Woonsocket
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woonsocket clear sky chart from 2005-11-06 to 2025-11-18.

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	18% 8% 2 6% 4 4 4 4 5% 7% 39%	126577
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 40%	123806
Transparency	Day	44% 5% 12% 21% 15% 3	130110
	Night	44% 5% 12% 21% 16% 3	128347
Seeing	Day	23% 18% 32% 18% 7% 2	16407
	Night	22% 15% 34% 22% 6%	25303

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% 8% 2 7% 4 4 3 3 5% 6% 46%	3597
	11th to 20th	Day	14% 8% 3 5% 4 3 4 3 4 4 48%	3570
	21st to end	Day	17% 8% 2 6% 3 4 4 3 4 5% 43%	3960
February	1st to 10th	Day	19% 7% 2 5% 5% 5% 6% 4 6% 7% 35%	1891
	11th to 20th	Day	14% 8% 3 6% 5% 4 4 4 5% 6% 40%	1948
	21st to end	Day	18% 10% 3 6% 4 4 4 3 4 5% 38%	1650
March	1st to 10th	Day	21% 11% 2 6% 3 3 4 3 5% 5% 36%	4476
	11th to 20th	Day	15% 8% 2 6% 5% 4 5% 4 5% 7% 41%	4749
	21st to end	Day	24% 10% 2 6% 3 4 4 4 5% 6% 32%	5800
April	1st to 10th	Day	19% 10% 3 6% 4 3 3 3 5% 6% 37%	2400
	11th to 20th	Day	18% 6% 2 5% 4 4 4 3 6% 8% 40%	2374
	21st to end	Day	21% 6% 2 7% 4 3 5% 4 4 6% 38%	2596
May	1st to 10th	Day	29% 11% 3 7% 4 4 4 3 4 7% 25%	5886
	11th to 20th	Day	21% 9% 3 8% 5% 5% 4 3 5% 6% 32%	5945
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 7% 36%	6949
June	1st to 10th	Day	18% 6% 2 6% 5% 5% 5% 4 6% 8% 34%	2800
	11th to 20th	Day	17% 6% 2 6% 5% 5% 5% 4 6% 8% 37%	2800
	21st to end	Day	16% 6% 3 6% 5% 4 5% 4 6% 9% 37%	2800
July	1st to 10th	Day	17% 6% 2 6% 5% 5% 5% 5% 7% 8% 33%	6360
	11th to 20th	Day	11% 7% 3 7% 5% 5% 6% 5% 7% 11% 35%	6360
	21st to end	Day	16% 6% 2 5% 4 4 4 4 5% 7% 42%	6926
August	1st to 10th	Day	16% 7% 3 8% 5% 6% 5% 4 6% 8% 33%	4276
	11th to 20th	Day	13% 7% 3 6% 4 5% 5% 4 6% 7% 40%	4078
	21st to end	Day	7% 4 2 5% 5% 5% 5% 5% 7% 8% 47%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 3 6% 5% 46%	2400
	11th to 20th	Day	15% 5% 2 4 4 3 4 2 4 6% 51%	2200
	21st to end	Day	19% 6% 2 5% 3 5% 3 3 4 6% 43%	2200
October	1st to 10th	Day	22% 7% 3 4 3 3 3 2 4 5% 44%	2200
	11th to 20th	Day	16% 6% 2 5% 3 3 4 3 4 7% 47%	1963
	21st to end	Day	20% 6% 2 5% 3 4 4 4 4 5% 42%	1980
November	1st to 10th	Day	15% 7% 2 5% 4 3 3 3 4 5% 49%	1851
	11th to 20th	Day	18% 6% 2 4 4 3 3 3 5% 6% 47%	1863
	21st to end	Day	18% 6% 2 5% 4 4 3 3 6% 6% 43%	1800
December	1st to 10th	Day	14% 9% 2 5% 3 3 4 3 4 6% 47%	2671
	11th to 20th	Day	18% 7% 2 4 3 3 3 2 4 5% 48%	2986
	21st to end	Day	20% 11% 3 6% 3 4 3 3 4 5% 38%	3960
January	1st to 10th	Night	14% 6% 2 4 3 3 3 3 5% 7% 49%	6349
	11th to 20th	Night	14% 10% 4 8% 4 3 3 3 4 5% 42%	6315
	21st to end	Night	17% 10% 3 7% 4 5% 4 3 4 5% 39%	6996
February	1st to 10th	Night	17% 9% 3 6% 4 4 3 4 5% 6% 39%	2503
	11th to 20th	Night	16% 8% 3 6% 4 4 4 5% 5% 6% 40%	2338
	21st to end	Night	18% 9% 3 6% 4 4 4 3 4 6% 40%	1980
March	1st to 10th	Night	23% 9% 2 4 3 3 4 3 5% 5% 39%	5364
	11th to 20th	Night	16% 10% 3 6% 4 4 4 3 4 6% 39%	5209
	21st to end	Night	25% 10% 2 6% 3 3 4 3 5% 5% 34%	5128
April	1st to 10th	Night	19% 8% 3 7% 4 5% 5% 3 5% 6% 36%	2000
	11th to 20th	Night	19% 8% 2 6% 5% 4 4 4 5% 5% 38%	1975
	21st to end	Night	20% 8% 3 6% 4 3 3 3 3 6% 41%	1802
May	1st to 10th	Night	30% 9% 3 7% 3 3 4 3 5% 6% 27%	4054
	11th to 20th	Night	19% 9% 3 8% 6% 6% 5% 4 6% 6% 28%	3990
	21st to end	Night	20% 8% 3 8% 5% 5% 4 4 5% 7% 33%	3926
June	1st to 10th	Night	16% 7% 3 6% 4 5% 5% 4 5% 7% 37%	1600
	11th to 20th	Night	19% 8% 2 4 5% 4 5% 3 5% 8% 36%	1600
	21st to end	Night	15% 6% 2 6% 3 4 3 4 6% 9% 41%	1600
July	1st to 10th	Night	14% 8% 3 7% 4 3 4 4 6% 10% 36%	3600
	11th to 20th	Night	14% 7% 2 7% 5% 4 5% 3 6% 9% 38%	3600
	21st to end	Night	14% 7% 2 6% 5% 5% 5% 3 5% 5% 43%	3926
August	1st to 10th	Night	20% 7% 3 7% 5% 4 5% 5% 6% 7% 30%	2840
	11th to 20th	Night	12% 7% 3 7% 6% 6% 6% 5% 6% 7% 35%	2965
	21st to end	Night	9% 4 2 4 3 3 3 3 5% 7% 56%	3586
September	1st to 10th	Night	12% 6% 2 7% 4 5% 4 4 5% 6% 44%	2000
	11th to 20th	Night	14% 6% 1 5% 3 3 3 2 4 6% 52%	2199
	21st to end	Night	19% 7% 3 6% 4 3 4 3 4 5% 42%	2200
October	1st to 10th	Night	20% 7% 2 5% 3 3 3 3 5% 5% 44%	2200
	11th to 20th	Night	16% 5% 2 5% 3 3 4 3 4 7% 48%	2433
	21st to end	Night	21% 7% 3 6% 4 4 4 2 4 5% 40%	2860
November	1st to 10th	Night	14% 6% 2 5% 4 4 3 3 5% 5% 49%	2667
	11th to 20th	Night	17% 7% 2 5% 4 3 4 3 4 5% 47%	2692
	21st to end	Night	17% 7% 2 4 4 3 4 3 5% 7% 45%	2600
December	1st to 10th	Night	17% 8% 2 5% 4 3 3 3 3 5% 47%	4505
	11th to 20th	Night	22% 8% 2 5% 3 3 3 3 4 4 41%	5208
	21st to end	Night	17% 11% 3 7% 3 3 3 3 4 5% 41%	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	38% 4 7% 27% 21% 3	3598
	11th to 20th	Day	39% 5% 10% 21% 18% 7%	3600
	21st to end	Day	43% 6% 9% 21% 19% 2	3960
February	1st to 10th	Day	46% 7% 13% 18% 14% 3	1891
	11th to 20th	Day	43% 6% 10% 21% 16% 4	1957
	21st to end	Day	48% 4 11% 19% 15% 3	1650
March	1st to 10th	Day	48% 4 11% 14% 12% 11%	4479
	11th to 20th	Day	40% 7% 14% 27% 10% 2	4749
	21st to end	Day	53% 5% 6% 15% 15% 7%	5800
April	1st to 10th	Day	47% 5% 11% 18% 16% 3	2400
	11th to 20th	Day	42% 6% 11% 20% 18% 3	2374
	21st to end	Day	46% 6% 9% 19% 17% 4	2596
May	1st to 10th	Day	58% 6% 14% 12% 8% 1	5897
	11th to 20th	Day	52% 6% 14% 16% 11% 2	5949
	21st to end	Day	46% 7% 12% 21% 13% 1	6949
June	1st to 10th	Day	45% 8% 13% 21% 12% 1	2800
	11th to 20th	Day	44% 8% 13% 20% 14% 2	2800
	21st to end	Day	43% 7% 14% 20% 14% 1	2800
July	1st to 10th	Day	49% 6% 11% 20% 13% 2	6290
	11th to 20th	Day	44% 5% 18% 22% 10% 1	6285
	21st to end	Day	42% 5% 11% 25% 16% 2	6728
August	1st to 10th	Day	49% 6% 16% 20% 8% 1	4262
	11th to 20th	Day	43% 5% 14% 27% 10%	4117
	21st to end	Day	33% 6% 14% 27% 18% 2	4312
September	1st to 10th	Day	38% 7% 11% 22% 20% 2	2400
	11th to 20th	Day	35% 5% 10% 24% 24% 3	2200
	21st to end	Day	43% 5% 9% 20% 22% 2	2200
October	1st to 10th	Day	40% 4 9% 22% 22% 4	3590
	11th to 20th	Day	31% 4 7% 25% 29% 4	3166
	21st to end	Day	32% 4 13% 28% 20% 3	3180
November	1st to 10th	Day	39% 5% 13% 22% 20% 2	1851
	11th to 20th	Day	38% 5% 10% 22% 21% 3	1863
	21st to end	Day	41% 5% 12% 27% 12% 3	1800
December	1st to 10th	Day	39% 4 14% 27% 14% 1	2671
	11th to 20th	Day	40% 3 14% 17% 19% 6%	2986
	21st to end	Day	48% 6% 8% 19% 15% 4	3960
January	1st to 10th	Night	35% 3 10% 33% 17% 2	6349
	11th to 20th	Night	45% 5% 11% 20% 14% 5%	6360
	21st to end	Night	48% 5% 9% 17% 17% 5%	6996
February	1st to 10th	Night	45% 6% 13% 21% 13% 2	2503
	11th to 20th	Night	44% 6% 10% 19% 17% 4	2340
	21st to end	Night	45% 4 9% 22% 16% 4	1980
March	1st to 10th	Night	47% 5% 9% 16% 16% 7%	5374
	11th to 20th	Night	45% 6% 17% 18% 12% 3	5210
	21st to end	Night	52% 4 6% 12% 20% 6%	5128
April	1st to 10th	Night	48% 5% 10% 19% 15% 3	2000
	11th to 20th	Night	46% 6% 9% 18% 18% 3	1975
	21st to end	Night	46% 6% 10% 18% 16% 4	1802
May	1st to 10th	Night	57% 8% 15% 11% 8% 1	4060
	11th to 20th	Night	53% 8% 15% 14% 8% 2	3991
	21st to end	Night	50% 8% 14% 18% 10% 1	3927
June	1st to 10th	Night	44% 9% 14% 20% 13% 1	1600
	11th to 20th	Night	45% 7% 13% 21% 13% 1	1600
	21st to end	Night	39% 9% 16% 23% 13% 1	1600
July	1st to 10th	Night	45% 7% 12% 23% 14%	3560
	11th to 20th	Night	45% 5% 18% 22% 10% 1	3552
	21st to end	Night	43% 5% 11% 26% 15% 1	3809
August	1st to 10th	Night	52% 7% 13% 18% 9% 1	2830
	11th to 20th	Night	45% 7% 14% 25% 9%	2992
	21st to end	Night	28% 5% 15% 29% 22% 1	3586
September	1st to 10th	Night	40% 6% 11% 23% 18% 2	2000
	11th to 20th	Night	34% 7% 9% 23% 26% 2	2199
	21st to end	Night	45% 6% 8% 20% 19% 2	2200
October	1st to 10th	Night	39% 5% 12% 24% 17% 3	3590
	11th to 20th	Night	27% 4 9% 27% 31% 3	3956
	21st to end	Night	35% 3 11% 28% 20% 2	4610
November	1st to 10th	Night	36% 7% 11% 23% 19% 3	2667
	11th to 20th	Night	41% 3 10% 22% 21% 4	2692
	21st to end	Night	39% 5% 13% 27% 14% 2	2600
December	1st to 10th	Night	42% 3 12% 28% 14% 1	4505
	11th to 20th	Night	46% 4 15% 14% 19% 2	5208
	21st to end	Night	45% 5% 8% 21% 17% 3	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	29% 28% 29% 13% 2	200
	11th to 20th	Day	30% 28% 34% 6% 4	200
	21st to end	Day	25% 30% 32% 10% 2 1	220
February	1st to 10th	Day	32% 25% 31% 11% 1	419
	11th to 20th	Day	31% 33% 27% 8% 1	496
	21st to end	Day	30% 25% 30% 12% 3	414
March	1st to 10th	Day	32% 21% 32% 12% 3	500
	11th to 20th	Day	29% 26% 30% 12% 3	500
	21st to end	Day	31% 23% 32% 10% 4 2	550
April	1st to 10th	Day	35% 23% 26% 11% 5% 1	500
	11th to 20th	Day	29% 26% 29% 12% 3 1	492
	21st to end	Day	28% 22% 31% 15% 2 2	500
May	1st to 10th	Day	31% 24% 28% 14% 3 1	503
	11th to 20th	Day	23% 18% 41% 14% 5%	527
	21st to end	Day	19% 16% 36% 22% 6% 2	573
June	1st to 10th	Day	21% 14% 36% 20% 8% 1	530
	11th to 20th	Day	18% 17% 38% 21% 5% 1	530
	21st to end	Day	17% 15% 36% 23% 7% 2	530
July	1st to 10th	Day	18% 9% 35% 24% 12% 2	525
	11th to 20th	Day	15% 8% 34% 27% 14% 2	524
	21st to end	Day	14% 8% 41% 26% 9% 1	576
August	1st to 10th	Day	11% 11% 34% 30% 11% 2	526
	11th to 20th	Day	14% 8% 33% 29% 12% 3	519
	21st to end	Day	11% 11% 36% 24% 12% 5%	583
September	1st to 10th	Day	18% 14% 28% 24% 13% 4	530
	11th to 20th	Day	18% 11% 27% 25% 11% 7%	530
	21st to end	Day	23% 12% 33% 21% 9% 3	530
October	1st to 10th	Day	27% 12% 26% 20% 10% 5%	530
	11th to 20th	Day	20% 17% 33% 17% 9% 3	477
	21st to end	Day	25% 18% 31% 18% 8% 1	462
November	1st to 10th	Day	23% 17% 34% 16% 8% 2	425
	11th to 20th	Day	27% 24% 29% 15% 5%	421
	21st to end	Day	27% 21% 31% 15% 6% 1	400
December	1st to 10th	Day	22% 31% 30% 13% 4	245
	11th to 20th	Day	31% 28% 32% 7% 2 1	200
	21st to end	Day	25% 27% 32% 10% 3 3	220
January	1st to 10th	Night	23% 21% 38% 15% 3	800
	11th to 20th	Night	28% 20% 35% 15% 2	800
	21st to end	Night	21% 23% 35% 18% 3	880
February	1st to 10th	Night	25% 19% 37% 18% 1	800
	11th to 20th	Night	26% 23% 36% 13% 1	783
	21st to end	Night	26% 21% 34% 15% 3	660
March	1st to 10th	Night	26% 21% 34% 16% 3	800
	11th to 20th	Night	21% 24% 36% 17% 3	800
	21st to end	Night	27% 20% 35% 15% 4	880
April	1st to 10th	Night	25% 22% 33% 17% 3	800
	11th to 20th	Night	24% 21% 35% 17% 4	791
	21st to end	Night	24% 19% 39% 16% 3	602
May	1st to 10th	Night	31% 15% 32% 20% 3	600
	11th to 20th	Night	22% 17% 39% 20% 3	575
	21st to end	Night	18% 9% 39% 29% 5%	433
June	1st to 10th	Night	18% 8% 37% 30% 8%	400
	11th to 20th	Night	19% 7% 38% 31% 5%	400
	21st to end	Night	16% 6% 40% 32% 6%	400
July	1st to 10th	Night	14% 5% 33% 39% 8%	390
	11th to 20th	Night	16% 4 31% 38% 11% 1	388
	21st to end	Night	13% 6% 36% 38% 7%	438
August	1st to 10th	Night	14% 5% 34% 39% 8%	548
	11th to 20th	Night	14% 5% 29% 40% 11%	646
	21st to end	Night	14% 6% 28% 37% 13% 2	880
September	1st to 10th	Night	16% 6% 33% 34% 11% 1	800
	11th to 20th	Night	17% 7% 28% 29% 17% 2	800
	21st to end	Night	23% 8% 28% 28% 11% 2	800
October	1st to 10th	Night	25% 11% 28% 24% 12% 2	800
	11th to 20th	Night	20% 12% 34% 23% 11% 1	800
	21st to end	Night	26% 16% 33% 19% 7%	880
November	1st to 10th	Night	18% 17% 33% 23% 9% 1	820
	11th to 20th	Night	23% 19% 35% 16% 6%	829
	21st to end	Night	23% 21% 32% 20% 4 1	800
December	1st to 10th	Night	26% 18% 34% 18% 4	800
	11th to 20th	Night	27% 19% 33% 20% 2	800
	21st to end	Night	25% 20% 35% 18% 3	880

Page generated at 2025-11-15 00:55:59. Version ac07

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