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 2025-01-07.

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 5% 7% 38%	105221
	Night	13% 10% 4 8% 5% 4 4 4 5% 6% 38%	103955
Transparency	Day	44% 7% 13% 23% 12% 1	108791
	Night	45% 6% 12% 23% 12% 1	108525
Seeing	Day	17% 13% 31% 24% 12% 3	16164
	Night	17% 10% 31% 31% 10% 1	26127

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% 15% 9% 17% 6% 5% 4 3 4 5% 24%	2575
	11th to 20th	Day	7% 14% 4 12% 8% 7% 8% 8% 7% 6% 20%	2530
	21st to end	Day	14% 18% 8% 11% 5% 4 4 3 4 6% 23%	3047
February	1st to 10th	Day	8% 13% 4 10% 6% 6% 4 4 6% 7% 32%	1710
	11th to 20th	Day	11% 10% 5% 8% 6% 5% 4 4 5% 6% 35%	1664
	21st to end	Day	13% 11% 4 8% 6% 4 4 3 5% 8% 33%	1570
March	1st to 10th	Day	14% 8% 3 6% 4 4 3 2 4 5% 48%	3205
	11th to 20th	Day	10% 7% 3 8% 5% 4 4 4 5% 8% 43%	3480
	21st to end	Day	23% 13% 3 9% 4 4 4 3 5% 5% 26%	3972
April	1st to 10th	Day	19% 12% 3 7% 5% 4 4 3 4 7% 32%	2280
	11th to 20th	Day	21% 9% 4 6% 4 4 4 4 4 6% 33%	2254
	21st to end	Day	20% 11% 3 6% 5% 4 5% 3 5% 6% 32%	2340
May	1st to 10th	Day	18% 7% 2 6% 4 5% 4 4 6% 6% 38%	4367
	11th to 20th	Day	14% 6% 2 6% 5% 5% 4 4 6% 7% 42%	4399
	21st to end	Day	17% 8% 2 7% 4 4 4 4 5% 6% 38%	4824
June	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 6% 7% 47%	2660
	11th to 20th	Day	13% 6% 2 6% 5% 4 4 4 6% 9% 41%	2660
	21st to end	Day	13% 5% 2 6% 5% 5% 5% 4 6% 9% 40%	2660
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 6% 5% 8% 9% 39%	4440
	11th to 20th	Day	5% 3 1 5% 4 4 4 4 7% 9% 55%	4440
	21st to end	Day	9% 4 2 7% 5% 5% 6% 4 7% 9% 43%	4813
August	1st to 10th	Day	11% 5% 2 6% 4 4 5% 5% 6% 8% 44%	4181
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 5% 8% 46%	4019
	21st to end	Day	9% 4 2 5% 5% 4 6% 4 6% 9% 45%	4180
September	1st to 10th	Day	14% 6% 2 5% 4 3 4 3 5% 7% 49%	2280
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 5% 7% 46%	2280
	21st to end	Day	14% 7% 2 6% 4 3 4 3 6% 7% 43%	2014
October	1st to 10th	Day	15% 6% 3 6% 5% 3 4 4 5% 6% 45%	1900
	11th to 20th	Day	18% 9% 2 6% 4 4 4 3 6% 7% 38%	1900
	21st to end	Day	18% 13% 3 7% 3 4 3 3 4 5% 37%	1995
November	1st to 10th	Day	14% 10% 2 7% 5% 4 4 3 5% 6% 40%	1762
	11th to 20th	Day	14% 13% 5% 10% 6% 5% 4 3 4 7% 30%	1620
	21st to end	Day	13% 11% 4 7% 5% 5% 3 3 5% 6% 38%	1600
December	1st to 10th	Day	8% 9% 5% 13% 8% 6% 7% 4 6% 7% 30%	2610
	11th to 20th	Day	12% 17% 5% 10% 7% 5% 5% 4 5% 6% 23%	3008
	21st to end	Day	19% 20% 9% 15% 5% 5% 4 3 3 4 14%	3982
January	1st to 10th	Night	10% 14% 9% 14% 5% 4 4 3 4 5% 28%	4513
	11th to 20th	Night	10% 12% 5% 13% 7% 6% 6% 7% 7% 5% 21%	4440
	21st to end	Night	14% 19% 7% 10% 4 4 4 3 4 5% 24%	4618
February	1st to 10th	Night	7% 14% 5% 12% 6% 5% 4 4 4 5% 33%	2470
	11th to 20th	Night	9% 10% 3 8% 6% 5% 5% 4 5% 6% 39%	2403
	21st to end	Night	14% 12% 3 9% 5% 4 4 4 5% 6% 36%	1884
March	1st to 10th	Night	10% 9% 3 6% 4 4 5% 3 6% 6% 44%	3678
	11th to 20th	Night	11% 7% 3 8% 5% 5% 5% 4 5% 6% 41%	3480
	21st to end	Night	25% 11% 4 9% 4 3 3 3 3 5% 29%	3658
April	1st to 10th	Night	18% 11% 3 7% 4 4 4 3 5% 6% 36%	1900
	11th to 20th	Night	20% 9% 3 7% 3 4 3 3 5% 5% 37%	1875
	21st to end	Night	19% 8% 3 6% 5% 4 4 4 6% 6% 36%	1838
May	1st to 10th	Night	16% 8% 2 7% 4 4 5% 4 5% 7% 39%	2538
	11th to 20th	Night	13% 5% 3 5% 3 3 4 4 5% 6% 50%	2506
	21st to end	Night	13% 6% 2 7% 4 4 4 4 6% 8% 43%	2743
June	1st to 10th	Night	10% 5% 3 5% 4 4 4 4 6% 8% 47%	1520
	11th to 20th	Night	13% 5% 2 6% 5% 3 4 3 7% 8% 44%	1520
	21st to end	Night	8% 5% 2 6% 4 3 5% 4 6% 7% 49%	1520
July	1st to 10th	Night	11% 4 2 6% 4 4 5% 4 5% 8% 47%	2530
	11th to 20th	Night	5% 3 1 4 3 4 4 4 6% 8% 58%	2530
	21st to end	Night	7% 4 1 6% 4 5% 4 4 6% 8% 51%	2750
August	1st to 10th	Night	11% 4 2 6% 5% 4 4 4 5% 7% 48%	2756
	11th to 20th	Night	12% 4 2 4 3 2 3 3 5% 8% 53%	2818
	21st to end	Night	11% 5% 3 6% 4 3 4 3 5% 7% 49%	3476
September	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 5% 6% 53%	1900
	11th to 20th	Night	11% 4 2 5% 3 4 4 3 4 7% 54%	1900
	21st to end	Night	12% 6% 2 5% 3 4 4 3 4 5% 53%	2143
October	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 4 6% 51%	2280
	11th to 20th	Night	16% 7% 3 5% 4 4 3 4 5% 7% 42%	2280
	21st to end	Night	17% 9% 4 7% 4 4 4 3 5% 7% 36%	2602
November	1st to 10th	Night	14% 10% 3 6% 4 4 4 3 4 6% 43%	2536
	11th to 20th	Night	13% 12% 6% 9% 5% 4 4 4 4 6% 33%	2775
	21st to end	Night	15% 12% 4 9% 6% 4 3 3 4 6% 35%	2800
December	1st to 10th	Night	8% 8% 4 12% 8% 6% 5% 4 6% 7% 32%	4580
	11th to 20th	Night	12% 20% 6% 12% 5% 5% 5% 4 4 5% 22%	5199
	21st to end	Night	21% 18% 7% 14% 5% 3 4 3 3 3 18%	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	64% 5% 13% 14% 5%	2576
	11th to 20th	Day	59% 9% 11% 16% 6%	2530
	21st to end	Day	62% 6% 14% 13% 4	3047
February	1st to 10th	Day	51% 6% 15% 17% 11% 1	1710
	11th to 20th	Day	49% 6% 12% 24% 8% 1	1673
	21st to end	Day	49% 8% 11% 21% 10% 2	1570
March	1st to 10th	Day	40% 5% 12% 24% 18% 2	3205
	11th to 20th	Day	39% 6% 12% 31% 11% 1	3480
	21st to end	Day	58% 8% 11% 15% 8% 1	3972
April	1st to 10th	Day	52% 6% 11% 19% 10% 1	2280
	11th to 20th	Day	52% 7% 10% 19% 11% 2	2254
	21st to end	Day	52% 8% 13% 16% 10% 1	2340
May	1st to 10th	Day	43% 8% 12% 23% 14% 1	4408
	11th to 20th	Day	37% 10% 13% 28% 11% 1	4403
	21st to end	Day	44% 9% 10% 22% 14% 2	4837
June	1st to 10th	Day	34% 9% 15% 27% 14% 2	2660
	11th to 20th	Day	40% 8% 14% 23% 14% 1	2660
	21st to end	Day	40% 9% 15% 23% 11% 2	2660
July	1st to 10th	Day	40% 7% 20% 24% 8% 1	4371
	11th to 20th	Day	25% 6% 17% 32% 19% 1	4365
	21st to end	Day	37% 7% 15% 23% 17% 1	4662
August	1st to 10th	Day	36% 7% 14% 27% 15% 1	4166
	11th to 20th	Day	37% 5% 13% 33% 13%	4058
	21st to end	Day	35% 5% 16% 29% 13% 1	4179
September	1st to 10th	Day	36% 6% 14% 26% 17%	2280
	11th to 20th	Day	35% 9% 15% 30% 10% 1	2280
	21st to end	Day	39% 7% 12% 29% 13%	2014
October	1st to 10th	Day	25% 5% 7% 39% 24%	3160
	11th to 20th	Day	37% 5% 13% 25% 19% 1	3140
	21st to end	Day	42% 3 12% 32% 10% 1	3272
November	1st to 10th	Day	44% 7% 13% 20% 14% 2	1762
	11th to 20th	Day	56% 5% 11% 19% 8% 1	1620
	21st to end	Day	48% 7% 17% 21% 7% 1	1600
December	1st to 10th	Day	54% 6% 16% 16% 7% 1	2610
	11th to 20th	Day	59% 7% 12% 16% 6%	3005
	21st to end	Day	76% 4 7% 10% 3	3982
January	1st to 10th	Night	58% 6% 11% 19% 5%	4513
	11th to 20th	Night	60% 7% 12% 14% 7%	4440
	21st to end	Night	61% 7% 10% 17% 5%	4618
February	1st to 10th	Night	53% 5% 11% 21% 9% 1	2470
	11th to 20th	Night	44% 8% 13% 24% 9% 1	2404
	21st to end	Night	48% 6% 12% 21% 11% 2	1884
March	1st to 10th	Night	39% 7% 12% 30% 10% 2	3678
	11th to 20th	Night	41% 7% 10% 26% 14% 2	3480
	21st to end	Night	58% 5% 8% 19% 8% 1	3658
April	1st to 10th	Night	49% 6% 9% 20% 14% 2	1900
	11th to 20th	Night	48% 6% 10% 18% 16% 3	1875
	21st to end	Night	46% 8% 12% 19% 13% 2	1838
May	1st to 10th	Night	43% 9% 12% 16% 19% 1	2562
	11th to 20th	Night	33% 8% 12% 25% 18% 4	2507
	21st to end	Night	37% 9% 11% 25% 17% 1	2751
June	1st to 10th	Night	32% 9% 15% 25% 17% 2	1520
	11th to 20th	Night	37% 7% 13% 22% 19% 2	1520
	21st to end	Night	31% 8% 15% 27% 14% 4	1520
July	1st to 10th	Night	36% 5% 19% 26% 12% 2	2490
	11th to 20th	Night	24% 5% 16% 37% 17% 2	2482
	21st to end	Night	29% 7% 17% 25% 20% 2	2662
August	1st to 10th	Night	35% 6% 13% 27% 18% 2	2747
	11th to 20th	Night	31% 6% 15% 30% 17% 1	2845
	21st to end	Night	35% 5% 15% 28% 15% 2	3476
September	1st to 10th	Night	31% 7% 11% 30% 21% 1	1900
	11th to 20th	Night	30% 7% 15% 31% 16% 1	1900
	21st to end	Night	33% 5% 12% 29% 19% 1	2143
October	1st to 10th	Night	25% 4 7% 34% 27% 3	3800
	11th to 20th	Night	30% 5% 11% 28% 23% 1	3779
	21st to end	Night	46% 4 10% 25% 15% 1	4275
November	1st to 10th	Night	43% 6% 12% 23% 14% 2	2536
	11th to 20th	Night	52% 7% 13% 17% 10% 1	2775
	21st to end	Night	52% 5% 15% 21% 7% 1	2800
December	1st to 10th	Night	50% 5% 19% 21% 4	4580
	11th to 20th	Night	63% 6% 10% 15% 5%	5201
	21st to end	Night	71% 5% 8% 12% 4	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	15% 18% 33% 23% 9% 1	288
	11th to 20th	Day	19% 20% 38% 19% 3 1	270
	21st to end	Day	19% 18% 40% 17% 6%	297
February	1st to 10th	Day	13% 26% 41% 13% 5% 1	270
	11th to 20th	Day	19% 27% 33% 17% 4	270
	21st to end	Day	20% 21% 44% 15%	225
March	1st to 10th	Day	21% 22% 36% 14% 6% 1	270
	11th to 20th	Day	23% 18% 38% 14% 6% 2	270
	21st to end	Day	30% 13% 31% 17% 8% 1	391
April	1st to 10th	Day	29% 16% 33% 18% 4	460
	11th to 20th	Day	30% 15% 28% 18% 8% 1	452
	21st to end	Day	25% 18% 30% 19% 7% 2	520
May	1st to 10th	Day	21% 18% 30% 22% 6% 1	653
	11th to 20th	Day	19% 14% 31% 23% 11% 3	675
	21st to end	Day	19% 12% 27% 25% 14% 3	734
June	1st to 10th	Day	10% 9% 31% 30% 17% 3	680
	11th to 20th	Day	15% 9% 33% 30% 12% 2	680
	21st to end	Day	14% 10% 31% 27% 14% 5%	680
July	1st to 10th	Day	9% 5% 21% 31% 25% 10%	671
	11th to 20th	Day	8% 6% 29% 29% 20% 8%	668
	21st to end	Day	7% 4 28% 36% 19% 8%	739
August	1st to 10th	Day	7% 5% 26% 32% 22% 8%	676
	11th to 20th	Day	13% 7% 20% 29% 25% 7%	656
	21st to end	Day	10% 9% 25% 31% 20% 5%	539
September	1st to 10th	Day	16% 8% 26% 27% 18% 5%	490
	11th to 20th	Day	13% 5% 29% 30% 18% 4	490
	21st to end	Day	18% 14% 26% 24% 15% 3	390
October	1st to 10th	Day	14% 15% 31% 25% 13% 2	300
	11th to 20th	Day	25% 17% 36% 15% 7%	300
	21st to end	Day	25% 17% 34% 17% 5% 1	330
November	1st to 10th	Day	21% 15% 35% 22% 6% 1	300
	11th to 20th	Day	21% 22% 36% 17% 5%	300
	21st to end	Day	22% 15% 40% 18% 5%	300
December	1st to 10th	Day	15% 14% 44% 18% 8% 1	300
	11th to 20th	Day	23% 16% 37% 18% 5% 1	300
	21st to end	Day	28% 16% 39% 12% 3 1	330
January	1st to 10th	Night	13% 15% 35% 28% 7% 1	981
	11th to 20th	Night	18% 15% 33% 28% 5% 1	950
	21st to end	Night	20% 11% 34% 28% 6%	1045
February	1st to 10th	Night	14% 15% 37% 27% 6% 1	950
	11th to 20th	Night	15% 15% 40% 23% 7%	929
	21st to end	Night	20% 13% 36% 26% 4	628
March	1st to 10th	Night	17% 14% 37% 26% 7% 1	731
	11th to 20th	Night	19% 13% 32% 29% 7% 1	570
	21st to end	Night	23% 10% 28% 29% 9% 1	627
April	1st to 10th	Night	21% 14% 36% 25% 4	570
	11th to 20th	Night	24% 10% 31% 29% 6%	563
	21st to end	Night	22% 9% 33% 27% 9% 1	570
May	1st to 10th	Night	22% 10% 34% 29% 5% 1	570
	11th to 20th	Night	17% 9% 32% 32% 9% 1	561
	21st to end	Night	15% 6% 28% 36% 13% 1	617
June	1st to 10th	Night	11% 6% 29% 43% 11%	570
	11th to 20th	Night	14% 6% 29% 42% 9%	570
	21st to end	Night	11% 4 25% 44% 15% 1	570
July	1st to 10th	Night	6% 3 21% 37% 31% 2	555
	11th to 20th	Night	8% 4 25% 38% 24% 2	552
	21st to end	Night	6% 2 16% 53% 21% 3	624
August	1st to 10th	Night	7% 2 16% 48% 25% 1	567
	11th to 20th	Night	13% 2 18% 35% 29% 3	564
	21st to end	Night	11% 4 20% 40% 23% 2	627
September	1st to 10th	Night	12% 5% 23% 37% 19% 5%	570
	11th to 20th	Night	11% 4 27% 36% 19% 3	570
	21st to end	Night	16% 8% 26% 33% 16% 1	715
October	1st to 10th	Night	15% 8% 31% 28% 16% 1	760
	11th to 20th	Night	18% 13% 32% 29% 8%	760
	21st to end	Night	21% 11% 30% 30% 7%	836
November	1st to 10th	Night	18% 12% 34% 28% 7% 1	780
	11th to 20th	Night	19% 14% 39% 22% 6%	975
	21st to end	Night	20% 15% 34% 24% 6%	1000
December	1st to 10th	Night	18% 12% 37% 26% 6% 1	1000
	11th to 20th	Night	23% 13% 35% 23% 6% 1	1000
	21st to end	Night	27% 13% 32% 24% 4	1100

Page generated at 2025-01-04 02:24:02. Version ac07

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