Ward Pound Ridge Reservation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ward Pound Ridge Reservation clear sky chart from 2005-11-06 to 2025-08-05.

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% 38%	125697
	Night	17% 8% 3 6% 4 4 4 3 5% 6% 42%	122334
Transparency	Day	42% 7% 12% 22% 15% 3	129211
	Night	42% 5% 11% 22% 16% 3	126894
Seeing	Day	24% 17% 31% 19% 8% 2	15927
	Night	23% 15% 31% 24% 7% 1	24976

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% 8% 2 6% 5% 4 4 3 5% 5% 45%	3597
	11th to 20th	Day	14% 10% 3 7% 5% 5% 4 3 4 5% 41%	3570
	21st to end	Day	18% 8% 3 7% 5% 4 4 3 5% 5% 39%	4208
February	1st to 10th	Day	16% 8% 3 6% 6% 5% 5% 4 5% 6% 37%	1827
	11th to 20th	Day	15% 7% 3 7% 5% 4 4 3 5% 6% 41%	1948
	21st to end	Day	19% 10% 2 6% 4 4 3 4 3 7% 38%	1650
March	1st to 10th	Day	22% 8% 3 6% 4 4 3 3 4 5% 40%	4476
	11th to 20th	Day	13% 6% 3 6% 4 4 5% 4 6% 7% 42%	4694
	21st to end	Day	19% 7% 3 6% 4 4 4 3 5% 6% 39%	5970
April	1st to 10th	Day	19% 9% 3 6% 4 3 4 3 5% 7% 36%	2400
	11th to 20th	Day	18% 7% 2 5% 4 4 4 3 5% 6% 40%	2374
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 6% 40%	2463
May	1st to 10th	Day	29% 8% 2 6% 4 4 4 3 5% 8% 26%	5886
	11th to 20th	Day	20% 10% 3 7% 4 4 4 4 5% 6% 34%	6241
	21st to end	Day	21% 7% 2 6% 4 4 5% 4 6% 7% 34%	6949
June	1st to 10th	Day	18% 6% 2 5% 4 4 5% 4 7% 8% 36%	2800
	11th to 20th	Day	17% 7% 3 6% 4 4 5% 4 6% 8% 36%	2800
	21st to end	Day	13% 6% 2 6% 5% 6% 5% 4 6% 9% 37%	2800
July	1st to 10th	Day	12% 7% 3 8% 6% 4 6% 4 7% 10% 34%	6360
	11th to 20th	Day	12% 7% 2 7% 5% 5% 6% 5% 8% 11% 32%	6360
	21st to end	Day	14% 7% 2 6% 5% 5% 5% 4 6% 7% 39%	6926
August	1st to 10th	Day	21% 7% 2 7% 4 5% 5% 5% 6% 8% 32%	4283
	11th to 20th	Day	12% 6% 2 7% 5% 4 4 4 6% 8% 41%	3730
	21st to end	Day	10% 6% 2 6% 4 4 4 3 6% 10% 45%	4180
September	1st to 10th	Day	14% 6% 1 7% 5% 4 5% 3 5% 7% 43%	2280
	11th to 20th	Day	13% 6% 2 5% 3 4 3 3 5% 7% 49%	2179
	21st to end	Day	17% 5% 3 8% 5% 4 4 4 5% 6% 40%	2090
October	1st to 10th	Day	21% 6% 2 6% 4 3 4 2 5% 5% 41%	2013
	11th to 20th	Day	15% 5% 2 5% 3 4 3 4 5% 7% 47%	1900
	21st to end	Day	22% 5% 1 5% 4 5% 4 3 5% 6% 41%	1906
November	1st to 10th	Day	14% 6% 2 5% 3 3 3 3 5% 6% 51%	1761
	11th to 20th	Day	19% 5% 2 4 4 2 3 4 4 5% 48%	1800
	21st to end	Day	17% 6% 2 5% 4 3 4 3 4 7% 43%	1730
December	1st to 10th	Day	15% 8% 3 6% 4 4 4 3 5% 8% 42%	2600
	11th to 20th	Day	20% 8% 2 5% 3 2 3 2 4 5% 45%	2986
	21st to end	Day	18% 9% 3 7% 4 4 4 3 4 6% 37%	3960
January	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	6349
	11th to 20th	Night	13% 8% 3 7% 4 3 4 3 5% 5% 45%	6315
	21st to end	Night	16% 9% 3 7% 4 4 4 4 4 5% 40%	6745
February	1st to 10th	Night	16% 9% 3 7% 4 3 4 3 4 6% 41%	2571
	11th to 20th	Night	17% 8% 3 6% 5% 3 3 3 5% 6% 41%	2338
	21st to end	Night	18% 8% 3 6% 4 4 4 3 4 4 42%	1980
March	1st to 10th	Night	19% 9% 2 5% 3 3 3 3 4 6% 42%	5364
	11th to 20th	Night	15% 8% 3 6% 4 4 4 3 4 6% 43%	5245
	21st to end	Night	18% 10% 3 7% 4 4 3 3 4 5% 39%	4962
April	1st to 10th	Night	19% 8% 2 6% 5% 4 3 3 6% 7% 36%	2000
	11th to 20th	Night	20% 7% 3 6% 3 3 4 3 5% 7% 38%	1975
	21st to end	Night	19% 6% 3 6% 5% 3 3 3 5% 5% 41%	1935
May	1st to 10th	Night	29% 10% 3 7% 4 3 4 3 5% 6% 26%	4054
	11th to 20th	Night	21% 10% 3 6% 4 4 4 4 5% 6% 34%	3681
	21st to end	Night	22% 7% 3 6% 4 3 4 3 5% 7% 37%	3926
June	1st to 10th	Night	17% 5% 2 6% 5% 4 5% 3 5% 8% 41%	1600
	11th to 20th	Night	15% 6% 3 6% 5% 4 4 4 6% 8% 41%	1600
	21st to end	Night	13% 6% 2 5% 4 4 4 5% 6% 9% 43%	1600
July	1st to 10th	Night	13% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	3600
	11th to 20th	Night	15% 9% 3 8% 4 5% 5% 3 7% 8% 33%	3600
	21st to end	Night	14% 7% 2 5% 3 3 4 3 6% 6% 45%	3926
August	1st to 10th	Night	22% 6% 3 7% 6% 4 5% 4 5% 7% 32%	2685
	11th to 20th	Night	15% 7% 3 7% 5% 5% 5% 3 5% 7% 39%	3097
	21st to end	Night	11% 5% 2 5% 3 3 4 3 5% 7% 53%	3476
September	1st to 10th	Night	15% 7% 2 6% 4 3 4 2 5% 6% 46%	1900
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 7% 52%	2000
	21st to end	Night	17% 7% 3 6% 3 3 5% 3 4 5% 44%	2090
October	1st to 10th	Night	19% 8% 3 6% 4 3 3 2 4 6% 43%	2164
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 7% 49%	2280
	21st to end	Night	21% 7% 2 5% 3 2 3 3 5% 6% 41%	2690
November	1st to 10th	Night	12% 5% 2 6% 3 3 4 4 5% 6% 50%	2537
	11th to 20th	Night	19% 7% 2 4 3 3 3 2 4 6% 47%	2600
	21st to end	Night	15% 6% 2 5% 4 3 4 3 5% 7% 46%	2665
December	1st to 10th	Night	16% 8% 2 5% 4 3 3 2 4 5% 47%	4580
	11th to 20th	Night	23% 9% 2 4 3 3 3 3 4 4 41%	5208
	21st to end	Night	19% 9% 3 7% 4 3 3 3 4 5% 40%	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	36% 6% 8% 29% 17% 3	3598
	11th to 20th	Day	44% 5% 10% 22% 13% 6%	3600
	21st to end	Day	46% 6% 9% 23% 15% 1	4208
February	1st to 10th	Day	46% 5% 12% 22% 13% 2	1827
	11th to 20th	Day	43% 4 10% 23% 17% 3	1957
	21st to end	Day	46% 5% 10% 22% 15% 3	1650
March	1st to 10th	Day	44% 5% 12% 17% 13% 9%	4479
	11th to 20th	Day	37% 6% 16% 27% 10% 3	4694
	21st to end	Day	45% 5% 9% 13% 22% 6%	5970
April	1st to 10th	Day	46% 5% 9% 20% 15% 4	2400
	11th to 20th	Day	43% 5% 11% 19% 19% 3	2374
	21st to end	Day	43% 6% 10% 22% 16% 3	2463
May	1st to 10th	Day	55% 8% 13% 14% 10% 1	5897
	11th to 20th	Day	48% 8% 10% 19% 13% 2	6245
	21st to end	Day	45% 8% 11% 22% 13% 1	6949
June	1st to 10th	Day	42% 9% 12% 21% 15% 1	2800
	11th to 20th	Day	44% 7% 14% 23% 12% 1	2800
	21st to end	Day	41% 9% 13% 22% 14% 1	2800
July	1st to 10th	Day	44% 10% 11% 20% 14% 1	6290
	11th to 20th	Day	41% 9% 18% 21% 10% 1	6285
	21st to end	Day	41% 8% 11% 21% 18% 1	6728
August	1st to 10th	Day	49% 8% 13% 21% 9% 1	4269
	11th to 20th	Day	38% 7% 16% 29% 10% 1	3766
	21st to end	Day	33% 7% 13% 28% 18% 1	4180
September	1st to 10th	Day	40% 7% 10% 23% 18% 2	2280
	11th to 20th	Day	34% 5% 11% 23% 26% 1	2179
	21st to end	Day	45% 5% 9% 21% 17% 3	2090
October	1st to 10th	Day	36% 6% 10% 19% 24% 5%	3338
	11th to 20th	Day	27% 5% 10% 25% 29% 5%	3140
	21st to end	Day	30% 4 15% 24% 24% 4	3118
November	1st to 10th	Day	34% 4 13% 25% 21% 3	1761
	11th to 20th	Day	38% 4 10% 23% 21% 4	1800
	21st to end	Day	41% 4 13% 27% 12% 2	1730
December	1st to 10th	Day	41% 5% 15% 27% 11% 1	2600
	11th to 20th	Day	43% 4 13% 21% 17% 3	2986
	21st to end	Day	47% 6% 8% 20% 16% 3	3960
January	1st to 10th	Night	35% 6% 9% 26% 21% 3	6349
	11th to 20th	Night	39% 5% 14% 21% 15% 6%	6360
	21st to end	Night	46% 5% 10% 19% 16% 4	6745
February	1st to 10th	Night	45% 5% 12% 24% 12% 2	2571
	11th to 20th	Night	44% 5% 10% 19% 18% 5%	2340
	21st to end	Night	45% 4 8% 23% 17% 4	1980
March	1st to 10th	Night	43% 4 11% 19% 15% 8%	5374
	11th to 20th	Night	40% 6% 14% 23% 12% 4	5246
	21st to end	Night	47% 5% 6% 14% 24% 5%	4962
April	1st to 10th	Night	47% 5% 11% 20% 15% 3	2000
	11th to 20th	Night	45% 5% 10% 19% 20% 1	1975
	21st to end	Night	43% 6% 9% 20% 18% 4	1935
May	1st to 10th	Night	57% 7% 12% 13% 10% 1	4060
	11th to 20th	Night	49% 8% 12% 14% 14% 2	3682
	21st to end	Night	47% 6% 13% 22% 11% 2	3927
June	1st to 10th	Night	42% 8% 9% 22% 18% 2	1600
	11th to 20th	Night	40% 8% 16% 25% 11% 1	1600
	21st to end	Night	36% 10% 13% 26% 14% 2	1600
July	1st to 10th	Night	44% 8% 13% 20% 14% 2	3560
	11th to 20th	Night	47% 8% 15% 20% 10%	3552
	21st to end	Night	37% 6% 13% 23% 19% 1	3809
August	1st to 10th	Night	51% 9% 14% 16% 10% 1	2675
	11th to 20th	Night	43% 7% 13% 28% 9% 1	3127
	21st to end	Night	29% 7% 13% 33% 17% 1	3476
September	1st to 10th	Night	39% 6% 9% 26% 19% 1	1900
	11th to 20th	Night	33% 5% 10% 25% 25% 3	2000
	21st to end	Night	41% 7% 7% 22% 21% 2	2090
October	1st to 10th	Night	40% 6% 11% 22% 19% 2	3606
	11th to 20th	Night	25% 4 10% 28% 29% 4	3779
	21st to end	Night	32% 5% 13% 29% 19% 3	4428
November	1st to 10th	Night	34% 5% 12% 23% 22% 4	2537
	11th to 20th	Night	40% 3 8% 24% 20% 5%	2600
	21st to end	Night	38% 4 13% 30% 13% 1	2665
December	1st to 10th	Night	40% 3 12% 31% 13% 1	4580
	11th to 20th	Night	47% 3 11% 20% 16% 3	5208
	21st to end	Night	45% 4 10% 19% 17% 4	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	36% 25% 26% 12% 3	200
	11th to 20th	Day	32% 25% 32% 10% 2	200
	21st to end	Day	25% 30% 32% 8% 4	273
February	1st to 10th	Day	34% 27% 29% 9%	327
	11th to 20th	Day	32% 27% 31% 9% 1	496
	21st to end	Day	33% 24% 31% 11% 2	414
March	1st to 10th	Day	31% 21% 33% 13% 3	500
	11th to 20th	Day	28% 26% 31% 12% 2 1	500
	21st to end	Day	32% 23% 30% 11% 3 1	550
April	1st to 10th	Day	34% 25% 25% 10% 5%	500
	11th to 20th	Day	29% 26% 27% 11% 6% 1	492
	21st to end	Day	30% 17% 34% 14% 4 1	500
May	1st to 10th	Day	36% 17% 30% 12% 5% 1	503
	11th to 20th	Day	25% 15% 36% 18% 5% 1	527
	21st to end	Day	23% 11% 30% 25% 9% 2	573
June	1st to 10th	Day	21% 12% 32% 24% 9% 2	530
	11th to 20th	Day	20% 13% 33% 24% 10% 1	530
	21st to end	Day	16% 12% 30% 29% 11% 1	530
July	1st to 10th	Day	16% 9% 32% 27% 14% 3	525
	11th to 20th	Day	12% 8% 32% 29% 16% 3	524
	21st to end	Day	14% 8% 35% 30% 12% 1	576
August	1st to 10th	Day	15% 8% 29% 30% 13% 5%	502
	11th to 20th	Day	15% 6% 29% 30% 15% 5%	479
	21st to end	Day	12% 11% 29% 27% 14% 7%	539
September	1st to 10th	Day	18% 12% 28% 21% 17% 4	490
	11th to 20th	Day	15% 8% 30% 27% 10% 10%	490
	21st to end	Day	21% 14% 33% 17% 11% 4	490
October	1st to 10th	Day	28% 12% 26% 18% 13% 3	490
	11th to 20th	Day	18% 20% 32% 21% 8% 2	490
	21st to end	Day	29% 13% 31% 18% 7% 1	442
November	1st to 10th	Day	19% 19% 29% 22% 9% 2	395
	11th to 20th	Day	27% 22% 30% 16% 6%	400
	21st to end	Day	28% 21% 30% 16% 4 1	330
December	1st to 10th	Day	30% 22% 32% 13% 4	200
	11th to 20th	Day	38% 22% 29% 8% 3	200
	21st to end	Day	28% 22% 30% 15% 5%	220
January	1st to 10th	Night	25% 20% 35% 17% 3	800
	11th to 20th	Night	27% 20% 31% 20% 2	800
	21st to end	Night	23% 21% 36% 17% 2	880
February	1st to 10th	Night	25% 19% 36% 19% 1	800
	11th to 20th	Night	28% 23% 34% 14% 1	783
	21st to end	Night	28% 21% 32% 17% 2	660
March	1st to 10th	Night	27% 21% 32% 17% 3	800
	11th to 20th	Night	24% 22% 34% 17% 3	800
	21st to end	Night	25% 20% 35% 16% 3	880
April	1st to 10th	Night	28% 20% 32% 16% 3	800
	11th to 20th	Night	25% 18% 35% 18% 3	791
	21st to end	Night	25% 18% 34% 18% 4	735
May	1st to 10th	Night	28% 15% 33% 19% 5%	600
	11th to 20th	Night	23% 15% 34% 21% 5%	448
	21st to end	Night	23% 7% 27% 32% 10% 1	433
June	1st to 10th	Night	18% 9% 30% 33% 11%	400
	11th to 20th	Night	18% 6% 31% 34% 12%	400
	21st to end	Night	15% 4 28% 44% 10%	400
July	1st to 10th	Night	16% 4 21% 42% 17%	390
	11th to 20th	Night	13% 3 27% 39% 16% 1	388
	21st to end	Night	13% 4 26% 40% 16% 1	438
August	1st to 10th	Night	13% 2 28% 40% 16% 1	468
	11th to 20th	Night	15% 6% 21% 37% 20% 2	750
	21st to end	Night	16% 6% 21% 35% 20% 3	836
September	1st to 10th	Night	17% 6% 29% 31% 14% 2	760
	11th to 20th	Night	16% 8% 23% 32% 18% 4	760
	21st to end	Night	22% 7% 27% 29% 14% 1	760
October	1st to 10th	Night	24% 11% 26% 26% 12% 2	760
	11th to 20th	Night	18% 14% 31% 27% 9% 1	760
	21st to end	Night	26% 13% 33% 21% 7%	836
November	1st to 10th	Night	16% 14% 36% 25% 8% 1	780
	11th to 20th	Night	24% 17% 32% 21% 6% 1	800
	21st to end	Night	23% 18% 33% 21% 6% 1	800
December	1st to 10th	Night	28% 18% 31% 18% 4 1	800
	11th to 20th	Night	27% 19% 31% 20% 3	800
	21st to end	Night	27% 18% 35% 18% 3	880

Page generated at 2025-08-02 01:32:23. Version ac07

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