Dubuque
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dubuque clear sky chart from 2005-11-06 to 2026-04-02.

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	12% 9% 3 8% 5% 4 4 4 6% 7% 37%	131781
	Night	12% 10% 4 8% 5% 4 4 3 5% 6% 39%	130350
Transparency	Day	44% 6% 12% 24% 13% 1	135293
	Night	45% 6% 12% 22% 14% 2	134913
Seeing	Day	16% 12% 30% 25% 13% 4	17725
	Night	17% 10% 32% 29% 11% 1	27734

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	7% 12% 8% 18% 8% 6% 5% 4 4 5% 24%	4691
	11th to 20th	Day	6% 10% 6% 12% 7% 5% 6% 7% 8% 6% 27%	4710
	21st to end	Day	9% 13% 5% 10% 5% 4 4 3 5% 6% 35%	5710
February	1st to 10th	Day	11% 14% 5% 10% 5% 4 5% 5% 5% 6% 30%	1890
	11th to 20th	Day	13% 11% 3 7% 5% 4 4 3 5% 7% 37%	1918
	21st to end	Day	13% 11% 3 10% 5% 3 4 3 4 7% 35%	1730
March	1st to 10th	Day	16% 8% 3 6% 4 3 3 2 4 5% 46%	4616
	11th to 20th	Day	11% 7% 3 6% 4 4 4 4 5% 9% 44%	5090
	21st to end	Day	19% 13% 4 11% 5% 4 4 3 4 5% 27%	5898
April	1st to 10th	Day	17% 14% 4 7% 5% 4 5% 3 5% 6% 32%	2412
	11th to 20th	Day	15% 12% 3 9% 5% 4 5% 4 5% 6% 34%	2374
	21st to end	Day	19% 10% 2 8% 4 4 4 3 5% 7% 34%	2400
May	1st to 10th	Day	14% 8% 3 7% 4 4 5% 4 6% 7% 38%	6175
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 5% 7% 42%	6319
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	6935
June	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 8% 43%	2800
	11th to 20th	Day	10% 7% 3 7% 4 4 4 4 7% 8% 43%	2800
	21st to end	Day	11% 7% 2 7% 4 5% 5% 5% 6% 9% 39%	2800
July	1st to 10th	Day	8% 7% 3 7% 5% 5% 5% 5% 8% 10% 37%	6360
	11th to 20th	Day	9% 5% 2 6% 4 4 4 3 7% 9% 46%	6360
	21st to end	Day	9% 7% 3 7% 5% 5% 6% 5% 8% 10% 36%	6924
August	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 8% 41%	4300
	11th to 20th	Day	10% 6% 3 6% 4 4 5% 4 7% 9% 44%	4022
	21st to end	Day	8% 5% 2 6% 4 3 4 4 7% 9% 48%	4312
September	1st to 10th	Day	13% 5% 2 6% 4 3 4 3 5% 7% 47%	2400
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 5% 7% 51%	2390
	21st to end	Day	12% 5% 2 6% 5% 4 4 3 5% 7% 46%	2155
October	1st to 10th	Day	13% 7% 2 6% 4 3 3 3 5% 6% 48%	2000
	11th to 20th	Day	17% 10% 3 7% 4 4 4 3 4 6% 39%	2000
	21st to end	Day	17% 10% 3 6% 4 4 4 2 5% 6% 40%	2094
November	1st to 10th	Day	11% 8% 3 8% 5% 4 4 3 5% 5% 44%	1852
	11th to 20th	Day	13% 13% 4 9% 5% 4 4 4 5% 6% 34%	1816
	21st to end	Day	14% 13% 4 9% 5% 3 3 3 5% 6% 36%	1680
December	1st to 10th	Day	7% 9% 5% 10% 6% 4 5% 3 5% 6% 40%	2690
	11th to 20th	Day	14% 14% 5% 14% 6% 5% 5% 4 5% 6% 23%	3088
	21st to end	Day	18% 24% 9% 14% 4 4 2 2 4 4 14%	4070
January	1st to 10th	Night	9% 12% 6% 15% 6% 5% 4 3 4 5% 31%	8232
	11th to 20th	Night	9% 14% 5% 14% 7% 6% 5% 5% 6% 5% 24%	8280
	21st to end	Night	10% 14% 5% 8% 6% 5% 4 3 4 6% 35%	8486
February	1st to 10th	Night	11% 13% 4 10% 7% 5% 4 3 4 4 33%	2730
	11th to 20th	Night	10% 10% 3 8% 6% 5% 4 3 4 6% 41%	2587
	21st to end	Night	14% 12% 3 7% 5% 4 4 3 4 6% 38%	2076
March	1st to 10th	Night	17% 9% 4 6% 4 3 4 3 3 4 44%	5493
	11th to 20th	Night	10% 7% 3 6% 4 4 3 3 4 7% 50%	5095
	21st to end	Night	20% 13% 5% 11% 5% 5% 4 3 4 5% 26%	5271
April	1st to 10th	Night	15% 10% 3 6% 5% 3 4 3 5% 6% 40%	2010
	11th to 20th	Night	16% 10% 2 7% 4 4 5% 3 4 6% 39%	1975
	21st to end	Night	15% 9% 3 7% 5% 4 4 4 5% 6% 37%	2000
May	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	3731
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 46%	3596
	21st to end	Night	14% 6% 2 6% 4 4 4 4 6% 7% 43%	3942
June	1st to 10th	Night	8% 4 2 6% 5% 4 4 4 7% 8% 48%	1600
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 4 7% 10% 44%	1600
	21st to end	Night	10% 5% 2 6% 4 4 4 4 7% 7% 46%	1600
July	1st to 10th	Night	10% 6% 3 6% 4 4 5% 4 6% 9% 41%	3618
	11th to 20th	Night	5% 5% 2 5% 4 4 4 3 6% 9% 52%	3617
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 6% 9% 45%	3947
August	1st to 10th	Night	6% 5% 2 5% 4 4 5% 4 6% 9% 51%	2855
	11th to 20th	Night	9% 5% 2 5% 4 4 4 3 5% 8% 51%	3032
	21st to end	Night	9% 5% 2 6% 4 4 3 3 5% 8% 51%	3586
September	1st to 10th	Night	10% 4 2 5% 2 3 4 3 5% 6% 56%	2000
	11th to 20th	Night	11% 4 2 6% 4 4 4 4 5% 8% 50%	2000
	21st to end	Night	9% 5% 2 5% 3 4 4 4 5% 6% 52%	2232
October	1st to 10th	Night	11% 5% 1 5% 4 4 4 4 5% 6% 53%	2400
	11th to 20th	Night	16% 7% 3 6% 4 3 3 3 5% 7% 44%	2400
	21st to end	Night	17% 8% 3 7% 5% 4 4 3 4 6% 39%	2745
November	1st to 10th	Night	11% 7% 3 7% 4 3 4 3 5% 6% 48%	2666
	11th to 20th	Night	14% 11% 4 8% 5% 4 4 3 5% 6% 36%	2799
	21st to end	Night	16% 10% 4 9% 5% 3 4 3 4 5% 37%	2940
December	1st to 10th	Night	8% 7% 3 8% 6% 6% 5% 4 5% 7% 41%	4720
	11th to 20th	Night	14% 15% 5% 10% 5% 4 4 3 4 5% 30%	5339
	21st to end	Night	18% 19% 7% 14% 6% 5% 5% 3 4 4 15%	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	63% 4 11% 15% 7%	4692
	11th to 20th	Day	50% 6% 11% 16% 16% 1	4710
	21st to end	Day	49% 4 14% 24% 9%	5710
February	1st to 10th	Day	53% 6% 13% 18% 9% 1	1890
	11th to 20th	Day	47% 5% 13% 24% 9% 2	1927
	21st to end	Day	50% 7% 12% 20% 10% 2	1730
March	1st to 10th	Day	40% 5% 11% 29% 11% 3	4616
	11th to 20th	Day	37% 5% 13% 32% 11% 2	5090
	21st to end	Day	58% 7% 12% 15% 7% 1	5900
April	1st to 10th	Day	52% 7% 10% 21% 10%	2412
	11th to 20th	Day	50% 7% 10% 20% 11% 2	2374
	21st to end	Day	50% 6% 10% 20% 12% 2	2400
May	1st to 10th	Day	43% 7% 9% 22% 18% 1	6213
	11th to 20th	Day	39% 8% 10% 28% 13% 2	6323
	21st to end	Day	42% 8% 11% 26% 11% 2	6949
June	1st to 10th	Day	35% 8% 14% 25% 16% 1	2800
	11th to 20th	Day	38% 7% 13% 23% 17% 2	2800
	21st to end	Day	40% 8% 14% 24% 12% 2	2800
July	1st to 10th	Day	39% 7% 15% 28% 9% 1	6291
	11th to 20th	Day	33% 7% 14% 31% 14% 1	6285
	21st to end	Day	40% 10% 15% 19% 15% 1	6728
August	1st to 10th	Day	37% 8% 15% 26% 12% 1	4285
	11th to 20th	Day	35% 7% 14% 29% 14% 1	4061
	21st to end	Day	32% 6% 15% 31% 15% 2	4311
September	1st to 10th	Day	37% 6% 12% 26% 18% 2	2400
	11th to 20th	Day	32% 7% 12% 31% 16% 2	2390
	21st to end	Day	37% 6% 10% 28% 17% 2	2155
October	1st to 10th	Day	23% 4 6% 38% 27% 1	3260
	11th to 20th	Day	34% 4 10% 25% 24% 3	3240
	21st to end	Day	41% 4 11% 28% 13% 2	3358
November	1st to 10th	Day	41% 5% 13% 25% 13% 2	1852
	11th to 20th	Day	52% 5% 13% 20% 10% 1	1816
	21st to end	Day	50% 5% 16% 21% 7% 1	1680
December	1st to 10th	Day	44% 5% 18% 25% 6% 1	2690
	11th to 20th	Day	60% 6% 13% 13% 7% 1	3085
	21st to end	Day	75% 4 9% 8% 4	4070
January	1st to 10th	Night	56% 5% 15% 18% 7%	8233
	11th to 20th	Night	61% 5% 11% 11% 12%	8280
	21st to end	Night	51% 4 12% 22% 10%	8486
February	1st to 10th	Night	53% 5% 11% 18% 11% 1	2730
	11th to 20th	Night	46% 5% 12% 23% 13% 1	2588
	21st to end	Night	48% 5% 13% 20% 11% 3	2076
March	1st to 10th	Night	46% 4 10% 23% 13% 5%	5493
	11th to 20th	Night	34% 5% 11% 33% 14% 3	5095
	21st to end	Night	62% 5% 9% 16% 8% 1	5271
April	1st to 10th	Night	45% 6% 11% 23% 14% 1	2010
	11th to 20th	Night	46% 5% 10% 19% 16% 3	1975
	21st to end	Night	46% 6% 14% 20% 13% 2	2000
May	1st to 10th	Night	42% 7% 11% 19% 19% 2	3756
	11th to 20th	Night	36% 7% 13% 23% 17% 3	3597
	21st to end	Night	37% 7% 11% 29% 14% 2	3950
June	1st to 10th	Night	31% 9% 15% 26% 18% 2	1600
	11th to 20th	Night	35% 6% 13% 24% 20% 3	1600
	21st to end	Night	35% 9% 13% 23% 16% 4	1600
July	1st to 10th	Night	38% 7% 15% 25% 13% 2	3580
	11th to 20th	Night	27% 7% 15% 31% 18% 2	3572
	21st to end	Night	34% 9% 18% 20% 17% 2	3832
August	1st to 10th	Night	29% 7% 15% 30% 18% 1	2846
	11th to 20th	Night	31% 6% 15% 32% 15% 1	3059
	21st to end	Night	31% 7% 12% 28% 18% 4	3586
September	1st to 10th	Night	28% 6% 12% 27% 25% 2	2000
	11th to 20th	Night	32% 5% 12% 31% 16% 3	2000
	21st to end	Night	31% 6% 10% 30% 22% 2	2232
October	1st to 10th	Night	24% 5% 7% 34% 30% 2	3920
	11th to 20th	Night	30% 5% 10% 22% 30% 3	3899
	21st to end	Night	45% 5% 9% 24% 15% 2	4431
November	1st to 10th	Night	38% 5% 12% 24% 17% 2	2666
	11th to 20th	Night	51% 5% 13% 20% 11% 1	2799
	21st to end	Night	49% 5% 12% 24% 9%	2940
December	1st to 10th	Night	42% 5% 17% 27% 8% 1	4720
	11th to 20th	Night	57% 6% 13% 18% 6% 1	5341
	21st to end	Night	72% 5% 8% 10% 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% 31% 26% 9% 1	330
	11th to 20th	Day	20% 16% 43% 16% 4 1	330
	21st to end	Day	19% 18% 40% 19% 3 1	363
February	1st to 10th	Day	15% 25% 37% 18% 4 1	330
	11th to 20th	Day	20% 25% 32% 19% 3 1	330
	21st to end	Day	22% 20% 46% 10% 2	273
March	1st to 10th	Day	16% 21% 42% 18% 3	330
	11th to 20th	Day	19% 22% 39% 15% 4 2	330
	21st to end	Day	29% 16% 34% 16% 4 1	497
April	1st to 10th	Day	25% 19% 32% 19% 4	504
	11th to 20th	Day	25% 21% 25% 19% 9% 1	492
	21st to end	Day	23% 18% 30% 20% 9% 1	500
May	1st to 10th	Day	20% 12% 34% 23% 9% 2	658
	11th to 20th	Day	21% 13% 27% 24% 11% 3	725
	21st to end	Day	16% 13% 27% 27% 13% 4	789
June	1st to 10th	Day	11% 8% 27% 32% 16% 5%	730
	11th to 20th	Day	15% 7% 30% 32% 11% 4	730
	21st to end	Day	14% 8% 32% 30% 12% 5%	730
July	1st to 10th	Day	8% 5% 20% 33% 23% 11%	721
	11th to 20th	Day	8% 6% 27% 31% 21% 7%	718
	21st to end	Day	9% 4 26% 35% 21% 6%	794
August	1st to 10th	Day	7% 3 23% 34% 25% 9%	726
	11th to 20th	Day	14% 5% 20% 28% 21% 12%	631
	21st to end	Day	9% 7% 22% 32% 22% 8%	583
September	1st to 10th	Day	13% 9% 23% 29% 20% 6%	530
	11th to 20th	Day	11% 5% 20% 32% 25% 7%	530
	21st to end	Day	13% 12% 26% 25% 18% 5%	485
October	1st to 10th	Day	17% 9% 31% 27% 13% 3	330
	11th to 20th	Day	23% 18% 33% 18% 7%	330
	21st to end	Day	26% 15% 31% 21% 6% 1	363
November	1st to 10th	Day	15% 18% 38% 19% 8% 2	330
	11th to 20th	Day	20% 22% 34% 18% 6% 1	330
	21st to end	Day	25% 15% 38% 19% 4	330
December	1st to 10th	Day	15% 17% 43% 17% 7% 1	330
	11th to 20th	Day	18% 17% 39% 19% 6% 1	330
	21st to end	Day	27% 17% 37% 15% 4	363
January	1st to 10th	Night	15% 16% 37% 26% 7%	1050
	11th to 20th	Night	18% 15% 38% 24% 5%	1050
	21st to end	Night	20% 14% 36% 26% 5%	1155
February	1st to 10th	Night	18% 14% 39% 23% 5%	1050
	11th to 20th	Night	17% 15% 39% 26% 4	953
	21st to end	Night	22% 15% 40% 20% 3	692
March	1st to 10th	Night	22% 14% 36% 23% 5%	840
	11th to 20th	Night	18% 13% 35% 27% 6%	635
	21st to end	Night	23% 13% 36% 23% 5% 1	693
April	1st to 10th	Night	20% 15% 37% 25% 4	603
	11th to 20th	Night	22% 14% 29% 27% 7% 1	593
	21st to end	Night	22% 10% 32% 28% 8% 1	600
May	1st to 10th	Night	17% 9% 35% 31% 7% 1	600
	11th to 20th	Night	18% 7% 32% 30% 12%	591
	21st to end	Night	14% 6% 29% 35% 15% 1	650
June	1st to 10th	Night	10% 5% 27% 45% 13% 1	600
	11th to 20th	Night	13% 4 30% 41% 12% 1	600
	21st to end	Night	13% 3 28% 41% 14% 1	600
July	1st to 10th	Night	9% 2 15% 41% 29% 4	585
	11th to 20th	Night	7% 3 22% 41% 25% 2	582
	21st to end	Night	7% 3 19% 45% 25% 2	657
August	1st to 10th	Night	7% 2 17% 45% 28% 2	597
	11th to 20th	Night	8% 3 14% 41% 29% 4	594
	21st to end	Night	10% 2 17% 45% 22% 3	660
September	1st to 10th	Night	11% 4 20% 38% 23% 4	600
	11th to 20th	Night	11% 3 20% 35% 27% 4	600
	21st to end	Night	11% 8% 26% 34% 20% 1	790
October	1st to 10th	Night	15% 7% 28% 31% 18% 2	800
	11th to 20th	Night	21% 12% 33% 27% 8%	800
	21st to end	Night	23% 11% 33% 27% 6%	880
November	1st to 10th	Night	16% 12% 38% 24% 9%	820
	11th to 20th	Night	19% 17% 36% 23% 5%	909
	21st to end	Night	21% 14% 36% 22% 7%	1050
December	1st to 10th	Night	20% 14% 38% 23% 5%	1050
	11th to 20th	Night	22% 13% 36% 24% 5%	1050
	21st to end	Night	27% 14% 35% 20% 3	1155

Page generated at 2026-03-30 01:18:41. Version ac07

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