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 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% 6% 2 6% 4 4 5% 4 6% 8% 42%	101155
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	97816
Transparency	Day	38% 7% 12% 20% 18% 6%	104805
	Night	39% 6% 10% 18% 20% 7%	102305
Seeing	Day	15% 10% 25% 25% 18% 7%	15496
	Night	16% 8% 26% 32% 17% 2	25580

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	17% 5% 2 5% 2 3 2 3 3 5% 52%	2836
	11th to 20th	Day	13% 5% 2 5% 3 3 3 2 4 4 54%	2840
	21st to end	Day	19% 9% 2 7% 4 3 3 3 4 4 43%	3124
February	1st to 10th	Day	15% 7% 2 6% 3 4 3 3 6% 8% 42%	1710
	11th to 20th	Day	21% 6% 1 5% 4 3 3 2 4 6% 46%	1710
	21st to end	Day	20% 7% 2 7% 4 3 3 3 5% 5% 41%	1712
March	1st to 10th	Day	23% 8% 3 5% 4 3 4 3 5% 6% 37%	3435
	11th to 20th	Day	10% 4 2 5% 4 3 4 3 5% 6% 54%	3480
	21st to end	Day	19% 7% 2 6% 4 4 3 3 4 5% 44%	3815
April	1st to 10th	Day	10% 4 2 4 4 3 4 3 5% 8% 53%	2169
	11th to 20th	Day	12% 5% 2 4 4 4 4 4 5% 7% 49%	2254
	21st to end	Day	13% 4 2 5% 4 4 5% 3 5% 7% 49%	2283
May	1st to 10th	Day	9% 7% 3 9% 6% 6% 5% 5% 7% 9% 35%	4082
	11th to 20th	Day	16% 7% 3 7% 5% 4 5% 4 6% 7% 36%	4081
	21st to end	Day	7% 4 2 5% 4 5% 4 4 7% 9% 49%	4476
June	1st to 10th	Day	9% 5% 3 6% 5% 5% 6% 5% 8% 9% 39%	2470
	11th to 20th	Day	8% 4 2 6% 5% 6% 5% 4 8% 10% 41%	2470
	21st to end	Day	7% 4 2 6% 6% 5% 6% 6% 10% 11% 37%	2470
July	1st to 10th	Day	8% 6% 3 8% 6% 7% 7% 5% 8% 10% 32%	4120
	11th to 20th	Day	10% 6% 2 8% 6% 6% 7% 6% 8% 12% 30%	4120
	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 2 3 3 2 4 5% 56%	1887
	11th to 20th	Day	15% 5% 2 4 2 3 3 3 4 7% 53%	1877
	21st to end	Day	14% 5% 2 5% 4 3 4 3 5% 7% 49%	1710
December	1st to 10th	Day	18% 7% 2 6% 4 3 3 3 6% 6% 41%	1710
	11th to 20th	Day	17% 4 2 4 3 2 2 2 5% 5% 54%	2153
	21st to end	Day	16% 6% 2 6% 4 3 4 2 4 6% 45%	3124
January	1st to 10th	Night	16% 6% 2 5% 4 3 3 3 5% 5% 48%	4109
	11th to 20th	Night	12% 7% 2 6% 5% 3 4 3 5% 5% 46%	4120
	21st to end	Night	19% 7% 2 6% 3 3 3 3 4 5% 45%	4532
February	1st to 10th	Night	16% 6% 2 6% 4 4 4 3 4 6% 45%	2470
	11th to 20th	Night	20% 6% 2 5% 4 3 3 3 5% 5% 43%	2351
	21st to end	Night	16% 7% 2 4 3 3 3 3 6% 7% 46%	1742
March	1st to 10th	Night	24% 9% 4 7% 4 4 3 3 4 5% 34%	3418
	11th to 20th	Night	13% 4 2 5% 4 4 4 4 5% 6% 51%	3480
	21st to end	Night	19% 5% 1 5% 4 3 4 4 4 5% 47%	3817
April	1st to 10th	Night	13% 5% 2 5% 3 3 3 3 6% 7% 50%	2009
	11th to 20th	Night	12% 4 2 5% 5% 4 4 3 4 6% 50%	1875
	21st to end	Night	11% 4 1 5% 4 4 5% 4 6% 7% 50%	1900
May	1st to 10th	Night	10% 7% 3 8% 4 4 4 4 6% 8% 41%	2825
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 3 5% 7% 38%	2812
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 7% 10% 44%	3079
June	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 5% 7% 9% 38%	1710
	11th to 20th	Night	11% 5% 2 6% 5% 5% 6% 5% 6% 9% 39%	1710
	21st to end	Night	7% 6% 2 6% 5% 4 6% 5% 8% 11% 38%	1710
July	1st to 10th	Night	11% 6% 2 7% 6% 6% 7% 5% 8% 10% 33%	2840
	11th to 20th	Night	13% 7% 3 8% 5% 5% 6% 5% 8% 11% 30%	2840
	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%	2264
	11th to 20th	Night	13% 7% 2 4 4 4 3 3 5% 5% 51%	2301
	21st to end	Night	14% 4 2 5% 4 3 3 3 4 8% 51%	2470
December	1st to 10th	Night	18% 8% 2 6% 4 4 4 3 5% 6% 41%	2470
	11th to 20th	Night	18% 6% 2 5% 3 3 3 3 4 4 49%	3042
	21st to end	Night	18% 5% 2 5% 3 4 4 3 5% 6% 46%	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% 3 5% 24% 25% 7%	2837
	11th to 20th	Day	34% 4 5% 18% 30% 9%	2840
	21st to end	Day	46% 3 5% 16% 22% 8%	3124
February	1st to 10th	Day	40% 5% 10% 19% 21% 6%	1710
	11th to 20th	Day	42% 4 6% 17% 24% 7%	1719
	21st to end	Day	45% 4 8% 17% 19% 7%	1712
March	1st to 10th	Day	48% 4 8% 17% 14% 9%	3435
	11th to 20th	Day	30% 5% 9% 16% 27% 13%	3480
	21st to end	Day	44% 5% 6% 21% 20% 5%	3815
April	1st to 10th	Day	29% 6% 10% 21% 27% 7%	2169
	11th to 20th	Day	34% 5% 10% 21% 21% 9%	2254
	21st to end	Day	35% 7% 11% 24% 19% 5%	2283
May	1st to 10th	Day	42% 11% 15% 19% 12% 2	4120
	11th to 20th	Day	45% 7% 12% 20% 15% 1	4085
	21st to end	Day	29% 10% 15% 21% 22% 3	4489
June	1st to 10th	Day	37% 10% 16% 22% 14% 1	2470
	11th to 20th	Day	34% 10% 17% 22% 15% 2	2470
	21st to end	Day	35% 13% 15% 22% 15% 2	2470
July	1st to 10th	Day	42% 11% 18% 16% 11% 2	4055
	11th to 20th	Day	44% 12% 25% 15% 3 1	4051
	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	31% 4 8% 19% 29% 9%	1887
	11th to 20th	Day	32% 4 7% 20% 27% 9%	1877
	21st to end	Day	36% 4 7% 21% 22% 9%	1710
December	1st to 10th	Day	43% 5% 10% 20% 19% 4	1710
	11th to 20th	Day	33% 3 7% 21% 27% 10%	2150
	21st to end	Day	41% 4 8% 20% 24% 3	3124
January	1st to 10th	Night	37% 3 8% 18% 27% 6%	4109
	11th to 20th	Night	39% 5% 8% 15% 26% 7%	4120
	21st to end	Night	42% 4 5% 15% 26% 8%	4532
February	1st to 10th	Night	40% 4 9% 19% 21% 7%	2470
	11th to 20th	Night	43% 4 7% 16% 22% 7%	2353
	21st to end	Night	38% 6% 9% 18% 21% 8%	1742
March	1st to 10th	Night	53% 5% 8% 13% 16% 6%	3418
	11th to 20th	Night	33% 5% 8% 12% 25% 17%	3480
	21st to end	Night	40% 5% 8% 19% 22% 6%	3817
April	1st to 10th	Night	34% 6% 8% 19% 24% 8%	2009
	11th to 20th	Night	34% 6% 9% 21% 21% 9%	1875
	21st to end	Night	32% 8% 11% 24% 21% 5%	1900
May	1st to 10th	Night	39% 9% 14% 23% 13% 2	2852
	11th to 20th	Night	45% 7% 10% 20% 17% 1	2813
	21st to end	Night	31% 9% 15% 25% 17% 2	3087
June	1st to 10th	Night	39% 11% 15% 20% 12% 2	1710
	11th to 20th	Night	39% 10% 15% 20% 14% 1	1710
	21st to end	Night	36% 13% 17% 20% 12% 3	1710
July	1st to 10th	Night	44% 11% 18% 15% 10% 1	2795
	11th to 20th	Night	46% 13% 23% 13% 4 1	2786
	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% 18% 25% 13%	2264
	11th to 20th	Night	36% 4 7% 16% 25% 13%	2301
	21st to end	Night	34% 4 6% 21% 25% 9%	2470
December	1st to 10th	Night	44% 6% 9% 17% 19% 6%	2470
	11th to 20th	Night	39% 4 7% 18% 24% 9%	3044
	21st to end	Night	40% 4 7% 21% 25% 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	19% 24% 37% 17% 3	270
	11th to 20th	Day	21% 25% 37% 13% 4	270
	21st to end	Day	19% 25% 40% 12% 4	297
February	1st to 10th	Day	20% 21% 35% 19% 4	270
	11th to 20th	Day	33% 20% 36% 10% 1	270
	21st to end	Day	25% 21% 34% 17% 3 1	367
March	1st to 10th	Day	21% 20% 28% 25% 5%	460
	11th to 20th	Day	18% 20% 39% 17% 5% 1	460
	21st to end	Day	22% 16% 34% 19% 7% 1	506
April	1st to 10th	Day	17% 19% 32% 22% 8% 1	460
	11th to 20th	Day	14% 17% 31% 22% 14% 3	452
	21st to end	Day	13% 13% 29% 27% 15% 2	460
May	1st to 10th	Day	12% 16% 35% 22% 12% 3	463
	11th to 20th	Day	14% 8% 20% 30% 23% 6%	487
	21st to end	Day	14% 3 23% 26% 23% 12%	529
June	1st to 10th	Day	11% 2 23% 31% 26% 7%	490
	11th to 20th	Day	10% 3 20% 30% 27% 11%	490
	21st to end	Day	7% 4 16% 31% 33% 10%	490
July	1st to 10th	Day	10% 2 7% 28% 34% 19%	485
	11th to 20th	Day	9% 2 9% 29% 35% 17%	484
	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	19% 8% 27% 29% 14% 3	467
	11th to 20th	Day	18% 14% 33% 25% 9% 1	437
	21st to end	Day	14% 15% 33% 26% 9% 2	270
December	1st to 10th	Day	22% 16% 41% 17% 4	270
	11th to 20th	Day	21% 14% 37% 17% 8% 2	270
	21st to end	Day	23% 14% 37% 17% 7% 2	297
January	1st to 10th	Night	21% 15% 32% 26% 6% 1	760
	11th to 20th	Night	16% 14% 35% 29% 6%	760
	21st to end	Night	20% 11% 37% 29% 3	836
February	1st to 10th	Night	19% 11% 37% 28% 5%	760
	11th to 20th	Night	24% 15% 40% 20% 2	743
	21st to end	Night	20% 14% 36% 26% 3	628
March	1st to 10th	Night	18% 11% 34% 31% 5% 1	760
	11th to 20th	Night	19% 12% 37% 25% 8% 1	760
	21st to end	Night	18% 12% 37% 26% 7%	836
April	1st to 10th	Night	16% 15% 34% 28% 7%	760
	11th to 20th	Night	14% 12% 34% 30% 10%	751
	21st to end	Night	12% 7% 34% 37% 9%	760
May	1st to 10th	Night	11% 9% 33% 36% 10%	582
	11th to 20th	Night	15% 4 25% 39% 16% 1	561
	21st to end	Night	12% 3 14% 40% 29% 2	617
June	1st to 10th	Night	11% 3 18% 42% 24% 2	570
	11th to 20th	Night	11% 4 16% 34% 29% 6%	570
	21st to end	Night	9% 2 16% 37% 33% 4	570
July	1st to 10th	Night	8% 2 11% 37% 36% 6%	555
	11th to 20th	Night	9% 1 10% 35% 39% 7%	552
	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	15% 7% 26% 33% 16% 3	755
	11th to 20th	Night	16% 11% 29% 32% 11% 1	760
	21st to end	Night	15% 8% 30% 31% 15% 1	760
December	1st to 10th	Night	20% 10% 29% 36% 6%	760
	11th to 20th	Night	19% 9% 31% 31% 9%	760
	21st to end	Night	22% 11% 27% 32% 8%	836

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