Greensboro
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greensboro clear sky chart from 2005-11-06 to 2026-10-29.

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 6% 8% 43%	149275
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 45%	142802
Transparency	Day	39% 5% 12% 22% 18% 5%	152881
	Night	39% 4 10% 21% 20% 6%	147268
Seeing	Day	16% 8% 24% 25% 19% 9%	18096
	Night	16% 7% 25% 31% 18% 2	28141

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% 7% 2 4 3 2 3 3 4 4 52%	5258
	11th to 20th	Day	11% 6% 2 4 3 3 2 2 3 3 60%	5280
	21st to end	Day	17% 9% 3 6% 3 3 3 3 4 5% 45%	5780
February	1st to 10th	Day	13% 6% 2 7% 5% 3 3 4 6% 7% 43%	1890
	11th to 20th	Day	21% 7% 2 4 4 4 3 3 4 5% 43%	1901
	21st to end	Day	18% 7% 2 6% 4 4 4 3 6% 6% 40%	1848
March	1st to 10th	Day	19% 7% 2 6% 3 3 3 3 5% 7% 42%	5045
	11th to 20th	Day	9% 5% 2 5% 3 3 4 3 5% 7% 54%	5090
	21st to end	Day	15% 7% 2 6% 4 4 3 3 4 5% 46%	5586
April	1st to 10th	Day	11% 4 1 4 3 3 4 3 5% 8% 52%	2388
	11th to 20th	Day	11% 5% 2 5% 4 4 3 3 5% 7% 49%	2494
	21st to end	Day	13% 6% 2 6% 4 5% 5% 3 6% 6% 46%	2593
May	1st to 10th	Day	11% 7% 2 7% 4 5% 5% 4 7% 9% 38%	7616
	11th to 20th	Day	16% 6% 2 6% 4 4 5% 4 7% 7% 39%	7626
	21st to end	Day	15% 6% 2 7% 5% 5% 5% 4 6% 9% 35%	8391
June	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 8% 11% 41%	2730
	11th to 20th	Day	7% 6% 2 5% 5% 5% 5% 5% 7% 11% 42%	2730
	21st to end	Day	6% 5% 2 5% 5% 5% 5% 5% 8% 11% 42%	2730
July	1st to 10th	Day	7% 4 2 6% 4 5% 6% 5% 8% 11% 40%	7680
	11th to 20th	Day	9% 6% 2 7% 6% 6% 6% 5% 9% 13% 31%	7680
	21st to end	Day	13% 6% 3 7% 5% 5% 5% 4 7% 10% 34%	8340
August	1st to 10th	Day	16% 8% 3 8% 5% 6% 7% 5% 9% 12% 22%	6014
	11th to 20th	Day	6% 5% 2 6% 5% 5% 6% 5% 8% 13% 40%	5911
	21st to end	Day	7% 5% 2 6% 4 4 4 3 6% 9% 50%	6080
September	1st to 10th	Day	9% 5% 1 6% 4 5% 4 4 6% 7% 48%	2489
	11th to 20th	Day	12% 7% 2 6% 4 4 4 4 5% 8% 44%	2310
	21st to end	Day	21% 6% 2 7% 3 4 3 3 5% 6% 40%	2310
October	1st to 10th	Day	13% 7% 2 5% 3 3 3 2 4 6% 53%	2105
	11th to 20th	Day	12% 5% 2 4 3 3 2 2 4 4 57%	2100
	21st to end	Day	12% 4 2 5% 3 3 3 3 4 4 58%	2280
November	1st to 10th	Day	12% 5% 2 5% 4 4 3 3 4 5% 55%	2057
	11th to 20th	Day	13% 4 2 4 4 2 3 3 5% 7% 53%	2005
	21st to end	Day	12% 5% 2 5% 4 4 3 3 5% 6% 49%	1890
December	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 5% 6% 52%	3020
	11th to 20th	Day	17% 6% 2 5% 4 4 4 3 4 5% 46%	3463
	21st to end	Day	18% 6% 2 5% 3 4 4 3 5% 8% 43%	4565
January	1st to 10th	Night	13% 6% 2 4 3 3 3 2 4 6% 54%	7635
	11th to 20th	Night	12% 6% 2 5% 3 2 3 2 3 4 58%	7680
	21st to end	Night	17% 7% 2 5% 3 3 3 3 4 5% 46%	8401
February	1st to 10th	Night	15% 6% 2 6% 4 4 4 3 4 6% 45%	2730
	11th to 20th	Night	20% 7% 1 5% 4 3 3 3 4 5% 44%	2600
	21st to end	Night	15% 6% 3 5% 4 4 3 3 5% 6% 45%	1956
March	1st to 10th	Night	17% 7% 2 6% 4 4 3 3 4 5% 45%	5028
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 5% 6% 56%	5090
	21st to end	Night	14% 5% 1 5% 4 3 4 3 5% 7% 48%	5588
April	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 4 7% 50%	2231
	11th to 20th	Night	12% 5% 3 4 4 4 4 3 6% 7% 49%	2075
	21st to end	Night	13% 4 2 6% 5% 4 4 5% 6% 7% 46%	2043
May	1st to 10th	Night	12% 6% 3 6% 5% 5% 5% 4 7% 9% 40%	5237
	11th to 20th	Night	14% 6% 2 7% 4 4 3 3 5% 8% 44%	5234
	21st to end	Night	20% 7% 2 6% 4 4 4 4 6% 8% 36%	5761
June	1st to 10th	Night	9% 5% 2 6% 6% 5% 6% 5% 8% 10% 39%	1890
	11th to 20th	Night	9% 6% 2 6% 6% 4 5% 3 7% 11% 41%	1890
	21st to end	Night	7% 5% 1 5% 6% 5% 5% 5% 8% 11% 42%	1890
July	1st to 10th	Night	9% 6% 2 7% 5% 6% 6% 5% 8% 11% 34%	5278
	11th to 20th	Night	12% 7% 3 8% 7% 6% 7% 5% 8% 9% 28%	5277
	21st to end	Night	14% 7% 3 7% 5% 5% 5% 5% 7% 10% 32%	5736
August	1st to 10th	Night	20% 8% 3 9% 6% 6% 7% 5% 8% 10% 20%	4135
	11th to 20th	Night	7% 5% 2 6% 4 5% 5% 5% 9% 12% 40%	4095
	21st to end	Night	8% 6% 2 6% 4 5% 5% 4 5% 7% 47%	5036
September	1st to 10th	Night	8% 6% 2 5% 4 4 4 4 6% 8% 49%	2126
	11th to 20th	Night	12% 7% 2 6% 4 4 5% 3 5% 7% 44%	2310
	21st to end	Night	19% 7% 3 6% 4 4 4 4 5% 6% 38%	2310
October	1st to 10th	Night	14% 7% 2 5% 4 3 3 2 4 6% 50%	2514
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 4 5% 55%	2520
	21st to end	Night	13% 5% 1 4 3 3 3 2 3 5% 58%	2737
November	1st to 10th	Night	15% 5% 2 5% 3 3 3 2 4 4 53%	2461
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 4 5% 52%	2613
	21st to end	Night	13% 5% 2 5% 3 3 3 4 5% 6% 52%	2730
December	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 4 5% 52%	4380
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 4 5% 41%	4952
	21st to end	Night	19% 5% 1 4 3 3 4 3 5% 7% 47%	6633

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	37% 2 8% 20% 27% 6%	5259
	11th to 20th	Day	31% 2 3 14% 37% 13%	5280
	21st to end	Day	44% 2 3 23% 20% 7%	5780
February	1st to 10th	Day	40% 4 10% 21% 21% 5%	1890
	11th to 20th	Day	44% 3 7% 21% 19% 6%	1910
	21st to end	Day	44% 4 10% 16% 20% 6%	1848
March	1st to 10th	Day	43% 3 6% 17% 19% 11%	5045
	11th to 20th	Day	31% 3 7% 19% 23% 17%	5090
	21st to end	Day	41% 3 8% 22% 20% 6%	5586
April	1st to 10th	Day	29% 4 11% 24% 24% 7%	2388
	11th to 20th	Day	34% 4 11% 23% 21% 8%	2494
	21st to end	Day	38% 5% 11% 25% 17% 3	2593
May	1st to 10th	Day	42% 5% 15% 22% 14% 2	7651
	11th to 20th	Day	43% 5% 13% 24% 15% 1	7630
	21st to end	Day	45% 6% 12% 19% 15% 3	8405
June	1st to 10th	Day	35% 8% 16% 24% 15% 1	2730
	11th to 20th	Day	34% 7% 18% 24% 15% 2	2730
	21st to end	Day	33% 10% 17% 24% 14% 1	2730
July	1st to 10th	Day	38% 6% 19% 25% 10% 2	7615
	11th to 20th	Day	43% 8% 24% 18% 6% 1	7611
	21st to end	Day	45% 6% 16% 20% 12%	8156
August	1st to 10th	Day	54% 8% 20% 14% 3	6001
	11th to 20th	Day	35% 5% 27% 24% 8% 1	5950
	21st to end	Day	32% 5% 16% 32% 14% 1	6080
September	1st to 10th	Day	34% 7% 12% 22% 20% 4	2489
	11th to 20th	Day	39% 6% 11% 21% 21% 2	2310
	21st to end	Day	46% 5% 9% 20% 17% 4	2310
October	1st to 10th	Day	34% 3 6% 19% 28% 10%	3365
	11th to 20th	Day	22% 2 5% 21% 26% 25%	3340
	21st to end	Day	26% 2 7% 25% 24% 17%	3618
November	1st to 10th	Day	33% 3 7% 22% 26% 8%	2057
	11th to 20th	Day	32% 4 7% 24% 26% 6%	2005
	21st to end	Day	36% 4 7% 23% 27% 4	1890
December	1st to 10th	Day	35% 3 6% 21% 27% 7%	3020
	11th to 20th	Day	42% 3 9% 17% 23% 6%	3460
	21st to end	Day	41% 4 10% 27% 18% 2	4565
January	1st to 10th	Night	33% 3 10% 20% 25% 8%	7636
	11th to 20th	Night	33% 2 3 16% 36% 10%	7680
	21st to end	Night	42% 2 4 21% 24% 7%	8401
February	1st to 10th	Night	40% 4 9% 22% 21% 5%	2730
	11th to 20th	Night	44% 3 8% 18% 21% 7%	2602
	21st to end	Night	40% 4 9% 18% 22% 7%	1956
March	1st to 10th	Night	42% 4 5% 15% 24% 10%	5028
	11th to 20th	Night	31% 3 5% 17% 26% 18%	5090
	21st to end	Night	37% 3 7% 25% 22% 5%	5588
April	1st to 10th	Night	35% 4 11% 19% 25% 6%	2231
	11th to 20th	Night	34% 3 9% 23% 23% 7%	2075
	21st to end	Night	36% 5% 12% 25% 18% 4	2043
May	1st to 10th	Night	42% 4 15% 22% 15% 2	5264
	11th to 20th	Night	41% 5% 12% 24% 18% 1	5235
	21st to end	Night	46% 5% 12% 22% 12% 2	5771
June	1st to 10th	Night	37% 9% 15% 22% 15% 2	1890
	11th to 20th	Night	38% 6% 17% 22% 15% 2	1890
	21st to end	Night	33% 10% 17% 23% 14% 3	1890
July	1st to 10th	Night	43% 7% 17% 21% 10% 1	5235
	11th to 20th	Night	50% 11% 18% 12% 8% 1	5226
	21st to end	Night	47% 6% 17% 19% 11% 1	5606
August	1st to 10th	Night	59% 10% 14% 13% 5%	4124
	11th to 20th	Night	35% 6% 23% 28% 7% 1	4122
	21st to end	Night	36% 5% 12% 30% 16% 1	5036
September	1st to 10th	Night	33% 8% 13% 23% 18% 5%	2126
	11th to 20th	Night	40% 6% 11% 19% 22% 2	2310
	21st to end	Night	47% 7% 10% 17% 16% 4	2310
October	1st to 10th	Night	40% 2 6% 18% 26% 7%	4034
	11th to 20th	Night	24% 2 5% 22% 28% 19%	4019
	21st to end	Night	25% 2 5% 26% 25% 17%	4349
November	1st to 10th	Night	36% 3 7% 20% 25% 9%	2461
	11th to 20th	Night	35% 3 7% 18% 26% 11%	2613
	21st to end	Night	33% 3 7% 24% 26% 6%	2730
December	1st to 10th	Night	36% 3 6% 21% 30% 5%	4380
	11th to 20th	Night	48% 3 8% 17% 16% 8%	4954
	21st to end	Night	38% 3 12% 23% 22% 2	6633

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	25% 16% 38% 17% 5%	330
	11th to 20th	Day	23% 19% 37% 15% 5%	330
	21st to end	Day	19% 19% 40% 18% 3	363
February	1st to 10th	Day	16% 15% 45% 17% 6% 1	330
	11th to 20th	Day	34% 16% 37% 9% 4	330
	21st to end	Day	26% 16% 34% 19% 5%	391
March	1st to 10th	Day	21% 11% 34% 25% 8% 1	540
	11th to 20th	Day	18% 14% 41% 22% 5% 1	540
	21st to end	Day	19% 14% 38% 21% 6% 1	594
April	1st to 10th	Day	18% 14% 33% 23% 11% 2	540
	11th to 20th	Day	12% 14% 30% 27% 14% 4	532
	21st to end	Day	16% 10% 26% 29% 16% 2	540
May	1st to 10th	Day	15% 13% 31% 23% 13% 5%	543
	11th to 20th	Day	16% 5% 25% 24% 22% 8%	567
	21st to end	Day	18% 5% 17% 26% 21% 13%	617
June	1st to 10th	Day	11% 2 18% 31% 25% 12%	570
	11th to 20th	Day	9% 4 19% 27% 24% 17%	570
	21st to end	Day	7% 1 15% 30% 35% 12%	570
July	1st to 10th	Day	10% 1 8% 24% 37% 20%	565
	11th to 20th	Day	6% 1 10% 24% 36% 23%	564
	21st to end	Day	10% 1 9% 26% 34% 19%	620
August	1st to 10th	Day	17% 1 12% 26% 27% 16%	566
	11th to 20th	Day	10% 2 11% 27% 30% 21%	559
	21st to end	Day	10% 1 12% 24% 30% 23%	627
September	1st to 10th	Day	12% 2 11% 24% 29% 21%	570
	11th to 20th	Day	16% 2 11% 25% 27% 19%	570
	21st to end	Day	24% 4 18% 27% 20% 7%	570
October	1st to 10th	Day	18% 5% 17% 29% 22% 10%	570
	11th to 20th	Day	14% 7% 23% 29% 23% 5%	570
	21st to end	Day	15% 8% 24% 29% 19% 5%	615
November	1st to 10th	Day	18% 5% 30% 27% 15% 4	535
	11th to 20th	Day	15% 13% 34% 23% 13% 2	445
	21st to end	Day	11% 18% 31% 24% 14% 2	330
December	1st to 10th	Day	22% 14% 37% 22% 5% 1	330
	11th to 20th	Day	18% 12% 34% 26% 9% 2	330
	21st to end	Day	23% 15% 29% 22% 9% 2	363
January	1st to 10th	Night	20% 14% 36% 25% 5%	840
	11th to 20th	Night	19% 12% 38% 27% 4	840
	21st to end	Night	19% 11% 42% 27% 2	924
February	1st to 10th	Night	19% 10% 38% 30% 3	840
	11th to 20th	Night	25% 15% 38% 20% 1	823
	21st to end	Night	19% 15% 36% 26% 4	692
March	1st to 10th	Night	18% 13% 35% 30% 5%	840
	11th to 20th	Night	18% 14% 36% 25% 7%	840
	21st to end	Night	17% 11% 36% 30% 6%	924
April	1st to 10th	Night	16% 13% 33% 30% 8%	840
	11th to 20th	Night	14% 9% 34% 30% 12% 1	831
	21st to end	Night	14% 7% 29% 39% 11% 1	783
May	1st to 10th	Night	13% 8% 31% 33% 14%	630
	11th to 20th	Night	14% 5% 22% 38% 19% 2	621
	21st to end	Night	17% 2 14% 33% 30% 4	683
June	1st to 10th	Night	11% 2 17% 40% 29% 2	630
	11th to 20th	Night	11% 3 14% 33% 33% 6%	630
	21st to end	Night	9% 1 12% 37% 38% 3	630
July	1st to 10th	Night	10% 1 9% 30% 43% 6%	615
	11th to 20th	Night	8% 1 5% 31% 46% 8%	612
	21st to end	Night	10% 1 9% 35% 39% 7%	690
August	1st to 10th	Night	17% 1 7% 33% 37% 5%	627
	11th to 20th	Night	11% 1 9% 31% 41% 7%	624
	21st to end	Night	11% 1 9% 33% 38% 8%	915
September	1st to 10th	Night	11% 1 10% 35% 36% 7%	840
	11th to 20th	Night	16% 3 12% 29% 35% 5%	840
	21st to end	Night	23% 3 18% 31% 25% 1	840
October	1st to 10th	Night	18% 2 16% 31% 27% 6%	840
	11th to 20th	Night	17% 6% 24% 33% 18% 2	840
	21st to end	Night	15% 7% 25% 32% 19% 2	913
November	1st to 10th	Night	16% 7% 24% 35% 16% 2	820
	11th to 20th	Night	15% 10% 30% 33% 11%	840
	21st to end	Night	15% 8% 32% 33% 12% 1	840
December	1st to 10th	Night	20% 9% 34% 30% 6%	840
	11th to 20th	Night	18% 7% 35% 32% 7%	840
	21st to end	Night	23% 9% 28% 33% 6%	924

Page generated at 2026-10-26 04:37:50. Version ac07

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