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 2024-11-03.

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	13% 9% 3 8% 5% 4 4 4 6% 7% 37%	101575
	Night	13% 10% 4 8% 4 4 4 3 5% 6% 38%	97517
Transparency	Day	45% 6% 12% 24% 12% 1	101368
	Night	46% 5% 12% 23% 13% 1	97395
Seeing	Day	18% 12% 31% 24% 12% 4	15955
	Night	18% 10% 30% 30% 11% 1	25798

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% 15% 10% 17% 6% 5% 5% 3 5% 4 22%	2527
	11th to 20th	Day	9% 13% 4 14% 8% 5% 8% 8% 6% 6% 18%	2530
	21st to end	Day	15% 19% 8% 12% 5% 4 3 2 5% 5% 21%	3043
February	1st to 10th	Day	8% 13% 5% 11% 6% 4 5% 5% 5% 7% 31%	1710
	11th to 20th	Day	12% 11% 4 8% 6% 5% 5% 4 5% 6% 34%	1678
	21st to end	Day	12% 12% 3 11% 6% 5% 4 3 5% 7% 33%	1570
March	1st to 10th	Day	14% 9% 3 5% 4 3 3 2 4 5% 48%	3179
	11th to 20th	Day	10% 8% 3 9% 4 4 5% 3 5% 7% 43%	3480
	21st to end	Day	22% 14% 3 10% 4 4 4 3 4 5% 26%	3993
April	1st to 10th	Day	18% 13% 4 7% 5% 5% 3 3 4 6% 32%	2280
	11th to 20th	Day	19% 13% 4 7% 4 4 3 3 5% 5% 33%	2254
	21st to end	Day	20% 11% 3 7% 4 4 4 3 6% 6% 31%	2318
May	1st to 10th	Day	18% 8% 2 7% 4 4 4 4 5% 7% 36%	4385
	11th to 20th	Day	14% 6% 2 7% 4 4 4 3 5% 8% 41%	4399
	21st to end	Day	17% 7% 2 7% 4 4 4 4 5% 6% 37%	4824
June	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 7% 8% 45%	2660
	11th to 20th	Day	12% 6% 2 6% 4 4 4 5% 6% 9% 41%	2660
	21st to end	Day	13% 6% 3 5% 5% 5% 5% 4 6% 9% 38%	2660
July	1st to 10th	Day	11% 6% 2 6% 5% 6% 6% 5% 7% 9% 38%	4440
	11th to 20th	Day	5% 3 2 5% 3 4 5% 4 7% 9% 53%	4440
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 8% 42%	4813
August	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	4200
	11th to 20th	Day	14% 6% 2 5% 4 3 4 3 6% 8% 45%	3991
	21st to end	Day	8% 5% 2 6% 5% 4 5% 4 7% 9% 44%	4180
September	1st to 10th	Day	15% 5% 2 5% 3 3 4 4 5% 7% 46%	2280
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 3 5% 7% 47%	2280
	21st to end	Day	13% 8% 3 6% 4 4 4 3 5% 7% 43%	2019
October	1st to 10th	Day	15% 8% 2 6% 4 3 4 3 5% 5% 45%	1900
	11th to 20th	Day	18% 10% 3 6% 3 3 4 3 5% 8% 37%	1900
	21st to end	Day	18% 11% 3 8% 5% 3 3 3 3 6% 37%	1989
November	1st to 10th	Day	12% 9% 3 8% 4 3 4 3 6% 6% 41%	1690
	11th to 20th	Day	14% 15% 4 10% 6% 4 4 3 5% 6% 30%	1562
	21st to end	Day	12% 11% 4 8% 5% 4 4 3 4 6% 39%	1520
December	1st to 10th	Day	13% 14% 5% 12% 6% 4 4 4 5% 6% 28%	1520
	11th to 20th	Day	13% 14% 5% 9% 6% 5% 6% 3 6% 6% 26%	1918
	21st to end	Day	18% 20% 8% 15% 6% 4 3 2 3 4 16%	2783
January	1st to 10th	Night	10% 15% 9% 14% 5% 5% 4 3 4 5% 26%	4428
	11th to 20th	Night	9% 14% 6% 15% 7% 5% 6% 6% 7% 4 20%	4440
	21st to end	Night	14% 20% 7% 11% 5% 4 4 3 4 4 23%	4623
February	1st to 10th	Night	8% 15% 6% 10% 7% 5% 4 4 4 5% 32%	2470
	11th to 20th	Night	9% 10% 4 9% 6% 6% 5% 3 4 6% 39%	2388
	21st to end	Night	13% 12% 4 10% 6% 5% 4 3 4 5% 35%	1884
March	1st to 10th	Night	12% 9% 3 7% 4 4 4 3 5% 6% 43%	3701
	11th to 20th	Night	10% 9% 3 8% 5% 4 5% 4 5% 6% 41%	3480
	21st to end	Night	24% 13% 4 10% 4 3 3 3 4 5% 29%	3637
April	1st to 10th	Night	18% 11% 3 8% 4 3 4 3 5% 5% 37%	1900
	11th to 20th	Night	19% 11% 3 7% 3 3 3 4 5% 6% 36%	1875
	21st to end	Night	19% 10% 2 6% 5% 4 4 3 5% 6% 34%	1858
May	1st to 10th	Night	16% 8% 2 7% 4 4 5% 4 5% 7% 38%	2518
	11th to 20th	Night	11% 6% 2 5% 4 4 4 4 5% 7% 48%	2506
	21st to end	Night	13% 6% 2 6% 4 4 4 4 6% 8% 43%	2743
June	1st to 10th	Night	11% 4 2 5% 4 5% 4 4 7% 8% 46%	1520
	11th to 20th	Night	10% 7% 3 6% 5% 4 3 3 6% 10% 44%	1520
	21st to end	Night	10% 4 2 5% 4 3 4 3 6% 8% 50%	1520
July	1st to 10th	Night	12% 7% 2 6% 3 4 4 4 5% 8% 45%	2530
	11th to 20th	Night	5% 3 2 5% 3 3 4 3 6% 10% 57%	2530
	21st to end	Night	5% 5% 2 6% 4 4 5% 4 6% 9% 50%	2750
August	1st to 10th	Night	11% 4 2 5% 4 4 5% 4 5% 7% 48%	2736
	11th to 20th	Night	11% 5% 2 5% 2 3 3 3 5% 6% 53%	2846
	21st to end	Night	10% 7% 2 5% 3 4 5% 3 5% 7% 49%	3476
September	1st to 10th	Night	10% 5% 2 6% 3 4 4 3 4 7% 52%	1900
	11th to 20th	Night	12% 4 2 5% 3 3 3 3 5% 7% 53%	1900
	21st to end	Night	12% 5% 2 5% 3 3 3 3 5% 6% 54%	2137
October	1st to 10th	Night	14% 6% 2 5% 3 4 3 3 4 6% 51%	2280
	11th to 20th	Night	16% 8% 2 7% 4 4 4 3 5% 7% 41%	2280
	21st to end	Night	17% 10% 3 7% 4 4 4 3 5% 6% 36%	2608
November	1st to 10th	Night	13% 9% 3 7% 4 4 4 3 5% 5% 43%	2433
	11th to 20th	Night	12% 13% 6% 10% 7% 5% 4 3 5% 4 32%	2617
	21st to end	Night	14% 13% 3 9% 4 4 3 3 4 6% 36%	2660
December	1st to 10th	Night	12% 12% 6% 12% 6% 5% 5% 3 5% 6% 28%	2660
	11th to 20th	Night	13% 15% 5% 13% 6% 5% 4 3 4 6% 27%	3279
	21st to end	Night	19% 18% 7% 13% 6% 3 4 3 3 4 20%	4884

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% 5% 12% 12% 5%	2528
	11th to 20th	Day	61% 6% 10% 17% 6%	2530
	21st to end	Day	66% 4 13% 13% 4	3043
February	1st to 10th	Day	52% 5% 14% 17% 10% 1	1710
	11th to 20th	Day	51% 5% 12% 24% 8% 1	1687
	21st to end	Day	52% 5% 10% 21% 10% 2	1570
March	1st to 10th	Day	41% 4 11% 25% 18% 2	3179
	11th to 20th	Day	40% 4 12% 31% 11% 2	3480
	21st to end	Day	60% 5% 10% 16% 8% 1	3993
April	1st to 10th	Day	54% 4 11% 20% 10% 1	2280
	11th to 20th	Day	53% 5% 9% 20% 11% 2	2254
	21st to end	Day	52% 6% 12% 18% 11% 1	2318
May	1st to 10th	Day	45% 6% 10% 24% 14% 1	4426
	11th to 20th	Day	40% 7% 10% 31% 11% 1	4403
	21st to end	Day	46% 6% 9% 23% 14% 2	4837
June	1st to 10th	Day	35% 7% 14% 28% 14% 2	2660
	11th to 20th	Day	39% 8% 13% 24% 15% 1	2660
	21st to end	Day	41% 8% 13% 23% 12% 2	2660
July	1st to 10th	Day	41% 8% 17% 25% 8% 1	4371
	11th to 20th	Day	26% 7% 15% 33% 18% 1	4365
	21st to end	Day	36% 8% 13% 24% 18% 1	4662
August	1st to 10th	Day	37% 6% 13% 28% 14% 1	4185
	11th to 20th	Day	36% 6% 12% 33% 13%	4030
	21st to end	Day	34% 6% 15% 31% 13% 1	4179
September	1st to 10th	Day	37% 6% 14% 25% 18% 1	2280
	11th to 20th	Day	37% 7% 13% 31% 12% 1	2280
	21st to end	Day	39% 6% 11% 30% 13% 1	2019
October	1st to 10th	Day	39% 6% 9% 32% 13%	1900
	11th to 20th	Day	45% 5% 13% 23% 12% 1	1900
	21st to end	Day	50% 4 12% 22% 11% 1	1989
November	1st to 10th	Day	43% 6% 14% 21% 15% 2	1690
	11th to 20th	Day	56% 5% 12% 18% 8% 1	1562
	21st to end	Day	47% 5% 17% 22% 8% 1	1520
December	1st to 10th	Day	56% 6% 14% 16% 7% 1	1520
	11th to 20th	Day	57% 6% 16% 15% 6% 1	1915
	21st to end	Day	73% 5% 7% 12% 3	2783
January	1st to 10th	Night	60% 5% 11% 19% 5%	4428
	11th to 20th	Night	62% 5% 11% 15% 7%	4440
	21st to end	Night	64% 4 11% 16% 5%	4623
February	1st to 10th	Night	55% 3 11% 19% 10% 1	2470
	11th to 20th	Night	47% 5% 12% 24% 10% 1	2389
	21st to end	Night	51% 4 11% 21% 11% 1	1884
March	1st to 10th	Night	41% 5% 11% 29% 11% 2	3701
	11th to 20th	Night	40% 7% 9% 28% 15% 2	3480
	21st to end	Night	59% 4 8% 20% 8% 1	3637
April	1st to 10th	Night	49% 6% 9% 20% 14% 2	1900
	11th to 20th	Night	48% 5% 9% 19% 17% 3	1875
	21st to end	Night	49% 5% 11% 19% 14% 2	1858
May	1st to 10th	Night	44% 7% 13% 17% 18% 1	2542
	11th to 20th	Night	35% 6% 10% 27% 18% 4	2507
	21st to end	Night	38% 7% 11% 25% 18% 1	2751
June	1st to 10th	Night	33% 7% 13% 27% 17% 2	1520
	11th to 20th	Night	37% 6% 10% 25% 20% 2	1520
	21st to end	Night	31% 7% 15% 27% 15% 4	1520
July	1st to 10th	Night	37% 6% 17% 25% 13% 2	2490
	11th to 20th	Night	24% 5% 15% 37% 18% 1	2482
	21st to end	Night	29% 8% 16% 24% 20% 2	2662
August	1st to 10th	Night	35% 6% 11% 29% 18% 2	2727
	11th to 20th	Night	32% 5% 13% 31% 17% 1	2873
	21st to end	Night	34% 6% 14% 28% 16% 3	3476
September	1st to 10th	Night	32% 6% 10% 29% 23% 1	1900
	11th to 20th	Night	32% 5% 13% 32% 17% 1	1900
	21st to end	Night	32% 6% 11% 32% 19% 1	2137
October	1st to 10th	Night	35% 5% 9% 31% 18% 2	2280
	11th to 20th	Night	43% 5% 12% 22% 16% 1	2280
	21st to end	Night	49% 5% 10% 23% 12% 1	2608
November	1st to 10th	Night	44% 4 12% 23% 15% 2	2433
	11th to 20th	Night	56% 4 12% 17% 9% 1	2617
	21st to end	Night	51% 4 14% 24% 7% 1	2660
December	1st to 10th	Night	56% 5% 13% 19% 6%	2660
	11th to 20th	Night	59% 6% 11% 18% 6%	3281
	21st to end	Night	68% 5% 10% 13% 4	4884

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	20% 17% 31% 21% 9% 3	270
	11th to 20th	Day	21% 21% 36% 17% 3 1	270
	21st to end	Day	22% 18% 37% 19% 4	297
February	1st to 10th	Day	15% 23% 42% 15% 3 2	270
	11th to 20th	Day	20% 24% 34% 18% 4	270
	21st to end	Day	19% 19% 44% 17% 1	225
March	1st to 10th	Day	21% 19% 39% 14% 6% 1	270
	11th to 20th	Day	24% 14% 39% 15% 6% 2	270
	21st to end	Day	29% 14% 30% 17% 9% 1	399
April	1st to 10th	Day	28% 15% 36% 16% 5%	460
	11th to 20th	Day	30% 15% 29% 17% 9% 1	452
	21st to end	Day	25% 17% 30% 19% 8% 2	498
May	1st to 10th	Day	24% 15% 30% 23% 7% 2	653
	11th to 20th	Day	19% 15% 31% 21% 11% 3	675
	21st to end	Day	21% 11% 26% 24% 14% 4	734
June	1st to 10th	Day	13% 7% 28% 31% 17% 4	680
	11th to 20th	Day	15% 8% 35% 28% 12% 3	680
	21st to end	Day	14% 10% 31% 27% 14% 4	680
July	1st to 10th	Day	10% 4 21% 30% 25% 10%	671
	11th to 20th	Day	8% 7% 28% 31% 19% 7%	668
	21st to end	Day	8% 4 28% 34% 19% 7%	739
August	1st to 10th	Day	8% 5% 23% 33% 23% 8%	676
	11th to 20th	Day	15% 5% 21% 28% 24% 8%	641
	21st to end	Day	11% 6% 26% 28% 22% 7%	539
September	1st to 10th	Day	17% 7% 23% 32% 14% 6%	490
	11th to 20th	Day	11% 7% 30% 31% 16% 5%	490
	21st to end	Day	17% 16% 27% 23% 14% 2	405
October	1st to 10th	Day	18% 13% 29% 27% 10% 3	300
	11th to 20th	Day	26% 17% 34% 15% 7%	300
	21st to end	Day	28% 18% 34% 14% 5% 1	330
November	1st to 10th	Day	18% 14% 38% 23% 6% 1	276
	11th to 20th	Day	22% 19% 38% 17% 3 1	270
	21st to end	Day	22% 18% 39% 16% 6%	270
December	1st to 10th	Day	16% 15% 42% 18% 8%	270
	11th to 20th	Day	22% 18% 33% 20% 6% 1	270
	21st to end	Day	29% 12% 42% 14% 2	297
January	1st to 10th	Night	16% 15% 37% 25% 8% 1	950
	11th to 20th	Night	19% 14% 35% 27% 5% 1	950
	21st to end	Night	20% 12% 34% 27% 6% 1	1045
February	1st to 10th	Night	15% 14% 35% 29% 6% 1	950
	11th to 20th	Night	16% 15% 37% 25% 7% 1	914
	21st to end	Night	21% 13% 36% 25% 6%	628
March	1st to 10th	Night	20% 12% 35% 27% 6% 1	741
	11th to 20th	Night	19% 12% 31% 30% 7% 1	570
	21st to end	Night	25% 10% 26% 29% 10% 1	627
April	1st to 10th	Night	23% 12% 37% 23% 5%	570
	11th to 20th	Night	25% 10% 31% 26% 7%	563
	21st to end	Night	24% 9% 31% 28% 8% 1	570
May	1st to 10th	Night	22% 9% 32% 30% 6% 1	570
	11th to 20th	Night	17% 8% 30% 35% 10% 1	561
	21st to end	Night	16% 5% 28% 36% 14% 1	617
June	1st to 10th	Night	13% 5% 28% 41% 13%	570
	11th to 20th	Night	13% 7% 30% 39% 11% 1	570
	21st to end	Night	11% 4 26% 42% 16% 1	570
July	1st to 10th	Night	8% 1 18% 39% 30% 3	555
	11th to 20th	Night	7% 5% 20% 41% 24% 3	552
	21st to end	Night	5% 2 17% 49% 24% 3	624
August	1st to 10th	Night	7% 2 16% 47% 27% 2	567
	11th to 20th	Night	13% 3 14% 38% 28% 4	564
	21st to end	Night	11% 3 21% 40% 23% 2	627
September	1st to 10th	Night	14% 4 21% 39% 18% 5%	570
	11th to 20th	Night	12% 5% 26% 33% 21% 4	570
	21st to end	Night	15% 9% 26% 34% 15% 2	726
October	1st to 10th	Night	18% 9% 28% 28% 16% 1	760
	11th to 20th	Night	21% 13% 31% 28% 8%	760
	21st to end	Night	23% 11% 29% 29% 7%	836
November	1st to 10th	Night	18% 12% 35% 26% 8% 1	749
	11th to 20th	Night	18% 18% 36% 22% 6%	907
	21st to end	Night	22% 16% 31% 25% 7%	950
December	1st to 10th	Night	19% 13% 37% 24% 6% 1	950
	11th to 20th	Night	21% 14% 35% 23% 6%	950
	21st to end	Night	27% 13% 32% 23% 5%	1045

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