Jackson Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jackson Lake State Park clear sky chart from 2005-11-06 to 2026-07-01.

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% 5% 2 5% 4 4 4 4 6% 8% 54%	146554
	Night	6% 6% 2 6% 4 4 4 3 5% 7% 52%	143303
Transparency	Day	27% 5% 10% 26% 23% 9%	141487
	Night	30% 5% 11% 25% 22% 7%	139382
Seeing	Day	8% 6% 21% 33% 23% 8%	17925
	Night	9% 6% 26% 45% 14% 1	27918

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	3 8% 3 7% 4 4 4 3 4 6% 56%	4720
	11th to 20th	Day	2 5% 2 6% 5% 4 4 4 6% 8% 54%	4740
	21st to end	Day	3 7% 3 7% 4 3 3 4 5% 7% 56%	5706
February	1st to 10th	Day	3 9% 4 6% 6% 4 4 3 6% 8% 47%	1914
	11th to 20th	Day	2 7% 3 8% 4 4 4 4 5% 7% 50%	2049
	21st to end	Day	3 6% 3 6% 5% 3 3 4 5% 7% 54%	1730
March	1st to 10th	Day	4 9% 2 5% 3 3 3 3 4 8% 55%	4600
	11th to 20th	Day	7% 6% 2 5% 4 3 4 3 5% 7% 55%	4866
	21st to end	Day	5% 7% 2 6% 4 5% 5% 4 6% 9% 47%	6055
April	1st to 10th	Day	7% 6% 2 5% 4 4 4 4 6% 7% 53%	2520
	11th to 20th	Day	10% 8% 3 6% 4 4 4 3 6% 7% 46%	2491
	21st to end	Day	9% 6% 2 6% 4 4 4 5% 7% 9% 45%	2530
May	1st to 10th	Day	9% 6% 2 6% 4 4 4 3 5% 7% 50%	7655
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 8% 49%	8022
	21st to end	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 47%	9026
June	1st to 10th	Day	5% 4 1 4 3 4 5% 4 7% 9% 54%	2940
	11th to 20th	Day	5% 3 1 4 4 4 5% 4 7% 8% 55%	2940
	21st to end	Day	4 3 1 4 3 4 4 4 8% 9% 57%	2940
July	1st to 10th	Day	5% 3 1 4 3 3 4 3 6% 9% 60%	6340
	11th to 20th	Day	3 2 1 4 4 4 5% 5% 8% 11% 52%	6340
	21st to end	Day	3 3 1 5% 4 4 5% 5% 7% 10% 52%	6903
August	1st to 10th	Day	7% 3 1 4 3 4 5% 5% 7% 11% 50%	5824
	11th to 20th	Day	2 2 1 4 3 3 4 4 6% 8% 62%	5366
	21st to end	Day	7% 4 2 6% 4 4 5% 4 6% 9% 50%	5984
September	1st to 10th	Day	4 2 1 3 2 3 3 3 4 8% 66%	2400
	11th to 20th	Day	6% 2 1 3 3 3 4 3 5% 7% 62%	2331
	21st to end	Day	8% 2 1 3 2 3 4 2 4 6% 65%	2200
October	1st to 10th	Day	6% 3 1 2 2 2 2 1 3 4 76%	3408
	11th to 20th	Day	4 4 2 5% 3 2 3 3 5% 6% 64%	3250
	21st to end	Day	6% 5% 1 4 2 3 3 3 5% 7% 60%	3298
November	1st to 10th	Day	3 4 1 5% 3 3 4 4 5% 7% 60%	1853
	11th to 20th	Day	4 6% 2 5% 3 4 3 2 5% 8% 59%	1890
	21st to end	Day	4 6% 3 5% 3 3 4 3 4 6% 59%	1825
December	1st to 10th	Day	2 4 2 5% 3 3 4 3 4 6% 63%	2700
	11th to 20th	Day	3 6% 2 4 3 4 3 3 4 6% 62%	3106
	21st to end	Day	6% 8% 2 5% 4 5% 4 3 5% 8% 49%	4092
January	1st to 10th	Night	4 9% 3 8% 4 4 4 3 5% 7% 49%	8201
	11th to 20th	Night	2 8% 2 7% 4 3 4 4 6% 6% 54%	8250
	21st to end	Night	2 7% 3 7% 4 4 4 3 4 6% 55%	8553
February	1st to 10th	Night	4 8% 4 7% 4 3 4 4 5% 7% 49%	2704
	11th to 20th	Night	4 9% 3 7% 5% 4 5% 4 6% 8% 46%	2458
	21st to end	Night	3 8% 3 6% 3 4 3 3 5% 6% 56%	2076
March	1st to 10th	Night	5% 9% 3 6% 4 3 4 3 4 5% 54%	5494
	11th to 20th	Night	8% 8% 2 5% 4 4 3 3 4 5% 54%	5340
	21st to end	Night	10% 8% 3 6% 4 4 5% 4 6% 7% 42%	5141
April	1st to 10th	Night	7% 8% 2 6% 4 4 4 4 5% 6% 51%	2100
	11th to 20th	Night	13% 8% 2 6% 5% 3 4 3 4 7% 45%	2077
	21st to end	Night	14% 7% 2 7% 5% 4 4 3 6% 7% 41%	2089
May	1st to 10th	Night	13% 7% 3 6% 4 4 4 3 5% 7% 44%	5292
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 6% 8% 47%	4853
	21st to end	Night	13% 7% 2 6% 4 4 5% 3 6% 8% 42%	5181
June	1st to 10th	Night	7% 3 1 4 4 3 3 4 8% 10% 51%	1680
	11th to 20th	Night	6% 4 1 4 4 4 5% 4 6% 8% 54%	1680
	21st to end	Night	6% 4 1 5% 4 5% 4 4 7% 8% 52%	1680
July	1st to 10th	Night	4 3 1 4 4 4 5% 4 6% 8% 57%	3640
	11th to 20th	Night	5% 3 2 5% 4 5% 5% 5% 7% 11% 49%	3640
	21st to end	Night	5% 4 2 6% 5% 6% 5% 5% 7% 9% 47%	3970
August	1st to 10th	Night	9% 4 2 6% 5% 5% 6% 4 7% 8% 43%	3971
	11th to 20th	Night	3 4 2 6% 4 6% 5% 5% 7% 9% 50%	4483
	21st to end	Night	8% 4 2 6% 4 5% 6% 5% 8% 8% 44%	4993
September	1st to 10th	Night	6% 4 2 5% 3 3 5% 3 5% 9% 57%	2000
	11th to 20th	Night	5% 4 2 5% 3 3 4 3 6% 7% 57%	2068
	21st to end	Night	7% 2 1 4 3 3 3 3 4 6% 64%	2200
October	1st to 10th	Night	6% 3 1 3 2 2 2 2 4 5% 70%	3775
	11th to 20th	Night	8% 3 2 4 3 3 3 3 5% 6% 60%	3898
	21st to end	Night	6% 5% 2 4 2 3 3 2 4 6% 61%	4469
November	1st to 10th	Night	4 4 2 4 3 4 3 3 5% 7% 61%	2665
	11th to 20th	Night	4 6% 2 4 3 3 4 3 5% 7% 58%	2730
	21st to end	Night	6% 7% 2 5% 4 3 4 3 5% 7% 55%	2793
December	1st to 10th	Night	2 5% 1 5% 3 3 3 2 4 5% 66%	4710
	11th to 20th	Night	2 5% 2 5% 4 4 4 3 6% 7% 59%	5321
	21st to end	Night	6% 10% 3 7% 4 4 4 4 5% 7% 47%	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	31% 3 8% 33% 21% 5%	4723
	11th to 20th	Day	27% 4 12% 27% 23% 7%	4740
	21st to end	Day	28% 4 9% 27% 25% 7%	5706
February	1st to 10th	Day	35% 5% 11% 27% 18% 5%	1914
	11th to 20th	Day	33% 4 9% 27% 21% 5%	2059
	21st to end	Day	28% 5% 8% 26% 24% 10%	1730
March	1st to 10th	Day	28% 4 6% 19% 32% 11%	4600
	11th to 20th	Day	28% 5% 10% 23% 28% 6%	4866
	21st to end	Day	30% 7% 14% 33% 14% 2	6055
April	1st to 10th	Day	30% 5% 12% 25% 20% 8%	2520
	11th to 20th	Day	35% 5% 11% 22% 18% 8%	2494
	21st to end	Day	34% 7% 10% 27% 19% 3	2530
May	1st to 10th	Day	33% 5% 8% 30% 19% 4	7655
	11th to 20th	Day	31% 5% 9% 24% 22% 9%	8026
	21st to end	Day	33% 6% 11% 25% 19% 5%	9027
June	1st to 10th	Day	24% 7% 18% 25% 19% 7%	2940
	11th to 20th	Day	25% 6% 10% 22% 24% 13%	2940
	21st to end	Day	20% 6% 11% 25% 26% 13%	2940
July	1st to 10th	Day	21% 5% 8% 19% 32% 16%	6272
	11th to 20th	Day	23% 6% 12% 27% 21% 11%	6265
	21st to end	Day	26% 7% 12% 21% 17% 18%	6705
August	1st to 10th	Day	28% 7% 15% 27% 16% 8%	4236
	11th to 20th	Day	24% 6% 12% 20% 25% 13%	3882
	21st to end	Day	22% 5% 11% 21% 26% 16%	4311
September	1st to 10th	Day	18% 4 7% 24% 28% 18%	2400
	11th to 20th	Day	21% 5% 8% 21% 29% 16%	2331
	21st to end	Day	22% 4 6% 23% 34% 11%	2200
October	1st to 10th	Day	15% 2 5% 18% 33% 27%	3408
	11th to 20th	Day	22% 3 8% 29% 28% 10%	3250
	21st to end	Day	24% 3 6% 28% 30% 9%	3298
November	1st to 10th	Day	22% 4 11% 27% 26% 10%	1853
	11th to 20th	Day	24% 4 6% 29% 30% 7%	1890
	21st to end	Day	26% 3 9% 26% 28% 8%	1825
December	1st to 10th	Day	23% 3 8% 34% 26% 6%	2700
	11th to 20th	Day	23% 4 8% 35% 26% 5%	3104
	21st to end	Day	33% 4 10% 29% 18% 6%	4092
January	1st to 10th	Night	34% 4 10% 28% 19% 4	8202
	11th to 20th	Night	29% 5% 9% 26% 25% 7%	8250
	21st to end	Night	30% 5% 9% 26% 25% 5%	8553
February	1st to 10th	Night	33% 6% 12% 25% 20% 4	2704
	11th to 20th	Night	35% 5% 12% 26% 18% 4	2458
	21st to end	Night	29% 4 8% 25% 25% 10%	2076
March	1st to 10th	Night	31% 5% 5% 18% 32% 8%	5494
	11th to 20th	Night	32% 4 10% 18% 27% 8%	5340
	21st to end	Night	39% 6% 12% 29% 12% 2	5141
April	1st to 10th	Night	33% 7% 9% 25% 20% 7%	2100
	11th to 20th	Night	38% 5% 11% 21% 18% 6%	2077
	21st to end	Night	41% 6% 10% 24% 17% 3	2089
May	1st to 10th	Night	38% 7% 12% 29% 12% 3	5293
	11th to 20th	Night	34% 6% 15% 24% 15% 7%	4854
	21st to end	Night	39% 8% 17% 21% 12% 3	5182
June	1st to 10th	Night	26% 7% 23% 27% 13% 5%	1680
	11th to 20th	Night	27% 8% 13% 23% 18% 11%	1680
	21st to end	Night	28% 6% 11% 27% 21% 7%	1680
July	1st to 10th	Night	24% 5% 11% 23% 30% 6%	3600
	11th to 20th	Night	27% 6% 18% 24% 20% 5%	3592
	21st to end	Night	31% 7% 14% 20% 19% 9%	3856
August	1st to 10th	Night	39% 9% 17% 19% 12% 4	2883
	11th to 20th	Night	32% 8% 15% 21% 15% 9%	3243
	21st to end	Night	26% 7% 16% 22% 21% 8%	3597
September	1st to 10th	Night	24% 5% 10% 22% 24% 15%	2000
	11th to 20th	Night	24% 5% 10% 25% 22% 14%	2068
	21st to end	Night	22% 4 8% 24% 28% 13%	2200
October	1st to 10th	Night	18% 3 6% 18% 31% 23%	3775
	11th to 20th	Night	24% 5% 8% 28% 27% 8%	3898
	21st to end	Night	25% 3 8% 27% 27% 10%	4469
November	1st to 10th	Night	23% 4 9% 27% 26% 11%	2665
	11th to 20th	Night	24% 4 8% 29% 26% 9%	2730
	21st to end	Night	29% 3 9% 25% 27% 6%	2793
December	1st to 10th	Night	21% 3 9% 35% 27% 5%	4710
	11th to 20th	Night	24% 4 5% 38% 25% 4	5322
	21st to end	Night	37% 4 8% 27% 22% 3	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	7% 6% 18% 44% 20% 5%	330
	11th to 20th	Day	10% 8% 22% 40% 19% 2	330
	21st to end	Day	5% 8% 26% 46% 12% 4	363
February	1st to 10th	Day	7% 8% 30% 43% 9% 2	330
	11th to 20th	Day	5% 7% 27% 45% 15% 1	330
	21st to end	Day	5% 9% 24% 49% 10% 2	273
March	1st to 10th	Day	8% 8% 23% 38% 18% 4	330
	11th to 20th	Day	10% 11% 25% 35% 16% 3	426
	21st to end	Day	9% 13% 30% 32% 13% 2	594
April	1st to 10th	Day	13% 14% 28% 29% 13% 4	540
	11th to 20th	Day	16% 15% 26% 27% 14% 2	532
	21st to end	Day	12% 14% 29% 24% 17% 4	550
May	1st to 10th	Day	16% 9% 23% 30% 18% 5%	753
	11th to 20th	Day	15% 6% 22% 29% 22% 6%	775
	21st to end	Day	11% 8% 22% 29% 21% 9%	844
June	1st to 10th	Day	7% 4 20% 29% 29% 12%	780
	11th to 20th	Day	6% 6% 28% 32% 23% 6%	780
	21st to end	Day	6% 4 20% 35% 27% 8%	780
July	1st to 10th	Day	8% 2 15% 28% 36% 11%	722
	11th to 20th	Day	4 3 14% 29% 39% 12%	718
	21st to end	Day	5% 2 11% 29% 39% 13%	794
August	1st to 10th	Day	6% 3 15% 30% 35% 12%	594
	11th to 20th	Day	3 2 20% 30% 30% 16%	517
	21st to end	Day	4 2 18% 33% 29% 14%	583
September	1st to 10th	Day	5% 2 16% 31% 30% 16%	530
	11th to 20th	Day	6% 3 16% 27% 31% 17%	461
	21st to end	Day	9% 2 15% 28% 28% 18%	330
October	1st to 10th	Day	10% 5% 16% 24% 29% 16%	330
	11th to 20th	Day	5% 6% 24% 36% 20% 8%	330
	21st to end	Day	9% 8% 23% 34% 20% 6%	363
November	1st to 10th	Day	7% 6% 22% 40% 18% 8%	330
	11th to 20th	Day	5% 6% 20% 43% 22% 4	330
	21st to end	Day	10% 8% 13% 43% 20% 5%	330
December	1st to 10th	Day	6% 8% 23% 39% 21% 3	330
	11th to 20th	Day	7% 6% 28% 45% 14%	330
	21st to end	Day	9% 7% 21% 47% 14% 2	363
January	1st to 10th	Night	7% 6% 27% 47% 12% 1	1050
	11th to 20th	Night	6% 8% 33% 42% 10%	1050
	21st to end	Night	7% 5% 31% 46% 10% 1	990
February	1st to 10th	Night	8% 5% 38% 42% 7%	840
	11th to 20th	Night	7% 6% 35% 44% 8%	824
	21st to end	Night	7% 6% 38% 45% 4	692
March	1st to 10th	Night	8% 8% 30% 45% 8%	840
	11th to 20th	Night	10% 7% 30% 41% 12%	840
	21st to end	Night	11% 10% 35% 37% 8%	714
April	1st to 10th	Night	10% 11% 37% 37% 5%	630
	11th to 20th	Night	17% 10% 29% 39% 5%	623
	21st to end	Night	17% 10% 29% 35% 9%	630
May	1st to 10th	Night	15% 8% 27% 35% 15%	630
	11th to 20th	Night	17% 4 24% 40% 14% 1	621
	21st to end	Night	12% 7% 27% 39% 15% 1	683
June	1st to 10th	Night	9% 3 21% 46% 20% 1	630
	11th to 20th	Night	8% 4 27% 49% 12%	630
	21st to end	Night	7% 3 24% 46% 19%	630
July	1st to 10th	Night	7% 4 14% 48% 26% 1	585
	11th to 20th	Night	5% 2 14% 48% 29% 1	582
	21st to end	Night	5% 2 13% 46% 32% 1	657
August	1st to 10th	Night	8% 3 14% 45% 29% 2	597
	11th to 20th	Night	4 2 17% 49% 27% 1	594
	21st to end	Night	6% 2 15% 53% 23% 1	660
September	1st to 10th	Night	7% 3 18% 47% 23% 2	600
	11th to 20th	Night	8% 4 19% 47% 21% 2	600
	21st to end	Night	7% 3 20% 48% 20% 1	600
October	1st to 10th	Night	13% 4 21% 40% 21% 1	707
	11th to 20th	Night	8% 5% 27% 43% 17%	800
	21st to end	Night	8% 7% 26% 45% 13% 1	1009
November	1st to 10th	Night	7% 5% 26% 48% 13% 1	1025
	11th to 20th	Night	7% 7% 28% 48% 9% 1	1050
	21st to end	Night	9% 5% 26% 46% 13% 1	1050
December	1st to 10th	Night	7% 5% 30% 49% 9%	1050
	11th to 20th	Night	7% 6% 30% 48% 9% 1	1050
	21st to end	Night	10% 6% 28% 46% 9%	1155

Page generated at 2026-06-28 00:10:46. Version ac07

Copyright © 2026 Attilla Danko.