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 2025-07-06.

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% 11% 4 10% 6% 5% 4 4 5% 7% 32%	119444
	Night	13% 12% 5% 12% 6% 5% 5% 4 5% 6% 29%	119456
Transparency	Day	32% 42% 7% 12% 6% 1	122931
	Night	36% 41% 7% 11% 5% 1	124129
Seeing	Day	18% 15% 34% 23% 8% 2	16793
	Night	19% 14% 33% 25% 9% 1	26819

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	7% 14% 11% 24% 9% 5% 4 3 4 7% 11%	3617
	11th to 20th	Day	8% 14% 7% 20% 13% 7% 7% 5% 6% 5% 10%	3589
	21st to end	Day	7% 16% 8% 17% 9% 6% 5% 4 5% 4 19%	3982
February	1st to 10th	Day	9% 13% 4 14% 10% 7% 6% 3 5% 6% 21%	1654
	11th to 20th	Day	9% 12% 4 13% 9% 9% 7% 5% 6% 5% 21%	1897
	21st to end	Day	11% 12% 6% 14% 8% 6% 6% 4 6% 6% 20%	1650
March	1st to 10th	Day	12% 11% 5% 9% 7% 5% 5% 4 5% 6% 32%	4478
	11th to 20th	Day	10% 13% 6% 16% 8% 5% 4 4 5% 5% 23%	4651
	21st to end	Day	18% 14% 7% 12% 7% 5% 4 3 5% 4 18%	5961
April	1st to 10th	Day	14% 13% 4 9% 6% 4 5% 4 5% 7% 28%	2400
	11th to 20th	Day	19% 13% 4 9% 5% 4 4 3 5% 5% 30%	2418
	21st to end	Day	15% 11% 3 7% 5% 5% 6% 5% 5% 7% 32%	2600
May	1st to 10th	Day	14% 8% 2 6% 3 3 3 3 4 6% 48%	6115
	11th to 20th	Day	12% 9% 2 6% 4 4 4 3 5% 7% 44%	6319
	21st to end	Day	10% 9% 3 8% 5% 5% 5% 4 6% 8% 40%	6949
June	1st to 10th	Day	11% 8% 2 7% 5% 4 5% 4 6% 9% 39%	2800
	11th to 20th	Day	15% 6% 2 8% 4 4 5% 4 8% 7% 37%	2800
	21st to end	Day	15% 6% 2 7% 5% 4 5% 5% 6% 9% 38%	2800
July	1st to 10th	Day	11% 5% 3 7% 5% 5% 4 4 6% 10% 39%	4511
	11th to 20th	Day	8% 5% 2 5% 4 4 4 3 6% 10% 49%	4440
	21st to end	Day	10% 5% 1 4 3 3 4 3 7% 8% 52%	4814
August	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 5% 7% 9% 43%	4423
	11th to 20th	Day	14% 5% 2 5% 3 3 4 3 5% 7% 49%	4117
	21st to end	Day	15% 6% 2 5% 4 3 3 3 5% 7% 47%	4214
September	1st to 10th	Day	16% 6% 2 5% 4 4 5% 4 6% 7% 42%	2280
	11th to 20th	Day	14% 5% 3 5% 5% 4 5% 4 6% 8% 41%	2152
	21st to end	Day	19% 9% 3 6% 4 4 5% 4 6% 7% 33%	2090
October	1st to 10th	Day	18% 10% 3 6% 5% 5% 5% 5% 5% 7% 32%	2028
	11th to 20th	Day	23% 14% 3 9% 5% 4 6% 4 6% 6% 20%	1786
	21st to end	Day	20% 20% 5% 9% 6% 4 4 4 4 5% 18%	1881
November	1st to 10th	Day	17% 16% 4 9% 5% 4 3 4 5% 6% 26%	1762
	11th to 20th	Day	15% 17% 7% 12% 8% 5% 5% 3 6% 5% 18%	1750
	21st to end	Day	15% 21% 7% 15% 6% 4 4 3 4 5% 15%	1600
December	1st to 10th	Day	9% 22% 10% 23% 6% 5% 5% 3 3 4 11%	2285
	11th to 20th	Day	9% 20% 9% 22% 8% 5% 4 3 4 4 12%	2649
	21st to end	Day	16% 22% 10% 20% 6% 5% 4 3 3 3 9%	3982
January	1st to 10th	Night	9% 16% 9% 25% 10% 6% 3 2 3 3 14%	6348
	11th to 20th	Night	8% 16% 7% 20% 10% 9% 7% 4 4 5% 11%	6316
	21st to end	Night	8% 13% 7% 15% 8% 6% 5% 5% 7% 7% 20%	6996
February	1st to 10th	Night	8% 14% 6% 12% 10% 7% 7% 4 5% 5% 21%	2745
	11th to 20th	Night	9% 13% 5% 14% 9% 6% 5% 5% 5% 6% 22%	2388
	21st to end	Night	13% 15% 5% 12% 8% 6% 5% 3 4 6% 23%	1980
March	1st to 10th	Night	11% 9% 4 10% 7% 5% 5% 4 6% 8% 31%	5362
	11th to 20th	Night	11% 12% 6% 12% 5% 5% 5% 4 5% 7% 28%	5307
	21st to end	Night	20% 12% 5% 12% 7% 4 5% 3 5% 5% 22%	5013
April	1st to 10th	Night	17% 15% 3 9% 5% 5% 4 5% 5% 5% 27%	2000
	11th to 20th	Night	22% 9% 4 6% 4 3 3 4 5% 5% 35%	1931
	21st to end	Night	16% 12% 3 8% 5% 4 4 3 4 6% 35%	1800
May	1st to 10th	Night	14% 8% 3 6% 3 3 3 3 4 6% 48%	3833
	11th to 20th	Night	13% 8% 3 6% 4 4 4 3 5% 7% 43%	3596
	21st to end	Night	16% 9% 3 7% 4 5% 5% 4 5% 7% 36%	3949
June	1st to 10th	Night	13% 6% 2 7% 5% 5% 4 4 5% 7% 42%	1600
	11th to 20th	Night	14% 7% 3 7% 5% 4 6% 5% 6% 8% 36%	1513
	21st to end	Night	16% 6% 3 7% 4 3 5% 4 6% 8% 39%	1600
July	1st to 10th	Night	11% 6% 3 8% 5% 5% 4 3 6% 7% 41%	2570
	11th to 20th	Night	7% 4 1 4 4 4 4 3 5% 8% 55%	2530
	21st to end	Night	10% 4 2 5% 4 3 3 2 5% 8% 54%	2750
August	1st to 10th	Night	10% 7% 2 7% 4 4 4 3 6% 6% 47%	2517
	11th to 20th	Night	15% 5% 2 5% 4 3 4 3 4 8% 49%	2714
	21st to end	Night	14% 6% 3 7% 4 3 4 3 4 6% 46%	3439
September	1st to 10th	Night	13% 5% 2 4 4 4 3 3 5% 8% 47%	1900
	11th to 20th	Night	13% 6% 2 6% 5% 4 5% 4 5% 6% 44%	2009
	21st to end	Night	18% 7% 2 6% 4 4 5% 4 5% 7% 37%	2090
October	1st to 10th	Night	18% 7% 2 7% 4 4 4 4 6% 7% 37%	2151
	11th to 20th	Night	18% 12% 3 7% 5% 5% 4 4 5% 7% 30%	2394
	21st to end	Night	20% 17% 4 9% 6% 4 4 4 5% 5% 22%	2717
November	1st to 10th	Night	15% 16% 4 8% 5% 6% 4 4 6% 7% 27%	2536
	11th to 20th	Night	16% 18% 7% 12% 6% 5% 4 3 4 4 21%	2645
	21st to end	Night	16% 17% 8% 14% 7% 4 4 3 5% 5% 17%	2800
December	1st to 10th	Night	12% 16% 9% 16% 8% 6% 6% 5% 5% 5% 13%	4898
	11th to 20th	Night	10% 15% 7% 20% 9% 6% 5% 4 4 5% 15%	5523
	21st to end	Night	17% 20% 11% 18% 6% 4 4 3 3 3 13%	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	58% 29% 9% 4	3618
	11th to 20th	Day	56% 31% 5% 8%	3620
	21st to end	Day	50% 31% 8% 7% 4	3982
February	1st to 10th	Day	24% 65% 5% 4 3	1654
	11th to 20th	Day	26% 63% 4 5% 2	1907
	21st to end	Day	23% 63% 4 7% 3	1650
March	1st to 10th	Day	34% 30% 12% 14% 8% 2	4480
	11th to 20th	Day	48% 31% 9% 9% 3	4651
	21st to end	Day	51% 30% 6% 8% 4	5961
April	1st to 10th	Day	23% 63% 5% 7% 3	2400
	11th to 20th	Day	21% 63% 3 9% 3 1	2418
	21st to end	Day	19% 62% 4 9% 5%	2600
May	1st to 10th	Day	25% 29% 7% 22% 14% 2	6124
	11th to 20th	Day	27% 32% 8% 21% 9% 3	6323
	21st to end	Day	32% 31% 8% 15% 12% 1	6949
June	1st to 10th	Day	16% 63% 5% 9% 5% 1	2800
	11th to 20th	Day	19% 63% 6% 7% 5%	2800
	21st to end	Day	17% 62% 6% 10% 5% 1	2800
July	1st to 10th	Day	29% 41% 9% 13% 7% 1	4442
	11th to 20th	Day	19% 39% 10% 22% 9% 1	4365
	21st to end	Day	17% 39% 7% 25% 12%	4662
August	1st to 10th	Day	24% 40% 12% 19% 6%	4408
	11th to 20th	Day	24% 39% 10% 22% 5%	4157
	21st to end	Day	24% 39% 11% 17% 9%	4213
September	1st to 10th	Day	19% 62% 4 11% 4	2280
	11th to 20th	Day	14% 63% 9% 10% 4	2152
	21st to end	Day	19% 62% 7% 11% 2	2090
October	1st to 10th	Day	20% 39% 10% 20% 10%	3366
	11th to 20th	Day	36% 38% 7% 10% 9%	2950
	21st to end	Day	40% 39% 10% 9% 3	3081
November	1st to 10th	Day	28% 57% 6% 6% 2	1762
	11th to 20th	Day	30% 58% 5% 5% 2	1750
	21st to end	Day	33% 59% 4 2 1	1600
December	1st to 10th	Day	55% 37% 5% 3 1	2285
	11th to 20th	Day	56% 33% 6% 4 1	2649
	21st to end	Day	63% 29% 2 4 2	3982
January	1st to 10th	Night	61% 27% 4 7% 1	6348
	11th to 20th	Night	56% 31% 6% 5% 1	6360
	21st to end	Night	45% 33% 14% 7% 2	6996
February	1st to 10th	Night	26% 62% 4 6% 2	2745
	11th to 20th	Night	25% 61% 4 7% 3	2389
	21st to end	Night	21% 63% 5% 8% 3	1980
March	1st to 10th	Night	34% 31% 17% 12% 5%	5373
	11th to 20th	Night	41% 30% 12% 12% 5%	5308
	21st to end	Night	46% 31% 7% 11% 5%	5013
April	1st to 10th	Night	22% 63% 4 6% 4 1	2000
	11th to 20th	Night	20% 63% 4 9% 4 1	1931
	21st to end	Night	20% 62% 3 9% 6% 1	1800
May	1st to 10th	Night	24% 30% 9% 23% 12% 3	3840
	11th to 20th	Night	27% 33% 8% 18% 11% 3	3597
	21st to end	Night	36% 31% 6% 14% 10% 3	3950
June	1st to 10th	Night	18% 62% 4 10% 6%	1600
	11th to 20th	Night	20% 63% 5% 8% 3 1	1513
	21st to end	Night	18% 61% 6% 9% 6%	1600
July	1st to 10th	Night	31% 38% 10% 12% 6% 2	2530
	11th to 20th	Night	15% 38% 9% 30% 7% 1	2482
	21st to end	Night	21% 37% 6% 17% 19% 1	2662
August	1st to 10th	Night	25% 39% 7% 19% 9%	2508
	11th to 20th	Night	26% 39% 10% 21% 5%	2740
	21st to end	Night	29% 39% 8% 14% 10% 1	3439
September	1st to 10th	Night	16% 61% 6% 12% 4	1900
	11th to 20th	Night	18% 62% 6% 11% 3	2009
	21st to end	Night	18% 61% 7% 11% 2 1	2090
October	1st to 10th	Night	23% 38% 9% 20% 9%	3593
	11th to 20th	Night	28% 38% 8% 16% 10%	3969
	21st to end	Night	36% 39% 9% 14% 2	4467
November	1st to 10th	Night	29% 57% 5% 7% 2	2536
	11th to 20th	Night	29% 58% 6% 5% 2	2645
	21st to end	Night	35% 58% 3 3 1	2800
December	1st to 10th	Night	52% 38% 5% 3 1	4898
	11th to 20th	Night	51% 35% 6% 6% 1	5522
	21st to end	Night	60% 28% 4 5% 3	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	18% 16% 40% 23% 3	300
	11th to 20th	Day	18% 16% 44% 18% 3 1	300
	21st to end	Day	18% 15% 43% 20% 4	330
February	1st to 10th	Day	21% 19% 39% 16% 5%	300
	11th to 20th	Day	14% 26% 44% 14% 2	300
	21st to end	Day	24% 23% 38% 14%	249
March	1st to 10th	Day	16% 24% 42% 14% 4	300
	11th to 20th	Day	21% 22% 35% 17% 5% 1	353
	21st to end	Day	26% 20% 31% 16% 6%	550
April	1st to 10th	Day	25% 15% 35% 19% 4 1	500
	11th to 20th	Day	26% 19% 28% 20% 7% 1	492
	21st to end	Day	22% 20% 28% 22% 7% 2	500
May	1st to 10th	Day	19% 18% 34% 21% 7% 2	600
	11th to 20th	Day	18% 14% 38% 22% 6% 2	725
	21st to end	Day	15% 13% 35% 25% 8% 3	789
June	1st to 10th	Day	14% 15% 34% 27% 8% 3	730
	11th to 20th	Day	15% 13% 36% 25% 9% 2	730
	21st to end	Day	18% 9% 33% 28% 9% 3	730
July	1st to 10th	Day	7% 8% 34% 34% 12% 5%	697
	11th to 20th	Day	11% 9% 32% 32% 13% 3	668
	21st to end	Day	9% 8% 33% 32% 15% 5%	739
August	1st to 10th	Day	11% 9% 33% 32% 13% 3	676
	11th to 20th	Day	14% 9% 23% 28% 22% 5%	528
	21st to end	Day	19% 11% 27% 25% 13% 4	539
September	1st to 10th	Day	19% 11% 31% 23% 12% 4	490
	11th to 20th	Day	12% 11% 32% 30% 11% 2	490
	21st to end	Day	21% 13% 27% 26% 11% 1	490
October	1st to 10th	Day	26% 15% 29% 20% 8% 1	428
	11th to 20th	Day	27% 24% 36% 12% 2	300
	21st to end	Day	32% 22% 35% 10% 2	330
November	1st to 10th	Day	22% 23% 33% 18% 3	300
	11th to 20th	Day	23% 27% 37% 10% 3	300
	21st to end	Day	23% 26% 34% 15% 1	300
December	1st to 10th	Day	18% 20% 37% 19% 6%	203
	11th to 20th	Day	26% 25% 35% 12% 3	207
	21st to end	Day	24% 24% 37% 12% 3	330
January	1st to 10th	Night	17% 19% 43% 18% 3	1000
	11th to 20th	Night	18% 20% 41% 17% 4 1	1000
	21st to end	Night	17% 16% 38% 22% 5% 1	1100
February	1st to 10th	Night	17% 18% 39% 20% 6%	1000
	11th to 20th	Night	16% 19% 38% 21% 6%	833
	21st to end	Night	19% 16% 43% 18% 4	660
March	1st to 10th	Night	15% 15% 37% 25% 7% 1	800
	11th to 20th	Night	17% 20% 35% 22% 5% 1	800
	21st to end	Night	22% 12% 32% 25% 8% 1	685
April	1st to 10th	Night	24% 15% 31% 25% 6% 1	600
	11th to 20th	Night	26% 12% 28% 25% 8% 1	593
	21st to end	Night	20% 11% 31% 28% 9% 1	600
May	1st to 10th	Night	19% 11% 25% 32% 11% 2	600
	11th to 20th	Night	19% 10% 27% 32% 10% 2	591
	21st to end	Night	16% 8% 28% 34% 13%	650
June	1st to 10th	Night	14% 8% 27% 36% 13% 1	600
	11th to 20th	Night	17% 6% 27% 37% 12%	513
	21st to end	Night	17% 8% 28% 33% 12% 3	600
July	1st to 10th	Night	11% 3 26% 38% 20% 2	570
	11th to 20th	Night	12% 4 31% 35% 17% 1	552
	21st to end	Night	9% 4 30% 36% 18% 4	624
August	1st to 10th	Night	11% 4 30% 35% 19% 1	567
	11th to 20th	Night	12% 3 21% 36% 26% 4	564
	21st to end	Night	15% 7% 29% 31% 17% 1	627
September	1st to 10th	Night	16% 5% 26% 31% 18% 3	570
	11th to 20th	Night	15% 8% 32% 33% 11%	679
	21st to end	Night	21% 8% 27% 32% 11% 1	760
October	1st to 10th	Night	22% 12% 33% 23% 9% 2	760
	11th to 20th	Night	23% 16% 35% 20% 6%	760
	21st to end	Night	30% 15% 32% 18% 5% 1	836
November	1st to 10th	Night	23% 17% 37% 19% 4	780
	11th to 20th	Night	23% 22% 34% 16% 4	845
	21st to end	Night	24% 19% 37% 17% 3	1000
December	1st to 10th	Night	18% 22% 40% 15% 5% 1	1000
	11th to 20th	Night	21% 19% 35% 18% 6% 2	1000
	21st to end	Night	25% 19% 38% 16% 3	1100

Page generated at 2025-07-03 01:30:14. Version ac07

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