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 2025-02-25.

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% 55%	112558
	Night	6% 6% 2 6% 4 4 4 4 6% 7% 53%	114937
Transparency	Day	26% 5% 10% 26% 23% 9%	112299
	Night	29% 6% 11% 25% 22% 7%	114786
Seeing	Day	8% 6% 21% 33% 24% 8%	16002
	Night	9% 5% 26% 45% 14% 1	26163

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 10% 3 8% 4 4 4 2 4 6% 53%	3638
	11th to 20th	Day	2 6% 2 7% 6% 5% 5% 4 6% 7% 50%	3640
	21st to end	Day	3 6% 2 5% 3 3 3 4 5% 7% 59%	4400
February	1st to 10th	Day	3 9% 4 7% 6% 4 4 3 6% 8% 47%	1823
	11th to 20th	Day	2 7% 3 8% 4 4 4 4 5% 7% 51%	1949
	21st to end	Day	3 7% 3 7% 5% 4 3 4 5% 7% 53%	1610
March	1st to 10th	Day	5% 9% 3 5% 4 4 4 3 5% 7% 53%	3130
	11th to 20th	Day	8% 5% 2 6% 4 3 4 3 4 5% 56%	3321
	21st to end	Day	6% 7% 2 6% 4 5% 5% 4 7% 9% 45%	4133
April	1st to 10th	Day	7% 7% 2 5% 4 4 3 4 6% 7% 53%	2280
	11th to 20th	Day	10% 8% 3 6% 4 4 4 3 6% 7% 45%	2251
	21st to end	Day	9% 6% 2 5% 4 4 4 5% 7% 8% 45%	2289
May	1st to 10th	Day	9% 7% 3 7% 5% 5% 5% 4 6% 7% 43%	4120
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 7% 10% 48%	4295
	21st to end	Day	7% 4 2 4 4 4 4 4 6% 9% 52%	4825
June	1st to 10th	Day	5% 3 2 3 3 4 5% 4 7% 9% 55%	2660
	11th to 20th	Day	6% 3 1 4 4 4 5% 4 7% 8% 53%	2660
	21st to end	Day	4 3 1 4 3 4 4 4 8% 9% 56%	2660
July	1st to 10th	Day	6% 4 1 4 3 3 4 3 6% 8% 58%	4430
	11th to 20th	Day	2 2 1 4 4 4 5% 5% 8% 11% 54%	4430
	21st to end	Day	2 2 1 4 3 4 5% 5% 7% 9% 58%	4802
August	1st to 10th	Day	9% 2 1 4 3 4 5% 5% 7% 11% 48%	4120
	11th to 20th	Day	3 3 2 5% 4 4 4 4 6% 8% 57%	3726
	21st to end	Day	4 3 1 4 3 3 4 4 6% 10% 58%	4180
September	1st to 10th	Day	4 3 1 3 2 3 3 3 4 8% 65%	2280
	11th to 20th	Day	6% 2 1 3 3 3 4 3 5% 6% 63%	2215
	21st to end	Day	8% 3 1 3 2 3 3 2 3 6% 65%	2090
October	1st to 10th	Day	6% 3 1 2 2 1 2 1 3 4 76%	3304
	11th to 20th	Day	4 5% 2 5% 3 2 3 3 5% 6% 64%	3150
	21st to end	Day	7% 5% 2 4 2 3 3 3 5% 7% 60%	3196
November	1st to 10th	Day	3 5% 1 5% 3 3 4 4 5% 7% 60%	1763
	11th to 20th	Day	4 6% 2 5% 3 4 3 2 5% 8% 59%	1800
	21st to end	Day	4 7% 3 5% 3 3 3 3 4 6% 60%	1738
December	1st to 10th	Day	2 4 2 5% 3 3 4 3 4 6% 63%	2620
	11th to 20th	Day	3 6% 2 4 3 4 3 3 4 6% 62%	3026
	21st to end	Day	6% 8% 3 5% 4 5% 4 3 5% 8% 49%	4004
January	1st to 10th	Night	4 10% 3 8% 4 4 4 4 6% 7% 46%	6327
	11th to 20th	Night	2 7% 2 8% 5% 4 5% 4 7% 7% 50%	6340
	21st to end	Night	2 6% 2 7% 5% 4 4 4 4 5% 56%	6609
February	1st to 10th	Night	4 9% 4 8% 4 4 4 4 5% 7% 48%	2575
	11th to 20th	Night	4 9% 3 7% 5% 4 4 4 6% 7% 46%	2338
	21st to end	Night	3 8% 3 7% 3 4 3 3 5% 6% 55%	1938
March	1st to 10th	Night	4 10% 3 6% 4 3 4 3 5% 6% 53%	3734
	11th to 20th	Night	10% 8% 2 5% 3 4 3 3 4 5% 52%	3650
	21st to end	Night	7% 7% 2 5% 5% 4 6% 5% 7% 7% 45%	3509
April	1st to 10th	Night	8% 8% 2 6% 4 4 4 4 5% 6% 51%	1900
	11th to 20th	Night	14% 8% 3 6% 5% 3 4 3 4 6% 44%	1877
	21st to end	Night	14% 7% 2 7% 4 4 4 3 6% 7% 42%	1891
May	1st to 10th	Night	10% 6% 3 6% 6% 5% 6% 4 7% 9% 38%	2850
	11th to 20th	Night	10% 5% 2 5% 5% 5% 4 4 7% 10% 45%	2593
	21st to end	Night	10% 5% 2 6% 4 5% 5% 4 6% 8% 44%	2762
June	1st to 10th	Night	6% 3 1 4 4 3 4 4 8% 11% 52%	1520
	11th to 20th	Night	7% 3 1 4 5% 4 5% 4 6% 7% 55%	1520
	21st to end	Night	6% 4 1 5% 4 5% 4 4 6% 8% 53%	1520
July	1st to 10th	Night	5% 4 1 4 5% 4 5% 4 6% 7% 56%	2540
	11th to 20th	Night	3 3 1 4 4 5% 5% 4 7% 12% 53%	2540
	21st to end	Night	4 3 1 5% 4 5% 5% 5% 7% 9% 53%	2761
August	1st to 10th	Night	11% 4 2 7% 5% 5% 7% 5% 8% 9% 38%	2802
	11th to 20th	Night	3 5% 2 6% 4 6% 5% 4 7% 10% 47%	3113
	21st to end	Night	3 3 1 5% 4 5% 6% 5% 9% 10% 49%	3487
September	1st to 10th	Night	6% 4 2 5% 3 3 5% 3 5% 9% 56%	1900
	11th to 20th	Night	5% 4 1 5% 3 3 3 3 6% 8% 59%	1964
	21st to end	Night	7% 2 1 4 3 3 3 3 4 6% 64%	2090
October	1st to 10th	Night	6% 3 1 3 2 2 2 2 4 5% 71%	3659
	11th to 20th	Night	8% 3 2 4 3 3 3 3 5% 6% 60%	3778
	21st to end	Night	6% 5% 2 5% 2 3 3 2 4 6% 61%	4330
November	1st to 10th	Night	4 4 2 4 3 4 3 4 5% 7% 59%	2535
	11th to 20th	Night	4 6% 2 4 3 3 4 4 5% 7% 59%	2600
	21st to end	Night	5% 7% 2 5% 4 3 3 3 5% 7% 56%	2660
December	1st to 10th	Night	2 5% 1 5% 2 3 3 2 4 5% 67%	4570
	11th to 20th	Night	2 5% 2 5% 4 3 4 3 6% 7% 58%	5181
	21st to end	Night	6% 10% 3 7% 4 4 4 4 5% 7% 46%	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	33% 4 9% 32% 18% 5%	3639
	11th to 20th	Day	32% 4 13% 23% 24% 5%	3640
	21st to end	Day	24% 4 11% 28% 26% 7%	4400
February	1st to 10th	Day	35% 5% 11% 26% 18% 5%	1823
	11th to 20th	Day	33% 4 9% 28% 22% 4	1959
	21st to end	Day	29% 5% 8% 27% 23% 8%	1610
March	1st to 10th	Day	30% 5% 8% 20% 29% 8%	3130
	11th to 20th	Day	28% 6% 14% 31% 17% 3	3321
	21st to end	Day	31% 8% 14% 32% 12% 3	4133
April	1st to 10th	Day	30% 5% 13% 24% 20% 8%	2280
	11th to 20th	Day	37% 6% 12% 22% 16% 7%	2254
	21st to end	Day	33% 7% 10% 27% 20% 2	2289
May	1st to 10th	Day	36% 7% 9% 26% 17% 5%	4120
	11th to 20th	Day	30% 7% 12% 29% 17% 4	4299
	21st to end	Day	26% 7% 14% 25% 23% 4	4825
June	1st to 10th	Day	23% 7% 18% 26% 18% 8%	2660
	11th to 20th	Day	26% 6% 11% 21% 24% 13%	2660
	21st to end	Day	20% 6% 11% 25% 26% 12%	2660
July	1st to 10th	Day	24% 5% 8% 17% 31% 15%	4361
	11th to 20th	Day	20% 6% 11% 25% 23% 14%	4355
	21st to end	Day	20% 7% 11% 22% 19% 22%	4651
August	1st to 10th	Day	28% 6% 15% 27% 16% 8%	4105
	11th to 20th	Day	24% 6% 12% 20% 25% 13%	3762
	21st to end	Day	22% 5% 10% 21% 26% 16%	4179
September	1st to 10th	Day	19% 4 7% 23% 27% 19%	2280
	11th to 20th	Day	21% 5% 8% 21% 29% 17%	2215
	21st to end	Day	22% 4 6% 23% 34% 12%	2090
October	1st to 10th	Day	15% 2 5% 18% 33% 27%	3304
	11th to 20th	Day	22% 3 9% 30% 27% 9%	3150
	21st to end	Day	25% 3 6% 28% 30% 9%	3196
November	1st to 10th	Day	23% 4 11% 26% 25% 10%	1763
	11th to 20th	Day	24% 4 7% 29% 29% 7%	1800
	21st to end	Day	25% 3 9% 25% 29% 9%	1738
December	1st to 10th	Day	22% 3 8% 34% 26% 6%	2620
	11th to 20th	Day	24% 4 7% 35% 25% 5%	3024
	21st to end	Day	34% 4 10% 30% 18% 6%	4004
January	1st to 10th	Night	35% 5% 12% 26% 19% 4	6327
	11th to 20th	Night	31% 6% 11% 21% 27% 5%	6340
	21st to end	Night	29% 5% 10% 26% 24% 7%	6609
February	1st to 10th	Night	34% 6% 12% 25% 19% 4	2575
	11th to 20th	Night	35% 5% 12% 26% 18% 4	2338
	21st to end	Night	30% 4 8% 25% 24% 9%	1938
March	1st to 10th	Night	30% 6% 7% 20% 29% 8%	3734
	11th to 20th	Night	33% 6% 13% 23% 21% 4	3650
	21st to end	Night	34% 8% 15% 30% 11% 2	3509
April	1st to 10th	Night	33% 7% 9% 25% 19% 7%	1900
	11th to 20th	Night	39% 5% 12% 22% 16% 6%	1877
	21st to end	Night	40% 6% 10% 24% 17% 3	1891
May	1st to 10th	Night	37% 10% 13% 23% 11% 5%	2850
	11th to 20th	Night	34% 7% 21% 25% 10% 4	2594
	21st to end	Night	35% 9% 19% 19% 13% 5%	2762
June	1st to 10th	Night	25% 7% 25% 26% 13% 5%	1520
	11th to 20th	Night	26% 9% 13% 23% 18% 11%	1520
	21st to end	Night	28% 6% 11% 27% 23% 5%	1520
July	1st to 10th	Night	27% 6% 13% 20% 29% 5%	2500
	11th to 20th	Night	23% 7% 17% 21% 25% 7%	2492
	21st to end	Night	25% 7% 15% 21% 19% 12%	2674
August	1st to 10th	Night	39% 9% 17% 19% 11% 4	2794
	11th to 20th	Night	32% 8% 15% 21% 15% 9%	3143
	21st to end	Night	25% 7% 16% 22% 22% 9%	3487
September	1st to 10th	Night	24% 5% 9% 22% 24% 15%	1900
	11th to 20th	Night	23% 5% 10% 26% 23% 14%	1964
	21st to end	Night	21% 4 8% 24% 29% 13%	2090
October	1st to 10th	Night	17% 3 6% 18% 31% 24%	3659
	11th to 20th	Night	24% 5% 8% 28% 27% 8%	3778
	21st to end	Night	26% 3 8% 27% 26% 11%	4330
November	1st to 10th	Night	24% 4 10% 26% 25% 11%	2535
	11th to 20th	Night	24% 4 9% 27% 26% 9%	2600
	21st to end	Night	28% 3 8% 25% 28% 7%	2660
December	1st to 10th	Night	21% 3 9% 35% 28% 5%	4570
	11th to 20th	Night	24% 4 5% 38% 26% 3	5182
	21st to end	Night	37% 4 8% 27% 22% 3	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	8% 5% 19% 43% 21% 5%	300
	11th to 20th	Day	10% 7% 22% 42% 19% 2	300
	21st to end	Day	5% 7% 26% 45% 13% 4	330
February	1st to 10th	Day	8% 8% 31% 42% 9% 2	300
	11th to 20th	Day	4 8% 27% 45% 15% 1	300
	21st to end	Day	5% 10% 26% 47% 9% 2	237
March	1st to 10th	Day	8% 9% 22% 39% 18% 5%	270
	11th to 20th	Day	10% 10% 24% 33% 18% 4	356
	21st to end	Day	11% 13% 30% 31% 13% 2	506
April	1st to 10th	Day	14% 13% 26% 30% 13% 4	460
	11th to 20th	Day	17% 15% 27% 24% 14% 2	452
	21st to end	Day	13% 14% 26% 25% 18% 4	469
May	1st to 10th	Day	16% 9% 24% 30% 17% 4	653
	11th to 20th	Day	16% 5% 20% 29% 24% 6%	675
	21st to end	Day	11% 8% 22% 28% 22% 9%	734
June	1st to 10th	Day	6% 4 19% 29% 31% 12%	680
	11th to 20th	Day	6% 5% 28% 32% 24% 5%	680
	21st to end	Day	5% 3 19% 36% 28% 9%	680
July	1st to 10th	Day	8% 2 14% 28% 36% 11%	671
	11th to 20th	Day	4 2 14% 28% 40% 12%	668
	21st to end	Day	5% 2 11% 28% 40% 14%	739
August	1st to 10th	Day	6% 2 13% 29% 37% 13%	551
	11th to 20th	Day	3 2 20% 31% 29% 16%	477
	21st to end	Day	4 1 18% 32% 30% 15%	539
September	1st to 10th	Day	5% 3 16% 30% 31% 16%	490
	11th to 20th	Day	6% 3 16% 26% 31% 18%	425
	21st to end	Day	9% 2 16% 29% 26% 18%	300
October	1st to 10th	Day	10% 4 15% 23% 29% 18%	300
	11th to 20th	Day	5% 5% 23% 36% 22% 9%	300
	21st to end	Day	10% 8% 25% 32% 20% 7%	330
November	1st to 10th	Day	6% 6% 22% 39% 19% 9%	300
	11th to 20th	Day	6% 6% 22% 43% 19% 4	300
	21st to end	Day	10% 6% 14% 44% 19% 6%	300
December	1st to 10th	Day	7% 7% 22% 39% 22% 3	300
	11th to 20th	Day	7% 5% 28% 46% 13%	300
	21st to end	Day	9% 8% 22% 45% 14% 2	330
January	1st to 10th	Night	7% 6% 27% 47% 12% 1	1000
	11th to 20th	Night	6% 7% 34% 42% 11% 1	1000
	21st to end	Night	8% 4 31% 46% 10% 1	943
February	1st to 10th	Night	8% 5% 38% 41% 7% 1	800
	11th to 20th	Night	7% 5% 35% 44% 8%	784
	21st to end	Night	8% 6% 38% 44% 4	646
March	1st to 10th	Night	7% 8% 30% 45% 9%	760
	11th to 20th	Night	11% 6% 28% 42% 13%	760
	21st to end	Night	11% 9% 35% 38% 7%	646
April	1st to 10th	Night	11% 11% 38% 35% 5%	570
	11th to 20th	Night	17% 11% 29% 37% 6%	563
	21st to end	Night	17% 9% 28% 36% 9%	570
May	1st to 10th	Night	15% 8% 28% 35% 14%	570
	11th to 20th	Night	18% 4 21% 41% 15% 1	561
	21st to end	Night	11% 6% 27% 40% 16% 1	617
June	1st to 10th	Night	8% 4 21% 46% 21% 1	570
	11th to 20th	Night	8% 4 26% 49% 12%	570
	21st to end	Night	7% 3 22% 47% 21% 1	570
July	1st to 10th	Night	7% 3 14% 47% 26% 1	555
	11th to 20th	Night	5% 2 14% 49% 29% 1	552
	21st to end	Night	5% 2 13% 46% 33% 1	624
August	1st to 10th	Night	8% 3 13% 45% 30% 2	567
	11th to 20th	Night	5% 2 17% 49% 26% 1	564
	21st to end	Night	6% 2 15% 53% 23% 1	627
September	1st to 10th	Night	7% 3 18% 47% 23% 2	570
	11th to 20th	Night	8% 3 19% 46% 21% 2	570
	21st to end	Night	7% 3 21% 48% 20% 1	570
October	1st to 10th	Night	13% 4 21% 39% 21% 1	671
	11th to 20th	Night	8% 5% 26% 43% 18%	760
	21st to end	Night	9% 6% 26% 45% 13% 1	958
November	1st to 10th	Night	8% 4 26% 48% 14% 1	975
	11th to 20th	Night	8% 7% 27% 48% 9% 1	1000
	21st to end	Night	9% 5% 26% 46% 14% 1	1000
December	1st to 10th	Night	7% 5% 30% 49% 9%	1000
	11th to 20th	Night	7% 6% 29% 48% 9% 1	1000
	21st to end	Night	10% 6% 27% 46% 10%	1100

Page generated at 2025-02-22 04:51:34. Version ac07

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