Pinehurst
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pinehurst clear sky chart from 2005-11-06 to 2025-07-21.

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 4 6% 7% 43%	120419
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 45%	118714
Transparency	Day	38% 6% 11% 19% 19% 6%	124067
	Night	38% 6% 10% 18% 21% 7%	123203
Seeing	Day	15% 10% 25% 25% 17% 7%	16438
	Night	16% 8% 26% 32% 17% 2	26532

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% 5% 2 5% 2 3 2 2 3 4 57%	4056
	11th to 20th	Day	13% 5% 2 4 3 2 3 2 3 4 59%	4060
	21st to end	Day	14% 8% 2 7% 5% 4 4 3 5% 4 45%	4466
February	1st to 10th	Day	15% 7% 2 6% 4 4 3 3 6% 8% 43%	1800
	11th to 20th	Day	22% 6% 1 5% 3 3 3 2 4 6% 45%	1803
	21st to end	Day	19% 7% 2 6% 4 3 4 3 5% 5% 43%	1800
March	1st to 10th	Day	21% 7% 2 5% 4 3 4 3 5% 6% 40%	4935
	11th to 20th	Day	10% 4 2 6% 4 3 4 3 5% 6% 53%	4980
	21st to end	Day	15% 6% 2 5% 4 4 4 3 4 5% 48%	5465
April	1st to 10th	Day	11% 4 1 4 3 3 4 3 5% 8% 52%	2283
	11th to 20th	Day	12% 5% 2 4 4 4 4 4 5% 7% 50%	2374
	21st to end	Day	12% 4 2 5% 4 4 5% 3 5% 7% 48%	2403
May	1st to 10th	Day	8% 7% 3 8% 5% 5% 5% 5% 7% 10% 36%	5862
	11th to 20th	Day	19% 6% 3 7% 5% 5% 5% 5% 7% 8% 30%	5861
	21st to end	Day	12% 5% 2 6% 4 5% 5% 4 6% 8% 44%	6433
June	1st to 10th	Day	9% 5% 3 6% 5% 5% 6% 5% 8% 9% 39%	2600
	11th to 20th	Day	8% 4 2 6% 5% 6% 5% 4 8% 10% 41%	2600
	21st to end	Day	7% 4 2 6% 6% 5% 6% 6% 10% 11% 39%	2600
July	1st to 10th	Day	8% 6% 3 8% 6% 7% 7% 6% 8% 10% 32%	4250
	11th to 20th	Day	9% 6% 2 8% 6% 6% 7% 6% 8% 12% 30%	4250
	21st to end	Day	12% 8% 3 8% 6% 6% 6% 6% 8% 10% 27%	4466
August	1st to 10th	Day	23% 9% 3 7% 5% 5% 6% 5% 7% 9% 22%	4104
	11th to 20th	Day	11% 5% 2 7% 5% 6% 6% 5% 8% 10% 34%	3953
	21st to end	Day	6% 4 2 5% 4 5% 5% 5% 6% 10% 49%	4180
September	1st to 10th	Day	8% 4 2 7% 4 5% 6% 4 6% 9% 44%	2273
	11th to 20th	Day	13% 6% 3 6% 5% 5% 4 4 6% 8% 42%	2090
	21st to end	Day	19% 5% 3 7% 4 4 4 3 5% 7% 39%	2081
October	1st to 10th	Day	15% 5% 2 6% 3 3 3 2 4 6% 51%	1900
	11th to 20th	Day	11% 4 1 4 4 3 3 2 4 5% 59%	1900
	21st to end	Day	11% 5% 1 4 3 3 3 2 4 5% 58%	2090
November	1st to 10th	Day	13% 6% 2 4 3 3 3 3 4 5% 54%	1957
	11th to 20th	Day	15% 5% 1 4 2 4 3 3 4 7% 53%	1975
	21st to end	Day	14% 5% 2 5% 3 3 4 3 5% 6% 49%	1800
December	1st to 10th	Day	12% 5% 2 6% 4 3 3 2 5% 4 53%	2930
	11th to 20th	Day	17% 5% 2 5% 4 3 3 3 5% 6% 45%	3373
	21st to end	Day	17% 6% 2 6% 3 3 4 2 4 6% 46%	4466
January	1st to 10th	Night	13% 5% 2 4 3 3 3 2 4 4 57%	5889
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 4 4 53%	5900
	21st to end	Night	15% 8% 2 6% 3 3 4 3 4 5% 46%	6490
February	1st to 10th	Night	16% 6% 2 6% 4 4 4 3 5% 6% 45%	2600
	11th to 20th	Night	21% 6% 2 5% 4 3 3 4 5% 5% 42%	2478
	21st to end	Night	16% 6% 2 4 3 3 3 3 6% 7% 47%	1830
March	1st to 10th	Night	20% 7% 3 6% 4 3 3 3 4 5% 42%	4918
	11th to 20th	Night	12% 4 2 4 3 3 4 4 5% 7% 53%	4980
	21st to end	Night	15% 4 1 6% 4 3 3 4 4 5% 49%	5467
April	1st to 10th	Night	13% 5% 2 5% 4 3 3 4 5% 7% 49%	2115
	11th to 20th	Night	12% 4 2 5% 5% 3 4 3 4 6% 51%	1975
	21st to end	Night	11% 4 1 5% 4 4 6% 4 6% 7% 49%	2000
May	1st to 10th	Night	11% 7% 3 7% 4 4 4 4 6% 9% 40%	4045
	11th to 20th	Night	18% 8% 3 7% 5% 5% 4 4 5% 8% 35%	4032
	21st to end	Night	14% 5% 2 6% 4 4 4 4 7% 9% 41%	4421
June	1st to 10th	Night	11% 7% 2 7% 5% 5% 5% 6% 7% 9% 38%	1800
	11th to 20th	Night	11% 5% 2 6% 5% 6% 6% 5% 6% 9% 38%	1800
	21st to end	Night	7% 6% 2 6% 5% 4 6% 5% 9% 12% 39%	1800
July	1st to 10th	Night	11% 6% 2 7% 6% 6% 7% 5% 8% 10% 32%	2930
	11th to 20th	Night	13% 7% 3 8% 5% 5% 6% 5% 8% 11% 30%	2930
	21st to end	Night	16% 9% 3 10% 5% 5% 5% 5% 7% 8% 26%	3087
August	1st to 10th	Night	25% 7% 2 8% 5% 5% 4 4 7% 8% 24%	2825
	11th to 20th	Night	10% 5% 2 6% 5% 5% 6% 6% 7% 12% 35%	2842
	21st to end	Night	6% 4 2 5% 5% 4 4 4 7% 11% 49%	3476
September	1st to 10th	Night	8% 6% 2 6% 4 5% 4 4 6% 9% 45%	1903
	11th to 20th	Night	14% 7% 2 6% 5% 4 4 3 5% 7% 42%	2090
	21st to end	Night	19% 7% 2 7% 5% 4 4 4 5% 6% 38%	2097
October	1st to 10th	Night	14% 6% 2 6% 3 3 3 3 3 6% 51%	2280
	11th to 20th	Night	13% 5% 2 4 3 3 3 2 4 5% 55%	2280
	21st to end	Night	12% 5% 1 4 2 2 3 3 4 6% 57%	2508
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 5% 54%	2341
	11th to 20th	Night	13% 7% 2 4 4 4 3 3 5% 5% 50%	2423
	21st to end	Night	14% 4 2 5% 3 3 3 3 4 7% 52%	2600
December	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 4 5% 53%	4250
	11th to 20th	Night	17% 8% 2 8% 4 4 4 3 4 5% 41%	4822
	21st to end	Night	18% 5% 2 5% 3 4 3 3 4 5% 47%	6490

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	34% 2 4 19% 33% 9%	4057
	11th to 20th	Day	31% 3 4 16% 35% 12%	4060
	21st to end	Day	43% 3 4 18% 22% 10%	4466
February	1st to 10th	Day	39% 5% 10% 19% 21% 6%	1800
	11th to 20th	Day	43% 4 7% 17% 23% 7%	1812
	21st to end	Day	44% 4 7% 17% 20% 8%	1800
March	1st to 10th	Day	46% 4 6% 15% 19% 11%	4935
	11th to 20th	Day	31% 5% 8% 14% 26% 17%	4980
	21st to end	Day	39% 4 8% 21% 21% 8%	5465
April	1st to 10th	Day	29% 6% 11% 21% 26% 7%	2283
	11th to 20th	Day	34% 5% 10% 22% 21% 8%	2374
	21st to end	Day	35% 7% 12% 24% 18% 4	2403
May	1st to 10th	Day	41% 9% 17% 21% 10% 1	5897
	11th to 20th	Day	49% 7% 14% 19% 11% 1	5865
	21st to end	Day	36% 8% 13% 20% 19% 3	6447
June	1st to 10th	Day	38% 10% 15% 22% 15% 1	2600
	11th to 20th	Day	34% 11% 17% 22% 14% 2	2600
	21st to end	Day	33% 12% 16% 22% 14% 2	2600
July	1st to 10th	Day	42% 10% 18% 17% 11% 2	4185
	11th to 20th	Day	43% 12% 26% 15% 3 1	4181
	21st to end	Day	48% 13% 16% 15% 9%	4324
August	1st to 10th	Day	56% 10% 17% 11% 5%	4091
	11th to 20th	Day	42% 10% 17% 22% 9% 1	3992
	21st to end	Day	28% 8% 14% 32% 15% 2	4180
September	1st to 10th	Day	35% 10% 16% 17% 18% 5%	2273
	11th to 20th	Day	40% 7% 11% 16% 21% 4	2090
	21st to end	Day	43% 7% 10% 20% 15% 5%	2081
October	1st to 10th	Day	33% 4 8% 20% 26% 9%	3160
	11th to 20th	Day	19% 3 6% 19% 26% 28%	3140
	21st to end	Day	24% 4 5% 24% 24% 19%	3428
November	1st to 10th	Day	32% 4 8% 19% 28% 9%	1957
	11th to 20th	Day	33% 4 7% 20% 28% 8%	1975
	21st to end	Day	35% 4 7% 21% 23% 9%	1800
December	1st to 10th	Day	35% 4 7% 18% 26% 11%	2930
	11th to 20th	Day	40% 4 10% 17% 22% 6%	3370
	21st to end	Day	41% 3 10% 23% 22% 2	4466
January	1st to 10th	Night	31% 3 6% 16% 36% 8%	5889
	11th to 20th	Night	35% 4 6% 13% 34% 9%	5900
	21st to end	Night	41% 4 4 15% 28% 8%	6490
February	1st to 10th	Night	41% 4 9% 19% 20% 7%	2600
	11th to 20th	Night	44% 4 8% 16% 22% 7%	2480
	21st to end	Night	36% 5% 9% 18% 23% 9%	1830
March	1st to 10th	Night	46% 4 6% 11% 25% 8%	4918
	11th to 20th	Night	31% 4 7% 12% 27% 19%	4980
	21st to end	Night	38% 4 7% 21% 23% 7%	5467
April	1st to 10th	Night	34% 6% 9% 19% 23% 8%	2115
	11th to 20th	Night	33% 6% 9% 22% 21% 9%	1975
	21st to end	Night	33% 8% 11% 24% 20% 4	2000
May	1st to 10th	Night	39% 8% 17% 20% 15% 2	4072
	11th to 20th	Night	47% 7% 16% 18% 13% 1	4033
	21st to end	Night	37% 8% 13% 24% 16% 2	4429
June	1st to 10th	Night	40% 11% 15% 20% 12% 2	1800
	11th to 20th	Night	40% 10% 15% 20% 13% 1	1800
	21st to end	Night	35% 13% 17% 21% 12% 3	1800
July	1st to 10th	Night	45% 11% 18% 15% 10% 1	2885
	11th to 20th	Night	46% 13% 23% 13% 4 1	2876
	21st to end	Night	53% 11% 13% 15% 8%	2988
August	1st to 10th	Night	56% 8% 17% 15% 4 1	2814
	11th to 20th	Night	40% 9% 23% 21% 6% 1	2869
	21st to end	Night	29% 7% 13% 29% 19% 3	3476
September	1st to 10th	Night	35% 10% 13% 20% 16% 6%	1903
	11th to 20th	Night	41% 9% 12% 15% 20% 3	2090
	21st to end	Night	46% 7% 11% 16% 15% 4	2097
October	1st to 10th	Night	35% 4 8% 20% 26% 6%	3800
	11th to 20th	Night	23% 3 5% 16% 30% 23%	3779
	21st to end	Night	25% 3 7% 23% 24% 18%	4120
November	1st to 10th	Night	33% 4 6% 19% 24% 13%	2341
	11th to 20th	Night	36% 4 6% 16% 26% 12%	2423
	21st to end	Night	33% 4 7% 22% 26% 9%	2600
December	1st to 10th	Night	34% 4 6% 18% 28% 10%	4250
	11th to 20th	Night	46% 4 9% 16% 17% 8%	4824
	21st to end	Night	40% 3 10% 22% 23% 2	6490

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	20% 26% 35% 17% 2	300
	11th to 20th	Day	20% 26% 37% 12% 4	300
	21st to end	Day	19% 25% 40% 12% 3	330
February	1st to 10th	Day	19% 20% 39% 18% 4	300
	11th to 20th	Day	35% 20% 35% 10% 1	300
	21st to end	Day	23% 20% 34% 19% 3 1	399
March	1st to 10th	Day	22% 20% 28% 24% 5%	500
	11th to 20th	Day	19% 19% 39% 17% 5% 1	500
	21st to end	Day	21% 18% 34% 20% 6% 1	550
April	1st to 10th	Day	17% 19% 33% 22% 8% 1	500
	11th to 20th	Day	13% 17% 32% 22% 13% 3	492
	21st to end	Day	13% 12% 29% 28% 15% 3	500
May	1st to 10th	Day	11% 15% 35% 23% 12% 3	503
	11th to 20th	Day	16% 7% 21% 29% 22% 5%	527
	21st to end	Day	15% 4 24% 25% 21% 11%	573
June	1st to 10th	Day	12% 3 24% 30% 25% 7%	530
	11th to 20th	Day	9% 3 20% 31% 26% 11%	530
	21st to end	Day	6% 3 15% 31% 34% 11%	530
July	1st to 10th	Day	11% 2 8% 27% 34% 18%	525
	11th to 20th	Day	9% 2 8% 27% 37% 18%	524
	21st to end	Day	8% 1 11% 33% 35% 11%	532
August	1st to 10th	Day	16% 4 13% 27% 25% 15%	486
	11th to 20th	Day	11% 3 11% 29% 29% 17%	479
	21st to end	Day	11% 2 12% 29% 26% 21%	539
September	1st to 10th	Day	9% 2 16% 29% 24% 20%	490
	11th to 20th	Day	16% 2 14% 30% 26% 12%	490
	21st to end	Day	19% 5% 22% 27% 22% 5%	490
October	1st to 10th	Day	15% 6% 23% 25% 22% 8%	490
	11th to 20th	Day	11% 11% 24% 29% 20% 6%	490
	21st to end	Day	12% 10% 24% 32% 19% 4	539
November	1st to 10th	Day	18% 8% 27% 31% 14% 3	495
	11th to 20th	Day	18% 14% 32% 25% 9% 1	475
	21st to end	Day	14% 17% 32% 26% 9% 2	300
December	1st to 10th	Day	21% 18% 42% 16% 4	300
	11th to 20th	Day	21% 14% 38% 18% 8% 2	300
	21st to end	Day	23% 15% 37% 18% 7% 2	330
January	1st to 10th	Night	21% 16% 33% 25% 6% 1	800
	11th to 20th	Night	17% 14% 36% 29% 5%	800
	21st to end	Night	20% 11% 37% 29% 3	880
February	1st to 10th	Night	19% 12% 37% 27% 5%	800
	11th to 20th	Night	24% 15% 39% 20% 2	783
	21st to end	Night	20% 14% 36% 26% 3	660
March	1st to 10th	Night	18% 13% 34% 31% 4 1	800
	11th to 20th	Night	18% 12% 37% 25% 7% 1	800
	21st to end	Night	18% 12% 38% 25% 6%	880
April	1st to 10th	Night	17% 15% 34% 27% 7%	800
	11th to 20th	Night	13% 12% 35% 30% 10%	791
	21st to end	Night	12% 7% 34% 38% 10%	800
May	1st to 10th	Night	12% 9% 33% 36% 10%	612
	11th to 20th	Night	15% 5% 25% 38% 16% 1	591
	21st to end	Night	14% 3 15% 39% 28% 2	650
June	1st to 10th	Night	12% 3 18% 42% 24% 2	600
	11th to 20th	Night	11% 4 17% 34% 28% 5%	600
	21st to end	Night	9% 2 16% 37% 34% 4	600
July	1st to 10th	Night	9% 2 11% 37% 35% 5%	585
	11th to 20th	Night	8% 1 10% 34% 39% 7%	582
	21st to end	Night	7% 2 13% 39% 35% 4	624
August	1st to 10th	Night	13% 2 8% 36% 36% 5%	567
	11th to 20th	Night	12% 1 10% 36% 35% 6%	595
	21st to end	Night	12% 2 11% 31% 39% 6%	836
September	1st to 10th	Night	10% 2 12% 35% 37% 5%	760
	11th to 20th	Night	16% 2 15% 29% 34% 4	760
	21st to end	Night	22% 3 18% 33% 22% 2	760
October	1st to 10th	Night	15% 5% 17% 31% 26% 5%	760
	11th to 20th	Night	14% 7% 28% 30% 20% 2	760
	21st to end	Night	14% 7% 25% 31% 20% 2	836
November	1st to 10th	Night	14% 7% 26% 34% 16% 3	780
	11th to 20th	Night	16% 12% 28% 32% 11% 1	800
	21st to end	Night	15% 9% 30% 31% 15% 1	800
December	1st to 10th	Night	21% 10% 29% 35% 5%	800
	11th to 20th	Night	19% 9% 31% 31% 9%	800
	21st to end	Night	21% 11% 27% 33% 8%	880

Page generated at 2025-07-18 01:10:00. Version ac07

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