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 2005-11-05 to 2024-10-14.

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 6% 7% 39%	101034
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 38%	97522
Transparency	Day	24% 49% 7% 12% 8% 1	100794
	Night	25% 50% 6% 11% 8% 1	97387
Seeing	Day	19% 7% 23% 32% 16% 3	14964
	Night	21% 8% 27% 30% 13% 2	23777

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	17% 7% 2 5% 3 3 3 3 5% 7% 44%	2517
	11th to 20th	Day	17% 7% 3 7% 4 3 4 3 4 6% 42%	2520
	21st to end	Day	20% 9% 3 6% 4 4 5% 3 4 5% 36%	2772
February	1st to 10th	Day	18% 7% 3 6% 4 4 4 4 6% 7% 37%	1737
	11th to 20th	Day	13% 7% 3 6% 5% 3 4 4 6% 7% 41%	1848
	21st to end	Day	15% 11% 3 6% 5% 3 4 4 5% 6% 38%	1570
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% 4 4 3 4 7% 46%	1784
	21st to end	Day	21% 7% 2 7% 3 4 4 3 5% 6% 40%	1782
November	1st to 10th	Day	17% 6% 2 5% 3 3 3 3 4 6% 49%	1671
	11th to 20th	Day	19% 6% 2 4 3 2 3 3 5% 6% 47%	1710
	21st to end	Day	20% 7% 2 5% 3 3 3 3 5% 6% 44%	1710
December	1st to 10th	Day	20% 7% 2 6% 3 4 4 4 6% 5% 39%	1560
	11th to 20th	Day	23% 6% 2 4 3 3 3 4 4 6% 43%	1906
	21st to end	Day	24% 9% 2 6% 5% 3 4 3 5% 5% 33%	2772
January	1st to 10th	Night	19% 8% 1 5% 3 3 3 3 4 6% 45%	4429
	11th to 20th	Night	15% 7% 3 8% 5% 4 4 3 5% 6% 39%	4440
	21st to end	Night	22% 11% 3 7% 4 5% 5% 3 4 6% 31%	4884
February	1st to 10th	Night	16% 9% 3 6% 5% 4 5% 4 6% 6% 37%	2440
	11th to 20th	Night	14% 9% 3 7% 5% 4 4 4 6% 5% 41%	2218
	21st to end	Night	17% 9% 2 5% 3 3 4 3 6% 6% 41%	1884
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% 6% 2 6% 4 5% 4 3 6% 6% 43%	2246
	21st to end	Night	23% 7% 2 5% 4 3 3 3 6% 6% 38%	2574
November	1st to 10th	Night	15% 6% 2 6% 3 4 4 3 5% 5% 46%	2407
	11th to 20th	Night	18% 7% 2 6% 3 4 3 3 4 5% 45%	2470
	21st to end	Night	17% 7% 2 4 4 3 4 3 5% 7% 44%	2470
December	1st to 10th	Night	20% 9% 3 6% 4 4 4 3 4 5% 38%	2617
	11th to 20th	Night	20% 6% 2 5% 4 3 3 3 5% 7% 40%	3288
	21st to end	Night	23% 9% 3 7% 4 4 4 3 4 6% 35%	4884

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	24% 39% 7% 22% 7% 1	2518
	11th to 20th	Day	26% 39% 6% 19% 9% 1	2520
	21st to end	Day	36% 42% 5% 13% 4	2772
February	1st to 10th	Day	17% 66% 5% 7% 5% 1	1737
	11th to 20th	Day	17% 64% 3 6% 8% 1	1857
	21st to end	Day	15% 65% 5% 8% 6% 2	1570
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	19% 60% 3 10% 6% 2	2090
	11th to 20th	Day	13% 62% 5% 13% 6% 1	1786
	21st to end	Day	20% 62% 4 9% 5% 1	1782
November	1st to 10th	Day	17% 59% 7% 10% 6% 1	1671
	11th to 20th	Day	17% 59% 3 8% 11% 1	1710
	21st to end	Day	16% 59% 6% 9% 9% 1	1710
December	1st to 10th	Day	20% 61% 6% 7% 7%	1560
	11th to 20th	Day	24% 49% 5% 9% 8% 4	1906
	21st to end	Day	34% 39% 6% 12% 7% 1	2772
January	1st to 10th	Night	24% 38% 9% 20% 7% 3	4429
	11th to 20th	Night	27% 38% 7% 16% 9% 2	4440
	21st to end	Night	39% 42% 6% 10% 3 1	4884
February	1st to 10th	Night	17% 66% 5% 6% 5% 2	2440
	11th to 20th	Night	17% 64% 3 7% 8% 1	2220
	21st to end	Night	16% 65% 3 8% 6% 3	1884
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	18% 60% 5% 11% 5% 2	2090
	11th to 20th	Night	12% 63% 6% 12% 6%	2249
	21st to end	Night	20% 63% 3 9% 4	2574
November	1st to 10th	Night	17% 60% 3 12% 6% 1	2407
	11th to 20th	Night	17% 59% 3 9% 10% 1	2470
	21st to end	Night	15% 60% 7% 11% 7% 1	2470
December	1st to 10th	Night	21% 61% 4 9% 6%	2617
	11th to 20th	Night	23% 50% 4 9% 13% 1	3288
	21st to end	Night	33% 38% 6% 16% 7%	4884

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% 13% 26% 28% 8%	180
	11th to 20th	Day	19% 18% 31% 24% 6% 1	180
	21st to end	Day	18% 10% 36% 28% 8% 1	198
February	1st to 10th	Day	25% 13% 35% 24% 2	363
	11th to 20th	Day	19% 14% 40% 23% 3	456
	21st to end	Day	20% 16% 31% 26% 7%	382
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	15% 7% 25% 31% 19% 2	394
	21st to end	Day	26% 5% 29% 28% 11% 1	396
November	1st to 10th	Day	17% 9% 27% 30% 16% 2	365
	11th to 20th	Day	25% 12% 28% 26% 8%	370
	21st to end	Day	25% 12% 26% 26% 9% 2	370
December	1st to 10th	Day	19% 8% 33% 32% 7% 1	220
	11th to 20th	Day	21% 16% 36% 25% 3	180
	21st to end	Day	24% 12% 31% 25% 8% 1	198
January	1st to 10th	Night	22% 15% 39% 20% 4	760
	11th to 20th	Night	24% 15% 36% 20% 4	760
	21st to end	Night	20% 14% 39% 22% 5%	836
February	1st to 10th	Night	21% 15% 36% 24% 3	760
	11th to 20th	Night	20% 14% 44% 19% 3	743
	21st to end	Night	21% 13% 34% 26% 6%	628
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	18% 6% 26% 35% 14% 2	735
	21st to end	Night	26% 8% 27% 29% 10%	792
November	1st to 10th	Night	18% 7% 32% 31% 11% 2	740
	11th to 20th	Night	21% 10% 34% 26% 7% 2	760
	21st to end	Night	20% 15% 32% 28% 5% 1	760
December	1st to 10th	Night	24% 11% 39% 21% 5%	760
	11th to 20th	Night	22% 13% 39% 23% 3	760
	21st to end	Night	26% 14% 33% 24% 3	836

Page generated at 2024-10-11 10:49:59. Version ac07

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