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 2025-02-21.

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 3 5% 7% 45%	108560
	Night	14% 6% 2 5% 4 3 4 3 5% 6% 48%	110197
Transparency	Day	37% 6% 11% 25% 19% 4	112195
	Night	36% 5% 10% 25% 20% 4	114703
Seeing	Day	17% 11% 26% 25% 16% 5%	15835
	Night	17% 10% 27% 28% 15% 2	25798

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% 8% 3 7% 4 3 3 3 4 5% 45%	3640
	11th to 20th	Day	11% 7% 2 5% 4 3 3 3 5% 6% 51%	4080
	21st to end	Day	20% 6% 1 5% 3 3 3 3 4 5% 46%	4488
February	1st to 10th	Day	18% 10% 2 6% 4 4 4 2 5% 5% 40%	1825
	11th to 20th	Day	17% 8% 2 6% 4 4 3 3 4 6% 42%	1948
	21st to end	Day	17% 9% 3 7% 4 4 5% 4 5% 6% 38%	1570
March	1st to 10th	Day	24% 9% 2 6% 3 3 3 2 4 5% 39%	3202
	11th to 20th	Day	15% 6% 2 5% 3 3 3 2 4 6% 52%	3480
	21st to end	Day	16% 6% 2 6% 4 4 5% 3 6% 6% 42%	4005
April	1st to 10th	Day	12% 6% 2 6% 4 4 3 4 5% 6% 48%	2280
	11th to 20th	Day	16% 7% 2 7% 5% 3 3 3 5% 7% 41%	2254
	21st to end	Day	18% 7% 2 6% 4 4 4 4 5% 6% 41%	2280
May	1st to 10th	Day	14% 5% 2 8% 5% 5% 5% 4 7% 9% 34%	3765
	11th to 20th	Day	17% 6% 3 6% 4 4 5% 3 7% 8% 39%	4217
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 7% 8% 40%	4824
June	1st to 10th	Day	9% 5% 2 6% 6% 5% 4 4 6% 9% 45%	2660
	11th to 20th	Day	5% 3 1 5% 4 6% 5% 4 7% 10% 50%	2660
	21st to end	Day	5% 3 2 4 4 5% 6% 5% 7% 10% 48%	2660
July	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 5% 7% 9% 42%	4440
	11th to 20th	Day	5% 3 1 5% 4 5% 5% 4 6% 10% 52%	4386
	21st to end	Day	9% 6% 3 8% 6% 7% 6% 6% 6% 10% 34%	4465
August	1st to 10th	Day	4 2 1 4 4 4 4 4 6% 10% 56%	4008
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 45%	3729
	21st to end	Day	6% 4 2 4 3 4 4 3 4 8% 57%	4180
September	1st to 10th	Day	10% 4 2 5% 4 4 4 4 6% 7% 51%	2280
	11th to 20th	Day	11% 5% 2 6% 4 4 4 3 5% 8% 48%	2253
	21st to end	Day	11% 5% 2 5% 3 3 4 3 5% 7% 53%	2090
October	1st to 10th	Day	9% 4 2 4 3 3 3 2 4 7% 58%	1905
	11th to 20th	Day	14% 5% 1 5% 3 3 3 2 4 6% 54%	1900
	21st to end	Day	19% 6% 2 5% 3 3 3 3 4 5% 48%	2090
November	1st to 10th	Day	13% 4 2 5% 3 3 3 3 4 5% 54%	1788
	11th to 20th	Day	13% 8% 2 4 3 3 3 3 4 6% 50%	1800
	21st to end	Day	20% 7% 2 5% 3 3 3 2 3 5% 46%	1800
December	1st to 10th	Day	11% 8% 2 6% 4 3 3 3 4 5% 51%	2618
	11th to 20th	Day	16% 8% 2 7% 4 3 3 3 4 5% 44%	3008
	21st to end	Day	25% 14% 3 7% 4 3 3 2 5% 5% 30%	3982
January	1st to 10th	Night	17% 8% 3 7% 4 4 4 3 5% 7% 40%	6320
	11th to 20th	Night	14% 7% 2 6% 3 3 3 3 5% 5% 49%	5900
	21st to end	Night	20% 7% 2 5% 3 3 3 3 4 5% 45%	6490
February	1st to 10th	Night	18% 10% 3 6% 4 3 3 3 4 5% 40%	2573
	11th to 20th	Night	17% 7% 3 7% 4 3 3 3 4 5% 44%	2338
	21st to end	Night	19% 7% 2 6% 4 3 3 3 5% 6% 43%	1885
March	1st to 10th	Night	23% 7% 2 6% 4 3 3 2 3 4 43%	3681
	11th to 20th	Night	15% 6% 2 5% 4 4 3 3 4 5% 50%	3480
	21st to end	Night	13% 7% 2 6% 4 4 4 4 5% 7% 44%	3611
April	1st to 10th	Night	11% 5% 2 4 3 3 4 5% 5% 7% 50%	1900
	11th to 20th	Night	13% 6% 2 5% 3 4 4 4 6% 7% 45%	1875
	21st to end	Night	19% 6% 2 6% 4 4 5% 4 4 7% 40%	1900
May	1st to 10th	Night	20% 5% 2 4 3 4 3 4 5% 7% 43%	3130
	11th to 20th	Night	15% 6% 2 6% 4 3 4 4 5% 8% 43%	2676
	21st to end	Night	12% 7% 2 6% 4 4 5% 4 7% 8% 42%	2743
June	1st to 10th	Night	9% 4 3 5% 4 4 5% 4 7% 8% 48%	1520
	11th to 20th	Night	4 4 1 3 3 3 3 3 6% 10% 59%	1520
	21st to end	Night	4 2 1 4 4 3 4 4 8% 10% 57%	1520
July	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 6% 9% 49%	2530
	11th to 20th	Night	5% 3 1 4 3 3 5% 3 6% 9% 58%	2579
	21st to end	Night	10% 7% 2 7% 4 4 4 4 8% 9% 40%	3098
August	1st to 10th	Night	4 2 1 3 3 3 4 4 5% 8% 63%	2926
	11th to 20th	Night	8% 4 2 5% 4 4 5% 3 6% 8% 51%	3100
	21st to end	Night	5% 3 1 4 3 3 4 3 6% 9% 59%	3476
September	1st to 10th	Night	10% 4 2 5% 3 2 3 2 6% 7% 55%	1900
	11th to 20th	Night	8% 6% 2 6% 4 3 4 3 4 7% 52%	1907
	21st to end	Night	10% 4 1 4 3 4 4 3 4 7% 55%	2090
October	1st to 10th	Night	6% 3 1 4 4 3 3 3 4 6% 63%	2270
	11th to 20th	Night	13% 5% 2 4 3 3 3 2 5% 5% 57%	2280
	21st to end	Night	19% 6% 2 5% 2 3 3 3 3 4 50%	2508
November	1st to 10th	Night	13% 5% 2 4 3 2 2 3 4 5% 58%	2507
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 5% 6% 53%	2600
	21st to end	Night	18% 6% 2 5% 3 3 3 2 4 5% 48%	2600
December	1st to 10th	Night	14% 7% 2 4 3 3 4 3 5% 5% 49%	4569
	11th to 20th	Night	17% 8% 2 5% 4 4 3 2 4 6% 46%	5199
	21st to end	Night	25% 9% 3 7% 4 4 4 3 4 5% 32%	6996

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	43% 3 12% 26% 14% 2	3641
	11th to 20th	Day	34% 3 8% 27% 21% 6%	4080
	21st to end	Day	42% 3 10% 17% 18% 10%	4488
February	1st to 10th	Day	46% 4 12% 22% 14% 1	1825
	11th to 20th	Day	45% 4 10% 21% 15% 5%	1958
	21st to end	Day	46% 5% 10% 20% 14% 6%	1570
March	1st to 10th	Day	50% 5% 6% 18% 14% 8%	3202
	11th to 20th	Day	36% 4 9% 26% 19% 6%	3480
	21st to end	Day	41% 6% 15% 22% 15% 1	4005
April	1st to 10th	Day	37% 5% 10% 25% 20% 2	2280
	11th to 20th	Day	43% 5% 10% 21% 17% 5%	2254
	21st to end	Day	44% 7% 10% 22% 16% 1	2280
May	1st to 10th	Day	44% 10% 13% 20% 12% 2	3800
	11th to 20th	Day	42% 9% 11% 24% 13% 1	4221
	21st to end	Day	40% 8% 11% 21% 18% 1	4837
June	1st to 10th	Day	35% 8% 13% 24% 18% 2	2660
	11th to 20th	Day	28% 9% 12% 28% 20% 4	2660
	21st to end	Day	27% 9% 17% 25% 16% 5%	2660
July	1st to 10th	Day	36% 8% 13% 25% 15% 3	4371
	11th to 20th	Day	26% 7% 12% 33% 19% 2	4311
	21st to end	Day	43% 9% 13% 26% 8% 1	4325
August	1st to 10th	Day	22% 7% 14% 31% 25% 1	3994
	11th to 20th	Day	35% 7% 14% 25% 17% 3	3765
	21st to end	Day	25% 5% 13% 36% 17% 3	4179
September	1st to 10th	Day	31% 7% 12% 28% 19% 4	2280
	11th to 20th	Day	35% 6% 9% 23% 25% 2	2253
	21st to end	Day	31% 5% 9% 26% 27% 3	2090
October	1st to 10th	Day	16% 4 6% 17% 45% 12%	3165
	11th to 20th	Day	22% 3 6% 21% 39% 9%	3140
	21st to end	Day	30% 4 5% 29% 27% 5%	3428
November	1st to 10th	Day	33% 4 10% 25% 22% 7%	1788
	11th to 20th	Day	36% 4 7% 24% 24% 6%	1800
	21st to end	Day	43% 3 8% 25% 20% 2	1800
December	1st to 10th	Day	36% 4 7% 35% 17% 1	2618
	11th to 20th	Day	42% 4 8% 28% 16% 2	3005
	21st to end	Day	57% 4 11% 16% 10% 2	3982
January	1st to 10th	Night	44% 4 10% 26% 15% 1	6320
	11th to 20th	Night	37% 4 8% 27% 21% 3	5900
	21st to end	Night	43% 4 8% 23% 17% 5%	6490
February	1st to 10th	Night	46% 4 10% 21% 16% 2	2573
	11th to 20th	Night	43% 4 11% 20% 18% 4	2339
	21st to end	Night	43% 5% 9% 21% 18% 5%	1885
March	1st to 10th	Night	46% 4 7% 20% 15% 7%	3681
	11th to 20th	Night	37% 5% 10% 23% 18% 6%	3480
	21st to end	Night	38% 6% 11% 32% 11% 1	3611
April	1st to 10th	Night	32% 6% 12% 25% 21% 4	1900
	11th to 20th	Night	37% 5% 11% 22% 20% 6%	1875
	21st to end	Night	44% 6% 9% 23% 16% 2	1900
May	1st to 10th	Night	39% 8% 16% 24% 12% 1	3160
	11th to 20th	Night	39% 9% 15% 20% 17% 1	2677
	21st to end	Night	38% 9% 13% 23% 17% 2	2751
June	1st to 10th	Night	32% 8% 14% 23% 22% 2	1520
	11th to 20th	Night	19% 8% 13% 32% 23% 6%	1520
	21st to end	Night	20% 8% 16% 28% 20% 8%	1520
July	1st to 10th	Night	31% 8% 14% 27% 16% 4	2490
	11th to 20th	Night	22% 6% 12% 34% 21% 4	2531
	21st to end	Night	38% 8% 16% 25% 12% 1	2999
August	1st to 10th	Night	18% 6% 18% 33% 23% 1	2916
	11th to 20th	Night	31% 6% 16% 26% 16% 5%	3130
	21st to end	Night	21% 5% 11% 39% 20% 3	3476
September	1st to 10th	Night	28% 7% 8% 30% 20% 6%	1900
	11th to 20th	Night	32% 6% 10% 24% 24% 4	1907
	21st to end	Night	29% 6% 9% 22% 30% 4	2090
October	1st to 10th	Night	14% 3 6% 17% 44% 16%	3790
	11th to 20th	Night	23% 2 5% 18% 38% 14%	3779
	21st to end	Night	31% 3 6% 24% 30% 6%	4120
November	1st to 10th	Night	30% 4 10% 26% 25% 5%	2507
	11th to 20th	Night	33% 3 8% 24% 25% 8%	2600
	21st to end	Night	39% 3 8% 25% 22% 3	2600
December	1st to 10th	Night	37% 4 8% 31% 18% 2	4569
	11th to 20th	Night	42% 3 10% 23% 20% 2	5201
	21st to end	Night	53% 5% 12% 19% 10% 2	6996

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% 18% 35% 15% 2	300
	11th to 20th	Day	30% 24% 33% 13%	300
	21st to end	Day	21% 23% 41% 12% 2	330
February	1st to 10th	Day	30% 22% 34% 10% 4	300
	11th to 20th	Day	34% 27% 27% 11% 1 1	300
	21st to end	Day	33% 24% 33% 8% 2	225
March	1st to 10th	Day	28% 21% 34% 14% 3	270
	11th to 20th	Day	33% 22% 31% 11% 3	270
	21st to end	Day	30% 18% 34% 13% 4 1	411
April	1st to 10th	Day	23% 18% 32% 20% 6%	460
	11th to 20th	Day	26% 18% 28% 19% 8% 1	452
	21st to end	Day	22% 16% 34% 20% 6% 2	460
May	1st to 10th	Day	19% 16% 33% 22% 8% 2	463
	11th to 20th	Day	20% 10% 28% 25% 14% 4	570
	21st to end	Day	11% 8% 32% 29% 14% 5%	734
June	1st to 10th	Day	13% 6% 24% 27% 23% 8%	680
	11th to 20th	Day	5% 4 23% 41% 22% 6%	680
	21st to end	Day	6% 5% 30% 35% 18% 7%	680
July	1st to 10th	Day	11% 3 15% 29% 30% 13%	671
	11th to 20th	Day	6% 3 19% 34% 30% 10%	668
	21st to end	Day	9% 3 15% 37% 28% 9%	739
August	1st to 10th	Day	8% 1 16% 38% 28% 10%	619
	11th to 20th	Day	14% 3 20% 29% 27% 7%	479
	21st to end	Day	11% 1 14% 27% 32% 15%	539
September	1st to 10th	Day	8% 3 14% 37% 29% 9%	490
	11th to 20th	Day	11% 5% 15% 28% 29% 12%	490
	21st to end	Day	14% 9% 20% 30% 19% 8%	490
October	1st to 10th	Day	11% 9% 23% 37% 13% 6%	305
	11th to 20th	Day	21% 10% 35% 23% 10% 2	300
	21st to end	Day	27% 16% 32% 19% 6%	330
November	1st to 10th	Day	19% 15% 35% 21% 9% 1	300
	11th to 20th	Day	23% 15% 31% 21% 9% 1	300
	21st to end	Day	31% 14% 29% 18% 7% 1	300
December	1st to 10th	Day	22% 20% 35% 14% 8% 2	300
	11th to 20th	Day	28% 19% 30% 18% 5%	300
	21st to end	Day	34% 20% 29% 12% 4	330
January	1st to 10th	Night	24% 17% 33% 22% 4	1000
	11th to 20th	Night	24% 20% 33% 19% 4	1000
	21st to end	Night	22% 14% 39% 24% 1	1100
February	1st to 10th	Night	24% 16% 36% 21% 3	973
	11th to 20th	Night	25% 20% 36% 17% 2	783
	21st to end	Night	25% 20% 36% 17% 3	629
March	1st to 10th	Night	24% 14% 35% 25% 2	734
	11th to 20th	Night	22% 13% 32% 29% 4	570
	21st to end	Night	25% 10% 35% 23% 6%	627
April	1st to 10th	Night	15% 17% 38% 25% 5%	570
	11th to 20th	Night	18% 17% 29% 26% 10% 1	563
	21st to end	Night	18% 13% 36% 24% 8%	570
May	1st to 10th	Night	18% 8% 32% 29% 12% 1	570
	11th to 20th	Night	19% 5% 28% 30% 15% 2	561
	21st to end	Night	12% 4 25% 33% 21% 4	617
June	1st to 10th	Night	10% 4 18% 35% 29% 3	570
	11th to 20th	Night	4 1 19% 46% 27% 3	570
	21st to end	Night	4 2 22% 38% 31% 3	570
July	1st to 10th	Night	7% 2 12% 31% 40% 8%	555
	11th to 20th	Night	6% 1 10% 40% 36% 6%	552
	21st to end	Night	9% 2 13% 34% 37% 6%	624
August	1st to 10th	Night	6% 2 12% 36% 39% 5%	567
	11th to 20th	Night	8% 2 13% 33% 39% 5%	564
	21st to end	Night	7% 1 12% 32% 41% 7%	627
September	1st to 10th	Night	12% 2 12% 33% 38% 4	570
	11th to 20th	Night	10% 2 14% 31% 35% 7%	577
	21st to end	Night	11% 5% 22% 29% 28% 5%	760
October	1st to 10th	Night	8% 6% 19% 37% 26% 4	760
	11th to 20th	Night	16% 9% 29% 29% 17% 1	760
	21st to end	Night	23% 11% 29% 27% 11% 1	836
November	1st to 10th	Night	15% 9% 33% 29% 13% 1	780
	11th to 20th	Night	18% 11% 31% 31% 9%	800
	21st to end	Night	23% 12% 29% 26% 8% 1	800
December	1st to 10th	Night	22% 13% 30% 29% 5%	989
	11th to 20th	Night	26% 11% 30% 27% 6%	1000
	21st to end	Night	28% 14% 31% 23% 4	1100

Page generated at 2025-02-18 02:26:28. Version ac07

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