Hampton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hampton clear sky chart from 2005-11-06 to 2025-11-03.

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	19% 11% 3 8% 4 4 4 3 5% 6% 32%	126884
	Night	20% 12% 3 8% 5% 4 4 3 5% 6% 31%	123281
Transparency	Day	52% 6% 12% 19% 10% 1	130402
	Night	53% 6% 11% 19% 10% 1	127837
Seeing	Day	30% 20% 29% 15% 5% 1	17900
	Night	28% 17% 29% 21% 5%	25606

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	11% 19% 6% 14% 8% 4 3 2 3 4 26%	3157
	11th to 20th	Day	13% 15% 5% 14% 6% 4 3 2 3 4 30%	3457
	21st to end	Day	11% 10% 4 8% 5% 4 4 4 5% 6% 37%	4466
February	1st to 10th	Day	16% 13% 5% 8% 6% 5% 4 4 6% 5% 30%	1800
	11th to 20th	Day	16% 15% 3 10% 6% 4 3 3 4 7% 29%	1753
	21st to end	Day	12% 13% 4 8% 5% 5% 3 3 5% 6% 35%	1571
March	1st to 10th	Day	22% 15% 5% 12% 4 3 3 2 4 4 26%	4792
	11th to 20th	Day	20% 18% 3 7% 4 4 3 3 5% 7% 27%	4980
	21st to end	Day	26% 15% 5% 9% 4 3 3 3 5% 5% 22%	5466
April	1st to 10th	Day	23% 15% 4 7% 5% 4 4 3 4 4 26%	2322
	11th to 20th	Day	21% 12% 3 6% 5% 3 3 3 5% 6% 33%	2572
	21st to end	Day	23% 11% 3 7% 3 4 4 3 5% 6% 32%	2600
May	1st to 10th	Day	27% 14% 4 8% 5% 4 4 4 5% 5% 22%	5886
	11th to 20th	Day	22% 11% 3 7% 5% 4 4 3 5% 6% 30%	6263
	21st to end	Day	20% 11% 3 7% 4 5% 4 4 6% 8% 29%	6982
June	1st to 10th	Day	25% 11% 3 6% 4 5% 5% 3 5% 6% 28%	3000
	11th to 20th	Day	21% 9% 2 6% 5% 4 4 3 5% 7% 33%	3000
	21st to end	Day	29% 9% 3 5% 4 4 4 3 5% 7% 27%	3000
July	1st to 10th	Day	18% 9% 3 8% 5% 6% 5% 4 7% 8% 28%	6820
	11th to 20th	Day	20% 8% 2 6% 4 4 4 3 6% 7% 36%	6820
	21st to end	Day	15% 8% 3 7% 5% 4 5% 4 7% 8% 36%	6489
August	1st to 10th	Day	22% 9% 3 6% 5% 4 5% 4 5% 6% 31%	4235
	11th to 20th	Day	16% 7% 3 7% 5% 4 5% 4 6% 9% 35%	4175
	21st to end	Day	13% 6% 2 5% 4 3 4 4 5% 9% 44%	4644
September	1st to 10th	Day	15% 7% 3 5% 3 4 5% 4 5% 8% 42%	2400
	11th to 20th	Day	18% 6% 2 6% 3 3 4 3 3 6% 46%	2207
	21st to end	Day	21% 6% 2 4 2 3 3 3 5% 6% 44%	2200
October	1st to 10th	Day	19% 7% 3 6% 4 4 3 3 5% 6% 41%	2010
	11th to 20th	Day	20% 10% 3 7% 4 4 4 3 4 6% 36%	2000
	21st to end	Day	20% 11% 3 8% 4 3 4 3 5% 7% 31%	2118
November	1st to 10th	Day	23% 10% 3 7% 4 3 3 3 5% 5% 34%	1684
	11th to 20th	Day	20% 13% 4 7% 4 4 4 3 4 6% 34%	1600
	21st to end	Day	20% 16% 4 9% 4 4 4 3 4 4 28%	1600
December	1st to 10th	Day	19% 13% 4 9% 6% 4 3 3 5% 6% 27%	2610
	11th to 20th	Day	23% 13% 4 8% 4 3 3 3 3 4 32%	2729
	21st to end	Day	17% 12% 4 9% 5% 4 4 3 4 6% 32%	3476
January	1st to 10th	Night	13% 15% 5% 10% 7% 5% 4 3 5% 4 29%	6808
	11th to 20th	Night	15% 13% 4 10% 6% 4 4 3 5% 6% 30%	6413
	21st to end	Night	12% 12% 4 7% 5% 4 4 3 4 6% 39%	6490
February	1st to 10th	Night	18% 12% 4 8% 5% 5% 4 3 5% 6% 31%	2600
	11th to 20th	Night	16% 13% 5% 9% 5% 5% 4 3 5% 5% 28%	2533
	21st to end	Night	14% 11% 5% 8% 7% 4 4 3 4 5% 33%	2055
March	1st to 10th	Night	25% 15% 4 9% 4 5% 3 3 3 4 24%	5047
	11th to 20th	Night	20% 17% 4 8% 5% 5% 4 3 4 5% 25%	4979
	21st to end	Night	30% 12% 4 7% 4 3 4 3 4 4 26%	5466
April	1st to 10th	Night	22% 15% 3 8% 5% 4 4 3 4 4 28%	2075
	11th to 20th	Night	24% 10% 3 6% 4 4 3 3 5% 6% 32%	1778
	21st to end	Night	23% 11% 3 8% 5% 3 4 4 5% 6% 29%	1800
May	1st to 10th	Night	27% 15% 4 7% 5% 4 4 3 4 5% 23%	4054
	11th to 20th	Night	21% 13% 3 5% 4 4 4 3 5% 5% 33%	3646
	21st to end	Night	19% 12% 3 7% 5% 4 5% 4 5% 7% 30%	3948
June	1st to 10th	Night	26% 9% 3 8% 5% 4 4 3 5% 7% 26%	1409
	11th to 20th	Night	21% 10% 2 6% 5% 3 4 3 5% 6% 33%	1400
	21st to end	Night	29% 9% 2 6% 5% 4 4 3 4 6% 28%	1400
July	1st to 10th	Night	21% 10% 3 9% 5% 5% 5% 5% 6% 6% 23%	3160
	11th to 20th	Night	21% 10% 3 8% 5% 5% 4 4 5% 8% 28%	3160
	21st to end	Night	18% 8% 3 6% 4 4 5% 4 6% 9% 35%	4302
August	1st to 10th	Night	25% 11% 3 7% 4 4 4 4 4 6% 28%	2915
	11th to 20th	Night	15% 9% 3 7% 5% 5% 5% 4 7% 8% 32%	2872
	21st to end	Night	14% 6% 3 5% 4 4 4 3 6% 7% 43%	3253
September	1st to 10th	Night	18% 7% 2 6% 4 3 4 4 5% 7% 40%	2000
	11th to 20th	Night	19% 6% 2 5% 4 3 3 2 4 7% 43%	2190
	21st to end	Night	21% 6% 2 5% 4 4 4 4 5% 6% 41%	2200
October	1st to 10th	Night	20% 7% 2 6% 3 3 3 3 5% 7% 41%	2390
	11th to 20th	Night	16% 12% 3 7% 5% 4 4 3 5% 6% 37%	2400
	21st to end	Night	22% 10% 3 8% 4 4 3 3 5% 5% 33%	2720
November	1st to 10th	Night	21% 10% 3 7% 4 4 3 3 5% 6% 34%	2659
	11th to 20th	Night	20% 11% 4 8% 4 4 4 3 5% 5% 31%	2800
	21st to end	Night	21% 12% 4 8% 5% 4 4 3 5% 6% 30%	2800
December	1st to 10th	Night	17% 12% 4 10% 5% 4 4 3 5% 6% 30%	4580
	11th to 20th	Night	22% 12% 3 7% 4 3 3 2 4 3 35%	5477
	21st to end	Night	20% 15% 5% 9% 4 3 3 2 4 5% 30%	7502

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	63% 4 12% 14% 6%	3158
	11th to 20th	Day	58% 4 11% 19% 8% 1	3487
	21st to end	Day	45% 5% 11% 15% 20% 4	4466
February	1st to 10th	Day	55% 5% 11% 17% 10% 2	1800
	11th to 20th	Day	56% 4 12% 17% 10% 1	1761
	21st to end	Day	50% 5% 11% 21% 10% 3	1571
March	1st to 10th	Day	62% 4 8% 13% 10% 3	4796
	11th to 20th	Day	57% 5% 15% 15% 7% 1	4980
	21st to end	Day	65% 3 6% 14% 10% 1	5466
April	1st to 10th	Day	61% 5% 8% 13% 11% 2	2322
	11th to 20th	Day	53% 4 10% 19% 12% 1	2572
	21st to end	Day	54% 5% 10% 17% 12% 3	2600
May	1st to 10th	Day	64% 6% 9% 14% 7%	5897
	11th to 20th	Day	53% 6% 13% 20% 6% 1	6267
	21st to end	Day	52% 8% 12% 17% 11%	6982
June	1st to 10th	Day	57% 7% 10% 17% 9% 1	3000
	11th to 20th	Day	50% 6% 12% 20% 10% 1	3000
	21st to end	Day	57% 6% 11% 16% 9% 1	3000
July	1st to 10th	Day	52% 6% 14% 18% 9%	6745
	11th to 20th	Day	45% 6% 15% 24% 8% 1	6739
	21st to end	Day	44% 8% 15% 24% 9%	6303
August	1st to 10th	Day	54% 7% 11% 20% 8%	4222
	11th to 20th	Day	44% 7% 16% 24% 8%	4214
	21st to end	Day	36% 7% 14% 25% 17% 1	4644
September	1st to 10th	Day	40% 7% 13% 25% 15% 1	2400
	11th to 20th	Day	41% 4 12% 26% 15% 2	2207
	21st to end	Day	41% 5% 10% 25% 17% 1	2200
October	1st to 10th	Day	45% 6% 10% 28% 11%	3270
	11th to 20th	Day	48% 4 10% 30% 9%	3240
	21st to end	Day	42% 5% 16% 21% 16%	3394
November	1st to 10th	Day	54% 4 10% 21% 10% 1	1684
	11th to 20th	Day	52% 4 13% 17% 12% 1	1600
	21st to end	Day	59% 5% 12% 17% 7%	1600
December	1st to 10th	Day	57% 6% 13% 20% 4	2610
	11th to 20th	Day	57% 4 9% 15% 11% 3	2729
	21st to end	Day	53% 4 14% 17% 11% 2	3476
January	1st to 10th	Night	55% 6% 11% 22% 5% 1	6808
	11th to 20th	Night	55% 6% 12% 21% 7% 1	6458
	21st to end	Night	44% 5% 9% 21% 16% 4	6490
February	1st to 10th	Night	54% 5% 11% 15% 13% 2	2600
	11th to 20th	Night	57% 5% 10% 16% 10% 2	2536
	21st to end	Night	52% 5% 10% 18% 12% 3	2055
March	1st to 10th	Night	64% 3 6% 12% 11% 3	5056
	11th to 20th	Night	59% 5% 13% 13% 8% 1	4980
	21st to end	Night	63% 3 6% 16% 11% 1	5466
April	1st to 10th	Night	59% 5% 8% 14% 11% 4	2075
	11th to 20th	Night	53% 4 11% 19% 12% 1	1778
	21st to end	Night	55% 5% 10% 16% 13% 2	1800
May	1st to 10th	Night	62% 7% 9% 13% 8% 1	4060
	11th to 20th	Night	52% 7% 12% 21% 5% 2	3647
	21st to end	Night	52% 9% 12% 19% 7% 1	3949
June	1st to 10th	Night	58% 6% 9% 19% 7% 1	1409
	11th to 20th	Night	50% 6% 12% 22% 8% 2	1400
	21st to end	Night	60% 6% 8% 15% 9% 1	1400
July	1st to 10th	Night	59% 7% 12% 13% 9%	3125
	11th to 20th	Night	53% 8% 11% 21% 7%	3118
	21st to end	Night	45% 7% 16% 20% 11% 1	4174
August	1st to 10th	Night	58% 7% 11% 18% 6%	2903
	11th to 20th	Night	47% 9% 16% 20% 9%	2899
	21st to end	Night	38% 7% 16% 23% 16% 1	3252
September	1st to 10th	Night	41% 8% 10% 26% 14% 1	2000
	11th to 20th	Night	42% 4 13% 25% 15% 1	2190
	21st to end	Night	44% 5% 10% 25% 14% 2	2200
October	1st to 10th	Night	46% 5% 12% 24% 13% 1	3910
	11th to 20th	Night	43% 4 11% 26% 15%	3899
	21st to end	Night	47% 4 13% 22% 13%	4381
November	1st to 10th	Night	52% 5% 12% 20% 11% 1	2659
	11th to 20th	Night	55% 5% 11% 18% 10% 1	2800
	21st to end	Night	57% 5% 14% 16% 8%	2800
December	1st to 10th	Night	53% 5% 12% 22% 8%	4580
	11th to 20th	Night	55% 4 8% 18% 13% 2	5478
	21st to end	Night	56% 5% 9% 18% 10% 2	7502

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	36% 25% 31% 8% 1	200
	11th to 20th	Day	40% 23% 26% 8% 3	206
	21st to end	Day	23% 25% 34% 14% 4	440
February	1st to 10th	Day	34% 23% 26% 14% 3	400
	11th to 20th	Day	35% 27% 25% 10% 2 1	396
	21st to end	Day	30% 26% 28% 13% 3	375
March	1st to 10th	Day	32% 27% 28% 10% 2	500
	11th to 20th	Day	32% 24% 31% 10% 3 1	500
	21st to end	Day	41% 21% 25% 9% 3 1	550
April	1st to 10th	Day	43% 27% 21% 6% 3	500
	11th to 20th	Day	38% 26% 23% 9% 3	492
	21st to end	Day	36% 22% 28% 11% 3 1	500
May	1st to 10th	Day	39% 21% 26% 9% 4	503
	11th to 20th	Day	29% 20% 28% 17% 4	695
	21st to end	Day	31% 19% 30% 15% 4 1	790
June	1st to 10th	Day	32% 20% 28% 15% 4	730
	11th to 20th	Day	28% 19% 30% 18% 5%	730
	21st to end	Day	34% 16% 26% 18% 6%	730
July	1st to 10th	Day	26% 15% 34% 19% 6% 1	720
	11th to 20th	Day	24% 12% 34% 21% 8% 1	718
	21st to end	Day	21% 16% 40% 17% 5% 1	607
August	1st to 10th	Day	21% 14% 38% 21% 5% 1	526
	11th to 20th	Day	23% 12% 36% 22% 6% 2	519
	21st to end	Day	22% 16% 32% 21% 7% 2	583
September	1st to 10th	Day	17% 19% 38% 19% 7% 1	530
	11th to 20th	Day	24% 17% 28% 21% 7% 2	530
	21st to end	Day	25% 18% 30% 18% 6% 2	530
October	1st to 10th	Day	25% 17% 25% 22% 10% 2	425
	11th to 20th	Day	28% 20% 27% 17% 6% 2	420
	21st to end	Day	31% 21% 29% 14% 5%	462
November	1st to 10th	Day	33% 19% 28% 14% 5% 2	401
	11th to 20th	Day	36% 24% 22% 14% 4	400
	21st to end	Day	35% 24% 29% 10% 2 1	400
December	1st to 10th	Day	35% 21% 27% 14% 3	400
	11th to 20th	Day	41% 26% 21% 11% 1	272
	21st to end	Day	34% 26% 28% 9% 2	220
January	1st to 10th	Night	30% 23% 26% 18% 2	900
	11th to 20th	Night	31% 20% 26% 18% 5%	827
	21st to end	Night	22% 23% 33% 17% 5%	880
February	1st to 10th	Night	29% 23% 29% 17% 2	800
	11th to 20th	Night	30% 25% 27% 17% 2	783
	21st to end	Night	24% 22% 30% 21% 3	660
March	1st to 10th	Night	28% 21% 33% 17% 2	800
	11th to 20th	Night	29% 17% 31% 20% 4	800
	21st to end	Night	29% 21% 31% 14% 6%	880
April	1st to 10th	Night	36% 17% 29% 15% 3	682
	11th to 20th	Night	30% 18% 30% 18% 4	594
	21st to end	Night	32% 17% 31% 16% 5% 1	600
May	1st to 10th	Night	30% 16% 30% 20% 4 1	600
	11th to 20th	Night	31% 15% 31% 18% 4 1	592
	21st to end	Night	25% 16% 37% 17% 4	649
June	1st to 10th	Night	31% 11% 28% 26% 5%	409
	11th to 20th	Night	24% 13% 29% 29% 5%	400
	21st to end	Night	31% 9% 25% 29% 6%	400
July	1st to 10th	Night	24% 6% 37% 27% 6%	390
	11th to 20th	Night	25% 7% 29% 30% 7%	388
	21st to end	Night	23% 8% 33% 30% 6%	626
August	1st to 10th	Night	19% 9% 33% 32% 7%	598
	11th to 20th	Night	24% 7% 28% 32% 8% 1	592
	21st to end	Night	18% 11% 28% 30% 11%	660
September	1st to 10th	Night	21% 9% 36% 26% 8% 1	600
	11th to 20th	Night	24% 11% 23% 28% 14% 1	790
	21st to end	Night	25% 12% 27% 26% 10%	800
October	1st to 10th	Night	24% 11% 26% 28% 10% 1	800
	11th to 20th	Night	25% 16% 29% 20% 9% 1	800
	21st to end	Night	31% 18% 27% 20% 3	880
November	1st to 10th	Night	31% 17% 26% 19% 7% 1	836
	11th to 20th	Night	31% 20% 26% 17% 5% 1	900
	21st to end	Night	31% 22% 24% 18% 4	900
December	1st to 10th	Night	33% 19% 27% 17% 4	900
	11th to 20th	Night	34% 24% 26% 14% 2	900
	21st to end	Night	33% 23% 24% 17% 4	990

Page generated at 2025-10-31 03:02:36. Version ac07

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