Staunton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Staunton clear sky chart from 2005-11-06 to 2026-07-16.

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	12% 6% 2 6% 4 5% 5% 4 6% 8% 43%	137540
	Night	12% 6% 2 6% 4 4 4 4 6% 7% 45%	135120
Transparency	Day	38% 7% 12% 22% 16% 4	141146
	Night	37% 7% 12% 23% 18% 4	139585
Seeing	Day	17% 14% 25% 23% 14% 6%	17198
	Night	16% 11% 26% 32% 14% 2	27038

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% 7% 2 6% 4 4 4 3 5% 5% 48%	5258
	11th to 20th	Day	11% 8% 2 6% 4 4 3 3 4 4 52%	5280
	21st to end	Day	11% 7% 3 7% 4 4 4 3 4 5% 47%	5780
February	1st to 10th	Day	11% 7% 2 8% 5% 4 5% 4 5% 6% 43%	1890
	11th to 20th	Day	15% 7% 3 6% 4 4 4 4 5% 7% 41%	1843
	21st to end	Day	14% 8% 3 6% 4 5% 5% 3 5% 6% 41%	1806
March	1st to 10th	Day	14% 8% 2 6% 4 5% 4 4 6% 7% 42%	5045
	11th to 20th	Day	9% 5% 2 5% 3 4 3 3 6% 7% 52%	5090
	21st to end	Day	12% 8% 2 7% 5% 5% 5% 4 5% 6% 42%	5586
April	1st to 10th	Day	9% 7% 2 6% 4 5% 4 4 6% 7% 47%	2451
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 6% 7% 47%	2494
	21st to end	Day	14% 7% 2 6% 5% 4 4 3 6% 6% 42%	2604
May	1st to 10th	Day	12% 5% 2 7% 5% 5% 6% 5% 7% 8% 37%	7616
	11th to 20th	Day	17% 6% 2 6% 4 5% 5% 4 5% 8% 38%	7626
	21st to end	Day	20% 4 2 5% 4 4 4 4 6% 8% 38%	8605
June	1st to 10th	Day	10% 4 2 5% 5% 6% 5% 5% 6% 10% 42%	2940
	11th to 20th	Day	9% 6% 2 6% 6% 5% 6% 5% 7% 10% 39%	2940
	21st to end	Day	7% 4 2 5% 6% 4 5% 4 7% 11% 43%	2931
July	1st to 10th	Day	7% 4 2 6% 5% 5% 6% 5% 8% 10% 43%	6030
	11th to 20th	Day	9% 4 2 7% 6% 7% 7% 6% 9% 12% 32%	5965
	21st to end	Day	10% 5% 3 7% 5% 6% 6% 5% 8% 10% 35%	6424
August	1st to 10th	Day	13% 5% 2 7% 6% 6% 6% 5% 8% 10% 34%	4234
	11th to 20th	Day	9% 5% 2 7% 6% 5% 6% 5% 7% 10% 38%	4148
	21st to end	Day	9% 3 2 5% 4 4 5% 4 7% 9% 47%	4312
September	1st to 10th	Day	12% 5% 2 6% 4 5% 4 3 5% 5% 49%	2400
	11th to 20th	Day	12% 7% 2 5% 4 5% 4 3 5% 7% 44%	2266
	21st to end	Day	22% 7% 2 5% 4 4 4 4 5% 6% 37%	2159
October	1st to 10th	Day	14% 5% 2 6% 3 4 4 3 4 6% 49%	2000
	11th to 20th	Day	14% 4 2 5% 3 3 3 3 5% 6% 51%	2000
	21st to end	Day	11% 5% 2 5% 3 3 4 4 4 6% 53%	2200
November	1st to 10th	Day	10% 5% 2 4 4 3 4 3 5% 6% 55%	2057
	11th to 20th	Day	11% 6% 2 5% 3 4 4 3 6% 5% 51%	1876
	21st to end	Day	11% 5% 2 6% 4 3 3 4 5% 7% 49%	1680
December	1st to 10th	Day	9% 5% 2 4 4 4 5% 4 5% 6% 52%	2680
	11th to 20th	Day	17% 6% 2 4 3 3 3 3 5% 8% 46%	3070
	21st to end	Day	17% 7% 2 6% 4 4 5% 4 5% 8% 37%	4254
January	1st to 10th	Night	10% 6% 2 5% 4 4 4 4 5% 6% 50%	7635
	11th to 20th	Night	10% 7% 2 5% 3 3 3 3 4 6% 55%	7680
	21st to end	Night	11% 6% 2 6% 4 4 3 2 4 5% 52%	8401
February	1st to 10th	Night	10% 7% 3 5% 4 4 4 4 6% 7% 45%	2730
	11th to 20th	Night	17% 8% 2 6% 4 4 4 3 5% 6% 41%	2663
	21st to end	Night	12% 8% 2 6% 5% 3 5% 4 6% 7% 43%	1993
March	1st to 10th	Night	15% 6% 2 5% 3 4 4 4 5% 6% 47%	5028
	11th to 20th	Night	10% 4 2 4 3 3 4 4 6% 8% 52%	5090
	21st to end	Night	11% 7% 2 6% 5% 5% 5% 3 6% 7% 45%	5588
April	1st to 10th	Night	11% 6% 3 6% 4 4 5% 4 5% 8% 44%	2168
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 6% 9% 47%	2075
	21st to end	Night	15% 4 2 5% 4 4 5% 3 6% 6% 46%	2032
May	1st to 10th	Night	14% 6% 2 6% 4 5% 5% 4 6% 8% 40%	5237
	11th to 20th	Night	17% 5% 2 5% 4 4 5% 4 7% 8% 38%	5234
	21st to end	Night	20% 6% 2 6% 4 4 5% 4 6% 8% 35%	5529
June	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 7% 10% 45%	1680
	11th to 20th	Night	9% 4 2 7% 4 4 5% 5% 7% 9% 45%	1680
	21st to end	Night	8% 4 2 4 5% 5% 5% 4 7% 10% 47%	1682
July	1st to 10th	Night	8% 4 2 5% 4 4 6% 5% 7% 9% 45%	4148
	11th to 20th	Night	10% 5% 2 8% 6% 7% 7% 6% 9% 10% 30%	4102
	21st to end	Night	9% 5% 3 8% 6% 6% 6% 5% 8% 10% 35%	4427
August	1st to 10th	Night	15% 5% 2 6% 4 5% 5% 4 7% 10% 36%	2915
	11th to 20th	Night	9% 5% 3 8% 5% 5% 5% 5% 8% 8% 39%	2875
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 9% 46%	3576
September	1st to 10th	Night	11% 5% 2 6% 4 3 4 4 5% 7% 50%	2000
	11th to 20th	Night	13% 6% 2 5% 4 4 5% 3 5% 8% 46%	2130
	21st to end	Night	22% 7% 2 6% 4 3 4 3 5% 5% 40%	2240
October	1st to 10th	Night	16% 5% 2 5% 3 4 4 2 5% 6% 48%	2400
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 6% 51%	2400
	21st to end	Night	12% 4 2 5% 4 3 3 3 4 7% 53%	2640
November	1st to 10th	Night	10% 7% 2 5% 4 3 3 3 4 5% 53%	2461
	11th to 20th	Night	11% 6% 2 5% 4 4 3 3 5% 6% 51%	2738
	21st to end	Night	11% 6% 2 5% 4 4 5% 3 5% 6% 50%	2940
December	1st to 10th	Night	8% 5% 2 5% 3 4 4 4 6% 6% 54%	4720
	11th to 20th	Night	15% 7% 2 5% 4 4 5% 4 5% 5% 43%	5345
	21st to end	Night	14% 7% 2 5% 4 4 5% 4 6% 8% 41%	6938

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	38% 3 10% 22% 20% 8%	5259
	11th to 20th	Day	36% 3 6% 17% 23% 14%	5280
	21st to end	Day	40% 4 6% 26% 19% 5%	5780
February	1st to 10th	Day	42% 6% 10% 21% 17% 4	1890
	11th to 20th	Day	42% 6% 10% 20% 17% 4	1852
	21st to end	Day	43% 7% 10% 18% 16% 6%	1806
March	1st to 10th	Day	42% 5% 9% 18% 17% 10%	5045
	11th to 20th	Day	30% 6% 9% 26% 20% 9%	5090
	21st to end	Day	44% 7% 9% 17% 17% 7%	5586
April	1st to 10th	Day	36% 7% 11% 21% 19% 7%	2451
	11th to 20th	Day	35% 7% 12% 22% 19% 5%	2494
	21st to end	Day	42% 6% 11% 23% 13% 4	2604
May	1st to 10th	Day	41% 9% 12% 22% 14% 1	7651
	11th to 20th	Day	44% 7% 13% 23% 13% 1	7630
	21st to end	Day	43% 9% 12% 18% 15% 3	8620
June	1st to 10th	Day	36% 10% 15% 23% 15% 1	2940
	11th to 20th	Day	38% 12% 16% 21% 13% 1	2940
	21st to end	Day	33% 11% 16% 25% 13% 1	2931
July	1st to 10th	Day	34% 12% 19% 20% 11% 4	5965
	11th to 20th	Day	41% 13% 19% 20% 6% 1	5896
	21st to end	Day	41% 10% 15% 22% 12%	6240
August	1st to 10th	Day	43% 10% 18% 22% 6%	4221
	11th to 20th	Day	37% 11% 14% 27% 11% 1	4187
	21st to end	Day	31% 10% 19% 26% 12% 1	4312
September	1st to 10th	Day	37% 8% 15% 17% 20% 4	2400
	11th to 20th	Day	39% 7% 9% 24% 19% 3	2266
	21st to end	Day	48% 7% 10% 17% 16% 2	2159
October	1st to 10th	Day	31% 5% 9% 20% 29% 5%	3260
	11th to 20th	Day	25% 4 9% 26% 23% 13%	3240
	21st to end	Day	22% 4 10% 30% 22% 13%	3538
November	1st to 10th	Day	31% 4 10% 24% 26% 5%	2057
	11th to 20th	Day	34% 5% 10% 20% 22% 8%	1876
	21st to end	Day	35% 5% 11% 24% 22% 3	1680
December	1st to 10th	Day	32% 6% 11% 25% 19% 7%	2680
	11th to 20th	Day	38% 5% 13% 22% 17% 5%	3066
	21st to end	Day	43% 7% 14% 20% 15% 1	4254
January	1st to 10th	Night	34% 4 10% 23% 21% 7%	7636
	11th to 20th	Night	32% 3 8% 21% 25% 11%	7680
	21st to end	Night	36% 4 7% 26% 22% 6%	8401
February	1st to 10th	Night	38% 7% 11% 24% 17% 3	2730
	11th to 20th	Night	44% 5% 9% 19% 17% 6%	2665
	21st to end	Night	39% 7% 12% 22% 14% 6%	1993
March	1st to 10th	Night	38% 5% 9% 21% 18% 9%	5028
	11th to 20th	Night	28% 5% 9% 25% 26% 7%	5090
	21st to end	Night	39% 5% 12% 20% 19% 5%	5588
April	1st to 10th	Night	38% 7% 13% 18% 19% 4	2168
	11th to 20th	Night	32% 8% 15% 21% 20% 4	2075
	21st to end	Night	38% 6% 12% 27% 15% 3	2032
May	1st to 10th	Night	41% 9% 13% 21% 12% 3	5264
	11th to 20th	Night	42% 8% 14% 25% 10%	5235
	21st to end	Night	45% 9% 14% 19% 10% 3	5537
June	1st to 10th	Night	34% 9% 14% 27% 15% 1	1680
	11th to 20th	Night	34% 10% 18% 24% 12% 1	1680
	21st to end	Night	31% 10% 17% 21% 17% 2	1682
July	1st to 10th	Night	35% 12% 18% 21% 13% 2	4105
	11th to 20th	Night	46% 14% 17% 16% 6%	4051
	21st to end	Night	41% 11% 17% 21% 9%	4297
August	1st to 10th	Night	42% 10% 18% 24% 6% 1	2904
	11th to 20th	Night	38% 11% 15% 24% 11%	2902
	21st to end	Night	33% 9% 17% 31% 8% 2	3576
September	1st to 10th	Night	34% 9% 14% 21% 18% 5%	2000
	11th to 20th	Night	36% 7% 12% 25% 18% 3	2130
	21st to end	Night	47% 7% 10% 18% 15% 2	2240
October	1st to 10th	Night	39% 6% 11% 19% 20% 5%	3920
	11th to 20th	Night	26% 4 9% 22% 30% 9%	3899
	21st to end	Night	21% 3 10% 30% 28% 8%	4252
November	1st to 10th	Night	34% 5% 9% 22% 25% 6%	2461
	11th to 20th	Night	35% 5% 8% 21% 24% 6%	2738
	21st to end	Night	36% 5% 10% 24% 21% 5%	2940
December	1st to 10th	Night	30% 5% 12% 28% 22% 3	4720
	11th to 20th	Night	42% 5% 11% 18% 17% 6%	5348
	21st to end	Night	39% 6% 14% 22% 17% 1	6938

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% 36% 23% 14% 3	330
	11th to 20th	Day	27% 34% 26% 11% 2	330
	21st to end	Day	24% 30% 31% 13% 1	363
February	1st to 10th	Day	23% 30% 33% 12% 3	330
	11th to 20th	Day	38% 28% 25% 8% 1	330
	21st to end	Day	29% 23% 27% 18% 3	401
March	1st to 10th	Day	20% 25% 29% 20% 6%	540
	11th to 20th	Day	24% 25% 28% 18% 4 2	540
	21st to end	Day	21% 21% 32% 21% 5% 1	594
April	1st to 10th	Day	22% 25% 25% 18% 9% 1	540
	11th to 20th	Day	20% 17% 28% 20% 12% 3	532
	21st to end	Day	21% 18% 30% 19% 10% 2	540
May	1st to 10th	Day	18% 21% 30% 21% 7% 3	543
	11th to 20th	Day	21% 11% 28% 23% 14% 4	567
	21st to end	Day	20% 9% 23% 24% 18% 6%	617
June	1st to 10th	Day	11% 8% 29% 27% 17% 7%	570
	11th to 20th	Day	11% 9% 25% 29% 16% 10%	570
	21st to end	Day	9% 5% 28% 31% 19% 9%	570
July	1st to 10th	Day	10% 4 16% 29% 27% 14%	565
	11th to 20th	Day	5% 2 18% 35% 27% 13%	544
	21st to end	Day	10% 4 18% 31% 26% 12%	576
August	1st to 10th	Day	13% 5% 18% 27% 25% 12%	526
	11th to 20th	Day	11% 4 19% 26% 27% 13%	519
	21st to end	Day	10% 4 14% 34% 23% 16%	583
September	1st to 10th	Day	12% 5% 18% 27% 22% 15%	530
	11th to 20th	Day	14% 5% 15% 28% 27% 11%	530
	21st to end	Day	27% 10% 19% 23% 16% 5%	530
October	1st to 10th	Day	17% 6% 21% 29% 20% 6%	530
	11th to 20th	Day	16% 15% 23% 25% 17% 3	530
	21st to end	Day	16% 15% 31% 24% 11% 3	583
November	1st to 10th	Day	14% 14% 29% 28% 11% 3	535
	11th to 20th	Day	20% 15% 30% 24% 9% 1	361
	21st to end	Day	20% 21% 33% 18% 6% 1	220
December	1st to 10th	Day	21% 24% 35% 14% 6%	220
	11th to 20th	Day	22% 22% 25% 21% 9% 1	220
	21st to end	Day	20% 25% 32% 17% 7%	289
January	1st to 10th	Night	17% 21% 36% 23% 3	840
	11th to 20th	Night	18% 20% 33% 26% 3	840
	21st to end	Night	16% 19% 39% 23% 2	924
February	1st to 10th	Night	16% 19% 34% 29% 3	840
	11th to 20th	Night	24% 20% 35% 19% 1	823
	21st to end	Night	19% 17% 38% 23% 2	692
March	1st to 10th	Night	17% 19% 33% 27% 4	840
	11th to 20th	Night	22% 19% 30% 22% 6% 1	840
	21st to end	Night	19% 15% 34% 27% 5% 1	924
April	1st to 10th	Night	16% 19% 35% 24% 5%	840
	11th to 20th	Night	13% 15% 31% 29% 11%	831
	21st to end	Night	17% 10% 31% 34% 8% 1	772
May	1st to 10th	Night	17% 9% 28% 32% 13% 1	630
	11th to 20th	Night	18% 6% 23% 37% 14% 1	621
	21st to end	Night	16% 2 18% 40% 23% 2	605
June	1st to 10th	Night	9% 1 19% 49% 20% 1	420
	11th to 20th	Night	10% 3 17% 45% 24% 2	420
	21st to end	Night	8% 4 18% 45% 23% 3	422
July	1st to 10th	Night	9% 3 11% 34% 36% 6%	615
	11th to 20th	Night	5% 2 8% 38% 41% 7%	597
	21st to end	Night	6% 3 13% 39% 33% 6%	657
August	1st to 10th	Night	12% 2 10% 38% 34% 4	597
	11th to 20th	Night	12% 3 10% 38% 34% 4	594
	21st to end	Night	13% 2 11% 35% 35% 4	870
September	1st to 10th	Night	14% 3 10% 37% 32% 5%	800
	11th to 20th	Night	15% 3 13% 33% 32% 5%	800
	21st to end	Night	25% 5% 19% 32% 19% 2	800
October	1st to 10th	Night	18% 6% 17% 33% 22% 4	800
	11th to 20th	Night	15% 11% 25% 33% 15% 1	800
	21st to end	Night	15% 11% 27% 34% 12% 1	880
November	1st to 10th	Night	15% 9% 26% 36% 13% 2	820
	11th to 20th	Night	15% 15% 29% 32% 9% 1	840
	21st to end	Night	14% 16% 29% 32% 8% 1	840
December	1st to 10th	Night	19% 14% 34% 28% 6%	840
	11th to 20th	Night	16% 14% 32% 32% 6%	840
	21st to end	Night	17% 14% 31% 35% 3	924

Page generated at 2026-07-13 03:14:48. Version ac07

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