Villard
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Villard clear sky chart from 2005-11-06 to 2026-02-16.

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	11% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	131052
	Night	10% 9% 4 9% 6% 5% 5% 4 6% 7% 37%	130089
Transparency	Day	44% 4 13% 26% 11% 1	134604
	Night	46% 4 13% 24% 12% 1	134617
Seeing	Day	15% 10% 31% 27% 13% 3	17771
	Night	14% 9% 33% 32% 10% 1	27818

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	7% 14% 4 14% 13% 9% 8% 4 6% 6% 15%	4124
	11th to 20th	Day	5% 8% 5% 13% 7% 8% 11% 7% 9% 8% 18%	4589
	21st to end	Day	3 9% 7% 13% 7% 6% 6% 6% 7% 7% 28%	5812
February	1st to 10th	Day	8% 12% 5% 11% 6% 6% 6% 4 6% 9% 27%	1890
	11th to 20th	Day	6% 11% 4 9% 9% 7% 5% 5% 7% 8% 31%	1799
	21st to end	Day	8% 12% 4 11% 9% 7% 5% 4 7% 8% 26%	1540
March	1st to 10th	Day	11% 9% 3 8% 5% 5% 3 3 5% 7% 41%	4851
	11th to 20th	Day	10% 9% 3 8% 5% 4 5% 4 5% 9% 38%	4980
	21st to end	Day	19% 12% 5% 11% 7% 4 4 3 5% 7% 23%	5462
April	1st to 10th	Day	16% 10% 3 6% 5% 4 4 4 5% 7% 36%	2345
	11th to 20th	Day	17% 13% 4 8% 4 4 3 3 6% 6% 32%	2527
	21st to end	Day	22% 11% 3 6% 4 4 4 4 4 6% 33%	2600
May	1st to 10th	Day	12% 6% 2 6% 4 3 4 3 4 6% 50%	5904
	11th to 20th	Day	17% 9% 2 5% 3 3 4 3 4 6% 42%	6319
	21st to end	Day	15% 7% 3 6% 5% 4 5% 4 7% 8% 37%	6935
June	1st to 10th	Day	11% 5% 2 7% 4 5% 4 4 6% 9% 43%	2954
	11th to 20th	Day	15% 7% 3 8% 5% 3 4 4 7% 7% 37%	3000
	21st to end	Day	10% 5% 2 5% 4 5% 5% 5% 7% 10% 42%	3000
July	1st to 10th	Day	7% 4 2 5% 4 5% 5% 5% 7% 10% 46%	6800
	11th to 20th	Day	8% 4 2 4 3 3 4 4 6% 9% 53%	6766
	21st to end	Day	7% 4 2 6% 4 4 5% 4 7% 10% 46%	6609
August	1st to 10th	Day	12% 5% 2 5% 3 4 5% 4 6% 9% 44%	4234
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 10% 41%	4171
	21st to end	Day	10% 6% 2 6% 4 4 4 3 5% 8% 48%	4642
September	1st to 10th	Day	10% 5% 1 5% 4 3 5% 3 6% 8% 51%	2400
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 5% 7% 45%	2244
	21st to end	Day	14% 6% 2 5% 3 3 4 3 5% 7% 49%	2185
October	1st to 10th	Day	16% 8% 2 5% 3 3 4 3 5% 8% 42%	2000
	11th to 20th	Day	15% 11% 3 6% 3 4 4 3 5% 5% 40%	2000
	21st to end	Day	17% 11% 4 8% 5% 4 4 3 4 5% 36%	2142
November	1st to 10th	Day	14% 13% 3 8% 4 4 4 4 6% 6% 34%	1712
	11th to 20th	Day	10% 13% 5% 13% 7% 6% 4 3 4 6% 29%	1680
	21st to end	Day	11% 11% 5% 12% 7% 5% 5% 3 5% 7% 29%	1680
December	1st to 10th	Day	6% 10% 5% 13% 12% 10% 8% 5% 5% 6% 19%	2690
	11th to 20th	Day	8% 15% 9% 11% 6% 5% 5% 4 5% 6% 26%	2891
	21st to end	Day	16% 17% 6% 20% 7% 4 3 2 3 5% 18%	3575
January	1st to 10th	Night	6% 9% 4 15% 11% 7% 8% 5% 6% 7% 23%	8799
	11th to 20th	Night	4 10% 5% 12% 8% 8% 11% 9% 7% 6% 21%	8384
	21st to end	Night	3 10% 8% 10% 5% 6% 6% 5% 7% 8% 32%	8402
February	1st to 10th	Night	6% 11% 5% 9% 8% 6% 5% 5% 7% 8% 30%	2730
	11th to 20th	Night	5% 9% 4 8% 6% 5% 6% 5% 7% 7% 38%	2599
	21st to end	Night	10% 10% 4 8% 5% 6% 5% 4 6% 7% 34%	2109
March	1st to 10th	Night	10% 6% 2 6% 4 4 4 4 6% 8% 46%	5007
	11th to 20th	Night	9% 8% 2 7% 5% 5% 5% 4 8% 9% 38%	4980
	21st to end	Night	20% 12% 4 10% 5% 5% 4 3 5% 5% 28%	5467
April	1st to 10th	Night	15% 9% 3 6% 4 4 4 3 5% 7% 40%	2055
	11th to 20th	Night	15% 11% 4 8% 4 4 4 3 5% 6% 36%	1820
	21st to end	Night	18% 10% 3 7% 4 3 5% 3 5% 5% 37%	1800
May	1st to 10th	Night	11% 6% 2 5% 3 3 3 2 4 6% 54%	4008
	11th to 20th	Night	13% 9% 2 6% 4 4 4 3 4 5% 47%	3596
	21st to end	Night	16% 9% 3 6% 5% 4 4 4 5% 7% 38%	3942
June	1st to 10th	Night	10% 5% 2 4 4 5% 3 4 5% 9% 49%	1442
	11th to 20th	Night	10% 5% 3 5% 4 4 4 5% 7% 9% 46%	1400
	21st to end	Night	9% 5% 2 4 4 3 4 3 7% 8% 52%	1400
July	1st to 10th	Night	8% 5% 2 4 4 4 5% 4 6% 10% 48%	3178
	11th to 20th	Night	6% 3 1 4 3 3 4 3 6% 8% 59%	3207
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 6% 8% 48%	4259
August	1st to 10th	Night	9% 7% 2 5% 3 4 4 3 6% 7% 50%	2926
	11th to 20th	Night	12% 5% 2 5% 4 3 3 3 5% 8% 50%	2888
	21st to end	Night	8% 5% 2 5% 3 3 4 4 5% 9% 52%	3266
September	1st to 10th	Night	8% 4 1 4 3 3 3 2 6% 8% 56%	2000
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 6% 52%	2154
	21st to end	Night	10% 6% 2 5% 3 3 3 2 4 6% 54%	2200
October	1st to 10th	Night	13% 7% 2 6% 4 3 4 3 5% 7% 47%	2395
	11th to 20th	Night	14% 9% 2 6% 5% 3 5% 3 5% 7% 43%	2400
	21st to end	Night	15% 11% 4 8% 3 3 4 3 5% 7% 36%	2695
November	1st to 10th	Night	11% 9% 3 7% 5% 4 5% 4 7% 7% 39%	2806
	11th to 20th	Night	11% 12% 4 12% 5% 4 4 3 5% 7% 33%	2940
	21st to end	Night	10% 10% 4 10% 7% 5% 4 3 6% 6% 36%	2940
December	1st to 10th	Night	5% 8% 4 11% 12% 8% 6% 4 7% 8% 26%	4720
	11th to 20th	Night	9% 12% 5% 15% 8% 7% 5% 4 6% 6% 23%	5530
	21st to end	Night	16% 17% 5% 17% 8% 5% 4 3 5% 5% 16%	7645

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	69% 3 10% 11% 6%	4125
	11th to 20th	Day	60% 3 10% 20% 7%	4589
	21st to end	Day	52% 5% 11% 20% 11%	5812
February	1st to 10th	Day	53% 4 12% 20% 10% 1	1890
	11th to 20th	Day	50% 4 13% 25% 6% 1	1808
	21st to end	Day	55% 4 12% 19% 10%	1540
March	1st to 10th	Day	43% 4 16% 25% 10% 2	4851
	11th to 20th	Day	43% 2 14% 29% 11%	4980
	21st to end	Day	62% 3 11% 18% 5%	5464
April	1st to 10th	Day	46% 5% 11% 24% 13% 1	2345
	11th to 20th	Day	52% 4 12% 18% 12% 1	2527
	21st to end	Day	52% 5% 11% 22% 9% 1	2600
May	1st to 10th	Day	35% 4 13% 29% 19%	5942
	11th to 20th	Day	43% 4 9% 23% 15% 7%	6323
	21st to end	Day	42% 5% 11% 31% 9% 1	6949
June	1st to 10th	Day	37% 5% 16% 30% 11% 1	2954
	11th to 20th	Day	44% 5% 15% 21% 14% 1	3000
	21st to end	Day	35% 6% 19% 27% 12% 1	3000
July	1st to 10th	Day	30% 7% 19% 32% 12%	6726
	11th to 20th	Day	28% 5% 17% 36% 14% 1	6685
	21st to end	Day	32% 6% 17% 32% 12% 1	6422
August	1st to 10th	Day	36% 5% 13% 32% 12% 2	4220
	11th to 20th	Day	39% 5% 14% 32% 9% 1	4210
	21st to end	Day	34% 5% 16% 32% 11% 1	4641
September	1st to 10th	Day	31% 5% 16% 36% 12% 1	2400
	11th to 20th	Day	37% 5% 18% 30% 9%	2244
	21st to end	Day	36% 3 12% 34% 13% 1	2185
October	1st to 10th	Day	32% 3 9% 33% 22% 1	3260
	11th to 20th	Day	39% 4 12% 22% 22% 2	3240
	21st to end	Day	48% 3 13% 26% 9%	3447
November	1st to 10th	Day	49% 5% 11% 22% 12% 2	1712
	11th to 20th	Day	58% 4 12% 18% 9% 1	1680
	21st to end	Day	55% 2 15% 19% 6% 2	1680
December	1st to 10th	Day	64% 5% 14% 12% 4	2690
	11th to 20th	Day	59% 2 14% 17% 7%	2888
	21st to end	Day	72% 2 8% 12% 6%	3575
January	1st to 10th	Night	60% 3 13% 16% 9%	8800
	11th to 20th	Night	61% 3 10% 16% 9% 1	8384
	21st to end	Night	48% 4 12% 25% 10%	8402
February	1st to 10th	Night	49% 4 13% 21% 11% 1	2730
	11th to 20th	Night	43% 5% 13% 24% 13% 1	2600
	21st to end	Night	47% 4 12% 21% 13% 2	2109
March	1st to 10th	Night	35% 3 15% 28% 16% 3	5007
	11th to 20th	Night	40% 4 14% 29% 14%	4980
	21st to end	Night	59% 4 9% 19% 8% 1	5467
April	1st to 10th	Night	45% 4 12% 26% 13% 1	2055
	11th to 20th	Night	50% 3 5% 24% 16% 2	1820
	21st to end	Night	49% 4 11% 22% 13% 2	1800
May	1st to 10th	Night	32% 4 11% 31% 19% 3	4035
	11th to 20th	Night	41% 4 8% 20% 21% 7%	3597
	21st to end	Night	46% 4 10% 26% 12% 1	3950
June	1st to 10th	Night	33% 5% 15% 31% 14% 2	1442
	11th to 20th	Night	33% 5% 18% 26% 15% 3	1400
	21st to end	Night	28% 5% 17% 30% 17% 3	1400
July	1st to 10th	Night	30% 6% 18% 28% 16%	3145
	11th to 20th	Night	23% 4 18% 40% 13% 2	3168
	21st to end	Night	34% 6% 16% 31% 11% 2	4135
August	1st to 10th	Night	34% 4 15% 29% 15% 4	2916
	11th to 20th	Night	34% 5% 16% 33% 11% 1	2915
	21st to end	Night	28% 6% 19% 32% 13% 2	3266
September	1st to 10th	Night	27% 4 18% 34% 16% 1	2000
	11th to 20th	Night	32% 5% 16% 32% 15%	2154
	21st to end	Night	32% 2 13% 35% 18% 1	2200
October	1st to 10th	Night	26% 2 7% 37% 24% 4	3915
	11th to 20th	Night	36% 3 12% 28% 20% 2	3899
	21st to end	Night	44% 3 15% 25% 13% 1	4343
November	1st to 10th	Night	43% 5% 13% 25% 12% 2	2806
	11th to 20th	Night	52% 4 13% 20% 11% 1	2940
	21st to end	Night	48% 4 17% 22% 7% 2	2940
December	1st to 10th	Night	55% 4 17% 18% 6%	4720
	11th to 20th	Night	61% 3 12% 18% 5%	5532
	21st to end	Night	72% 3 9% 12% 4	7645

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	13% 14% 32% 27% 10% 3	330
	11th to 20th	Day	13% 12% 36% 32% 7% 1	330
	21st to end	Day	10% 14% 39% 23% 14% 1	363
February	1st to 10th	Day	17% 16% 35% 28% 3 1	330
	11th to 20th	Day	13% 14% 36% 25% 10% 2	315
	21st to end	Day	14% 12% 41% 28% 6%	249
March	1st to 10th	Day	16% 12% 40% 24% 7%	300
	11th to 20th	Day	18% 9% 37% 24% 11% 2	300
	21st to end	Day	24% 13% 27% 21% 12% 3	330
April	1st to 10th	Day	23% 14% 32% 22% 8%	445
	11th to 20th	Day	26% 16% 26% 22% 9% 1	645
	21st to end	Day	25% 11% 31% 21% 10% 2	700
May	1st to 10th	Day	19% 12% 32% 24% 10% 3	703
	11th to 20th	Day	20% 12% 27% 27% 13% 2	725
	21st to end	Day	17% 7% 32% 29% 13% 2	789
June	1st to 10th	Day	11% 8% 28% 31% 19% 4	730
	11th to 20th	Day	16% 9% 34% 28% 11% 2	730
	21st to end	Day	15% 7% 33% 27% 16% 3	730
July	1st to 10th	Day	7% 5% 23% 34% 25% 7%	721
	11th to 20th	Day	8% 6% 29% 32% 19% 6%	718
	21st to end	Day	6% 4 25% 36% 23% 6%	794
August	1st to 10th	Day	10% 4 24% 33% 24% 5%	726
	11th to 20th	Day	13% 5% 22% 31% 22% 7%	715
	21st to end	Day	10% 7% 26% 32% 21% 4	783
September	1st to 10th	Day	10% 7% 31% 31% 16% 5%	530
	11th to 20th	Day	13% 5% 33% 32% 13% 5%	374
	21st to end	Day	17% 12% 31% 23% 14% 4	330
October	1st to 10th	Day	17% 12% 32% 27% 10% 4	330
	11th to 20th	Day	16% 19% 35% 21% 8% 1	330
	21st to end	Day	24% 14% 38% 17% 7% 1	363
November	1st to 10th	Day	23% 12% 31% 27% 6% 1	330
	11th to 20th	Day	18% 17% 40% 20% 5%	330
	21st to end	Day	18% 17% 37% 23% 4 1	330
December	1st to 10th	Day	11% 11% 43% 26% 8% 1	330
	11th to 20th	Day	18% 17% 36% 25% 5%	330
	21st to end	Day	26% 10% 39% 20% 6%	363
January	1st to 10th	Night	11% 11% 39% 29% 8% 2	1050
	11th to 20th	Night	13% 11% 39% 29% 7% 1	1050
	21st to end	Night	14% 12% 41% 27% 6%	1155
February	1st to 10th	Night	11% 11% 39% 30% 8%	1050
	11th to 20th	Night	11% 11% 44% 26% 7% 1	1005
	21st to end	Night	15% 12% 33% 30% 9% 1	789
March	1st to 10th	Night	15% 9% 37% 30% 8% 1	640
	11th to 20th	Night	18% 8% 39% 29% 5% 1	600
	21st to end	Night	20% 10% 29% 28% 11% 2	660
April	1st to 10th	Night	18% 12% 34% 30% 6%	600
	11th to 20th	Night	21% 11% 33% 26% 8% 1	593
	21st to end	Night	22% 9% 32% 29% 7% 2	600
May	1st to 10th	Night	16% 10% 34% 30% 10% 1	600
	11th to 20th	Night	18% 8% 31% 33% 10% 1	591
	21st to end	Night	17% 8% 27% 37% 11%	650
June	1st to 10th	Night	12% 6% 28% 37% 16% 1	600
	11th to 20th	Night	11% 4 34% 42% 8%	600
	21st to end	Night	11% 5% 24% 46% 13% 1	600
July	1st to 10th	Night	5% 2 24% 43% 24% 2	585
	11th to 20th	Night	6% 3 28% 45% 17% 1	582
	21st to end	Night	5% 3 26% 45% 19% 2	657
August	1st to 10th	Night	9% 4 20% 45% 20% 2	597
	11th to 20th	Night	11% 5% 19% 38% 26% 2	594
	21st to end	Night	8% 4 26% 37% 23% 1	660
September	1st to 10th	Night	11% 3 29% 38% 17% 2	600
	11th to 20th	Night	12% 6% 28% 36% 18% 1	600
	21st to end	Night	13% 7% 34% 31% 15% 1	600
October	1st to 10th	Night	17% 10% 32% 30% 10% 1	795
	11th to 20th	Night	20% 11% 34% 27% 8%	800
	21st to end	Night	22% 11% 33% 29% 5%	935
November	1st to 10th	Night	15% 12% 34% 31% 8%	1025
	11th to 20th	Night	17% 13% 37% 24% 8% 1	1050
	21st to end	Night	14% 13% 40% 25% 7%	1050
December	1st to 10th	Night	14% 11% 38% 30% 8% 1	1050
	11th to 20th	Night	18% 13% 35% 28% 5% 1	1050
	21st to end	Night	23% 10% 35% 26% 6% 1	1155

Page generated at 2026-02-13 00:42:13. Version ac07

Copyright © 2026 Attilla Danko.