Washington Road Scenic Overlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Washington Road Scenic Overlook clear sky chart from 2005-11-06 to 2025-02-06.

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	10% 6% 1 3 2 2 2 2 3 5% 63%	112491
	Night	12% 7% 1 3 2 2 3 2 4 5% 58%	114565
Transparency	Day	27% 3 6% 17% 25% 22%	112240
	Night	30% 3 7% 17% 23% 20%	114406
Seeing	Day	15% 15% 31% 26% 11% 3	15334
	Night	15% 7% 19% 32% 22% 4	24757

By Month

Percentage Cloud Cover SW (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	17% 13% 2 4 3 3 3 2 4 7% 43%	3639
	11th to 20th	Day	15% 8% 2 5% 3 3 2 2 2 4 54%	3886
	21st to end	Day	19% 8% 2 4 3 2 2 2 3 4 49%	4510
February	1st to 10th	Day	21% 10% 1 4 2 2 2 2 5% 5% 44%	1756
	11th to 20th	Day	16% 13% 2 4 3 3 3 3 5% 5% 44%	1794
	21st to end	Day	18% 16% 2 4 2 2 2 3 4 4 43%	1570
March	1st to 10th	Day	20% 24% 5% 7% 3 3 3 2 4 5% 26%	3190
	11th to 20th	Day	14% 11% 2 4 2 2 2 2 3 4 56%	3490
	21st to end	Day	18% 19% 3 7% 4 4 3 3 5% 5% 29%	4001
April	1st to 10th	Day	17% 11% 2 5% 3 3 3 3 5% 7% 42%	2280
	11th to 20th	Day	14% 8% 2 4 4 3 3 3 4 5% 50%	2249
	21st to end	Day	12% 6% 1 3 3 3 3 2 5% 6% 55%	2280
May	1st to 10th	Day	9% 5% 2 3 2 2 2 2 3 4 68%	3946
	11th to 20th	Day	5% 3 1 2 2 2 2 2 3 4 75%	4377
	21st to end	Day	7% 3 1 3 2 2 2 2 3 5% 69%	4813
June	1st to 10th	Day	8% 4 1 4 3 3 4 3 5% 7% 59%	2660
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 5% 76%	2660
	21st to end	Day	3 1 2 1 1 1 1 3 3 82%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 1 92%	4420
	11th to 20th	Day	1 1 1 1 1 1 2 2 2 3 84%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4562
August	1st to 10th	Day	2 2 1 2 2 2 2 2 3 4 77%	4091
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 89%	3766
	21st to end	Day	2 1 1 1 1 1 1 2 2 88%	4180
September	1st to 10th	Day	2 1 1 1 1 2 1 2 3 86%	2280
	11th to 20th	Day	5% 2 1 2 1 2 3 2 4 4 74%	2280
	21st to end	Day	5% 2 1 2 2 2 1 2 3 5% 76%	2060
October	1st to 10th	Day	4 2 1 2 1 2 2 3 4 5% 72%	3180
	11th to 20th	Day	8% 2 1 3 2 2 2 2 4 6% 68%	3161
	21st to end	Day	6% 4 1 4 4 4 4 3 4 6% 59%	3448
November	1st to 10th	Day	14% 8% 2 3 4 3 3 3 4 6% 52%	1767
	11th to 20th	Day	16% 5% 1 3 4 3 4 3 4 7% 49%	1800
	21st to end	Day	13% 8% 2 4 3 3 4 3 4 5% 51%	1663
December	1st to 10th	Day	11% 4 1 3 2 3 3 4 5% 6% 57%	2620
	11th to 20th	Day	28% 10% 2 5% 3 3 3 3 5% 6% 32%	3028
	21st to end	Day	25% 8% 2 6% 3 4 4 3 6% 7% 32%	4004
January	1st to 10th	Night	12% 12% 2 5% 3 4 4 4 5% 7% 42%	6306
	11th to 20th	Night	16% 7% 2 3 3 3 3 3 4 5% 53%	6083
	21st to end	Night	16% 10% 2 5% 3 4 4 3 4 5% 45%	6468
February	1st to 10th	Night	21% 7% 2 4 3 3 3 2 4 5% 47%	2535
	11th to 20th	Night	15% 11% 1 4 3 4 4 3 5% 6% 44%	2274
	21st to end	Night	17% 11% 3 4 2 2 3 3 4 5% 45%	1884
March	1st to 10th	Night	22% 23% 4 4 3 2 2 2 3 5% 30%	3679
	11th to 20th	Night	17% 8% 1 3 2 2 2 2 3 5% 55%	3490
	21st to end	Night	20% 18% 2 5% 3 3 4 3 5% 5% 31%	3650
April	1st to 10th	Night	16% 11% 2 5% 3 3 2 3 6% 5% 46%	1900
	11th to 20th	Night	14% 7% 2 4 3 3 3 3 4 6% 51%	1879
	21st to end	Night	11% 5% 1 3 3 2 3 2 4 6% 60%	1900
May	1st to 10th	Night	6% 7% 1 3 2 3 3 3 4 5% 63%	3022
	11th to 20th	Night	5% 2 1 2 2 2 2 3 3 5% 72%	2516
	21st to end	Night	6% 3 1 3 1 2 2 2 3 5% 72%	2762
June	1st to 10th	Night	8% 4 1 2 2 3 3 3 4 7% 64%	1520
	11th to 20th	Night	3 2 1 2 2 2 2 2 3 5% 77%	1520
	21st to end	Night	3 2 1 2 2 1 2 1 3 3 81%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 92%	2540
	11th to 20th	Night	2 2 1 3 1 2 2 1 2 3 82%	2540
	21st to end	Night	1 1 1 2 1 1 1 2 3 3 85%	2981
August	1st to 10th	Night	4 3 1 3 1 2 3 3 5% 5% 72%	2848
	11th to 20th	Night	1 1 1 1 1 1 2 3 89%	3083
	21st to end	Night	2 1 1 1 1 1 1 1 2 87%	3498
September	1st to 10th	Night	2 1 1 1 1 1 1 2 4 85%	1900
	11th to 20th	Night	4 2 1 3 2 1 2 2 3 4 76%	1900
	21st to end	Night	4 2 1 2 2 2 2 2 4 4 76%	2116
October	1st to 10th	Night	4 2 1 3 2 2 2 2 2 3 77%	3800
	11th to 20th	Night	4 2 1 2 2 1 2 2 3 4 76%	3777
	21st to end	Night	11% 3 1 3 2 2 3 3 4 6% 62%	4121
November	1st to 10th	Night	16% 7% 1 3 2 2 3 3 3 6% 53%	2530
	11th to 20th	Night	12% 5% 1 4 3 3 3 3 6% 8% 53%	2600
	21st to end	Night	13% 7% 2 4 3 3 3 3 3 6% 53%	2735
December	1st to 10th	Night	12% 4 1 2 1 2 3 3 4 5% 62%	4560
	11th to 20th	Night	25% 12% 2 5% 3 3 4 3 6% 8% 29%	5176
	21st to end	Night	27% 11% 3 6% 4 3 4 3 4 5% 31%	6952

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	43% 4 11% 18% 15% 9%	3639
	11th to 20th	Day	37% 2 6% 15% 23% 16%	3886
	21st to end	Day	41% 3 6% 14% 20% 18%	4510
February	1st to 10th	Day	43% 3 9% 17% 19% 10%	1756
	11th to 20th	Day	43% 4 8% 18% 20% 7%	1804
	21st to end	Day	45% 2 9% 22% 15% 7%	1570
March	1st to 10th	Day	62% 5% 6% 11% 11% 5%	3190
	11th to 20th	Day	35% 3 7% 31% 19% 5%	3490
	21st to end	Day	57% 6% 10% 17% 8% 2	4001
April	1st to 10th	Day	44% 4 12% 21% 16% 2	2280
	11th to 20th	Day	37% 5% 12% 23% 17% 6%	2252
	21st to end	Day	30% 5% 13% 28% 21% 4	2280
May	1st to 10th	Day	23% 3 13% 26% 22% 13%	3946
	11th to 20th	Day	16% 3 8% 26% 39% 9%	4380
	21st to end	Day	19% 4 9% 41% 23% 3	4814
June	1st to 10th	Day	25% 5% 10% 22% 28% 9%	2660
	11th to 20th	Day	13% 3 8% 21% 36% 19%	2660
	21st to end	Day	10% 1 3 16% 37% 32%	2660
July	1st to 10th	Day	4 1 1 6% 16% 72%	4351
	11th to 20th	Day	9% 1 2 7% 18% 62%	4345
	21st to end	Day	7% 1 2 5% 29% 56%	4418
August	1st to 10th	Day	13% 1 1 8% 24% 53%	4076
	11th to 20th	Day	5% 1 2 6% 43% 43%	3802
	21st to end	Day	7% 1 1 11% 44% 35%	4179
September	1st to 10th	Day	7% 1 2 9% 34% 47%	2280
	11th to 20th	Day	15% 3 4 21% 38% 20%	2280
	21st to end	Day	15% 2 5% 19% 35% 25%	2060
October	1st to 10th	Day	17% 2 3 11% 33% 33%	3180
	11th to 20th	Day	20% 2 4 17% 40% 17%	3161
	21st to end	Day	27% 1 5% 23% 29% 15%	3448
November	1st to 10th	Day	35% 3 7% 19% 22% 14%	1767
	11th to 20th	Day	35% 3 10% 18% 22% 11%	1800
	21st to end	Day	35% 4 7% 18% 22% 14%	1663
December	1st to 10th	Day	29% 2 7% 20% 26% 16%	2620
	11th to 20th	Day	54% 2 7% 15% 14% 7%	3028
	21st to end	Day	51% 3 11% 18% 13% 4	4004
January	1st to 10th	Night	41% 4 12% 20% 16% 7%	6306
	11th to 20th	Night	36% 3 7% 11% 26% 17%	6083
	21st to end	Night	43% 3 5% 11% 16% 23%	6468
February	1st to 10th	Night	42% 3 7% 18% 19% 12%	2535
	11th to 20th	Night	42% 4 7% 19% 20% 9%	2275
	21st to end	Night	43% 3 7% 22% 19% 6%	1884
March	1st to 10th	Night	59% 4 9% 13% 10% 6%	3679
	11th to 20th	Night	34% 3 6% 23% 27% 6%	3490
	21st to end	Night	54% 6% 10% 18% 8% 2	3650
April	1st to 10th	Night	41% 4 12% 22% 17% 4	1900
	11th to 20th	Night	35% 5% 13% 23% 18% 6%	1879
	21st to end	Night	27% 4 13% 32% 20% 3	1900
May	1st to 10th	Night	23% 7% 11% 23% 26% 9%	3022
	11th to 20th	Night	15% 4 9% 20% 34% 18%	2516
	21st to end	Night	16% 5% 11% 38% 24% 6%	2762
June	1st to 10th	Night	22% 8% 10% 24% 25% 11%	1520
	11th to 20th	Night	11% 3 8% 23% 34% 21%	1520
	21st to end	Night	12% 1 4 14% 33% 36%	1520
July	1st to 10th	Night	4 2 1 5% 15% 73%	2500
	11th to 20th	Night	13% 1 2 7% 15% 63%	2492
	21st to end	Night	7% 1 2 5% 25% 60%	2888
August	1st to 10th	Night	15% 1 2 7% 23% 51%	2839
	11th to 20th	Night	5% 1 2 8% 39% 45%	3113
	21st to end	Night	8% 1 2 12% 36% 41%	3498
September	1st to 10th	Night	7% 1 3 8% 31% 51%	1900
	11th to 20th	Night	14% 2 5% 19% 39% 21%	1900
	21st to end	Night	13% 3 4 20% 33% 27%	2116
October	1st to 10th	Night	16% 2 3 10% 28% 41%	3800
	11th to 20th	Night	15% 1 4 23% 38% 18%	3777
	21st to end	Night	25% 2 4 22% 29% 18%	4121
November	1st to 10th	Night	34% 4 6% 20% 20% 16%	2530
	11th to 20th	Night	30% 5% 11% 20% 23% 11%	2600
	21st to end	Night	34% 3 6% 19% 22% 16%	2735
December	1st to 10th	Night	26% 3 6% 19% 23% 23%	4560
	11th to 20th	Night	54% 2 5% 12% 21% 6%	5176
	21st to end	Night	57% 3 7% 16% 11% 6%	6952

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	40% 14% 20% 18% 8% 1	200
	11th to 20th	Day	25% 15% 23% 26% 10% 1	303
	21st to end	Day	26% 14% 24% 22% 12% 2	440
February	1st to 10th	Day	32% 15% 24% 22% 7% 1	386
	11th to 20th	Day	29% 18% 29% 18% 5%	428
	21st to end	Day	27% 18% 33% 16% 6%	382
March	1st to 10th	Day	37% 23% 23% 11% 4 1	460
	11th to 20th	Day	32% 19% 23% 16% 8% 2	460
	21st to end	Day	29% 26% 26% 15% 4	506
April	1st to 10th	Day	24% 25% 29% 15% 6% 1	460
	11th to 20th	Day	25% 22% 27% 20% 6% 1	452
	21st to end	Day	13% 22% 30% 24% 9% 2	460
May	1st to 10th	Day	17% 25% 30% 20% 6% 2	463
	11th to 20th	Day	16% 19% 31% 22% 8% 4	488
	21st to end	Day	12% 14% 32% 27% 11% 4	529
June	1st to 10th	Day	9% 15% 32% 28% 11% 4	490
	11th to 20th	Day	8% 17% 38% 23% 9% 4	490
	21st to end	Day	2 12% 38% 31% 11% 6%	490
July	1st to 10th	Day	1 6% 42% 34% 12% 5%	486
	11th to 20th	Day	1 5% 39% 34% 14% 6%	484
	21st to end	Day	1 6% 36% 37% 15% 5%	531
August	1st to 10th	Day	4 5% 39% 34% 13% 5%	487
	11th to 20th	Day	2 9% 34% 37% 13% 4	477
	21st to end	Day	2 6% 36% 40% 13% 3	539
September	1st to 10th	Day	2 9% 42% 31% 14% 2	490
	11th to 20th	Day	8% 13% 33% 32% 11% 3	490
	21st to end	Day	6% 13% 33% 35% 10% 2	490
October	1st to 10th	Day	6% 18% 31% 31% 12% 2	490
	11th to 20th	Day	9% 13% 28% 33% 14% 3	490
	21st to end	Day	13% 14% 28% 29% 12% 3	539
November	1st to 10th	Day	18% 13% 20% 26% 19% 3	303
	11th to 20th	Day	16% 12% 25% 28% 15% 4	300
	21st to end	Day	20% 11% 23% 26% 16% 3	231
December	1st to 10th	Day	24% 12% 21% 23% 14% 8%	200
	11th to 20th	Day	26% 12% 22% 22% 15% 4	200
	21st to end	Day	29% 11% 27% 21% 11% 2	220
January	1st to 10th	Night	26% 9% 23% 25% 13% 4	800
	11th to 20th	Night	20% 10% 29% 29% 10% 1	800
	21st to end	Night	24% 10% 24% 24% 17% 2	880
February	1st to 10th	Night	25% 10% 23% 28% 12% 1	780
	11th to 20th	Night	22% 9% 22% 28% 15% 3	744
	21st to end	Night	24% 12% 22% 30% 9% 2	628
March	1st to 10th	Night	30% 11% 21% 23% 13% 2	760
	11th to 20th	Night	25% 10% 17% 26% 21% 2	760
	21st to end	Night	26% 10% 24% 26% 13% 1	836
April	1st to 10th	Night	21% 8% 21% 33% 16% 2	760
	11th to 20th	Night	16% 11% 23% 30% 16% 4	751
	21st to end	Night	13% 7% 20% 35% 21% 4	760
May	1st to 10th	Night	11% 11% 24% 30% 21% 3	667
	11th to 20th	Night	11% 4 17% 39% 25% 4	374
	21st to end	Night	12% 3 16% 33% 31% 5%	411
June	1st to 10th	Night	9% 3 14% 37% 32% 4	380
	11th to 20th	Night	3 5% 17% 40% 31% 4	380
	21st to end	Night	3 1 14% 42% 35% 4	380
July	1st to 10th	Night	1 11% 35% 49% 3	370
	11th to 20th	Night	1 1 11% 44% 39% 5%	368
	21st to end	Night	1 1 9% 33% 48% 8%	548
August	1st to 10th	Night	4 1 11% 38% 40% 7%	567
	11th to 20th	Night	1 2 12% 42% 36% 8%	721
	21st to end	Night	1 1 10% 43% 40% 5%	836
September	1st to 10th	Night	2 2 12% 43% 38% 5%	760
	11th to 20th	Night	4 2 14% 38% 32% 9%	760
	21st to end	Night	4 4 20% 36% 26% 9%	760
October	1st to 10th	Night	7% 6% 17% 41% 25% 4	760
	11th to 20th	Night	9% 6% 18% 35% 27% 5%	760
	21st to end	Night	11% 8% 21% 30% 24% 7%	836
November	1st to 10th	Night	18% 6% 18% 30% 23% 5%	780
	11th to 20th	Night	14% 7% 27% 32% 18% 3	800
	21st to end	Night	17% 8% 26% 29% 17% 4	800
December	1st to 10th	Night	24% 8% 22% 31% 13% 3	800
	11th to 20th	Night	30% 8% 21% 28% 12% 2	800
	21st to end	Night	30% 11% 23% 25% 10%	880

Page generated at 2025-02-03 00:05:49. Version ac07

Copyright © 2025 Attilla Danko.