Snow King Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Snow King Mountain 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	4 10% 4 8% 5% 4 4 4 5% 7% 45%	159412
	Night	4 11% 4 9% 4 4 4 3 5% 7% 45%	149562
Transparency	Day	37% 5% 12% 21% 17% 8%	154143
	Night	38% 5% 14% 22% 15% 5%	145839
Seeing	Day	12% 19% 32% 25% 10% 2	18290
	Night	12% 10% 26% 36% 15% 1	27733

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 21% 8% 20% 7% 4 4 3 4 5% 21%	4900
	11th to 20th	Day	3 10% 4 12% 6% 4 3 2 4 6% 47%	5340
	21st to end	Day	2 15% 5% 10% 5% 4 4 3 5% 7% 39%	5844
February	1st to 10th	Day	4 22% 9% 15% 6% 5% 4 3 6% 5% 21%	1890
	11th to 20th	Day	3 24% 8% 14% 7% 4 4 2 4 5% 24%	1845
	21st to end	Day	4 21% 9% 17% 7% 3 4 3 4 4 23%	1667
March	1st to 10th	Day	3 20% 6% 14% 4 4 4 3 4 4 33%	4990
	11th to 20th	Day	3 18% 7% 12% 5% 4 3 2 4 5% 37%	5110
	21st to end	Day	5% 24% 8% 14% 6% 6% 5% 3 4 5% 19%	5607
April	1st to 10th	Day	7% 19% 7% 11% 5% 4 4 3 5% 6% 29%	2417
	11th to 20th	Day	7% 16% 5% 11% 7% 5% 4 3 5% 6% 30%	2635
	21st to end	Day	8% 17% 5% 9% 6% 4 5% 5% 6% 7% 28%	2730
May	1st to 10th	Day	6% 10% 2 7% 4 4 5% 4 6% 8% 45%	7626
	11th to 20th	Day	5% 9% 3 8% 5% 5% 6% 5% 6% 7% 41%	7811
	21st to end	Day	8% 10% 3 8% 4 5% 5% 4 6% 7% 40%	9026
June	1st to 10th	Day	10% 7% 2 6% 5% 5% 5% 5% 7% 9% 41%	2940
	11th to 20th	Day	8% 7% 3 7% 4 4 4 4 6% 7% 48%	3114
	21st to end	Day	3 3 1 5% 3 4 4 4 5% 7% 62%	3150
July	1st to 10th	Day	1 2 1 4 3 4 5% 4 6% 7% 63%	8819
	11th to 20th	Day	1 2 1 4 4 4 5% 4 5% 7% 62%	7999
	21st to end	Day	2 3 1 5% 4 5% 6% 5% 8% 9% 52%	8304
August	1st to 10th	Day	2 2 1 3 3 4 4 4 6% 7% 64%	7549
	11th to 20th	Day	3 3 1 5% 4 4 6% 4 6% 9% 55%	7565
	21st to end	Day	5% 4 2 6% 4 4 4 4 5% 8% 54%	8268
September	1st to 10th	Day	4 4 2 4 4 3 3 4 5% 6% 62%	2504
	11th to 20th	Day	7% 5% 2 6% 3 4 4 3 5% 6% 54%	2310
	21st to end	Day	7% 5% 2 5% 3 3 3 2 4 6% 59%	2289
October	1st to 10th	Day	6% 7% 2 5% 3 3 3 2 3 3 63%	3318
	11th to 20th	Day	6% 9% 3 6% 3 3 3 3 5% 5% 54%	3250
	21st to end	Day	6% 14% 4 8% 4 4 4 3 6% 7% 41%	3504
November	1st to 10th	Day	12% 15% 5% 8% 4 3 3 2 5% 6% 37%	1833
	11th to 20th	Day	7% 18% 4 10% 5% 4 3 2 4 6% 36%	1680
	21st to end	Day	3 17% 8% 12% 4 5% 3 3 4 6% 37%	1680
December	1st to 10th	Day	3 14% 6% 9% 5% 4 3 2 4 6% 45%	2700
	11th to 20th	Day	4 20% 8% 17% 7% 4 3 3 4 6% 24%	3106
	21st to end	Day	5% 19% 6% 14% 7% 5% 4 3 5% 7% 24%	4092
January	1st to 10th	Night	2 18% 9% 20% 7% 5% 4 3 5% 7% 20%	8064
	11th to 20th	Night	2 12% 6% 13% 5% 4 4 4 5% 8% 39%	7650
	21st to end	Night	2 17% 5% 9% 5% 4 4 3 5% 9% 38%	8370
February	1st to 10th	Night	4 21% 8% 15% 7% 5% 4 3 5% 5% 23%	2730
	11th to 20th	Night	4 20% 8% 15% 6% 4 4 3 3 4 29%	2662
	21st to end	Night	4 17% 8% 19% 6% 4 3 3 4 6% 25%	2135
March	1st to 10th	Night	2 22% 7% 14% 4 3 3 2 2 5% 35%	5122
	11th to 20th	Night	3 13% 6% 10% 5% 4 4 3 5% 7% 40%	5110
	21st to end	Night	5% 18% 8% 12% 6% 5% 5% 4 5% 6% 27%	5610
April	1st to 10th	Night	6% 16% 5% 9% 4 4 5% 3 4 8% 35%	2202
	11th to 20th	Night	6% 13% 4 9% 6% 5% 6% 4 5% 5% 37%	1928
	21st to end	Night	7% 13% 3 7% 4 3 4 4 5% 8% 41%	1890
May	1st to 10th	Night	6% 12% 2 5% 3 3 3 3 5% 6% 51%	5321
	11th to 20th	Night	5% 7% 2 6% 4 4 4 3 6% 8% 52%	5063
	21st to end	Night	7% 7% 2 5% 3 4 5% 4 6% 9% 49%	5181
June	1st to 10th	Night	8% 8% 2 5% 4 4 5% 3 7% 9% 46%	1680
	11th to 20th	Night	7% 6% 2 5% 3 4 3 3 5% 7% 56%	1499
	21st to end	Night	3 2 1 3 2 3 4 3 5% 7% 67%	1470
July	1st to 10th	Night	1 1 1 3 2 4 4 4 6% 7% 67%	4140
	11th to 20th	Night	1 1 1 3 2 3 4 4 6% 9% 68%	4953
	21st to end	Night	1 2 1 4 3 4 5% 5% 7% 9% 59%	5805
August	1st to 10th	Night	2 2 1 3 2 3 3 3 5% 7% 70%	5273
	11th to 20th	Night	2 2 1 4 4 4 5% 4 7% 10% 57%	5291
	21st to end	Night	5% 4 2 5% 3 3 4 3 7% 8% 56%	5946
September	1st to 10th	Night	5% 4 1 3 2 3 3 3 5% 6% 65%	2113
	11th to 20th	Night	6% 5% 2 5% 3 4 3 4 6% 7% 55%	2310
	21st to end	Night	8% 6% 1 3 2 2 3 2 3 6% 63%	2288
October	1st to 10th	Night	7% 5% 2 3 3 2 2 2 3 5% 66%	3873
	11th to 20th	Night	7% 8% 3 6% 4 3 3 3 4 5% 53%	3898
	21st to end	Night	6% 11% 3 6% 3 3 3 4 5% 8% 47%	4283
November	1st to 10th	Night	11% 14% 4 9% 3 3 3 4 4 5% 40%	2665
	11th to 20th	Night	7% 16% 5% 9% 5% 4 5% 3 5% 6% 36%	2938
	21st to end	Night	4 15% 5% 10% 5% 4 4 3 5% 6% 39%	2940
December	1st to 10th	Night	4 14% 5% 12% 6% 4 3 3 3 4 44%	4710
	11th to 20th	Night	4 20% 8% 15% 6% 3 4 3 5% 6% 26%	5321
	21st to end	Night	4 21% 8% 16% 6% 5% 4 3 4 5% 25%	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	60% 6% 16% 11% 6%	4903
	11th to 20th	Day	38% 4 21% 22% 11% 4	5340
	21st to end	Day	40% 5% 16% 23% 14% 1	5844
February	1st to 10th	Day	64% 6% 12% 13% 4 1	1890
	11th to 20th	Day	62% 6% 12% 13% 6% 2	1854
	21st to end	Day	64% 5% 7% 15% 7% 1	1667
March	1st to 10th	Day	53% 4 10% 18% 12% 3	4990
	11th to 20th	Day	49% 4 15% 24% 8% 1	5110
	21st to end	Day	64% 5% 14% 14% 3	5607
April	1st to 10th	Day	55% 7% 13% 18% 7% 1	2417
	11th to 20th	Day	54% 6% 11% 19% 10% 1	2638
	21st to end	Day	52% 6% 13% 22% 6%	2730
May	1st to 10th	Day	33% 6% 13% 31% 15% 2	7626
	11th to 20th	Day	36% 6% 11% 26% 15% 6%	7814
	21st to end	Day	38% 6% 13% 29% 13% 1	9027
June	1st to 10th	Day	37% 7% 15% 26% 14% 2	2940
	11th to 20th	Day	36% 5% 9% 21% 20% 9%	3114
	21st to end	Day	20% 5% 7% 24% 32% 11%	3150
July	1st to 10th	Day	18% 4 6% 16% 32% 24%	8746
	11th to 20th	Day	17% 4 6% 19% 27% 26%	7923
	21st to end	Day	24% 4 8% 19% 30% 15%	8120
August	1st to 10th	Day	17% 3 6% 16% 27% 32%	5978
	11th to 20th	Day	25% 7% 11% 21% 26% 10%	5964
	21st to end	Day	24% 6% 12% 21% 25% 14%	6487
September	1st to 10th	Day	23% 4 7% 19% 34% 13%	2504
	11th to 20th	Day	30% 5% 9% 23% 26% 7%	2310
	21st to end	Day	28% 4 12% 27% 24% 5%	2289
October	1st to 10th	Day	28% 3 7% 22% 32% 9%	3318
	11th to 20th	Day	32% 3 12% 34% 15% 5%	3250
	21st to end	Day	40% 5% 17% 26% 11% 1	3504
November	1st to 10th	Day	48% 5% 15% 22% 9% 2	1833
	11th to 20th	Day	50% 5% 18% 18% 8% 1	1680
	21st to end	Day	49% 5% 16% 20% 9% 1	1680
December	1st to 10th	Day	41% 4 25% 22% 6% 2	2700
	11th to 20th	Day	61% 3 20% 12% 3	3104
	21st to end	Day	55% 4 15% 12% 7% 6%	4092
January	1st to 10th	Night	59% 5% 13% 17% 6%	8065
	11th to 20th	Night	42% 6% 21% 20% 9% 2	7650
	21st to end	Night	39% 4 17% 25% 12% 2	8370
February	1st to 10th	Night	63% 7% 12% 13% 6%	2730
	11th to 20th	Night	59% 5% 11% 16% 8% 1	2663
	21st to end	Night	61% 5% 9% 16% 7% 2	2135
March	1st to 10th	Night	53% 4 10% 19% 11% 2	5122
	11th to 20th	Night	42% 5% 16% 26% 10% 1	5110
	21st to end	Night	53% 8% 17% 20% 3	5610
April	1st to 10th	Night	47% 8% 15% 18% 10% 2	2202
	11th to 20th	Night	45% 8% 16% 21% 9% 1	1928
	21st to end	Night	40% 7% 16% 29% 8%	1890
May	1st to 10th	Night	31% 4 12% 37% 15% 1	5319
	11th to 20th	Night	27% 4 14% 29% 19% 7%	5064
	21st to end	Night	28% 6% 18% 33% 14% 1	5182
June	1st to 10th	Night	34% 6% 18% 26% 14% 2	1680
	11th to 20th	Night	28% 5% 12% 25% 22% 8%	1499
	21st to end	Night	16% 3 10% 25% 32% 13%	1470
July	1st to 10th	Night	15% 4 9% 17% 39% 17%	4105
	11th to 20th	Night	12% 4 8% 20% 34% 23%	4906
	21st to end	Night	17% 5% 12% 21% 30% 15%	5677
August	1st to 10th	Night	14% 2 6% 15% 33% 30%	4168
	11th to 20th	Night	23% 9% 14% 23% 21% 9%	4168
	21st to end	Night	20% 5% 18% 18% 28% 12%	4658
September	1st to 10th	Night	20% 5% 7% 20% 31% 17%	2113
	11th to 20th	Night	27% 4 12% 23% 25% 9%	2310
	21st to end	Night	24% 4 10% 30% 27% 5%	2288
October	1st to 10th	Night	23% 2 7% 29% 33% 5%	3873
	11th to 20th	Night	32% 3 10% 34% 17% 3	3898
	21st to end	Night	34% 5% 18% 29% 13% 1	4283
November	1st to 10th	Night	45% 6% 14% 24% 9% 2	2665
	11th to 20th	Night	47% 7% 18% 20% 7% 1	2938
	21st to end	Night	44% 7% 16% 21% 10% 2	2940
December	1st to 10th	Night	42% 5% 26% 22% 4 1	4710
	11th to 20th	Night	57% 5% 22% 13% 4	5322
	21st to end	Night	58% 5% 13% 14% 7% 4	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	14% 21% 28% 30% 7% 1	330
	11th to 20th	Day	7% 19% 38% 25% 9% 2	330
	21st to end	Day	7% 17% 37% 32% 7%	363
February	1st to 10th	Day	15% 35% 30% 17% 3	330
	11th to 20th	Day	18% 26% 30% 22% 4	330
	21st to end	Day	16% 29% 34% 16% 4	383
March	1st to 10th	Day	17% 31% 31% 15% 4 1	540
	11th to 20th	Day	16% 26% 33% 20% 5%	540
	21st to end	Day	20% 27% 33% 16% 3	594
April	1st to 10th	Day	19% 26% 29% 19% 5% 1	540
	11th to 20th	Day	18% 28% 33% 16% 5% 1	532
	21st to end	Day	20% 23% 27% 20% 8% 2	540
May	1st to 10th	Day	15% 21% 28% 25% 9% 2	543
	11th to 20th	Day	17% 19% 30% 23% 10% 2	640
	21st to end	Day	19% 13% 25% 26% 14% 3	844
June	1st to 10th	Day	11% 17% 28% 27% 15% 3	780
	11th to 20th	Day	14% 19% 36% 22% 8%	780
	21st to end	Day	7% 13% 32% 31% 15% 2	780
July	1st to 10th	Day	3 10% 32% 37% 16% 2	771
	11th to 20th	Day	4 11% 40% 30% 13% 2	656
	21st to end	Day	4 9% 35% 36% 14% 2	619
August	1st to 10th	Day	5% 13% 38% 32% 11% 1	567
	11th to 20th	Day	4 10% 35% 32% 15% 4	557
	21st to end	Day	7% 16% 32% 26% 15% 4	627
September	1st to 10th	Day	5% 15% 33% 28% 15% 4	570
	11th to 20th	Day	12% 16% 31% 26% 11% 4	570
	21st to end	Day	9% 15% 28% 30% 14% 4	563
October	1st to 10th	Day	12% 17% 26% 24% 16% 5%	365
	11th to 20th	Day	13% 22% 21% 24% 15% 5%	330
	21st to end	Day	14% 22% 29% 26% 7% 2	363
November	1st to 10th	Day	20% 19% 29% 21% 8% 3	330
	11th to 20th	Day	15% 20% 33% 22% 8% 2	330
	21st to end	Day	8% 19% 34% 28% 10% 1	330
December	1st to 10th	Day	18% 15% 29% 26% 11% 1	330
	11th to 20th	Day	18% 22% 33% 22% 5%	330
	21st to end	Day	18% 21% 31% 21% 8% 1	363
January	1st to 10th	Night	13% 14% 28% 35% 9% 1	1004
	11th to 20th	Night	11% 14% 31% 31% 11% 2	840
	21st to end	Night	11% 9% 34% 36% 9% 1	924
February	1st to 10th	Night	12% 17% 36% 29% 6% 1	840
	11th to 20th	Night	12% 13% 33% 33% 8% 1	824
	21st to end	Night	13% 16% 34% 29% 7% 1	692
March	1st to 10th	Night	12% 19% 30% 31% 7% 1	840
	11th to 20th	Night	10% 14% 31% 34% 11% 1	840
	21st to end	Night	14% 14% 32% 31% 9%	924
April	1st to 10th	Night	14% 14% 28% 32% 11% 1	732
	11th to 20th	Night	13% 12% 32% 33% 9%	623
	21st to end	Night	12% 10% 26% 34% 16% 1	630
May	1st to 10th	Night	13% 10% 22% 37% 17% 1	630
	11th to 20th	Night	12% 7% 28% 33% 20% 1	621
	21st to end	Night	14% 10% 21% 38% 17% 1	683
June	1st to 10th	Night	13% 8% 24% 33% 21% 1	630
	11th to 20th	Night	10% 8% 27% 40% 14%	449
	21st to end	Night	4 2 18% 48% 26% 2	420
July	1st to 10th	Night	2 2 15% 49% 30% 2	410
	11th to 20th	Night	2 3 16% 50% 29%	575
	21st to end	Night	2 2 14% 51% 30% 1	690
August	1st to 10th	Night	5% 4 15% 48% 27% 2	627
	11th to 20th	Night	3 1 14% 50% 30% 1	624
	21st to end	Night	5% 4 19% 41% 28% 3	693
September	1st to 10th	Night	6% 4 16% 44% 27% 3	643
	11th to 20th	Night	8% 5% 18% 39% 27% 4	840
	21st to end	Night	11% 3 19% 38% 25% 4	832
October	1st to 10th	Night	13% 8% 20% 36% 20% 3	800
	11th to 20th	Night	15% 10% 19% 35% 19% 2	800
	21st to end	Night	12% 10% 22% 42% 12% 3	880
November	1st to 10th	Night	19% 10% 26% 34% 10% 2	820
	11th to 20th	Night	15% 14% 33% 32% 6% 1	1048
	21st to end	Night	12% 12% 30% 35% 10% 1	1050
December	1st to 10th	Night	17% 12% 29% 34% 6%	1050
	11th to 20th	Night	16% 15% 31% 31% 6%	1050
	21st to end	Night	19% 15% 30% 26% 8% 1	1155

Page generated at 2026-09-26 02:18:38. Version ac07

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