Voyageurs National Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Voyageurs National Park clear sky chart from 2005-11-06 to 2026-04-17.

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% 5% 5% 5% 4 6% 7% 33%	131692
	Night	12% 12% 5% 11% 6% 5% 5% 4 5% 6% 29%	130775
Transparency	Day	49% 6% 14% 21% 9% 1	135156
	Night	54% 6% 12% 19% 9% 1	135398
Seeing	Day	19% 14% 33% 23% 9% 2	18112
	Night	18% 12% 33% 27% 9% 1	28182

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	6% 12% 8% 16% 10% 7% 7% 4 5% 5% 20%	4124
	11th to 20th	Day	5% 15% 6% 15% 8% 7% 10% 9% 8% 4 12%	4240
	21st to end	Day	5% 13% 9% 16% 7% 6% 7% 6% 7% 6% 18%	5369
February	1st to 10th	Day	7% 15% 6% 13% 6% 6% 8% 5% 7% 6% 21%	1890
	11th to 20th	Day	9% 11% 5% 10% 7% 6% 6% 4 6% 7% 30%	1844
	21st to end	Day	8% 14% 4 12% 6% 6% 5% 3 4 6% 32%	1584
March	1st to 10th	Day	10% 10% 4 8% 4 4 4 3 4 6% 41%	4802
	11th to 20th	Day	9% 11% 6% 13% 6% 4 5% 3 6% 6% 31%	5090
	21st to end	Day	15% 14% 4 10% 5% 3 3 3 4 6% 32%	5724
April	1st to 10th	Day	16% 12% 4 8% 6% 5% 5% 3 5% 6% 30%	2520
	11th to 20th	Day	17% 12% 3 9% 5% 4 4 4 5% 7% 31%	2525
	21st to end	Day	19% 12% 4 7% 5% 4 4 4 5% 5% 32%	2640
May	1st to 10th	Day	16% 8% 2 5% 3 3 4 3 4 6% 45%	6348
	11th to 20th	Day	14% 9% 3 7% 5% 5% 5% 4 6% 8% 36%	6319
	21st to end	Day	15% 7% 2 5% 4 4 4 4 6% 7% 43%	6949
June	1st to 10th	Day	14% 7% 3 6% 5% 4 6% 5% 6% 8% 37%	2990
	11th to 20th	Day	15% 7% 2 7% 6% 5% 5% 4 5% 8% 36%	3000
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 5% 7% 9% 34%	3000
July	1st to 10th	Day	8% 5% 2 6% 5% 6% 6% 5% 8% 10% 41%	6799
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 4 6% 9% 40%	6800
	21st to end	Day	11% 7% 3 7% 5% 5% 4 4 7% 9% 38%	6931
August	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 8% 38%	4479
	11th to 20th	Day	12% 4 2 5% 4 4 5% 4 7% 10% 43%	4171
	21st to end	Day	14% 7% 2 5% 4 4 4 4 6% 9% 40%	4548
September	1st to 10th	Day	13% 7% 2 6% 4 5% 4 4 5% 8% 42%	2400
	11th to 20th	Day	15% 8% 2 6% 5% 4 5% 4 6% 8% 38%	2400
	21st to end	Day	19% 8% 3 6% 4 4 3 4 5% 7% 37%	2086
October	1st to 10th	Day	18% 11% 3 7% 4 4 4 3 5% 7% 34%	2000
	11th to 20th	Day	19% 15% 4 9% 5% 4 5% 3 5% 6% 26%	2000
	21st to end	Day	20% 18% 4 9% 6% 5% 3 2 3 5% 26%	2057
November	1st to 10th	Day	13% 20% 6% 11% 5% 4 5% 4 4 5% 23%	1647
	11th to 20th	Day	14% 20% 7% 14% 6% 4 3 3 4 4 22%	1680
	21st to end	Day	15% 16% 8% 18% 8% 5% 3 3 4 4 16%	1680
December	1st to 10th	Day	12% 17% 6% 22% 12% 5% 5% 3 4 4 11%	2690
	11th to 20th	Day	8% 18% 9% 13% 6% 7% 6% 4 5% 4 21%	2791
	21st to end	Day	16% 20% 6% 17% 8% 5% 5% 3 4 4 11%	3575
January	1st to 10th	Night	5% 13% 7% 21% 9% 7% 6% 4 5% 5% 20%	8800
	11th to 20th	Night	6% 13% 7% 15% 11% 10% 9% 8% 6% 3 12%	8672
	21st to end	Night	5% 14% 9% 13% 7% 6% 8% 4 6% 8% 19%	8841
February	1st to 10th	Night	7% 12% 5% 12% 8% 7% 7% 5% 6% 6% 24%	2730
	11th to 20th	Night	8% 9% 4 11% 6% 5% 7% 5% 6% 6% 32%	2663
	21st to end	Night	7% 14% 5% 12% 8% 5% 6% 4 5% 5% 28%	2221
March	1st to 10th	Night	11% 9% 4 9% 5% 5% 6% 4 5% 6% 35%	5304
	11th to 20th	Night	7% 13% 5% 14% 9% 8% 6% 4 5% 6% 23%	5089
	21st to end	Night	19% 16% 4 9% 5% 3 4 2 3 4 30%	5448
April	1st to 10th	Night	16% 13% 5% 10% 5% 4 4 2 6% 5% 32%	2100
	11th to 20th	Night	14% 14% 4 8% 5% 4 4 3 4 6% 34%	1955
	21st to end	Night	20% 12% 3 7% 5% 4 5% 3 5% 4 32%	1760
May	1st to 10th	Night	17% 7% 1 4 3 3 3 3 4 6% 49%	3613
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 5% 8% 40%	3596
	21st to end	Night	16% 6% 2 5% 3 4 4 4 6% 7% 43%	3949
June	1st to 10th	Night	17% 5% 2 7% 4 4 4 3 5% 7% 42%	1405
	11th to 20th	Night	11% 7% 2 6% 4 5% 4 3 5% 8% 45%	1400
	21st to end	Night	13% 7% 2 6% 4 4 4 4 4 9% 43%	1400
July	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 7% 9% 48%	3180
	11th to 20th	Night	11% 6% 2 4 3 3 4 3 6% 9% 48%	3180
	21st to end	Night	11% 7% 3 6% 4 4 4 4 6% 9% 45%	3941
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 9% 44%	2678
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 6% 9% 45%	2888
	21st to end	Night	13% 6% 2 6% 4 4 3 3 5% 8% 45%	3357
September	1st to 10th	Night	13% 6% 2 7% 4 4 4 3 5% 6% 46%	2000
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 5% 7% 44%	2000
	21st to end	Night	18% 8% 3 6% 4 3 4 3 4 7% 40%	2290
October	1st to 10th	Night	17% 10% 3 7% 4 4 4 4 4 7% 36%	2400
	11th to 20th	Night	19% 14% 3 8% 4 3 4 3 4 6% 32%	2400
	21st to end	Night	19% 16% 4 10% 5% 4 4 3 5% 6% 25%	2780
November	1st to 10th	Night	14% 17% 6% 11% 6% 4 4 3 5% 5% 26%	2871
	11th to 20th	Night	15% 17% 7% 16% 7% 5% 4 3 4 5% 18%	2940
	21st to end	Night	13% 15% 6% 17% 9% 5% 5% 4 4 4 18%	2940
December	1st to 10th	Night	10% 19% 9% 22% 10% 7% 4 3 4 4 9%	4720
	11th to 20th	Night	10% 14% 6% 15% 9% 7% 6% 6% 4 5% 17%	5619
	21st to end	Night	18% 18% 7% 17% 7% 5% 4 3 4 4 13%	7645

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	65% 4 7% 15% 8% 1	4125
	11th to 20th	Day	69% 5% 5% 17% 4	4268
	21st to end	Day	64% 5% 10% 15% 7%	5369
February	1st to 10th	Day	60% 6% 10% 14% 9% 1	1890
	11th to 20th	Day	51% 5% 12% 20% 10% 1	1853
	21st to end	Day	54% 5% 12% 17% 11% 1	1584
March	1st to 10th	Day	43% 5% 14% 20% 14% 5%	4804
	11th to 20th	Day	51% 6% 12% 19% 11%	5090
	21st to end	Day	53% 5% 9% 20% 12% 1	5724
April	1st to 10th	Day	53% 5% 10% 17% 14% 1	2520
	11th to 20th	Day	52% 7% 12% 18% 10% 1	2525
	21st to end	Day	53% 6% 10% 20% 10% 1	2640
May	1st to 10th	Day	37% 7% 15% 25% 16% 1	6357
	11th to 20th	Day	44% 8% 10% 21% 16% 2	6323
	21st to end	Day	38% 6% 10% 27% 16% 2	6949
June	1st to 10th	Day	41% 10% 16% 23% 10% 1	2990
	11th to 20th	Day	45% 8% 14% 21% 12%	3000
	21st to end	Day	44% 9% 17% 23% 7% 1	3000
July	1st to 10th	Day	35% 9% 21% 27% 7%	6726
	11th to 20th	Day	38% 6% 19% 31% 5%	6719
	21st to end	Day	40% 7% 17% 28% 7%	6732
August	1st to 10th	Day	41% 7% 18% 23% 10% 1	4464
	11th to 20th	Day	34% 10% 24% 28% 5%	4210
	21st to end	Day	40% 7% 21% 26% 6%	4547
September	1st to 10th	Day	40% 7% 16% 29% 8%	2400
	11th to 20th	Day	44% 8% 21% 22% 5%	2400
	21st to end	Day	47% 7% 13% 26% 6%	2086
October	1st to 10th	Day	40% 5% 18% 27% 10%	3260
	11th to 20th	Day	51% 6% 14% 19% 10%	3240
	21st to end	Day	59% 5% 14% 18% 3	3297
November	1st to 10th	Day	62% 7% 11% 14% 5% 1	1647
	11th to 20th	Day	66% 5% 10% 13% 5%	1680
	21st to end	Day	73% 6% 10% 8% 3	1680
December	1st to 10th	Day	77% 6% 9% 7% 1	2690
	11th to 20th	Day	65% 5% 8% 11% 10%	2792
	21st to end	Day	76% 4 6% 10% 4	3575
January	1st to 10th	Night	66% 5% 9% 12% 8%	8800
	11th to 20th	Night	72% 5% 6% 11% 5%	8719
	21st to end	Night	63% 4 9% 18% 7%	8841
February	1st to 10th	Night	58% 5% 12% 16% 9% 1	2730
	11th to 20th	Night	50% 6% 14% 20% 10% 1	2664
	21st to end	Night	57% 5% 10% 18% 7% 1	2221
March	1st to 10th	Night	47% 7% 12% 16% 14% 4	5315
	11th to 20th	Night	59% 7% 12% 14% 7% 1	5090
	21st to end	Night	58% 5% 7% 16% 13% 1	5448
April	1st to 10th	Night	54% 5% 9% 16% 16% 1	2100
	11th to 20th	Night	50% 6% 10% 20% 13% 2	1955
	21st to end	Night	54% 5% 9% 19% 12% 1	1760
May	1st to 10th	Night	36% 6% 11% 28% 18%	3620
	11th to 20th	Night	39% 8% 14% 20% 17% 2	3597
	21st to end	Night	39% 6% 10% 27% 16% 2	3950
June	1st to 10th	Night	40% 7% 17% 23% 12% 1	1405
	11th to 20th	Night	38% 7% 12% 26% 15% 1	1400
	21st to end	Night	39% 8% 18% 26% 9% 1	1400
July	1st to 10th	Night	30% 9% 22% 30% 10%	3145
	11th to 20th	Night	32% 6% 20% 32% 10%	3138
	21st to end	Night	36% 6% 17% 31% 8%	3826
August	1st to 10th	Night	37% 7% 17% 28% 11% 1	2669
	11th to 20th	Night	34% 8% 20% 31% 7%	2915
	21st to end	Night	38% 6% 21% 27% 8%	3357
September	1st to 10th	Night	37% 8% 16% 28% 10%	2000
	11th to 20th	Night	38% 10% 19% 26% 7%	2000
	21st to end	Night	44% 6% 14% 29% 7%	2290
October	1st to 10th	Night	37% 6% 13% 33% 10% 1	3920
	11th to 20th	Night	49% 5% 15% 23% 8%	3899
	21st to end	Night	57% 5% 12% 21% 4	4491
November	1st to 10th	Night	60% 6% 12% 16% 6% 1	2871
	11th to 20th	Night	69% 6% 9% 11% 5%	2940
	21st to end	Night	68% 8% 11% 9% 4	2940
December	1st to 10th	Night	79% 6% 7% 7% 1	4720
	11th to 20th	Night	68% 5% 9% 11% 7%	5617
	21st to end	Night	75% 4 6% 11% 3	7645

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	12% 17% 42% 22% 7% 1	330
	11th to 20th	Day	16% 10% 43% 25% 5% 1	330
	21st to end	Day	15% 12% 44% 21% 8%	363
February	1st to 10th	Day	18% 19% 42% 15% 6% 1	330
	11th to 20th	Day	14% 22% 36% 17% 9% 2	330
	21st to end	Day	21% 19% 44% 13% 4	273
March	1st to 10th	Day	20% 16% 39% 18% 6% 1	330
	11th to 20th	Day	16% 21% 36% 18% 7% 2	330
	21st to end	Day	20% 20% 34% 17% 7% 2	425
April	1st to 10th	Day	24% 17% 35% 17% 8%	540
	11th to 20th	Day	24% 16% 30% 22% 6% 1	595
	21st to end	Day	23% 15% 30% 21% 10% 1	700
May	1st to 10th	Day	21% 18% 34% 17% 8% 2	703
	11th to 20th	Day	21% 13% 31% 23% 10% 2	725
	21st to end	Day	22% 12% 27% 29% 8% 2	789
June	1st to 10th	Day	16% 14% 31% 25% 11% 3	730
	11th to 20th	Day	17% 13% 37% 23% 8% 2	730
	21st to end	Day	19% 8% 31% 27% 10% 5%	730
July	1st to 10th	Day	12% 9% 28% 30% 14% 7%	721
	11th to 20th	Day	14% 11% 30% 25% 16% 5%	718
	21st to end	Day	10% 9% 31% 28% 17% 6%	794
August	1st to 10th	Day	12% 9% 28% 32% 16% 3	726
	11th to 20th	Day	15% 7% 27% 27% 18% 6%	715
	21st to end	Day	16% 10% 29% 27% 15% 3	728
September	1st to 10th	Day	16% 12% 32% 25% 12% 3	530
	11th to 20th	Day	20% 12% 30% 26% 9% 2	530
	21st to end	Day	22% 18% 29% 19% 10% 1	331
October	1st to 10th	Day	24% 16% 34% 16% 9% 1	330
	11th to 20th	Day	24% 19% 38% 17% 2	330
	21st to end	Day	31% 20% 32% 14% 2 1	363
November	1st to 10th	Day	24% 20% 32% 19% 5% 1	330
	11th to 20th	Day	27% 19% 33% 16% 4 1	330
	21st to end	Day	28% 18% 35% 16% 3	330
December	1st to 10th	Day	21% 16% 40% 19% 5%	330
	11th to 20th	Day	22% 17% 40% 18% 2	330
	21st to end	Day	22% 14% 41% 17% 4 1	363
January	1st to 10th	Night	12% 16% 38% 23% 9% 1	1050
	11th to 20th	Night	17% 10% 42% 23% 7% 1	1050
	21st to end	Night	17% 12% 39% 26% 6%	1155
February	1st to 10th	Night	14% 12% 37% 28% 8%	1050
	11th to 20th	Night	13% 14% 38% 25% 9% 2	1029
	21st to end	Night	14% 12% 38% 25% 9% 3	837
March	1st to 10th	Night	17% 15% 33% 27% 9% 1	766
	11th to 20th	Night	15% 16% 37% 26% 6% 1	630
	21st to end	Night	22% 11% 31% 23% 10% 3	693
April	1st to 10th	Night	21% 13% 33% 26% 7%	630
	11th to 20th	Night	20% 11% 34% 27% 7%	611
	21st to end	Night	25% 11% 23% 33% 9% 1	600
May	1st to 10th	Night	20% 11% 34% 28% 7% 1	600
	11th to 20th	Night	19% 10% 35% 27% 8% 1	591
	21st to end	Night	18% 9% 30% 34% 9%	650
June	1st to 10th	Night	18% 7% 29% 33% 13% 1	600
	11th to 20th	Night	13% 9% 31% 36% 11%	600
	21st to end	Night	16% 6% 29% 34% 14% 2	600
July	1st to 10th	Night	8% 4 27% 40% 20% 1	585
	11th to 20th	Night	9% 7% 30% 35% 18% 1	582
	21st to end	Night	8% 5% 28% 36% 21% 2	657
August	1st to 10th	Night	10% 4 28% 39% 18% 1	597
	11th to 20th	Night	14% 6% 21% 38% 18% 3	594
	21st to end	Night	14% 8% 29% 33% 15% 1	660
September	1st to 10th	Night	16% 6% 29% 32% 17% 1	600
	11th to 20th	Night	18% 7% 31% 28% 15% 1	600
	21st to end	Night	22% 11% 29% 25% 12% 1	695
October	1st to 10th	Night	23% 13% 33% 25% 6% 1	800
	11th to 20th	Night	26% 15% 30% 22% 6%	800
	21st to end	Night	27% 14% 33% 22% 4	890
November	1st to 10th	Night	23% 15% 32% 25% 5% 1	1025
	11th to 20th	Night	23% 17% 32% 21% 6% 1	1050
	21st to end	Night	22% 19% 38% 17% 4	1050
December	1st to 10th	Night	18% 13% 38% 25% 6%	1050
	11th to 20th	Night	21% 13% 38% 21% 6% 1	1050
	21st to end	Night	24% 13% 30% 25% 7% 1	1155

Page generated at 2026-04-14 01:44:30. Version ac07

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