Greenville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greenville clear sky chart from 2005-11-06 to 2024-11-04.

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% 10% 4 8% 5% 5% 5% 4 5% 7% 34%	101241
	Night	14% 11% 4 8% 5% 5% 4 3 5% 6% 34%	97823
Transparency	Day	47% 6% 11% 22% 13% 1	104826
	Night	49% 6% 11% 21% 12% 1	102379
Seeing	Day	18% 12% 29% 23% 13% 5%	15825
	Night	19% 9% 30% 30% 11% 1	25672

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	14% 22% 7% 12% 7% 6% 4 3 4 4 16%	2527
	11th to 20th	Day	14% 18% 7% 18% 14% 10% 4 3 4 3 7%	2530
	21st to end	Day	21% 24% 8% 12% 7% 5% 3 2 3 4 9%	2783
February	1st to 10th	Day	12% 15% 5% 14% 10% 6% 5% 4 5% 5% 20%	1733
	11th to 20th	Day	12% 15% 5% 14% 9% 5% 4 3 4 5% 24%	1848
	21st to end	Day	15% 14% 6% 12% 7% 4 4 4 5% 6% 22%	1570
March	1st to 10th	Day	15% 13% 4 8% 5% 4 5% 3 5% 6% 32%	3120
	11th to 20th	Day	11% 8% 5% 10% 7% 6% 5% 4 6% 6% 33%	3410
	21st to end	Day	19% 12% 6% 8% 5% 4 4 3 4 5% 30%	3923
April	1st to 10th	Day	17% 14% 3 7% 5% 4 4 4 5% 6% 31%	2280
	11th to 20th	Day	17% 11% 3 6% 4 4 4 3 5% 6% 36%	2333
	21st to end	Day	17% 9% 3 7% 5% 5% 5% 3 5% 7% 34%	2470
May	1st to 10th	Day	16% 9% 3 7% 4 4 5% 4 5% 8% 36%	4082
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 4 6% 8% 39%	4081
	21st to end	Day	10% 6% 2 7% 5% 4 5% 4 6% 8% 44%	4793
June	1st to 10th	Day	10% 7% 2 5% 4 5% 5% 4 7% 9% 43%	2660
	11th to 20th	Day	11% 6% 2 5% 4 5% 4 4 6% 8% 44%	2660
	21st to end	Day	11% 6% 2 7% 5% 5% 4 4 7% 8% 42%	2660
July	1st to 10th	Day	10% 7% 3 8% 5% 5% 5% 5% 7% 9% 36%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 11% 49%	4440
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 7% 8% 45%	4813
August	1st to 10th	Day	11% 6% 2 6% 4 6% 6% 4 6% 8% 41%	4114
	11th to 20th	Day	10% 6% 2 5% 4 5% 5% 3 5% 8% 47%	4044
	21st to end	Day	7% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	4288
September	1st to 10th	Day	10% 7% 3 6% 5% 4 4 4 6% 7% 43%	2233
	11th to 20th	Day	11% 5% 1 5% 4 4 5% 3 7% 8% 47%	2090
	21st to end	Day	12% 7% 3 7% 6% 5% 5% 3 5% 8% 41%	2090
October	1st to 10th	Day	16% 7% 3 7% 4 4 4 3 4 6% 42%	2090
	11th to 20th	Day	20% 10% 3 8% 5% 5% 5% 3 5% 7% 29%	1849
	21st to end	Day	21% 11% 3 9% 7% 5% 5% 3 5% 6% 25%	1881
November	1st to 10th	Day	12% 11% 3 7% 5% 4 4 4 5% 6% 37%	1699
	11th to 20th	Day	13% 16% 5% 9% 6% 5% 4 4 6% 6% 25%	1710
	21st to end	Day	20% 15% 6% 8% 5% 4 4 3 4 6% 24%	1710
December	1st to 10th	Day	13% 18% 9% 15% 7% 5% 4 3 5% 4 17%	1586
	11th to 20th	Day	13% 17% 7% 12% 8% 6% 6% 4 5% 6% 17%	1918
	21st to end	Day	22% 22% 9% 12% 6% 5% 4 3 4 4 11%	2783
January	1st to 10th	Night	15% 19% 8% 13% 7% 5% 4 3 5% 5% 18%	4428
	11th to 20th	Night	13% 18% 8% 17% 10% 8% 4 3 4 4 12%	4440
	21st to end	Night	20% 20% 9% 11% 6% 4 4 3 4 5% 14%	4884
February	1st to 10th	Night	13% 16% 5% 11% 9% 6% 5% 4 5% 5% 21%	2443
	11th to 20th	Night	11% 14% 6% 11% 7% 6% 5% 5% 6% 6% 24%	2218
	21st to end	Night	16% 14% 4 12% 5% 6% 5% 4 4 5% 25%	1884
March	1st to 10th	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 38%	3733
	11th to 20th	Night	10% 8% 2 6% 4 4 4 3 6% 8% 44%	3549
	21st to end	Night	16% 11% 6% 9% 5% 4 4 3 5% 7% 30%	3736
April	1st to 10th	Night	15% 11% 3 7% 5% 4 4 4 5% 6% 37%	1900
	11th to 20th	Night	20% 8% 2 7% 4 4 4 3 5% 6% 37%	1796
	21st to end	Night	17% 8% 3 5% 5% 4 4 4 5% 7% 38%	1710
May	1st to 10th	Night	13% 8% 4 8% 4 5% 5% 4 5% 7% 38%	2813
	11th to 20th	Night	17% 6% 2 6% 4 4 4 3 4 7% 42%	2812
	21st to end	Night	13% 8% 3 7% 4 3 4 4 5% 7% 43%	2756
June	1st to 10th	Night	10% 6% 2 5% 5% 4 4 4 6% 8% 46%	1520
	11th to 20th	Night	11% 5% 2 6% 4 4 4 4 6% 8% 45%	1520
	21st to end	Night	8% 6% 2 5% 6% 4 4 4 6% 8% 47%	1520
July	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 4 7% 8% 42%	2530
	11th to 20th	Night	6% 4 2 4 4 3 4 4 6% 7% 56%	2530
	21st to end	Night	6% 4 2 6% 4 5% 6% 3 6% 8% 48%	2750
August	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 5% 8% 50%	2814
	11th to 20th	Night	10% 4 2 5% 4 3 5% 4 5% 8% 50%	2785
	21st to end	Night	9% 6% 2 6% 5% 5% 4 4 5% 8% 46%	3366
September	1st to 10th	Night	9% 5% 1 5% 4 4 4 4 5% 7% 52%	1926
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 6% 54%	2090
	21st to end	Night	13% 8% 3 6% 4 4 4 4 5% 7% 43%	2090
October	1st to 10th	Night	16% 5% 2 6% 3 3 4 3 4 6% 49%	2090
	11th to 20th	Night	18% 11% 3 7% 5% 5% 3 3 5% 7% 34%	2326
	21st to end	Night	21% 10% 3 7% 5% 3 5% 4 4 6% 32%	2717
November	1st to 10th	Night	13% 9% 3 7% 4 5% 4 3 6% 6% 40%	2452
	11th to 20th	Night	14% 14% 3 9% 6% 6% 5% 5% 8% 7% 25%	2470
	21st to end	Night	18% 14% 4 9% 5% 4 4 3 5% 5% 28%	2470
December	1st to 10th	Night	15% 18% 6% 11% 7% 7% 5% 4 4 6% 17%	2592
	11th to 20th	Night	15% 17% 6% 12% 7% 5% 5% 4 5% 6% 18%	3279
	21st to end	Night	26% 21% 6% 10% 5% 4 3 3 4 5% 14%	4884

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% 6% 9% 11% 2	2528
	11th to 20th	Day	82% 5% 7% 5% 2	2530
	21st to end	Day	81% 4 7% 6% 2	2783
February	1st to 10th	Day	66% 6% 8% 14% 5%	1733
	11th to 20th	Day	63% 5% 9% 15% 8%	1858
	21st to end	Day	61% 6% 11% 15% 6%	1570
March	1st to 10th	Day	53% 5% 11% 21% 9%	3120
	11th to 20th	Day	50% 6% 13% 20% 10% 1	3410
	21st to end	Day	57% 4 11% 18% 9% 1	3923
April	1st to 10th	Day	54% 5% 10% 19% 12% 1	2280
	11th to 20th	Day	49% 5% 9% 21% 13% 2	2333
	21st to end	Day	49% 6% 11% 19% 13% 3	2470
May	1st to 10th	Day	45% 6% 11% 20% 15% 2	4120
	11th to 20th	Day	40% 8% 13% 26% 13% 1	4085
	21st to end	Day	37% 7% 11% 22% 22% 1	4806
June	1st to 10th	Day	36% 7% 12% 28% 15% 2	2660
	11th to 20th	Day	36% 6% 13% 22% 20% 1	2660
	21st to end	Day	38% 8% 13% 22% 16% 2	2660
July	1st to 10th	Day	42% 7% 13% 20% 15% 3	4371
	11th to 20th	Day	27% 7% 16% 33% 16% 1	4365
	21st to end	Day	33% 8% 13% 23% 22% 2	4662
August	1st to 10th	Day	38% 8% 11% 26% 16% 1	4100
	11th to 20th	Day	34% 7% 11% 29% 18% 1	4083
	21st to end	Day	35% 8% 13% 29% 14% 1	4287
September	1st to 10th	Day	38% 7% 13% 26% 14% 2	2233
	11th to 20th	Day	33% 7% 13% 29% 16% 2	2090
	21st to end	Day	42% 5% 12% 24% 15%	2090
October	1st to 10th	Day	30% 4 8% 35% 21% 2	3480
	11th to 20th	Day	42% 5% 11% 28% 14%	3052
	21st to end	Day	50% 6% 12% 23% 8% 1	3081
November	1st to 10th	Day	46% 6% 13% 23% 11% 1	1699
	11th to 20th	Day	58% 6% 13% 17% 6% 1	1710
	21st to end	Day	61% 5% 14% 14% 5%	1710
December	1st to 10th	Day	70% 6% 9% 12% 2 1	1586
	11th to 20th	Day	66% 7% 12% 12% 2	1915
	21st to end	Day	77% 6% 7% 8% 2	2783
January	1st to 10th	Night	69% 5% 10% 11% 5% 1	4428
	11th to 20th	Night	77% 4 8% 7% 4	4440
	21st to end	Night	73% 6% 9% 9% 3	4884
February	1st to 10th	Night	63% 7% 10% 14% 6%	2443
	11th to 20th	Night	59% 6% 9% 17% 8% 1	2219
	21st to end	Night	60% 5% 11% 16% 7% 1	1884
March	1st to 10th	Night	47% 6% 12% 26% 8% 1	3733
	11th to 20th	Night	36% 6% 15% 24% 17% 2	3549
	21st to end	Night	53% 6% 11% 20% 8% 1	3736
April	1st to 10th	Night	48% 6% 9% 22% 14% 1	1900
	11th to 20th	Night	47% 4 9% 20% 17% 3	1796
	21st to end	Night	45% 4 13% 20% 14% 3	1710
May	1st to 10th	Night	44% 7% 12% 19% 15% 2	2840
	11th to 20th	Night	42% 5% 8% 23% 19% 2	2813
	21st to end	Night	41% 6% 10% 21% 20% 3	2764
June	1st to 10th	Night	36% 6% 11% 29% 17% 3	1520
	11th to 20th	Night	36% 6% 13% 24% 20% 1	1520
	21st to end	Night	33% 6% 14% 28% 16% 2	1520
July	1st to 10th	Night	37% 7% 12% 25% 12% 7%	2490
	11th to 20th	Night	25% 7% 14% 30% 23% 1	2482
	21st to end	Night	32% 8% 15% 21% 22% 2	2662
August	1st to 10th	Night	32% 5% 13% 30% 19% 1	2804
	11th to 20th	Night	31% 7% 11% 34% 16% 1	2812
	21st to end	Night	34% 8% 11% 30% 16% 2	3366
September	1st to 10th	Night	32% 6% 12% 30% 18% 2	1926
	11th to 20th	Night	29% 6% 11% 34% 19% 1	2090
	21st to end	Night	40% 6% 12% 27% 14% 1	2090
October	1st to 10th	Night	27% 4 10% 36% 21% 1	3480
	11th to 20th	Night	42% 5% 10% 24% 18%	3862
	21st to end	Night	43% 4 10% 29% 13%	4467
November	1st to 10th	Night	43% 6% 11% 25% 14% 1	2452
	11th to 20th	Night	55% 6% 13% 18% 6% 1	2470
	21st to end	Night	57% 5% 14% 19% 4	2470
December	1st to 10th	Night	68% 7% 10% 11% 4	2592
	11th to 20th	Night	66% 7% 13% 11% 4	3281
	21st to end	Night	74% 6% 10% 8% 3	4884

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	21% 18% 35% 18% 6% 2	270
	11th to 20th	Day	23% 16% 40% 16% 4 1	270
	21st to end	Day	30% 15% 30% 17% 7%	297
February	1st to 10th	Day	21% 23% 35% 17% 2 2	270
	11th to 20th	Day	21% 25% 37% 14% 2	270
	21st to end	Day	25% 27% 35% 10% 3	225
March	1st to 10th	Day	23% 20% 43% 10% 4	270
	11th to 20th	Day	22% 14% 33% 20% 10% 1	416
	21st to end	Day	27% 11% 32% 23% 5% 2	506
April	1st to 10th	Day	25% 17% 31% 20% 7% 1	460
	11th to 20th	Day	27% 21% 27% 14% 6% 4	452
	21st to end	Day	21% 12% 32% 22% 10% 2	460
May	1st to 10th	Day	23% 17% 27% 22% 8% 3	463
	11th to 20th	Day	18% 9% 30% 26% 11% 6%	487
	21st to end	Day	14% 9% 27% 25% 20% 5%	716
June	1st to 10th	Day	12% 8% 34% 28% 13% 4	680
	11th to 20th	Day	14% 9% 30% 29% 13% 5%	680
	21st to end	Day	13% 8% 31% 28% 15% 4	680
July	1st to 10th	Day	8% 6% 23% 29% 22% 12%	671
	11th to 20th	Day	10% 7% 25% 31% 17% 9%	668
	21st to end	Day	9% 5% 28% 29% 21% 8%	739
August	1st to 10th	Day	10% 4 23% 25% 24% 14%	496
	11th to 20th	Day	12% 3 19% 27% 26% 13%	479
	21st to end	Day	11% 6% 20% 29% 23% 11%	539
September	1st to 10th	Day	13% 7% 21% 26% 21% 12%	490
	11th to 20th	Day	9% 5% 19% 27% 27% 13%	490
	21st to end	Day	18% 11% 21% 27% 16% 7%	490
October	1st to 10th	Day	19% 10% 27% 24% 15% 5%	490
	11th to 20th	Day	23% 14% 31% 23% 7% 1	415
	21st to end	Day	29% 14% 36% 17% 4 1	330
November	1st to 10th	Day	21% 19% 31% 19% 9% 1	279
	11th to 20th	Day	21% 21% 39% 14% 4 1	270
	21st to end	Day	27% 16% 41% 13% 3	270
December	1st to 10th	Day	23% 23% 33% 15% 4 1	270
	11th to 20th	Day	23% 20% 40% 15% 2 1	270
	21st to end	Day	27% 23% 34% 13% 2 1	297
January	1st to 10th	Night	22% 15% 33% 23% 7% 1	950
	11th to 20th	Night	23% 14% 34% 23% 6%	950
	21st to end	Night	22% 9% 32% 31% 6%	1045
February	1st to 10th	Night	21% 14% 35% 27% 4	769
	11th to 20th	Night	20% 13% 37% 26% 5%	743
	21st to end	Night	24% 15% 39% 20% 3	628
March	1st to 10th	Night	19% 12% 37% 25% 8% 1	760
	11th to 20th	Night	18% 12% 37% 27% 5% 1	760
	21st to end	Night	23% 10% 33% 26% 7%	793
April	1st to 10th	Night	17% 12% 37% 27% 6% 1	570
	11th to 20th	Night	25% 9% 33% 26% 6% 1	563
	21st to end	Night	22% 9% 35% 26% 7% 1	570
May	1st to 10th	Night	18% 7% 34% 32% 8% 1	570
	11th to 20th	Night	20% 6% 32% 29% 12% 1	561
	21st to end	Night	14% 6% 24% 35% 19% 1	617
June	1st to 10th	Night	12% 5% 28% 38% 15% 1	570
	11th to 20th	Night	12% 6% 28% 35% 19%	570
	21st to end	Night	10% 5% 25% 41% 18% 1	570
July	1st to 10th	Night	9% 2 18% 42% 26% 3	555
	11th to 20th	Night	7% 3 22% 41% 24% 3	552
	21st to end	Night	8% 2 21% 43% 25% 2	624
August	1st to 10th	Night	8% 2 19% 43% 26% 2	567
	11th to 20th	Night	9% 2 18% 41% 26% 4	564
	21st to end	Night	11% 3 19% 37% 27% 3	627
September	1st to 10th	Night	11% 3 22% 35% 24% 4	596
	11th to 20th	Night	12% 4 19% 36% 26% 3	760
	21st to end	Night	16% 7% 23% 33% 17% 5%	760
October	1st to 10th	Night	18% 6% 24% 34% 15% 2	760
	11th to 20th	Night	23% 11% 28% 29% 9% 1	760
	21st to end	Night	27% 11% 33% 22% 7%	836
November	1st to 10th	Night	20% 10% 31% 28% 10%	755
	11th to 20th	Night	21% 14% 36% 22% 6% 1	760
	21st to end	Night	24% 11% 34% 27% 4	760
December	1st to 10th	Night	23% 14% 34% 23% 5%	882
	11th to 20th	Night	24% 13% 36% 21% 4 1	950
	21st to end	Night	30% 12% 36% 20% 2	1045

Page generated at 2024-11-01 22:47:45. Version ac07

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