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 2025-03-27.

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 8% 5% 4 5% 4 6% 7% 39%	108996
	Night	12% 10% 4 8% 5% 4 4 3 5% 6% 38%	110540
Transparency	Day	43% 6% 12% 25% 13% 1	112516
	Night	46% 5% 11% 22% 14% 2	115161
Seeing	Day	16% 10% 29% 26% 15% 5%	16385
	Night	17% 9% 31% 30% 11% 1	26449

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% 10% 5% 15% 7% 6% 5% 4 5% 6% 30%	3617
	11th to 20th	Day	9% 10% 5% 11% 5% 5% 8% 5% 6% 7% 29%	3620
	21st to end	Day	12% 12% 5% 11% 6% 4 4 3 4 5% 33%	3982
February	1st to 10th	Day	9% 12% 4 10% 7% 5% 5% 5% 5% 6% 32%	1800
	11th to 20th	Day	11% 10% 4 8% 5% 3 5% 4 6% 6% 38%	1901
	21st to end	Day	11% 11% 4 9% 6% 6% 5% 4 5% 6% 34%	1650
March	1st to 10th	Day	13% 7% 2 6% 4 4 4 3 4 7% 47%	3220
	11th to 20th	Day	10% 6% 2 7% 4 4 5% 4 5% 7% 44%	3394
	21st to end	Day	20% 11% 3 10% 5% 5% 4 3 3 5% 30%	4237
April	1st to 10th	Day	15% 11% 3 7% 5% 5% 5% 4 6% 6% 33%	2280
	11th to 20th	Day	19% 8% 3 6% 4 4 4 4 5% 6% 35%	2254
	21st to end	Day	18% 7% 3 8% 5% 5% 5% 3 5% 6% 35%	2409
May	1st to 10th	Day	12% 7% 2 7% 5% 5% 5% 4 6% 6% 41%	4197
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 47%	4399
	21st to end	Day	12% 6% 2 7% 5% 4 5% 4 6% 8% 40%	4824
June	1st to 10th	Day	10% 6% 2 5% 5% 4 3 4 7% 8% 46%	2660
	11th to 20th	Day	12% 6% 2 5% 4 4 5% 3 6% 9% 44%	2660
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 7% 10% 44%	2660
July	1st to 10th	Day	12% 5% 2 7% 4 4 5% 4 7% 9% 39%	4440
	11th to 20th	Day	5% 3 1 4 3 4 5% 5% 8% 11% 50%	4440
	21st to end	Day	8% 6% 2 5% 5% 4 5% 4 6% 8% 48%	4813
August	1st to 10th	Day	9% 5% 2 6% 5% 5% 6% 4 6% 9% 44%	4423
	11th to 20th	Day	11% 5% 2 4 4 4 5% 4 6% 9% 46%	3883
	21st to end	Day	10% 5% 2 7% 4 5% 5% 4 6% 8% 43%	4180
September	1st to 10th	Day	12% 5% 3 5% 5% 4 4 4 6% 6% 47%	2280
	11th to 20th	Day	11% 5% 2 4 4 4 3 3 5% 8% 50%	2185
	21st to end	Day	12% 7% 3 7% 5% 4 5% 3 6% 7% 42%	2090
October	1st to 10th	Day	14% 6% 3 5% 4 4 4 4 5% 5% 46%	1986
	11th to 20th	Day	18% 9% 2 8% 5% 5% 5% 4 6% 7% 32%	1873
	21st to end	Day	15% 10% 4 8% 6% 4 3 3 5% 5% 37%	1881
November	1st to 10th	Day	13% 8% 3 7% 5% 3 5% 4 5% 6% 41%	1762
	11th to 20th	Day	11% 13% 4 11% 7% 5% 4 4 6% 6% 29%	1796
	21st to end	Day	15% 12% 4 9% 5% 5% 4 3 5% 6% 32%	1600
December	1st to 10th	Day	8% 11% 5% 11% 7% 8% 6% 5% 7% 6% 28%	2610
	11th to 20th	Day	10% 16% 5% 11% 6% 5% 5% 4 5% 5% 26%	3008
	21st to end	Day	18% 19% 6% 13% 6% 4 4 3 4 4 17%	3982
January	1st to 10th	Night	9% 13% 7% 11% 5% 4 3 3 4 5% 37%	6348
	11th to 20th	Night	10% 13% 5% 13% 6% 5% 6% 5% 5% 6% 26%	6360
	21st to end	Night	10% 15% 6% 11% 6% 5% 4 3 4 5% 32%	6982
February	1st to 10th	Night	11% 13% 5% 10% 6% 4 4 3 5% 5% 34%	2600
	11th to 20th	Night	9% 10% 4 10% 6% 5% 5% 3 4 5% 39%	2383
	21st to end	Night	15% 12% 4 8% 5% 4 3 2 5% 5% 37%	1980
March	1st to 10th	Night	14% 8% 2 5% 4 4 3 3 6% 6% 43%	3853
	11th to 20th	Night	9% 8% 3 7% 5% 5% 6% 3 5% 7% 42%	3816
	21st to end	Night	18% 10% 4 10% 5% 4 4 3 5% 5% 30%	3532
April	1st to 10th	Night	18% 11% 3 8% 5% 3 4 3 4 6% 35%	1900
	11th to 20th	Night	20% 8% 3 7% 4 3 3 4 6% 6% 36%	1875
	21st to end	Night	17% 8% 3 7% 5% 5% 3 5% 4 6% 38%	1770
May	1st to 10th	Night	15% 7% 3 8% 5% 5% 4 4 6% 7% 37%	2699
	11th to 20th	Night	12% 7% 2 7% 5% 5% 5% 4 6% 7% 42%	2506
	21st to end	Night	15% 6% 3 7% 5% 4 4 3 6% 6% 39%	2743
June	1st to 10th	Night	9% 6% 2 6% 4 4 5% 4 5% 9% 47%	1520
	11th to 20th	Night	10% 6% 3 6% 5% 4 4 4 5% 9% 44%	1520
	21st to end	Night	8% 4 2 6% 4 4 4 4 7% 10% 47%	1520
July	1st to 10th	Night	15% 7% 2 5% 4 4 3 3 6% 7% 44%	2530
	11th to 20th	Night	4 3 1 5% 4 3 3 4 7% 10% 55%	2530
	21st to end	Night	6% 4 2 5% 4 5% 5% 4 7% 8% 49%	2750
August	1st to 10th	Night	12% 5% 1 5% 3 3 4 4 6% 9% 48%	2517
	11th to 20th	Night	11% 6% 3 7% 4 4 5% 3 5% 8% 45%	2943
	21st to end	Night	10% 5% 2 5% 4 4 4 3 6% 8% 48%	3476
September	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 6% 8% 52%	1900
	11th to 20th	Night	13% 4 1 5% 3 3 4 3 4 6% 52%	1974
	21st to end	Night	12% 6% 2 6% 5% 4 4 3 5% 6% 47%	2090
October	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 5% 6% 48%	2190
	11th to 20th	Night	16% 8% 2 7% 4 4 5% 4 5% 7% 38%	2305
	21st to end	Night	17% 10% 3 7% 4 4 5% 3 5% 8% 33%	2717
November	1st to 10th	Night	13% 8% 3 6% 4 4 3 4 5% 7% 44%	2536
	11th to 20th	Night	14% 12% 4 10% 6% 5% 4 4 5% 5% 31%	2600
	21st to end	Night	15% 12% 3 9% 6% 4 4 3 5% 7% 34%	2800
December	1st to 10th	Night	9% 11% 4 9% 6% 5% 5% 4 6% 8% 34%	4580
	11th to 20th	Night	14% 18% 6% 11% 5% 5% 4 3 3 5% 27%	5199
	21st to end	Night	19% 17% 6% 11% 5% 5% 4 3 4 5% 21%	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	54% 4 15% 19% 7%	3618
	11th to 20th	Day	53% 5% 10% 17% 13% 1	3620
	21st to end	Day	54% 5% 10% 21% 11%	3982
February	1st to 10th	Day	52% 6% 12% 20% 10% 1	1800
	11th to 20th	Day	46% 6% 12% 25% 11% 2	1911
	21st to end	Day	51% 6% 11% 20% 10% 2	1650
March	1st to 10th	Day	38% 5% 11% 27% 16% 3	3220
	11th to 20th	Day	38% 5% 15% 25% 15% 2	3394
	21st to end	Day	57% 6% 9% 21% 7% 1	4237
April	1st to 10th	Day	50% 7% 13% 20% 10%	2280
	11th to 20th	Day	49% 5% 10% 20% 14% 2	2254
	21st to end	Day	49% 7% 11% 20% 11% 2	2409
May	1st to 10th	Day	40% 7% 12% 23% 16% 1	4235
	11th to 20th	Day	35% 6% 11% 33% 14% 1	4403
	21st to end	Day	39% 9% 11% 22% 17% 2	4837
June	1st to 10th	Day	35% 7% 13% 28% 15% 2	2660
	11th to 20th	Day	37% 8% 13% 27% 14% 1	2660
	21st to end	Day	33% 10% 14% 27% 14% 2	2660
July	1st to 10th	Day	40% 6% 14% 28% 10% 2	4371
	11th to 20th	Day	25% 7% 15% 34% 17% 2	4365
	21st to end	Day	33% 7% 14% 22% 22% 3	4662
August	1st to 10th	Day	36% 6% 15% 29% 12% 1	4408
	11th to 20th	Day	33% 7% 11% 37% 12% 1	3923
	21st to end	Day	38% 6% 13% 25% 16% 1	4179
September	1st to 10th	Day	37% 7% 13% 27% 16% 1	2280
	11th to 20th	Day	33% 7% 14% 33% 12% 1	2185
	21st to end	Day	41% 6% 12% 30% 11%	2090
October	1st to 10th	Day	24% 4 8% 38% 25% 1	3298
	11th to 20th	Day	43% 4 9% 27% 16% 1	3089
	21st to end	Day	43% 4 13% 28% 12% 1	3081
November	1st to 10th	Day	43% 6% 13% 23% 13% 1	1762
	11th to 20th	Day	55% 6% 14% 16% 7% 1	1796
	21st to end	Day	53% 5% 15% 20% 6% 1	1600
December	1st to 10th	Day	56% 7% 14% 19% 4	2610
	11th to 20th	Day	59% 4 11% 18% 7% 1	3005
	21st to end	Day	71% 4 6% 12% 6%	3982
January	1st to 10th	Night	52% 3 9% 24% 12% 1	6348
	11th to 20th	Night	59% 3 9% 12% 15% 1	6360
	21st to end	Night	56% 3 11% 17% 11%	6982
February	1st to 10th	Night	53% 5% 10% 20% 11% 2	2600
	11th to 20th	Night	49% 4 9% 24% 12% 2	2384
	21st to end	Night	49% 4 14% 20% 11% 2	1980
March	1st to 10th	Night	40% 5% 14% 27% 11% 3	3853
	11th to 20th	Night	41% 4 11% 24% 17% 2	3816
	21st to end	Night	55% 6% 8% 19% 10% 2	3532
April	1st to 10th	Night	50% 6% 8% 16% 17% 1	1900
	11th to 20th	Night	47% 5% 9% 20% 15% 3	1875
	21st to end	Night	47% 6% 11% 21% 14% 1	1770
May	1st to 10th	Night	44% 6% 13% 17% 18% 1	2726
	11th to 20th	Night	39% 7% 11% 27% 15% 1	2507
	21st to end	Night	44% 6% 11% 19% 16% 4	2751
June	1st to 10th	Night	32% 8% 12% 29% 17% 1	1520
	11th to 20th	Night	36% 8% 10% 28% 17% 2	1520
	21st to end	Night	31% 8% 16% 26% 15% 3	1520
July	1st to 10th	Night	41% 4 16% 22% 13% 5%	2490
	11th to 20th	Night	24% 5% 17% 35% 17% 2	2482
	21st to end	Night	30% 8% 14% 23% 23% 2	2662
August	1st to 10th	Night	34% 6% 14% 27% 18% 2	2508
	11th to 20th	Night	37% 5% 11% 31% 16%	2969
	21st to end	Night	34% 5% 13% 24% 21% 3	3476
September	1st to 10th	Night	31% 7% 11% 26% 24% 1	1900
	11th to 20th	Night	32% 5% 12% 33% 16% 1	1974
	21st to end	Night	37% 6% 11% 29% 15% 1	2090
October	1st to 10th	Night	28% 4 7% 37% 22% 2	3658
	11th to 20th	Night	34% 5% 11% 32% 15% 2	3828
	21st to end	Night	45% 4 10% 24% 16%	4467
November	1st to 10th	Night	40% 6% 12% 25% 15% 2	2536
	11th to 20th	Night	55% 5% 12% 16% 10% 1	2600
	21st to end	Night	52% 5% 15% 22% 6% 1	2800
December	1st to 10th	Night	49% 6% 18% 20% 5% 2	4580
	11th to 20th	Night	62% 3 9% 14% 11% 1	5201
	21st to end	Night	67% 5% 8% 14% 7%	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	16% 12% 32% 28% 10% 2	300
	11th to 20th	Day	17% 16% 34% 28% 6% 1	300
	21st to end	Day	18% 11% 36% 28% 7% 1	330
February	1st to 10th	Day	11% 14% 43% 23% 7% 1	300
	11th to 20th	Day	16% 15% 40% 22% 7% 1	300
	21st to end	Day	14% 19% 42% 21% 3	249
March	1st to 10th	Day	20% 12% 41% 20% 6% 1	300
	11th to 20th	Day	20% 17% 29% 22% 8% 4	305
	21st to end	Day	26% 13% 27% 24% 8% 2	530
April	1st to 10th	Day	25% 11% 33% 24% 7%	460
	11th to 20th	Day	25% 14% 28% 21% 9% 3	452
	21st to end	Day	21% 13% 27% 24% 13% 3	460
May	1st to 10th	Day	18% 10% 33% 27% 10% 2	526
	11th to 20th	Day	17% 10% 29% 27% 12% 4	675
	21st to end	Day	16% 7% 28% 26% 17% 6%	734
June	1st to 10th	Day	11% 7% 30% 30% 17% 5%	680
	11th to 20th	Day	16% 7% 29% 29% 16% 4	680
	21st to end	Day	11% 8% 26% 33% 17% 5%	680
July	1st to 10th	Day	9% 4 18% 30% 28% 11%	671
	11th to 20th	Day	7% 6% 24% 32% 21% 10%	668
	21st to end	Day	9% 3 23% 33% 24% 9%	739
August	1st to 10th	Day	7% 5% 22% 31% 26% 9%	676
	11th to 20th	Day	14% 3 16% 24% 30% 12%	515
	21st to end	Day	12% 7% 20% 29% 21% 10%	539
September	1st to 10th	Day	13% 7% 23% 27% 23% 7%	490
	11th to 20th	Day	11% 6% 18% 35% 19% 11%	490
	21st to end	Day	16% 11% 24% 24% 19% 6%	490
October	1st to 10th	Day	19% 10% 23% 27% 16% 5%	386
	11th to 20th	Day	19% 18% 30% 25% 8%	300
	21st to end	Day	22% 14% 39% 18% 6% 1	330
November	1st to 10th	Day	15% 16% 35% 25% 8% 1	300
	11th to 20th	Day	16% 21% 39% 17% 7%	300
	21st to end	Day	23% 16% 39% 18% 4	300
December	1st to 10th	Day	16% 17% 42% 20% 5%	300
	11th to 20th	Day	20% 14% 40% 18% 7% 1	300
	21st to end	Day	25% 15% 36% 19% 5% 1	330
January	1st to 10th	Night	17% 13% 35% 27% 8%	1000
	11th to 20th	Night	20% 10% 38% 25% 6% 1	1000
	21st to end	Night	19% 10% 36% 28% 7%	1100
February	1st to 10th	Night	17% 12% 37% 26% 6% 1	1000
	11th to 20th	Night	15% 13% 38% 25% 8%	828
	21st to end	Night	20% 11% 36% 28% 4 1	660
March	1st to 10th	Night	20% 10% 32% 28% 8% 1	800
	11th to 20th	Night	16% 11% 36% 30% 6% 1	754
	21st to end	Night	21% 6% 30% 31% 9% 1	647
April	1st to 10th	Night	24% 10% 35% 25% 6%	570
	11th to 20th	Night	23% 10% 31% 29% 7% 1	563
	21st to end	Night	21% 8% 32% 31% 8%	570
May	1st to 10th	Night	20% 9% 33% 29% 8%	570
	11th to 20th	Night	19% 5% 34% 32% 9%	561
	21st to end	Night	14% 6% 25% 36% 18%	617
June	1st to 10th	Night	10% 6% 29% 38% 16% 1	570
	11th to 20th	Night	14% 5% 31% 38% 11% 1	570
	21st to end	Night	9% 4 26% 43% 17% 1	570
July	1st to 10th	Night	10% 2 18% 43% 26% 1	555
	11th to 20th	Night	9% 4 22% 40% 23% 2	552
	21st to end	Night	6% 2 19% 46% 25% 2	624
August	1st to 10th	Night	9% 2 16% 47% 24% 2	567
	11th to 20th	Night	9% 2 18% 38% 28% 4	564
	21st to end	Night	11% 4 19% 39% 24% 2	627
September	1st to 10th	Night	10% 6% 25% 36% 19% 4	570
	11th to 20th	Night	14% 4 24% 33% 22% 3	644
	21st to end	Night	14% 9% 26% 29% 21% 2	760
October	1st to 10th	Night	15% 9% 26% 32% 16% 1	760
	11th to 20th	Night	23% 10% 33% 26% 7%	760
	21st to end	Night	24% 12% 29% 26% 8% 1	836
November	1st to 10th	Night	16% 12% 37% 26% 8% 1	780
	11th to 20th	Night	21% 17% 37% 20% 5%	800
	21st to end	Night	20% 14% 37% 23% 6%	1000
December	1st to 10th	Night	20% 15% 38% 21% 6%	1000
	11th to 20th	Night	24% 12% 35% 22% 6% 1	1000
	21st to end	Night	27% 11% 34% 24% 4	1100

Page generated at 2025-03-24 08:04:27. Version ac07

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