Chequamegon National Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chequamegon National Forest clear sky chart from 2005-11-06 to 2025-07-21.

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	14% 11% 4 9% 5% 5% 5% 3 5% 6% 33%	120517
	Night	12% 12% 4 11% 6% 5% 4 4 5% 6% 32%	118872
Transparency	Day	50% 6% 12% 21% 11% 1	124035
	Night	52% 5% 12% 20% 10% 1	123494
Seeing	Day	20% 17% 34% 20% 8% 2	17061
	Night	19% 14% 34% 24% 8% 1	26945

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	8% 13% 6% 20% 10% 8% 5% 4 4 5% 18%	3617
	11th to 20th	Day	7% 14% 7% 15% 9% 9% 10% 6% 9% 5% 10%	3620
	21st to end	Day	7% 17% 10% 17% 5% 5% 6% 3 4 6% 20%	4097
February	1st to 10th	Day	8% 14% 5% 13% 7% 5% 5% 5% 5% 5% 27%	1800
	11th to 20th	Day	8% 13% 5% 13% 7% 6% 5% 5% 5% 6% 29%	1754
	21st to end	Day	11% 13% 8% 12% 7% 5% 4 4 5% 6% 26%	1640
March	1st to 10th	Day	12% 9% 3 9% 5% 5% 4 3 5% 7% 38%	4480
	11th to 20th	Day	9% 13% 4 11% 6% 4 4 4 6% 8% 31%	4975
	21st to end	Day	21% 14% 4 11% 5% 3 3 3 4 5% 27%	5773
April	1st to 10th	Day	15% 17% 4 10% 5% 4 3 3 5% 5% 28%	2400
	11th to 20th	Day	19% 15% 6% 9% 4 4 4 2 4 6% 29%	2374
	21st to end	Day	20% 13% 3 8% 5% 4 4 3 4 5% 30%	2566
May	1st to 10th	Day	15% 8% 2 5% 3 4 4 3 4 5% 47%	6319
	11th to 20th	Day	14% 9% 2 6% 4 5% 5% 4 5% 7% 38%	6319
	21st to end	Day	16% 10% 3 7% 5% 4 4 3 6% 6% 36%	6935
June	1st to 10th	Day	14% 6% 2 6% 6% 5% 5% 4 6% 8% 38%	2800
	11th to 20th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 7% 35%	2800
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 5% 7% 8% 35%	2800
July	1st to 10th	Day	13% 5% 2 6% 4 6% 5% 5% 7% 9% 40%	4580
	11th to 20th	Day	8% 5% 2 5% 4 4 5% 4 7% 10% 45%	4580
	21st to end	Day	8% 7% 2 6% 4 4 5% 4 7% 8% 46%	4814
August	1st to 10th	Day	14% 7% 2 7% 4 5% 5% 4 6% 8% 37%	4398
	11th to 20th	Day	15% 5% 2 5% 3 4 4 3 5% 8% 46%	4041
	21st to end	Day	15% 8% 3 6% 5% 5% 4 4 5% 7% 38%	4189
September	1st to 10th	Day	14% 7% 2 6% 5% 4 4 3 6% 8% 41%	2280
	11th to 20th	Day	15% 7% 2 6% 4 5% 4 4 6% 8% 40%	2280
	21st to end	Day	20% 9% 2 6% 4 3 3 4 4 6% 38%	2025
October	1st to 10th	Day	18% 11% 3 6% 3 4 5% 3 6% 7% 35%	1900
	11th to 20th	Day	19% 16% 4 10% 4 3 4 3 4 5% 27%	1900
	21st to end	Day	21% 16% 4 6% 4 4 4 3 5% 4 28%	1924
November	1st to 10th	Day	14% 19% 4 8% 5% 3 4 4 4 6% 30%	1737
	11th to 20th	Day	14% 19% 9% 13% 8% 3 4 3 4 4 20%	1600
	21st to end	Day	14% 15% 6% 15% 8% 5% 5% 3 5% 5% 20%	1600
December	1st to 10th	Day	9% 16% 10% 28% 9% 5% 4 2 3 3 11%	2610
	11th to 20th	Day	9% 19% 8% 12% 12% 6% 5% 3 4 4 19%	3008
	21st to end	Day	18% 25% 7% 15% 6% 4 4 2 3 4 13%	3982
January	1st to 10th	Night	8% 11% 6% 20% 10% 7% 6% 3 4 4 21%	6348
	11th to 20th	Night	7% 13% 7% 17% 8% 7% 8% 7% 7% 4 15%	6360
	21st to end	Night	7% 18% 9% 17% 5% 6% 5% 3 5% 5% 21%	6877
February	1st to 10th	Night	8% 14% 5% 13% 8% 7% 5% 4 5% 6% 26%	2600
	11th to 20th	Night	8% 11% 4 10% 7% 7% 7% 5% 5% 5% 29%	2533
	21st to end	Night	11% 14% 5% 10% 6% 6% 5% 3 6% 6% 28%	1989
March	1st to 10th	Night	11% 7% 2 8% 4 4 5% 4 5% 8% 42%	5373
	11th to 20th	Night	11% 11% 5% 15% 6% 5% 5% 5% 6% 6% 27%	5027
	21st to end	Night	20% 15% 5% 10% 5% 4 3 3 4 5% 27%	5155
April	1st to 10th	Night	18% 15% 3 7% 4 4 4 3 6% 5% 30%	2000
	11th to 20th	Night	21% 11% 5% 7% 4 3 4 4 4 6% 33%	1975
	21st to end	Night	20% 11% 3 6% 4 3 3 3 5% 6% 35%	1830
May	1st to 10th	Night	14% 8% 3 6% 4 3 3 3 3 6% 47%	3596
	11th to 20th	Night	12% 7% 3 6% 3 3 3 3 4 7% 47%	3596
	21st to end	Night	13% 9% 3 8% 5% 4 5% 4 5% 6% 40%	3942
June	1st to 10th	Night	12% 6% 2 6% 4 4 4 5% 5% 8% 43%	1600
	11th to 20th	Night	12% 7% 2 7% 6% 5% 5% 4 6% 7% 39%	1600
	21st to end	Night	12% 6% 3 5% 4 5% 5% 4 6% 9% 41%	1600
July	1st to 10th	Night	10% 5% 2 5% 4 4 3 4 6% 8% 49%	2610
	11th to 20th	Night	7% 4 2 5% 3 3 3 3 6% 9% 55%	2610
	21st to end	Night	8% 6% 2 5% 3 3 3 4 6% 7% 53%	2750
August	1st to 10th	Night	12% 6% 2 6% 4 5% 4 4 6% 9% 43%	2539
	11th to 20th	Night	13% 6% 2 4 2 3 3 3 4 8% 51%	2798
	21st to end	Night	17% 9% 2 5% 4 3 3 3 5% 7% 43%	3466
September	1st to 10th	Night	10% 5% 2 5% 4 4 4 3 6% 7% 50%	1900
	11th to 20th	Night	10% 6% 2 4 4 4 5% 4 5% 7% 49%	1900
	21st to end	Night	16% 7% 2 6% 4 4 4 3 5% 7% 41%	2133
October	1st to 10th	Night	16% 9% 2 6% 3 4 3 3 5% 5% 43%	2280
	11th to 20th	Night	16% 14% 4 7% 5% 4 4 4 5% 6% 32%	2280
	21st to end	Night	19% 15% 4 7% 5% 4 4 4 4 5% 29%	2674
November	1st to 10th	Night	14% 15% 4 8% 4 4 3 2 5% 6% 32%	2556
	11th to 20th	Night	14% 16% 6% 12% 5% 5% 4 3 5% 5% 26%	2800
	21st to end	Night	14% 15% 6% 12% 6% 5% 4 4 5% 5% 24%	2800
December	1st to 10th	Night	9% 14% 8% 21% 10% 6% 4 4 4 4 15%	4580
	11th to 20th	Night	10% 18% 7% 16% 7% 5% 6% 5% 5% 4 18%	5199
	21st to end	Night	22% 19% 5% 13% 7% 5% 4 3 4 3 17%	6996

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	68% 4 6% 14% 7%	3618
	11th to 20th	Day	70% 4 6% 12% 7%	3620
	21st to end	Day	66% 4 8% 17% 5%	4097
February	1st to 10th	Day	57% 5% 10% 17% 11% 1	1800
	11th to 20th	Day	54% 8% 9% 21% 8%	1763
	21st to end	Day	58% 5% 10% 16% 9% 1	1640
March	1st to 10th	Day	45% 5% 14% 20% 13% 3	4480
	11th to 20th	Day	49% 5% 14% 19% 11% 1	4975
	21st to end	Day	60% 5% 9% 15% 11%	5775
April	1st to 10th	Day	57% 6% 10% 16% 10% 1	2400
	11th to 20th	Day	57% 4 9% 20% 8% 1	2374
	21st to end	Day	56% 5% 9% 18% 11% 1	2566
May	1st to 10th	Day	39% 6% 11% 25% 17% 2	6357
	11th to 20th	Day	44% 6% 13% 22% 11% 4	6323
	21st to end	Day	46% 6% 9% 21% 17%	6949
June	1st to 10th	Day	40% 9% 14% 26% 11% 1	2800
	11th to 20th	Day	47% 7% 13% 20% 13% 1	2800
	21st to end	Day	43% 8% 17% 23% 9% 1	2800
July	1st to 10th	Day	39% 6% 18% 26% 11% 1	4511
	11th to 20th	Day	31% 7% 17% 32% 12% 1	4505
	21st to end	Day	34% 7% 13% 31% 15%	4663
August	1st to 10th	Day	43% 6% 16% 23% 11% 1	4383
	11th to 20th	Day	36% 6% 17% 30% 10%	4080
	21st to end	Day	44% 5% 16% 23% 10% 1	4188
September	1st to 10th	Day	39% 6% 16% 28% 11%	2280
	11th to 20th	Day	41% 7% 18% 26% 7%	2280
	21st to end	Day	47% 7% 12% 26% 8%	2025
October	1st to 10th	Day	37% 4 14% 29% 15% 1	3160
	11th to 20th	Day	53% 4 8% 23% 11%	3140
	21st to end	Day	52% 5% 16% 20% 6%	3149
November	1st to 10th	Day	55% 6% 11% 19% 8% 1	1737
	11th to 20th	Day	68% 4 9% 12% 5% 1	1600
	21st to end	Day	65% 6% 12% 12% 4 1	1600
December	1st to 10th	Day	79% 4 7% 7% 2	2610
	11th to 20th	Day	69% 4 7% 11% 9%	3005
	21st to end	Day	77% 3 4 11% 5%	3982
January	1st to 10th	Night	66% 4 8% 13% 7%	6348
	11th to 20th	Night	67% 5% 9% 12% 6%	6360
	21st to end	Night	65% 4 9% 16% 6%	6877
February	1st to 10th	Night	57% 5% 9% 17% 11% 1	2600
	11th to 20th	Night	53% 6% 12% 19% 9% 1	2534
	21st to end	Night	55% 6% 11% 18% 8% 2	1989
March	1st to 10th	Night	38% 6% 17% 19% 17% 3	5373
	11th to 20th	Night	54% 5% 13% 19% 8% 1	5027
	21st to end	Night	61% 4 8% 14% 12% 1	5155
April	1st to 10th	Night	54% 6% 8% 17% 13% 1	2000
	11th to 20th	Night	53% 5% 9% 19% 11% 2	1975
	21st to end	Night	49% 5% 10% 23% 13% 1	1830
May	1st to 10th	Night	38% 6% 14% 26% 14% 2	3620
	11th to 20th	Night	37% 6% 11% 24% 17% 4	3597
	21st to end	Night	43% 8% 12% 23% 14% 1	3950
June	1st to 10th	Night	37% 8% 15% 27% 12% 1	1600
	11th to 20th	Night	41% 7% 13% 21% 16% 2	1600
	21st to end	Night	38% 8% 15% 25% 13% 1	1600
July	1st to 10th	Night	33% 6% 20% 27% 12% 2	2570
	11th to 20th	Night	25% 7% 15% 39% 13% 1	2562
	21st to end	Night	29% 6% 13% 30% 21% 1	2662
August	1st to 10th	Night	38% 6% 15% 26% 14% 2	2530
	11th to 20th	Night	33% 5% 16% 35% 10% 1	2825
	21st to end	Night	41% 5% 16% 26% 10% 2	3466
September	1st to 10th	Night	32% 6% 16% 32% 13% 1	1900
	11th to 20th	Night	33% 7% 18% 33% 9%	1900
	21st to end	Night	42% 6% 15% 27% 9% 1	2133
October	1st to 10th	Night	31% 4 9% 33% 21% 2	3800
	11th to 20th	Night	46% 5% 11% 22% 15% 1	3779
	21st to end	Night	56% 5% 11% 20% 8%	4399
November	1st to 10th	Night	52% 6% 12% 21% 9%	2556
	11th to 20th	Night	60% 5% 14% 13% 8% 1	2800
	21st to end	Night	60% 6% 14% 15% 4 1	2800
December	1st to 10th	Night	72% 5% 9% 11% 2	4580
	11th to 20th	Night	69% 5% 8% 13% 5%	5201
	21st to end	Night	73% 4 5% 11% 7%	6996

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% 22% 35% 19% 4 2	300
	11th to 20th	Day	21% 20% 35% 22% 3	300
	21st to end	Day	21% 19% 38% 20% 2	330
February	1st to 10th	Day	19% 28% 37% 12% 3	300
	11th to 20th	Day	16% 32% 36% 11% 4	300
	21st to end	Day	22% 28% 42% 7%	249
March	1st to 10th	Day	19% 23% 41% 13% 4	300
	11th to 20th	Day	21% 22% 39% 13% 4 1	300
	21st to end	Day	23% 21% 34% 16% 4 2	460
April	1st to 10th	Day	27% 20% 35% 13% 5%	500
	11th to 20th	Day	30% 19% 28% 17% 4 1	492
	21st to end	Day	28% 19% 29% 18% 5% 1	593
May	1st to 10th	Day	23% 20% 32% 17% 6% 2	703
	11th to 20th	Day	21% 18% 31% 21% 6% 2	725
	21st to end	Day	23% 15% 34% 19% 8% 1	789
June	1st to 10th	Day	15% 18% 35% 24% 7% 2	730
	11th to 20th	Day	19% 16% 39% 18% 6% 2	730
	21st to end	Day	20% 12% 37% 18% 10% 2	730
July	1st to 10th	Day	10% 9% 35% 26% 15% 5%	721
	11th to 20th	Day	12% 12% 32% 27% 11% 5%	718
	21st to end	Day	9% 10% 37% 23% 15% 5%	740
August	1st to 10th	Day	14% 8% 32% 29% 14% 3	676
	11th to 20th	Day	16% 7% 28% 31% 14% 4	665
	21st to end	Day	18% 12% 28% 25% 14% 3	548
September	1st to 10th	Day	17% 13% 30% 26% 11% 3	490
	11th to 20th	Day	15% 12% 32% 30% 9% 2	490
	21st to end	Day	24% 16% 29% 18% 11% 2	422
October	1st to 10th	Day	26% 19% 28% 18% 9% 1	300
	11th to 20th	Day	28% 25% 34% 11% 3	300
	21st to end	Day	32% 25% 35% 8% 1	330
November	1st to 10th	Day	25% 20% 38% 14% 3	300
	11th to 20th	Day	27% 25% 36% 9% 3	300
	21st to end	Day	24% 23% 39% 12% 2	300
December	1st to 10th	Day	19% 20% 40% 17% 3	300
	11th to 20th	Day	24% 26% 36% 12% 2	300
	21st to end	Day	25% 22% 39% 9% 3 1	330
January	1st to 10th	Night	15% 20% 39% 21% 6%	1000
	11th to 20th	Night	20% 16% 40% 19% 6% 1	1000
	21st to end	Night	20% 15% 40% 21% 4	1100
February	1st to 10th	Night	16% 19% 38% 21% 6%	1000
	11th to 20th	Night	13% 23% 39% 18% 7% 1	979
	21st to end	Night	18% 17% 41% 21% 3	669
March	1st to 10th	Night	19% 17% 38% 21% 5% 1	800
	11th to 20th	Night	17% 20% 36% 20% 6%	621
	21st to end	Night	23% 14% 30% 21% 9% 2	660
April	1st to 10th	Night	25% 16% 33% 21% 5% 1	600
	11th to 20th	Night	28% 11% 30% 23% 8%	593
	21st to end	Night	25% 12% 31% 25% 7% 1	600
May	1st to 10th	Night	21% 13% 33% 26% 6% 1	600
	11th to 20th	Night	20% 10% 34% 27% 7% 2	591
	21st to end	Night	17% 9% 32% 33% 9% 1	650
June	1st to 10th	Night	15% 8% 33% 33% 10%	600
	11th to 20th	Night	16% 9% 33% 33% 9%	600
	21st to end	Night	15% 8% 30% 35% 11% 2	600
July	1st to 10th	Night	8% 5% 30% 36% 20% 1	585
	11th to 20th	Night	12% 5% 33% 31% 18% 1	582
	21st to end	Night	8% 4 28% 40% 18% 2	624
August	1st to 10th	Night	11% 4 25% 42% 17% 1	567
	11th to 20th	Night	14% 5% 24% 34% 21% 2	564
	21st to end	Night	17% 7% 27% 28% 19% 2	627
September	1st to 10th	Night	12% 8% 26% 36% 14% 3	570
	11th to 20th	Night	12% 8% 34% 30% 15% 2	570
	21st to end	Night	20% 13% 30% 25% 11% 1	737
October	1st to 10th	Night	22% 13% 29% 24% 11% 1	760
	11th to 20th	Night	26% 16% 34% 17% 6% 1	760
	21st to end	Night	27% 14% 30% 23% 6%	836
November	1st to 10th	Night	25% 14% 37% 20% 5% 1	800
	11th to 20th	Night	22% 22% 33% 18% 5% 1	1000
	21st to end	Night	22% 22% 34% 19% 4	1000
December	1st to 10th	Night	18% 20% 38% 19% 4	1000
	11th to 20th	Night	21% 19% 34% 20% 5% 1	1000
	21st to end	Night	28% 18% 33% 16% 4 1	1100

Page generated at 2025-07-18 00:10:00. Version ac07

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