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 2025-04-26.

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%	113282
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 40%	115319
Transparency	Day	43% 5% 12% 22% 15% 3	116850
	Night	44% 5% 11% 21% 16% 3	119915
Seeing	Day	19% 9% 28% 29% 12% 2	15568
	Night	20% 11% 31% 28% 10% 1	24555

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	14% 6% 2 6% 4 5% 5% 4 6% 7% 40%	3597
	11th to 20th	Day	14% 8% 2 6% 3 3 4 3 5% 6% 47%	3570
	21st to end	Day	16% 8% 2 6% 3 4 4 3 4 5% 46%	3960
February	1st to 10th	Day	18% 8% 3 5% 4 5% 4 4 6% 7% 37%	1835
	11th to 20th	Day	14% 7% 3 7% 5% 4 4 4 6% 6% 41%	1948
	21st to end	Day	16% 11% 3 5% 4 4 5% 4 5% 5% 38%	1650
March	1st to 10th	Day	22% 10% 3 5% 4 4 4 4 5% 6% 34%	4476
	11th to 20th	Day	17% 11% 3 6% 4 3 3 4 5% 6% 38%	4832
	21st to end	Day	28% 8% 2 5% 3 4 4 3 5% 6% 31%	5691
April	1st to 10th	Day	19% 9% 3 6% 5% 4 3 2 5% 6% 37%	2400
	11th to 20th	Day	17% 7% 2 5% 4 5% 5% 4 6% 6% 38%	2423
	21st to end	Day	20% 6% 2 7% 4 5% 3 3 4 6% 38%	2535
May	1st to 10th	Day	21% 11% 3 7% 5% 4 4 3 5% 6% 30%	4106
	11th to 20th	Day	22% 8% 3 7% 5% 4 4 3 4 7% 33%	4133
	21st to end	Day	16% 5% 2 5% 3 3 5% 4 5% 8% 43%	4837
June	1st to 10th	Day	19% 8% 3 6% 4 4 5% 4 6% 8% 34%	2660
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 4 6% 9% 40%	2660
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 6% 8% 34%	2660
July	1st to 10th	Day	14% 6% 3 7% 5% 4 5% 5% 7% 10% 36%	4440
	11th to 20th	Day	9% 6% 2 6% 4 4 4 5% 7% 10% 41%	4440
	21st to end	Day	17% 6% 2 6% 5% 5% 4 4 6% 7% 37%	4814
August	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 6% 7% 37%	4121
	11th to 20th	Day	15% 8% 2 7% 4 5% 5% 3 5% 7% 38%	4045
	21st to end	Day	8% 3 1 4 4 4 6% 5% 7% 10% 47%	4217
September	1st to 10th	Day	12% 5% 1 5% 4 4 4 4 6% 7% 48%	2256
	11th to 20th	Day	15% 5% 2 5% 3 3 3 3 3 6% 53%	2090
	21st to end	Day	16% 6% 2 5% 4 3 4 2 5% 7% 45%	2090
October	1st to 10th	Day	22% 6% 2 5% 3 5% 4 3 5% 5% 41%	2090
	11th to 20th	Day	15% 5% 2 5% 4 4 4 3 5% 7% 47%	1848
	21st to end	Day	22% 5% 2 6% 3 4 4 3 5% 6% 41%	1881
November	1st to 10th	Day	16% 6% 2 6% 3 3 3 3 4 5% 49%	1761
	11th to 20th	Day	18% 6% 2 4 3 2 3 2 4 7% 48%	1800
	21st to end	Day	20% 7% 2 5% 3 3 4 3 5% 6% 43%	1800
December	1st to 10th	Day	15% 9% 2 4 3 2 4 3 5% 6% 47%	2670
	11th to 20th	Day	21% 5% 2 5% 3 3 3 2 4 5% 47%	2986
	21st to end	Day	22% 10% 2 6% 3 4 4 3 4 5% 38%	3960
January	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 5% 7% 47%	6349
	11th to 20th	Night	14% 9% 3 9% 5% 5% 4 3 5% 5% 39%	6315
	21st to end	Night	16% 9% 2 6% 5% 5% 4 3 5% 5% 40%	6996
February	1st to 10th	Night	16% 9% 2 6% 4 4 4 4 6% 6% 38%	2559
	11th to 20th	Night	14% 9% 3 6% 4 4 4 3 5% 5% 41%	2338
	21st to end	Night	17% 8% 2 5% 3 4 4 4 5% 7% 41%	1980
March	1st to 10th	Night	26% 8% 2 5% 4 4 4 3 4 5% 36%	5364
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 4 5% 6% 36%	5127
	21st to end	Night	27% 8% 2 6% 3 4 4 3 6% 5% 33%	5238
April	1st to 10th	Night	20% 9% 2 6% 5% 4 3 4 4 6% 37%	2000
	11th to 20th	Night	20% 7% 2 6% 4 4 3 3 5% 6% 40%	1925
	21st to end	Night	20% 7% 2 8% 3 4 4 3 4 4 38%	1762
May	1st to 10th	Night	23% 12% 3 8% 4 4 4 3 5% 7% 26%	2834
	11th to 20th	Night	20% 9% 4 7% 5% 6% 5% 5% 6% 8% 26%	2789
	21st to end	Night	18% 7% 2 6% 4 4 4 4 5% 7% 40%	2738
June	1st to 10th	Night	20% 8% 3 6% 5% 5% 4 3 5% 6% 36%	1520
	11th to 20th	Night	19% 7% 1 6% 4 3 4 4 7% 9% 37%	1520
	21st to end	Night	18% 7% 3 7% 4 4 5% 3 6% 7% 36%	1520
July	1st to 10th	Night	12% 7% 3 7% 6% 6% 6% 4 7% 9% 33%	2520
	11th to 20th	Night	10% 5% 2 8% 5% 4 5% 5% 7% 9% 39%	2520
	21st to end	Night	16% 8% 2 7% 4 4 5% 4 6% 6% 38%	2739
August	1st to 10th	Night	20% 6% 3 8% 4 5% 5% 4 5% 7% 34%	2762
	11th to 20th	Night	14% 8% 3 8% 5% 5% 5% 4 7% 8% 34%	2782
	21st to end	Night	10% 4 1 4 4 3 5% 4 6% 8% 50%	3436
September	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	1924
	11th to 20th	Night	15% 5% 1 4 3 3 3 2 4 6% 52%	2090
	21st to end	Night	15% 6% 2 5% 5% 4 3 3 5% 7% 44%	2090
October	1st to 10th	Night	20% 6% 3 6% 5% 3 3 3 5% 6% 40%	2090
	11th to 20th	Night	16% 5% 2 6% 3 4 4 3 5% 6% 46%	2326
	21st to end	Night	23% 6% 2 6% 3 4 3 3 4 5% 40%	2717
November	1st to 10th	Night	14% 6% 2 5% 3 4 4 3 5% 6% 48%	2537
	11th to 20th	Night	17% 7% 2 5% 4 4 4 2 4 6% 47%	2600
	21st to end	Night	17% 7% 2 5% 3 3 4 3 5% 6% 44%	2600
December	1st to 10th	Night	18% 9% 2 5% 4 4 4 3 5% 5% 41%	4508
	11th to 20th	Night	22% 7% 2 6% 4 3 3 3 4 5% 42%	5208
	21st to end	Night	19% 9% 3 6% 4 3 4 3 4 5% 40%	6996

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	42% 5% 8% 27% 17% 1	3598
	11th to 20th	Day	39% 4 12% 23% 20% 3	3600
	21st to end	Day	42% 5% 8% 22% 20% 4	3960
February	1st to 10th	Day	46% 5% 14% 20% 13% 3	1835
	11th to 20th	Day	43% 5% 12% 21% 15% 3	1957
	21st to end	Day	47% 6% 10% 20% 14% 3	1650
March	1st to 10th	Day	52% 3 9% 14% 12% 10%	4479
	11th to 20th	Day	45% 5% 14% 23% 11% 3	4832
	21st to end	Day	54% 4 5% 15% 15% 7%	5691
April	1st to 10th	Day	48% 4 9% 18% 17% 4	2400
	11th to 20th	Day	43% 6% 12% 20% 16% 4	2423
	21st to end	Day	46% 5% 9% 19% 17% 3	2535
May	1st to 10th	Day	53% 8% 12% 17% 9% 1	4120
	11th to 20th	Day	50% 8% 15% 15% 10% 2	4137
	21st to end	Day	36% 8% 14% 23% 18% 1	4837
June	1st to 10th	Day	47% 7% 13% 21% 11% 1	2660
	11th to 20th	Day	41% 7% 14% 20% 16% 3	2660
	21st to end	Day	46% 8% 12% 22% 11% 1	2660
July	1st to 10th	Day	43% 6% 12% 21% 16% 1	4370
	11th to 20th	Day	37% 5% 17% 27% 13% 1	4365
	21st to end	Day	44% 6% 13% 22% 13% 2	4661
August	1st to 10th	Day	44% 7% 17% 23% 8% 1	4107
	11th to 20th	Day	44% 6% 14% 26% 9% 1	4084
	21st to end	Day	30% 6% 15% 29% 18% 2	4217
September	1st to 10th	Day	35% 6% 13% 25% 20% 1	2256
	11th to 20th	Day	34% 4 10% 28% 22% 3	2090
	21st to end	Day	39% 5% 9% 23% 21% 2	2090
October	1st to 10th	Day	44% 5% 8% 24% 17% 2	3480
	11th to 20th	Day	31% 4 7% 31% 24% 3	3038
	21st to end	Day	34% 4 9% 30% 21% 3	3081
November	1st to 10th	Day	38% 5% 13% 26% 16% 2	1761
	11th to 20th	Day	38% 5% 9% 22% 23% 3	1800
	21st to end	Day	43% 5% 15% 22% 14% 1	1800
December	1st to 10th	Day	39% 4 14% 29% 13% 1	2670
	11th to 20th	Day	41% 3 14% 18% 19% 6%	2986
	21st to end	Day	49% 4 8% 20% 14% 5%	3960
January	1st to 10th	Night	38% 4 10% 32% 15% 2	6349
	11th to 20th	Night	47% 5% 11% 21% 13% 3	6360
	21st to end	Night	47% 5% 9% 18% 17% 5%	6996
February	1st to 10th	Night	47% 6% 12% 19% 14% 3	2559
	11th to 20th	Night	44% 5% 11% 20% 16% 3	2340
	21st to end	Night	43% 5% 9% 25% 14% 4	1980
March	1st to 10th	Night	51% 4 8% 15% 15% 8%	5374
	11th to 20th	Night	48% 5% 14% 17% 13% 2	5128
	21st to end	Night	53% 4 5% 12% 20% 6%	5238
April	1st to 10th	Night	48% 5% 9% 17% 16% 4	2000
	11th to 20th	Night	46% 4 9% 20% 18% 3	1925
	21st to end	Night	47% 5% 10% 17% 17% 3	1762
May	1st to 10th	Night	57% 7% 11% 16% 8% 2	2840
	11th to 20th	Night	53% 8% 15% 13% 9% 2	2790
	21st to end	Night	42% 7% 15% 19% 15% 2	2739
June	1st to 10th	Night	49% 5% 12% 21% 13% 1	1520
	11th to 20th	Night	43% 8% 13% 20% 14% 2	1520
	21st to end	Night	44% 8% 13% 21% 13% 1	1520
July	1st to 10th	Night	45% 7% 13% 21% 14% 1	2480
	11th to 20th	Night	39% 7% 16% 23% 15%	2472
	21st to end	Night	45% 6% 12% 22% 14% 1	2651
August	1st to 10th	Night	50% 7% 13% 19% 11% 1	2752
	11th to 20th	Night	46% 8% 14% 21% 10%	2809
	21st to end	Night	30% 6% 15% 27% 22% 1	3436
September	1st to 10th	Night	36% 6% 11% 27% 20% 1	1924
	11th to 20th	Night	34% 4 10% 25% 25% 2	2090
	21st to end	Night	39% 6% 9% 25% 19% 2	2090
October	1st to 10th	Night	42% 5% 14% 23% 14% 2	3480
	11th to 20th	Night	28% 4 10% 29% 27% 3	3875
	21st to end	Night	35% 3 11% 31% 18% 2	4467
November	1st to 10th	Night	37% 5% 11% 24% 19% 3	2537
	11th to 20th	Night	40% 4 10% 22% 21% 3	2600
	21st to end	Night	41% 5% 14% 25% 14% 2	2600
December	1st to 10th	Night	45% 4 10% 28% 12% 1	4508
	11th to 20th	Night	46% 4 13% 16% 21% 1	5208
	21st to end	Night	47% 4 9% 22% 17% 2	6996

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	25% 19% 27% 24% 6%	200
	11th to 20th	Day	21% 20% 35% 19% 6%	200
	21st to end	Day	21% 16% 33% 25% 5%	220
February	1st to 10th	Day	25% 16% 37% 20% 2	397
	11th to 20th	Day	23% 19% 38% 17% 3	496
	21st to end	Day	20% 17% 34% 24% 5%	414
March	1st to 10th	Day	23% 15% 33% 24% 5%	500
	11th to 20th	Day	19% 19% 36% 23% 3 1	500
	21st to end	Day	25% 16% 34% 18% 5% 2	550
April	1st to 10th	Day	27% 14% 32% 19% 6% 2	500
	11th to 20th	Day	22% 13% 39% 19% 6% 1	492
	21st to end	Day	22% 8% 34% 28% 8% 1	480
May	1st to 10th	Day	25% 8% 33% 25% 7% 1	463
	11th to 20th	Day	17% 8% 30% 33% 10% 2	487
	21st to end	Day	19% 4 25% 35% 14% 3	529
June	1st to 10th	Day	19% 4 24% 34% 16% 3	490
	11th to 20th	Day	13% 5% 30% 36% 14% 2	490
	21st to end	Day	18% 3 28% 36% 13% 2	490
July	1st to 10th	Day	17% 3 15% 39% 22% 4	485
	11th to 20th	Day	13% 4 18% 39% 22% 4	484
	21st to end	Day	11% 3 17% 49% 18% 2	532
August	1st to 10th	Day	12% 3 20% 36% 26% 3	486
	11th to 20th	Day	14% 4 19% 35% 23% 6%	479
	21st to end	Day	13% 3 18% 41% 18% 7%	539
September	1st to 10th	Day	16% 4 24% 29% 20% 7%	490
	11th to 20th	Day	19% 5% 23% 27% 18% 8%	490
	21st to end	Day	17% 4 28% 30% 15% 6%	490
October	1st to 10th	Day	25% 7% 23% 24% 17% 4	490
	11th to 20th	Day	17% 11% 26% 31% 14% 2	417
	21st to end	Day	25% 8% 31% 25% 10% 1	429
November	1st to 10th	Day	15% 11% 33% 27% 11% 3	395
	11th to 20th	Day	22% 16% 33% 24% 5% 1	400
	21st to end	Day	25% 15% 27% 23% 9% 1	400
December	1st to 10th	Day	20% 10% 40% 23% 7%	244
	11th to 20th	Day	22% 19% 37% 20% 3	200
	21st to end	Day	22% 16% 33% 21% 6% 2	220
January	1st to 10th	Night	22% 19% 39% 18% 3	800
	11th to 20th	Night	24% 17% 39% 17% 3	800
	21st to end	Night	19% 19% 39% 20% 3	880
February	1st to 10th	Night	22% 17% 37% 22% 2	800
	11th to 20th	Night	21% 17% 44% 15% 3	783
	21st to end	Night	22% 15% 37% 22% 4	660
March	1st to 10th	Night	23% 17% 36% 21% 3	800
	11th to 20th	Night	20% 14% 38% 23% 6%	800
	21st to end	Night	24% 12% 34% 24% 6%	880
April	1st to 10th	Night	24% 13% 33% 25% 5%	800
	11th to 20th	Night	24% 8% 35% 24% 8% 1	741
	21st to end	Night	22% 8% 32% 31% 7% 1	588
May	1st to 10th	Night	26% 5% 30% 29% 8% 1	570
	11th to 20th	Night	22% 5% 28% 34% 10% 1	551
	21st to end	Night	21% 5% 21% 36% 14% 2	411
June	1st to 10th	Night	22% 5% 21% 36% 14% 3	380
	11th to 20th	Night	20% 5% 21% 40% 13% 1	380
	21st to end	Night	20% 3 19% 41% 15% 1	380
July	1st to 10th	Night	17% 3 16% 43% 18% 2	370
	11th to 20th	Night	13% 4 13% 48% 22% 1	368
	21st to end	Night	15% 3 14% 47% 20% 1	416
August	1st to 10th	Night	14% 2 13% 45% 24% 1	530
	11th to 20th	Night	14% 3 16% 42% 23% 2	562
	21st to end	Night	14% 3 17% 37% 25% 3	809
September	1st to 10th	Night	15% 3 24% 33% 23% 3	760
	11th to 20th	Night	16% 5% 21% 34% 19% 5%	760
	21st to end	Night	19% 4 24% 31% 19% 4	760
October	1st to 10th	Night	23% 6% 24% 28% 16% 3	760
	11th to 20th	Night	18% 9% 29% 30% 13% 2	760
	21st to end	Night	25% 9% 31% 25% 9%	836
November	1st to 10th	Night	15% 9% 36% 29% 9% 1	780
	11th to 20th	Night	20% 14% 36% 23% 7% 1	800
	21st to end	Night	21% 18% 33% 23% 5% 1	800
December	1st to 10th	Night	23% 13% 40% 20% 4 1	800
	11th to 20th	Night	23% 17% 35% 22% 3	800
	21st to end	Night	24% 16% 37% 20% 2	880

Page generated at 2025-04-23 09:25:06. Version ac07

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