Split Mountain Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Split Mountain Campground clear sky chart from 2005-11-06 to 2025-03-27.

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	4 6% 2 6% 4 4 5% 4 6% 8% 50%	113140
	Night	5% 6% 2 6% 4 4 4 4 6% 8% 51%	115074
Transparency	Day	28% 7% 12% 23% 18% 11%	112899
	Night	30% 7% 12% 24% 18% 9%	114904
Seeing	Day	7% 7% 21% 35% 23% 6%	15893
	Night	8% 4 18% 45% 22% 3	26207

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 6% 3 9% 6% 7% 8% 8% 9% 11% 31%	3939
	11th to 20th	Day	3 6% 2 7% 6% 8% 10% 7% 8% 9% 34%	4100
	21st to end	Day	3 8% 4 11% 5% 6% 8% 8% 7% 8% 32%	4510
February	1st to 10th	Day	4 7% 4 8% 5% 7% 7% 6% 9% 9% 34%	1800
	11th to 20th	Day	5% 9% 3 8% 5% 5% 5% 5% 8% 11% 36%	1755
	21st to end	Day	3 8% 3 9% 5% 6% 5% 5% 6% 9% 41%	1627
March	1st to 10th	Day	5% 13% 3 7% 4 4 5% 4 5% 8% 42%	3554
	11th to 20th	Day	3 9% 3 6% 4 4 4 4 6% 8% 48%	3600
	21st to end	Day	6% 15% 4 8% 6% 5% 5% 5% 8% 8% 30%	3892
April	1st to 10th	Day	5% 8% 2 6% 4 4 5% 4 7% 8% 48%	2228
	11th to 20th	Day	3 8% 2 7% 5% 5% 5% 5% 5% 7% 46%	2251
	21st to end	Day	5% 6% 2 7% 5% 5% 5% 4 6% 9% 46%	2424
May	1st to 10th	Day	9% 10% 3 7% 5% 5% 6% 4 7% 7% 36%	4110
	11th to 20th	Day	4 3 2 5% 4 4 4 5% 8% 10% 51%	4102
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 9% 51%	4825
June	1st to 10th	Day	4 3 1 3 4 3 4 3 7% 10% 58%	2660
	11th to 20th	Day	3 3 2 4 3 3 4 4 6% 8% 60%	2660
	21st to end	Day	3 2 1 3 3 3 3 4 5% 8% 67%	2660
July	1st to 10th	Day	2 2 1 2 2 2 3 3 5% 5% 74%	4430
	11th to 20th	Day	2 3 1 4 4 5% 6% 6% 9% 11% 48%	4115
	21st to end	Day	2 2 1 4 3 4 5% 4 7% 8% 58%	4454
August	1st to 10th	Day	2 3 1 4 4 5% 6% 5% 8% 9% 53%	4092
	11th to 20th	Day	3 2 1 4 3 4 5% 5% 7% 8% 57%	4028
	21st to end	Day	4 3 1 4 3 4 4 4 6% 8% 60%	4275
September	1st to 10th	Day	3 3 1 3 2 2 2 3 5% 7% 67%	2280
	11th to 20th	Day	3 2 1 4 3 3 3 3 5% 7% 65%	2157
	21st to end	Day	6% 2 1 3 3 3 2 2 3 6% 70%	2070
October	1st to 10th	Day	4 3 1 2 2 2 3 2 4 5% 71%	3170
	11th to 20th	Day	6% 5% 2 4 3 3 4 3 5% 8% 56%	3150
	21st to end	Day	5% 4 2 4 3 3 4 4 4 7% 60%	3438
November	1st to 10th	Day	5% 5% 1 4 4 3 4 4 5% 8% 55%	1934
	11th to 20th	Day	4 5% 2 4 3 3 3 3 6% 8% 59%	1600
	21st to end	Day	5% 5% 3 8% 5% 3 3 4 5% 8% 51%	1600
December	1st to 10th	Day	2 5% 2 5% 4 3 3 3 5% 7% 60%	2620
	11th to 20th	Day	3 6% 2 7% 6% 5% 6% 5% 7% 10% 42%	3026
	21st to end	Day	8% 10% 4 9% 6% 6% 6% 5% 7% 8% 30%	4004
January	1st to 10th	Night	2 6% 3 8% 6% 6% 6% 5% 7% 10% 41%	6069
	11th to 20th	Night	2 8% 2 9% 4 4 5% 4 6% 10% 45%	5880
	21st to end	Night	4 9% 4 8% 4 4 4 4 5% 11% 43%	6468
February	1st to 10th	Night	5% 7% 3 7% 4 5% 5% 5% 7% 9% 44%	2600
	11th to 20th	Night	4 8% 3 8% 6% 4 4 4 5% 9% 45%	2532
	21st to end	Night	3 11% 3 6% 5% 4 4 4 5% 8% 46%	1997
March	1st to 10th	Night	5% 11% 5% 7% 5% 4 4 3 5% 7% 44%	3540
	11th to 20th	Night	5% 9% 3 6% 4 4 4 4 6% 7% 50%	3600
	21st to end	Night	10% 14% 4 9% 4 5% 4 4 5% 6% 35%	3899
April	1st to 10th	Night	6% 10% 2 6% 4 4 4 3 5% 7% 48%	1951
	11th to 20th	Night	8% 8% 3 7% 5% 3 5% 5% 7% 8% 41%	1877
	21st to end	Night	9% 6% 3 5% 4 4 4 4 7% 8% 47%	1752
May	1st to 10th	Night	8% 12% 3 6% 4 4 5% 4 6% 7% 42%	2860
	11th to 20th	Night	6% 5% 2 5% 4 4 4 4 6% 9% 51%	2787
	21st to end	Night	9% 6% 2 5% 3 4 4 3 5% 8% 51%	2762
June	1st to 10th	Night	4 4 1 4 3 4 5% 4 7% 8% 54%	1520
	11th to 20th	Night	7% 5% 2 5% 3 3 3 3 5% 7% 58%	1520
	21st to end	Night	2 3 1 3 4 3 5% 4 6% 7% 63%	1520
July	1st to 10th	Night	4 3 1 3 3 3 4 3 5% 6% 65%	2540
	11th to 20th	Night	2 4 1 5% 5% 5% 6% 5% 8% 10% 47%	2850
	21st to end	Night	2 2 1 5% 4 4 4 4 8% 9% 58%	3109
August	1st to 10th	Night	2 3 1 5% 4 4 4 4 7% 9% 56%	2847
	11th to 20th	Night	3 4 2 7% 5% 4 5% 4 6% 7% 52%	2811
	21st to end	Night	5% 3 1 4 4 3 4 4 6% 7% 60%	3390
September	1st to 10th	Night	5% 2 1 3 3 2 4 3 5% 6% 66%	1900
	11th to 20th	Night	6% 3 1 4 3 4 4 4 5% 7% 60%	2020
	21st to end	Night	4 4 1 3 2 3 2 2 5% 5% 68%	2109
October	1st to 10th	Night	5% 2 1 3 3 2 2 2 4 5% 72%	3800
	11th to 20th	Night	6% 4 2 4 3 3 3 3 5% 7% 61%	3778
	21st to end	Night	6% 7% 1 4 3 3 3 3 4 7% 60%	4120
November	1st to 10th	Night	5% 6% 3 6% 3 3 3 3 6% 7% 55%	2362
	11th to 20th	Night	3 4 1 5% 3 3 3 4 5% 9% 60%	2779
	21st to end	Night	5% 6% 2 6% 5% 3 4 3 5% 8% 54%	2800
December	1st to 10th	Night	3 6% 2 5% 3 2 3 2 4 6% 64%	4570
	11th to 20th	Night	4 6% 2 7% 5% 5% 5% 4 6% 9% 46%	5181
	21st to end	Night	6% 9% 4 9% 6% 5% 5% 5% 6% 9% 38%	6974

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	38% 17% 19% 17% 9%	3940
	11th to 20th	Day	37% 11% 18% 22% 10% 3	4100
	21st to end	Day	43% 12% 15% 21% 8% 1	4510
February	1st to 10th	Day	40% 12% 17% 20% 9% 2	1800
	11th to 20th	Day	39% 7% 18% 27% 9%	1764
	21st to end	Day	39% 8% 14% 24% 13% 2	1627
March	1st to 10th	Day	37% 8% 13% 27% 14% 2	3554
	11th to 20th	Day	32% 8% 14% 31% 13% 1	3600
	21st to end	Day	45% 8% 15% 22% 8% 1	3892
April	1st to 10th	Day	32% 7% 15% 24% 17% 6%	2228
	11th to 20th	Day	34% 6% 12% 24% 19% 4	2254
	21st to end	Day	31% 6% 11% 29% 20% 3	2424
May	1st to 10th	Day	39% 6% 9% 22% 20% 5%	4110
	11th to 20th	Day	22% 7% 11% 31% 24% 6%	4105
	21st to end	Day	26% 6% 8% 27% 28% 5%	4825
June	1st to 10th	Day	20% 5% 10% 22% 29% 13%	2660
	11th to 20th	Day	20% 4 7% 16% 27% 26%	2660
	21st to end	Day	15% 3 5% 14% 29% 33%	2660
July	1st to 10th	Day	11% 3 5% 9% 17% 54%	4361
	11th to 20th	Day	23% 5% 7% 15% 26% 24%	4045
	21st to end	Day	20% 5% 7% 15% 20% 33%	4314
August	1st to 10th	Day	24% 6% 9% 25% 17% 20%	4078
	11th to 20th	Day	22% 6% 9% 23% 23% 17%	4067
	21st to end	Day	22% 5% 8% 18% 24% 23%	4274
September	1st to 10th	Day	16% 4 8% 18% 27% 27%	2280
	11th to 20th	Day	18% 4 10% 23% 27% 18%	2157
	21st to end	Day	18% 2 5% 23% 36% 15%	2070
October	1st to 10th	Day	16% 2 7% 20% 30% 23%	3170
	11th to 20th	Day	26% 5% 9% 29% 27% 4	3150
	21st to end	Day	25% 4 15% 35% 19% 3	3438
November	1st to 10th	Day	26% 5% 17% 32% 18% 1	1934
	11th to 20th	Day	25% 4 20% 35% 16%	1600
	21st to end	Day	31% 7% 19% 31% 13%	1600
December	1st to 10th	Day	24% 5% 18% 43% 10%	2620
	11th to 20th	Day	34% 11% 27% 24% 4	3024
	21st to end	Day	47% 10% 17% 18% 8%	4004
January	1st to 10th	Night	34% 10% 18% 27% 9% 2	6069
	11th to 20th	Night	33% 9% 18% 26% 13% 1	5880
	21st to end	Night	37% 11% 17% 20% 14% 1	6468
February	1st to 10th	Night	34% 11% 19% 25% 10% 2	2600
	11th to 20th	Night	37% 7% 16% 25% 13% 1	2533
	21st to end	Night	35% 7% 16% 24% 15% 3	1997
March	1st to 10th	Night	37% 5% 11% 29% 16% 1	3540
	11th to 20th	Night	32% 7% 14% 32% 13% 2	3600
	21st to end	Night	47% 8% 12% 21% 10% 2	3899
April	1st to 10th	Night	35% 5% 12% 24% 19% 7%	1951
	11th to 20th	Night	38% 6% 11% 20% 20% 4	1877
	21st to end	Night	33% 7% 9% 27% 20% 3	1752
May	1st to 10th	Night	38% 7% 8% 17% 23% 7%	2860
	11th to 20th	Night	26% 6% 10% 29% 21% 8%	2788
	21st to end	Night	29% 5% 8% 23% 30% 4	2762
June	1st to 10th	Night	25% 6% 10% 18% 26% 15%	1520
	11th to 20th	Night	27% 4 5% 13% 25% 26%	1520
	21st to end	Night	20% 4 4 11% 26% 35%	1520
July	1st to 10th	Night	19% 5% 5% 9% 15% 48%	2500
	11th to 20th	Night	27% 6% 6% 14% 24% 23%	2797
	21st to end	Night	20% 6% 7% 15% 22% 31%	3011
August	1st to 10th	Night	23% 6% 8% 23% 18% 21%	2838
	11th to 20th	Night	30% 6% 9% 15% 23% 17%	2838
	21st to end	Night	23% 6% 7% 15% 24% 25%	3390
September	1st to 10th	Night	19% 4 6% 17% 26% 29%	1900
	11th to 20th	Night	23% 5% 8% 20% 23% 21%	2020
	21st to end	Night	19% 3 5% 17% 35% 20%	2109
October	1st to 10th	Night	16% 3 5% 17% 33% 26%	3800
	11th to 20th	Night	24% 4 7% 27% 30% 9%	3778
	21st to end	Night	25% 4 10% 35% 24% 3	4120
November	1st to 10th	Night	27% 4 13% 30% 23% 2	2362
	11th to 20th	Night	21% 5% 16% 39% 18% 1	2779
	21st to end	Night	30% 5% 14% 34% 17% 1	2800
December	1st to 10th	Night	23% 4 16% 43% 14%	4570
	11th to 20th	Night	32% 10% 23% 31% 4	5182
	21st to end	Night	41% 11% 16% 23% 9%	6974

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	13% 3 13% 42% 23% 6%	300
	11th to 20th	Day	9% 4 17% 44% 22% 5%	300
	21st to end	Day	8% 3 16% 45% 25% 4	330
February	1st to 10th	Day	10% 6% 22% 49% 11% 2	300
	11th to 20th	Day	8% 4 19% 48% 16% 4	300
	21st to end	Day	8% 6% 20% 48% 15% 2	314
March	1st to 10th	Day	10% 8% 19% 40% 18% 5%	500
	11th to 20th	Day	11% 10% 23% 33% 19% 4	500
	21st to end	Day	12% 12% 26% 36% 11% 2	531
April	1st to 10th	Day	8% 15% 25% 30% 18% 4	460
	11th to 20th	Day	12% 16% 30% 29% 12% 2	452
	21st to end	Day	8% 17% 26% 25% 20% 3	460
May	1st to 10th	Day	9% 15% 32% 25% 17% 2	463
	11th to 20th	Day	8% 12% 24% 30% 23% 4	506
	21st to end	Day	9% 9% 20% 31% 25% 6%	734
June	1st to 10th	Day	5% 6% 20% 31% 31% 7%	680
	11th to 20th	Day	7% 12% 22% 34% 23% 3	680
	21st to end	Day	5% 6% 24% 33% 28% 5%	680
July	1st to 10th	Day	3 4 17% 33% 34% 8%	671
	11th to 20th	Day	3 3 22% 38% 27% 8%	488
	21st to end	Day	3 4 14% 36% 33% 10%	531
August	1st to 10th	Day	5% 3 21% 37% 26% 9%	487
	11th to 20th	Day	4 4 17% 38% 28% 9%	477
	21st to end	Day	4 4 16% 31% 32% 12%	539
September	1st to 10th	Day	5% 5% 14% 31% 30% 14%	490
	11th to 20th	Day	3 9% 25% 28% 26% 10%	490
	21st to end	Day	7% 9% 17% 28% 29% 10%	470
October	1st to 10th	Day	8% 6% 19% 28% 27% 12%	300
	11th to 20th	Day	7% 10% 21% 30% 25% 7%	300
	21st to end	Day	8% 5% 23% 42% 19% 2	330
November	1st to 10th	Day	13% 7% 22% 34% 18% 6%	300
	11th to 20th	Day	6% 5% 28% 42% 13% 6%	300
	21st to end	Day	9% 4 19% 43% 21% 5%	300
December	1st to 10th	Day	7% 2 20% 47% 18% 6%	300
	11th to 20th	Day	5% 3 18% 53% 19% 2	300
	21st to end	Day	15% 6% 19% 40% 16% 5%	330
January	1st to 10th	Night	8% 3 16% 48% 22% 3	885
	11th to 20th	Night	7% 3 18% 52% 18% 3	800
	21st to end	Night	11% 3 18% 49% 16% 3	880
February	1st to 10th	Night	8% 3 24% 51% 13% 2	800
	11th to 20th	Night	8% 4 23% 51% 14% 1	784
	21st to end	Night	7% 5% 25% 50% 12% 1	660
March	1st to 10th	Night	9% 7% 19% 48% 17% 1	800
	11th to 20th	Night	10% 4 20% 46% 19% 1	800
	21st to end	Night	11% 6% 24% 44% 14% 1	862
April	1st to 10th	Night	13% 7% 24% 42% 14%	621
	11th to 20th	Night	13% 7% 27% 38% 13% 2	563
	21st to end	Night	11% 8% 23% 36% 18% 3	570
May	1st to 10th	Night	11% 8% 24% 38% 16% 3	570
	11th to 20th	Night	8% 4 21% 39% 24% 4	561
	21st to end	Night	10% 7% 19% 39% 23% 3	617
June	1st to 10th	Night	5% 4 17% 45% 27% 1	570
	11th to 20th	Night	9% 6% 21% 46% 16% 2	570
	21st to end	Night	4 2 16% 48% 29% 2	570
July	1st to 10th	Night	4 3 13% 37% 40% 3	555
	11th to 20th	Night	4 1 9% 40% 41% 5%	552
	21st to end	Night	4 1 8% 35% 47% 5%	624
August	1st to 10th	Night	4 1 9% 44% 40% 2	567
	11th to 20th	Night	4 3 10% 44% 36% 4	564
	21st to end	Night	4 1 12% 37% 39% 6%	627
September	1st to 10th	Night	5% 3 11% 41% 34% 6%	570
	11th to 20th	Night	7% 2 14% 40% 32% 5%	690
	21st to end	Night	5% 2 17% 35% 31% 9%	760
October	1st to 10th	Night	8% 3 16% 45% 24% 4	760
	11th to 20th	Night	8% 3 17% 43% 26% 4	760
	21st to end	Night	8% 3 19% 44% 23% 4	836
November	1st to 10th	Night	9% 4 16% 46% 24% 2	780
	11th to 20th	Night	5% 2 24% 51% 15% 3	979
	21st to end	Night	8% 4 19% 45% 22% 2	1000
December	1st to 10th	Night	8% 2 19% 54% 15% 2	1000
	11th to 20th	Night	11% 3 18% 51% 16% 1	1000
	21st to end	Night	12% 5% 19% 50% 12% 2	1100

Page generated at 2025-03-24 07:04:26. Version ac07

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