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 2024-11-04.

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% 8% 40%	101282
	Night	13% 7% 3 6% 4 4 4 4 5% 7% 43%	97680
Transparency	Day	41% 6% 10% 22% 17% 3	105016
	Night	39% 5% 10% 22% 19% 4	102074
Seeing	Day	16% 9% 21% 24% 20% 11%	15107
	Night	17% 8% 23% 30% 20% 3	24723

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	13% 12% 6% 11% 5% 5% 5% 4 5% 6% 28%	2527
	11th to 20th	Day	20% 9% 3 12% 6% 6% 5% 2 3 4 30%	2758
	21st to end	Day	23% 13% 7% 6% 3 3 3 3 4 5% 30%	3409
February	1st to 10th	Day	19% 11% 3 8% 5% 4 4 3 4 5% 34%	1900
	11th to 20th	Day	20% 11% 4 8% 4 5% 3 3 4 6% 33%	1848
	21st to end	Day	21% 10% 3 6% 4 4 3 3 4 6% 36%	1570
March	1st to 10th	Day	19% 12% 4 8% 5% 4 4 3 5% 6% 31%	3120
	11th to 20th	Day	13% 6% 3 6% 4 4 4 3 4 6% 47%	3343
	21st to end	Day	13% 7% 3 7% 5% 4 4 4 6% 7% 41%	4000
April	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 5% 6% 46%	2280
	11th to 20th	Day	12% 7% 3 7% 4 3 5% 3 5% 6% 45%	2254
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 5% 8% 41%	2327
May	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 4 7% 8% 35%	4082
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 5% 8% 37%	4081
	21st to end	Day	10% 7% 3 7% 5% 5% 5% 4 6% 8% 41%	4476
June	1st to 10th	Day	9% 6% 2 7% 5% 4 5% 5% 7% 9% 42%	2470
	11th to 20th	Day	5% 4 1 5% 4 5% 6% 5% 9% 10% 46%	2620
	21st to end	Day	5% 4 2 5% 7% 5% 6% 6% 9% 12% 40%	2660
July	1st to 10th	Day	6% 4 2 7% 7% 6% 7% 6% 8% 9% 38%	4440
	11th to 20th	Day	9% 5% 2 6% 6% 5% 6% 5% 7% 11% 37%	4280
	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% 4 2 4 3 2 3 3 4 6% 58%	1699
	11th to 20th	Day	14% 6% 2 6% 3 2 4 3 7% 6% 47%	1710
	21st to end	Day	15% 8% 2 5% 4 3 4 3 5% 6% 44%	1710
December	1st to 10th	Day	22% 9% 3 7% 4 3 4 4 5% 5% 35%	1710
	11th to 20th	Day	15% 10% 3 7% 5% 5% 4 4 4 7% 36%	2153
	21st to end	Day	17% 11% 4 9% 6% 4 4 4 6% 7% 28%	3093
January	1st to 10th	Night	18% 10% 3 8% 4 4 4 3 5% 6% 34%	4428
	11th to 20th	Night	19% 11% 3 8% 5% 4 4 3 4 4 35%	4181
	21st to end	Night	20% 13% 4 6% 4 3 3 3 4 6% 33%	4244
February	1st to 10th	Night	20% 10% 3 8% 5% 4 3 3 5% 5% 33%	2280
	11th to 20th	Night	22% 10% 3 7% 4 3 3 3 4 4 36%	2218
	21st to end	Night	24% 8% 3 7% 5% 4 4 4 5% 5% 32%	1884
March	1st to 10th	Night	23% 9% 2 7% 4 5% 4 3 4 5% 32%	3733
	11th to 20th	Night	13% 6% 2 5% 3 5% 3 3 4 6% 49%	3615
	21st to end	Night	13% 7% 3 7% 5% 4 4 4 5% 6% 41%	3658
April	1st to 10th	Night	11% 5% 2 6% 4 4 5% 4 6% 7% 47%	1900
	11th to 20th	Night	16% 6% 2 4 3 3 3 3 5% 6% 48%	1875
	21st to end	Night	13% 7% 3 5% 4 3 5% 3 6% 7% 44%	1853
May	1st to 10th	Night	12% 7% 2 7% 5% 4 4 4 6% 7% 40%	2813
	11th to 20th	Night	12% 7% 3 7% 5% 4 4 3 6% 8% 41%	2812
	21st to end	Night	6% 4 2 7% 6% 5% 5% 5% 6% 10% 43%	3079
June	1st to 10th	Night	7% 5% 2 8% 5% 5% 4 4 6% 9% 45%	1710
	11th to 20th	Night	4 3 1 4 4 4 4 5% 7% 12% 53%	1553
	21st to end	Night	3 4 2 5% 5% 4 6% 4 6% 12% 47%	1520
July	1st to 10th	Night	6% 4 2 6% 5% 5% 6% 5% 9% 12% 41%	2530
	11th to 20th	Night	6% 5% 2 6% 4 4 4 4 6% 11% 45%	2680
	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	11% 4 2 5% 4 4 3 2 5% 6% 53%	2452
	11th to 20th	Night	12% 7% 2 4 4 3 3 3 6% 7% 49%	2470
	21st to end	Night	16% 7% 2 5% 4 4 3 3 5% 6% 45%	2470
December	1st to 10th	Night	21% 11% 3 6% 4 4 4 3 5% 6% 35%	2470
	11th to 20th	Night	15% 9% 4 7% 3 4 3 3 4 5% 44%	3042
	21st to end	Night	16% 11% 4 9% 6% 5% 5% 4 5% 7% 29%	4536

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	55% 4 9% 19% 12% 2	2528
	11th to 20th	Day	58% 3 8% 15% 15% 1	2758
	21st to end	Day	56% 3 8% 21% 11% 1	3409
February	1st to 10th	Day	53% 4 7% 19% 15% 2	1900
	11th to 20th	Day	54% 4 7% 18% 14% 3	1858
	21st to end	Day	50% 4 9% 15% 16% 6%	1570
March	1st to 10th	Day	55% 5% 6% 14% 13% 8%	3120
	11th to 20th	Day	39% 5% 9% 24% 17% 6%	3343
	21st to end	Day	43% 5% 9% 26% 16% 1	4000
April	1st to 10th	Day	38% 5% 11% 23% 20% 4	2280
	11th to 20th	Day	39% 5% 7% 21% 22% 6%	2254
	21st to end	Day	42% 5% 9% 26% 16% 2	2327
May	1st to 10th	Day	44% 8% 11% 22% 14% 1	4120
	11th to 20th	Day	44% 8% 11% 24% 12%	4085
	21st to end	Day	39% 7% 11% 22% 20% 1	4489
June	1st to 10th	Day	38% 7% 12% 23% 17% 2	2470
	11th to 20th	Day	30% 9% 16% 24% 19% 3	2620
	21st to end	Day	33% 10% 17% 20% 16% 4	2660
July	1st to 10th	Day	37% 11% 17% 25% 8% 2	4371
	11th to 20th	Day	38% 9% 16% 27% 8% 2	4206
	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	30% 3 8% 24% 29% 6%	1699
	11th to 20th	Day	36% 4 7% 23% 24% 5%	1710
	21st to end	Day	41% 3 7% 25% 20% 4	1710
December	1st to 10th	Day	51% 5% 6% 21% 15% 2	1710
	11th to 20th	Day	48% 5% 10% 19% 16% 2	2150
	21st to end	Day	53% 4 13% 19% 9% 2	3093
January	1st to 10th	Night	48% 4 9% 22% 16% 1	4428
	11th to 20th	Night	52% 4 9% 15% 16% 4	4181
	21st to end	Night	53% 3 8% 21% 13% 2	4244
February	1st to 10th	Night	52% 4 9% 18% 16% 1	2280
	11th to 20th	Night	53% 4 6% 18% 15% 4	2219
	21st to end	Night	53% 4 8% 14% 16% 5%	1884
March	1st to 10th	Night	54% 5% 9% 11% 16% 6%	3733
	11th to 20th	Night	37% 5% 8% 23% 16% 11%	3615
	21st to end	Night	43% 5% 9% 23% 18% 1	3658
April	1st to 10th	Night	36% 5% 11% 24% 22% 3	1900
	11th to 20th	Night	37% 4 8% 20% 23% 9%	1875
	21st to end	Night	38% 6% 9% 26% 19% 2	1853
May	1st to 10th	Night	41% 8% 12% 25% 13% 1	2840
	11th to 20th	Night	41% 9% 14% 19% 16% 1	2813
	21st to end	Night	33% 11% 13% 24% 18% 1	3087
June	1st to 10th	Night	36% 7% 12% 25% 16% 3	1710
	11th to 20th	Night	23% 7% 17% 31% 18% 3	1553
	21st to end	Night	28% 9% 16% 28% 14% 4	1520
July	1st to 10th	Night	32% 9% 22% 26% 9% 2	2490
	11th to 20th	Night	33% 7% 17% 31% 9% 3	2632
	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	34% 3 7% 23% 26% 7%	2452
	11th to 20th	Night	34% 3 8% 21% 28% 7%	2470
	21st to end	Night	41% 4 8% 22% 21% 5%	2470
December	1st to 10th	Night	51% 5% 9% 18% 16% 2	2470
	11th to 20th	Night	42% 3 8% 21% 22% 3	3044
	21st to end	Night	55% 4 10% 17% 12% 2	4536

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% 39% 13% 6% 1	270
	11th to 20th	Day	31% 21% 28% 13% 6% 1	270
	21st to end	Day	22% 16% 41% 17% 4	297
February	1st to 10th	Day	26% 14% 36% 17% 6%	270
	11th to 20th	Day	34% 19% 30% 11% 4 1	270
	21st to end	Day	34% 18% 32% 12% 3	225
March	1st to 10th	Day	23% 16% 38% 17% 6%	270
	11th to 20th	Day	21% 18% 32% 20% 7% 1	375
	21st to end	Day	24% 14% 34% 19% 9% 1	506
April	1st to 10th	Day	19% 17% 25% 26% 10% 2	460
	11th to 20th	Day	18% 14% 27% 27% 12% 2	452
	21st to end	Day	18% 12% 28% 25% 13% 4	460
May	1st to 10th	Day	18% 11% 25% 26% 15% 5%	463
	11th to 20th	Day	17% 6% 22% 25% 21% 10%	487
	21st to end	Day	10% 5% 18% 26% 24% 16%	529
June	1st to 10th	Day	11% 5% 16% 23% 24% 20%	490
	11th to 20th	Day	6% 3 13% 27% 33% 18%	640
	21st to end	Day	7% 4 16% 33% 24% 16%	680
July	1st to 10th	Day	8% 4 9% 27% 30% 21%	671
	11th to 20th	Day	9% 3 9% 24% 32% 23%	574
	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	15% 8% 27% 32% 14% 4	279
	11th to 20th	Day	15% 14% 35% 26% 10%	270
	21st to end	Day	21% 11% 31% 20% 13% 4	270
December	1st to 10th	Day	26% 20% 25% 22% 6% 1	270
	11th to 20th	Day	21% 18% 29% 19% 12% 1	270
	21st to end	Day	25% 20% 31% 21% 4	297
January	1st to 10th	Night	22% 17% 30% 26% 5%	950
	11th to 20th	Night	27% 16% 31% 22% 4	795
	21st to end	Night	21% 12% 38% 26% 3	836
February	1st to 10th	Night	25% 12% 32% 27% 4	760
	11th to 20th	Night	29% 13% 33% 22% 3	743
	21st to end	Night	30% 15% 32% 21% 1	628
March	1st to 10th	Night	22% 12% 31% 28% 6%	760
	11th to 20th	Night	21% 10% 34% 27% 8% 1	760
	21st to end	Night	20% 12% 31% 29% 9%	741
April	1st to 10th	Night	14% 12% 33% 33% 8%	570
	11th to 20th	Night	18% 9% 33% 28% 10% 1	563
	21st to end	Night	16% 9% 29% 34% 10% 1	570
May	1st to 10th	Night	13% 5% 29% 35% 18% 1	570
	11th to 20th	Night	12% 4 22% 36% 21% 4	561
	21st to end	Night	7% 2 15% 40% 30% 5%	617
June	1st to 10th	Night	9% 4 14% 35% 33% 5%	570
	11th to 20th	Night	5% 1 10% 36% 41% 5%	570
	21st to end	Night	6% 1 9% 39% 38% 8%	570
July	1st to 10th	Night	10% 2 6% 31% 41% 10%	555
	11th to 20th	Night	8% 2 6% 29% 44% 11%	552
	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	14% 6% 21% 38% 19% 2	755
	11th to 20th	Night	15% 9% 31% 31% 13% 1	760
	21st to end	Night	19% 10% 27% 32% 11% 1	760
December	1st to 10th	Night	28% 11% 28% 26% 6%	760
	11th to 20th	Night	22% 8% 31% 31% 7% 1	760
	21st to end	Night	26% 13% 30% 26% 5%	840

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