Maple Plains
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maple Plains clear sky chart from 2005-11-06 to 2026-03-18.

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	17% 11% 4 9% 5% 5% 5% 4 5% 7% 30%	131854
	Night	18% 12% 4 9% 5% 5% 4 3 5% 6% 28%	129784
Transparency	Day	34% 39% 9% 13% 5%	135390
	Night	36% 38% 8% 11% 6%	134338
Seeing	Day	22% 11% 29% 26% 10% 2	18980
	Night	24% 12% 30% 26% 8% 1	26449

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	12% 20% 9% 15% 6% 7% 5% 4 4 5% 15%	4187
	11th to 20th	Day	17% 15% 8% 14% 6% 4 4 3 3 4 21%	4681
	21st to end	Day	9% 9% 3 11% 5% 5% 6% 4 6% 7% 34%	5702
February	1st to 10th	Day	16% 12% 5% 10% 5% 5% 4 4 5% 5% 29%	1890
	11th to 20th	Day	15% 15% 4 10% 6% 5% 5% 3 4 5% 29%	1843
	21st to end	Day	11% 11% 5% 9% 6% 5% 4 3 6% 7% 33%	1585
March	1st to 10th	Day	20% 12% 4 10% 5% 7% 3 3 4 6% 26%	4935
	11th to 20th	Day	14% 13% 6% 11% 6% 5% 5% 4 6% 7% 24%	5057
	21st to end	Day	23% 15% 5% 11% 6% 4 4 3 5% 5% 20%	5510
April	1st to 10th	Day	20% 13% 4 8% 5% 4 4 3 4 6% 30%	2400
	11th to 20th	Day	19% 12% 3 6% 5% 4 4 3 5% 7% 33%	2454
	21st to end	Day	20% 12% 4 7% 4 4 5% 4 5% 6% 30%	2600
May	1st to 10th	Day	25% 14% 3 8% 4 4 4 3 4 5% 27%	6202
	11th to 20th	Day	18% 11% 3 7% 5% 5% 4 3 4 6% 33%	6318
	21st to end	Day	18% 10% 3 8% 5% 4 4 4 5% 7% 32%	6948
June	1st to 10th	Day	24% 11% 3 7% 5% 4 5% 4 6% 6% 26%	2849
	11th to 20th	Day	19% 9% 3 6% 5% 4 4 3 5% 7% 35%	3000
	21st to end	Day	24% 10% 3 7% 4 3 4 3 5% 6% 31%	3000
July	1st to 10th	Day	16% 10% 3 8% 5% 5% 5% 4 7% 8% 29%	6820
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 6% 8% 42%	6465
	21st to end	Day	12% 6% 2 6% 4 4 5% 4 7% 9% 38%	6927
August	1st to 10th	Day	17% 9% 3 8% 5% 4 5% 4 6% 7% 33%	4251
	11th to 20th	Day	13% 7% 2 6% 4 5% 5% 5% 6% 9% 39%	4175
	21st to end	Day	11% 5% 2 4 4 4 5% 4 7% 8% 44%	4492
September	1st to 10th	Day	16% 5% 2 5% 4 4 4 4 6% 8% 41%	2400
	11th to 20th	Day	17% 8% 2 7% 4 4 4 4 4 7% 39%	2359
	21st to end	Day	17% 7% 2 6% 4 5% 4 3 5% 7% 40%	2115
October	1st to 10th	Day	18% 8% 3 6% 5% 5% 4 4 6% 8% 35%	2000
	11th to 20th	Day	19% 11% 4 9% 5% 5% 5% 4 5% 8% 26%	2000
	21st to end	Day	17% 13% 4 11% 6% 5% 5% 3 4 7% 24%	2155
November	1st to 10th	Day	20% 13% 3 8% 5% 6% 5% 4 5% 5% 25%	1667
	11th to 20th	Day	20% 18% 5% 10% 5% 5% 4 3 5% 6% 20%	1680
	21st to end	Day	18% 16% 5% 12% 6% 6% 5% 5% 5% 6% 18%	1680
December	1st to 10th	Day	17% 14% 7% 18% 5% 5% 4 3 5% 5% 17%	2690
	11th to 20th	Day	21% 13% 5% 13% 7% 5% 4 2 4 4 22%	3076
	21st to end	Day	16% 13% 6% 16% 7% 5% 5% 3 4 5% 19%	3741
January	1st to 10th	Night	13% 18% 6% 12% 6% 5% 5% 4 5% 5% 22%	8716
	11th to 20th	Night	19% 16% 7% 12% 6% 5% 4 3 4 4 22%	8234
	21st to end	Night	8% 12% 5% 10% 6% 6% 6% 4 5% 7% 32%	8480
February	1st to 10th	Night	16% 14% 5% 9% 6% 4 4 3 5% 5% 29%	2730
	11th to 20th	Night	16% 15% 4 10% 7% 5% 5% 3 5% 5% 26%	2663
	21st to end	Night	13% 13% 4 9% 6% 5% 4 4 5% 5% 32%	2220
March	1st to 10th	Night	22% 14% 4 11% 6% 4 4 3 4 5% 24%	5122
	11th to 20th	Night	20% 14% 6% 10% 5% 5% 4 3 4 5% 24%	5057
	21st to end	Night	26% 14% 5% 10% 4 4 4 3 4 3 23%	5421
April	1st to 10th	Night	22% 12% 4 9% 5% 4 3 4 5% 5% 26%	2000
	11th to 20th	Night	21% 12% 3 7% 5% 4 4 3 4 6% 31%	1893
	21st to end	Night	23% 13% 4 7% 5% 3 4 3 5% 5% 29%	1800
May	1st to 10th	Night	27% 13% 4 8% 5% 4 4 4 4 5% 23%	3750
	11th to 20th	Night	18% 8% 3 8% 5% 4 5% 3 5% 6% 34%	3596
	21st to end	Night	17% 9% 3 7% 4 4 5% 4 5% 8% 33%	3948
June	1st to 10th	Night	26% 10% 3 7% 5% 4 4 4 4 5% 29%	1566
	11th to 20th	Night	18% 8% 2 6% 4 3 4 3 5% 8% 38%	1400
	21st to end	Night	22% 11% 3 8% 5% 3 4 4 6% 6% 28%	1400
July	1st to 10th	Night	16% 9% 3 9% 6% 6% 7% 5% 7% 9% 26%	3160
	11th to 20th	Night	10% 7% 3 6% 5% 5% 5% 5% 7% 8% 38%	3454
	21st to end	Night	15% 7% 2 7% 4 4 5% 4 6% 8% 38%	3948
August	1st to 10th	Night	19% 8% 3 7% 6% 5% 5% 4 5% 7% 31%	2883
	11th to 20th	Night	10% 7% 3 7% 5% 5% 4 4 7% 8% 41%	2872
	21st to end	Night	12% 6% 2 6% 4 4 5% 3 6% 8% 44%	3406
September	1st to 10th	Night	16% 6% 2 6% 4 4 4 3 4 7% 44%	2000
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 4 6% 43%	2039
	21st to end	Night	18% 6% 2 5% 3 4 4 3 5% 7% 42%	2285
October	1st to 10th	Night	19% 7% 2 7% 4 4 4 3 5% 7% 39%	2400
	11th to 20th	Night	18% 9% 4 7% 5% 4 5% 3 5% 5% 35%	2400
	21st to end	Night	22% 12% 3 8% 5% 4 5% 3 4 5% 28%	2684
November	1st to 10th	Night	22% 12% 3 7% 5% 4 5% 4 4 6% 27%	2848
	11th to 20th	Night	21% 15% 4 9% 4 5% 4 3 5% 6% 24%	2940
	21st to end	Night	23% 16% 4 9% 5% 4 4 3 5% 6% 21%	2940
December	1st to 10th	Night	16% 12% 5% 15% 7% 5% 5% 4 7% 6% 19%	4720
	11th to 20th	Night	23% 13% 4 10% 5% 4 3 3 5% 5% 24%	5353
	21st to end	Night	21% 15% 5% 13% 5% 5% 4 4 4 5% 20%	7456

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% 26% 8% 5% 3	4188
	11th to 20th	Day	53% 25% 8% 9% 5%	4710
	21st to end	Day	37% 25% 9% 18% 10% 1	5702
February	1st to 10th	Day	25% 59% 3 8% 4 1	1890
	11th to 20th	Day	24% 59% 4 9% 4	1851
	21st to end	Day	19% 59% 5% 9% 6% 1	1585
March	1st to 10th	Day	44% 29% 6% 12% 7% 1	4939
	11th to 20th	Day	42% 34% 12% 9% 3	5057
	21st to end	Day	50% 31% 6% 9% 4	5510
April	1st to 10th	Day	23% 62% 3 6% 5% 2	2400
	11th to 20th	Day	20% 63% 4 9% 4	2454
	21st to end	Day	23% 62% 4 6% 4 1	2600
May	1st to 10th	Day	43% 31% 10% 11% 5%	6214
	11th to 20th	Day	37% 32% 11% 17% 3	6322
	21st to end	Day	35% 34% 10% 15% 6%	6948
June	1st to 10th	Day	20% 63% 4 9% 3	2849
	11th to 20th	Day	18% 62% 6% 9% 4	3000
	21st to end	Day	21% 61% 5% 8% 6%	3000
July	1st to 10th	Day	41% 28% 13% 11% 6%	6745
	11th to 20th	Day	30% 27% 13% 24% 5%	6386
	21st to end	Day	27% 30% 15% 22% 5%	6730
August	1st to 10th	Day	34% 38% 8% 16% 3	4237
	11th to 20th	Day	26% 39% 8% 16% 9%	4214
	21st to end	Day	23% 38% 11% 18% 11%	4492
September	1st to 10th	Day	15% 59% 7% 14% 6%	2400
	11th to 20th	Day	22% 58% 7% 10% 4	2359
	21st to end	Day	17% 58% 5% 13% 7%	2115
October	1st to 10th	Day	30% 38% 9% 18% 5%	3260
	11th to 20th	Day	33% 38% 6% 18% 5%	3240
	21st to end	Day	30% 37% 15% 14% 4	3460
November	1st to 10th	Day	29% 55% 5% 8% 2	1667
	11th to 20th	Day	35% 55% 5% 3 2	1680
	21st to end	Day	31% 57% 7% 4 1	1680
December	1st to 10th	Day	45% 38% 4 13% 1	2690
	11th to 20th	Day	45% 33% 7% 8% 6%	3075
	21st to end	Day	51% 29% 8% 10% 2	3741
January	1st to 10th	Night	48% 29% 9% 11% 3	8716
	11th to 20th	Night	51% 25% 9% 10% 4	8280
	21st to end	Night	39% 28% 9% 11% 13% 1	8480
February	1st to 10th	Night	25% 59% 3 6% 5% 1	2730
	11th to 20th	Night	24% 58% 4 9% 4	2666
	21st to end	Night	20% 60% 3 9% 6% 2	2220
March	1st to 10th	Night	46% 29% 5% 9% 10% 1	5131
	11th to 20th	Night	45% 32% 9% 7% 6% 1	5058
	21st to end	Night	49% 31% 4 10% 6%	5421
April	1st to 10th	Night	23% 62% 4 6% 5% 1	2000
	11th to 20th	Night	22% 63% 4 8% 3 1	1893
	21st to end	Night	23% 62% 3 6% 5% 1	1800
May	1st to 10th	Night	48% 33% 5% 8% 7%	3755
	11th to 20th	Night	35% 33% 11% 15% 5% 1	3597
	21st to end	Night	34% 34% 14% 15% 3	3949
June	1st to 10th	Night	20% 62% 5% 9% 4	1566
	11th to 20th	Night	16% 63% 6% 11% 5%	1400
	21st to end	Night	21% 61% 4 8% 5% 1	1400
July	1st to 10th	Night	43% 29% 10% 11% 5% 1	3125
	11th to 20th	Night	30% 29% 15% 19% 6%	3410
	21st to end	Night	31% 29% 16% 18% 6%	3831
August	1st to 10th	Night	37% 38% 10% 12% 3	2872
	11th to 20th	Night	24% 41% 12% 13% 9% 1	2899
	21st to end	Night	24% 37% 12% 17% 10%	3405
September	1st to 10th	Night	15% 58% 5% 15% 6%	2000
	11th to 20th	Night	20% 58% 6% 12% 4	2039
	21st to end	Night	16% 59% 5% 14% 6%	2285
October	1st to 10th	Night	32% 37% 11% 16% 5%	3920
	11th to 20th	Night	26% 38% 8% 19% 8%	3899
	21st to end	Night	30% 37% 13% 14% 7%	4332
November	1st to 10th	Night	29% 55% 7% 6% 3	2848
	11th to 20th	Night	31% 56% 6% 6% 1	2940
	21st to end	Night	32% 56% 6% 4 2	2940
December	1st to 10th	Night	38% 39% 9% 13% 2	4720
	11th to 20th	Night	40% 34% 8% 12% 5% 1	5355
	21st to end	Night	49% 28% 9% 9% 4	7456

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	24% 21% 33% 17% 5%	249
	11th to 20th	Day	26% 17% 31% 21% 5%	430
	21st to end	Day	16% 14% 39% 25% 5%	473
February	1st to 10th	Day	25% 14% 33% 20% 6% 2	430
	11th to 20th	Day	22% 16% 35% 21% 5%	426
	21st to end	Day	17% 13% 33% 28% 8% 1	355
March	1st to 10th	Day	23% 14% 32% 25% 5% 1	512
	11th to 20th	Day	19% 15% 34% 24% 8% 1	528
	21st to end	Day	25% 15% 28% 23% 9% 1	550
April	1st to 10th	Day	28% 14% 33% 19% 6%	500
	11th to 20th	Day	22% 13% 32% 22% 9% 2	492
	21st to end	Day	24% 13% 25% 24% 12% 1	500
May	1st to 10th	Day	30% 8% 31% 22% 7% 1	638
	11th to 20th	Day	22% 7% 26% 28% 14% 2	724
	21st to end	Day	22% 10% 29% 28% 10% 1	790
June	1st to 10th	Day	29% 8% 23% 28% 11% 1	730
	11th to 20th	Day	20% 7% 30% 32% 10% 2	730
	21st to end	Day	27% 5% 24% 30% 12% 3	730
July	1st to 10th	Day	19% 5% 28% 31% 14% 3	720
	11th to 20th	Day	17% 5% 24% 34% 17% 3	718
	21st to end	Day	17% 5% 23% 37% 16% 2	795
August	1st to 10th	Day	13% 5% 23% 39% 17% 4	542
	11th to 20th	Day	16% 3 25% 32% 18% 6%	519
	21st to end	Day	15% 7% 27% 29% 18% 5%	583
September	1st to 10th	Day	15% 7% 29% 33% 14% 3	530
	11th to 20th	Day	20% 9% 26% 28% 15% 2	530
	21st to end	Day	18% 11% 29% 26% 13% 3	483
October	1st to 10th	Day	19% 12% 27% 24% 17% 2	420
	11th to 20th	Day	23% 14% 29% 20% 12% 2	420
	21st to end	Day	21% 19% 31% 21% 6% 1	462
November	1st to 10th	Day	25% 18% 32% 19% 5% 1	425
	11th to 20th	Day	33% 20% 26% 16% 4 1	430
	21st to end	Day	27% 19% 33% 17% 3 1	430
December	1st to 10th	Day	30% 16% 34% 18% 3	430
	11th to 20th	Day	29% 24% 33% 12% 2	430
	21st to end	Day	23% 19% 36% 17% 4 1	326
January	1st to 10th	Night	25% 16% 34% 19% 5%	950
	11th to 20th	Night	25% 17% 31% 22% 5%	950
	21st to end	Night	18% 15% 35% 23% 7% 1	938
February	1st to 10th	Night	24% 14% 33% 22% 5% 1	840
	11th to 20th	Night	23% 14% 36% 22% 4 1	823
	21st to end	Night	19% 11% 34% 28% 8% 1	692
March	1st to 10th	Night	23% 12% 35% 26% 3	840
	11th to 20th	Night	22% 13% 30% 28% 7% 1	829
	21st to end	Night	27% 12% 27% 24% 9% 1	860
April	1st to 10th	Night	28% 11% 32% 24% 5%	600
	11th to 20th	Night	27% 8% 30% 26% 8% 1	594
	21st to end	Night	28% 8% 30% 26% 8% 1	600
May	1st to 10th	Night	29% 7% 30% 23% 9% 2	600
	11th to 20th	Night	22% 7% 28% 30% 11% 2	592
	21st to end	Night	18% 8% 36% 31% 6%	649
June	1st to 10th	Night	28% 9% 26% 30% 7% 1	566
	11th to 20th	Night	20% 6% 28% 37% 9% 1	400
	21st to end	Night	26% 4 26% 35% 9% 1	400
July	1st to 10th	Night	17% 6% 29% 35% 13% 1	390
	11th to 20th	Night	14% 5% 32% 38% 11% 1	511
	21st to end	Night	17% 5% 23% 40% 14%	656
August	1st to 10th	Night	16% 4 28% 36% 16% 1	598
	11th to 20th	Night	15% 4 26% 36% 18% 1	592
	21st to end	Night	15% 6% 23% 36% 18% 1	660
September	1st to 10th	Night	17% 6% 30% 34% 11% 1	600
	11th to 20th	Night	19% 9% 22% 37% 13% 1	639
	21st to end	Night	19% 10% 29% 31% 10% 1	800
October	1st to 10th	Night	22% 9% 28% 29% 11%	800
	11th to 20th	Night	22% 13% 30% 24% 9% 2	800
	21st to end	Night	29% 18% 27% 21% 5%	905
November	1st to 10th	Night	28% 17% 31% 19% 4 1	930
	11th to 20th	Night	29% 20% 26% 19% 5% 1	950
	21st to end	Night	30% 20% 27% 20% 3 1	950
December	1st to 10th	Night	28% 19% 31% 18% 4	950
	11th to 20th	Night	27% 24% 31% 15% 3	950
	21st to end	Night	29% 17% 31% 19% 4 1	1045

Page generated at 2026-03-15 03:23:53. Version ac07

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