Keene
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keene clear sky chart from 2005-11-06 to 2026-06-01.

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	13% 11% 4 11% 7% 6% 5% 4 6% 7% 27%	132092
	Night	11% 11% 5% 12% 7% 6% 5% 4 5% 6% 26%	131067
Transparency	Day	52% 6% 11% 19% 10% 1	135560
	Night	52% 6% 12% 18% 11% 1	135686
Seeing	Day	25% 23% 30% 15% 6% 2	16612
	Night	21% 22% 29% 20% 7% 1	25689

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	6% 13% 8% 17% 11% 8% 6% 4 4 5% 17%	4661
	11th to 20th	Day	4 14% 8% 19% 13% 10% 5% 3 4 4 17%	4650
	21st to end	Day	7% 10% 5% 15% 9% 10% 7% 5% 5% 5% 21%	5142
February	1st to 10th	Day	9% 12% 6% 14% 10% 7% 7% 4 6% 5% 21%	1890
	11th to 20th	Day	6% 10% 6% 14% 10% 8% 6% 5% 5% 6% 23%	1979
	21st to end	Day	9% 15% 6% 12% 7% 6% 5% 4 6% 6% 24%	1730
March	1st to 10th	Day	12% 13% 6% 15% 8% 5% 4 3 4 5% 24%	4576
	11th to 20th	Day	8% 13% 6% 11% 9% 7% 6% 4 5% 6% 27%	4806
	21st to end	Day	12% 12% 5% 11% 7% 6% 5% 3 4 5% 29%	6096
April	1st to 10th	Day	14% 16% 4 9% 7% 5% 5% 4 5% 6% 27%	2520
	11th to 20th	Day	14% 13% 4 10% 6% 5% 4 3 5% 5% 31%	2494
	21st to end	Day	18% 14% 4 9% 5% 4 4 3 5% 5% 29%	2655
May	1st to 10th	Day	25% 14% 4 10% 6% 5% 4 3 4 5% 20%	6291
	11th to 20th	Day	15% 12% 4 9% 6% 6% 5% 5% 6% 7% 25%	6458
	21st to end	Day	18% 10% 4 8% 6% 6% 5% 4 5% 7% 26%	7103
June	1st to 10th	Day	21% 10% 3 9% 6% 5% 6% 4 6% 6% 27%	2800
	11th to 20th	Day	15% 8% 3 8% 6% 5% 5% 5% 6% 7% 31%	2800
	21st to end	Day	19% 8% 3 9% 5% 6% 5% 5% 7% 6% 27%	2800
July	1st to 10th	Day	12% 7% 2 8% 6% 6% 6% 5% 7% 9% 31%	6360
	11th to 20th	Day	9% 5% 2 7% 6% 6% 7% 6% 8% 10% 34%	6360
	21st to end	Day	12% 6% 2 7% 5% 6% 6% 5% 7% 9% 36%	6926
August	1st to 10th	Day	14% 8% 3 8% 6% 6% 6% 5% 7% 8% 30%	4563
	11th to 20th	Day	12% 7% 3 10% 7% 6% 7% 5% 7% 8% 28%	3989
	21st to end	Day	13% 6% 2 7% 5% 5% 6% 3 7% 9% 35%	4312
September	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 4 6% 8% 41%	2400
	11th to 20th	Day	11% 6% 3 7% 5% 5% 4 3 6% 7% 44%	2314
	21st to end	Day	12% 8% 3 7% 5% 5% 5% 5% 7% 7% 36%	2200
October	1st to 10th	Day	17% 11% 3 7% 6% 4 5% 3 6% 6% 32%	2072
	11th to 20th	Day	14% 13% 4 8% 5% 4 5% 4 5% 6% 32%	1980
	21st to end	Day	18% 13% 5% 10% 6% 4 4 3 4 6% 26%	1980
November	1st to 10th	Day	11% 13% 5% 11% 6% 6% 6% 3 6% 6% 28%	1851
	11th to 20th	Day	11% 12% 6% 11% 8% 6% 5% 4 6% 5% 27%	1860
	21st to end	Day	11% 15% 5% 12% 7% 6% 5% 5% 5% 6% 22%	1680
December	1st to 10th	Day	7% 18% 8% 22% 8% 6% 5% 3 4 4 13%	2680
	11th to 20th	Day	11% 12% 6% 16% 6% 5% 5% 4 6% 6% 22%	3066
	21st to end	Day	12% 13% 6% 12% 6% 5% 5% 3 5% 6% 25%	4048
January	1st to 10th	Night	8% 14% 7% 18% 11% 8% 6% 3 4 5% 16%	8234
	11th to 20th	Night	5% 12% 9% 20% 14% 9% 6% 4 5% 5% 11%	8235
	21st to end	Night	8% 7% 5% 15% 10% 9% 10% 6% 7% 7% 17%	9024
February	1st to 10th	Night	7% 12% 5% 13% 11% 8% 7% 5% 6% 6% 20%	2730
	11th to 20th	Night	6% 10% 5% 14% 10% 9% 7% 4 7% 6% 21%	2526
	21st to end	Night	8% 12% 6% 14% 8% 6% 5% 5% 5% 6% 25%	2076
March	1st to 10th	Night	12% 10% 4 13% 9% 9% 7% 4 5% 5% 21%	5484
	11th to 20th	Night	9% 13% 5% 11% 7% 5% 4 4 6% 7% 29%	5371
	21st to end	Night	13% 12% 6% 13% 6% 5% 4 3 4 4 27%	5077
April	1st to 10th	Night	13% 13% 4 11% 7% 6% 5% 3 5% 7% 27%	2100
	11th to 20th	Night	15% 12% 4 9% 6% 6% 5% 3 6% 6% 27%	2075
	21st to end	Night	16% 10% 5% 8% 7% 5% 4 3 4 5% 33%	1964
May	1st to 10th	Night	23% 19% 3 8% 5% 4 4 4 5% 6% 18%	3914
	11th to 20th	Night	16% 12% 3 8% 5% 5% 5% 4 6% 8% 30%	3655
	21st to end	Night	16% 13% 3 9% 5% 5% 5% 3 6% 6% 28%	4014
June	1st to 10th	Night	20% 9% 3 6% 5% 4 5% 4 6% 7% 32%	1600
	11th to 20th	Night	15% 7% 2 6% 5% 5% 5% 5% 7% 7% 37%	1600
	21st to end	Night	16% 7% 3 7% 5% 6% 4 5% 7% 7% 34%	1600
July	1st to 10th	Night	11% 6% 2 8% 6% 5% 5% 5% 6% 9% 37%	3600
	11th to 20th	Night	12% 6% 3 7% 5% 5% 4 4 6% 7% 42%	3600
	21st to end	Night	9% 7% 2 7% 5% 4 4 4 6% 8% 45%	3926
August	1st to 10th	Night	14% 8% 3 7% 5% 5% 4 3 5% 7% 38%	2586
	11th to 20th	Night	11% 7% 3 10% 6% 5% 5% 5% 7% 6% 37%	3021
	21st to end	Night	9% 8% 2 6% 5% 4 5% 4 6% 8% 43%	3586
September	1st to 10th	Night	12% 6% 2 6% 5% 5% 5% 4 5% 6% 44%	2000
	11th to 20th	Night	11% 7% 2 6% 4 4 4 3 4 6% 47%	2085
	21st to end	Night	15% 8% 2 7% 4 4 4 4 7% 6% 40%	2200
October	1st to 10th	Night	17% 9% 3 7% 4 5% 5% 3 6% 8% 32%	2325
	11th to 20th	Night	15% 11% 3 8% 5% 6% 4 4 5% 7% 33%	2418
	21st to end	Night	17% 14% 5% 10% 7% 6% 5% 3 5% 5% 24%	2860
November	1st to 10th	Night	11% 14% 6% 9% 7% 6% 5% 3 6% 5% 27%	2667
	11th to 20th	Night	11% 12% 5% 13% 6% 5% 5% 4 5% 6% 27%	2756
	21st to end	Night	11% 14% 6% 13% 7% 6% 5% 4 6% 7% 22%	2940
December	1st to 10th	Night	9% 14% 7% 23% 12% 6% 5% 3 4 6% 12%	4720
	11th to 20th	Night	12% 14% 7% 14% 8% 6% 6% 4 5% 4 20%	5348
	21st to end	Night	11% 15% 5% 14% 6% 6% 6% 4 5% 6% 22%	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	60% 5% 12% 18% 5% 1	4662
	11th to 20th	Day	67% 4 8% 8% 10% 3	4680
	21st to end	Day	58% 4 10% 17% 10% 2	5142
February	1st to 10th	Day	60% 4 9% 16% 8% 2	1890
	11th to 20th	Day	55% 6% 11% 17% 11% 1	1988
	21st to end	Day	56% 4 11% 14% 12% 2	1730
March	1st to 10th	Day	59% 6% 8% 12% 10% 6%	4579
	11th to 20th	Day	55% 4 13% 16% 8% 4	4806
	21st to end	Day	55% 5% 6% 12% 19% 4	6096
April	1st to 10th	Day	55% 5% 9% 17% 12% 2	2520
	11th to 20th	Day	52% 6% 7% 18% 14% 1	2494
	21st to end	Day	55% 5% 8% 17% 12% 3	2655
May	1st to 10th	Day	66% 4 7% 16% 7% 1	6302
	11th to 20th	Day	55% 7% 14% 15% 9% 1	6462
	21st to end	Day	54% 6% 11% 21% 8% 1	7103
June	1st to 10th	Day	54% 6% 12% 17% 10% 1	2800
	11th to 20th	Day	47% 6% 12% 22% 11% 2	2800
	21st to end	Day	54% 6% 10% 20% 10% 1	2800
July	1st to 10th	Day	45% 7% 14% 23% 11%	6290
	11th to 20th	Day	39% 9% 14% 27% 10% 1	6285
	21st to end	Day	40% 7% 12% 33% 8%	6728
August	1st to 10th	Day	47% 7% 14% 21% 10% 1	4549
	11th to 20th	Day	47% 8% 15% 23% 5%	4029
	21st to end	Day	41% 8% 14% 25% 11% 1	4312
September	1st to 10th	Day	38% 7% 11% 31% 13% 1	2400
	11th to 20th	Day	37% 6% 10% 30% 17% 1	2314
	21st to end	Day	43% 6% 14% 23% 12% 2	2200
October	1st to 10th	Day	44% 5% 11% 25% 15%	3371
	11th to 20th	Day	44% 4 14% 22% 15% 1	3208
	21st to end	Day	44% 3 14% 30% 8% 1	3180
November	1st to 10th	Day	52% 6% 13% 17% 11% 1	1851
	11th to 20th	Day	53% 6% 10% 14% 14% 3	1860
	21st to end	Day	57% 5% 13% 17% 8% 1	1680
December	1st to 10th	Day	71% 4 8% 12% 4	2680
	11th to 20th	Day	57% 5% 11% 17% 10%	3066
	21st to end	Day	57% 4 9% 13% 15% 1	4048
January	1st to 10th	Night	60% 5% 12% 14% 8% 1	8234
	11th to 20th	Night	66% 6% 9% 10% 8% 2	8280
	21st to end	Night	56% 5% 11% 13% 12% 1	9024
February	1st to 10th	Night	58% 7% 10% 14% 10% 2	2730
	11th to 20th	Night	54% 7% 10% 17% 12% 1	2528
	21st to end	Night	53% 7% 11% 17% 10% 2	2076
March	1st to 10th	Night	58% 6% 9% 12% 13% 2	5494
	11th to 20th	Night	51% 5% 17% 16% 9% 2	5372
	21st to end	Night	55% 5% 5% 16% 15% 3	5077
April	1st to 10th	Night	52% 6% 9% 17% 14% 2	2100
	11th to 20th	Night	53% 5% 11% 18% 12%	2075
	21st to end	Night	50% 6% 10% 19% 13% 3	1964
May	1st to 10th	Night	66% 4 8% 14% 8% 1	3920
	11th to 20th	Night	50% 5% 13% 22% 9% 1	3656
	21st to end	Night	52% 6% 13% 18% 11% 1	4015
June	1st to 10th	Night	47% 7% 13% 20% 12% 1	1600
	11th to 20th	Night	42% 5% 16% 23% 13% 1	1600
	21st to end	Night	44% 6% 17% 24% 9%	1600
July	1st to 10th	Night	40% 6% 18% 26% 11%	3560
	11th to 20th	Night	37% 7% 15% 27% 14%	3552
	21st to end	Night	34% 7% 15% 34% 9%	3809
August	1st to 10th	Night	42% 8% 17% 24% 9%	2576
	11th to 20th	Night	41% 7% 17% 25% 9%	3047
	21st to end	Night	34% 6% 18% 31% 11% 1	3586
September	1st to 10th	Night	35% 7% 15% 30% 13% 1	2000
	11th to 20th	Night	36% 5% 13% 31% 15% 1	2085
	21st to end	Night	40% 7% 12% 25% 14% 2	2200
October	1st to 10th	Night	46% 6% 11% 25% 12% 1	3806
	11th to 20th	Night	42% 5% 13% 24% 12% 5%	3929
	21st to end	Night	47% 6% 14% 23% 9% 1	4610
November	1st to 10th	Night	51% 8% 11% 17% 11% 2	2667
	11th to 20th	Night	52% 7% 10% 17% 11% 3	2756
	21st to end	Night	55% 6% 14% 17% 8% 1	2940
December	1st to 10th	Night	66% 6% 11% 13% 4	4720
	11th to 20th	Night	61% 4 9% 13% 13% 1	5348
	21st to end	Night	61% 4 9% 12% 11% 3	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	17% 31% 30% 15% 5%	220
	11th to 20th	Day	25% 32% 33% 8% 2 1	220
	21st to end	Day	25% 29% 34% 9% 2 1	245
February	1st to 10th	Day	32% 39% 24% 4 1	330
	11th to 20th	Day	31% 30% 30% 7% 1	467
	21st to end	Day	32% 26% 30% 10% 1	446
March	1st to 10th	Day	28% 28% 31% 11% 2	540
	11th to 20th	Day	31% 29% 26% 10% 3 1	540
	21st to end	Day	34% 30% 21% 10% 4 1	594
April	1st to 10th	Day	38% 23% 26% 10% 3 1	540
	11th to 20th	Day	36% 25% 23% 11% 3 2	532
	21st to end	Day	33% 26% 26% 9% 5% 1	540
May	1st to 10th	Day	34% 26% 26% 8% 4 2	543
	11th to 20th	Day	23% 23% 32% 17% 3 1	567
	21st to end	Day	25% 22% 31% 17% 4 2	617
June	1st to 10th	Day	28% 19% 32% 15% 5% 1	530
	11th to 20th	Day	18% 21% 34% 18% 7% 1	530
	21st to end	Day	23% 23% 31% 16% 5% 1	530
July	1st to 10th	Day	18% 13% 37% 22% 9% 2	525
	11th to 20th	Day	12% 15% 41% 22% 8% 1	524
	21st to end	Day	16% 14% 40% 23% 5% 2	576
August	1st to 10th	Day	13% 16% 32% 25% 11% 3	526
	11th to 20th	Day	13% 15% 34% 23% 11% 5%	519
	21st to end	Day	13% 18% 34% 22% 9% 5%	583
September	1st to 10th	Day	17% 15% 32% 19% 11% 6%	530
	11th to 20th	Day	13% 16% 26% 22% 15% 8%	530
	21st to end	Day	15% 21% 32% 18% 9% 5%	530
October	1st to 10th	Day	24% 20% 24% 17% 11% 3	530
	11th to 20th	Day	25% 26% 24% 18% 7% 1	519
	21st to end	Day	30% 22% 31% 15% 2	462
November	1st to 10th	Day	30% 21% 28% 15% 6%	425
	11th to 20th	Day	29% 30% 24% 13% 4 1	400
	21st to end	Day	33% 31% 25% 10% 2	220
December	1st to 10th	Day	25% 32% 26% 13% 4	220
	11th to 20th	Day	33% 34% 25% 8%	220
	21st to end	Day	29% 29% 30% 9% 3	242
January	1st to 10th	Night	21% 30% 33% 14% 3	840
	11th to 20th	Night	25% 24% 34% 13% 3	840
	21st to end	Night	14% 31% 34% 17% 3	924
February	1st to 10th	Night	20% 30% 33% 15% 2	840
	11th to 20th	Night	22% 29% 32% 15% 2	823
	21st to end	Night	21% 29% 31% 16% 3	692
March	1st to 10th	Night	26% 24% 31% 16% 2	840
	11th to 20th	Night	27% 28% 28% 11% 4	840
	21st to end	Night	26% 26% 28% 16% 4 1	924
April	1st to 10th	Night	27% 24% 29% 16% 3	840
	11th to 20th	Night	28% 26% 24% 16% 5% 1	831
	21st to end	Night	26% 22% 28% 19% 5%	704
May	1st to 10th	Night	28% 19% 28% 19% 6%	530
	11th to 20th	Night	21% 20% 30% 22% 6% 1	414
	21st to end	Night	18% 17% 36% 20% 10%	455
June	1st to 10th	Night	22% 13% 33% 23% 10%	400
	11th to 20th	Night	19% 13% 26% 32% 10% 1	400
	21st to end	Night	18% 14% 29% 30% 9% 1	400
July	1st to 10th	Night	12% 11% 29% 33% 14% 1	390
	11th to 20th	Night	11% 7% 30% 34% 15% 2	388
	21st to end	Night	12% 9% 31% 36% 11% 1	438
August	1st to 10th	Night	10% 9% 27% 36% 16% 1	398
	11th to 20th	Night	11% 9% 27% 33% 17% 3	674
	21st to end	Night	14% 10% 28% 29% 18% 1	880
September	1st to 10th	Night	14% 14% 26% 30% 14% 3	800
	11th to 20th	Night	14% 13% 23% 25% 21% 4	800
	21st to end	Night	18% 14% 28% 22% 17% 2	800
October	1st to 10th	Night	22% 17% 25% 22% 14% 1	800
	11th to 20th	Night	23% 20% 25% 22% 8% 1	800
	21st to end	Night	27% 24% 26% 18% 4	880
November	1st to 10th	Night	25% 23% 28% 17% 6% 1	820
	11th to 20th	Night	25% 27% 26% 14% 7% 2	840
	21st to end	Night	24% 28% 26% 16% 5% 1	840
December	1st to 10th	Night	23% 30% 29% 14% 3	840
	11th to 20th	Night	26% 25% 29% 16% 4	840
	21st to end	Night	26% 28% 31% 13% 2	924

Page generated at 2026-05-29 01:53:29. Version ac07

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