La Crosse
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the La Crosse clear sky chart from 2005-11-06 to 2026-10-29.

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	12% 9% 3 8% 5% 4 5% 4 6% 7% 38%	150407
	Night	12% 10% 4 9% 5% 4 4 4 5% 6% 37%	142066
Transparency	Day	44% 5% 12% 25% 12% 1	153919
	Night	46% 5% 12% 23% 13% 1	146630
Seeing	Day	18% 12% 31% 24% 12% 3	18724
	Night	18% 10% 30% 30% 11% 1	28502

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% 7% 18% 7% 7% 5% 3 5% 5% 22%	4691
	11th to 20th	Day	6% 13% 6% 12% 7% 4 8% 10% 8% 5% 21%	4710
	21st to end	Day	9% 12% 7% 10% 5% 4 6% 3 6% 7% 32%	5650
February	1st to 10th	Day	8% 14% 5% 11% 6% 4 5% 5% 5% 6% 31%	1890
	11th to 20th	Day	11% 11% 4 8% 6% 5% 5% 4 5% 6% 35%	1860
	21st to end	Day	11% 12% 3 10% 7% 5% 4 3 5% 7% 33%	1730
March	1st to 10th	Day	14% 8% 3 5% 4 3 3 3 4 6% 49%	4669
	11th to 20th	Day	11% 8% 2 7% 4 3 5% 3 5% 8% 44%	5090
	21st to end	Day	23% 12% 4 8% 4 4 4 3 4 5% 30%	5851
April	1st to 10th	Day	18% 14% 4 7% 5% 5% 3 3 4 6% 32%	2520
	11th to 20th	Day	19% 13% 4 7% 4 4 4 3 5% 5% 31%	2494
	21st to end	Day	20% 11% 3 7% 5% 4 4 4 6% 6% 31%	2562
May	1st to 10th	Day	12% 7% 2 6% 4 4 5% 4 6% 7% 43%	8184
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 7% 43%	8222
	21st to end	Day	16% 7% 2 7% 4 4 4 4 5% 7% 38%	9047
June	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 7% 9% 44%	2940
	11th to 20th	Day	13% 7% 2 6% 4 4 4 5% 6% 9% 40%	2940
	21st to end	Day	13% 6% 3 6% 5% 5% 5% 4 6% 9% 38%	2940
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 9% 38%	8280
	11th to 20th	Day	6% 4 2 4 3 4 4 4 7% 9% 53%	8280
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 6% 8% 44%	8990
August	1st to 10th	Day	11% 7% 3 7% 4 5% 5% 4 6% 7% 42%	6155
	11th to 20th	Day	14% 7% 2 6% 4 4 5% 3 6% 8% 40%	5883
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 7% 10% 47%	6080
September	1st to 10th	Day	14% 5% 2 5% 4 3 4 4 6% 8% 45%	2520
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 8% 44%	2520
	21st to end	Day	13% 8% 3 7% 4 4 4 3 5% 7% 42%	2232
October	1st to 10th	Day	14% 7% 2 6% 4 3 4 3 5% 5% 48%	2100
	11th to 20th	Day	18% 10% 3 6% 4 3 4 3 5% 8% 38%	2100
	21st to end	Day	17% 11% 3 8% 5% 4 3 3 4 6% 37%	2171
November	1st to 10th	Day	13% 9% 3 8% 4 3 4 3 5% 6% 40%	1852
	11th to 20th	Day	13% 14% 4 10% 6% 4 3 3 5% 6% 31%	1726
	21st to end	Day	13% 12% 4 9% 5% 4 4 3 4 6% 37%	1680
December	1st to 10th	Day	8% 11% 5% 13% 8% 6% 4 4 6% 6% 29%	2690
	11th to 20th	Day	14% 17% 5% 11% 8% 5% 5% 4 6% 6% 21%	3088
	21st to end	Day	18% 21% 9% 17% 5% 4 3 3 3 3 13%	4070
January	1st to 10th	Night	10% 13% 6% 14% 8% 5% 4 3 4 5% 28%	8232
	11th to 20th	Night	8% 15% 6% 15% 7% 6% 8% 7% 6% 4 18%	8280
	21st to end	Night	8% 14% 6% 10% 6% 6% 5% 4 6% 6% 29%	8549
February	1st to 10th	Night	8% 14% 6% 11% 7% 5% 5% 4 5% 5% 32%	2730
	11th to 20th	Night	9% 10% 4 9% 5% 6% 5% 4 4 6% 39%	2646
	21st to end	Night	12% 12% 4 10% 6% 5% 4 3 4 6% 35%	2076
March	1st to 10th	Night	12% 8% 4 7% 4 4 4 3 4 5% 44%	5446
	11th to 20th	Night	10% 9% 3 8% 4 4 4 4 5% 7% 42%	5090
	21st to end	Night	23% 14% 4 9% 4 3 3 3 4 5% 28%	5319
April	1st to 10th	Night	18% 11% 3 7% 4 4 4 3 5% 5% 36%	2100
	11th to 20th	Night	19% 10% 3 7% 3 3 3 3 5% 6% 36%	2075
	21st to end	Night	19% 10% 2 6% 5% 4 4 4 5% 6% 35%	2054
May	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 6% 7% 45%	4697
	11th to 20th	Night	14% 6% 2 5% 4 4 4 4 5% 6% 46%	4670
	21st to end	Night	16% 8% 3 8% 5% 4 4 4 5% 7% 37%	5139
June	1st to 10th	Night	11% 4 2 5% 4 4 4 4 7% 8% 45%	1680
	11th to 20th	Night	10% 7% 3 6% 5% 4 3 3 6% 10% 42%	1680
	21st to end	Night	11% 4 2 5% 4 3 4 3 6% 8% 49%	1680
July	1st to 10th	Night	11% 7% 2 6% 4 4 5% 4 6% 9% 42%	4708
	11th to 20th	Night	6% 4 2 4 3 3 3 3 6% 9% 57%	4707
	21st to end	Night	6% 5% 2 6% 4 4 5% 4 6% 9% 49%	5117
August	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 7% 49%	4011
	11th to 20th	Night	13% 6% 2 6% 3 4 4 3 5% 8% 48%	4180
	21st to end	Night	8% 6% 2 5% 3 4 5% 4 6% 8% 49%	5046
September	1st to 10th	Night	10% 5% 2 6% 3 4 4 3 5% 7% 51%	2100
	11th to 20th	Night	13% 4 2 5% 3 4 3 3 5% 7% 51%	2100
	21st to end	Night	12% 5% 2 5% 3 3 3 3 5% 6% 53%	2362
October	1st to 10th	Night	13% 6% 2 5% 3 4 3 3 4 6% 52%	2520
	11th to 20th	Night	16% 8% 2 6% 4 4 4 3 4 7% 42%	2520
	21st to end	Night	17% 10% 3 7% 4 4 4 3 5% 6% 37%	2844
November	1st to 10th	Night	14% 10% 3 7% 4 4 4 3 5% 5% 42%	2666
	11th to 20th	Night	12% 13% 6% 9% 6% 5% 4 3 5% 4 33%	2893
	21st to end	Night	14% 14% 4 10% 4 4 3 3 3 6% 35%	2940
December	1st to 10th	Night	7% 9% 4 12% 8% 7% 5% 3 6% 7% 31%	4720
	11th to 20th	Night	13% 18% 7% 14% 5% 5% 5% 4 4 4 21%	5339
	21st to end	Night	19% 19% 8% 15% 5% 4 4 3 3 4 17%	7150

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	65% 4 12% 14% 6%	4692
	11th to 20th	Day	59% 5% 9% 17% 10%	4710
	21st to end	Day	52% 3 12% 23% 10%	5650
February	1st to 10th	Day	53% 5% 14% 17% 10% 1	1890
	11th to 20th	Day	50% 5% 11% 25% 8% 1	1869
	21st to end	Day	51% 5% 11% 22% 9% 2	1730
March	1st to 10th	Day	38% 3 13% 28% 14% 3	4669
	11th to 20th	Day	39% 3 15% 29% 12% 2	5090
	21st to end	Day	58% 4 10% 15% 11% 1	5853
April	1st to 10th	Day	54% 4 11% 20% 11% 1	2520
	11th to 20th	Day	54% 5% 9% 20% 11% 2	2494
	21st to end	Day	52% 6% 12% 18% 11% 1	2562
May	1st to 10th	Day	38% 4 8% 29% 19% 2	8222
	11th to 20th	Day	41% 6% 8% 27% 16% 1	8226
	21st to end	Day	45% 5% 9% 26% 13% 3	9061
June	1st to 10th	Day	36% 7% 13% 28% 14% 2	2940
	11th to 20th	Day	40% 7% 13% 24% 14% 1	2940
	21st to end	Day	42% 7% 14% 23% 12% 2	2940
July	1st to 10th	Day	39% 7% 17% 29% 7% 1	8211
	11th to 20th	Day	26% 6% 13% 35% 19% 1	8205
	21st to end	Day	37% 7% 11% 28% 17% 1	8794
August	1st to 10th	Day	40% 6% 12% 30% 12% 1	6140
	11th to 20th	Day	40% 7% 14% 30% 9%	5922
	21st to end	Day	31% 6% 17% 33% 12% 1	6079
September	1st to 10th	Day	36% 6% 15% 26% 17% 1	2520
	11th to 20th	Day	38% 7% 15% 30% 11% 1	2520
	21st to end	Day	41% 6% 10% 30% 13% 1	2232
October	1st to 10th	Day	25% 4 6% 41% 23% 1	3360
	11th to 20th	Day	38% 4 11% 25% 19% 2	3340
	21st to end	Day	43% 3 12% 30% 11% 1	3435
November	1st to 10th	Day	44% 5% 13% 21% 14% 1	1852
	11th to 20th	Day	55% 4 12% 20% 9% 1	1726
	21st to end	Day	49% 5% 16% 22% 7% 1	1680
December	1st to 10th	Day	54% 6% 16% 16% 7% 1	2690
	11th to 20th	Day	63% 5% 12% 15% 5%	3085
	21st to end	Day	77% 4 6% 11% 3	4070
January	1st to 10th	Night	58% 4 14% 18% 5%	8233
	11th to 20th	Night	66% 3 9% 11% 10%	8280
	21st to end	Night	54% 3 13% 19% 11%	8549
February	1st to 10th	Night	55% 3 12% 19% 9% 1	2730
	11th to 20th	Night	47% 5% 12% 25% 10% 1	2647
	21st to end	Night	51% 4 12% 21% 11% 1	2076
March	1st to 10th	Night	43% 4 12% 26% 11% 4	5446
	11th to 20th	Night	40% 5% 11% 28% 13% 2	5090
	21st to end	Night	59% 4 10% 16% 10% 1	5319
April	1st to 10th	Night	50% 5% 9% 20% 15% 2	2100
	11th to 20th	Night	48% 5% 9% 19% 17% 2	2075
	21st to end	Night	49% 5% 11% 20% 13% 2	2054
May	1st to 10th	Night	37% 5% 9% 24% 23% 1	4721
	11th to 20th	Night	39% 5% 10% 22% 20% 4	4671
	21st to end	Night	46% 5% 9% 24% 14% 2	5149
June	1st to 10th	Night	34% 7% 13% 27% 16% 2	1680
	11th to 20th	Night	38% 6% 10% 24% 19% 2	1680
	21st to end	Night	33% 6% 15% 27% 15% 4	1680
July	1st to 10th	Night	38% 7% 16% 28% 11% 1	4670
	11th to 20th	Night	24% 5% 13% 38% 19% 1	4662
	21st to end	Night	31% 7% 15% 28% 18% 2	5002
August	1st to 10th	Night	35% 5% 12% 29% 17% 1	4002
	11th to 20th	Night	35% 6% 17% 28% 13% 1	4207
	21st to end	Night	32% 7% 15% 30% 14% 2	5046
September	1st to 10th	Night	33% 6% 11% 29% 21% 1	2100
	11th to 20th	Night	33% 6% 14% 31% 15% 1	2100
	21st to end	Night	33% 5% 10% 31% 19% 1	2362
October	1st to 10th	Night	26% 3 6% 36% 27% 3	4040
	11th to 20th	Night	33% 4 10% 28% 23% 2	4019
	21st to end	Night	47% 4 8% 26% 14% 1	4530
November	1st to 10th	Night	45% 4 12% 24% 14% 2	2666
	11th to 20th	Night	55% 4 12% 18% 9% 1	2893
	21st to end	Night	53% 3 13% 23% 6% 1	2940
December	1st to 10th	Night	52% 5% 18% 20% 4	4720
	11th to 20th	Night	67% 4 10% 14% 5%	5341
	21st to end	Night	72% 4 8% 12% 4	7150

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	19% 16% 33% 20% 8% 3	330
	11th to 20th	Day	20% 21% 39% 16% 3 1	330
	21st to end	Day	21% 19% 37% 18% 4	363
February	1st to 10th	Day	16% 22% 41% 15% 4 2	330
	11th to 20th	Day	20% 21% 38% 18% 4	330
	21st to end	Day	19% 19% 45% 16% 1	273
March	1st to 10th	Day	22% 19% 39% 15% 5% 1	330
	11th to 20th	Day	26% 14% 39% 14% 5% 2	330
	21st to end	Day	29% 16% 31% 16% 8% 1	476
April	1st to 10th	Day	28% 16% 35% 15% 5%	540
	11th to 20th	Day	31% 16% 28% 16% 9% 1	532
	21st to end	Day	25% 17% 31% 18% 8% 1	582
May	1st to 10th	Day	22% 16% 29% 24% 7% 2	753
	11th to 20th	Day	20% 15% 30% 21% 11% 3	775
	21st to end	Day	21% 11% 27% 24% 14% 4	844
June	1st to 10th	Day	14% 8% 28% 30% 17% 4	780
	11th to 20th	Day	16% 9% 35% 26% 11% 2	780
	21st to end	Day	15% 11% 32% 26% 13% 4	780
July	1st to 10th	Day	10% 4 21% 31% 25% 9%	771
	11th to 20th	Day	8% 7% 27% 32% 18% 8%	768
	21st to end	Day	8% 5% 28% 35% 18% 6%	849
August	1st to 10th	Day	8% 5% 24% 33% 22% 8%	776
	11th to 20th	Day	16% 5% 21% 29% 22% 7%	739
	21st to end	Day	10% 7% 26% 28% 21% 6%	627
September	1st to 10th	Day	16% 8% 24% 32% 14% 6%	570
	11th to 20th	Day	13% 7% 30% 30% 16% 5%	570
	21st to end	Day	18% 15% 25% 24% 15% 3	476
October	1st to 10th	Day	17% 13% 31% 27% 10% 3	360
	11th to 20th	Day	26% 17% 35% 14% 8% 1	360
	21st to end	Day	26% 16% 35% 16% 6% 1	387
November	1st to 10th	Day	21% 16% 37% 20% 5% 1	330
	11th to 20th	Day	22% 20% 36% 17% 4 1	330
	21st to end	Day	23% 19% 39% 14% 5%	330
December	1st to 10th	Day	16% 17% 42% 18% 7%	330
	11th to 20th	Day	22% 18% 35% 18% 6% 1	330
	21st to end	Day	29% 13% 40% 14% 3 1	363
January	1st to 10th	Night	16% 15% 36% 25% 8% 1	1050
	11th to 20th	Night	19% 15% 35% 26% 5% 1	1050
	21st to end	Night	19% 12% 35% 28% 6% 1	1155
February	1st to 10th	Night	15% 15% 36% 28% 6%	1050
	11th to 20th	Night	16% 15% 38% 25% 6% 1	1012
	21st to end	Night	20% 13% 37% 25% 5%	692
March	1st to 10th	Night	20% 12% 35% 27% 5% 1	819
	11th to 20th	Night	20% 12% 32% 28% 7%	630
	21st to end	Night	24% 10% 28% 28% 9% 1	693
April	1st to 10th	Night	24% 12% 37% 22% 5%	630
	11th to 20th	Night	26% 10% 30% 26% 7%	623
	21st to end	Night	24% 9% 30% 28% 8% 1	630
May	1st to 10th	Night	21% 9% 31% 32% 7% 1	630
	11th to 20th	Night	17% 9% 30% 34% 10% 1	621
	21st to end	Night	16% 5% 29% 35% 13% 1	683
June	1st to 10th	Night	13% 5% 28% 41% 13%	630
	11th to 20th	Night	13% 7% 31% 37% 10% 1	630
	21st to end	Night	12% 5% 26% 42% 15% 1	630
July	1st to 10th	Night	9% 2 18% 39% 31% 3	615
	11th to 20th	Night	8% 4 19% 41% 25% 2	612
	21st to end	Night	5% 3 17% 50% 22% 3	690
August	1st to 10th	Night	7% 2 16% 47% 27% 2	627
	11th to 20th	Night	13% 3 13% 39% 28% 4	624
	21st to end	Night	10% 3 21% 40% 24% 2	693
September	1st to 10th	Night	14% 5% 21% 39% 18% 4	630
	11th to 20th	Night	13% 4 25% 33% 20% 4	630
	21st to end	Night	15% 8% 24% 36% 15% 2	802
October	1st to 10th	Night	17% 9% 29% 30% 15% 1	840
	11th to 20th	Night	21% 12% 32% 27% 7%	840
	21st to end	Night	23% 11% 29% 29% 7%	913
November	1st to 10th	Night	20% 12% 34% 26% 7% 1	820
	11th to 20th	Night	19% 17% 35% 23% 6%	1003
	21st to end	Night	23% 16% 30% 25% 6%	1050
December	1st to 10th	Night	19% 13% 37% 24% 6% 1	1050
	11th to 20th	Night	21% 15% 34% 23% 6%	1050
	21st to end	Night	27% 13% 31% 23% 5%	1155

Page generated at 2026-10-26 03:37:51. Version ac07

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