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 2025-02-25.

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%	108393
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 39%	110271
Transparency	Day	24% 45% 7% 13% 9% 1	111961
	Night	26% 43% 6% 13% 10% 2	114867
Seeing	Day	19% 7% 23% 32% 16% 3	15322
	Night	21% 8% 27% 30% 13% 2	24313

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% 8% 40%	3597
	11th to 20th	Day	14% 7% 2 6% 4 3 4 3 4 6% 47%	3570
	21st to end	Day	16% 7% 2 5% 4 4 4 3 4 5% 46%	3960
February	1st to 10th	Day	18% 7% 3 6% 4 4 4 4 6% 7% 38%	1829
	11th to 20th	Day	14% 7% 3 6% 5% 3 4 4 5% 7% 41%	1948
	21st to end	Day	15% 11% 3 6% 5% 3 4 4 6% 6% 38%	1610
March	1st to 10th	Day	25% 12% 2 6% 5% 3 4 3 5% 5% 29%	3116
	11th to 20th	Day	15% 7% 3 6% 4 4 4 4 5% 7% 41%	3374
	21st to end	Day	24% 8% 3 5% 3 4 4 3 5% 5% 35%	3967
April	1st to 10th	Day	19% 8% 3 7% 5% 5% 3 3 4 6% 37%	2280
	11th to 20th	Day	17% 7% 3 5% 4 4 5% 4 6% 7% 38%	2304
	21st to end	Day	19% 6% 3 6% 5% 4 5% 4 4 7% 37%	2470
May	1st to 10th	Day	21% 10% 3 8% 5% 4 4 4 6% 7% 30%	4106
	11th to 20th	Day	22% 8% 2 8% 5% 4 3 3 4 7% 34%	4133
	21st to end	Day	16% 5% 2 4 4 4 5% 4 5% 8% 43%	4837
June	1st to 10th	Day	20% 8% 2 6% 5% 4 5% 4 5% 7% 34%	2660
	11th to 20th	Day	15% 6% 2 6% 4 5% 4 4 6% 8% 41%	2660
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 6% 8% 34%	2660
July	1st to 10th	Day	11% 7% 3 7% 5% 5% 5% 5% 8% 10% 34%	4440
	11th to 20th	Day	8% 6% 2 6% 4 5% 5% 4 8% 10% 42%	4440
	21st to end	Day	16% 6% 2 6% 5% 4 4 4 7% 8% 38%	4814
August	1st to 10th	Day	13% 6% 3 7% 5% 5% 6% 4 6% 7% 37%	4121
	11th to 20th	Day	15% 8% 3 8% 4 4 4 4 6% 7% 37%	4045
	21st to end	Day	8% 3 2 5% 3 4 6% 5% 8% 10% 47%	4223
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 7% 48%	2255
	11th to 20th	Day	14% 5% 2 5% 3 3 3 3 3 5% 55%	2090
	21st to end	Day	16% 6% 2 6% 3 3 4 3 4 8% 45%	2090
October	1st to 10th	Day	21% 6% 2 5% 3 5% 3 3 4 6% 41%	2090
	11th to 20th	Day	15% 4 2 5% 5% 3 4 3 4 7% 47%	1848
	21st to end	Day	20% 7% 2 7% 3 4 4 3 5% 6% 41%	1881
November	1st to 10th	Day	16% 6% 2 5% 3 3 3 3 4 6% 49%	1761
	11th to 20th	Day	18% 6% 2 4 3 2 3 2 5% 6% 49%	1800
	21st to end	Day	20% 7% 2 5% 3 3 3 3 5% 6% 43%	1800
December	1st to 10th	Day	15% 8% 2 5% 2 3 4 3 5% 6% 47%	2668
	11th to 20th	Day	21% 5% 2 4 3 3 3 3 4 6% 47%	2986
	21st to end	Day	22% 9% 3 6% 4 3 4 3 5% 5% 38%	3960
January	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 5% 7% 46%	6349
	11th to 20th	Night	14% 8% 3 8% 5% 5% 4 3 5% 6% 38%	6315
	21st to end	Night	16% 9% 2 6% 4 5% 5% 3 5% 6% 39%	6996
February	1st to 10th	Night	16% 9% 3 6% 5% 4 4 4 5% 6% 37%	2567
	11th to 20th	Night	14% 9% 2 7% 4 4 4 4 6% 5% 41%	2338
	21st to end	Night	17% 9% 3 5% 3 3 4 3 6% 6% 41%	1939
March	1st to 10th	Night	30% 9% 2 5% 3 3 3 2 4 4 33%	3724
	11th to 20th	Night	13% 8% 3 8% 6% 5% 5% 4 5% 6% 37%	3583
	21st to end	Night	26% 8% 3 6% 4 3 4 4 6% 5% 33%	3662
April	1st to 10th	Night	19% 10% 2 6% 5% 3 4 4 5% 6% 37%	1900
	11th to 20th	Night	19% 8% 3 5% 4 3 4 4 5% 6% 40%	1824
	21st to end	Night	22% 7% 2 6% 4 4 4 4 4 5% 37%	1710
May	1st to 10th	Night	23% 12% 3 8% 4 4 5% 3 5% 8% 26%	2834
	11th to 20th	Night	19% 9% 3 7% 6% 5% 5% 5% 5% 8% 27%	2789
	21st to end	Night	18% 7% 3 6% 4 3 4 3 5% 6% 41%	2738
June	1st to 10th	Night	20% 8% 3 7% 4 4 4 3 5% 6% 36%	1520
	11th to 20th	Night	18% 8% 2 6% 4 3 5% 4 7% 8% 37%	1520
	21st to end	Night	19% 6% 3 6% 4 4 4 4 6% 7% 36%	1520
July	1st to 10th	Night	11% 7% 3 8% 5% 6% 5% 4 7% 10% 34%	2520
	11th to 20th	Night	10% 5% 2 6% 5% 5% 6% 4 8% 9% 39%	2520
	21st to end	Night	16% 7% 3 7% 5% 4 4 4 6% 7% 38%	2739
August	1st to 10th	Night	19% 7% 3 8% 5% 5% 5% 4 5% 6% 34%	2762
	11th to 20th	Night	14% 7% 2 8% 6% 5% 5% 5% 7% 8% 33%	2782
	21st to end	Night	10% 5% 2 4 3 4 4 4 7% 7% 50%	3430
September	1st to 10th	Night	12% 6% 2 6% 4 3 3 3 5% 7% 49%	1924
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 6% 52%	2090
	21st to end	Night	15% 6% 2 5% 4 4 4 3 5% 7% 45%	2090
October	1st to 10th	Night	20% 5% 3 7% 5% 3 3 4 5% 6% 40%	2090
	11th to 20th	Night	15% 5% 2 6% 4 5% 4 3 6% 6% 45%	2329
	21st to end	Night	22% 7% 2 5% 4 3 3 3 6% 6% 39%	2717
November	1st to 10th	Night	14% 5% 2 5% 3 4 4 3 5% 6% 47%	2537
	11th to 20th	Night	17% 6% 2 6% 3 4 3 3 4 5% 46%	2600
	21st to end	Night	17% 7% 2 4 4 3 4 3 5% 6% 44%	2600
December	1st to 10th	Night	17% 10% 2 5% 4 4 4 3 4 5% 41%	4509
	11th to 20th	Night	22% 7% 2 6% 3 3 3 3 4 5% 42%	5208
	21st to end	Night	19% 9% 3 7% 4 4 4 3 4 5% 39%	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	31% 28% 7% 20% 13% 1	3598
	11th to 20th	Day	26% 28% 9% 21% 14% 2	3600
	21st to end	Day	32% 30% 4 15% 16% 3	3960
February	1st to 10th	Day	18% 63% 5% 7% 6% 1	1829
	11th to 20th	Day	18% 61% 4 7% 8% 2	1957
	21st to end	Day	15% 64% 5% 9% 7% 2	1610
March	1st to 10th	Day	39% 41% 5% 7% 8% 1	3119
	11th to 20th	Day	20% 44% 11% 13% 9% 3	3374
	21st to end	Day	34% 41% 3 8% 10% 4	3967
April	1st to 10th	Day	19% 64% 2 7% 6% 2	2280
	11th to 20th	Day	14% 66% 5% 8% 5% 1	2304
	21st to end	Day	18% 65% 4 6% 8%	2470
May	1st to 10th	Day	33% 45% 8% 10% 4	4120
	11th to 20th	Day	34% 42% 12% 9% 3	4137
	21st to end	Day	22% 42% 10% 14% 12%	4837
June	1st to 10th	Day	15% 65% 5% 9% 6%	2660
	11th to 20th	Day	13% 65% 4 8% 8% 1	2660
	21st to end	Day	16% 65% 4 8% 7%	2660
July	1st to 10th	Day	30% 39% 7% 12% 11% 1	4370
	11th to 20th	Day	22% 39% 11% 18% 10%	4365
	21st to end	Day	29% 38% 9% 15% 8% 1	4661
August	1st to 10th	Day	30% 39% 10% 16% 5%	4107
	11th to 20th	Day	30% 39% 9% 17% 4	4084
	21st to end	Day	16% 40% 11% 21% 12% 1	4223
September	1st to 10th	Day	13% 60% 5% 13% 9%	2255
	11th to 20th	Day	16% 60% 4 10% 9% 1	2090
	21st to end	Day	16% 60% 4 12% 8% 1	2090
October	1st to 10th	Day	27% 38% 6% 16% 12% 1	3480
	11th to 20th	Day	16% 37% 4 21% 19% 2	3038
	21st to end	Day	18% 37% 5% 23% 16% 1	3081
November	1st to 10th	Day	17% 56% 7% 11% 7% 1	1761
	11th to 20th	Day	17% 56% 3 8% 14% 2	1800
	21st to end	Day	18% 57% 6% 10% 9% 1	1800
December	1st to 10th	Day	23% 37% 9% 24% 6%	2668
	11th to 20th	Day	26% 32% 10% 12% 14% 6%	2986
	21st to end	Day	36% 28% 5% 16% 11% 4	3960
January	1st to 10th	Night	27% 27% 8% 25% 11% 2	6349
	11th to 20th	Night	35% 28% 9% 16% 10% 2	6360
	21st to end	Night	35% 30% 6% 12% 12% 5%	6996
February	1st to 10th	Night	18% 63% 5% 7% 6% 2	2567
	11th to 20th	Night	18% 61% 4 7% 9% 2	2340
	21st to end	Night	16% 63% 3 10% 6% 3	1939
March	1st to 10th	Night	37% 41% 6% 8% 6% 2	3734
	11th to 20th	Night	25% 44% 7% 10% 12% 2	3584
	21st to end	Night	34% 42% 3 7% 9% 5%	3662
April	1st to 10th	Night	19% 65% 2 5% 7% 1	1900
	11th to 20th	Night	16% 65% 3 7% 7% 1	1824
	21st to end	Night	17% 65% 3 6% 8% 1	1710
May	1st to 10th	Night	36% 45% 8% 8% 3	2840
	11th to 20th	Night	34% 44% 11% 7% 3	2790
	21st to end	Night	27% 43% 10% 11% 9% 1	2739
June	1st to 10th	Night	17% 65% 3 9% 6%	1520
	11th to 20th	Night	13% 66% 6% 9% 6% 1	1520
	21st to end	Night	16% 65% 4 10% 6% 1	1520
July	1st to 10th	Night	28% 39% 8% 14% 11%	2480
	11th to 20th	Night	25% 40% 9% 15% 11%	2472
	21st to end	Night	30% 37% 7% 14% 10%	2651
August	1st to 10th	Night	36% 39% 7% 11% 7% 1	2752
	11th to 20th	Night	29% 42% 10% 12% 6%	2809
	21st to end	Night	17% 39% 11% 17% 16%	3430
September	1st to 10th	Night	14% 60% 5% 12% 8% 1	1924
	11th to 20th	Night	16% 60% 3 10% 9% 1	2090
	21st to end	Night	16% 60% 3 12% 7% 1	2090
October	1st to 10th	Night	27% 39% 10% 15% 8% 1	3480
	11th to 20th	Night	13% 37% 6% 19% 22% 2	3878
	21st to end	Night	18% 37% 7% 23% 13% 2	4467
November	1st to 10th	Night	17% 57% 4 13% 7% 2	2537
	11th to 20th	Night	17% 56% 3 10% 12% 2	2600
	21st to end	Night	17% 57% 7% 11% 7% 1	2600
December	1st to 10th	Night	29% 36% 5% 22% 8%	4509
	11th to 20th	Night	33% 32% 7% 11% 16% 1	5208
	21st to end	Night	35% 28% 6% 17% 13% 1	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	23% 15% 29% 27% 7%	200
	11th to 20th	Day	19% 17% 32% 26% 7% 1	200
	21st to end	Day	17% 9% 39% 27% 7%	220
February	1st to 10th	Day	24% 13% 36% 24% 3	395
	11th to 20th	Day	19% 15% 40% 23% 3	496
	21st to end	Day	19% 15% 31% 27% 7%	398
March	1st to 10th	Day	23% 12% 32% 27% 6%	460
	11th to 20th	Day	18% 13% 37% 25% 6%	460
	21st to end	Day	21% 12% 32% 25% 8% 2	506
April	1st to 10th	Day	24% 9% 30% 26% 9% 2	460
	11th to 20th	Day	21% 7% 30% 30% 11% 1	452
	21st to end	Day	23% 5% 25% 35% 11% 2	460
May	1st to 10th	Day	24% 5% 25% 34% 10% 1	463
	11th to 20th	Day	18% 5% 22% 38% 15% 2	487
	21st to end	Day	19% 3 17% 41% 17% 3	529
June	1st to 10th	Day	21% 2 17% 38% 20% 2	490
	11th to 20th	Day	14% 4 19% 39% 20% 4	490
	21st to end	Day	17% 4 18% 38% 19% 4	490
July	1st to 10th	Day	14% 3 10% 41% 26% 6%	485
	11th to 20th	Day	13% 3 10% 40% 30% 5%	484
	21st to end	Day	11% 2 11% 45% 28% 4	532
August	1st to 10th	Day	13% 2 13% 34% 35% 4	486
	11th to 20th	Day	16% 3 10% 37% 26% 8%	479
	21st to end	Day	14% 2 11% 39% 27% 8%	539
September	1st to 10th	Day	16% 2 15% 31% 28% 8%	490
	11th to 20th	Day	17% 5% 17% 29% 21% 11%	490
	21st to end	Day	17% 3 20% 35% 18% 7%	490
October	1st to 10th	Day	22% 4 20% 27% 22% 5%	490
	11th to 20th	Day	16% 7% 25% 29% 20% 3	415
	21st to end	Day	25% 5% 28% 29% 13% 1	429
November	1st to 10th	Day	15% 9% 28% 32% 15% 2	395
	11th to 20th	Day	24% 11% 29% 28% 7%	400
	21st to end	Day	26% 13% 27% 25% 9% 2	400
December	1st to 10th	Day	17% 9% 33% 31% 8% 1	242
	11th to 20th	Day	21% 15% 37% 25% 4	200
	21st to end	Day	22% 12% 29% 27% 9% 1	220
January	1st to 10th	Night	21% 16% 39% 20% 4	800
	11th to 20th	Night	24% 14% 36% 21% 5%	800
	21st to end	Night	19% 14% 41% 21% 5%	880
February	1st to 10th	Night	22% 16% 36% 24% 3	800
	11th to 20th	Night	20% 15% 44% 18% 3	783
	21st to end	Night	21% 12% 34% 26% 6%	647
March	1st to 10th	Night	25% 12% 36% 23% 4	760
	11th to 20th	Night	22% 10% 35% 25% 8% 1	760
	21st to end	Night	23% 9% 32% 28% 7% 1	836
April	1st to 10th	Night	25% 7% 29% 31% 8%	760
	11th to 20th	Night	22% 6% 28% 31% 12% 1	700
	21st to end	Night	24% 5% 24% 34% 11% 1	570
May	1st to 10th	Night	25% 3 24% 34% 12% 2	570
	11th to 20th	Night	21% 4 23% 35% 15% 1	551
	21st to end	Night	24% 2 14% 39% 18% 3	411
June	1st to 10th	Night	23% 4 11% 41% 18% 3	380
	11th to 20th	Night	21% 4 12% 41% 20% 2	380
	21st to end	Night	21% 2 10% 45% 19% 2	380
July	1st to 10th	Night	18% 1 9% 40% 28% 3	370
	11th to 20th	Night	14% 1 6% 43% 33% 3	368
	21st to end	Night	13% 3 8% 43% 30% 3	416
August	1st to 10th	Night	14% 1 8% 40% 34% 3	530
	11th to 20th	Night	13% 3 11% 38% 31% 4	562
	21st to end	Night	17% 2 11% 34% 31% 5%	803
September	1st to 10th	Night	14% 2 16% 36% 28% 4	760
	11th to 20th	Night	17% 3 17% 31% 24% 7%	760
	21st to end	Night	17% 3 18% 34% 23% 5%	760
October	1st to 10th	Night	22% 5% 21% 28% 20% 4	760
	11th to 20th	Night	17% 6% 26% 34% 14% 2	760
	21st to end	Night	25% 7% 28% 29% 11%	836
November	1st to 10th	Night	17% 7% 32% 32% 11% 2	780
	11th to 20th	Night	20% 10% 35% 27% 7% 2	800
	21st to end	Night	20% 15% 32% 27% 5% 1	800
December	1st to 10th	Night	24% 10% 39% 21% 6%	800
	11th to 20th	Night	23% 13% 38% 23% 3	800
	21st to end	Night	25% 14% 32% 24% 4	880

Page generated at 2025-02-22 06:51:39. Version ac07

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