Summit Lake State Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Summit Lake State Recreation Area 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	11% 7% 3 7% 4 4 4 4 5% 7% 44%	149157
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 47%	142563
Transparency	Day	39% 4 13% 26% 16% 2	152784
	Night	37% 3 13% 27% 18% 3	146992
Seeing	Day	15% 9% 30% 29% 14% 3	18502
	Night	13% 8% 33% 34% 10% 1	28256

By Month

Percentage Cloud Cover SE (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	9% 12% 4 17% 8% 6% 4 3 4 5% 28%	5289
	11th to 20th	Day	5% 9% 4 11% 6% 6% 6% 4 6% 6% 36%	5310
	21st to end	Day	6% 9% 5% 10% 6% 6% 5% 4 5% 6% 37%	5812
February	1st to 10th	Day	9% 13% 5% 10% 6% 6% 4 4 6% 8% 30%	1890
	11th to 20th	Day	8% 12% 4 9% 4 4 4 3 5% 5% 42%	1875
	21st to end	Day	10% 8% 3 9% 5% 4 4 3 4 7% 43%	1730
March	1st to 10th	Day	13% 9% 3 6% 3 3 3 3 3 4 51%	4953
	11th to 20th	Day	12% 7% 2 4 3 3 4 3 5% 8% 49%	5090
	21st to end	Day	20% 11% 4 9% 4 4 5% 4 6% 6% 27%	5583
April	1st to 10th	Day	15% 9% 3 7% 4 4 3 3 5% 7% 41%	2372
	11th to 20th	Day	17% 9% 2 5% 4 3 3 3 5% 7% 41%	2639
	21st to end	Day	20% 8% 3 6% 4 4 3 4 5% 7% 37%	2730
May	1st to 10th	Day	11% 6% 2 7% 5% 4 4 4 6% 6% 45%	7617
	11th to 20th	Day	14% 6% 2 6% 4 3 3 3 5% 6% 48%	7627
	21st to end	Day	18% 7% 3 7% 4 4 4 4 6% 7% 36%	8747
June	1st to 10th	Day	9% 4 2 6% 4 4 4 4 6% 9% 48%	2940
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 4 6% 9% 47%	2940
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 9% 48%	3060
July	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 9% 43%	7942
	11th to 20th	Day	6% 4 2 5% 3 3 3 3 5% 7% 59%	7680
	21st to end	Day	8% 5% 2 6% 4 4 5% 5% 7% 9% 44%	8337
August	1st to 10th	Day	7% 5% 2 6% 4 4 4 4 6% 8% 50%	6014
	11th to 20th	Day	15% 7% 3 7% 4 4 5% 4 6% 8% 37%	5948
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	6509
September	1st to 10th	Day	12% 5% 2 5% 4 3 4 3 4 5% 52%	2437
	11th to 20th	Day	12% 5% 1 5% 4 4 4 3 5% 7% 51%	2310
	21st to end	Day	12% 4 1 4 3 2 3 3 5% 6% 55%	2288
October	1st to 10th	Day	14% 5% 2 5% 4 2 4 3 4 6% 52%	2050
	11th to 20th	Day	11% 6% 2 4 4 3 3 3 4 5% 56%	2000
	21st to end	Day	13% 8% 3 7% 3 2 3 4 5% 5% 47%	2195
November	1st to 10th	Day	9% 6% 2 6% 3 3 4 3 5% 6% 52%	1853
	11th to 20th	Day	10% 7% 2 8% 5% 4 4 4 5% 7% 45%	1797
	21st to end	Day	12% 9% 3 6% 4 4 2 3 6% 7% 44%	1680
December	1st to 10th	Day	6% 6% 3 6% 5% 5% 5% 3 4 6% 51%	2690
	11th to 20th	Day	8% 10% 3 9% 5% 4 5% 4 5% 7% 39%	3088
	21st to end	Day	17% 9% 4 14% 5% 4 4 3 5% 5% 30%	4135
January	1st to 10th	Night	9% 11% 4 16% 8% 5% 4 3 5% 5% 29%	7634
	11th to 20th	Night	4 7% 3 9% 6% 5% 7% 4 7% 6% 40%	7680
	21st to end	Night	6% 10% 5% 11% 5% 5% 4 4 5% 5% 40%	8402
February	1st to 10th	Night	10% 11% 4 9% 6% 5% 4 3 5% 5% 39%	2730
	11th to 20th	Night	8% 9% 4 8% 4 4 5% 3 6% 7% 42%	2651
	21st to end	Night	8% 7% 3 8% 4 4 3 3 5% 5% 50%	2076
March	1st to 10th	Night	13% 7% 2 5% 3 3 3 2 5% 5% 52%	5124
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 7% 53%	5090
	21st to end	Night	16% 8% 3 8% 5% 4 4 4 5% 8% 35%	5588
April	1st to 10th	Night	13% 7% 2 6% 4 4 3 3 5% 6% 45%	2247
	11th to 20th	Night	12% 7% 2 7% 4 4 3 3 5% 5% 47%	1927
	21st to end	Night	18% 6% 3 6% 4 3 4 3 5% 7% 41%	1890
May	1st to 10th	Night	11% 5% 2 5% 4 3 3 3 5% 6% 53%	5266
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 7% 53%	5265
	21st to end	Night	17% 7% 3 6% 4 4 4 3 5% 7% 41%	5435
June	1st to 10th	Night	7% 5% 1 4 3 3 5% 4 6% 9% 52%	1680
	11th to 20th	Night	8% 5% 1 4 4 4 4 4 5% 9% 53%	1680
	21st to end	Night	6% 4 2 4 3 4 4 4 6% 8% 56%	1535
July	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 5% 9% 51%	4979
	11th to 20th	Night	6% 3 1 4 3 3 3 2 5% 7% 63%	5307
	21st to end	Night	6% 4 2 5% 4 4 5% 4 6% 10% 48%	5770
August	1st to 10th	Night	5% 3 1 4 4 4 4 4 6% 9% 56%	4156
	11th to 20th	Night	12% 5% 2 5% 4 3 4 4 6% 8% 45%	4118
	21st to end	Night	5% 4 2 5% 3 4 4 3 6% 9% 53%	4622
September	1st to 10th	Night	9% 3 2 4 3 3 3 3 4 8% 58%	2179
	11th to 20th	Night	11% 3 1 4 3 3 3 4 5% 7% 57%	2310
	21st to end	Night	12% 5% 1 4 3 3 3 2 4 5% 57%	2288
October	1st to 10th	Night	13% 6% 2 5% 4 3 3 2 5% 5% 51%	2330
	11th to 20th	Night	12% 6% 2 4 3 3 2 2 4 5% 55%	2400
	21st to end	Night	14% 6% 2 5% 3 3 2 3 4 6% 52%	2640
November	1st to 10th	Night	9% 5% 2 5% 3 3 3 3 5% 6% 57%	2665
	11th to 20th	Night	10% 6% 2 6% 4 3 3 4 5% 6% 52%	2819
	21st to end	Night	11% 7% 3 5% 4 3 4 3 5% 6% 49%	2940
December	1st to 10th	Night	5% 7% 3 7% 5% 4 4 3 5% 6% 50%	4720
	11th to 20th	Night	10% 8% 4 7% 4 4 4 4 6% 7% 42%	5339
	21st to end	Night	15% 13% 5% 10% 4 3 4 3 4 6% 33%	7081

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% 2 12% 16% 9% 1	5290
	11th to 20th	Day	47% 3 13% 20% 16% 2	5310
	21st to end	Day	46% 4 16% 23% 10%	5812
February	1st to 10th	Day	53% 4 14% 19% 10% 1	1890
	11th to 20th	Day	45% 3 11% 24% 15% 2	1884
	21st to end	Day	42% 4 11% 26% 14% 3	1730
March	1st to 10th	Day	39% 2 7% 30% 18% 4	4953
	11th to 20th	Day	35% 2 8% 29% 21% 3	5090
	21st to end	Day	57% 3 19% 16% 4 2	5585
April	1st to 10th	Day	44% 3 11% 27% 12% 1	2372
	11th to 20th	Day	44% 3 12% 25% 14% 3	2639
	21st to end	Day	48% 4 9% 26% 13%	2730
May	1st to 10th	Day	39% 3 8% 30% 18% 2	7655
	11th to 20th	Day	38% 3 9% 25% 22% 4	7631
	21st to end	Day	47% 4 11% 22% 15% 1	8761
June	1st to 10th	Day	34% 4 16% 31% 12% 3	2940
	11th to 20th	Day	33% 4 13% 29% 18% 2	2940
	21st to end	Day	34% 4 13% 30% 15% 4	3060
July	1st to 10th	Day	36% 5% 15% 31% 12% 1	7878
	11th to 20th	Day	25% 4 13% 31% 22% 5%	7611
	21st to end	Day	33% 6% 17% 28% 13% 1	8155
August	1st to 10th	Day	31% 5% 14% 31% 18% 2	6000
	11th to 20th	Day	44% 6% 15% 25% 10% 1	5987
	21st to end	Day	33% 5% 16% 27% 16% 3	6508
September	1st to 10th	Day	33% 4 11% 30% 18% 4	2437
	11th to 20th	Day	35% 3 10% 34% 17% 1	2310
	21st to end	Day	30% 3 10% 31% 25% 2	2288
October	1st to 10th	Day	22% 1 6% 23% 43% 3	3336
	11th to 20th	Day	23% 2 14% 30% 24% 7%	3240
	21st to end	Day	37% 2 10% 28% 19% 3	3522
November	1st to 10th	Day	33% 3 16% 26% 19% 2	1853
	11th to 20th	Day	39% 3 14% 27% 17% 1	1797
	21st to end	Day	42% 3 13% 28% 14% 1	1680
December	1st to 10th	Day	35% 3 17% 29% 14% 1	2690
	11th to 20th	Day	45% 3 19% 24% 10%	3085
	21st to end	Day	57% 2 13% 21% 7%	4135
January	1st to 10th	Night	56% 4 12% 17% 10% 1	7635
	11th to 20th	Night	41% 3 14% 24% 16% 2	7680
	21st to end	Night	45% 4 13% 21% 16% 1	8402
February	1st to 10th	Night	47% 3 13% 23% 12% 2	2730
	11th to 20th	Night	41% 3 14% 24% 15% 3	2652
	21st to end	Night	36% 2 12% 26% 20% 3	2076
March	1st to 10th	Night	36% 2 7% 30% 22% 2	5124
	11th to 20th	Night	32% 2 7% 29% 24% 5%	5090
	21st to end	Night	47% 4 18% 24% 6% 1	5588
April	1st to 10th	Night	40% 4 11% 26% 17% 2	2247
	11th to 20th	Night	40% 2 11% 26% 18% 3	1927
	21st to end	Night	42% 3 13% 25% 15% 1	1890
May	1st to 10th	Night	33% 3 8% 28% 25% 3	5293
	11th to 20th	Night	33% 3 10% 21% 26% 6%	5266
	21st to end	Night	44% 4 11% 25% 14% 2	5446
June	1st to 10th	Night	28% 4 15% 34% 15% 4	1680
	11th to 20th	Night	29% 4 13% 27% 22% 5%	1680
	21st to end	Night	27% 4 14% 33% 20% 3	1535
July	1st to 10th	Night	31% 4 16% 34% 14% 2	4936
	11th to 20th	Night	22% 3 13% 34% 23% 5%	5256
	21st to end	Night	30% 6% 20% 28% 15% 1	5641
August	1st to 10th	Night	24% 4 16% 34% 20% 2	4146
	11th to 20th	Night	36% 6% 20% 25% 13% 1	4145
	21st to end	Night	28% 5% 16% 31% 14% 5%	4622
September	1st to 10th	Night	26% 4 11% 31% 23% 5%	2179
	11th to 20th	Night	27% 4 12% 35% 20% 2	2310
	21st to end	Night	32% 2 8% 28% 26% 4	2288
October	1st to 10th	Night	22% 2 6% 18% 48% 4	3811
	11th to 20th	Night	24% 2 8% 30% 29% 7%	3899
	21st to end	Night	35% 2 10% 32% 20% 2	4252
November	1st to 10th	Night	29% 2 15% 27% 22% 4	2665
	11th to 20th	Night	34% 2 13% 30% 18% 3	2819
	21st to end	Night	37% 3 12% 30% 17% 1	2940
December	1st to 10th	Night	35% 3 13% 34% 14% 1	4720
	11th to 20th	Night	40% 5% 15% 29% 10%	5341
	21st to end	Night	55% 3 11% 24% 7% 1	7081

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	18% 11% 34% 27% 10% 1	330
	11th to 20th	Day	16% 13% 39% 26% 5% 1	330
	21st to end	Day	13% 9% 42% 28% 7% 1	363
February	1st to 10th	Day	17% 19% 35% 25% 5%	330
	11th to 20th	Day	17% 16% 33% 26% 7% 1	330
	21st to end	Day	16% 15% 38% 24% 6%	273
March	1st to 10th	Day	15% 15% 41% 22% 4 2	330
	11th to 20th	Day	23% 16% 32% 20% 9% 1	330
	21st to end	Day	32% 14% 32% 18% 3 1	363
April	1st to 10th	Day	21% 17% 38% 21% 3	392
	11th to 20th	Day	21% 18% 31% 23% 6% 1	677
	21st to end	Day	24% 14% 32% 20% 9% 1	750
May	1st to 10th	Day	19% 12% 32% 25% 11% 2	753
	11th to 20th	Day	20% 10% 27% 25% 14% 3	775
	21st to end	Day	19% 8% 28% 28% 15% 3	844
June	1st to 10th	Day	8% 7% 25% 36% 19% 5%	780
	11th to 20th	Day	8% 7% 33% 32% 16% 3	780
	21st to end	Day	10% 8% 32% 31% 16% 3	780
July	1st to 10th	Day	9% 3 20% 35% 25% 8%	771
	11th to 20th	Day	7% 4 22% 37% 23% 8%	768
	21st to end	Day	7% 4 20% 42% 24% 4	849
August	1st to 10th	Day	10% 3 23% 36% 23% 5%	776
	11th to 20th	Day	10% 4 23% 37% 21% 4	765
	21st to end	Day	9% 4 22% 41% 20% 4	826
September	1st to 10th	Day	12% 5% 26% 38% 16% 3	487
	11th to 20th	Day	11% 6% 33% 31% 15% 5%	360
	21st to end	Day	16% 8% 28% 27% 16% 5%	354
October	1st to 10th	Day	18% 6% 32% 25% 14% 5%	330
	11th to 20th	Day	12% 15% 41% 23% 8% 1	330
	21st to end	Day	18% 12% 37% 21% 10% 1	363
November	1st to 10th	Day	15% 12% 38% 24% 9% 2	330
	11th to 20th	Day	15% 14% 40% 24% 8%	330
	21st to end	Day	22% 12% 31% 27% 7% 2	330
December	1st to 10th	Day	11% 15% 36% 27% 10% 1	330
	11th to 20th	Day	16% 12% 35% 27% 9% 1	330
	21st to end	Day	23% 12% 38% 23% 4 1	363
January	1st to 10th	Night	13% 11% 35% 33% 6% 1	1050
	11th to 20th	Night	13% 13% 37% 30% 6%	1050
	21st to end	Night	15% 9% 40% 30% 6%	1155
February	1st to 10th	Night	17% 10% 37% 32% 4	1050
	11th to 20th	Night	13% 11% 40% 32% 4	1017
	21st to end	Night	12% 11% 42% 29% 5%	692
March	1st to 10th	Night	13% 13% 38% 29% 6% 1	677
	11th to 20th	Night	20% 9% 38% 27% 6%	630
	21st to end	Night	20% 11% 37% 27% 5%	693
April	1st to 10th	Night	18% 13% 41% 24% 4	630
	11th to 20th	Night	14% 13% 39% 28% 4	623
	21st to end	Night	20% 10% 33% 30% 7%	630
May	1st to 10th	Night	15% 8% 31% 37% 8%	630
	11th to 20th	Night	14% 9% 30% 35% 11%	621
	21st to end	Night	16% 6% 30% 35% 12%	683
June	1st to 10th	Night	8% 4 26% 46% 15% 1	630
	11th to 20th	Night	9% 4 34% 40% 12% 1	630
	21st to end	Night	7% 4 33% 40% 15%	630
July	1st to 10th	Night	8% 2 19% 42% 29% 1	615
	11th to 20th	Night	4 2 20% 49% 24% 1	612
	21st to end	Night	5% 3 13% 55% 23%	690
August	1st to 10th	Night	7% 3 21% 43% 24% 2	627
	11th to 20th	Night	9% 2 18% 47% 24% 1	624
	21st to end	Night	8% 2 22% 45% 22% 2	693
September	1st to 10th	Night	11% 4 23% 41% 20% 1	630
	11th to 20th	Night	11% 2 30% 40% 16% 1	630
	21st to end	Night	13% 6% 30% 34% 16% 2	624
October	1st to 10th	Night	15% 8% 31% 33% 12% 1	730
	11th to 20th	Night	16% 11% 36% 30% 7%	800
	21st to end	Night	19% 11% 29% 31% 10%	880
November	1st to 10th	Night	11% 10% 35% 35% 8% 1	1025
	11th to 20th	Night	14% 10% 40% 30% 6%	1050
	21st to end	Night	16% 10% 35% 30% 9%	1050
December	1st to 10th	Night	13% 10% 39% 31% 6%	1050
	11th to 20th	Night	16% 10% 36% 32% 7%	1050
	21st to end	Night	19% 11% 35% 29% 6%	1155

Page generated at 2026-09-26 03:18:38. Version ac07

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