Rye Harbor State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rye Harbor State Park clear sky chart from 2005-11-06 to 2026-07-01.

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% 39%	137321
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 39%	135035
Transparency	Day	29% 37% 8% 15% 10% 2	140843
	Night	30% 36% 7% 15% 11% 2	139602
Seeing	Day	18% 7% 23% 32% 16% 3	17107
	Night	20% 8% 27% 30% 13% 2	25956

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% 7% 3 8% 5% 5% 5% 4 6% 8% 39%	4661
	11th to 20th	Day	16% 8% 2 6% 3 3 4 3 4 5% 45%	4650
	21st to end	Day	14% 7% 2 5% 3 4 4 3 4 5% 48%	5124
February	1st to 10th	Day	17% 7% 3 6% 4 4 4 4 6% 7% 38%	1921
	11th to 20th	Day	13% 7% 3 6% 5% 3 4 4 5% 7% 42%	2048
	21st to end	Day	15% 11% 3 6% 5% 3 4 4 5% 6% 38%	1730
March	1st to 10th	Day	21% 11% 2 6% 5% 4 4 4 5% 6% 34%	4576
	11th to 20th	Day	16% 10% 3 6% 4 4 3 4 5% 7% 38%	4939
	21st to end	Day	28% 8% 3 5% 3 4 4 3 5% 6% 32%	5813
April	1st to 10th	Day	19% 8% 3 7% 5% 5% 3 3 4 6% 37%	2520
	11th to 20th	Day	17% 7% 3 5% 4 4 5% 4 6% 7% 38%	2550
	21st to end	Day	19% 6% 3 6% 5% 5% 4 3 4 7% 38%	2730
May	1st to 10th	Day	26% 9% 2 7% 4 4 4 3 5% 6% 29%	7639
	11th to 20th	Day	19% 9% 2 8% 5% 4 4 3 5% 6% 35%	7719
	21st to end	Day	21% 7% 3 6% 4 5% 5% 4 5% 7% 33%	9060
June	1st to 10th	Day	19% 8% 2 6% 4 4 5% 4 6% 8% 34%	2940
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 6% 8% 41%	2940
	21st to end	Day	16% 6% 2 6% 5% 5% 5% 4 6% 8% 35%	2940
July	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 5% 7% 10% 32%	6360
	11th to 20th	Day	7% 7% 3 7% 4 5% 5% 5% 8% 10% 40%	6360
	21st to end	Day	14% 5% 2 5% 4 4 4 4 6% 8% 45%	6926
August	1st to 10th	Day	13% 6% 3 7% 5% 5% 6% 4 6% 7% 38%	4252
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 6% 7% 38%	4175
	21st to end	Day	8% 3 2 5% 3 4 6% 5% 8% 10% 47%	4356
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 7% 48%	2373
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 3 5% 55%	2200
	21st to end	Day	16% 6% 2 6% 3 3 4 3 4 8% 45%	2200
October	1st to 10th	Day	20% 6% 2 5% 3 4 3 3 4 6% 43%	2200
	11th to 20th	Day	16% 4 2 5% 5% 3 4 3 4 7% 46%	1944
	21st to end	Day	20% 7% 2 6% 3 4 4 3 5% 6% 42%	1980
November	1st to 10th	Day	16% 6% 2 5% 3 3 3 3 4 6% 49%	1851
	11th to 20th	Day	17% 6% 2 4 3 2 3 2 5% 6% 49%	1890
	21st to end	Day	20% 7% 2 5% 3 3 3 3 4 6% 43%	1890
December	1st to 10th	Day	15% 8% 2 5% 2 3 4 3 5% 6% 47%	2750
	11th to 20th	Day	20% 5% 2 4 3 3 3 3 4 6% 47%	3066
	21st to end	Day	21% 9% 3 6% 4 3 4 3 5% 5% 38%	4048
January	1st to 10th	Night	14% 7% 2 6% 4 4 3 3 5% 7% 46%	8234
	11th to 20th	Night	16% 10% 3 8% 5% 5% 4 3 5% 6% 36%	8235
	21st to end	Night	15% 9% 2 5% 4 5% 5% 3 5% 6% 42%	9057
February	1st to 10th	Night	16% 9% 3 6% 4 4 5% 4 6% 6% 38%	2695
	11th to 20th	Night	14% 9% 2 6% 4 4 4 4 6% 5% 41%	2458
	21st to end	Night	16% 9% 3 6% 4 3 4 3 6% 5% 41%	2076
March	1st to 10th	Night	26% 8% 2 5% 3 4 4 3 4 5% 36%	5484
	11th to 20th	Night	14% 10% 4 7% 5% 4 5% 4 5% 6% 36%	5238
	21st to end	Night	26% 8% 2 6% 4 3 4 3 6% 5% 32%	5358
April	1st to 10th	Night	20% 9% 2 6% 5% 3 3 4 4 6% 37%	2100
	11th to 20th	Night	20% 8% 3 6% 4 3 4 3 5% 6% 40%	2018
	21st to end	Night	21% 7% 3 7% 4 4 4 4 4 5% 38%	1890
May	1st to 10th	Night	27% 10% 3 7% 4 3 4 3 4 7% 29%	5259
	11th to 20th	Night	17% 9% 3 7% 5% 5% 5% 4 5% 8% 32%	5183
	21st to end	Night	21% 9% 3 8% 5% 4 4 4 6% 6% 31%	5114
June	1st to 10th	Night	20% 8% 3 7% 4 4 4 3 5% 6% 37%	1680
	11th to 20th	Night	17% 7% 2 6% 3 3 5% 5% 7% 8% 37%	1680
	21st to end	Night	19% 6% 2 6% 4 4 5% 4 6% 6% 36%	1680
July	1st to 10th	Night	12% 7% 3 7% 5% 5% 5% 4 7% 10% 36%	3600
	11th to 20th	Night	11% 8% 2 6% 4 5% 5% 4 7% 9% 38%	3600
	21st to end	Night	12% 5% 2 6% 4 4 4 4 6% 6% 47%	3926
August	1st to 10th	Night	19% 7% 3 7% 5% 5% 4 4 5% 6% 35%	2850
	11th to 20th	Night	14% 7% 2 8% 6% 5% 5% 5% 7% 8% 34%	2872
	21st to end	Night	10% 5% 2 4 3 4 4 4 7% 7% 50%	3538
September	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 5% 7% 49%	2026
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 5% 6% 52%	2200
	21st to end	Night	15% 6% 2 5% 5% 4 4 3 5% 7% 44%	2200
October	1st to 10th	Night	19% 5% 3 7% 4 3 3 4 4 6% 42%	2200
	11th to 20th	Night	15% 5% 2 6% 4 4 4 3 6% 7% 44%	2452
	21st to end	Night	22% 6% 2 5% 4 3 3 3 6% 6% 39%	2860
November	1st to 10th	Night	15% 6% 2 5% 3 4 4 3 5% 6% 47%	2667
	11th to 20th	Night	17% 6% 2 6% 3 4 4 3 4 6% 46%	2730
	21st to end	Night	17% 7% 2 5% 4 3 4 3 5% 7% 44%	2730
December	1st to 10th	Night	17% 9% 2 5% 4 4 4 3 4 6% 41%	4647
	11th to 20th	Night	22% 7% 2 6% 3 3 3 3 4 5% 42%	5348
	21st to end	Night	19% 9% 3 7% 4 4 4 3 4 5% 39%	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	35% 23% 9% 20% 13% 1	4662
	11th to 20th	Day	32% 22% 8% 20% 16% 2	4680
	21st to end	Day	31% 24% 6% 18% 18% 3	5124
February	1st to 10th	Day	19% 60% 5% 9% 7% 1	1921
	11th to 20th	Day	19% 59% 4 8% 9% 2	2057
	21st to end	Day	16% 60% 6% 9% 8% 2	1730
March	1st to 10th	Day	38% 30% 6% 9% 9% 9%	4579
	11th to 20th	Day	31% 32% 12% 16% 7% 2	4939
	21st to end	Day	40% 29% 4 10% 12% 5%	5813
April	1st to 10th	Day	22% 59% 3 7% 7% 2	2520
	11th to 20th	Day	17% 60% 5% 9% 7% 2	2550
	21st to end	Day	20% 59% 4 8% 9% 1	2730
May	1st to 10th	Day	44% 27% 9% 13% 6% 1	7651
	11th to 20th	Day	40% 25% 12% 16% 6% 1	7723
	21st to end	Day	39% 25% 9% 17% 8%	9061
June	1st to 10th	Day	17% 59% 6% 11% 7%	2940
	11th to 20th	Day	16% 60% 5% 10% 9% 1	2940
	21st to end	Day	18% 59% 5% 10% 7% 1	2940
July	1st to 10th	Day	37% 29% 9% 14% 10%	6290
	11th to 20th	Day	27% 30% 11% 19% 11%	6285
	21st to end	Day	28% 27% 10% 23% 11% 1	6728
August	1st to 10th	Day	29% 38% 10% 16% 6%	4238
	11th to 20th	Day	30% 38% 9% 18% 5%	4214
	21st to end	Day	16% 39% 11% 21% 13% 1	4356
September	1st to 10th	Day	14% 57% 6% 14% 9%	2373
	11th to 20th	Day	17% 57% 4 11% 10% 1	2200
	21st to end	Day	17% 58% 4 13% 8% 1	2200
October	1st to 10th	Day	26% 37% 5% 17% 13% 2	3590
	11th to 20th	Day	17% 36% 5% 22% 18% 2	3134
	21st to end	Day	18% 36% 5% 24% 16% 1	3180
November	1st to 10th	Day	19% 54% 7% 12% 8% 1	1851
	11th to 20th	Day	18% 54% 3 9% 14% 2	1890
	21st to end	Day	19% 54% 6% 11% 9% 1	1890
December	1st to 10th	Day	24% 36% 9% 24% 7%	2750
	11th to 20th	Day	27% 32% 10% 12% 14% 6%	3066
	21st to end	Day	36% 27% 5% 16% 11% 4	4048
January	1st to 10th	Night	31% 22% 9% 24% 12% 2	8234
	11th to 20th	Night	40% 22% 8% 15% 12% 4	8280
	21st to end	Night	35% 23% 6% 16% 16% 4	9057
February	1st to 10th	Night	19% 60% 5% 8% 6% 2	2695
	11th to 20th	Night	18% 58% 4 8% 9% 2	2460
	21st to end	Night	19% 59% 3 10% 6% 3	2076
March	1st to 10th	Night	39% 29% 6% 8% 11% 7%	5494
	11th to 20th	Night	34% 31% 11% 12% 10% 2	5239
	21st to end	Night	40% 30% 3 8% 14% 4	5358
April	1st to 10th	Night	22% 59% 3 6% 8% 2	2100
	11th to 20th	Night	20% 59% 4 8% 8% 1	2018
	21st to end	Night	20% 60% 3 6% 10% 1	1890
May	1st to 10th	Night	45% 26% 10% 10% 9%	5265
	11th to 20th	Night	40% 26% 11% 17% 7%	5184
	21st to end	Night	43% 25% 9% 16% 6%	5115
June	1st to 10th	Night	19% 59% 4 12% 7%	1680
	11th to 20th	Night	15% 60% 7% 10% 7% 1	1680
	21st to end	Night	19% 59% 4 11% 6% 1	1680
July	1st to 10th	Night	32% 29% 9% 18% 13%	3560
	11th to 20th	Night	31% 30% 11% 14% 13%	3552
	21st to end	Night	27% 28% 10% 24% 12%	3809
August	1st to 10th	Night	36% 37% 7% 12% 8% 1	2840
	11th to 20th	Night	29% 41% 10% 13% 6%	2899
	21st to end	Night	17% 38% 11% 17% 16%	3538
September	1st to 10th	Night	14% 57% 5% 13% 9% 1	2026
	11th to 20th	Night	17% 57% 3 11% 10% 1	2200
	21st to end	Night	18% 58% 4 13% 8% 1	2200
October	1st to 10th	Night	26% 38% 9% 16% 9% 2	3590
	11th to 20th	Night	14% 36% 6% 19% 22% 2	4001
	21st to end	Night	19% 37% 6% 24% 13% 2	4610
November	1st to 10th	Night	19% 54% 4 14% 8% 2	2667
	11th to 20th	Night	18% 54% 4 10% 12% 2	2730
	21st to end	Night	18% 55% 8% 12% 7% 1	2730
December	1st to 10th	Night	29% 35% 5% 22% 8%	4647
	11th to 20th	Night	33% 31% 7% 11% 16% 2	5348
	21st to end	Night	36% 27% 6% 16% 13% 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	21% 14% 29% 27% 9%	220
	11th to 20th	Day	19% 17% 32% 25% 6%	220
	21st to end	Day	17% 9% 41% 26% 7%	242
February	1st to 10th	Day	22% 13% 37% 24% 4	427
	11th to 20th	Day	18% 14% 39% 25% 4	536
	21st to end	Day	19% 14% 34% 27% 7%	446
March	1st to 10th	Day	22% 12% 32% 28% 6%	540
	11th to 20th	Day	17% 14% 37% 25% 7%	540
	21st to end	Day	22% 12% 33% 25% 7% 2	594
April	1st to 10th	Day	25% 9% 30% 26% 8% 2	540
	11th to 20th	Day	21% 7% 30% 32% 10% 1	532
	21st to end	Day	22% 4 25% 35% 12% 2	540
May	1st to 10th	Day	26% 5% 24% 35% 10% 1	543
	11th to 20th	Day	18% 5% 21% 39% 15% 2	567
	21st to end	Day	20% 4 17% 40% 17% 2	617
June	1st to 10th	Day	20% 2 15% 37% 22% 3	570
	11th to 20th	Day	14% 4 19% 39% 21% 3	570
	21st to end	Day	17% 4 16% 37% 22% 4	570
July	1st to 10th	Day	14% 3 10% 42% 26% 5%	525
	11th to 20th	Day	12% 3 10% 39% 31% 5%	524
	21st to end	Day	10% 2 11% 45% 29% 3	576
August	1st to 10th	Day	12% 2 12% 34% 35% 5%	526
	11th to 20th	Day	15% 3 10% 36% 27% 10%	519
	21st to end	Day	13% 2 11% 40% 26% 8%	583
September	1st to 10th	Day	15% 2 15% 32% 27% 8%	530
	11th to 20th	Day	16% 5% 16% 29% 23% 12%	530
	21st to end	Day	17% 3 19% 35% 19% 7%	530
October	1st to 10th	Day	21% 4 20% 27% 22% 6%	530
	11th to 20th	Day	17% 7% 24% 29% 20% 2	447
	21st to end	Day	24% 6% 28% 28% 13% 1	462
November	1st to 10th	Day	15% 10% 28% 32% 14% 2	425
	11th to 20th	Day	22% 11% 30% 29% 8%	430
	21st to end	Day	25% 13% 29% 24% 8% 1	430
December	1st to 10th	Day	17% 9% 33% 30% 9% 1	264
	11th to 20th	Day	20% 15% 37% 24% 3	220
	21st to end	Day	21% 12% 30% 27% 8% 1	242
January	1st to 10th	Night	21% 16% 40% 20% 4	840
	11th to 20th	Night	24% 15% 36% 20% 4	840
	21st to end	Night	19% 15% 41% 21% 5%	924
February	1st to 10th	Night	21% 15% 36% 25% 3	840
	11th to 20th	Night	20% 14% 44% 19% 4	823
	21st to end	Night	21% 12% 35% 26% 5%	692
March	1st to 10th	Night	25% 13% 36% 23% 4	840
	11th to 20th	Night	22% 11% 33% 26% 8%	840
	21st to end	Night	23% 9% 33% 27% 7% 1	924
April	1st to 10th	Night	25% 8% 29% 30% 8%	840
	11th to 20th	Night	23% 6% 28% 32% 10% 1	774
	21st to end	Night	23% 6% 24% 35% 11% 1	630
May	1st to 10th	Night	25% 4 23% 34% 12% 2	630
	11th to 20th	Night	21% 4 23% 36% 16% 1	609
	21st to end	Night	24% 2 13% 40% 17% 3	455
June	1st to 10th	Night	22% 4 11% 40% 20% 3	420
	11th to 20th	Night	20% 4 14% 40% 21% 1	420
	21st to end	Night	20% 3 10% 45% 20% 2	420
July	1st to 10th	Night	18% 1 9% 41% 28% 3	390
	11th to 20th	Night	13% 1 7% 42% 34% 3	388
	21st to end	Night	13% 3 8% 45% 29% 3	438
August	1st to 10th	Night	13% 1 8% 39% 35% 3	558
	11th to 20th	Night	12% 3 11% 38% 32% 4	592
	21st to end	Night	16% 2 11% 36% 30% 5%	845
September	1st to 10th	Night	14% 2 16% 36% 28% 4	800
	11th to 20th	Night	16% 3 16% 32% 25% 7%	800
	21st to end	Night	17% 3 17% 35% 24% 5%	800
October	1st to 10th	Night	21% 5% 22% 28% 21% 4	800
	11th to 20th	Night	17% 6% 26% 35% 14% 2	800
	21st to end	Night	25% 7% 28% 29% 11%	880
November	1st to 10th	Night	17% 8% 32% 31% 10% 1	820
	11th to 20th	Night	19% 10% 36% 26% 7% 1	840
	21st to end	Night	20% 15% 33% 27% 5% 1	840
December	1st to 10th	Night	24% 11% 39% 21% 5%	840
	11th to 20th	Night	22% 14% 39% 22% 3	840
	21st to end	Night	25% 15% 32% 24% 4	924

Page generated at 2026-06-28 02:10:42. Version ac07

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