Caumsett State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caumsett State Park clear sky chart from 2005-11-06 to 2026-04-17.

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	15% 7% 2 6% 4 4 4 4 6% 8% 41%	131346
	Night	16% 8% 3 6% 4 4 4 3 5% 6% 42%	130816
Transparency	Day	41% 6% 12% 23% 16% 2	134873
	Night	42% 5% 11% 23% 16% 3	135376
Seeing	Day	18% 12% 29% 26% 12% 2	16828
	Night	20% 12% 31% 27% 9% 1	26042

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	13% 6% 2 5% 4 4 4 3 5% 7% 48%	4661
	11th to 20th	Day	16% 8% 2 5% 4 4 4 3 4 5% 45%	4650
	21st to end	Day	16% 7% 3 7% 4 4 5% 4 5% 6% 42%	5459
February	1st to 10th	Day	16% 7% 3 6% 4 4 4 4 5% 7% 41%	1939
	11th to 20th	Day	15% 6% 3 7% 4 4 4 3 4 7% 44%	2048
	21st to end	Day	19% 7% 2 6% 4 4 3 3 5% 6% 41%	1730
March	1st to 10th	Day	20% 8% 2 5% 3 3 3 3 4 5% 43%	4576
	11th to 20th	Day	11% 8% 3 5% 4 4 5% 4 6% 8% 43%	4810
	21st to end	Day	17% 7% 2 6% 4 3 4 3 5% 7% 42%	6102
April	1st to 10th	Day	17% 8% 2 6% 4 3 4 3 6% 7% 39%	2520
	11th to 20th	Day	16% 6% 2 6% 4 4 4 3 6% 7% 42%	2446
	21st to end	Day	18% 6% 2 5% 4 4 5% 3 5% 7% 43%	2461
May	1st to 10th	Day	26% 9% 2 5% 3 3 4 3 6% 8% 30%	5886
	11th to 20th	Day	20% 9% 3 6% 4 4 3 3 5% 6% 37%	6175
	21st to end	Day	20% 6% 2 5% 4 4 4 4 6% 8% 38%	6949
June	1st to 10th	Day	16% 6% 2 5% 4 4 4 4 6% 9% 41%	2800
	11th to 20th	Day	14% 7% 2 5% 5% 4 5% 4 6% 9% 40%	2800
	21st to end	Day	10% 7% 2 6% 4 4 5% 5% 6% 9% 43%	2800
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 5% 7% 10% 36%	6360
	11th to 20th	Day	8% 6% 3 7% 5% 5% 6% 5% 8% 11% 35%	6360
	21st to end	Day	12% 7% 2 6% 4 5% 5% 4 6% 9% 40%	6926
August	1st to 10th	Day	16% 7% 3 7% 4 5% 5% 4 6% 10% 34%	4324
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 9% 43%	3850
	21st to end	Day	8% 5% 2 6% 4 4 4 4 6% 10% 48%	4312
September	1st to 10th	Day	14% 5% 2 5% 4 4 4 3 5% 8% 47%	2400
	11th to 20th	Day	11% 6% 2 4 3 4 4 3 5% 7% 52%	2285
	21st to end	Day	17% 6% 3 7% 5% 4 4 3 5% 6% 41%	2200
October	1st to 10th	Day	19% 7% 2 5% 2 3 3 4 4 7% 45%	2132
	11th to 20th	Day	14% 6% 2 5% 4 4 4 4 4 7% 47%	2000
	21st to end	Day	19% 6% 2 5% 4 4 4 3 4 6% 43%	2005
November	1st to 10th	Day	13% 6% 2 5% 4 3 3 4 5% 6% 51%	1851
	11th to 20th	Day	16% 6% 2 5% 3 3 3 3 5% 6% 48%	1890
	21st to end	Day	15% 7% 2 5% 4 3 5% 3 5% 6% 44%	1845
December	1st to 10th	Day	14% 7% 3 5% 4 4 4 3 6% 7% 43%	2680
	11th to 20th	Day	21% 6% 2 5% 3 2 3 2 4 5% 46%	3066
	21st to end	Day	17% 9% 3 7% 4 4 4 3 4 5% 38%	4048
January	1st to 10th	Night	13% 8% 3 6% 3 4 3 2 5% 6% 47%	8234
	11th to 20th	Night	16% 9% 3 6% 3 3 3 2 4 5% 45%	8235
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 42%	8719
February	1st to 10th	Night	16% 9% 2 5% 4 4 4 3 5% 5% 42%	2679
	11th to 20th	Night	18% 8% 3 5% 4 3 4 4 5% 7% 39%	2458
	21st to end	Night	19% 8% 2 5% 4 4 5% 3 5% 5% 41%	2076
March	1st to 10th	Night	19% 9% 3 5% 3 3 3 3 4 5% 43%	5484
	11th to 20th	Night	14% 10% 2 6% 5% 4 4 3 5% 6% 43%	5365
	21st to end	Night	19% 9% 3 6% 4 4 3 3 5% 6% 38%	5072
April	1st to 10th	Night	19% 8% 2 6% 4 5% 4 4 5% 6% 38%	2100
	11th to 20th	Night	19% 7% 2 6% 4 3 4 4 4 7% 40%	2036
	21st to end	Night	18% 7% 3 6% 5% 3 4 3 4 6% 42%	1937
May	1st to 10th	Night	26% 10% 3 7% 5% 4 3 3 5% 7% 27%	4054
	11th to 20th	Night	22% 10% 3 6% 4 4 3 3 5% 6% 35%	3760
	21st to end	Night	22% 8% 2 5% 4 4 4 3 5% 7% 36%	3926
June	1st to 10th	Night	16% 7% 2 6% 4 4 4 5% 5% 7% 41%	1600
	11th to 20th	Night	14% 7% 3 6% 3 4 4 4 8% 8% 40%	1600
	21st to end	Night	10% 5% 2 6% 4 5% 6% 4 7% 10% 41%	1600
July	1st to 10th	Night	9% 9% 3 8% 6% 5% 5% 5% 6% 9% 35%	3600
	11th to 20th	Night	11% 9% 4 8% 5% 6% 6% 5% 7% 9% 32%	3600
	21st to end	Night	12% 7% 3 6% 4 4 4 3 6% 9% 41%	3926
August	1st to 10th	Night	21% 7% 2 7% 5% 4 5% 3 7% 7% 32%	2774
	11th to 20th	Night	13% 7% 3 7% 4 4 5% 4 6% 8% 38%	3197
	21st to end	Night	8% 4 2 5% 3 4 5% 3 6% 8% 51%	3586
September	1st to 10th	Night	13% 5% 2 6% 4 4 4 5% 6% 7% 44%	2000
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 5% 6% 51%	2113
	21st to end	Night	17% 6% 2 6% 5% 3 3 3 5% 7% 43%	2200
October	1st to 10th	Night	17% 8% 2 6% 4 4 3 3 4 6% 42%	2265
	11th to 20th	Night	15% 5% 2 5% 3 3 4 3 4 6% 49%	2400
	21st to end	Night	20% 6% 2 6% 3 3 3 3 4 6% 42%	2833
November	1st to 10th	Night	12% 5% 2 6% 3 3 4 3 5% 6% 49%	2667
	11th to 20th	Night	17% 7% 2 4 3 2 3 3 4 5% 48%	2730
	21st to end	Night	14% 6% 2 5% 4 4 3 4 5% 6% 47%	2772
December	1st to 10th	Night	16% 6% 2 5% 3 4 3 3 5% 5% 47%	4720
	11th to 20th	Night	23% 8% 2 5% 3 3 3 3 4 4 43%	5348
	21st to end	Night	18% 9% 3 6% 4 4 4 3 4 5% 41%	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	36% 5% 10% 30% 18% 2	4662
	11th to 20th	Day	41% 3 9% 23% 17% 6%	4680
	21st to end	Day	43% 4 10% 26% 16% 1	5459
February	1st to 10th	Day	44% 5% 12% 23% 14% 2	1939
	11th to 20th	Day	42% 4 9% 25% 16% 2	2057
	21st to end	Day	46% 4 10% 23% 15% 2	1730
March	1st to 10th	Day	42% 5% 11% 19% 14% 8%	4579
	11th to 20th	Day	37% 7% 13% 28% 12% 2	4810
	21st to end	Day	42% 5% 10% 14% 22% 6%	6102
April	1st to 10th	Day	44% 5% 9% 22% 16% 4	2520
	11th to 20th	Day	41% 5% 12% 22% 17% 3	2446
	21st to end	Day	41% 6% 10% 22% 17% 4	2461
May	1st to 10th	Day	53% 6% 16% 14% 10% 1	5897
	11th to 20th	Day	48% 6% 11% 20% 14% 2	6179
	21st to end	Day	43% 7% 11% 23% 14% 1	6949
June	1st to 10th	Day	40% 7% 12% 23% 16% 1	2800
	11th to 20th	Day	42% 6% 13% 24% 13% 2	2800
	21st to end	Day	38% 8% 15% 23% 15% 1	2800
July	1st to 10th	Day	42% 10% 13% 21% 15% 1	6290
	11th to 20th	Day	40% 9% 19% 21% 10% 1	6285
	21st to end	Day	40% 7% 12% 21% 19% 1	6728
August	1st to 10th	Day	45% 7% 15% 23% 9% 1	4310
	11th to 20th	Day	37% 7% 13% 32% 10% 1	3886
	21st to end	Day	31% 6% 13% 27% 20% 2	4312
September	1st to 10th	Day	37% 6% 13% 23% 19% 2	2400
	11th to 20th	Day	32% 5% 11% 25% 24% 2	2285
	21st to end	Day	45% 5% 10% 19% 18% 3	2200
October	1st to 10th	Day	34% 7% 11% 19% 24% 5%	3470
	11th to 20th	Day	27% 4 10% 23% 31% 5%	3240
	21st to end	Day	29% 4 14% 26% 24% 3	3217
November	1st to 10th	Day	36% 4 13% 23% 22% 2	1851
	11th to 20th	Day	38% 3 10% 23% 23% 3	1890
	21st to end	Day	40% 5% 13% 28% 12% 2	1845
December	1st to 10th	Day	40% 4 16% 28% 12% 1	2680
	11th to 20th	Day	42% 4 13% 22% 17% 2	3066
	21st to end	Day	47% 5% 9% 22% 15% 2	4048
January	1st to 10th	Night	39% 3 11% 25% 20% 3	8234
	11th to 20th	Night	42% 3 11% 21% 17% 5%	8280
	21st to end	Night	44% 3 8% 22% 19% 4	8719
February	1st to 10th	Night	44% 4 12% 25% 13% 2	2679
	11th to 20th	Night	45% 4 9% 21% 16% 4	2460
	21st to end	Night	45% 4 7% 24% 16% 4	2076
March	1st to 10th	Night	45% 3 10% 21% 14% 8%	5494
	11th to 20th	Night	42% 5% 12% 25% 12% 4	5366
	21st to end	Night	48% 4 6% 14% 23% 5%	5072
April	1st to 10th	Night	47% 5% 10% 18% 17% 4	2100
	11th to 20th	Night	44% 6% 10% 18% 21% 2	2036
	21st to end	Night	44% 4 9% 21% 18% 5%	1937
May	1st to 10th	Night	57% 5% 13% 14% 10% 1	4060
	11th to 20th	Night	52% 5% 13% 15% 13% 2	3761
	21st to end	Night	48% 6% 12% 22% 11% 1	3927
June	1st to 10th	Night	43% 6% 9% 21% 20% 1	1600
	11th to 20th	Night	41% 7% 14% 26% 12% 1	1600
	21st to end	Night	38% 8% 13% 26% 13% 2	1600
July	1st to 10th	Night	46% 8% 12% 21% 11% 1	3560
	11th to 20th	Night	46% 8% 15% 20% 10% 1	3552
	21st to end	Night	38% 7% 15% 23% 16% 1	3809
August	1st to 10th	Night	50% 6% 17% 17% 9% 1	2764
	11th to 20th	Night	41% 7% 14% 28% 9% 1	3227
	21st to end	Night	29% 6% 13% 32% 18% 1	3586
September	1st to 10th	Night	39% 6% 10% 26% 18% 1	2000
	11th to 20th	Night	34% 5% 10% 25% 23% 3	2113
	21st to end	Night	43% 6% 7% 21% 19% 3	2200
October	1st to 10th	Night	39% 5% 10% 24% 19% 3	3707
	11th to 20th	Night	24% 4 10% 28% 30% 4	3899
	21st to end	Night	31% 4 13% 29% 21% 2	4571
November	1st to 10th	Night	36% 5% 10% 24% 21% 4	2667
	11th to 20th	Night	39% 4 8% 24% 20% 5%	2730
	21st to end	Night	38% 4 12% 30% 14% 2	2772
December	1st to 10th	Night	39% 4 12% 30% 13% 2	4720
	11th to 20th	Night	46% 3 9% 24% 15% 3	5348
	21st to end	Night	45% 4 9% 21% 16% 4	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	24% 25% 32% 16% 4	220
	11th to 20th	Day	20% 32% 31% 14% 2	220
	21st to end	Day	21% 20% 39% 15% 4 1	303
February	1st to 10th	Day	23% 16% 44% 15% 2	379
	11th to 20th	Day	22% 20% 39% 17% 2	536
	21st to end	Day	24% 21% 34% 17% 5%	446
March	1st to 10th	Day	16% 21% 37% 21% 4	540
	11th to 20th	Day	19% 16% 40% 21% 3 1	540
	21st to end	Day	23% 21% 35% 16% 5% 1	594
April	1st to 10th	Day	23% 21% 34% 15% 7% 1	540
	11th to 20th	Day	20% 17% 32% 22% 8% 1	516
	21st to end	Day	24% 13% 34% 23% 5% 1	500
May	1st to 10th	Day	27% 13% 31% 22% 7% 1	503
	11th to 20th	Day	18% 11% 30% 31% 9% 1	527
	21st to end	Day	18% 6% 22% 31% 21% 2	573
June	1st to 10th	Day	18% 6% 24% 34% 16% 2	530
	11th to 20th	Day	16% 8% 28% 32% 13% 2	530
	21st to end	Day	12% 5% 29% 32% 19% 2	530
July	1st to 10th	Day	11% 5% 20% 36% 23% 5%	525
	11th to 20th	Day	9% 5% 22% 36% 23% 5%	524
	21st to end	Day	12% 5% 22% 40% 18% 3	576
August	1st to 10th	Day	11% 7% 19% 36% 21% 5%	526
	11th to 20th	Day	13% 3 20% 37% 24% 3	519
	21st to end	Day	10% 6% 25% 35% 19% 6%	583
September	1st to 10th	Day	17% 6% 26% 26% 20% 6%	530
	11th to 20th	Day	14% 5% 21% 31% 21% 8%	530
	21st to end	Day	22% 6% 28% 27% 13% 4	530
October	1st to 10th	Day	24% 8% 24% 23% 17% 5%	530
	11th to 20th	Day	17% 14% 30% 25% 12% 2	530
	21st to end	Day	21% 14% 31% 23% 9% 2	476
November	1st to 10th	Day	16% 14% 29% 29% 10% 2	425
	11th to 20th	Day	20% 21% 32% 22% 5%	430
	21st to end	Day	21% 19% 31% 22% 6% 1	385
December	1st to 10th	Day	22% 18% 37% 18% 5%	220
	11th to 20th	Day	29% 24% 30% 15% 3	220
	21st to end	Day	24% 20% 35% 12% 7%	242
January	1st to 10th	Night	19% 20% 38% 19% 3	840
	11th to 20th	Night	25% 18% 32% 23% 2	840
	21st to end	Night	20% 18% 40% 20% 2	924
February	1st to 10th	Night	21% 17% 38% 22% 2	840
	11th to 20th	Night	24% 18% 38% 18% 1	823
	21st to end	Night	22% 20% 35% 19% 4	692
March	1st to 10th	Night	22% 17% 36% 21% 5%	840
	11th to 20th	Night	21% 15% 39% 20% 4 1	840
	21st to end	Night	22% 16% 39% 18% 4	924
April	1st to 10th	Night	24% 15% 35% 21% 5%	840
	11th to 20th	Night	21% 14% 33% 26% 6%	816
	21st to end	Night	21% 11% 36% 26% 6% 1	737
May	1st to 10th	Night	25% 9% 33% 26% 7% 1	600
	11th to 20th	Night	22% 9% 36% 27% 5%	475
	21st to end	Night	21% 6% 20% 37% 14% 2	433
June	1st to 10th	Night	19% 7% 26% 34% 15%	400
	11th to 20th	Night	17% 5% 23% 40% 14% 1	400
	21st to end	Night	10% 5% 23% 49% 12% 1	400
July	1st to 10th	Night	11% 4 24% 42% 17% 1	390
	11th to 20th	Night	12% 6% 19% 41% 19% 3	388
	21st to end	Night	13% 3 21% 46% 16% 1	438
August	1st to 10th	Night	12% 3 21% 44% 19% 1	508
	11th to 20th	Night	14% 4 18% 37% 25% 2	790
	21st to end	Night	13% 5% 19% 38% 23% 3	880
September	1st to 10th	Night	15% 4 26% 34% 18% 3	800
	11th to 20th	Night	15% 5% 21% 35% 20% 5%	800
	21st to end	Night	21% 5% 24% 31% 17% 2	800
October	1st to 10th	Night	21% 8% 26% 28% 15% 3	800
	11th to 20th	Night	19% 12% 28% 30% 11% 1	800
	21st to end	Night	23% 12% 33% 24% 7%	880
November	1st to 10th	Night	15% 12% 34% 28% 10% 2	820
	11th to 20th	Night	22% 16% 33% 21% 8%	840
	21st to end	Night	18% 17% 33% 25% 6% 1	840
December	1st to 10th	Night	25% 17% 34% 18% 5% 1	840
	11th to 20th	Night	24% 15% 37% 20% 3	840
	21st to end	Night	24% 15% 38% 20% 3	924

Page generated at 2026-04-14 02:44:23. Version ac07

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