17% 7%	300
	11th to 20th	Day	21% 18% 33% 20% 7% 1	411
	21st to end	Day	23% 14% 35% 19% 8% 1	550
April	1st to 10th	Day	20% 17% 26% 25% 10% 2	500
	11th to 20th	Day	17% 15% 28% 28% 11% 2	492
	21st to end	Day	19% 12% 27% 26% 13% 4	500
May	1st to 10th	Day	19% 10% 25% 26% 14% 5%	503
	11th to 20th	Day	17% 7% 22% 25% 20% 9%	527
	21st to end	Day	12% 6% 19% 26% 23% 15%	573
June	1st to 10th	Day	11% 5% 16% 24% 25% 19%	530
	11th to 20th	Day	6% 3 13% 27% 32% 18%	688
	21st to end	Day	7% 3 15% 32% 25% 19%	730
July	1st to 10th	Day	8% 4 9% 27% 32% 21%	721
	11th to 20th	Day	9% 3 8% 23% 33% 23%	619
	21st to end	Day	10% 3 9% 22% 31% 25%	532
August	1st to 10th	Day	9% 2 8% 27% 34% 21%	486
	11th to 20th	Day	11% 3 9% 31% 33% 13%	479
	21st to end	Day	11% 2 7% 18% 37% 25%	539
September	1st to 10th	Day	13% 4 9% 23% 33% 18%	490
	11th to 20th	Day	15% 3 8% 21% 33% 20%	490
	21st to end	Day	16% 5% 14% 27% 27% 11%	490
October	1st to 10th	Day	12% 4 16% 27% 28% 12%	490
	11th to 20th	Day	12% 11% 27% 29% 17% 5%	466
	21st to end	Day	23% 10% 22% 29% 14% 2	330
November	1st to 10th	Day	17% 8% 28% 31% 13% 4	300
	11th to 20th	Day	17% 13% 34% 25% 11%	300
	21st to end	Day	21% 11% 33% 19% 13% 3	300
December	1st to 10th	Day	25% 19% 27% 23% 5% 1	300
	11th to 20th	Day	23% 18% 28% 20% 11% 1	300
	21st to end	Day	25% 18% 30% 22% 5%	330
January	1st to 10th	Night	22% 16% 30% 26% 5%	1000
	11th to 20th	Night	26% 16% 31% 22% 4	836
	21st to end	Night	21% 11% 38% 27% 3	880
February	1st to 10th	Night	25% 12% 32% 27% 4	800
	11th to 20th	Night	30% 13% 33% 22% 3	783
	21st to end	Night	28% 14% 33% 23% 2	660
March	1st to 10th	Night	22% 13% 32% 28% 6%	800
	11th to 20th	Night	21% 10% 34% 27% 7% 1	800
	21st to end	Night	19% 12% 32% 28% 8%	780
April	1st to 10th	Night	15% 12% 33% 33% 8%	600
	11th to 20th	Night	17% 9% 34% 29% 10% 1	593
	21st to end	Night	17% 9% 28% 35% 10% 1	600
May	1st to 10th	Night	14% 5% 28% 35% 17% 1	600
	11th to 20th	Night	12% 4 22% 37% 21% 4	591
	21st to end	Night	8% 2 16% 40% 29% 5%	650
June	1st to 10th	Night	9% 3 14% 37% 32% 5%	600
	11th to 20th	Night	6% 2 10% 36% 42% 5%	600
	21st to end	Night	6% 1 9% 37% 39% 9%	600
July	1st to 10th	Night	10% 2 6% 30% 43% 10%	585
	11th to 20th	Night	7% 2 6% 28% 46% 11%	582
	21st to end	Night	8% 2 7% 28% 46% 9%	624
August	1st to 10th	Night	8% 2 4 30% 48% 8%	567
	11th to 20th	Night	7% 2 9% 39% 38% 5%	564
	21st to end	Night	10% 1 4 30% 44% 10%	627
September	1st to 10th	Night	12% 1 10% 29% 42% 6%	589
	11th to 20th	Night	13% 4 12% 28% 38% 6%	760
	21st to end	Night	13% 2 15% 31% 36% 4	760
October	1st to 10th	Night	11% 4 16% 31% 32% 6%	760
	11th to 20th	Night	18% 6% 21% 34% 19% 2	760
	21st to end	Night	17% 7% 26% 31% 18% 2	836
November	1st to 10th	Night	15% 6% 21% 37% 18% 2	780
	11th to 20th	Night	16% 9% 31% 32% 13% 1	800
	21st to end	Night	20% 10% 27% 32% 11% 1	800
December	1st to 10th	Night	28% 12% 28% 27% 6%	800
	11th to 20th	Night	22% 8% 31% 31% 7% 1	800
	21st to end	Night	26% 12% 30% 26% 5%	885

Page generated at 2025-07-18 00:10:01. Version ac07

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