St Clairsville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the St Clairsville clear sky chart from 2005-11-06 to 2025-05-26.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 32%	113998
	Night	15% 11% 4 9% 5% 4 4 3 5% 6% 32%	115272
Transparency	Day	50% 6% 11% 20% 11% 1	117673
	Night	50% 6% 10% 20% 12% 2	119736
Seeing	Day	22% 16% 27% 20% 11% 4	15404
	Night	21% 12% 27% 26% 12% 1	25417

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	16% 19% 7% 20% 5% 4 3 2 3 5% 17%	4056
	11th to 20th	Day	13% 22% 9% 13% 8% 5% 4 2 3 3 18%	4060
	21st to end	Day	19% 19% 6% 11% 8% 5% 4 3 3 4 17%	4466
February	1st to 10th	Day	20% 17% 5% 9% 6% 4 4 3 4 4 24%	1800
	11th to 20th	Day	16% 15% 6% 13% 5% 4 3 3 5% 6% 23%	1793
	21st to end	Day	19% 14% 6% 9% 4 3 3 4 4 5% 29%	1650
March	1st to 10th	Day	16% 15% 5% 10% 5% 4 4 3 4 5% 30%	4926
	11th to 20th	Day	12% 8% 3 8% 5% 5% 5% 4 5% 6% 39%	4980
	21st to end	Day	18% 9% 3 9% 6% 5% 5% 4 5% 6% 31%	5465
April	1st to 10th	Day	14% 13% 4 8% 6% 4 5% 4 5% 7% 30%	2258
	11th to 20th	Day	15% 10% 3 8% 5% 5% 4 4 5% 6% 35%	2462
	21st to end	Day	18% 9% 3 7% 5% 5% 5% 4 6% 6% 33%	2600
May	1st to 10th	Day	21% 9% 3 8% 6% 5% 5% 4 5% 7% 27%	4212
	11th to 20th	Day	19% 9% 3 8% 4 5% 4 4 5% 7% 31%	4211
	21st to end	Day	12% 6% 2 7% 5% 5% 6% 5% 8% 10% 35%	4541
June	1st to 10th	Day	11% 8% 3 7% 5% 5% 5% 4 7% 9% 36%	2646
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 5% 8% 9% 35%	2660
	21st to end	Day	12% 6% 2 7% 4 5% 6% 5% 7% 9% 36%	2589
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 4 6% 9% 39%	4120
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 9% 41%	4120
	21st to end	Day	12% 8% 3 8% 6% 6% 5% 4 6% 9% 33%	4466
August	1st to 10th	Day	11% 7% 3 8% 5% 7% 6% 5% 7% 9% 32%	4104
	11th to 20th	Day	10% 6% 3 8% 5% 5% 7% 5% 8% 9% 35%	4044
	21st to end	Day	6% 4 2 6% 5% 6% 6% 6% 7% 9% 42%	4377
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 3 5% 7% 47%	2212
	11th to 20th	Day	9% 6% 2 5% 4 4 4 4 6% 9% 45%	2090
	21st to end	Day	18% 9% 3 7% 4 4 5% 3 4 7% 35%	2090
October	1st to 10th	Day	13% 6% 3 7% 4 4 5% 3 6% 7% 41%	1940
	11th to 20th	Day	16% 8% 3 8% 5% 4 5% 3 5% 5% 39%	1900
	21st to end	Day	21% 9% 3 7% 4 3 4 3 4 6% 35%	2090
November	1st to 10th	Day	10% 9% 3 6% 5% 4 5% 3 5% 6% 45%	1833
	11th to 20th	Day	17% 15% 3 6% 5% 4 4 3 5% 5% 32%	1788
	21st to end	Day	17% 14% 5% 9% 6% 4 4 4 5% 4 28%	1600
December	1st to 10th	Day	18% 12% 4 17% 5% 5% 3 3 4 5% 24%	2600
	11th to 20th	Day	23% 17% 5% 11% 4 3 3 3 4 4 23%	2990
	21st to end	Day	21% 21% 5% 11% 6% 4 4 3 4 5% 16%	4259
January	1st to 10th	Night	15% 16% 8% 20% 6% 5% 4 3 3 4 16%	5889
	11th to 20th	Night	15% 18% 8% 13% 9% 6% 5% 3 4 4 16%	5900
	21st to end	Night	21% 15% 5% 12% 6% 4 4 2 3 4 24%	6490
February	1st to 10th	Night	19% 14% 4 10% 6% 5% 4 4 4 5% 26%	2600
	11th to 20th	Night	20% 14% 5% 11% 5% 6% 4 4 5% 5% 24%	2488
	21st to end	Night	18% 15% 5% 11% 5% 5% 4 3 4 5% 25%	1980
March	1st to 10th	Night	19% 12% 5% 9% 5% 4 4 2 3 5% 33%	4926
	11th to 20th	Night	11% 8% 4 7% 5% 5% 4 4 5% 7% 40%	4980
	21st to end	Night	16% 9% 3 9% 5% 5% 4 3 5% 6% 35%	5467
April	1st to 10th	Night	17% 13% 3 8% 4 4 4 3 6% 5% 32%	2140
	11th to 20th	Night	16% 8% 2 8% 5% 4 5% 4 6% 7% 36%	1903
	21st to end	Night	15% 10% 3 7% 5% 3 4 4 5% 7% 39%	1800
May	1st to 10th	Night	26% 11% 4 7% 4 5% 4 3 4 6% 26%	2903
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 3 5% 7% 38%	2902
	21st to end	Night	10% 6% 3 7% 4 4 5% 4 7% 10% 40%	3130
June	1st to 10th	Night	8% 7% 3 6% 5% 5% 6% 4 6% 8% 44%	1530
	11th to 20th	Night	10% 5% 2 5% 4 5% 6% 5% 8% 11% 39%	1520
	21st to end	Night	11% 5% 2 5% 5% 5% 4 5% 6% 8% 44%	1584
July	1st to 10th	Night	9% 7% 3 8% 5% 4 4 3 6% 8% 43%	2840
	11th to 20th	Night	9% 6% 2 7% 4 4 5% 3 6% 9% 45%	2840
	21st to end	Night	8% 8% 3 7% 5% 5% 5% 4 6% 8% 41%	3087
August	1st to 10th	Night	10% 8% 3 8% 5% 5% 6% 5% 6% 10% 35%	2825
	11th to 20th	Night	10% 8% 3 8% 4 5% 4 4 7% 7% 41%	2785
	21st to end	Night	6% 4 2 6% 5% 5% 5% 4 7% 9% 46%	3247
September	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 5% 6% 50%	1965
	11th to 20th	Night	9% 5% 2 5% 4 3 3 3 5% 8% 54%	2090
	21st to end	Night	15% 8% 2 7% 4 4 5% 4 4 6% 42%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 45%	2238
	11th to 20th	Night	14% 8% 3 7% 4 5% 4 4 5% 7% 40%	2280
	21st to end	Night	21% 8% 3 6% 4 4 3 3 5% 7% 37%	2508
November	1st to 10th	Night	12% 8% 3 5% 4 3 3 3 5% 7% 47%	2460
	11th to 20th	Night	16% 12% 3 7% 5% 5% 4 4 5% 5% 33%	2608
	21st to end	Night	18% 13% 4 8% 5% 5% 4 4 5% 5% 29%	2800
December	1st to 10th	Night	17% 13% 5% 16% 5% 5% 4 3 5% 5% 21%	4580
	11th to 20th	Night	18% 17% 7% 11% 5% 4 3 3 4 5% 22%	5205
	21st to end	Night	20% 18% 6% 10% 6% 5% 4 3 4 6% 18%	6692

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	72% 5% 9% 10% 4	4057
	11th to 20th	Day	73% 3 7% 9% 6% 2	4060
	21st to end	Day	72% 4 7% 11% 6%	4466
February	1st to 10th	Day	64% 4 9% 14% 8% 1	1800
	11th to 20th	Day	61% 6% 10% 16% 7% 1	1802
	21st to end	Day	58% 4 11% 17% 8% 2	1650
March	1st to 10th	Day	55% 6% 8% 23% 8% 1	4926
	11th to 20th	Day	43% 6% 10% 28% 10% 2	4980
	21st to end	Day	52% 5% 8% 20% 14% 1	5465
April	1st to 10th	Day	52% 6% 11% 17% 10% 3	2258
	11th to 20th	Day	48% 7% 11% 16% 15% 3	2462
	21st to end	Day	49% 7% 10% 20% 12% 2	2600
May	1st to 10th	Day	54% 8% 10% 20% 7% 1	4250
	11th to 20th	Day	49% 8% 11% 21% 10% 1	4215
	21st to end	Day	39% 11% 15% 21% 11% 3	4554
June	1st to 10th	Day	42% 8% 14% 23% 12% 1	2646
	11th to 20th	Day	41% 10% 14% 22% 12% 1	2660
	21st to end	Day	41% 9% 13% 21% 13% 1	2589
July	1st to 10th	Day	40% 7% 13% 23% 16% 2	4055
	11th to 20th	Day	37% 7% 11% 28% 16% 1	4051
	21st to end	Day	45% 7% 12% 17% 16% 2	4324
August	1st to 10th	Day	44% 9% 14% 22% 10%	4091
	11th to 20th	Day	41% 8% 11% 27% 12%	4083
	21st to end	Day	34% 9% 13% 28% 14% 2	4377
September	1st to 10th	Day	37% 6% 12% 21% 20% 4	2212
	11th to 20th	Day	34% 6% 14% 28% 15% 3	2090
	21st to end	Day	49% 5% 10% 21% 15% 1	2090
October	1st to 10th	Day	31% 6% 9% 32% 21% 2	3226
	11th to 20th	Day	41% 6% 12% 22% 15% 5%	3140
	21st to end	Day	36% 4 12% 26% 20% 1	3428
November	1st to 10th	Day	40% 5% 10% 26% 16% 3	1833
	11th to 20th	Day	53% 5% 11% 19% 11% 2	1788
	21st to end	Day	58% 5% 11% 16% 8% 1	1600
December	1st to 10th	Day	63% 4 14% 15% 4	2600
	11th to 20th	Day	66% 3 11% 15% 5%	2986
	21st to end	Day	70% 6% 9% 11% 4	4259
January	1st to 10th	Night	72% 5% 7% 12% 4	5889
	11th to 20th	Night	71% 5% 9% 10% 5% 1	5900
	21st to end	Night	66% 3 9% 14% 6% 2	6490
February	1st to 10th	Night	61% 5% 10% 17% 7% 1	2600
	11th to 20th	Night	62% 4 10% 17% 7% 1	2490
	21st to end	Night	62% 5% 9% 15% 8% 2	1980
March	1st to 10th	Night	54% 5% 8% 22% 11% 1	4926
	11th to 20th	Night	41% 6% 11% 29% 9% 3	4980
	21st to end	Night	49% 5% 9% 21% 13% 2	5467
April	1st to 10th	Night	52% 6% 9% 18% 13% 2	2140
	11th to 20th	Night	44% 8% 13% 17% 15% 4	1903
	21st to end	Night	43% 7% 12% 21% 15% 2	1800
May	1st to 10th	Night	58% 7% 9% 17% 8% 2	2930
	11th to 20th	Night	45% 8% 10% 24% 11% 1	2903
	21st to end	Night	34% 11% 15% 23% 12% 4	3138
June	1st to 10th	Night	36% 9% 12% 23% 17% 3	1530
	11th to 20th	Night	35% 9% 16% 22% 16% 2	1520
	21st to end	Night	35% 10% 13% 24% 16% 2	1584
July	1st to 10th	Night	39% 6% 10% 24% 17% 4	2795
	11th to 20th	Night	34% 7% 13% 29% 16% 1	2786
	21st to end	Night	38% 9% 11% 19% 19% 4	2988
August	1st to 10th	Night	43% 10% 15% 23% 10% 1	2814
	11th to 20th	Night	39% 8% 9% 23% 19% 1	2812
	21st to end	Night	31% 8% 14% 30% 14% 3	3247
September	1st to 10th	Night	34% 7% 10% 21% 21% 6%	1965
	11th to 20th	Night	29% 6% 14% 26% 24% 2	2090
	21st to end	Night	42% 7% 10% 21% 18% 1	2090
October	1st to 10th	Night	33% 5% 9% 27% 25% 3	3732
	11th to 20th	Night	35% 6% 11% 24% 16% 8%	3779
	21st to end	Night	34% 3 8% 28% 24% 3	4120
November	1st to 10th	Night	38% 5% 12% 23% 18% 4	2460
	11th to 20th	Night	52% 5% 10% 18% 13% 2	2608
	21st to end	Night	56% 6% 11% 19% 8% 1	2800
December	1st to 10th	Night	65% 5% 10% 16% 3 1	4580
	11th to 20th	Night	64% 4 14% 14% 3	5208
	21st to end	Night	67% 6% 9% 13% 5%	6692

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	34% 25% 28% 9% 4	300
	11th to 20th	Day	36% 28% 28% 7% 1	300
	21st to end	Day	34% 32% 27% 5% 2	330
February	1st to 10th	Day	36% 26% 30% 8% 1	300
	11th to 20th	Day	39% 28% 26% 5% 1	300
	21st to end	Day	34% 29% 32% 4	249
March	1st to 10th	Day	30% 23% 29% 14% 3	491
	11th to 20th	Day	30% 21% 31% 13% 4 1	500
	21st to end	Day	31% 21% 31% 14% 2 1	550
April	1st to 10th	Day	30% 20% 28% 15% 5% 1	500
	11th to 20th	Day	25% 23% 26% 16% 8% 2	492
	21st to end	Day	26% 20% 33% 14% 6% 2	500
May	1st to 10th	Day	24% 25% 26% 16% 7% 2	503
	11th to 20th	Day	21% 16% 31% 19% 9% 4	527
	21st to end	Day	15% 11% 28% 24% 17% 5%	549
June	1st to 10th	Day	13% 12% 28% 31% 13% 4	490
	11th to 20th	Day	14% 14% 24% 31% 12% 6%	490
	21st to end	Day	13% 12% 33% 25% 13% 4	490
July	1st to 10th	Day	14% 7% 23% 27% 18% 11%	485
	11th to 20th	Day	11% 7% 26% 30% 17% 9%	484
	21st to end	Day	15% 7% 24% 28% 18% 8%	532
August	1st to 10th	Day	13% 6% 22% 31% 20% 8%	486
	11th to 20th	Day	14% 7% 24% 29% 16% 11%	479
	21st to end	Day	9% 5% 25% 26% 23% 11%	539
September	1st to 10th	Day	16% 7% 23% 27% 20% 8%	490
	11th to 20th	Day	10% 4 19% 30% 28% 9%	490
	21st to end	Day	24% 12% 25% 20% 14% 4	490
October	1st to 10th	Day	15% 9% 30% 26% 16% 4	490
	11th to 20th	Day	22% 15% 28% 23% 10% 2	490
	21st to end	Day	26% 19% 29% 19% 7% 1	539
November	1st to 10th	Day	18% 19% 36% 16% 9% 2	371
	11th to 20th	Day	29% 17% 32% 13% 7% 1	293
	21st to end	Day	28% 28% 31% 14% 1	200
December	1st to 10th	Day	32% 25% 32% 7% 5% 1	200
	11th to 20th	Day	30% 28% 28% 13% 2	200
	21st to end	Day	33% 27% 26% 11% 2	285
January	1st to 10th	Night	29% 20% 32% 16% 3	800
	11th to 20th	Night	30% 21% 32% 15% 3	800
	21st to end	Night	27% 23% 30% 17% 3	880
February	1st to 10th	Night	29% 19% 29% 22% 1	800
	11th to 20th	Night	31% 20% 32% 15% 1	783
	21st to end	Night	28% 18% 33% 18% 2	660
March	1st to 10th	Night	24% 19% 33% 21% 4	800
	11th to 20th	Night	25% 20% 28% 21% 6% 1	800
	21st to end	Night	26% 17% 31% 20% 5% 1	880
April	1st to 10th	Night	26% 16% 31% 21% 6%	800
	11th to 20th	Night	21% 15% 33% 20% 10% 1	719
	21st to end	Night	20% 10% 36% 27% 7% 1	600
May	1st to 10th	Night	21% 14% 23% 31% 10% 1	600
	11th to 20th	Night	21% 9% 27% 29% 14% 1	591
	21st to end	Night	11% 4 24% 38% 21% 3	634
June	1st to 10th	Night	8% 6% 28% 38% 19% 1	390
	11th to 20th	Night	10% 7% 21% 40% 22%	380
	21st to end	Night	9% 5% 25% 41% 19% 1	444
July	1st to 10th	Night	11% 4 18% 36% 25% 6%	555
	11th to 20th	Night	8% 4 20% 35% 29% 4	552
	21st to end	Night	11% 4 15% 36% 32% 2	624
August	1st to 10th	Night	8% 3 16% 42% 29% 3	567
	11th to 20th	Night	10% 3 16% 36% 29% 6%	564
	21st to end	Night	10% 3 19% 31% 31% 6%	698
September	1st to 10th	Night	13% 4 18% 32% 28% 5%	760
	11th to 20th	Night	10% 3 18% 36% 28% 5%	760
	21st to end	Night	19% 7% 23% 27% 20% 3	760
October	1st to 10th	Night	16% 8% 23% 30% 21% 3	760
	11th to 20th	Night	21% 10% 29% 28% 11% 1	760
	21st to end	Night	25% 12% 27% 28% 8% 1	836
November	1st to 10th	Night	18% 11% 28% 29% 13%	780
	11th to 20th	Night	24% 16% 29% 23% 7% 1	800
	21st to end	Night	28% 13% 31% 22% 5% 1	800
December	1st to 10th	Night	29% 18% 30% 19% 5%	800
	11th to 20th	Night	30% 17% 30% 20% 3	800
	21st to end	Night	30% 16% 32% 20% 2	880

Page generated at 2025-05-23 09:21:03. Version ac07

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