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 2025-05-26.

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% 10% 3 8% 5% 5% 4 4 5% 7% 33%	114058
	Night	17% 10% 4 8% 5% 4 4 3 5% 6% 34%	115190
Transparency	Day	50% 5% 12% 21% 11% 2	117636
	Night	51% 5% 12% 20% 12% 1	119775
Seeing	Day	25% 18% 28% 18% 8% 3	15484
	Night	23% 17% 27% 24% 9% 1	24823

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% 14% 10% 18% 6% 4 3 2 3 4 24%	3597
	11th to 20th	Day	13% 14% 7% 16% 7% 5% 4 3 4 5% 21%	3594
	21st to end	Day	18% 15% 6% 8% 6% 4 3 3 4 4 29%	4466
February	1st to 10th	Day	16% 12% 3 11% 7% 6% 6% 4 5% 6% 25%	1800
	11th to 20th	Day	14% 12% 5% 9% 6% 5% 4 4 5% 7% 29%	1847
	21st to end	Day	18% 12% 3 9% 6% 5% 4 3 5% 6% 29%	1650
March	1st to 10th	Day	21% 14% 4 8% 5% 4 3 3 3 4 31%	4522
	11th to 20th	Day	14% 12% 3 7% 5% 4 4 3 4 6% 39%	4980
	21st to end	Day	17% 9% 3 7% 5% 5% 4 4 5% 6% 35%	5757
April	1st to 10th	Day	20% 12% 3 7% 4 5% 4 3 4 5% 33%	2400
	11th to 20th	Day	16% 11% 3 7% 5% 4 4 4 5% 6% 35%	2374
	21st to end	Day	17% 10% 3 6% 5% 5% 4 4 6% 6% 36%	2400
May	1st to 10th	Day	28% 8% 2 5% 4 4 4 3 5% 7% 30%	4359
	11th to 20th	Day	23% 9% 3 7% 6% 5% 4 4 5% 7% 26%	4538
	21st to end	Day	15% 6% 2 5% 4 4 5% 4 7% 9% 40%	4907
June	1st to 10th	Day	16% 6% 3 6% 6% 5% 5% 4 6% 9% 33%	2660
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 4 7% 8% 33%	2660
	21st to end	Day	14% 6% 2 7% 5% 5% 5% 4 7% 9% 35%	2660
July	1st to 10th	Day	8% 6% 3 8% 6% 5% 6% 5% 8% 11% 35%	4440
	11th to 20th	Day	8% 7% 2 8% 5% 5% 5% 4 8% 11% 36%	4440
	21st to end	Day	12% 8% 4 8% 6% 6% 5% 4 6% 7% 33%	4791
August	1st to 10th	Day	21% 9% 3 8% 5% 5% 5% 4 6% 8% 28%	4104
	11th to 20th	Day	16% 7% 2 7% 5% 5% 5% 4 6% 9% 34%	3828
	21st to end	Day	16% 7% 2 6% 4 3 4 3 6% 8% 42%	4180
September	1st to 10th	Day	17% 6% 2 6% 5% 4 4 4 5% 7% 39%	2280
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 7% 46%	2271
	21st to end	Day	19% 7% 3 7% 4 4 4 4 6% 7% 35%	2052
October	1st to 10th	Day	17% 8% 2 6% 4 4 4 4 5% 8% 36%	1900
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 4 5% 7% 37%	1900
	21st to end	Day	22% 10% 3 6% 4 4 5% 3 5% 8% 31%	2014
November	1st to 10th	Day	13% 11% 3 6% 4 4 4 3 4 6% 42%	1761
	11th to 20th	Day	15% 12% 3 8% 4 4 4 3 5% 6% 35%	1780
	21st to end	Day	18% 13% 3 7% 5% 4 4 4 5% 6% 30%	1600
December	1st to 10th	Day	16% 13% 7% 11% 6% 5% 4 3 5% 5% 24%	2600
	11th to 20th	Day	20% 14% 6% 8% 4 4 3 3 4 5% 29%	2986
	21st to end	Day	20% 14% 4 11% 5% 5% 4 3 5% 6% 23%	3960
January	1st to 10th	Night	12% 13% 6% 18% 7% 4 4 3 4 5% 24%	6349
	11th to 20th	Night	11% 14% 6% 17% 6% 5% 4 3 4 5% 23%	6287
	21st to end	Night	17% 11% 4 10% 7% 5% 5% 4 5% 5% 26%	6490
February	1st to 10th	Night	16% 12% 4 9% 6% 5% 4 4 4 7% 30%	2600
	11th to 20th	Night	14% 12% 4 10% 6% 4 5% 5% 5% 6% 27%	2438
	21st to end	Night	17% 12% 3 9% 6% 4 4 3 4 5% 31%	1980
March	1st to 10th	Night	19% 12% 5% 7% 6% 4 3 2 4 5% 33%	5303
	11th to 20th	Night	13% 12% 4 6% 4 5% 4 3 4 5% 39%	4979
	21st to end	Night	17% 11% 3 8% 5% 4 4 3 4 5% 35%	5174
April	1st to 10th	Night	18% 13% 4 8% 6% 4 4 3 4 5% 30%	2000
	11th to 20th	Night	19% 10% 2 6% 5% 4 4 4 5% 7% 37%	1975
	21st to end	Night	19% 8% 3 6% 4 4 4 3 5% 6% 39%	2000
May	1st to 10th	Night	28% 8% 2 6% 4 4 4 3 4 5% 31%	2815
	11th to 20th	Night	22% 10% 2 6% 4 5% 5% 3 5% 7% 31%	2575
	21st to end	Night	14% 8% 3 7% 4 4 4 4 6% 8% 37%	2784
June	1st to 10th	Night	16% 6% 2 5% 4 4 4 4 7% 8% 39%	1520
	11th to 20th	Night	14% 6% 3 7% 4 4 4 4 6% 8% 40%	1520
	21st to end	Night	13% 5% 2 5% 4 4 4 4 6% 9% 44%	1520
July	1st to 10th	Night	12% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	2520
	11th to 20th	Night	12% 5% 3 7% 4 5% 5% 4 7% 10% 38%	2520
	21st to end	Night	16% 7% 2 6% 4 5% 5% 4 5% 6% 40%	2759
August	1st to 10th	Night	21% 8% 3 7% 4 4 4 4 6% 7% 31%	2825
	11th to 20th	Night	18% 6% 3 7% 4 4 4 3 5% 7% 40%	2967
	21st to end	Night	14% 6% 2 6% 4 4 4 3 5% 7% 46%	3476
September	1st to 10th	Night	16% 5% 2 5% 4 4 5% 4 6% 6% 43%	1900
	11th to 20th	Night	13% 6% 2 5% 3 3 4 3 4 6% 50%	1909
	21st to end	Night	19% 7% 2 5% 5% 4 4 3 5% 6% 40%	2123
October	1st to 10th	Night	20% 7% 2 6% 3 4 4 3 5% 7% 40%	2280
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 5% 4 43%	2280
	21st to end	Night	22% 9% 2 6% 3 4 5% 3 6% 7% 34%	2582
November	1st to 10th	Night	12% 10% 3 7% 4 4 4 3 5% 5% 44%	2537
	11th to 20th	Night	18% 11% 3 7% 4 4 3 3 5% 6% 36%	2619
	21st to end	Night	14% 12% 4 6% 5% 4 4 4 6% 7% 34%	2800
December	1st to 10th	Night	15% 13% 7% 10% 6% 5% 4 3 5% 5% 27%	4580
	11th to 20th	Night	23% 13% 4 8% 4 3 3 3 3 4 32%	5208
	21st to end	Night	21% 16% 5% 9% 5% 4 4 3 3 5% 25%	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	65% 3 7% 19% 4 1	3598
	11th to 20th	Day	66% 3 8% 14% 7% 2	3624
	21st to end	Day	58% 3 10% 20% 10%	4466
February	1st to 10th	Day	59% 5% 11% 16% 9% 1	1800
	11th to 20th	Day	55% 5% 8% 22% 10% 1	1856
	21st to end	Day	57% 4 9% 21% 7% 2	1650
March	1st to 10th	Day	57% 3 9% 17% 10% 4	4525
	11th to 20th	Day	46% 4 14% 25% 8% 3	4980
	21st to end	Day	50% 4 10% 13% 20% 3	5757
April	1st to 10th	Day	55% 4 7% 21% 10% 3	2400
	11th to 20th	Day	49% 5% 10% 22% 13% 2	2374
	21st to end	Day	49% 4 9% 22% 13% 3	2400
May	1st to 10th	Day	56% 3 10% 19% 10% 1	4372
	11th to 20th	Day	57% 4 12% 18% 7% 1	4542
	21st to end	Day	40% 5% 12% 26% 15% 1	4907
June	1st to 10th	Day	47% 5% 13% 21% 12% 1	2660
	11th to 20th	Day	47% 5% 13% 22% 10% 1	2660
	21st to end	Day	44% 6% 13% 26% 11%	2660
July	1st to 10th	Day	43% 7% 16% 23% 11%	4370
	11th to 20th	Day	38% 8% 17% 24% 13%	4365
	21st to end	Day	48% 6% 12% 18% 14% 1	4638
August	1st to 10th	Day	54% 6% 14% 19% 7%	4091
	11th to 20th	Day	45% 6% 15% 26% 8%	3867
	21st to end	Day	41% 5% 10% 33% 11% 1	4180
September	1st to 10th	Day	44% 5% 12% 22% 15% 1	2280
	11th to 20th	Day	38% 4 11% 23% 22% 2	2271
	21st to end	Day	47% 5% 10% 22% 15% 2	2052
October	1st to 10th	Day	45% 5% 11% 21% 18% 1	3160
	11th to 20th	Day	41% 4 8% 25% 15% 7%	3140
	21st to end	Day	36% 3 17% 27% 16% 2	3304
November	1st to 10th	Day	43% 4 12% 24% 15% 2	1761
	11th to 20th	Day	51% 4 10% 21% 12% 2	1780
	21st to end	Day	54% 4 14% 21% 7% 1	1600
December	1st to 10th	Day	59% 6% 13% 16% 5% 1	2600
	11th to 20th	Day	58% 3 13% 15% 10%	2986
	21st to end	Day	62% 3 12% 13% 9% 1	3960
January	1st to 10th	Night	63% 4 9% 16% 7% 1	6349
	11th to 20th	Night	63% 4 11% 14% 6% 2	6332
	21st to end	Night	58% 4 10% 14% 13% 1	6490
February	1st to 10th	Night	54% 5% 12% 20% 9% 1	2600
	11th to 20th	Night	57% 5% 10% 17% 9% 1	2440
	21st to end	Night	55% 4 8% 19% 11% 2	1980
March	1st to 10th	Night	55% 2 12% 17% 12% 2	5313
	11th to 20th	Night	46% 5% 17% 21% 7% 4	4980
	21st to end	Night	51% 4 7% 15% 19% 2	5174
April	1st to 10th	Night	57% 3 9% 18% 11% 2	2000
	11th to 20th	Night	49% 5% 10% 21% 15% 1	1975
	21st to end	Night	46% 5% 10% 21% 15% 3	2000
May	1st to 10th	Night	57% 3 8% 22% 8% 2	2821
	11th to 20th	Night	53% 6% 14% 17% 9% 1	2576
	21st to end	Night	44% 5% 14% 21% 13% 1	2785
June	1st to 10th	Night	42% 5% 11% 27% 15%	1520
	11th to 20th	Night	40% 5% 16% 28% 10% 1	1520
	21st to end	Night	37% 6% 15% 28% 13%	1520
July	1st to 10th	Night	42% 7% 16% 19% 15% 1	2480
	11th to 20th	Night	39% 8% 16% 25% 12% 1	2472
	21st to end	Night	43% 6% 14% 21% 16% 1	2671
August	1st to 10th	Night	51% 6% 15% 20% 7%	2814
	11th to 20th	Night	43% 6% 16% 25% 11%	2994
	21st to end	Night	37% 5% 13% 32% 13% 1	3476
September	1st to 10th	Night	40% 6% 12% 24% 16% 1	1900
	11th to 20th	Night	35% 4 10% 27% 22% 2	1909
	21st to end	Night	44% 4 9% 24% 17% 1	2123
October	1st to 10th	Night	48% 4 10% 22% 15% 1	3800
	11th to 20th	Night	38% 4 12% 22% 18% 6%	3779
	21st to end	Night	36% 5% 17% 25% 17% 1	4242
November	1st to 10th	Night	42% 4 12% 23% 17% 3	2537
	11th to 20th	Night	49% 4 10% 21% 12% 2	2619
	21st to end	Night	50% 5% 14% 22% 9% 1	2800
December	1st to 10th	Night	57% 5% 12% 22% 4	4580
	11th to 20th	Night	57% 4 12% 16% 11% 1	5208
	21st to end	Night	63% 3 9% 15% 8% 1	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% 26% 28% 8% 2 1	200
	11th to 20th	Day	42% 27% 24% 6% 1	206
	21st to end	Day	31% 32% 26% 8% 3 1	330
February	1st to 10th	Day	37% 30% 26% 7%	300
	11th to 20th	Day	39% 26% 27% 6% 1	394
	21st to end	Day	34% 28% 27% 8% 3	414
March	1st to 10th	Day	33% 24% 29% 11% 2	500
	11th to 20th	Day	32% 25% 27% 12% 4 1	500
	21st to end	Day	36% 23% 26% 10% 3 2	550
April	1st to 10th	Day	36% 24% 25% 11% 4	500
	11th to 20th	Day	30% 25% 27% 10% 6% 2	492
	21st to end	Day	27% 23% 32% 12% 4 2	500
May	1st to 10th	Day	35% 18% 28% 10% 7% 2	503
	11th to 20th	Day	26% 18% 32% 15% 7% 2	527
	21st to end	Day	20% 13% 31% 23% 11% 3	549
June	1st to 10th	Day	21% 16% 28% 23% 10% 2	490
	11th to 20th	Day	19% 17% 25% 27% 12% 1	490
	21st to end	Day	19% 13% 33% 26% 8% 1	490
July	1st to 10th	Day	15% 8% 29% 28% 16% 5%	485
	11th to 20th	Day	9% 9% 32% 31% 16% 4	484
	21st to end	Day	15% 11% 33% 27% 10% 4	532
August	1st to 10th	Day	14% 9% 27% 26% 18% 6%	486
	11th to 20th	Day	15% 9% 26% 28% 16% 6%	479
	21st to end	Day	13% 11% 28% 25% 14% 8%	539
September	1st to 10th	Day	20% 12% 21% 21% 17% 8%	490
	11th to 20th	Day	14% 8% 25% 23% 18% 11%	490
	21st to end	Day	26% 13% 26% 20% 12% 4	490
October	1st to 10th	Day	26% 14% 24% 19% 13% 5%	490
	11th to 20th	Day	24% 17% 30% 21% 8% 1	490
	21st to end	Day	28% 18% 30% 17% 6% 1	499
November	1st to 10th	Day	24% 22% 23% 22% 8% 1	395
	11th to 20th	Day	30% 22% 28% 16% 4 1	380
	21st to end	Day	39% 23% 29% 8% 2	200
December	1st to 10th	Day	36% 28% 26% 8% 3 1	200
	11th to 20th	Day	40% 25% 25% 9% 2	200
	21st to end	Day	29% 30% 29% 10% 2	220
January	1st to 10th	Night	25% 27% 33% 12% 3	800
	11th to 20th	Night	28% 24% 29% 17% 2	800
	21st to end	Night	21% 29% 33% 15% 2	880
February	1st to 10th	Night	29% 22% 32% 16% 1	800
	11th to 20th	Night	30% 27% 32% 11% 1	783
	21st to end	Night	29% 25% 31% 14% 2	660
March	1st to 10th	Night	29% 23% 30% 16% 3	800
	11th to 20th	Night	28% 22% 29% 17% 4	800
	21st to end	Night	26% 22% 31% 15% 6%	880
April	1st to 10th	Night	26% 22% 31% 19% 2	800
	11th to 20th	Night	25% 21% 29% 18% 6%	791
	21st to end	Night	25% 17% 28% 25% 5%	800
May	1st to 10th	Night	28% 13% 27% 24% 9%	543
	11th to 20th	Night	18% 10% 35% 29% 6% 1	394
	21st to end	Night	14% 9% 26% 37% 14%	423
June	1st to 10th	Night	16% 8% 24% 38% 14%	380
	11th to 20th	Night	14% 8% 28% 40% 10%	380
	21st to end	Night	13% 6% 26% 45% 9% 1	380
July	1st to 10th	Night	13% 5% 22% 39% 21% 1	370
	11th to 20th	Night	12% 5% 19% 43% 18% 2	368
	21st to end	Night	14% 7% 19% 42% 17% 1	424
August	1st to 10th	Night	13% 3 20% 43% 18% 2	567
	11th to 20th	Night	16% 3 15% 36% 28% 2	668
	21st to end	Night	15% 5% 18% 36% 24% 1	836
September	1st to 10th	Night	16% 7% 23% 34% 17% 3	760
	11th to 20th	Night	15% 6% 20% 30% 23% 5%	760
	21st to end	Night	22% 9% 21% 29% 17% 2	760
October	1st to 10th	Night	24% 10% 22% 26% 17% 1	760
	11th to 20th	Night	19% 15% 28% 30% 8%	760
	21st to end	Night	27% 14% 30% 22% 6%	836
November	1st to 10th	Night	18% 18% 32% 24% 7% 1	780
	11th to 20th	Night	25% 21% 29% 19% 6% 1	800
	21st to end	Night	24% 22% 30% 19% 5% 1	800
December	1st to 10th	Night	28% 22% 30% 15% 4	800
	11th to 20th	Night	27% 24% 28% 18% 3	800
	21st to end	Night	27% 22% 32% 16% 3	880

Page generated at 2025-05-23 09:20:59. Version ac07

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