Marquette
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marquette clear sky chart from 2005-11-06 to 2026-10-29.

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% 10% 4 9% 6% 5% 5% 4 5% 7% 34%	149464
	Night	12% 11% 5% 11% 6% 5% 5% 4 5% 6% 30%	142858
Transparency	Day	34% 35% 9% 16% 7% 1	152906
	Night	38% 35% 8% 13% 5% 1	147503
Seeing	Day	18% 16% 34% 22% 8% 2	18649
	Night	19% 14% 34% 25% 8% 1	28574

By Month

Percentage Cloud Cover NE (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% 15% 10% 21% 9% 5% 4 3 4 8% 13%	4691
	11th to 20th	Day	7% 17% 7% 20% 12% 6% 7% 4 5% 4 10%	4679
	21st to end	Day	6% 12% 7% 15% 10% 7% 6% 6% 6% 6% 19%	5156
February	1st to 10th	Day	9% 13% 4 14% 10% 7% 6% 4 5% 6% 21%	1737
	11th to 20th	Day	9% 12% 4 13% 9% 9% 7% 4 5% 5% 22%	1995
	21st to end	Day	11% 13% 6% 13% 9% 6% 6% 4 6% 6% 20%	1730
March	1st to 10th	Day	12% 11% 5% 9% 7% 5% 5% 4 5% 6% 32%	4578
	11th to 20th	Day	11% 13% 6% 16% 8% 5% 4 4 5% 5% 23%	4754
	21st to end	Day	18% 15% 7% 13% 7% 5% 4 3 5% 4 18%	6093
April	1st to 10th	Day	15% 13% 5% 10% 6% 4 5% 4 5% 7% 28%	2520
	11th to 20th	Day	18% 13% 4 10% 5% 4 4 3 5% 5% 29%	2540
	21st to end	Day	15% 11% 3 7% 5% 4 5% 5% 5% 7% 32%	2730
May	1st to 10th	Day	11% 8% 2 7% 4 4 4 3 5% 7% 45%	7938
	11th to 20th	Day	13% 9% 2 6% 4 4 3 3 5% 6% 45%	8222
	21st to end	Day	9% 7% 2 7% 5% 4 4 3 5% 7% 46%	9061
June	1st to 10th	Day	11% 8% 2 7% 5% 5% 5% 4 6% 9% 38%	2940
	11th to 20th	Day	14% 6% 2 8% 4 4 5% 4 7% 7% 37%	2940
	21st to end	Day	15% 6% 2 7% 5% 4 5% 5% 6% 9% 38%	2940
July	1st to 10th	Day	10% 4 2 6% 4 4 4 4 7% 13% 41%	8279
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 9% 46%	8280
	21st to end	Day	10% 6% 2 5% 4 3 4 3 6% 8% 48%	8992
August	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 46%	6483
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 3 6% 9% 45%	6069
	21st to end	Day	14% 7% 3 6% 4 4 4 4 5% 7% 41%	6128
September	1st to 10th	Day	16% 6% 2 5% 4 4 5% 4 6% 7% 42%	2520
	11th to 20th	Day	13% 6% 3 5% 5% 5% 5% 4 6% 9% 39%	2378
	21st to end	Day	18% 8% 2 6% 4 4 5% 4 6% 7% 35%	2310
October	1st to 10th	Day	17% 10% 3 6% 5% 4 5% 5% 6% 7% 33%	2241
	11th to 20th	Day	22% 14% 3 9% 5% 4 6% 4 5% 6% 22%	1974
	21st to end	Day	20% 19% 5% 9% 6% 4 4 4 4 6% 19%	2052
November	1st to 10th	Day	16% 16% 5% 9% 5% 4 4 4 6% 6% 26%	1852
	11th to 20th	Day	15% 17% 7% 12% 7% 5% 5% 3 6% 5% 18%	1837
	21st to end	Day	16% 20% 7% 15% 6% 4 4 3 4 5% 15%	1680
December	1st to 10th	Day	8% 21% 10% 23% 6% 6% 5% 3 3 4 11%	2355
	11th to 20th	Day	9% 19% 9% 23% 8% 5% 4 3 4 4 12%	2720
	21st to end	Day	16% 22% 10% 20% 6% 5% 4 3 3 3 9%	4070
January	1st to 10th	Night	10% 15% 9% 24% 11% 5% 3 3 3 4 13%	8233
	11th to 20th	Night	7% 18% 7% 23% 9% 8% 7% 3 4 4 9%	8236
	21st to end	Night	6% 10% 6% 14% 9% 7% 6% 6% 8% 8% 20%	9058
February	1st to 10th	Night	8% 15% 6% 12% 9% 7% 7% 4 5% 5% 21%	2882
	11th to 20th	Night	9% 13% 5% 14% 9% 6% 5% 5% 5% 6% 23%	2510
	21st to end	Night	13% 15% 5% 12% 8% 6% 5% 4 4 6% 22%	2076
March	1st to 10th	Night	11% 9% 4 10% 7% 5% 5% 4 6% 8% 31%	5482
	11th to 20th	Night	11% 12% 5% 12% 5% 5% 5% 4 5% 7% 28%	5424
	21st to end	Night	20% 12% 5% 12% 7% 4 5% 3 5% 5% 22%	5124
April	1st to 10th	Night	17% 14% 3 10% 5% 4 4 5% 5% 5% 27%	2100
	11th to 20th	Night	22% 9% 4 6% 4 3 3 4 5% 5% 34%	2029
	21st to end	Night	15% 11% 3 8% 5% 4 5% 3 5% 6% 35%	1890
May	1st to 10th	Night	11% 7% 2 5% 3 3 3 3 4 7% 50%	4973
	11th to 20th	Night	15% 10% 3 6% 4 4 4 3 5% 6% 41%	4670
	21st to end	Night	13% 7% 2 7% 4 4 4 3 5% 7% 42%	5148
June	1st to 10th	Night	13% 6% 3 7% 5% 5% 4 4 4 7% 42%	1680
	11th to 20th	Night	14% 7% 3 6% 5% 4 6% 5% 6% 8% 36%	1589
	21st to end	Night	16% 6% 3 6% 4 3 5% 4 6% 8% 39%	1680
July	1st to 10th	Night	10% 6% 2 7% 4 5% 4 4 6% 9% 43%	4710
	11th to 20th	Night	10% 4 2 5% 4 3 4 3 5% 9% 51%	4710
	21st to end	Night	7% 4 2 5% 4 3 3 3 6% 9% 53%	5118
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 47%	3687
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 4 9% 50%	3982
	21st to end	Night	15% 7% 3 7% 4 4 5% 4 5% 6% 40%	4995
September	1st to 10th	Night	13% 6% 2 4 4 4 4 3 5% 8% 46%	2100
	11th to 20th	Night	12% 6% 3 7% 5% 5% 5% 4 5% 5% 43%	2221
	21st to end	Night	17% 7% 2 6% 4 4 5% 4 5% 7% 38%	2310
October	1st to 10th	Night	17% 7% 2 7% 4 4 4 4 6% 7% 38%	2377
	11th to 20th	Night	18% 12% 3 7% 5% 5% 4 3 5% 6% 30%	2646
	21st to end	Night	19% 16% 4 9% 6% 4 4 4 5% 5% 24%	2965
November	1st to 10th	Night	15% 17% 4 8% 5% 6% 4 4 6% 7% 26%	2666
	11th to 20th	Night	15% 18% 7% 12% 6% 5% 4 3 4 5% 21%	2777
	21st to end	Night	16% 17% 8% 14% 7% 4 4 3 5% 5% 17%	2940
December	1st to 10th	Night	12% 15% 9% 16% 8% 6% 6% 5% 5% 5% 14%	5048
	11th to 20th	Night	10% 15% 7% 20% 9% 6% 5% 4 4 5% 15%	5672
	21st to end	Night	17% 19% 11% 18% 6% 4 4 2 3 3 13%	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	59% 25% 12% 3	4692
	11th to 20th	Day	63% 24% 5% 8%	4710
	21st to end	Day	50% 26% 9% 11% 4	5156
February	1st to 10th	Day	24% 62% 5% 6% 3	1737
	11th to 20th	Day	27% 60% 4 6% 3	2005
	21st to end	Day	25% 60% 4 7% 3	1730
March	1st to 10th	Day	34% 30% 12% 14% 8% 2	4580
	11th to 20th	Day	48% 30% 9% 9% 3 1	4754
	21st to end	Day	52% 29% 6% 8% 4	6093
April	1st to 10th	Day	25% 60% 5% 7% 3	2520
	11th to 20th	Day	22% 60% 4 9% 3 1	2540
	21st to end	Day	21% 60% 5% 10% 5%	2730
May	1st to 10th	Day	27% 24% 8% 26% 13% 1	7947
	11th to 20th	Day	30% 26% 7% 24% 11% 2	8226
	21st to end	Day	29% 25% 8% 21% 16% 2	9061
June	1st to 10th	Day	18% 60% 6% 9% 6% 1	2940
	11th to 20th	Day	20% 60% 6% 9% 5%	2940
	21st to end	Day	18% 59% 6% 11% 5% 1	2940
July	1st to 10th	Day	29% 28% 13% 22% 8% 1	8211
	11th to 20th	Day	28% 24% 13% 26% 8%	8205
	21st to end	Day	27% 24% 10% 28% 11%	8794
August	1st to 10th	Day	27% 29% 13% 25% 6%	6468
	11th to 20th	Day	26% 31% 17% 22% 3	6109
	21st to end	Day	32% 30% 12% 20% 6%	6127
September	1st to 10th	Day	21% 56% 6% 12% 4	2520
	11th to 20th	Day	17% 58% 10% 11% 4	2378
	21st to end	Day	20% 57% 7% 12% 5%	2310
October	1st to 10th	Day	21% 37% 11% 21% 10%	3579
	11th to 20th	Day	37% 36% 7% 11% 10%	3138
	21st to end	Day	41% 38% 10% 10% 2	3252
November	1st to 10th	Day	30% 55% 6% 6% 2	1852
	11th to 20th	Day	31% 56% 5% 6% 2	1837
	21st to end	Day	35% 57% 4 2 2	1680
December	1st to 10th	Day	55% 36% 5% 3 1	2355
	11th to 20th	Day	57% 32% 6% 4 1	2720
	21st to end	Day	63% 28% 2 4 2	4070
January	1st to 10th	Night	65% 23% 6% 5% 1	8233
	11th to 20th	Night	65% 25% 6% 4 1	8280
	21st to end	Night	47% 28% 13% 9% 3	9058
February	1st to 10th	Night	27% 59% 5% 6% 3	2882
	11th to 20th	Night	26% 59% 5% 8% 3	2511
	21st to end	Night	24% 60% 5% 9% 3	2076
March	1st to 10th	Night	35% 31% 17% 12% 5%	5493
	11th to 20th	Night	42% 29% 12% 12% 5%	5425
	21st to end	Night	47% 30% 8% 10% 5%	5124
April	1st to 10th	Night	25% 60% 4 7% 4 1	2100
	11th to 20th	Night	22% 60% 4 9% 4 1	2029
	21st to end	Night	21% 59% 4 9% 6% 1	1890
May	1st to 10th	Night	24% 24% 8% 31% 12% 2	4980
	11th to 20th	Night	33% 26% 7% 23% 10% 2	4671
	21st to end	Night	33% 25% 7% 19% 14% 3	5149
June	1st to 10th	Night	19% 60% 4 10% 8%	1680
	11th to 20th	Night	21% 61% 5% 9% 4 1	1589
	21st to end	Night	19% 59% 6% 10% 6%	1680
July	1st to 10th	Night	32% 24% 14% 19% 8% 3	4670
	11th to 20th	Night	25% 22% 13% 30% 9%	4662
	21st to end	Night	24% 23% 13% 25% 15% 1	5002
August	1st to 10th	Night	30% 28% 10% 22% 10%	3678
	11th to 20th	Night	27% 29% 15% 24% 5%	4008
	21st to end	Night	37% 29% 8% 18% 7%	4995
September	1st to 10th	Night	19% 56% 7% 13% 5%	2100
	11th to 20th	Night	21% 57% 6% 12% 4	2221
	21st to end	Night	20% 56% 7% 11% 5% 1	2310
October	1st to 10th	Night	24% 36% 10% 21% 9%	3819
	11th to 20th	Night	29% 36% 8% 16% 10%	4221
	21st to end	Night	36% 38% 9% 15% 3	4715
November	1st to 10th	Night	31% 55% 5% 7% 2	2666
	11th to 20th	Night	30% 56% 6% 5% 2	2777
	21st to end	Night	37% 56% 3 3 1	2940
December	1st to 10th	Night	53% 38% 6% 3 1	5048
	11th to 20th	Night	52% 35% 6% 6% 1	5671
	21st to end	Night	60% 27% 4 5% 3	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	19% 17% 39% 22% 3	330
	11th to 20th	Day	18% 17% 44% 17% 3 1	330
	21st to end	Day	17% 17% 43% 19% 4	363
February	1st to 10th	Day	21% 20% 40% 15% 4	330
	11th to 20th	Day	15% 25% 44% 13% 3	330
	21st to end	Day	25% 23% 38% 13%	273
March	1st to 10th	Day	19% 24% 40% 13% 4	330
	11th to 20th	Day	23% 22% 34% 16% 4 1	386
	21st to end	Day	27% 21% 31% 15% 6%	594
April	1st to 10th	Day	26% 17% 34% 19% 4 1	540
	11th to 20th	Day	26% 18% 29% 20% 6% 1	532
	21st to end	Day	22% 19% 30% 21% 6% 2	540
May	1st to 10th	Day	19% 18% 34% 21% 7% 2	645
	11th to 20th	Day	19% 15% 37% 21% 5% 2	775
	21st to end	Day	15% 14% 35% 26% 8% 3	844
June	1st to 10th	Day	13% 15% 34% 27% 9% 3	780
	11th to 20th	Day	16% 14% 36% 24% 9% 1	780
	21st to end	Day	18% 9% 34% 28% 9% 3	780
July	1st to 10th	Day	7% 7% 34% 35% 12% 5%	771
	11th to 20th	Day	12% 10% 33% 31% 12% 3	768
	21st to end	Day	9% 8% 35% 30% 13% 4	849
August	1st to 10th	Day	11% 9% 34% 31% 12% 3	776
	11th to 20th	Day	14% 10% 26% 26% 20% 4	614
	21st to end	Day	19% 11% 28% 25% 13% 4	627
September	1st to 10th	Day	20% 12% 31% 22% 11% 4	570
	11th to 20th	Day	13% 13% 32% 29% 11% 2	570
	21st to end	Day	20% 12% 28% 27% 12% 1	570
October	1st to 10th	Day	24% 16% 32% 20% 7% 1	501
	11th to 20th	Day	27% 24% 36% 11% 2	360
	21st to end	Day	29% 20% 36% 12% 2	387
November	1st to 10th	Day	23% 24% 34% 17% 3	330
	11th to 20th	Day	23% 28% 35% 11% 3	330
	21st to end	Day	25% 25% 34% 14% 1	330
December	1st to 10th	Day	17% 23% 36% 18% 5%	223
	11th to 20th	Day	27% 26% 33% 11% 3	228
	21st to end	Day	26% 23% 37% 12% 3	363
January	1st to 10th	Night	17% 20% 42% 18% 3	1050
	11th to 20th	Night	19% 20% 40% 16% 4 1	1050
	21st to end	Night	17% 17% 39% 22% 5% 1	1155
February	1st to 10th	Night	17% 18% 38% 20% 6%	1050
	11th to 20th	Night	16% 19% 39% 21% 6%	875
	21st to end	Night	20% 15% 43% 18% 3	692
March	1st to 10th	Night	15% 15% 38% 25% 7% 1	840
	11th to 20th	Night	18% 20% 35% 21% 5% 1	840
	21st to end	Night	22% 13% 32% 24% 8% 1	719
April	1st to 10th	Night	23% 15% 31% 24% 6%	630
	11th to 20th	Night	26% 12% 29% 25% 7% 1	623
	21st to end	Night	20% 11% 32% 28% 9% 1	630
May	1st to 10th	Night	18% 11% 25% 32% 11% 2	630
	11th to 20th	Night	19% 11% 28% 31% 10% 2	621
	21st to end	Night	16% 8% 29% 35% 12%	683
June	1st to 10th	Night	14% 7% 27% 37% 14% 1	630
	11th to 20th	Night	17% 8% 27% 37% 11%	539
	21st to end	Night	17% 7% 28% 33% 12% 3	630
July	1st to 10th	Night	11% 3 26% 38% 20% 2	615
	11th to 20th	Night	12% 4 31% 36% 16% 1	612
	21st to end	Night	8% 4 32% 36% 16% 3	690
August	1st to 10th	Night	11% 4 31% 35% 18% 1	627
	11th to 20th	Night	11% 3 22% 36% 24% 3	624
	21st to end	Night	15% 7% 29% 31% 17% 1	693
September	1st to 10th	Night	16% 7% 26% 30% 18% 3	630
	11th to 20th	Night	15% 9% 31% 33% 11% 1	751
	21st to end	Night	20% 7% 27% 33% 12% 1	840
October	1st to 10th	Night	21% 14% 33% 22% 9% 2	840
	11th to 20th	Night	23% 16% 35% 19% 6%	840
	21st to end	Night	28% 15% 31% 19% 6% 1	913
November	1st to 10th	Night	24% 18% 36% 19% 3	820
	11th to 20th	Night	23% 23% 34% 16% 4	887
	21st to end	Night	24% 20% 37% 17% 3	1050
December	1st to 10th	Night	18% 22% 40% 16% 4 1	1050
	11th to 20th	Night	22% 19% 34% 18% 6% 1	1050
	21st to end	Night	25% 19% 37% 16% 3	1155

Page generated at 2026-10-26 04:37:51. Version ac07

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