Scranton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Scranton clear sky chart from 2005-11-06 to 2026-09-29.

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% 9% 3 8% 5% 5% 4 4 6% 7% 32%	149597
	Night	17% 10% 4 9% 5% 4 4 3 5% 6% 33%	141787
Transparency	Day	50% 5% 12% 21% 11% 1	153128
	Night	51% 5% 12% 20% 12% 1	146343
Seeing	Day	26% 18% 28% 18% 8% 3	17276
	Night	23% 17% 27% 24% 9% 1	26448

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	14% 15% 9% 17% 6% 4 3 2 4 5% 22%	4661
	11th to 20th	Day	14% 13% 6% 14% 7% 5% 4 3 4 5% 24%	4688
	21st to end	Day	16% 12% 5% 8% 7% 5% 5% 3 4 5% 29%	5780
February	1st to 10th	Day	15% 11% 3 11% 7% 6% 6% 4 5% 6% 25%	1890
	11th to 20th	Day	15% 13% 5% 9% 6% 5% 4 4 5% 6% 29%	1942
	21st to end	Day	17% 13% 4 10% 6% 4 4 3 4 6% 30%	1730
March	1st to 10th	Day	21% 14% 4 8% 5% 4 3 3 3 4 31%	4623
	11th to 20th	Day	14% 12% 3 7% 5% 4 4 3 4 6% 39%	5090
	21st to end	Day	17% 9% 3 7% 5% 5% 4 4 5% 6% 34%	5884
April	1st to 10th	Day	20% 12% 3 7% 4 5% 4 3 4 5% 33%	2520
	11th to 20th	Day	16% 11% 3 7% 5% 4 4 4 5% 7% 35%	2494
	21st to end	Day	18% 10% 3 6% 5% 5% 4 4 6% 6% 35%	2520
May	1st to 10th	Day	25% 8% 2 7% 5% 5% 5% 4 6% 7% 28%	7855
	11th to 20th	Day	19% 9% 3 7% 5% 4 4 4 5% 7% 32%	8221
	21st to end	Day	25% 7% 2 6% 4 4 5% 4 6% 7% 29%	9060
June	1st to 10th	Day	16% 6% 3 6% 5% 5% 5% 4 6% 9% 35%	2940
	11th to 20th	Day	15% 8% 3 7% 5% 5% 5% 4 7% 8% 34%	2940
	21st to end	Day	15% 6% 2 7% 5% 5% 5% 4 7% 9% 35%	2940
July	1st to 10th	Day	11% 7% 3 8% 6% 5% 6% 4 6% 9% 35%	8280
	11th to 20th	Day	9% 6% 3 8% 5% 5% 5% 5% 8% 11% 35%	8280
	21st to end	Day	15% 7% 3 6% 4 5% 4 4 6% 8% 38%	8942
August	1st to 10th	Day	18% 9% 3 8% 5% 6% 5% 5% 7% 8% 25%	6014
	11th to 20th	Day	15% 6% 2 7% 4 5% 5% 4 7% 10% 34%	5631
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 7% 9% 38%	6080
September	1st to 10th	Day	16% 6% 2 6% 5% 4 4 4 5% 8% 40%	2520
	11th to 20th	Day	13% 5% 2 6% 3 4 4 3 5% 7% 46%	2510
	21st to end	Day	20% 7% 3 7% 4 4 4 4 6% 7% 34%	2248
October	1st to 10th	Day	16% 8% 2 6% 4 4 4 4 5% 7% 39%	2000
	11th to 20th	Day	17% 8% 3 6% 5% 4 4 4 5% 7% 36%	2000
	21st to end	Day	21% 10% 3 6% 4 4 5% 3 5% 8% 31%	2120
November	1st to 10th	Day	13% 11% 3 6% 4 4 4 3 5% 6% 41%	1851
	11th to 20th	Day	15% 13% 3 9% 5% 4 4 3 5% 6% 35%	1869
	21st to end	Day	18% 14% 3 7% 5% 4 4 4 5% 6% 30%	1680
December	1st to 10th	Day	16% 13% 7% 11% 6% 5% 4 4 5% 5% 24%	2680
	11th to 20th	Day	20% 14% 6% 8% 4 4 3 3 4 5% 30%	3066
	21st to end	Day	19% 14% 4 12% 5% 4 4 3 5% 6% 23%	4048
January	1st to 10th	Night	13% 14% 6% 18% 7% 4 4 3 4 4 22%	8234
	11th to 20th	Night	12% 14% 6% 17% 6% 5% 4 3 4 5% 23%	8193
	21st to end	Night	14% 9% 4 10% 8% 6% 5% 4 5% 6% 29%	8401
February	1st to 10th	Night	16% 12% 4 9% 6% 5% 4 4 4 7% 30%	2730
	11th to 20th	Night	15% 13% 5% 10% 6% 4 5% 5% 5% 6% 27%	2563
	21st to end	Night	17% 13% 4 10% 6% 4 4 3 4 5% 30%	2076
March	1st to 10th	Night	19% 12% 5% 7% 6% 4 3 2 4 5% 33%	5422
	11th to 20th	Night	13% 12% 4 7% 4 5% 4 3 4 5% 39%	5089
	21st to end	Night	17% 11% 3 8% 5% 4 4 3 4 5% 35%	5289
April	1st to 10th	Night	19% 13% 4 8% 6% 4 4 3 4 5% 30%	2100
	11th to 20th	Night	18% 10% 2 6% 5% 4 4 4 5% 7% 36%	2075
	21st to end	Night	19% 8% 3 6% 4 4 4 3 5% 6% 38%	2100
May	1st to 10th	Night	26% 9% 3 7% 5% 4 4 3 4 6% 28%	5070
	11th to 20th	Night	20% 9% 2 6% 4 4 4 3 5% 7% 35%	4639
	21st to end	Night	24% 10% 3 7% 4 4 3 3 5% 6% 31%	5114
June	1st to 10th	Night	16% 6% 3 5% 4 4 4 4 6% 8% 40%	1680
	11th to 20th	Night	15% 7% 3 7% 4 4 4 4 5% 8% 39%	1680
	21st to end	Night	13% 5% 2 6% 4 4 4 4 7% 9% 42%	1680
July	1st to 10th	Night	14% 7% 3 7% 4 4 5% 4 6% 9% 38%	4680
	11th to 20th	Night	13% 6% 3 7% 5% 5% 5% 4 7% 9% 37%	4680
	21st to end	Night	16% 7% 2 5% 4 4 5% 3 5% 6% 41%	5118
August	1st to 10th	Night	19% 9% 4 8% 5% 4 4 4 6% 7% 29%	4135
	11th to 20th	Night	18% 6% 3 7% 4 4 4 4 5% 7% 38%	4367
	21st to end	Night	13% 7% 2 7% 5% 5% 5% 3 6% 8% 41%	5045
September	1st to 10th	Night	16% 5% 2 5% 4 4 5% 4 6% 6% 43%	2100
	11th to 20th	Night	13% 6% 2 5% 3 3 4 3 4 7% 50%	2110
	21st to end	Night	19% 7% 2 6% 5% 4 4 3 6% 6% 38%	2324
October	1st to 10th	Night	20% 6% 2 6% 3 4 4 3 4 7% 42%	2400
	11th to 20th	Night	17% 7% 2 6% 4 4 4 3 5% 4 43%	2400
	21st to end	Night	21% 10% 2 6% 3 4 4 3 6% 7% 35%	2718
November	1st to 10th	Night	12% 10% 3 7% 4 4 4 3 5% 5% 43%	2667
	11th to 20th	Night	17% 11% 3 7% 4 4 3 3 5% 6% 35%	2750
	21st to end	Night	14% 13% 4 7% 5% 4 4 3 6% 7% 33%	2940
December	1st to 10th	Night	15% 13% 6% 10% 6% 5% 4 4 5% 6% 27%	4720
	11th to 20th	Night	23% 13% 4 8% 4 3 3 3 3 4 32%	5348
	21st to end	Night	21% 16% 5% 9% 5% 4 4 3 3 5% 25%	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	66% 4 9% 16% 5% 1	4662
	11th to 20th	Day	62% 3 9% 15% 9% 2	4718
	21st to end	Day	56% 3 12% 19% 10%	5780
February	1st to 10th	Day	58% 4 11% 17% 9% 1	1890
	11th to 20th	Day	56% 5% 8% 21% 9% 1	1951
	21st to end	Day	57% 4 9% 21% 8% 2	1730
March	1st to 10th	Day	57% 3 9% 17% 10% 4	4626
	11th to 20th	Day	46% 4 14% 25% 8% 3	5090
	21st to end	Day	50% 4 10% 13% 19% 3	5884
April	1st to 10th	Day	55% 4 8% 20% 11% 3	2520
	11th to 20th	Day	48% 5% 11% 22% 13% 2	2494
	21st to end	Day	49% 4 9% 22% 13% 3	2520
May	1st to 10th	Day	55% 5% 13% 18% 9% 1	7865
	11th to 20th	Day	52% 4 11% 22% 10% 1	8225
	21st to end	Day	53% 5% 13% 18% 11% 1	9061
June	1st to 10th	Day	46% 5% 12% 22% 13% 1	2940
	11th to 20th	Day	47% 5% 14% 21% 11% 1	2940
	21st to end	Day	44% 6% 13% 25% 11%	2940
July	1st to 10th	Day	46% 7% 13% 21% 12%	8210
	11th to 20th	Day	39% 8% 15% 26% 11%	8205
	21st to end	Day	43% 6% 11% 23% 16% 1	8744
August	1st to 10th	Day	54% 7% 13% 16% 9% 1	6001
	11th to 20th	Day	43% 6% 18% 26% 6%	5670
	21st to end	Day	40% 6% 11% 30% 11% 1	6080
September	1st to 10th	Day	43% 6% 12% 23% 15% 1	2520
	11th to 20th	Day	38% 4 11% 24% 21% 2	2510
	21st to end	Day	47% 5% 10% 20% 15% 1	2248
October	1st to 10th	Day	44% 4 10% 21% 18% 2	3260
	11th to 20th	Day	42% 4 8% 25% 15% 7%	3240
	21st to end	Day	36% 3 16% 27% 16% 2	3410
November	1st to 10th	Day	43% 4 12% 24% 15% 2	1851
	11th to 20th	Day	51% 4 10% 21% 12% 2	1869
	21st to end	Day	55% 4 14% 20% 6% 1	1680
December	1st to 10th	Day	59% 6% 13% 16% 6% 1	2680
	11th to 20th	Day	58% 3 13% 15% 10%	3066
	21st to end	Day	62% 3 12% 14% 9% 1	4048
January	1st to 10th	Night	66% 4 9% 15% 6% 1	8234
	11th to 20th	Night	62% 4 11% 13% 8% 2	8238
	21st to end	Night	54% 4 10% 17% 14% 1	8401
February	1st to 10th	Night	54% 4 12% 20% 10% 1	2730
	11th to 20th	Night	58% 5% 10% 17% 9% 1	2565
	21st to end	Night	55% 4 9% 20% 11% 2	2076
March	1st to 10th	Night	55% 2 12% 17% 12% 2	5432
	11th to 20th	Night	46% 5% 16% 21% 7% 4	5090
	21st to end	Night	51% 4 8% 15% 19% 2	5289
April	1st to 10th	Night	57% 4 9% 18% 11% 2	2100
	11th to 20th	Night	49% 5% 10% 21% 15% 1	2075
	21st to end	Night	47% 5% 10% 21% 15% 3	2100
May	1st to 10th	Night	57% 4 11% 18% 8% 1	5076
	11th to 20th	Night	49% 6% 14% 21% 10% 1	4640
	21st to end	Night	55% 4 11% 19% 10% 1	5115
June	1st to 10th	Night	41% 5% 10% 27% 16%	1680
	11th to 20th	Night	42% 5% 14% 27% 11% 1	1680
	21st to end	Night	38% 6% 16% 27% 13% 1	1680
July	1st to 10th	Night	42% 8% 16% 20% 14% 1	4640
	11th to 20th	Night	41% 8% 14% 26% 11% 1	4632
	21st to end	Night	41% 6% 12% 25% 16%	5001
August	1st to 10th	Night	52% 7% 14% 19% 8% 1	4124
	11th to 20th	Night	45% 6% 16% 26% 8%	4394
	21st to end	Night	39% 6% 14% 28% 12% 1	5045
September	1st to 10th	Night	40% 6% 12% 25% 16% 1	2100
	11th to 20th	Night	35% 4 11% 27% 22% 2	2110
	21st to end	Night	45% 4 9% 23% 17% 1	2324
October	1st to 10th	Night	47% 4 10% 22% 16% 1	3920
	11th to 20th	Night	38% 4 12% 23% 18% 5%	3899
	21st to end	Night	36% 5% 16% 24% 18% 1	4378
November	1st to 10th	Night	43% 4 12% 23% 17% 2	2667
	11th to 20th	Night	50% 4 10% 21% 12% 2	2750
	21st to end	Night	51% 5% 13% 22% 9%	2940
December	1st to 10th	Night	57% 5% 12% 22% 4	4720
	11th to 20th	Night	57% 4 12% 16% 11% 1	5348
	21st to end	Night	63% 3 9% 15% 8% 1	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	36% 27% 26% 8% 2 1	220
	11th to 20th	Day	44% 26% 23% 5% 1	227
	21st to end	Day	34% 31% 24% 7% 2 1	363
February	1st to 10th	Day	36% 29% 27% 8%	330
	11th to 20th	Day	40% 26% 28% 6% 1	429
	21st to end	Day	33% 30% 26% 7% 2	446
March	1st to 10th	Day	34% 23% 29% 11% 2	540
	11th to 20th	Day	33% 24% 27% 12% 4 1	540
	21st to end	Day	36% 24% 25% 9% 3 2	594
April	1st to 10th	Day	37% 23% 24% 11% 4	540
	11th to 20th	Day	29% 25% 28% 10% 5% 2	532
	21st to end	Day	28% 23% 32% 11% 4 1	540
May	1st to 10th	Day	35% 20% 28% 9% 6% 2	543
	11th to 20th	Day	25% 18% 33% 15% 7% 2	567
	21st to end	Day	22% 14% 30% 21% 10% 2	617
June	1st to 10th	Day	20% 15% 27% 25% 10% 2	570
	11th to 20th	Day	23% 16% 26% 24% 10% 1	570
	21st to end	Day	18% 14% 32% 28% 7% 1	570
July	1st to 10th	Day	15% 8% 30% 29% 15% 4	565
	11th to 20th	Day	9% 10% 32% 30% 16% 4	564
	21st to end	Day	15% 12% 33% 27% 9% 4	620
August	1st to 10th	Day	14% 9% 27% 26% 17% 7%	566
	11th to 20th	Day	15% 9% 26% 28% 17% 5%	559
	21st to end	Day	12% 13% 29% 25% 14% 7%	627
September	1st to 10th	Day	19% 14% 22% 21% 16% 7%	570
	11th to 20th	Day	14% 9% 26% 23% 18% 10%	570
	21st to end	Day	25% 13% 27% 20% 12% 3	562
October	1st to 10th	Day	24% 13% 24% 19% 14% 5%	530
	11th to 20th	Day	25% 17% 29% 20% 8% 1	530
	21st to end	Day	27% 19% 30% 17% 6% 1	539
November	1st to 10th	Day	26% 23% 23% 20% 8% 1	425
	11th to 20th	Day	31% 22% 27% 16% 3	409
	21st to end	Day	40% 24% 27% 7% 1	220
December	1st to 10th	Day	36% 28% 25% 8% 3	220
	11th to 20th	Day	40% 25% 25% 8% 2	220
	21st to end	Day	32% 29% 28% 10% 2	242
January	1st to 10th	Night	25% 27% 33% 12% 3	840
	11th to 20th	Night	29% 24% 29% 16% 2	840
	21st to end	Night	22% 29% 32% 15% 2	924
February	1st to 10th	Night	28% 22% 32% 16% 1	840
	11th to 20th	Night	30% 27% 31% 11% 1	823
	21st to end	Night	28% 25% 30% 14% 2	692
March	1st to 10th	Night	30% 22% 30% 15% 3	840
	11th to 20th	Night	28% 23% 29% 17% 4	840
	21st to end	Night	26% 22% 31% 15% 6%	924
April	1st to 10th	Night	26% 23% 30% 19% 2	840
	11th to 20th	Night	25% 22% 29% 18% 6%	831
	21st to end	Night	26% 17% 28% 24% 5%	840
May	1st to 10th	Night	27% 15% 27% 22% 8%	570
	11th to 20th	Night	18% 10% 36% 29% 6% 1	414
	21st to end	Night	17% 9% 26% 35% 13%	455
June	1st to 10th	Night	15% 8% 24% 39% 13%	420
	11th to 20th	Night	16% 9% 28% 37% 10%	420
	21st to end	Night	13% 6% 26% 44% 11% 1	420
July	1st to 10th	Night	14% 5% 21% 40% 20% 1	410
	11th to 20th	Night	12% 6% 19% 43% 18% 2	408
	21st to end	Night	15% 7% 19% 41% 17% 1	469
August	1st to 10th	Night	13% 4 19% 42% 20% 2	627
	11th to 20th	Night	16% 3 16% 38% 26% 2	740
	21st to end	Night	15% 5% 19% 36% 23% 1	924
September	1st to 10th	Night	17% 7% 22% 34% 17% 2	840
	11th to 20th	Night	15% 6% 20% 31% 23% 5%	840
	21st to end	Night	22% 9% 22% 28% 16% 2	833
October	1st to 10th	Night	24% 9% 22% 26% 18% 1	800
	11th to 20th	Night	20% 15% 28% 29% 8%	800
	21st to end	Night	27% 14% 30% 22% 6%	880
November	1st to 10th	Night	19% 18% 32% 23% 7% 1	820
	11th to 20th	Night	26% 21% 28% 19% 6% 1	840
	21st to end	Night	25% 22% 30% 18% 4 1	840
December	1st to 10th	Night	28% 23% 30% 15% 4	840
	11th to 20th	Night	27% 25% 28% 18% 3	840
	21st to end	Night	29% 22% 31% 16% 2	924

Page generated at 2026-09-26 04:18:45. Version ac07

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