Trempealeau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trempealeau clear sky chart from 2005-11-06 to 2026-05-02.

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% 8% 3 8% 5% 4 5% 4 5% 7% 39%	132206
	Night	12% 10% 4 9% 5% 4 4 4 5% 6% 37%	130616
Transparency	Day	44% 6% 13% 24% 12% 1	135732
	Night	46% 5% 12% 23% 13% 1	135165
Seeing	Day	17% 12% 31% 24% 12% 3	17941
	Night	17% 10% 31% 31% 10% 1	27940

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	9% 12% 7% 17% 8% 7% 5% 3 4 5% 23%	4691
	11th to 20th	Day	5% 13% 7% 11% 7% 6% 8% 8% 8% 6% 21%	4710
	21st to end	Day	8% 12% 6% 9% 5% 4 6% 3 5% 6% 36%	5668
February	1st to 10th	Day	9% 13% 5% 10% 6% 6% 4 4 6% 7% 31%	1890
	11th to 20th	Day	11% 10% 5% 8% 6% 5% 4 4 5% 6% 36%	1844
	21st to end	Day	12% 11% 4 8% 6% 4 4 3 5% 8% 34%	1730
March	1st to 10th	Day	14% 7% 2 6% 3 4 4 2 4 6% 49%	4709
	11th to 20th	Day	11% 6% 2 7% 4 4 4 3 6% 8% 44%	5090
	21st to end	Day	23% 11% 3 8% 4 4 4 3 4 5% 30%	5816
April	1st to 10th	Day	19% 12% 3 7% 5% 4 4 3 4 7% 32%	2520
	11th to 20th	Day	20% 10% 3 7% 5% 4 4 4 5% 6% 32%	2494
	21st to end	Day	20% 11% 3 6% 5% 4 5% 3 5% 6% 32%	2586
May	1st to 10th	Day	15% 7% 2 6% 4 4 3 3 5% 6% 45%	6287
	11th to 20th	Day	14% 6% 3 7% 5% 4 4 3 5% 6% 43%	6319
	21st to end	Day	19% 6% 2 7% 4 4 4 4 5% 6% 39%	6935
June	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 6% 7% 47%	2800
	11th to 20th	Day	14% 6% 2 6% 5% 5% 4 4 5% 9% 40%	2800
	21st to end	Day	13% 5% 3 6% 5% 5% 5% 4 6% 9% 40%	2800
July	1st to 10th	Day	9% 4 2 6% 4 4 5% 5% 7% 10% 44%	6360
	11th to 20th	Day	8% 4 1 5% 4 3 4 4 6% 8% 53%	6360
	21st to end	Day	10% 5% 2 7% 5% 5% 5% 4 6% 8% 43%	6924
August	1st to 10th	Day	11% 5% 2 7% 4 4 5% 4 6% 8% 44%	4313
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 5% 8% 46%	4148
	21st to end	Day	8% 5% 2 5% 5% 4 6% 4 6% 9% 45%	4312
September	1st to 10th	Day	13% 6% 2 6% 4 4 4 3 5% 7% 48%	2400
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	2400
	21st to end	Day	14% 7% 2 6% 4 3 4 3 6% 7% 44%	2119
October	1st to 10th	Day	14% 5% 3 6% 5% 2 4 4 5% 6% 46%	2000
	11th to 20th	Day	18% 9% 2 6% 4 4 4 3 6% 6% 38%	2000
	21st to end	Day	17% 13% 3 7% 3 4 3 3 4 5% 37%	2100
November	1st to 10th	Day	14% 9% 2 7% 5% 4 4 3 5% 6% 40%	1852
	11th to 20th	Day	14% 13% 5% 9% 6% 5% 4 3 4 7% 30%	1701
	21st to end	Day	13% 12% 4 8% 5% 5% 3 3 4 6% 37%	1680
December	1st to 10th	Day	8% 10% 4 13% 8% 6% 6% 4 6% 6% 29%	2690
	11th to 20th	Day	12% 17% 5% 10% 7% 5% 5% 4 5% 6% 23%	3088
	21st to end	Day	19% 20% 9% 15% 5% 4 4 3 3 4 14%	4070
January	1st to 10th	Night	10% 13% 6% 14% 7% 4 4 3 4 6% 29%	8232
	11th to 20th	Night	8% 14% 5% 13% 7% 7% 8% 7% 7% 5% 19%	8280
	21st to end	Night	8% 13% 5% 9% 5% 6% 5% 4 6% 6% 32%	8544
February	1st to 10th	Night	8% 14% 6% 11% 6% 5% 4 4 5% 5% 33%	2730
	11th to 20th	Night	9% 10% 3 9% 5% 4 4 4 5% 6% 39%	2663
	21st to end	Night	13% 11% 4 9% 5% 4 4 4 5% 6% 37%	2076
March	1st to 10th	Night	11% 8% 3 7% 4 4 5% 3 5% 5% 45%	5408
	11th to 20th	Night	10% 8% 3 8% 5% 4 5% 4 5% 7% 41%	5090
	21st to end	Night	25% 12% 4 9% 4 3 3 3 3 5% 29%	5354
April	1st to 10th	Night	18% 11% 3 7% 4 4 4 3 5% 6% 36%	2100
	11th to 20th	Night	20% 9% 3 7% 3 4 3 3 5% 5% 37%	2075
	21st to end	Night	19% 8% 3 6% 5% 4 4 4 5% 6% 36%	2031
May	1st to 10th	Night	15% 7% 2 6% 3 4 4 3 4 6% 45%	3651
	11th to 20th	Night	12% 6% 2 5% 3 3 3 4 4 6% 51%	3596
	21st to end	Night	16% 6% 2 7% 4 4 4 4 5% 7% 39%	3942
June	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 47%	1600
	11th to 20th	Night	13% 5% 2 7% 4 4 5% 4 6% 8% 42%	1600
	21st to end	Night	9% 5% 2 6% 4 3 5% 4 6% 7% 49%	1600
July	1st to 10th	Night	10% 4 2 5% 4 4 5% 4 6% 8% 47%	3618
	11th to 20th	Night	8% 4 2 4 3 4 3 3 5% 8% 55%	3617
	21st to end	Night	7% 4 2 7% 4 5% 5% 4 6% 8% 48%	3947
August	1st to 10th	Night	11% 3 2 6% 5% 4 5% 4 5% 8% 48%	2843
	11th to 20th	Night	12% 4 2 4 3 3 3 3 4 8% 53%	2909
	21st to end	Night	11% 5% 3 6% 4 3 4 3 5% 7% 49%	3586
September	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 5% 6% 53%	2000
	11th to 20th	Night	11% 4 2 5% 3 4 4 3 4 7% 52%	2000
	21st to end	Night	12% 5% 2 5% 3 3 4 3 4 5% 53%	2256
October	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 4 6% 51%	2400
	11th to 20th	Night	16% 7% 3 6% 4 4 3 3 5% 7% 42%	2400
	21st to end	Night	17% 9% 4 7% 4 4 4 3 5% 7% 37%	2739
November	1st to 10th	Night	14% 10% 3 6% 4 4 4 3 4 6% 43%	2666
	11th to 20th	Night	13% 12% 5% 9% 5% 4 4 4 4 5% 34%	2914
	21st to end	Night	15% 12% 4 10% 6% 4 3 3 4 6% 35%	2940
December	1st to 10th	Night	8% 8% 4 13% 8% 6% 5% 4 6% 7% 31%	4720
	11th to 20th	Night	12% 19% 6% 12% 5% 5% 5% 4 4 5% 22%	5339
	21st to end	Night	21% 18% 7% 14% 5% 3 4 3 3 4 18%	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	64% 3 12% 14% 6%	4692
	11th to 20th	Day	58% 6% 8% 17% 11%	4710
	21st to end	Day	49% 5% 12% 23% 11%	5668
February	1st to 10th	Day	52% 6% 15% 17% 10% 1	1890
	11th to 20th	Day	48% 5% 12% 25% 8% 1	1853
	21st to end	Day	48% 7% 12% 22% 9% 2	1730
March	1st to 10th	Day	38% 4 14% 26% 15% 3	4709
	11th to 20th	Day	38% 5% 15% 29% 11% 2	5090
	21st to end	Day	57% 6% 11% 15% 11% 1	5818
April	1st to 10th	Day	52% 6% 11% 19% 11% 1	2520
	11th to 20th	Day	52% 6% 11% 18% 11% 2	2494
	21st to end	Day	51% 7% 13% 17% 10% 1	2586
May	1st to 10th	Day	38% 6% 10% 27% 18% 1	6326
	11th to 20th	Day	39% 7% 13% 25% 14% 2	6323
	21st to end	Day	44% 7% 10% 26% 12% 1	6949
June	1st to 10th	Day	34% 9% 14% 28% 14% 2	2800
	11th to 20th	Day	42% 7% 14% 23% 13% 1	2800
	21st to end	Day	41% 8% 15% 22% 12% 2	2800
July	1st to 10th	Day	35% 5% 19% 32% 8% 1	6291
	11th to 20th	Day	29% 5% 16% 32% 17% 1	6285
	21st to end	Day	39% 6% 14% 24% 16% 1	6728
August	1st to 10th	Day	37% 7% 14% 27% 15% 1	4298
	11th to 20th	Day	37% 5% 13% 32% 13%	4187
	21st to end	Day	35% 5% 16% 29% 13% 1	4311
September	1st to 10th	Day	37% 6% 14% 26% 17%	2400
	11th to 20th	Day	36% 8% 16% 30% 10% 1	2400
	21st to end	Day	39% 6% 12% 29% 13%	2119
October	1st to 10th	Day	25% 5% 7% 39% 24%	3260
	11th to 20th	Day	37% 5% 13% 24% 19% 2	3240
	21st to end	Day	43% 3 12% 32% 10% 1	3377
November	1st to 10th	Day	44% 7% 12% 21% 14% 2	1852
	11th to 20th	Day	56% 5% 11% 20% 8% 1	1701
	21st to end	Day	49% 6% 16% 21% 7% 1	1680
December	1st to 10th	Day	54% 6% 16% 16% 7% 1	2690
	11th to 20th	Day	59% 7% 12% 16% 6%	3085
	21st to end	Day	76% 4 7% 10% 3	4070
January	1st to 10th	Night	57% 4 14% 19% 6%	8233
	11th to 20th	Night	63% 5% 9% 12% 10%	8280
	21st to end	Night	50% 5% 12% 20% 12%	8544
February	1st to 10th	Night	53% 5% 12% 21% 9% 1	2730
	11th to 20th	Night	44% 7% 12% 26% 9% 1	2664
	21st to end	Night	48% 5% 13% 21% 11% 2	2076
March	1st to 10th	Night	41% 6% 12% 26% 11% 4	5408
	11th to 20th	Night	41% 5% 14% 25% 13% 2	5090
	21st to end	Night	59% 4 10% 16% 11% 1	5354
April	1st to 10th	Night	49% 5% 9% 20% 14% 1	2100
	11th to 20th	Night	48% 6% 10% 18% 16% 2	2075
	21st to end	Night	47% 7% 11% 19% 13% 2	2031
May	1st to 10th	Night	39% 7% 10% 21% 22% 1	3675
	11th to 20th	Night	33% 6% 13% 23% 19% 6%	3597
	21st to end	Night	44% 7% 10% 26% 13% 1	3950
June	1st to 10th	Night	32% 9% 15% 26% 17% 2	1600
	11th to 20th	Night	38% 7% 13% 22% 18% 2	1600
	21st to end	Night	32% 8% 15% 27% 14% 4	1600
July	1st to 10th	Night	35% 4 17% 30% 13% 1	3580
	11th to 20th	Night	28% 4 15% 37% 14% 1	3572
	21st to end	Night	33% 5% 17% 26% 17% 2	3832
August	1st to 10th	Night	35% 6% 13% 27% 18% 2	2834
	11th to 20th	Night	32% 5% 15% 30% 17% 1	2936
	21st to end	Night	34% 5% 15% 28% 15% 2	3586
September	1st to 10th	Night	32% 7% 11% 30% 20% 1	2000
	11th to 20th	Night	32% 6% 15% 30% 15% 1	2000
	21st to end	Night	33% 5% 12% 29% 20% 1	2256
October	1st to 10th	Night	26% 4 7% 34% 27% 3	3920
	11th to 20th	Night	31% 5% 11% 28% 23% 2	3899
	21st to end	Night	46% 4 10% 25% 15% 1	4412
November	1st to 10th	Night	43% 6% 12% 24% 14% 2	2666
	11th to 20th	Night	52% 7% 12% 18% 10% 1	2914
	21st to end	Night	52% 5% 14% 22% 6% 1	2940
December	1st to 10th	Night	51% 5% 18% 21% 4	4720
	11th to 20th	Night	63% 6% 10% 15% 5%	5341
	21st to end	Night	71% 5% 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	17% 16% 33% 24% 9% 1	330
	11th to 20th	Day	18% 18% 40% 21% 3 1	330
	21st to end	Day	18% 17% 41% 17% 6%	363
February	1st to 10th	Day	15% 24% 41% 15% 5% 1	330
	11th to 20th	Day	18% 24% 33% 19% 5%	330
	21st to end	Day	19% 19% 44% 16% 1	273
March	1st to 10th	Day	20% 19% 37% 17% 6% 1	330
	11th to 20th	Day	24% 17% 36% 15% 6% 2	330
	21st to end	Day	28% 14% 32% 18% 7% 1	467
April	1st to 10th	Day	27% 17% 32% 19% 4	540
	11th to 20th	Day	29% 16% 28% 18% 8% 1	532
	21st to end	Day	25% 16% 32% 19% 7% 1	606
May	1st to 10th	Day	21% 17% 28% 23% 9% 2	709
	11th to 20th	Day	19% 14% 30% 23% 11% 3	725
	21st to end	Day	20% 11% 26% 26% 14% 3	789
June	1st to 10th	Day	10% 9% 31% 30% 17% 3	730
	11th to 20th	Day	16% 8% 32% 30% 11% 2	730
	21st to end	Day	15% 9% 32% 26% 13% 4	730
July	1st to 10th	Day	9% 4 21% 31% 25% 9%	721
	11th to 20th	Day	9% 6% 28% 30% 19% 8%	718
	21st to end	Day	7% 4 27% 37% 19% 7%	794
August	1st to 10th	Day	7% 5% 26% 32% 22% 9%	726
	11th to 20th	Day	13% 7% 20% 29% 24% 7%	705
	21st to end	Day	10% 9% 24% 31% 20% 5%	583
September	1st to 10th	Day	15% 8% 26% 27% 18% 6%	530
	11th to 20th	Day	13% 5% 28% 31% 18% 4	530
	21st to end	Day	18% 13% 25% 23% 17% 4	424
October	1st to 10th	Day	13% 14% 32% 26% 13% 3	330
	11th to 20th	Day	26% 18% 35% 14% 7%	330
	21st to end	Day	25% 16% 33% 18% 6% 1	363
November	1st to 10th	Day	20% 17% 36% 20% 6% 1	330
	11th to 20th	Day	21% 22% 34% 18% 5%	330
	21st to end	Day	23% 15% 40% 17% 5%	330
December	1st to 10th	Day	17% 13% 42% 19% 8% 1	330
	11th to 20th	Day	22% 16% 37% 18% 5% 1	330
	21st to end	Day	29% 15% 41% 12% 3 1	363
January	1st to 10th	Night	14% 15% 35% 29% 7% 1	1050
	11th to 20th	Night	18% 15% 34% 28% 5%	1050
	21st to end	Night	18% 12% 35% 28% 6%	1155
February	1st to 10th	Night	15% 15% 37% 27% 6%	1050
	11th to 20th	Night	15% 14% 40% 23% 7%	1029
	21st to end	Night	19% 13% 37% 26% 4	692
March	1st to 10th	Night	17% 14% 36% 26% 7%	807
	11th to 20th	Night	20% 13% 33% 28% 6%	630
	21st to end	Night	22% 10% 30% 29% 8% 1	693
April	1st to 10th	Night	21% 14% 36% 25% 4	630
	11th to 20th	Night	24% 10% 30% 29% 6%	623
	21st to end	Night	22% 9% 33% 27% 8%	630
May	1st to 10th	Night	21% 9% 33% 30% 7% 1	603
	11th to 20th	Night	16% 9% 31% 31% 11% 1	591
	21st to end	Night	16% 6% 27% 37% 13% 1	650
June	1st to 10th	Night	11% 7% 29% 43% 11%	600
	11th to 20th	Night	15% 6% 29% 41% 9%	600
	21st to end	Night	11% 5% 26% 43% 15% 1	600
July	1st to 10th	Night	6% 3 21% 37% 31% 2	585
	11th to 20th	Night	8% 4 24% 38% 24% 2	582
	21st to end	Night	6% 2 16% 53% 20% 3	657
August	1st to 10th	Night	7% 2 16% 49% 25% 2	597
	11th to 20th	Night	13% 3 17% 36% 28% 3	594
	21st to end	Night	11% 4 19% 39% 24% 2	660
September	1st to 10th	Night	12% 5% 24% 36% 19% 5%	600
	11th to 20th	Night	11% 4 26% 36% 21% 3	600
	21st to end	Night	15% 8% 25% 34% 18% 1	753
October	1st to 10th	Night	15% 8% 31% 29% 16% 1	800
	11th to 20th	Night	19% 13% 32% 29% 7%	800
	21st to end	Night	21% 11% 29% 31% 7%	880
November	1st to 10th	Night	18% 12% 34% 28% 7% 1	820
	11th to 20th	Night	19% 14% 38% 23% 6%	1024
	21st to end	Night	20% 15% 34% 24% 6%	1050
December	1st to 10th	Night	18% 12% 37% 26% 7% 1	1050
	11th to 20th	Night	22% 14% 35% 23% 5%	1050
	21st to end	Night	27% 12% 32% 25% 4	1155

Page generated at 2026-04-29 01:21:41. Version ac07

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