Greenville Recreation Area
Clear Sky Chart
History

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

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	13% 6% 2 6% 4 4 4 4 5% 7% 45%	137325
	Night	14% 6% 2 5% 4 4 4 3 5% 6% 47%	134932
Transparency	Day	37% 6% 11% 25% 18% 4	140921
	Night	37% 5% 11% 24% 19% 4	139416
Seeing	Day	18% 11% 27% 25% 15% 5%	17661
	Night	17% 10% 28% 28% 15% 2	27494

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	15% 8% 3 6% 4 4 4 3 4 5% 45%	4728
	11th to 20th	Day	9% 6% 2 5% 4 3 3 3 4 6% 54%	5310
	21st to end	Day	18% 7% 2 6% 3 3 3 3 4 5% 46%	5812
February	1st to 10th	Day	18% 9% 2 6% 4 4 4 3 5% 5% 41%	1916
	11th to 20th	Day	17% 9% 2 6% 4 4 3 3 4 6% 42%	2048
	21st to end	Day	15% 9% 3 7% 4 4 5% 4 5% 5% 39%	1730
March	1st to 10th	Day	20% 10% 2 6% 3 3 3 2 4 5% 41%	4692
	11th to 20th	Day	11% 6% 2 4 3 3 3 3 4 7% 55%	5090
	21st to end	Day	15% 6% 2 6% 4 4 5% 3 5% 7% 43%	5864
April	1st to 10th	Day	13% 6% 2 6% 4 4 3 3 5% 6% 47%	2520
	11th to 20th	Day	16% 7% 2 7% 5% 3 4 3 5% 7% 41%	2494
	21st to end	Day	18% 6% 2 6% 3 4 4 4 5% 7% 40%	2520
May	1st to 10th	Day	13% 6% 3 8% 5% 6% 5% 4 7% 8% 34%	7021
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	7875
	21st to end	Day	21% 7% 3 7% 5% 4 4 4 6% 7% 32%	9047
June	1st to 10th	Day	9% 5% 2 6% 6% 5% 4 4 6% 9% 44%	2940
	11th to 20th	Day	6% 4 1 5% 4 6% 5% 4 7% 10% 48%	2871
	21st to end	Day	4 3 2 4 4 5% 6% 5% 7% 10% 48%	2800
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 6% 8% 45%	6360
	11th to 20th	Day	5% 3 1 5% 5% 5% 6% 5% 7% 11% 46%	6278
	21st to end	Day	7% 5% 2 6% 5% 6% 6% 5% 7% 11% 40%	6422
August	1st to 10th	Day	4 2 1 4 4 4 4 4 6% 10% 57%	4135
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 46%	3849
	21st to end	Day	6% 4 2 4 4 4 4 3 4 8% 57%	4312
September	1st to 10th	Day	9% 4 2 5% 4 4 4 4 6% 7% 51%	2400
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 5% 8% 48%	2371
	21st to end	Day	12% 5% 2 5% 3 3 4 3 5% 7% 53%	2200
October	1st to 10th	Day	9% 3 2 4 4 3 3 2 4 7% 58%	2005
	11th to 20th	Day	13% 5% 1 5% 3 3 3 2 4 6% 55%	2000
	21st to end	Day	20% 6% 2 5% 3 3 2 3 4 5% 48%	2200
November	1st to 10th	Day	13% 4 2 5% 3 3 3 3 5% 5% 54%	1879
	11th to 20th	Day	13% 7% 2 4 3 4 3 4 4 6% 50%	1890
	21st to end	Day	20% 7% 2 5% 3 3 3 2 3 5% 46%	1890
December	1st to 10th	Day	11% 8% 2 6% 4 3 3 3 4 5% 51%	2698
	11th to 20th	Day	16% 8% 2 7% 4 3 3 3 4 5% 45%	3088
	21st to end	Day	25% 14% 3 7% 4 3 3 2 5% 5% 30%	4070
January	1st to 10th	Night	16% 8% 2 7% 4 4 4 3 4 6% 42%	8190
	11th to 20th	Night	11% 6% 2 6% 3 3 3 3 4 5% 53%	7680
	21st to end	Night	19% 7% 2 5% 4 4 4 3 4 5% 43%	8402
February	1st to 10th	Night	17% 10% 3 6% 3 3 3 3 4 6% 42%	2701
	11th to 20th	Night	17% 7% 3 6% 4 4 3 3 4 5% 44%	2458
	21st to end	Night	17% 7% 2 6% 4 3 3 3 5% 5% 45%	2076
March	1st to 10th	Night	19% 8% 3 7% 5% 4 4 3 4 4 41%	5412
	11th to 20th	Night	12% 7% 2 6% 4 4 3 3 5% 5% 49%	5090
	21st to end	Night	13% 6% 2 7% 4 4 4 4 5% 7% 44%	5292
April	1st to 10th	Night	12% 5% 2 5% 3 3 4 5% 5% 7% 49%	2100
	11th to 20th	Night	13% 6% 2 5% 4 4 4 4 5% 7% 46%	2075
	21st to end	Night	19% 6% 2 6% 4 4 5% 4 4 7% 40%	2100
May	1st to 10th	Night	16% 7% 2 5% 4 5% 4 4 6% 8% 39%	5832
	11th to 20th	Night	14% 7% 2 7% 4 4 4 4 5% 8% 40%	4981
	21st to end	Night	20% 9% 3 8% 4 4 4 3 6% 6% 31%	5139
June	1st to 10th	Night	9% 4 3 5% 4 3 5% 4 7% 8% 48%	1680
	11th to 20th	Night	6% 4 1 3 4 3 3 3 6% 10% 57%	1640
	21st to end	Night	4 2 1 3 4 3 4 4 8% 10% 57%	1600
July	1st to 10th	Night	8% 4 2 6% 4 4 5% 4 6% 9% 47%	3618
	11th to 20th	Night	5% 4 1 5% 4 4 5% 4 7% 10% 51%	3680
	21st to end	Night	7% 5% 2 6% 4 3 4 4 7% 11% 48%	4449
August	1st to 10th	Night	4 2 1 3 3 3 4 4 6% 8% 63%	3019
	11th to 20th	Night	8% 4 2 5% 4 4 5% 3 6% 8% 51%	3200
	21st to end	Night	5% 3 1 4 3 3 4 3 6% 9% 59%	3586
September	1st to 10th	Night	10% 4 2 5% 3 2 3 3 6% 7% 55%	2000
	11th to 20th	Night	8% 5% 2 6% 4 3 5% 4 4 7% 52%	2008
	21st to end	Night	10% 4 1 5% 3 3 4 3 4 7% 55%	2200
October	1st to 10th	Night	7% 3 1 4 4 3 2 3 4 6% 64%	2390
	11th to 20th	Night	13% 4 2 4 3 3 3 2 5% 5% 58%	2400
	21st to end	Night	20% 7% 2 5% 2 3 3 2 3 4 49%	2640
November	1st to 10th	Night	12% 5% 2 4 2 2 2 3 4 6% 58%	2636
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 5% 6% 53%	2730
	21st to end	Night	18% 6% 2 5% 3 3 3 2 4 6% 47%	2730
December	1st to 10th	Night	14% 7% 2 4 3 3 4 3 5% 6% 48%	4709
	11th to 20th	Night	17% 8% 2 5% 4 4 4 2 4 6% 46%	5339
	21st to end	Night	25% 9% 3 7% 4 4 4 3 4 5% 33%	7150

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	42% 3 13% 28% 13% 2	4729
	11th to 20th	Day	32% 3 7% 30% 23% 6%	5310
	21st to end	Day	42% 3 9% 20% 17% 9%	5812
February	1st to 10th	Day	46% 4 13% 22% 14% 1	1916
	11th to 20th	Day	45% 4 10% 22% 15% 5%	2058
	21st to end	Day	44% 5% 9% 20% 15% 6%	1730
March	1st to 10th	Day	46% 4 5% 20% 16% 9%	4692
	11th to 20th	Day	31% 3 8% 28% 22% 8%	5090
	21st to end	Day	41% 5% 12% 28% 14% 1	5866
April	1st to 10th	Day	38% 5% 10% 24% 20% 3	2520
	11th to 20th	Day	43% 5% 11% 20% 16% 5%	2494
	21st to end	Day	43% 7% 11% 23% 15% 1	2520
May	1st to 10th	Day	45% 7% 11% 23% 13% 1	7056
	11th to 20th	Day	45% 7% 10% 19% 16% 2	7879
	21st to end	Day	50% 7% 10% 19% 13% 2	9061
June	1st to 10th	Day	36% 8% 12% 24% 18% 2	2940
	11th to 20th	Day	29% 8% 12% 28% 19% 4	2871
	21st to end	Day	27% 9% 17% 26% 17% 5%	2800
July	1st to 10th	Day	34% 7% 11% 24% 20% 3	6291
	11th to 20th	Day	29% 9% 17% 30% 14% 1	6203
	21st to end	Day	35% 9% 15% 30% 10% 1	6240
August	1st to 10th	Day	22% 7% 14% 32% 24% 1	4121
	11th to 20th	Day	35% 7% 14% 25% 17% 3	3885
	21st to end	Day	25% 5% 13% 36% 17% 3	4311
September	1st to 10th	Day	31% 7% 12% 28% 19% 4	2400
	11th to 20th	Day	34% 6% 9% 24% 25% 2	2371
	21st to end	Day	31% 5% 8% 24% 27% 3	2200
October	1st to 10th	Day	16% 4 6% 18% 45% 12%	3265
	11th to 20th	Day	22% 3 6% 21% 38% 9%	3240
	21st to end	Day	31% 4 5% 29% 26% 5%	3538
November	1st to 10th	Day	32% 4 10% 26% 21% 7%	1879
	11th to 20th	Day	36% 4 8% 24% 23% 6%	1890
	21st to end	Day	43% 3 8% 25% 20% 2	1890
December	1st to 10th	Day	36% 4 7% 35% 17% 1	2698
	11th to 20th	Day	42% 4 8% 28% 16% 2	3085
	21st to end	Day	57% 4 11% 16% 10% 2	4070
January	1st to 10th	Night	44% 3 12% 27% 13% 1	8191
	11th to 20th	Night	34% 3 7% 26% 26% 5%	7680
	21st to end	Night	44% 4 9% 23% 17% 4	8402
February	1st to 10th	Night	45% 4 11% 22% 17% 2	2701
	11th to 20th	Night	43% 4 11% 21% 18% 4	2459
	21st to end	Night	41% 4 8% 22% 19% 5%	2076
March	1st to 10th	Night	47% 4 6% 19% 16% 8%	5412
	11th to 20th	Night	37% 4 8% 22% 17% 11%	5090
	21st to end	Night	39% 5% 10% 30% 13% 1	5292
April	1st to 10th	Night	32% 6% 13% 25% 20% 4	2100
	11th to 20th	Night	37% 6% 11% 22% 20% 5%	2075
	21st to end	Night	44% 5% 9% 23% 17% 2	2100
May	1st to 10th	Night	43% 7% 15% 25% 10% 1	5862
	11th to 20th	Night	42% 7% 13% 22% 15% 2	4982
	21st to end	Night	52% 7% 10% 17% 11% 3	5149
June	1st to 10th	Night	32% 8% 13% 23% 22% 2	1680
	11th to 20th	Night	22% 7% 12% 30% 23% 6%	1640
	21st to end	Night	20% 8% 16% 28% 21% 7%	1600
July	1st to 10th	Night	33% 8% 12% 23% 22% 3	3580
	11th to 20th	Night	28% 9% 17% 29% 15% 3	3635
	21st to end	Night	29% 7% 21% 28% 14% 1	4320
August	1st to 10th	Night	19% 7% 18% 34% 22% 1	3009
	11th to 20th	Night	31% 6% 16% 27% 16% 4	3230
	21st to end	Night	21% 5% 11% 39% 21% 3	3586
September	1st to 10th	Night	28% 7% 9% 30% 21% 6%	2000
	11th to 20th	Night	32% 6% 10% 25% 24% 3	2008
	21st to end	Night	30% 6% 9% 21% 30% 5%	2200
October	1st to 10th	Night	14% 3 6% 17% 44% 17%	3910
	11th to 20th	Night	22% 2 6% 18% 38% 13%	3899
	21st to end	Night	31% 3 6% 24% 30% 6%	4252
November	1st to 10th	Night	29% 4 10% 27% 25% 5%	2636
	11th to 20th	Night	32% 3 8% 25% 24% 7%	2730
	21st to end	Night	40% 3 8% 25% 21% 3	2730
December	1st to 10th	Night	37% 4 8% 32% 18% 2	4709
	11th to 20th	Night	42% 3 10% 23% 21% 2	5341
	21st to end	Night	53% 5% 12% 19% 10% 2	7150

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	29% 17% 35% 16% 2	330
	11th to 20th	Day	29% 24% 34% 12%	330
	21st to end	Day	22% 23% 41% 11% 2	363
February	1st to 10th	Day	28% 22% 35% 10% 4	330
	11th to 20th	Day	34% 26% 28% 10% 1 1	330
	21st to end	Day	32% 22% 36% 9% 2	273
March	1st to 10th	Day	29% 21% 35% 12% 3	330
	11th to 20th	Day	32% 23% 32% 10% 2	330
	21st to end	Day	28% 19% 37% 12% 3 1	489
April	1st to 10th	Day	24% 17% 33% 20% 6%	540
	11th to 20th	Day	27% 19% 28% 18% 7% 1	532
	21st to end	Day	21% 16% 36% 20% 5% 2	540
May	1st to 10th	Day	19% 18% 33% 22% 7% 1	543
	11th to 20th	Day	20% 12% 30% 23% 12% 3	659
	21st to end	Day	14% 7% 31% 29% 14% 4	844
June	1st to 10th	Day	13% 6% 25% 27% 21% 7%	780
	11th to 20th	Day	6% 4 24% 40% 21% 6%	756
	21st to end	Day	6% 5% 28% 36% 18% 7%	730
July	1st to 10th	Day	10% 2 15% 29% 30% 13%	721
	11th to 20th	Day	6% 3 18% 35% 30% 9%	718
	21st to end	Day	9% 3 14% 37% 29% 9%	794
August	1st to 10th	Day	8% 1 17% 38% 27% 9%	666
	11th to 20th	Day	13% 3 19% 29% 28% 8%	519
	21st to end	Day	10% 1 15% 28% 32% 14%	583
September	1st to 10th	Day	8% 3 15% 37% 28% 8%	530
	11th to 20th	Day	10% 4 14% 27% 30% 14%	530
	21st to end	Day	14% 9% 20% 31% 19% 8%	530
October	1st to 10th	Day	11% 8% 24% 37% 14% 6%	335
	11th to 20th	Day	20% 10% 34% 23% 12% 2	330
	21st to end	Day	29% 16% 33% 18% 5%	363
November	1st to 10th	Day	19% 15% 36% 21% 8% 1	330
	11th to 20th	Day	22% 15% 32% 21% 8% 1	330
	21st to end	Day	32% 15% 28% 17% 7% 1	330
December	1st to 10th	Day	21% 21% 35% 15% 7% 2	330
	11th to 20th	Day	26% 20% 30% 18% 5%	330
	21st to end	Day	33% 19% 32% 12% 4	363
January	1st to 10th	Night	24% 16% 33% 22% 4	1050
	11th to 20th	Night	24% 20% 34% 19% 3	1050
	21st to end	Night	22% 14% 39% 24% 1	1155
February	1st to 10th	Night	23% 15% 37% 22% 3	1021
	11th to 20th	Night	25% 19% 36% 17% 2	823
	21st to end	Night	24% 20% 36% 19% 2	692
March	1st to 10th	Night	24% 15% 35% 24% 2	811
	11th to 20th	Night	23% 14% 33% 27% 4	630
	21st to end	Night	24% 12% 35% 23% 6%	693
April	1st to 10th	Night	15% 16% 39% 25% 5%	630
	11th to 20th	Night	18% 17% 30% 25% 9%	623
	21st to end	Night	18% 12% 36% 24% 9%	630
May	1st to 10th	Night	18% 8% 32% 29% 11% 1	630
	11th to 20th	Night	19% 7% 28% 30% 14% 2	621
	21st to end	Night	13% 5% 25% 33% 20% 3	683
June	1st to 10th	Night	10% 4 19% 36% 28% 3	630
	11th to 20th	Night	6% 2 19% 45% 26% 3	615
	21st to end	Night	4 2 21% 38% 32% 3	600
July	1st to 10th	Night	8% 2 12% 31% 40% 8%	585
	11th to 20th	Night	6% 1 9% 41% 37% 6%	582
	21st to end	Night	8% 2 12% 34% 38% 6%	657
August	1st to 10th	Night	6% 2 12% 36% 39% 5%	597
	11th to 20th	Night	8% 2 12% 32% 41% 5%	594
	21st to end	Night	7% 1 12% 33% 40% 7%	660
September	1st to 10th	Night	12% 2 12% 34% 37% 4	600
	11th to 20th	Night	10% 2 13% 32% 36% 7%	608
	21st to end	Night	11% 5% 22% 30% 27% 5%	800
October	1st to 10th	Night	8% 6% 18% 38% 26% 4	800
	11th to 20th	Night	15% 9% 28% 29% 18% 1	800
	21st to end	Night	24% 11% 29% 26% 10% 1	880
November	1st to 10th	Night	15% 10% 34% 29% 12% 1	820
	11th to 20th	Night	18% 11% 31% 31% 9%	840
	21st to end	Night	24% 13% 29% 26% 8%	840
December	1st to 10th	Night	22% 14% 30% 29% 5%	1039
	11th to 20th	Night	25% 11% 31% 26% 6%	1050
	21st to end	Night	28% 14% 31% 23% 4	1155

Page generated at 2026-06-13 01:31:40. Version ac07

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