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 2025-05-26.

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%	114300
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 47%	115139
Transparency	Day	40% 3 13% 26% 16% 2	117968
	Night	37% 3 12% 27% 18% 3	119589
Seeing	Day	14% 9% 30% 30% 14% 3	16540
	Night	13% 8% 33% 34% 11% 1	26524

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% 13% 4 19% 9% 6% 4 3 4 5% 24%	4077
	11th to 20th	Day	6% 9% 4 11% 6% 5% 6% 4 6% 6% 37%	4080
	21st to end	Day	7% 9% 5% 11% 6% 6% 6% 3 4 6% 38%	4488
February	1st to 10th	Day	10% 13% 5% 10% 6% 6% 4 4 5% 7% 30%	1800
	11th to 20th	Day	8% 12% 4 9% 5% 4 4 3 5% 5% 41%	1783
	21st to end	Day	10% 9% 3 8% 5% 5% 4 3 5% 7% 42%	1650
March	1st to 10th	Day	13% 9% 2 6% 3 3 3 3 3 4 51%	4845
	11th to 20th	Day	11% 7% 2 4 3 3 4 3 5% 8% 49%	4980
	21st to end	Day	20% 11% 4 9% 4 4 5% 4 6% 6% 27%	5462
April	1st to 10th	Day	14% 8% 3 7% 4 4 3 3 5% 7% 42%	2259
	11th to 20th	Day	18% 9% 2 5% 4 3 3 3 5% 6% 41%	2512
	21st to end	Day	20% 8% 3 6% 4 4 3 4 5% 7% 37%	2600
May	1st to 10th	Day	16% 8% 3 7% 6% 4 4 4 6% 7% 34%	4212
	11th to 20th	Day	13% 7% 2 7% 4 4 3 3 5% 5% 47%	4212
	21st to end	Day	14% 6% 3 6% 5% 5% 5% 4 6% 7% 40%	4730
June	1st to 10th	Day	9% 4 2 6% 4 4 4 4 6% 9% 49%	2660
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 4 6% 8% 45%	2660
	21st to end	Day	8% 5% 2 4 4 4 4 4 6% 9% 49%	2768
July	1st to 10th	Day	13% 5% 2 6% 4 4 5% 4 6% 8% 44%	4257
	11th to 20th	Day	7% 4 2 5% 3 3 4 4 5% 7% 55%	4120
	21st to end	Day	4 3 2 4 3 4 5% 5% 8% 10% 52%	4465
August	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 4 7% 8% 47%	4104
	11th to 20th	Day	16% 7% 2 6% 4 4 4 4 5% 7% 41%	4041
	21st to end	Day	7% 5% 2 6% 4 4 4 4 6% 8% 52%	4478
September	1st to 10th	Day	12% 4 2 5% 4 3 4 3 4 5% 53%	2205
	11th to 20th	Day	10% 5% 2 5% 4 4 4 2 4 6% 54%	2090
	21st to end	Day	11% 4 1 3 3 2 3 3 5% 6% 57%	2090
October	1st to 10th	Day	14% 5% 2 5% 4 2 4 3 3 6% 51%	1948
	11th to 20th	Day	11% 6% 1 4 4 3 3 2 4 5% 57%	1900
	21st to end	Day	13% 8% 2 6% 3 2 3 4 5% 5% 48%	2085
November	1st to 10th	Day	9% 6% 3 6% 3 3 4 3 5% 6% 52%	1763
	11th to 20th	Day	11% 7% 2 8% 5% 4 4 4 5% 7% 45%	1712
	21st to end	Day	12% 8% 3 6% 4 4 3 3 6% 7% 44%	1600
December	1st to 10th	Day	6% 5% 3 6% 4 5% 5% 3 4 6% 53%	2610
	11th to 20th	Day	9% 9% 3 9% 5% 4 5% 4 5% 7% 39%	3008
	21st to end	Day	17% 9% 4 14% 5% 4 3 3 5% 6% 30%	4046
January	1st to 10th	Night	9% 12% 4 19% 9% 6% 5% 3 5% 5% 24%	5888
	11th to 20th	Night	5% 9% 3 10% 6% 5% 7% 4 7% 5% 38%	5900
	21st to end	Night	7% 9% 5% 11% 5% 5% 4 4 5% 6% 39%	6490
February	1st to 10th	Night	10% 11% 4 9% 6% 4 4 3 5% 5% 39%	2600
	11th to 20th	Night	8% 9% 4 8% 4 4 5% 3 6% 7% 42%	2522
	21st to end	Night	8% 7% 3 8% 4 4 3 3 5% 5% 50%	1980
March	1st to 10th	Night	13% 7% 2 5% 3 3 3 2 5% 5% 52%	5012
	11th to 20th	Night	12% 5% 2 4 3 3 4 3 4 7% 54%	4980
	21st to end	Night	16% 8% 3 8% 5% 4 4 4 5% 7% 35%	5467
April	1st to 10th	Night	13% 7% 2 7% 4 3 3 3 6% 7% 45%	2140
	11th to 20th	Night	13% 7% 2 7% 4 4 3 3 5% 6% 47%	1834
	21st to end	Night	17% 6% 3 6% 4 3 4 3 5% 7% 42%	1800
May	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 5% 6% 46%	2913
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 6% 7% 51%	2913
	21st to end	Night	15% 6% 2 6% 4 4 4 4 5% 7% 43%	2950
June	1st to 10th	Night	7% 4 1 4 3 3 5% 4 6% 10% 54%	1520
	11th to 20th	Night	8% 5% 1 4 4 4 4 4 5% 9% 52%	1520
	21st to end	Night	4 4 2 4 3 4 4 4 6% 8% 58%	1389
July	1st to 10th	Night	8% 4 1 4 4 3 3 4 5% 9% 54%	2672
	11th to 20th	Night	6% 2 1 3 2 3 3 3 6% 8% 64%	2850
	21st to end	Night	3 3 1 3 3 3 4 4 6% 10% 59%	3098
August	1st to 10th	Night	4 4 1 4 4 4 4 4 6% 10% 54%	2836
	11th to 20th	Night	12% 5% 1 4 3 3 4 3 6% 7% 51%	2798
	21st to end	Night	6% 5% 2 5% 3 4 4 3 5% 7% 55%	3187
September	1st to 10th	Night	9% 3 2 4 3 3 3 3 4 7% 60%	1971
	11th to 20th	Night	9% 3 1 3 3 2 3 3 5% 7% 59%	2090
	21st to end	Night	10% 5% 1 4 3 3 3 2 4 5% 60%	2090
October	1st to 10th	Night	13% 6% 2 5% 3 3 4 3 5% 6% 51%	2213
	11th to 20th	Night	12% 6% 2 4 3 3 2 2 4 5% 56%	2280
	21st to end	Night	14% 6% 2 5% 3 3 2 3 4 6% 52%	2508
November	1st to 10th	Night	9% 4 2 4 3 3 4 3 5% 6% 57%	2535
	11th to 20th	Night	10% 6% 2 5% 4 3 3 4 5% 6% 52%	2685
	21st to end	Night	11% 8% 3 5% 4 3 4 3 5% 6% 50%	2800
December	1st to 10th	Night	5% 7% 2 7% 5% 4 4 3 5% 6% 51%	4580
	11th to 20th	Night	10% 8% 4 7% 4 4 4 4 6% 7% 42%	5199
	21st to end	Night	15% 13% 5% 10% 4 3 4 3 4 6% 32%	6929

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	63% 2 10% 18% 6%	4078
	11th to 20th	Day	48% 3 13% 20% 15% 2	4080
	21st to end	Day	47% 5% 15% 23% 10% 1	4488
February	1st to 10th	Day	53% 4 14% 19% 10% 1	1800
	11th to 20th	Day	46% 3 11% 22% 15% 2	1792
	21st to end	Day	43% 4 11% 25% 14% 3	1650
March	1st to 10th	Day	39% 2 7% 30% 18% 4	4845
	11th to 20th	Day	35% 2 8% 30% 22% 3	4980
	21st to end	Day	57% 3 19% 16% 3 2	5464
April	1st to 10th	Day	43% 3 11% 28% 13% 2	2259
	11th to 20th	Day	44% 3 13% 24% 14% 3	2512
	21st to end	Day	48% 4 9% 26% 13% 1	2600
May	1st to 10th	Day	49% 3 10% 23% 13% 2	4250
	11th to 20th	Day	41% 3 10% 28% 17% 2	4216
	21st to end	Day	43% 4 13% 22% 16% 1	4743
June	1st to 10th	Day	32% 4 17% 31% 13% 3	2660
	11th to 20th	Day	35% 5% 13% 29% 16% 2	2660
	21st to end	Day	32% 4 14% 32% 15% 4	2768
July	1st to 10th	Day	38% 4 12% 30% 14% 1	4193
	11th to 20th	Day	29% 3 13% 32% 20% 3	4051
	21st to end	Day	23% 7% 17% 29% 22% 3	4325
August	1st to 10th	Day	33% 5% 14% 29% 17% 3	4090
	11th to 20th	Day	42% 4 11% 28% 14% 1	4080
	21st to end	Day	31% 5% 14% 26% 19% 5%	4477
September	1st to 10th	Day	32% 3 11% 31% 19% 4	2205
	11th to 20th	Day	33% 2 10% 35% 19% 1	2090
	21st to end	Day	28% 3 10% 32% 26% 1	2090
October	1st to 10th	Day	22% 1 6% 23% 44% 4	3234
	11th to 20th	Day	22% 2 14% 31% 24% 8%	3140
	21st to end	Day	36% 2 10% 28% 20% 4	3412
November	1st to 10th	Day	33% 3 16% 26% 19% 2	1763
	11th to 20th	Day	40% 3 13% 27% 17% 1	1712
	21st to end	Day	41% 3 13% 28% 14% 2	1600
December	1st to 10th	Day	34% 3 17% 30% 15% 1	2610
	11th to 20th	Day	45% 3 19% 23% 10%	3005
	21st to end	Day	57% 2 12% 21% 7%	4046
January	1st to 10th	Night	62% 3 10% 15% 10%	5888
	11th to 20th	Night	44% 3 15% 21% 15% 2	5900
	21st to end	Night	46% 4 11% 22% 15% 1	6490
February	1st to 10th	Night	47% 3 13% 22% 13% 2	2600
	11th to 20th	Night	42% 3 14% 24% 15% 3	2523
	21st to end	Night	37% 2 12% 26% 20% 4	1980
March	1st to 10th	Night	36% 2 7% 30% 22% 2	5012
	11th to 20th	Night	32% 2 6% 29% 25% 5%	4980
	21st to end	Night	48% 4 18% 24% 5% 1	5467
April	1st to 10th	Night	39% 4 11% 25% 18% 2	2140
	11th to 20th	Night	41% 2 11% 26% 17% 3	1834
	21st to end	Night	42% 4 13% 25% 15% 1	1800
May	1st to 10th	Night	40% 3 11% 27% 18% 2	2940
	11th to 20th	Night	34% 3 12% 25% 23% 4	2914
	21st to end	Night	42% 3 13% 22% 17% 3	2958
June	1st to 10th	Night	26% 4 15% 35% 15% 4	1520
	11th to 20th	Night	30% 4 13% 28% 20% 5%	1520
	21st to end	Night	24% 4 15% 34% 19% 3	1389
July	1st to 10th	Night	27% 4 16% 35% 16% 2	2627
	11th to 20th	Night	19% 4 16% 37% 21% 4	2796
	21st to end	Night	19% 7% 17% 33% 22% 2	2999
August	1st to 10th	Night	25% 3 16% 34% 19% 3	2826
	11th to 20th	Night	33% 4 15% 28% 18% 2	2825
	21st to end	Night	29% 4 14% 27% 18% 8%	3187
September	1st to 10th	Night	25% 3 10% 32% 24% 5%	1971
	11th to 20th	Night	24% 4 12% 36% 21% 3	2090
	21st to end	Night	29% 2 8% 30% 27% 4	2090
October	1st to 10th	Night	22% 1 6% 18% 49% 4	3694
	11th to 20th	Night	23% 2 8% 30% 29% 7%	3779
	21st to end	Night	34% 2 10% 33% 20% 2	4120
November	1st to 10th	Night	29% 2 16% 26% 22% 4	2535
	11th to 20th	Night	34% 2 13% 30% 18% 3	2685
	21st to end	Night	36% 3 12% 31% 17% 2	2800
December	1st to 10th	Night	34% 3 13% 35% 14% 1	4580
	11th to 20th	Night	40% 5% 16% 29% 10%	5201
	21st to end	Night	55% 3 10% 24% 7% 1	6929

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	17% 11% 34% 27% 10% 1	300
	11th to 20th	Day	16% 12% 38% 28% 5% 1	300
	21st to end	Day	13% 8% 42% 28% 8% 1	330
February	1st to 10th	Day	18% 18% 34% 26% 5%	300
	11th to 20th	Day	17% 16% 32% 26% 7% 1	300
	21st to end	Day	17% 15% 38% 24% 5%	249
March	1st to 10th	Day	15% 16% 40% 22% 4 3	300
	11th to 20th	Day	23% 15% 34% 20% 8% 1	300
	21st to end	Day	33% 12% 32% 18% 3 1	330
April	1st to 10th	Day	20% 16% 39% 22% 3	359
	11th to 20th	Day	22% 17% 31% 23% 7% 1	630
	21st to end	Day	24% 15% 31% 19% 10% 1	700
May	1st to 10th	Day	20% 12% 30% 25% 11% 3	703
	11th to 20th	Day	19% 10% 27% 26% 14% 3	725
	21st to end	Day	18% 8% 28% 28% 14% 3	760
June	1st to 10th	Day	7% 7% 25% 37% 19% 5%	680
	11th to 20th	Day	9% 6% 32% 33% 16% 4	680
	21st to end	Day	8% 8% 31% 33% 16% 3	680
July	1st to 10th	Day	9% 3 19% 35% 26% 8%	671
	11th to 20th	Day	7% 4 23% 38% 22% 7%	668
	21st to end	Day	5% 4 19% 43% 26% 4	739
August	1st to 10th	Day	9% 3 22% 36% 24% 5%	676
	11th to 20th	Day	11% 4 23% 37% 23% 3	665
	21st to end	Day	9% 4 21% 40% 22% 4	720
September	1st to 10th	Day	12% 4 25% 39% 16% 3	415
	11th to 20th	Day	8% 5% 33% 32% 16% 5%	300
	21st to end	Day	13% 8% 30% 30% 16% 4	300
October	1st to 10th	Day	18% 5% 33% 24% 15% 6%	300
	11th to 20th	Day	12% 15% 38% 25% 9% 1	300
	21st to end	Day	16% 12% 38% 22% 11% 1	330
November	1st to 10th	Day	15% 12% 37% 23% 10% 2	300
	11th to 20th	Day	15% 14% 39% 24% 7%	300
	21st to end	Day	21% 12% 31% 28% 7% 2	300
December	1st to 10th	Day	10% 14% 37% 27% 10% 1	300
	11th to 20th	Day	15% 12% 35% 28% 9% 1	300
	21st to end	Day	24% 12% 38% 21% 4 1	330
January	1st to 10th	Night	13% 12% 35% 33% 7% 1	1000
	11th to 20th	Night	13% 13% 37% 30% 7%	1000
	21st to end	Night	16% 8% 40% 30% 6%	1100
February	1st to 10th	Night	17% 10% 37% 32% 4	1000
	11th to 20th	Night	13% 11% 40% 31% 4	968
	21st to end	Night	12% 11% 41% 29% 6%	660
March	1st to 10th	Night	13% 13% 38% 29% 7% 1	645
	11th to 20th	Night	20% 9% 38% 27% 6%	600
	21st to end	Night	21% 12% 36% 27% 5%	660
April	1st to 10th	Night	18% 14% 40% 25% 4	600
	11th to 20th	Night	15% 13% 39% 28% 5%	593
	21st to end	Night	20% 10% 34% 30% 7%	600
May	1st to 10th	Night	16% 8% 30% 37% 9%	600
	11th to 20th	Night	14% 9% 30% 36% 11%	591
	21st to end	Night	15% 6% 31% 35% 12%	634
June	1st to 10th	Night	8% 4 26% 46% 16% 1	570
	11th to 20th	Night	9% 4 34% 40% 12% 1	570
	21st to end	Night	5% 3 34% 42% 17%	570
July	1st to 10th	Night	7% 2 19% 41% 30% 1	555
	11th to 20th	Night	3 2 21% 49% 24% 1	552
	21st to end	Night	4 2 13% 55% 25%	624
August	1st to 10th	Night	7% 2 21% 42% 25% 2	567
	11th to 20th	Night	9% 2 19% 47% 22% 1	564
	21st to end	Night	8% 2 22% 43% 22% 3	627
September	1st to 10th	Night	11% 3 24% 40% 22% 1	570
	11th to 20th	Night	10% 2 30% 40% 16% 1	570
	21st to end	Night	10% 6% 32% 35% 15% 2	570
October	1st to 10th	Night	15% 8% 31% 33% 12% 1	693
	11th to 20th	Night	16% 11% 36% 30% 8%	760
	21st to end	Night	18% 11% 28% 32% 10%	836
November	1st to 10th	Night	11% 10% 34% 36% 8% 1	975
	11th to 20th	Night	14% 10% 40% 29% 6% 1	1000
	21st to end	Night	15% 10% 36% 30% 9%	1000
December	1st to 10th	Night	13% 11% 39% 31% 6%	1000
	11th to 20th	Night	16% 9% 35% 32% 7%	1000
	21st to end	Night	19% 11% 35% 28% 6%	1100

Page generated at 2025-05-23 08:21:00. Version ac07

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