Norfolk(NE)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Norfolk(NE) clear sky chart from 2005-11-06 to 2026-02-16.

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	11% 7% 3 7% 4 4 4 3 5% 7% 45%	130794
	Night	9% 7% 3 7% 4 4 4 3 5% 7% 47%	130318
Transparency	Day	39% 4 13% 26% 16% 3	134402
	Night	36% 4 12% 27% 18% 3	134779
Seeing	Day	15% 10% 32% 29% 13% 2	17547
	Night	13% 10% 35% 32% 9% 1	27588

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	10% 13% 5% 14% 8% 6% 4 3 3 4 30%	4722
	11th to 20th	Day	4 9% 4 10% 7% 6% 6% 4 6% 6% 36%	5226
	21st to end	Day	4 9% 4 12% 5% 4 4 4 5% 6% 43%	5812
February	1st to 10th	Day	9% 12% 4 9% 6% 6% 5% 4 5% 7% 32%	1890
	11th to 20th	Day	7% 11% 5% 7% 5% 4 4 3 5% 6% 42%	1893
	21st to end	Day	9% 10% 3 8% 4 4 5% 3 4 7% 43%	1650
March	1st to 10th	Day	12% 8% 3 6% 3 3 3 3 4 5% 51%	4715
	11th to 20th	Day	9% 8% 2 5% 3 3 3 3 5% 7% 51%	4980
	21st to end	Day	20% 10% 3 10% 5% 5% 5% 4 5% 7% 26%	5462
April	1st to 10th	Day	13% 8% 3 7% 4 4 4 3 5% 7% 42%	2234
	11th to 20th	Day	17% 8% 2 6% 4 3 3 4 6% 7% 40%	2572
	21st to end	Day	20% 9% 3 6% 4 3 3 4 5% 6% 38%	2600
May	1st to 10th	Day	11% 7% 3 7% 4 4 4 3 5% 7% 46%	5862
	11th to 20th	Day	13% 6% 2 5% 3 3 4 3 5% 6% 51%	5862
	21st to end	Day	19% 7% 3 7% 4 5% 4 3 4 6% 37%	6434
June	1st to 10th	Day	9% 5% 2 5% 4 3 4 4 5% 10% 49%	2810
	11th to 20th	Day	10% 5% 2 6% 3 4 4 4 7% 8% 46%	3000
	21st to end	Day	7% 5% 1 5% 4 4 4 4 6% 9% 51%	2942
July	1st to 10th	Day	10% 4 2 5% 3 4 5% 3 7% 9% 48%	6340
	11th to 20th	Day	9% 5% 2 6% 4 4 4 3 6% 7% 50%	6124
	21st to end	Day	5% 5% 2 5% 5% 4 5% 4 6% 9% 49%	6422
August	1st to 10th	Day	7% 5% 2 7% 4 5% 5% 4 6% 9% 45%	4234
	11th to 20th	Day	16% 7% 3 6% 4 4 4 3 5% 7% 41%	4171
	21st to end	Day	8% 4 2 5% 4 4 4 3 5% 8% 53%	4675
September	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 4 7% 51%	2266
	11th to 20th	Day	8% 5% 1 6% 3 3 3 3 5% 7% 55%	2200
	21st to end	Day	10% 4 1 4 3 3 3 2 5% 6% 58%	2200
October	1st to 10th	Day	15% 5% 2 5% 3 3 3 3 4 6% 52%	2101
	11th to 20th	Day	11% 5% 2 4 3 3 3 2 4 6% 56%	2000
	21st to end	Day	15% 7% 2 5% 3 3 3 2 4 6% 50%	2115
November	1st to 10th	Day	8% 7% 3 6% 4 4 3 3 6% 6% 51%	1853
	11th to 20th	Day	9% 7% 1 7% 5% 3 4 4 5% 7% 49%	1890
	21st to end	Day	11% 10% 3 7% 4 3 3 3 5% 7% 44%	1694
December	1st to 10th	Day	5% 6% 3 7% 4 5% 4 3 4 6% 52%	2690
	11th to 20th	Day	6% 9% 4 9% 5% 5% 5% 3 5% 7% 40%	3088
	21st to end	Day	13% 10% 3 14% 4 4 3 3 5% 6% 35%	4065
January	1st to 10th	Night	9% 11% 3 12% 7% 6% 6% 4 6% 6% 30%	8201
	11th to 20th	Night	3 8% 3 10% 6% 6% 7% 5% 7% 7% 39%	7757
	21st to end	Night	4 8% 5% 12% 4 4 4 3 5% 6% 45%	8402
February	1st to 10th	Night	10% 10% 3 9% 6% 4 4 3 5% 5% 40%	2730
	11th to 20th	Night	8% 10% 4 7% 4 5% 5% 4 6% 6% 42%	2523
	21st to end	Night	9% 6% 3 6% 5% 4 5% 3 5% 6% 49%	1980
March	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 4 6% 51%	5148
	11th to 20th	Night	11% 6% 2 5% 3 3 3 3 4 7% 53%	4980
	21st to end	Night	14% 9% 3 7% 4 5% 5% 4 5% 8% 37%	5467
April	1st to 10th	Night	13% 7% 3 6% 4 4 4 4 5% 6% 45%	2162
	11th to 20th	Night	12% 8% 2 7% 4 4 4 3 4 7% 45%	1779
	21st to end	Night	15% 8% 2 6% 3 4 3 4 6% 7% 42%	1800
May	1st to 10th	Night	13% 4 1 5% 4 3 3 3 4 7% 52%	4053
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 7% 52%	4053
	21st to end	Night	16% 6% 2 5% 4 4 3 3 5% 8% 42%	4443
June	1st to 10th	Night	7% 3 2 3 3 3 5% 4 7% 8% 56%	1579
	11th to 20th	Night	8% 4 2 6% 3 4 3 3 5% 7% 56%	1400
	21st to end	Night	4 4 2 4 3 3 4 3 6% 8% 59%	1450
July	1st to 10th	Night	9% 5% 2 5% 3 4 3 3 5% 8% 55%	3638
	11th to 20th	Night	9% 5% 2 5% 3 4 3 4 5% 8% 53%	3850
	21st to end	Night	3 4 2 4 4 3 4 4 6% 10% 56%	4449
August	1st to 10th	Night	5% 4 2 6% 4 4 5% 4 7% 10% 50%	2926
	11th to 20th	Night	11% 6% 1 5% 3 3 4 3 5% 8% 50%	2888
	21st to end	Night	5% 3 2 5% 4 4 4 3 5% 9% 55%	3234
September	1st to 10th	Night	8% 3 1 5% 3 3 3 3 5% 6% 61%	2129
	11th to 20th	Night	7% 4 1 4 3 3 4 3 5% 6% 59%	2200
	21st to end	Night	8% 4 2 5% 3 3 3 2 4 6% 60%	2200
October	1st to 10th	Night	15% 5% 2 4 3 3 3 3 4 6% 53%	2278
	11th to 20th	Night	12% 5% 2 5% 3 2 3 3 4 5% 56%	2400
	21st to end	Night	14% 5% 1 5% 3 3 3 2 4 6% 53%	2723
November	1st to 10th	Night	8% 6% 2 4 3 3 3 3 5% 6% 58%	2665
	11th to 20th	Night	8% 7% 2 6% 4 4 3 3 5% 6% 52%	2730
	21st to end	Night	9% 8% 2 5% 4 3 3 3 5% 7% 50%	2923
December	1st to 10th	Night	4 6% 3 7% 5% 4 4 3 5% 7% 52%	4720
	11th to 20th	Night	9% 8% 3 7% 4 4 4 4 6% 7% 44%	5339
	21st to end	Night	14% 13% 4 11% 4 4 4 3 4 5% 34%	7119

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	59% 3 11% 16% 10% 1	4723
	11th to 20th	Day	48% 2 14% 18% 17% 2	5226
	21st to end	Day	42% 3 16% 23% 15% 1	5812
February	1st to 10th	Day	50% 5% 15% 18% 10% 1	1890
	11th to 20th	Day	43% 5% 11% 23% 15% 3	1902
	21st to end	Day	42% 5% 12% 24% 14% 4	1650
March	1st to 10th	Day	37% 3 8% 28% 20% 4	4715
	11th to 20th	Day	34% 3 7% 29% 24% 3	4980
	21st to end	Day	57% 4 17% 15% 4 2	5464
April	1st to 10th	Day	43% 4 12% 26% 14% 2	2234
	11th to 20th	Day	43% 4 12% 23% 14% 3	2572
	21st to end	Day	46% 5% 11% 26% 12%	2600
May	1st to 10th	Day	37% 4 11% 25% 20% 2	5900
	11th to 20th	Day	35% 4 12% 23% 18% 9%	5866
	21st to end	Day	48% 4 9% 24% 14% 1	6447
June	1st to 10th	Day	31% 7% 17% 31% 12% 2	2810
	11th to 20th	Day	34% 6% 15% 26% 16% 2	3000
	21st to end	Day	29% 6% 16% 31% 14% 4	2942
July	1st to 10th	Day	35% 3 14% 33% 15% 1	6271
	11th to 20th	Day	35% 2 12% 33% 15% 2	6049
	21st to end	Day	31% 3 18% 28% 17% 2	6240
August	1st to 10th	Day	35% 4 14% 29% 13% 4	4220
	11th to 20th	Day	44% 4 12% 26% 13% 1	4210
	21st to end	Day	31% 5% 14% 25% 20% 5%	4674
September	1st to 10th	Day	34% 4 12% 27% 18% 5%	2266
	11th to 20th	Day	30% 4 13% 35% 17% 2	2200
	21st to end	Day	27% 3 9% 33% 26% 2	2200
October	1st to 10th	Day	23% 2 5% 22% 43% 5%	3426
	11th to 20th	Day	24% 2 15% 32% 21% 7%	3240
	21st to end	Day	34% 2 11% 29% 21% 3	3396
November	1st to 10th	Day	33% 4 15% 26% 21% 2	1853
	11th to 20th	Day	36% 5% 13% 26% 18% 2	1890
	21st to end	Day	40% 4 12% 27% 14% 2	1694
December	1st to 10th	Day	34% 2 18% 28% 16% 2	2690
	11th to 20th	Day	43% 3 19% 23% 11% 1	3085
	21st to end	Day	51% 4 10% 25% 10% 1	4065
January	1st to 10th	Night	53% 4 12% 18% 12% 1	8202
	11th to 20th	Night	44% 2 12% 25% 16% 1	7757
	21st to end	Night	41% 3 12% 23% 19% 1	8402
February	1st to 10th	Night	46% 4 13% 23% 12% 2	2730
	11th to 20th	Night	41% 5% 13% 23% 14% 4	2524
	21st to end	Night	35% 4 12% 26% 18% 4	1980
March	1st to 10th	Night	34% 3 8% 29% 23% 3	5148
	11th to 20th	Night	32% 3 6% 26% 28% 5%	4980
	21st to end	Night	46% 5% 17% 25% 7% 1	5467
April	1st to 10th	Night	39% 5% 10% 27% 17% 1	2162
	11th to 20th	Night	39% 5% 9% 28% 17% 2	1779
	21st to end	Night	39% 6% 13% 26% 15% 2	1800
May	1st to 10th	Night	33% 4 10% 29% 23% 1	4080
	11th to 20th	Night	33% 4 13% 19% 23% 8%	4054
	21st to end	Night	41% 4 13% 26% 14% 2	4452
June	1st to 10th	Night	24% 7% 17% 33% 15% 4	1579
	11th to 20th	Night	29% 4 15% 28% 19% 5%	1400
	21st to end	Night	23% 5% 15% 35% 18% 3	1450
July	1st to 10th	Night	30% 3 13% 39% 14% 2	3600
	11th to 20th	Night	32% 4 14% 32% 16% 3	3805
	21st to end	Night	25% 4 22% 29% 18% 2	4320
August	1st to 10th	Night	30% 4 16% 33% 15% 3	2916
	11th to 20th	Night	35% 4 15% 28% 16% 2	2915
	21st to end	Night	29% 4 14% 25% 21% 6%	3234
September	1st to 10th	Night	25% 5% 12% 30% 23% 6%	2129
	11th to 20th	Night	26% 4 13% 33% 21% 2	2200
	21st to end	Night	27% 4 8% 30% 26% 5%	2200
October	1st to 10th	Night	21% 2 5% 18% 49% 5%	3720
	11th to 20th	Night	23% 2 10% 30% 28% 6%	3899
	21st to end	Night	33% 2 11% 33% 19% 2	4397
November	1st to 10th	Night	28% 4 16% 26% 23% 4	2665
	11th to 20th	Night	33% 3 13% 27% 20% 4	2730
	21st to end	Night	35% 4 13% 29% 17% 2	2923
December	1st to 10th	Night	33% 2 15% 33% 16% 1	4720
	11th to 20th	Night	39% 4 14% 31% 12%	5341
	21st to end	Night	53% 3 10% 24% 9% 1	7119

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	18% 12% 36% 22% 10% 2	330
	11th to 20th	Day	17% 18% 33% 24% 7% 1	330
	21st to end	Day	12% 9% 46% 25% 7% 1	363
February	1st to 10th	Day	15% 18% 41% 23% 3	330
	11th to 20th	Day	13% 14% 41% 25% 6% 1	315
	21st to end	Day	15% 18% 40% 21% 5%	249
March	1st to 10th	Day	15% 18% 44% 18% 5% 1	300
	11th to 20th	Day	19% 14% 39% 20% 8% 1	300
	21st to end	Day	29% 14% 33% 17% 6% 1	330
April	1st to 10th	Day	20% 19% 40% 18% 4	334
	11th to 20th	Day	21% 17% 33% 22% 7%	690
	21st to end	Day	25% 15% 30% 21% 8% 2	700
May	1st to 10th	Day	19% 12% 34% 23% 11% 2	703
	11th to 20th	Day	19% 12% 29% 24% 14% 2	725
	21st to end	Day	19% 8% 31% 28% 11% 2	789
June	1st to 10th	Day	8% 8% 27% 33% 20% 4	730
	11th to 20th	Day	12% 5% 32% 33% 15% 3	730
	21st to end	Day	9% 8% 33% 32% 16% 2	730
July	1st to 10th	Day	10% 4 20% 34% 27% 6%	721
	11th to 20th	Day	6% 2 26% 42% 19% 5%	718
	21st to end	Day	7% 2 24% 43% 21% 4	794
August	1st to 10th	Day	10% 4 21% 42% 21% 2	726
	11th to 20th	Day	13% 3 22% 37% 20% 4	715
	21st to end	Day	11% 3 26% 36% 21% 3	803
September	1st to 10th	Day	13% 4 28% 38% 13% 4	396
	11th to 20th	Day	8% 6% 39% 29% 14% 5%	330
	21st to end	Day	14% 11% 29% 29% 13% 5%	330
October	1st to 10th	Day	20% 8% 27% 28% 14% 3	330
	11th to 20th	Day	16% 13% 38% 22% 8% 2	330
	21st to end	Day	20% 15% 36% 21% 7% 1	363
November	1st to 10th	Day	15% 15% 35% 25% 7% 3	330
	11th to 20th	Day	13% 16% 44% 21% 6%	330
	21st to end	Day	19% 18% 33% 22% 8% 1	330
December	1st to 10th	Day	12% 12% 43% 27% 5% 1	330
	11th to 20th	Day	17% 15% 37% 24% 7%	330
	21st to end	Day	17% 16% 41% 20% 5% 1	363
January	1st to 10th	Night	13% 14% 38% 28% 6% 1	1050
	11th to 20th	Night	12% 15% 39% 28% 6% 1	1050
	21st to end	Night	14% 10% 44% 27% 5%	1155
February	1st to 10th	Night	14% 13% 41% 28% 4	1050
	11th to 20th	Night	13% 11% 43% 28% 5%	929
	21st to end	Night	12% 12% 42% 28% 6%	660
March	1st to 10th	Night	15% 14% 40% 27% 5%	704
	11th to 20th	Night	16% 12% 39% 28% 5%	600
	21st to end	Night	20% 8% 41% 25% 6%	660
April	1st to 10th	Night	20% 14% 38% 25% 4	600
	11th to 20th	Night	17% 14% 39% 26% 5%	593
	21st to end	Night	18% 12% 35% 26% 8%	600
May	1st to 10th	Night	17% 9% 34% 30% 10%	600
	11th to 20th	Night	15% 8% 32% 34% 10% 1	591
	21st to end	Night	18% 6% 32% 33% 10% 1	650
June	1st to 10th	Night	8% 4 26% 48% 14% 1	600
	11th to 20th	Night	9% 6% 33% 39% 12% 1	600
	21st to end	Night	7% 6% 29% 46% 13%	600
July	1st to 10th	Night	7% 4 19% 45% 25% 1	585
	11th to 20th	Night	5% 1 23% 51% 19% 1	582
	21st to end	Night	4 2 20% 56% 18%	657
August	1st to 10th	Night	5% 3 22% 48% 21% 1	597
	11th to 20th	Night	9% 3 21% 46% 20%	594
	21st to end	Night	7% 3 28% 43% 18% 1	660
September	1st to 10th	Night	9% 4 27% 42% 17% 2	600
	11th to 20th	Night	9% 6% 32% 39% 13% 2	600
	21st to end	Night	11% 8% 32% 33% 15% 1	600
October	1st to 10th	Night	17% 8% 34% 31% 10% 1	678
	11th to 20th	Night	14% 15% 37% 27% 7%	800
	21st to end	Night	17% 12% 32% 29% 9%	963
November	1st to 10th	Night	12% 11% 39% 31% 7% 1	1025
	11th to 20th	Night	13% 12% 40% 30% 6%	1050
	21st to end	Night	14% 11% 36% 29% 9%	1050
December	1st to 10th	Night	11% 12% 44% 27% 5% 1	1050
	11th to 20th	Night	16% 11% 37% 28% 7%	1050
	21st to end	Night	18% 13% 39% 24% 5%	1155

Page generated at 2026-02-13 00:42:15. Version ac07

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