Hampton Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hampton Beach clear sky chart from 2005-11-06 to 2026-08-30.

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	17% 7% 2 6% 4 4 4 4 5% 7% 40%	143601
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 40%	138618
Transparency	Day	43% 5% 12% 23% 15% 2	147123
	Night	44% 5% 11% 22% 16% 2	143185
Seeing	Day	20% 10% 29% 27% 11% 2	17354
	Night	20% 11% 31% 27% 10% 1	26123

By Month

Percentage Cloud Cover NE (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	12% 6% 3 8% 4 5% 6% 4 6% 7% 39%	4661
	11th to 20th	Day	16% 9% 3 6% 3 3 4 3 4 6% 45%	4650
	21st to end	Day	13% 8% 2 5% 3 3 4 3 4 6% 48%	5124
February	1st to 10th	Day	17% 8% 3 5% 4 5% 4 4 6% 7% 37%	1927
	11th to 20th	Day	13% 7% 3 7% 5% 4 4 4 6% 6% 41%	2048
	21st to end	Day	16% 11% 3 6% 4 4 5% 3 5% 5% 38%	1730
March	1st to 10th	Day	22% 10% 3 5% 4 4 4 4 5% 6% 34%	4576
	11th to 20th	Day	17% 11% 3 6% 4 4 4 4 5% 6% 38%	4938
	21st to end	Day	28% 8% 2 5% 3 4 4 3 5% 6% 31%	5817
April	1st to 10th	Day	20% 9% 3 6% 5% 4 3 2 5% 6% 37%	2520
	11th to 20th	Day	17% 7% 2 5% 4 5% 5% 4 6% 6% 38%	2545
	21st to end	Day	20% 6% 2 7% 4 5% 3 3 4 6% 38%	2730
May	1st to 10th	Day	26% 9% 3 6% 4 4 4 3 5% 6% 29%	7639
	11th to 20th	Day	19% 8% 3 8% 4 4 4 3 5% 7% 35%	7719
	21st to end	Day	21% 7% 3 6% 4 4 5% 4 5% 7% 33%	9060
June	1st to 10th	Day	19% 7% 2 6% 4 4 5% 4 6% 9% 34%	2940
	11th to 20th	Day	14% 7% 2 6% 4 4 5% 4 6% 9% 40%	2940
	21st to end	Day	17% 6% 3 7% 4 5% 5% 4 6% 8% 36%	2940
July	1st to 10th	Day	17% 6% 2 6% 4 4 5% 4 7% 10% 35%	8280
	11th to 20th	Day	7% 6% 2 6% 4 4 4 4 7% 10% 47%	8280
	21st to end	Day	15% 5% 2 5% 4 4 3 3 5% 7% 46%	8993
August	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 6% 7% 38%	4383
	11th to 20th	Day	15% 8% 2 7% 4 5% 5% 3 5% 8% 39%	4305
	21st to end	Day	8% 3 1 5% 4 4 6% 5% 7% 9% 47%	4459
September	1st to 10th	Day	12% 5% 1 5% 4 4 4 4 6% 7% 48%	2375
	11th to 20th	Day	14% 4 2 5% 3 3 3 3 3 6% 54%	2200
	21st to end	Day	16% 6% 2 5% 4 4 4 3 5% 7% 45%	2200
October	1st to 10th	Day	21% 5% 2 5% 3 5% 4 3 5% 5% 43%	2200
	11th to 20th	Day	16% 5% 2 5% 4 4 4 3 5% 7% 46%	1945
	21st to end	Day	21% 5% 2 6% 3 4 4 3 5% 6% 41%	1980
November	1st to 10th	Day	16% 6% 2 6% 3 3 3 3 4 5% 49%	1851
	11th to 20th	Day	18% 6% 2 4 3 3 3 3 4 7% 48%	1890
	21st to end	Day	20% 7% 2 6% 3 3 3 3 5% 6% 43%	1890
December	1st to 10th	Day	15% 9% 2 5% 3 3 4 3 5% 6% 47%	2752
	11th to 20th	Day	21% 5% 2 5% 3 3 3 2 4 5% 48%	3066
	21st to end	Day	21% 10% 2 6% 3 4 4 3 4 5% 38%	4048
January	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 5% 7% 46%	8234
	11th to 20th	Night	16% 10% 3 8% 5% 4 4 3 5% 6% 36%	8235
	21st to end	Night	15% 8% 2 6% 4 5% 4 3 5% 5% 42%	9057
February	1st to 10th	Night	16% 9% 2 6% 4 4 4 4 6% 6% 38%	2687
	11th to 20th	Night	14% 9% 3 6% 4 5% 4 3 5% 5% 42%	2458
	21st to end	Night	17% 8% 2 5% 3 4 4 4 5% 7% 41%	2076
March	1st to 10th	Night	25% 8% 2 5% 4 4 4 3 4 5% 37%	5484
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 4 5% 6% 36%	5241
	21st to end	Night	26% 8% 2 6% 3 4 4 3 5% 5% 32%	5354
April	1st to 10th	Night	20% 9% 2 6% 5% 4 3 4 4 6% 37%	2100
	11th to 20th	Night	20% 8% 2 6% 4 3 3 3 4 6% 40%	2022
	21st to end	Night	19% 7% 2 8% 4 4 4 3 4 5% 38%	1890
May	1st to 10th	Night	28% 10% 3 6% 3 4 3 3 5% 7% 28%	5259
	11th to 20th	Night	17% 9% 3 7% 4 5% 5% 4 5% 8% 32%	5183
	21st to end	Night	22% 8% 3 8% 4 4 4 4 5% 6% 31%	5114
June	1st to 10th	Night	20% 8% 3 6% 5% 4 4 3 5% 6% 37%	1680
	11th to 20th	Night	18% 7% 2 6% 4 3 4 4 6% 9% 37%	1680
	21st to end	Night	18% 7% 2 7% 4 4 5% 3 6% 7% 37%	1680
July	1st to 10th	Night	15% 7% 3 7% 5% 4 5% 4 6% 9% 36%	4680
	11th to 20th	Night	9% 6% 2 6% 4 4 4 4 6% 10% 44%	4680
	21st to end	Night	14% 6% 2 6% 3 3 4 4 5% 7% 47%	5084
August	1st to 10th	Night	19% 6% 3 7% 4 5% 5% 4 5% 7% 35%	2938
	11th to 20th	Night	13% 7% 3 8% 5% 4 5% 4 7% 8% 34%	2962
	21st to end	Night	10% 4 1 4 4 3 5% 4 6% 8% 49%	3635
September	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 5% 7% 49%	2025
	11th to 20th	Night	14% 5% 1 4 3 3 3 2 5% 6% 52%	2200
	21st to end	Night	15% 5% 2 6% 5% 4 3 3 5% 7% 44%	2200
October	1st to 10th	Night	20% 6% 3 6% 5% 3 3 3 5% 6% 42%	2200
	11th to 20th	Night	16% 5% 2 6% 3 4 4 3 5% 6% 46%	2449
	21st to end	Night	22% 6% 2 6% 3 4 4 3 4 6% 40%	2860
November	1st to 10th	Night	15% 6% 2 5% 3 4 4 3 5% 6% 48%	2667
	11th to 20th	Night	16% 6% 2 5% 4 4 4 2 4 6% 46%	2730
	21st to end	Night	16% 7% 2 5% 4 3 4 3 5% 6% 44%	2730
December	1st to 10th	Night	17% 9% 2 5% 4 4 4 3 5% 5% 41%	4646
	11th to 20th	Night	22% 7% 2 6% 3 3 3 3 4 5% 42%	5348
	21st to end	Night	19% 9% 3 6% 4 3 4 3 4 5% 40%	7150

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	43% 4 10% 26% 15% 1	4662
	11th to 20th	Day	42% 3 10% 22% 20% 4	4680
	21st to end	Day	38% 4 9% 24% 22% 3	5124
February	1st to 10th	Day	45% 5% 13% 20% 14% 2	1927
	11th to 20th	Day	43% 5% 12% 22% 15% 3	2057
	21st to end	Day	47% 6% 10% 20% 14% 3	1730
March	1st to 10th	Day	52% 3 9% 15% 12% 10%	4579
	11th to 20th	Day	45% 5% 14% 23% 11% 3	4938
	21st to end	Day	54% 4 5% 15% 15% 7%	5817
April	1st to 10th	Day	49% 4 9% 18% 17% 4	2520
	11th to 20th	Day	44% 6% 12% 20% 15% 4	2545
	21st to end	Day	46% 5% 8% 19% 18% 4	2730
May	1st to 10th	Day	56% 6% 12% 16% 9% 1	7651
	11th to 20th	Day	49% 6% 15% 19% 11% 2	7723
	21st to end	Day	49% 6% 11% 22% 11% 1	9061
June	1st to 10th	Day	46% 6% 13% 22% 12% 1	2940
	11th to 20th	Day	41% 6% 14% 21% 16% 3	2940
	21st to end	Day	45% 7% 13% 23% 12% 1	2940
July	1st to 10th	Day	45% 6% 14% 21% 13% 1	8210
	11th to 20th	Day	32% 4 15% 31% 16%	8205
	21st to end	Day	38% 4 13% 27% 17% 2	8795
August	1st to 10th	Day	43% 7% 17% 23% 9% 1	4369
	11th to 20th	Day	43% 6% 14% 27% 9% 1	4344
	21st to end	Day	30% 6% 14% 29% 19% 2	4459
September	1st to 10th	Day	35% 5% 13% 25% 20% 1	2375
	11th to 20th	Day	34% 4 10% 28% 22% 3	2200
	21st to end	Day	39% 6% 9% 23% 20% 2	2200
October	1st to 10th	Day	43% 5% 8% 24% 18% 3	3590
	11th to 20th	Day	31% 4 7% 31% 23% 3	3135
	21st to end	Day	34% 4 9% 31% 20% 3	3180
November	1st to 10th	Day	38% 5% 12% 26% 17% 2	1851
	11th to 20th	Day	38% 5% 9% 22% 23% 3	1890
	21st to end	Day	43% 4 14% 22% 14% 1	1890
December	1st to 10th	Day	39% 4 14% 29% 13% 1	2752
	11th to 20th	Day	40% 3 13% 18% 19% 6%	3066
	21st to end	Day	49% 4 8% 20% 14% 5%	4048
January	1st to 10th	Night	39% 3 11% 29% 15% 2	8234
	11th to 20th	Night	49% 4 9% 19% 14% 4	8280
	21st to end	Night	44% 4 7% 20% 19% 5%	9057
February	1st to 10th	Night	46% 6% 12% 20% 14% 2	2687
	11th to 20th	Night	44% 5% 10% 21% 16% 3	2460
	21st to end	Night	43% 5% 9% 25% 14% 4	2076
March	1st to 10th	Night	51% 4 8% 15% 15% 8%	5494
	11th to 20th	Night	48% 5% 14% 17% 13% 2	5242
	21st to end	Night	53% 4 5% 12% 20% 6%	5354
April	1st to 10th	Night	48% 5% 9% 17% 16% 4	2100
	11th to 20th	Night	46% 4 8% 20% 18% 3	2022
	21st to end	Night	48% 5% 9% 17% 18% 3	1890
May	1st to 10th	Night	57% 5% 12% 14% 11% 2	5265
	11th to 20th	Night	50% 6% 14% 20% 10% 1	5184
	21st to end	Night	53% 5% 12% 20% 9% 1	5115
June	1st to 10th	Night	48% 5% 11% 23% 13% 1	1680
	11th to 20th	Night	43% 8% 13% 20% 14% 2	1680
	21st to end	Night	44% 8% 12% 22% 13% 1	1680
July	1st to 10th	Night	45% 5% 14% 21% 15%	4640
	11th to 20th	Night	35% 5% 16% 24% 19%	4632
	21st to end	Night	38% 4 11% 30% 16% 1	4967
August	1st to 10th	Night	49% 6% 13% 19% 12% 1	2928
	11th to 20th	Night	45% 8% 14% 22% 10% 1	2989
	21st to end	Night	31% 6% 15% 27% 21% 1	3635
September	1st to 10th	Night	35% 5% 11% 28% 20% 1	2025
	11th to 20th	Night	34% 4 10% 26% 25% 2	2200
	21st to end	Night	40% 6% 10% 25% 18% 2	2200
October	1st to 10th	Night	41% 5% 13% 23% 15% 2	3590
	11th to 20th	Night	28% 4 10% 29% 26% 2	3998
	21st to end	Night	35% 3 11% 31% 18% 2	4610
November	1st to 10th	Night	37% 5% 10% 25% 19% 3	2667
	11th to 20th	Night	39% 4 10% 23% 21% 3	2730
	21st to end	Night	41% 4 14% 25% 14% 2	2730
December	1st to 10th	Night	45% 4 10% 28% 12% 1	4646
	11th to 20th	Night	46% 4 13% 16% 21% 2	5348
	21st to end	Night	47% 4 9% 21% 17% 2	7150

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	24% 19% 28% 24% 5%	220
	11th to 20th	Day	22% 22% 34% 17% 5%	220
	21st to end	Day	21% 19% 32% 23% 5%	242
February	1st to 10th	Day	25% 15% 38% 20% 2	429
	11th to 20th	Day	22% 19% 40% 17% 3	536
	21st to end	Day	20% 18% 35% 23% 4	446
March	1st to 10th	Day	23% 15% 34% 23% 5%	540
	11th to 20th	Day	21% 20% 34% 21% 3 1	540
	21st to end	Day	27% 17% 33% 16% 5% 2	594
April	1st to 10th	Day	28% 14% 33% 18% 6% 1	540
	11th to 20th	Day	23% 14% 38% 19% 6% 1	532
	21st to end	Day	23% 9% 33% 27% 7% 1	540
May	1st to 10th	Day	27% 9% 33% 23% 6% 1	543
	11th to 20th	Day	19% 10% 32% 30% 9% 2	567
	21st to end	Day	21% 5% 28% 32% 12% 2	617
June	1st to 10th	Day	19% 4 25% 33% 15% 3	570
	11th to 20th	Day	15% 7% 31% 32% 13% 2	570
	21st to end	Day	18% 4 30% 33% 12% 2	570
July	1st to 10th	Day	18% 4 18% 38% 19% 3	565
	11th to 20th	Day	12% 6% 21% 36% 21% 4	564
	21st to end	Day	12% 5% 19% 46% 17% 2	620
August	1st to 10th	Day	11% 3 23% 34% 25% 3	566
	11th to 20th	Day	14% 5% 21% 34% 21% 5%	559
	21st to end	Day	12% 4 22% 38% 17% 6%	619
September	1st to 10th	Day	15% 4 27% 28% 18% 7%	530
	11th to 20th	Day	17% 5% 24% 28% 17% 8%	530
	21st to end	Day	18% 4 29% 30% 15% 5%	530
October	1st to 10th	Day	23% 8% 23% 25% 16% 4	530
	11th to 20th	Day	18% 11% 25% 30% 14% 2	450
	21st to end	Day	25% 10% 30% 24% 10% 1	462
November	1st to 10th	Day	16% 13% 33% 26% 10% 3	425
	11th to 20th	Day	22% 16% 33% 23% 5%	430
	21st to end	Day	26% 16% 28% 21% 9% 1	430
December	1st to 10th	Day	21% 11% 40% 22% 7%	266
	11th to 20th	Day	24% 19% 37% 18% 3	220
	21st to end	Day	25% 17% 32% 19% 5% 2	242
January	1st to 10th	Night	22% 20% 38% 18% 3	840
	11th to 20th	Night	25% 17% 39% 16% 3	840
	21st to end	Night	20% 20% 38% 19% 3	924
February	1st to 10th	Night	21% 16% 38% 21% 3	840
	11th to 20th	Night	21% 16% 44% 16% 3	823
	21st to end	Night	22% 15% 37% 22% 4	692
March	1st to 10th	Night	23% 17% 36% 21% 3	840
	11th to 20th	Night	20% 14% 37% 23% 5%	840
	21st to end	Night	25% 13% 34% 23% 6%	924
April	1st to 10th	Night	25% 13% 33% 25% 5%	840
	11th to 20th	Night	25% 8% 35% 24% 8% 1	778
	21st to end	Night	22% 9% 31% 31% 6% 1	630
May	1st to 10th	Night	28% 6% 30% 27% 7% 1	630
	11th to 20th	Night	21% 5% 30% 33% 10% 1	609
	21st to end	Night	22% 6% 22% 35% 13% 2	455
June	1st to 10th	Night	21% 5% 22% 37% 13% 2	420
	11th to 20th	Night	19% 6% 22% 39% 12% 1	420
	21st to end	Night	20% 4 20% 41% 15% 1	420
July	1st to 10th	Night	17% 3 18% 42% 17% 2	410
	11th to 20th	Night	13% 4 15% 46% 21% 1	408
	21st to end	Night	14% 3 17% 46% 19% 1	460
August	1st to 10th	Night	13% 3 15% 45% 23% 1	586
	11th to 20th	Night	14% 3 17% 42% 21% 2	622
	21st to end	Night	14% 3 20% 37% 23% 3	888
September	1st to 10th	Night	15% 3 24% 35% 22% 2	800
	11th to 20th	Night	15% 5% 21% 33% 20% 5%	800
	21st to end	Night	19% 4 24% 32% 19% 4	800
October	1st to 10th	Night	23% 7% 24% 28% 16% 3	800
	11th to 20th	Night	18% 9% 28% 31% 13% 2	800
	21st to end	Night	25% 10% 31% 26% 9%	880
November	1st to 10th	Night	16% 10% 36% 28% 9% 1	820
	11th to 20th	Night	20% 14% 37% 22% 7% 1	840
	21st to end	Night	21% 18% 33% 22% 5% 1	840
December	1st to 10th	Night	24% 13% 40% 19% 4	840
	11th to 20th	Night	23% 18% 35% 21% 3	840
	21st to end	Night	25% 17% 37% 20% 2	924

Page generated at 2026-08-27 04:07:12. Version ac07

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