County Road 2C
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the County Road 2C clear sky chart from 2005-11-06 to 2026-09-14.

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	5% 4 1 4 3 3 4 3 6% 8% 59%	157453
	Night	5% 5% 2 5% 4 4 4 4 5% 7% 55%	151173
Transparency	Day	22% 5% 11% 25% 26% 11%	152453
	Night	28% 5% 11% 24% 24% 9%	147185
Seeing	Day	7% 7% 26% 32% 22% 7%	18153
	Night	7% 6% 30% 40% 15% 1	28024

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	2 7% 3 7% 4 4 4 3 5% 5% 57%	4720
	11th to 20th	Day	1 4 2 5% 4 3 4 4 5% 6% 63%	4740
	21st to end	Day	2 8% 2 5% 3 2 2 2 4 6% 62%	5766
February	1st to 10th	Day	2 8% 2 5% 4 3 3 4 5% 7% 57%	2017
	11th to 20th	Day	2 6% 2 6% 5% 4 3 3 5% 7% 57%	2049
	21st to end	Day	3 6% 2 7% 3 3 4 3 3 5% 62%	1730
March	1st to 10th	Day	2 3 2 4 3 3 4 3 4 6% 66%	4600
	11th to 20th	Day	5% 5% 2 4 3 3 3 3 5% 7% 59%	4801
	21st to end	Day	3 4 2 5% 4 4 4 3 7% 9% 56%	6101
April	1st to 10th	Day	5% 5% 1 4 3 3 4 3 5% 7% 57%	2520
	11th to 20th	Day	8% 5% 2 5% 4 4 4 3 5% 7% 53%	2491
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 8% 50%	2525
May	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 6% 53%	7655
	11th to 20th	Day	6% 4 1 4 3 3 4 3 5% 7% 60%	7642
	21st to end	Day	11% 5% 2 4 3 3 3 3 5% 9% 52%	9026
June	1st to 10th	Day	6% 3 1 3 3 3 3 4 7% 11% 56%	2940
	11th to 20th	Day	5% 3 1 3 3 3 4 4 5% 8% 61%	2940
	21st to end	Day	3 3 1 5% 3 4 4 4 7% 9% 56%	2940
July	1st to 10th	Day	2 2 1 3 3 4 5% 4 7% 9% 60%	8249
	11th to 20th	Day	2 2 1 3 3 3 4 4 6% 8% 65%	8250
	21st to end	Day	2 3 1 4 3 4 5% 5% 7% 11% 55%	8957
August	1st to 10th	Day	7% 4 1 3 3 3 4 4 7% 10% 54%	7273
	11th to 20th	Day	3 2 1 3 3 4 4 5% 8% 11% 56%	7003
	21st to end	Day	5% 3 1 5% 3 4 5% 4 8% 11% 50%	7751
September	1st to 10th	Day	4 4 1 4 3 3 4 3 5% 7% 62%	2520
	11th to 20th	Day	6% 3 1 3 2 2 3 3 4 7% 65%	2332
	21st to end	Day	5% 3 1 3 2 3 3 3 4 5% 68%	2200
October	1st to 10th	Day	5% 3 1 2 1 1 1 2 3 4 78%	3526
	11th to 20th	Day	5% 4 2 5% 2 2 2 2 4 6% 66%	3250
	21st to end	Day	4 4 1 3 2 2 2 2 3 5% 71%	3293
November	1st to 10th	Day	4 3 1 3 2 2 3 3 6% 6% 66%	1853
	11th to 20th	Day	2 4 2 4 3 2 3 2 3 6% 69%	1890
	21st to end	Day	4 5% 2 3 2 3 3 3 4 6% 65%	1890
December	1st to 10th	Day	2 7% 1 4 2 1 2 3 3 5% 69%	2815
	11th to 20th	Day	2 4 2 4 3 2 3 2 6% 7% 67%	3106
	21st to end	Day	3 6% 2 6% 3 3 3 3 5% 7% 59%	4092
January	1st to 10th	Night	3 8% 3 6% 4 3 4 4 5% 6% 54%	8201
	11th to 20th	Night	1 6% 2 6% 3 3 4 3 4 6% 62%	8250
	21st to end	Night	2 7% 3 8% 3 3 3 2 4 5% 60%	8492
February	1st to 10th	Night	4 6% 2 5% 4 3 4 3 4 7% 57%	2600
	11th to 20th	Night	3 8% 3 7% 4 4 4 4 5% 7% 50%	2458
	21st to end	Night	4 5% 2 5% 3 2 2 3 4 6% 63%	2076
March	1st to 10th	Night	3 5% 2 6% 3 3 4 3 4 5% 62%	5494
	11th to 20th	Night	6% 7% 2 5% 3 3 3 3 5% 6% 56%	5400
	21st to end	Night	7% 6% 2 6% 4 4 4 3 6% 8% 50%	5094
April	1st to 10th	Night	6% 6% 2 5% 3 5% 4 3 6% 7% 53%	2100
	11th to 20th	Night	8% 5% 2 5% 3 4 5% 4 6% 8% 50%	2077
	21st to end	Night	11% 7% 3 5% 5% 4 4 2 5% 8% 46%	2093
May	1st to 10th	Night	14% 7% 2 5% 3 3 4 3 5% 7% 48%	5292
	11th to 20th	Night	9% 6% 2 5% 3 4 4 4 6% 8% 50%	5234
	21st to end	Night	16% 8% 2 6% 4 4 4 3 5% 7% 42%	5181
June	1st to 10th	Night	5% 3 2 4 4 4 5% 4 7% 10% 51%	1680
	11th to 20th	Night	3 4 1 3 4 4 4 4 6% 10% 55%	1680
	21st to end	Night	5% 4 2 6% 5% 4 4 6% 6% 10% 48%	1680
July	1st to 10th	Night	4 4 2 5% 4 5% 5% 5% 8% 10% 48%	4740
	11th to 20th	Night	4 3 1 4 4 4 5% 4 6% 9% 56%	4740
	21st to end	Night	4 4 3 8% 6% 6% 7% 6% 8% 9% 39%	5152
August	1st to 10th	Night	9% 5% 2 6% 5% 5% 5% 5% 7% 8% 43%	5516
	11th to 20th	Night	7% 5% 2 7% 5% 6% 6% 5% 7% 9% 40%	5853
	21st to end	Night	9% 5% 2 6% 5% 6% 6% 5% 8% 10% 37%	6465
September	1st to 10th	Night	7% 4 1 4 3 3 4 4 6% 7% 56%	2100
	11th to 20th	Night	6% 3 1 3 2 3 3 4 7% 8% 60%	2135
	21st to end	Night	5% 3 1 4 3 3 3 2 4 6% 65%	2200
October	1st to 10th	Night	6% 3 1 3 2 3 3 3 4 5% 68%	3652
	11th to 20th	Night	6% 3 2 4 3 3 4 3 5% 7% 61%	3898
	21st to end	Night	4 4 1 4 2 3 3 3 4 5% 68%	4474
November	1st to 10th	Night	4 3 1 3 2 2 3 3 3 7% 68%	2665
	11th to 20th	Night	2 4 1 4 2 2 2 2 4 5% 71%	2730
	21st to end	Night	4 5% 2 5% 3 3 3 3 4 7% 63%	2730
December	1st to 10th	Night	1 3 1 4 3 3 3 3 4 6% 70%	4592
	11th to 20th	Night	2 5% 2 4 4 3 3 3 5% 7% 63%	5321
	21st to end	Night	3 5% 2 5% 4 4 4 4 6% 7% 54%	7128

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	29% 3 7% 32% 21% 8%	4723
	11th to 20th	Day	21% 4 9% 25% 29% 12%	4740
	21st to end	Day	25% 2 8% 24% 30% 10%	5766
February	1st to 10th	Day	27% 4 9% 26% 24% 10%	2017
	11th to 20th	Day	28% 4 8% 27% 25% 9%	2059
	21st to end	Day	27% 3 7% 18% 27% 18%	1730
March	1st to 10th	Day	18% 4 6% 19% 34% 18%	4600
	11th to 20th	Day	25% 3 6% 23% 33% 10%	4801
	21st to end	Day	23% 5% 11% 38% 19% 4	6101
April	1st to 10th	Day	25% 5% 10% 24% 25% 10%	2520
	11th to 20th	Day	29% 5% 10% 24% 20% 12%	2494
	21st to end	Day	30% 5% 12% 24% 23% 7%	2525
May	1st to 10th	Day	33% 4 9% 25% 22% 8%	7655
	11th to 20th	Day	23% 4 10% 25% 27% 10%	7646
	21st to end	Day	29% 6% 14% 25% 17% 10%	9027
June	1st to 10th	Day	20% 7% 16% 29% 19% 8%	2940
	11th to 20th	Day	20% 6% 11% 22% 24% 17%	2940
	21st to end	Day	21% 6% 11% 22% 25% 15%	2940
July	1st to 10th	Day	17% 6% 9% 21% 33% 14%	8181
	11th to 20th	Day	15% 5% 14% 22% 27% 17%	8175
	21st to end	Day	21% 7% 18% 24% 18% 12%	8759
August	1st to 10th	Day	24% 6% 14% 28% 21% 7%	5752
	11th to 20th	Day	21% 7% 20% 25% 21% 5%	5519
	21st to end	Day	20% 5% 21% 29% 17% 8%	6078
September	1st to 10th	Day	21% 5% 8% 24% 27% 15%	2520
	11th to 20th	Day	20% 4 9% 20% 30% 18%	2332
	21st to end	Day	19% 3 6% 20% 35% 16%	2200
October	1st to 10th	Day	14% 2 5% 16% 37% 26%	3526
	11th to 20th	Day	21% 3 7% 25% 33% 10%	3250
	21st to end	Day	18% 2 5% 23% 37% 15%	3293
November	1st to 10th	Day	18% 3 9% 27% 28% 16%	1853
	11th to 20th	Day	19% 3 6% 28% 33% 12%	1890
	21st to end	Day	22% 3 9% 22% 30% 15%	1890
December	1st to 10th	Day	19% 2 7% 29% 34% 9%	2815
	11th to 20th	Day	18% 2 8% 29% 35% 8%	3104
	21st to end	Day	26% 4 8% 27% 26% 8%	4092
January	1st to 10th	Night	31% 3 6% 31% 24% 6%	8202
	11th to 20th	Night	23% 4 10% 23% 28% 13%	8250
	21st to end	Night	27% 4 7% 23% 29% 10%	8492
February	1st to 10th	Night	28% 5% 9% 25% 24% 9%	2600
	11th to 20th	Night	32% 4 11% 25% 22% 6%	2458
	21st to end	Night	23% 3 6% 22% 31% 15%	2076
March	1st to 10th	Night	23% 3 7% 16% 34% 17%	5494
	11th to 20th	Night	28% 4 11% 16% 26% 14%	5400
	21st to end	Night	30% 6% 13% 31% 17% 3	5094
April	1st to 10th	Night	29% 5% 10% 23% 22% 10%	2100
	11th to 20th	Night	30% 6% 11% 22% 21% 9%	2077
	21st to end	Night	36% 5% 11% 24% 18% 5%	2093
May	1st to 10th	Night	35% 7% 14% 26% 14% 5%	5293
	11th to 20th	Night	30% 6% 12% 27% 18% 7%	5235
	21st to end	Night	41% 7% 15% 19% 13% 5%	5182
June	1st to 10th	Night	24% 10% 22% 24% 14% 6%	1680
	11th to 20th	Night	22% 8% 14% 23% 20% 13%	1680
	21st to end	Night	29% 7% 11% 23% 19% 12%	1680
July	1st to 10th	Night	28% 7% 12% 27% 21% 5%	4700
	11th to 20th	Night	25% 5% 16% 18% 26% 11%	4692
	21st to end	Night	38% 8% 13% 17% 17% 6%	5038
August	1st to 10th	Night	37% 7% 14% 22% 14% 6%	4361
	11th to 20th	Night	41% 10% 14% 20% 11% 3	4613
	21st to end	Night	33% 8% 21% 22% 12% 4	5069
September	1st to 10th	Night	26% 6% 12% 20% 24% 12%	2100
	11th to 20th	Night	20% 6% 11% 23% 24% 16%	2135
	21st to end	Night	22% 4 8% 20% 33% 13%	2200
October	1st to 10th	Night	18% 5% 6% 19% 31% 21%	3652
	11th to 20th	Night	22% 4 7% 26% 27% 12%	3898
	21st to end	Night	21% 3 6% 26% 30% 15%	4474
November	1st to 10th	Night	18% 3 10% 26% 28% 15%	2665
	11th to 20th	Night	18% 3 6% 26% 34% 13%	2730
	21st to end	Night	23% 3 9% 22% 28% 14%	2730
December	1st to 10th	Night	17% 3 7% 34% 30% 9%	4592
	11th to 20th	Night	22% 2 6% 29% 33% 7%	5322
	21st to end	Night	27% 5% 9% 24% 27% 8%	7128

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	6% 6% 29% 39% 15% 4	330
	11th to 20th	Day	11% 9% 28% 35% 17% 1	330
	21st to end	Day	6% 9% 31% 37% 14% 4	363
February	1st to 10th	Day	5% 9% 39% 33% 10% 3	330
	11th to 20th	Day	5% 5% 49% 28% 11% 1	330
	21st to end	Day	4 12% 37% 34% 9% 3	273
March	1st to 10th	Day	5% 8% 31% 31% 22% 3	330
	11th to 20th	Day	9% 9% 34% 29% 17% 2	379
	21st to end	Day	11% 14% 35% 27% 11% 2	594
April	1st to 10th	Day	9% 15% 36% 24% 12% 4	540
	11th to 20th	Day	11% 16% 36% 24% 10% 2	532
	21st to end	Day	11% 17% 31% 26% 13% 2	545
May	1st to 10th	Day	13% 13% 28% 27% 16% 3	753
	11th to 20th	Day	12% 7% 29% 28% 20% 4	775
	21st to end	Day	11% 10% 28% 28% 19% 5%	844
June	1st to 10th	Day	7% 5% 22% 31% 26% 10%	780
	11th to 20th	Day	4 6% 27% 35% 23% 5%	780
	21st to end	Day	5% 6% 23% 35% 24% 7%	780
July	1st to 10th	Day	6% 3 16% 34% 30% 11%	771
	11th to 20th	Day	3 2 12% 33% 38% 12%	768
	21st to end	Day	5% 1 10% 30% 39% 14%	849
August	1st to 10th	Day	6% 2 16% 32% 32% 12%	619
	11th to 20th	Day	4 1 16% 34% 32% 11%	557
	21st to end	Day	4 2 16% 39% 27% 12%	627
September	1st to 10th	Day	5% 2 18% 35% 29% 11%	570
	11th to 20th	Day	3 3 19% 37% 27% 11%	438
	21st to end	Day	9% 4 19% 25% 28% 15%	330
October	1st to 10th	Day	8% 4 22% 25% 25% 15%	330
	11th to 20th	Day	5% 5% 31% 31% 19% 8%	330
	21st to end	Day	9% 9% 28% 26% 20% 8%	363
November	1st to 10th	Day	7% 6% 29% 32% 21% 5%	330
	11th to 20th	Day	4 6% 32% 32% 22% 4	330
	21st to end	Day	9% 8% 24% 36% 18% 4	330
December	1st to 10th	Day	7% 5% 30% 38% 16% 4	330
	11th to 20th	Day	5% 9% 30% 36% 18% 2	330
	21st to end	Day	7% 10% 34% 35% 13% 1	363
January	1st to 10th	Night	6% 6% 33% 40% 14% 2	1050
	11th to 20th	Night	5% 8% 36% 38% 12% 1	1050
	21st to end	Night	4 7% 35% 44% 10% 1	968
February	1st to 10th	Night	7% 6% 39% 40% 7%	840
	11th to 20th	Night	7% 7% 41% 36% 9% 1	824
	21st to end	Night	5% 6% 43% 38% 7%	692
March	1st to 10th	Night	7% 8% 36% 39% 9% 1	840
	11th to 20th	Night	9% 7% 34% 37% 10% 1	830
	21st to end	Night	9% 11% 40% 33% 7%	693
April	1st to 10th	Night	9% 11% 42% 33% 5%	630
	11th to 20th	Night	12% 12% 41% 29% 7%	623
	21st to end	Night	14% 15% 30% 31% 10%	630
May	1st to 10th	Night	13% 9% 33% 33% 11%	630
	11th to 20th	Night	13% 7% 30% 34% 15% 1	621
	21st to end	Night	14% 8% 36% 31% 10% 1	683
June	1st to 10th	Night	7% 5% 29% 42% 17% 1	630
	11th to 20th	Night	4 4 38% 42% 11%	630
	21st to end	Night	7% 5% 28% 44% 15%	630
July	1st to 10th	Night	7% 3 20% 46% 24% 1	615
	11th to 20th	Night	5% 2 13% 49% 29% 2	612
	21st to end	Night	8% 1 13% 43% 33% 2	690
August	1st to 10th	Night	8% 2 16% 43% 30% 1	627
	11th to 20th	Night	6% 2 18% 52% 21% 1	624
	21st to end	Night	7% 1 14% 49% 27% 2	693
September	1st to 10th	Night	9% 3 17% 49% 21% 1	630
	11th to 20th	Night	7% 2 22% 42% 24% 2	609
	21st to end	Night	7% 3 24% 43% 22% 2	600
October	1st to 10th	Night	11% 6% 27% 39% 16% 2	636
	11th to 20th	Night	5% 6% 29% 38% 19% 3	800
	21st to end	Night	7% 8% 27% 37% 18% 3	1014
November	1st to 10th	Night	6% 4 29% 43% 17% 2	1025
	11th to 20th	Night	5% 5% 32% 41% 15% 2	1050
	21st to end	Night	7% 7% 29% 40% 15% 2	1050
December	1st to 10th	Night	4 6% 35% 42% 12% 2	1050
	11th to 20th	Night	6% 6% 32% 41% 14% 1	1050
	21st to end	Night	7% 10% 34% 39% 10% 1	1155

Page generated at 2026-09-11 02:11:55. Version ac07

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