South Lake Norman
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Lake Norman 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	14% 6% 2 5% 4 4 4 4 6% 8% 43%	101193
	Night	15% 6% 2 6% 4 4 4 4 6% 7% 43%	97772
Transparency	Day	37% 6% 12% 21% 18% 5%	104883
	Night	39% 6% 11% 19% 20% 6%	102221
Seeing	Day	16% 7% 21% 24% 21% 11%	15269
	Night	16% 7% 23% 31% 20% 3	25332

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	18% 5% 1 5% 3 3 3 2 4 6% 51%	2836
	11th to 20th	Day	14% 7% 2 5% 3 3 2 2 4 4 53%	2840
	21st to end	Day	25% 6% 2 5% 3 3 3 3 4 5% 42%	3124
February	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 6% 6% 42%	1710
	11th to 20th	Day	20% 6% 2 5% 3 3 2 3 4 5% 46%	1814
	21st to end	Day	19% 8% 3 6% 4 3 4 3 3 6% 40%	1614
March	1st to 10th	Day	25% 6% 2 5% 3 3 3 3 4 6% 40%	3435
	11th to 20th	Day	11% 5% 2 5% 3 3 3 3 5% 7% 54%	3480
	21st to end	Day	21% 7% 2 5% 4 3 3 3 4 6% 43%	3815
April	1st to 10th	Day	10% 5% 2 4 3 4 4 3 6% 8% 51%	2090
	11th to 20th	Day	15% 4 2 5% 3 3 4 3 5% 6% 49%	2252
	21st to end	Day	14% 6% 2 4 4 3 4 3 5% 6% 49%	2432
May	1st to 10th	Day	11% 7% 2 6% 6% 5% 6% 5% 7% 9% 36%	4082
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 6% 8% 37%	4081
	21st to end	Day	8% 4 2 5% 4 4 5% 4 6% 9% 48%	4476
June	1st to 10th	Day	9% 6% 2 7% 4 5% 5% 5% 7% 11% 40%	2470
	11th to 20th	Day	9% 5% 2 5% 4 5% 6% 5% 7% 10% 43%	2470
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 8% 11% 40%	2470
July	1st to 10th	Day	8% 6% 3 7% 5% 5% 6% 5% 9% 11% 37%	4120
	11th to 20th	Day	7% 6% 3 6% 6% 6% 6% 5% 8% 11% 36%	4120
	21st to end	Day	12% 9% 4 7% 6% 6% 6% 5% 9% 10% 26%	4466
August	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 5% 7% 10% 28%	4104
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 8% 11% 37%	4044
	21st to end	Day	6% 4 1 4 4 4 4 4 7% 9% 53%	4252
September	1st to 10th	Day	9% 5% 2 5% 5% 5% 6% 5% 8% 9% 44%	2123
	11th to 20th	Day	13% 6% 2 7% 4 3 4 4 6% 9% 43%	2090
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 6% 39%	2090
October	1st to 10th	Day	14% 5% 2 4 3 3 3 2 4 6% 55%	1971
	11th to 20th	Day	13% 5% 2 4 3 2 3 3 3 5% 58%	1900
	21st to end	Day	14% 5% 1 4 3 2 2 3 3 4 57%	2090
November	1st to 10th	Day	13% 5% 2 5% 3 3 3 2 4 5% 55%	1887
	11th to 20th	Day	13% 6% 1 4 2 3 3 3 5% 7% 53%	1748
	21st to end	Day	15% 5% 2 4 3 4 3 3 5% 6% 50%	1710
December	1st to 10th	Day	19% 7% 3 5% 3 4 4 3 5% 6% 41%	1710
	11th to 20th	Day	15% 5% 2 5% 3 2 3 3 5% 6% 52%	2153
	21st to end	Day	18% 6% 2 5% 3 4 4 3 6% 8% 41%	3124
January	1st to 10th	Night	17% 5% 2 5% 4 3 4 3 5% 5% 49%	4109
	11th to 20th	Night	12% 6% 2 5% 4 4 4 3 4 5% 48%	4120
	21st to end	Night	24% 7% 2 4 3 3 2 2 4 4 45%	4532
February	1st to 10th	Night	16% 6% 2 5% 3 4 3 3 5% 6% 46%	2470
	11th to 20th	Night	21% 6% 2 5% 4 4 3 2 4 6% 44%	2247
	21st to end	Night	16% 7% 2 5% 4 3 3 4 6% 6% 44%	1837
March	1st to 10th	Night	22% 8% 3 6% 4 3 4 3 4 5% 38%	3418
	11th to 20th	Night	12% 4 2 5% 4 3 4 3 5% 8% 52%	3480
	21st to end	Night	20% 5% 2 5% 3 4 3 4 5% 5% 45%	3817
April	1st to 10th	Night	12% 6% 2 4 4 4 4 3 5% 7% 48%	2090
	11th to 20th	Night	14% 5% 2 5% 4 3 3 3 5% 7% 51%	1875
	21st to end	Night	12% 5% 2 5% 5% 4 4 3 6% 7% 48%	1762
May	1st to 10th	Night	14% 8% 3 7% 5% 4 4 3 5% 8% 40%	2813
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 3 6% 6% 38%	2812
	21st to end	Night	9% 5% 2 6% 4 5% 5% 4 7% 11% 43%	3079
June	1st to 10th	Night	9% 6% 2 6% 5% 6% 5% 6% 8% 10% 36%	1710
	11th to 20th	Night	11% 6% 2 6% 5% 6% 5% 5% 8% 11% 36%	1710
	21st to end	Night	7% 5% 2 6% 6% 6% 6% 6% 8% 10% 37%	1710
July	1st to 10th	Night	9% 8% 3 9% 6% 5% 7% 5% 8% 10% 30%	2840
	11th to 20th	Night	9% 6% 2 6% 6% 5% 6% 5% 9% 14% 34%	2840
	21st to end	Night	14% 9% 4 9% 7% 6% 6% 5% 9% 10% 22%	3087
August	1st to 10th	Night	20% 8% 4 8% 5% 5% 6% 4 7% 9% 24%	2825
	11th to 20th	Night	10% 7% 3 8% 5% 6% 6% 6% 8% 9% 32%	2785
	21st to end	Night	5% 4 2 6% 4 5% 5% 4 7% 10% 49%	3370
September	1st to 10th	Night	9% 6% 2 6% 4 5% 5% 4 6% 8% 44%	2052
	11th to 20th	Night	15% 7% 3 7% 5% 4 5% 4 6% 6% 38%	2090
	21st to end	Night	18% 6% 2 6% 5% 4 5% 3 6% 6% 39%	2090
October	1st to 10th	Night	15% 5% 2 5% 3 3 3 3 5% 6% 50%	2209
	11th to 20th	Night	14% 6% 1 3 3 3 3 3 4 5% 54%	2280
	21st to end	Night	12% 5% 1 5% 3 3 3 2 4 3 58%	2508
November	1st to 10th	Night	14% 6% 2 5% 3 3 2 2 4 5% 54%	2264
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 4 5% 52%	2427
	21st to end	Night	14% 4 2 4 3 4 4 3 6% 7% 50%	2470
December	1st to 10th	Night	20% 7% 2 7% 4 3 4 3 4 5% 42%	2470
	11th to 20th	Night	17% 6% 2 4 3 3 3 2 4 5% 51%	3042
	21st to end	Night	20% 5% 2 5% 4 4 4 4 6% 6% 43%	4532

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 5% 27% 22% 7%	2837
	11th to 20th	Day	36% 3 6% 17% 33% 6%	2840
	21st to end	Day	45% 3 5% 17% 24% 5%	3124
February	1st to 10th	Day	39% 5% 10% 22% 19% 5%	1710
	11th to 20th	Day	41% 4 8% 20% 21% 6%	1824
	21st to end	Day	46% 5% 7% 17% 19% 7%	1614
March	1st to 10th	Day	46% 4 7% 16% 17% 9%	3435
	11th to 20th	Day	31% 5% 8% 18% 26% 12%	3480
	21st to end	Day	44% 4 6% 22% 21% 3	3815
April	1st to 10th	Day	30% 4 12% 22% 25% 6%	2090
	11th to 20th	Day	35% 4 10% 19% 22% 9%	2252
	21st to end	Day	35% 6% 11% 25% 19% 4	2432
May	1st to 10th	Day	40% 9% 17% 20% 12% 2	4120
	11th to 20th	Day	44% 7% 13% 21% 14% 1	4085
	21st to end	Day	30% 8% 17% 23% 19% 4	4489
June	1st to 10th	Day	37% 8% 16% 26% 13% 1	2470
	11th to 20th	Day	34% 9% 18% 22% 15% 1	2470
	21st to end	Day	34% 10% 18% 22% 14% 2	2470
July	1st to 10th	Day	36% 12% 19% 19% 11% 2	4055
	11th to 20th	Day	39% 11% 25% 20% 5%	4051
	21st to end	Day	49% 11% 15% 18% 6% 1	4324
August	1st to 10th	Day	48% 10% 18% 20% 5%	4091
	11th to 20th	Day	37% 10% 20% 21% 10% 2	4083
	21st to end	Day	26% 8% 15% 35% 14% 2	4252
September	1st to 10th	Day	33% 10% 14% 21% 19% 4	2123
	11th to 20th	Day	37% 8% 13% 18% 20% 3	2090
	21st to end	Day	45% 6% 9% 19% 17% 4	2090
October	1st to 10th	Day	29% 5% 6% 21% 29% 11%	3270
	11th to 20th	Day	20% 3 5% 19% 27% 25%	3140
	21st to end	Day	26% 3 5% 26% 23% 16%	3428
November	1st to 10th	Day	33% 3 6% 20% 29% 8%	1887
	11th to 20th	Day	32% 3 8% 24% 27% 7%	1748
	21st to end	Day	35% 4 8% 22% 24% 7%	1710
December	1st to 10th	Day	44% 4 8% 21% 17% 5%	1710
	11th to 20th	Day	34% 3 7% 21% 25% 10%	2150
	21st to end	Day	41% 4 9% 24% 19% 3	3124
January	1st to 10th	Night	38% 3 8% 18% 27% 7%	4109
	11th to 20th	Night	37% 4 7% 15% 31% 6%	4120
	21st to end	Night	44% 2 5% 17% 25% 7%	4532
February	1st to 10th	Night	39% 4 10% 20% 21% 5%	2470
	11th to 20th	Night	44% 4 7% 16% 22% 7%	2248
	21st to end	Night	40% 4 10% 18% 21% 7%	1837
March	1st to 10th	Night	48% 5% 9% 14% 17% 6%	3418
	11th to 20th	Night	31% 5% 7% 17% 24% 16%	3480
	21st to end	Night	41% 5% 7% 21% 19% 7%	3817
April	1st to 10th	Night	35% 4 10% 20% 24% 6%	2090
	11th to 20th	Night	33% 5% 9% 21% 22% 9%	1875
	21st to end	Night	36% 5% 12% 22% 21% 4	1762
May	1st to 10th	Night	42% 6% 15% 23% 12% 2	2840
	11th to 20th	Night	45% 8% 11% 21% 14% 1	2813
	21st to end	Night	31% 8% 16% 28% 15% 1	3087
June	1st to 10th	Night	39% 10% 16% 21% 12% 2	1710
	11th to 20th	Night	40% 9% 17% 21% 11% 2	1710
	21st to end	Night	37% 12% 16% 19% 12% 4	1710
July	1st to 10th	Night	46% 10% 17% 14% 10% 2	2795
	11th to 20th	Night	37% 13% 26% 20% 4 1	2786
	21st to end	Night	53% 13% 14% 15% 5%	2988
August	1st to 10th	Night	54% 9% 18% 14% 4	2814
	11th to 20th	Night	43% 10% 22% 16% 9% 1	2812
	21st to end	Night	29% 8% 13% 29% 19% 2	3370
September	1st to 10th	Night	36% 9% 14% 19% 17% 5%	2052
	11th to 20th	Night	44% 8% 10% 16% 20% 2	2090
	21st to end	Night	45% 6% 12% 16% 16% 4	2090
October	1st to 10th	Night	36% 4 10% 18% 25% 7%	3690
	11th to 20th	Night	23% 2 6% 21% 27% 21%	3779
	21st to end	Night	28% 3 5% 21% 27% 16%	4120
November	1st to 10th	Night	34% 4 7% 20% 24% 11%	2264
	11th to 20th	Night	35% 4 6% 18% 25% 12%	2427
	21st to end	Night	34% 4 7% 22% 27% 7%	2470
December	1st to 10th	Night	45% 4 9% 18% 19% 5%	2470
	11th to 20th	Night	37% 3 7% 18% 25% 9%	3044
	21st to end	Night	41% 4 9% 21% 21% 3	4532

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% 15% 34% 24% 6%	270
	11th to 20th	Day	25% 19% 28% 23% 5% 1	270
	21st to end	Day	23% 14% 39% 18% 6%	297
February	1st to 10th	Day	22% 16% 34% 20% 7% 1	270
	11th to 20th	Day	33% 11% 40% 11% 4	270
	21st to end	Day	26% 13% 36% 20% 4	269
March	1st to 10th	Day	22% 10% 34% 24% 9% 2	460
	11th to 20th	Day	20% 11% 40% 22% 7%	460
	21st to end	Day	21% 14% 34% 23% 7% 1	506
April	1st to 10th	Day	17% 14% 32% 23% 11% 3	460
	11th to 20th	Day	15% 11% 29% 23% 17% 4	452
	21st to end	Day	17% 8% 27% 25% 18% 6%	460
May	1st to 10th	Day	10% 8% 30% 28% 18% 5%	463
	11th to 20th	Day	18% 5% 15% 26% 23% 13%	487
	21st to end	Day	15% 3 12% 23% 29% 18%	529
June	1st to 10th	Day	11% 2 13% 29% 30% 14%	490
	11th to 20th	Day	10% 2 16% 26% 23% 23%	490
	21st to end	Day	9% 2 11% 28% 34% 17%	490
July	1st to 10th	Day	11% 2 7% 19% 34% 27%	485
	11th to 20th	Day	7% 2 6% 28% 32% 26%	484
	21st to end	Day	8% 2 8% 27% 35% 21%	532
August	1st to 10th	Day	14% 2 10% 23% 31% 19%	486
	11th to 20th	Day	11% 3 8% 24% 32% 22%	479
	21st to end	Day	12% 2 6% 24% 29% 27%	539
September	1st to 10th	Day	13% 2 9% 22% 33% 22%	490
	11th to 20th	Day	17% 3 12% 19% 28% 20%	490
	21st to end	Day	24% 3 17% 24% 25% 8%	490
October	1st to 10th	Day	16% 4 19% 23% 26% 12%	490
	11th to 20th	Day	12% 5% 23% 29% 22% 8%	490
	21st to end	Day	17% 7% 19% 29% 21% 7%	539
November	1st to 10th	Day	20% 7% 24% 28% 17% 4	467
	11th to 20th	Day	16% 7% 35% 28% 12% 2	308
	21st to end	Day	13% 7% 31% 29% 16% 3	270
December	1st to 10th	Day	26% 8% 32% 26% 7% 1	270
	11th to 20th	Day	20% 10% 30% 26% 13% 2	270
	21st to end	Day	24% 10% 33% 22% 10% 1	297
January	1st to 10th	Night	21% 12% 34% 27% 6%	760
	11th to 20th	Night	20% 11% 35% 29% 5%	760
	21st to end	Night	19% 11% 36% 31% 3	836
February	1st to 10th	Night	19% 10% 36% 32% 3	760
	11th to 20th	Night	24% 13% 39% 23% 2	743
	21st to end	Night	19% 13% 38% 26% 4	628
March	1st to 10th	Night	17% 10% 34% 34% 6%	760
	11th to 20th	Night	18% 11% 35% 27% 9% 1	760
	21st to end	Night	21% 8% 34% 30% 7%	836
April	1st to 10th	Night	16% 12% 32% 30% 10%	760
	11th to 20th	Night	15% 12% 27% 31% 16% 1	751
	21st to end	Night	14% 7% 28% 35% 16%	622
May	1st to 10th	Night	12% 7% 27% 34% 19% 1	570
	11th to 20th	Night	16% 4 21% 33% 24% 2	561
	21st to end	Night	16% 2 10% 32% 36% 4	617
June	1st to 10th	Night	11% 3 13% 38% 30% 5%	570
	11th to 20th	Night	12% 3 13% 28% 34% 10%	570
	21st to end	Night	9% 1 11% 33% 40% 6%	570
July	1st to 10th	Night	10% 2 7% 27% 44% 10%	555
	11th to 20th	Night	9% 2 5% 29% 46% 9%	552
	21st to end	Night	8% 1 8% 32% 43% 8%	624
August	1st to 10th	Night	14% 2 7% 27% 42% 8%	567
	11th to 20th	Night	14% 2 6% 28% 42% 8%	564
	21st to end	Night	11% 2 7% 25% 46% 9%	769
September	1st to 10th	Night	12% 3 6% 29% 40% 9%	760
	11th to 20th	Night	17% 4 12% 23% 38% 7%	760
	21st to end	Night	20% 3 16% 30% 27% 4	760
October	1st to 10th	Night	16% 4 16% 30% 28% 6%	760
	11th to 20th	Night	16% 5% 21% 33% 22% 3	760
	21st to end	Night	14% 6% 22% 34% 22% 2	836
November	1st to 10th	Night	17% 5% 24% 34% 18% 3	755
	11th to 20th	Night	15% 7% 30% 33% 13% 1	760
	21st to end	Night	16% 6% 28% 35% 14% 1	760
December	1st to 10th	Night	22% 9% 27% 34% 8%	760
	11th to 20th	Night	20% 6% 29% 36% 9% 1	760
	21st to end	Night	25% 9% 26% 31% 9%	836

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