Oshkosh
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oshkosh clear sky chart from 2005-11-06 to 2026-07-31.

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% 8% 3 7% 5% 4 5% 4 6% 7% 40%	138400
	Night	12% 10% 4 8% 5% 4 4 3 5% 7% 38%	134906
Transparency	Day	42% 5% 12% 26% 13% 1	141875
	Night	46% 4 11% 23% 14% 2	139508
Seeing	Day	15% 10% 29% 26% 14% 5%	18365
	Night	17% 10% 31% 30% 11% 1	28187

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	10% 11% 5% 14% 6% 6% 5% 4 5% 6% 28%	4691
	11th to 20th	Day	7% 10% 6% 11% 5% 5% 7% 4 6% 7% 32%	4710
	21st to end	Day	9% 10% 4 10% 6% 5% 5% 3 4 5% 36%	5156
February	1st to 10th	Day	9% 12% 4 11% 7% 5% 5% 5% 5% 7% 31%	1890
	11th to 20th	Day	11% 10% 4 8% 5% 3 5% 4 6% 7% 39%	1999
	21st to end	Day	11% 11% 4 9% 6% 6% 5% 4 5% 6% 35%	1730
March	1st to 10th	Day	13% 6% 2 5% 4 4 4 3 5% 7% 47%	4580
	11th to 20th	Day	11% 6% 2 7% 4 4 5% 4 6% 8% 43%	4796
	21st to end	Day	23% 11% 3 9% 5% 4 4 3 4 5% 30%	6099
April	1st to 10th	Day	15% 11% 3 7% 4 5% 5% 4 6% 6% 32%	2520
	11th to 20th	Day	19% 8% 3 7% 4 4 4 4 5% 7% 35%	2494
	21st to end	Day	18% 7% 3 8% 5% 4 5% 3 5% 7% 35%	2663
May	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 7% 8% 44%	7828
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 45%	8222
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 8% 43%	9047
June	1st to 10th	Day	10% 6% 2 6% 5% 4 4 4 6% 8% 45%	2940
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 3 6% 9% 43%	2940
	21st to end	Day	9% 6% 2 6% 4 4 5% 4 7% 10% 43%	2940
July	1st to 10th	Day	11% 5% 2 7% 4 4 5% 4 7% 9% 42%	6500
	11th to 20th	Day	7% 3 2 4 3 4 5% 5% 7% 10% 50%	6500
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 46%	7065
August	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 6% 9% 44%	4563
	11th to 20th	Day	11% 5% 2 4 4 4 5% 4 6% 9% 46%	4008
	21st to end	Day	10% 5% 2 6% 4 5% 5% 4 6% 9% 43%	4312
September	1st to 10th	Day	11% 5% 3 5% 5% 4 4 4 6% 6% 47%	2400
	11th to 20th	Day	10% 5% 2 4 4 4 4 3 5% 8% 50%	2300
	21st to end	Day	12% 7% 3 7% 5% 4 5% 3 6% 7% 42%	2200
October	1st to 10th	Day	14% 6% 3 5% 4 4 4 4 5% 6% 46%	2090
	11th to 20th	Day	18% 9% 2 8% 5% 5% 5% 4 6% 7% 31%	1971
	21st to end	Day	15% 9% 4 8% 6% 4 3 3 5% 6% 38%	1980
November	1st to 10th	Day	12% 8% 3 7% 5% 4 5% 4 5% 6% 42%	1852
	11th to 20th	Day	11% 13% 4 11% 7% 5% 4 4 6% 6% 29%	1886
	21st to end	Day	15% 12% 4 9% 4 5% 4 3 5% 6% 32%	1680
December	1st to 10th	Day	8% 12% 5% 11% 7% 8% 6% 5% 7% 6% 28%	2690
	11th to 20th	Day	10% 16% 5% 11% 6% 5% 5% 4 5% 5% 27%	3088
	21st to end	Day	18% 19% 7% 13% 7% 4 4 3 4 4 17%	4070
January	1st to 10th	Night	11% 13% 6% 11% 5% 3 3 2 4 5% 35%	8232
	11th to 20th	Night	9% 14% 6% 14% 6% 5% 6% 5% 5% 6% 25%	8280
	21st to end	Night	8% 13% 5% 11% 7% 6% 4 4 4 5% 33%	9044
February	1st to 10th	Night	11% 13% 5% 10% 6% 4 4 3 5% 5% 33%	2730
	11th to 20th	Night	10% 9% 4 10% 6% 5% 5% 3 4 5% 40%	2505
	21st to end	Night	14% 12% 4 8% 5% 4 4 2 5% 5% 37%	2076
March	1st to 10th	Night	14% 7% 2 5% 3 4 4 3 5% 6% 45%	5493
	11th to 20th	Night	10% 8% 3 7% 4 5% 6% 3 5% 8% 42%	5402
	21st to end	Night	19% 10% 4 9% 5% 5% 4 3 4 5% 31%	5072
April	1st to 10th	Night	19% 11% 3 7% 4 3 4 3 4 6% 35%	2100
	11th to 20th	Night	21% 8% 3 7% 4 3 4 4 5% 6% 36%	2075
	21st to end	Night	16% 8% 3 7% 5% 5% 4 4 5% 6% 38%	1956
May	1st to 10th	Night	12% 7% 3 6% 4 4 4 4 6% 8% 42%	5033
	11th to 20th	Night	9% 6% 2 7% 5% 5% 5% 4 6% 9% 41%	4670
	21st to end	Night	16% 7% 3 8% 5% 4 4 3 5% 7% 38%	5139
June	1st to 10th	Night	9% 6% 2 5% 4 4 5% 4 5% 8% 47%	1680
	11th to 20th	Night	10% 7% 3 6% 5% 5% 4 4 6% 8% 42%	1680
	21st to end	Night	9% 5% 2 6% 4 4 4 4 7% 9% 46%	1680
July	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 7% 9% 45%	3698
	11th to 20th	Night	8% 3 1 5% 4 3 4 4 6% 9% 53%	3697
	21st to end	Night	5% 4 2 6% 4 5% 5% 4 6% 8% 51%	4027
August	1st to 10th	Night	11% 5% 1 5% 3 3 4 4 6% 8% 49%	2597
	11th to 20th	Night	12% 6% 3 7% 4 4 5% 3 5% 8% 45%	3038
	21st to end	Night	9% 5% 2 5% 4 4 4 3 6% 8% 48%	3586
September	1st to 10th	Night	10% 5% 2 5% 4 4 4 3 6% 8% 52%	2000
	11th to 20th	Night	12% 4 1 5% 4 3 4 3 4 7% 52%	2078
	21st to end	Night	12% 6% 2 6% 5% 4 4 3 5% 6% 48%	2200
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 6% 48%	2306
	11th to 20th	Night	17% 8% 2 7% 4 4 5% 3 5% 7% 38%	2427
	21st to end	Night	17% 10% 3 7% 4 4 4 3 5% 7% 34%	2860
November	1st to 10th	Night	13% 8% 3 6% 4 4 3 4 5% 7% 44%	2666
	11th to 20th	Night	13% 12% 4 10% 6% 5% 4 3 5% 5% 32%	2730
	21st to end	Night	14% 12% 3 9% 6% 4 4 3 5% 7% 34%	2940
December	1st to 10th	Night	9% 11% 4 9% 6% 5% 5% 4 6% 8% 33%	4720
	11th to 20th	Night	13% 17% 6% 11% 5% 5% 4 3 4 5% 27%	5339
	21st to end	Night	19% 17% 6% 11% 5% 5% 4 3 4 5% 21%	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	58% 4 15% 17% 6%	4692
	11th to 20th	Day	51% 4 10% 21% 13% 1	4710
	21st to end	Day	51% 4 9% 22% 14%	5156
February	1st to 10th	Day	52% 5% 12% 20% 10% 1	1890
	11th to 20th	Day	45% 5% 11% 26% 11% 2	2009
	21st to end	Day	51% 5% 11% 21% 10% 2	1730
March	1st to 10th	Day	38% 4 13% 24% 15% 5%	4580
	11th to 20th	Day	39% 4 17% 24% 15% 2	4796
	21st to end	Day	58% 4 9% 18% 11%	6101
April	1st to 10th	Day	50% 7% 12% 20% 10%	2520
	11th to 20th	Day	49% 5% 10% 21% 13% 2	2494
	21st to end	Day	49% 6% 12% 21% 10% 2	2663
May	1st to 10th	Day	35% 5% 11% 31% 15% 2	7863
	11th to 20th	Day	36% 6% 10% 30% 17% 1	8226
	21st to end	Day	39% 6% 9% 27% 17% 4	9061
June	1st to 10th	Day	36% 7% 13% 27% 16% 2	2940
	11th to 20th	Day	38% 7% 13% 27% 14% 1	2940
	21st to end	Day	34% 9% 14% 26% 14% 1	2940
July	1st to 10th	Day	38% 5% 13% 34% 9% 1	6431
	11th to 20th	Day	28% 6% 15% 34% 16% 1	6425
	21st to end	Day	34% 6% 14% 26% 19% 2	6869
August	1st to 10th	Day	36% 6% 15% 29% 13% 1	4548
	11th to 20th	Day	34% 6% 11% 37% 12% 1	4048
	21st to end	Day	38% 6% 13% 26% 16% 1	4311
September	1st to 10th	Day	36% 7% 13% 27% 16% 1	2400
	11th to 20th	Day	32% 7% 15% 33% 12% 1	2300
	21st to end	Day	41% 6% 11% 31% 11%	2200
October	1st to 10th	Day	24% 4 8% 38% 25% 1	3402
	11th to 20th	Day	43% 4 9% 27% 16% 1	3187
	21st to end	Day	43% 4 12% 29% 12% 1	3180
November	1st to 10th	Day	43% 6% 13% 23% 14% 1	1852
	11th to 20th	Day	54% 6% 14% 18% 8% 1	1886
	21st to end	Day	54% 5% 15% 20% 6% 1	1680
December	1st to 10th	Day	57% 7% 14% 19% 4	2690
	11th to 20th	Day	58% 4 11% 18% 8% 1	3085
	21st to end	Day	71% 4 6% 12% 6%	4070
January	1st to 10th	Night	54% 3 10% 23% 10%	8233
	11th to 20th	Night	61% 3 9% 12% 14% 1	8280
	21st to end	Night	55% 3 10% 19% 13%	9044
February	1st to 10th	Night	53% 4 10% 21% 11% 2	2730
	11th to 20th	Night	48% 4 9% 25% 12% 2	2506
	21st to end	Night	49% 4 14% 21% 10% 2	2076
March	1st to 10th	Night	39% 4 15% 25% 13% 3	5493
	11th to 20th	Night	41% 3 16% 22% 14% 3	5402
	21st to end	Night	56% 5% 9% 18% 12% 1	5072
April	1st to 10th	Night	51% 6% 8% 17% 17% 1	2100
	11th to 20th	Night	48% 5% 9% 20% 15% 3	2075
	21st to end	Night	46% 6% 11% 22% 14% 1	1956
May	1st to 10th	Night	39% 4 10% 25% 20% 2	5060
	11th to 20th	Night	38% 5% 13% 23% 19% 1	4671
	21st to end	Night	46% 4 8% 22% 16% 5%	5149
June	1st to 10th	Night	33% 8% 12% 29% 18% 1	1680
	11th to 20th	Night	38% 7% 9% 27% 17% 2	1680
	21st to end	Night	33% 8% 16% 26% 14% 3	1680
July	1st to 10th	Night	37% 3 14% 32% 10% 3	3660
	11th to 20th	Night	28% 4 15% 33% 17% 2	3652
	21st to end	Night	29% 6% 14% 26% 23% 2	3912
August	1st to 10th	Night	33% 6% 14% 27% 19% 2	2588
	11th to 20th	Night	38% 5% 11% 31% 15%	3064
	21st to end	Night	34% 5% 13% 25% 20% 3	3586
September	1st to 10th	Night	32% 7% 11% 26% 23% 1	2000
	11th to 20th	Night	32% 5% 12% 33% 16% 1	2078
	21st to end	Night	37% 6% 11% 30% 16% 1	2200
October	1st to 10th	Night	28% 4 7% 37% 22% 2	3774
	11th to 20th	Night	35% 5% 11% 32% 15% 2	3950
	21st to end	Night	45% 4 10% 24% 16%	4610
November	1st to 10th	Night	41% 6% 12% 25% 15% 2	2666
	11th to 20th	Night	54% 5% 12% 17% 10% 2	2730
	21st to end	Night	52% 4 15% 22% 6% 1	2940
December	1st to 10th	Night	50% 6% 17% 20% 5% 2	4720
	11th to 20th	Night	62% 3 9% 14% 11% 1	5341
	21st to end	Night	66% 5% 8% 14% 7%	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	16% 12% 33% 27% 9% 2	330
	11th to 20th	Day	15% 16% 36% 27% 5% 1	330
	21st to end	Day	17% 12% 37% 28% 7% 1	363
February	1st to 10th	Day	11% 15% 42% 24% 7% 1	330
	11th to 20th	Day	15% 15% 41% 22% 7% 1	330
	21st to end	Day	14% 19% 43% 21% 3	273
March	1st to 10th	Day	20% 13% 39% 21% 6% 1	330
	11th to 20th	Day	21% 16% 31% 21% 7% 3	335
	21st to end	Day	26% 12% 30% 23% 7% 2	594
April	1st to 10th	Day	25% 13% 33% 22% 6%	540
	11th to 20th	Day	25% 15% 28% 20% 9% 3	532
	21st to end	Day	22% 12% 27% 24% 12% 2	540
May	1st to 10th	Day	16% 10% 34% 27% 10% 2	613
	11th to 20th	Day	16% 12% 30% 26% 12% 4	775
	21st to end	Day	16% 7% 29% 28% 15% 6%	844
June	1st to 10th	Day	11% 7% 29% 31% 17% 4	780
	11th to 20th	Day	16% 8% 30% 27% 14% 4	780
	21st to end	Day	12% 9% 26% 33% 16% 4	780
July	1st to 10th	Day	9% 4 18% 32% 26% 11%	771
	11th to 20th	Day	7% 7% 24% 32% 21% 9%	768
	21st to end	Day	8% 4 24% 33% 23% 8%	845
August	1st to 10th	Day	7% 4 22% 31% 26% 9%	726
	11th to 20th	Day	14% 3 16% 24% 30% 12%	557
	21st to end	Day	12% 7% 20% 29% 22% 10%	583
September	1st to 10th	Day	13% 7% 23% 27% 22% 8%	530
	11th to 20th	Day	11% 6% 18% 34% 21% 11%	530
	21st to end	Day	15% 10% 23% 25% 20% 7%	530
October	1st to 10th	Day	18% 10% 23% 28% 17% 5%	420
	11th to 20th	Day	18% 18% 32% 23% 8% 1	330
	21st to end	Day	20% 13% 39% 20% 6% 2	363
November	1st to 10th	Day	14% 18% 35% 25% 7% 1	330
	11th to 20th	Day	16% 22% 37% 17% 8%	330
	21st to end	Day	24% 16% 39% 17% 4	330
December	1st to 10th	Day	16% 17% 42% 20% 5%	330
	11th to 20th	Day	19% 15% 42% 17% 6% 1	330
	21st to end	Day	25% 14% 38% 18% 4 1	363
January	1st to 10th	Night	17% 14% 35% 26% 7%	1050
	11th to 20th	Night	19% 11% 39% 24% 6% 1	1050
	21st to end	Night	18% 11% 36% 28% 7%	1155
February	1st to 10th	Night	17% 12% 37% 26% 6% 1	1050
	11th to 20th	Night	15% 13% 38% 25% 8%	870
	21st to end	Night	20% 12% 36% 28% 4 1	692
March	1st to 10th	Night	20% 10% 32% 28% 9% 1	840
	11th to 20th	Night	18% 11% 36% 29% 6% 1	792
	21st to end	Night	21% 8% 31% 30% 9% 1	693
April	1st to 10th	Night	25% 11% 34% 23% 6%	630
	11th to 20th	Night	24% 10% 30% 28% 7% 1	623
	21st to end	Night	20% 9% 33% 31% 7%	630
May	1st to 10th	Night	19% 10% 33% 29% 9%	630
	11th to 20th	Night	18% 7% 34% 32% 9%	621
	21st to end	Night	15% 7% 26% 35% 17%	683
June	1st to 10th	Night	10% 6% 30% 38% 16% 1	630
	11th to 20th	Night	13% 7% 31% 36% 11% 1	630
	21st to end	Night	11% 4 26% 41% 17% 1	630
July	1st to 10th	Night	9% 2 19% 44% 25% 1	615
	11th to 20th	Night	9% 4 22% 41% 22% 2	612
	21st to end	Night	6% 3 20% 47% 23% 2	687
August	1st to 10th	Night	9% 3 15% 47% 24% 2	597
	11th to 20th	Night	10% 3 19% 38% 27% 4	594
	21st to end	Night	10% 4 19% 39% 25% 2	660
September	1st to 10th	Night	10% 6% 25% 35% 19% 4	600
	11th to 20th	Night	13% 4 23% 32% 24% 3	678
	21st to end	Night	13% 8% 25% 30% 21% 2	800
October	1st to 10th	Night	15% 9% 28% 32% 16% 1	800
	11th to 20th	Night	23% 11% 33% 26% 7%	800
	21st to end	Night	23% 12% 29% 27% 8% 1	880
November	1st to 10th	Night	16% 12% 37% 26% 7% 1	820
	11th to 20th	Night	20% 18% 36% 20% 5%	840
	21st to end	Night	20% 14% 37% 22% 6%	1050
December	1st to 10th	Night	20% 16% 38% 21% 6%	1050
	11th to 20th	Night	23% 13% 35% 22% 6% 1	1050
	21st to end	Night	27% 11% 34% 24% 4	1155

Page generated at 2026-07-28 02:25:23. Version ac07

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