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 2024-12-24.

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% 10% 4 9% 5% 5% 5% 4 6% 7% 33%	102214
	Night	13% 12% 5% 10% 6% 5% 5% 4 5% 6% 30%	98061
Transparency	Day	48% 7% 14% 22% 8% 1	105698
	Night	52% 7% 13% 20% 8% 1	102665
Seeing	Day	18% 14% 33% 23% 10% 2	16346
	Night	18% 11% 33% 27% 10% 1	26328

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% 12% 9% 16% 9% 8% 6% 4 5% 5% 19%	2218
	11th to 20th	Day	6% 12% 5% 12% 10% 8% 12% 7% 6% 5% 16%	2283
	21st to end	Day	8% 16% 11% 18% 7% 6% 6% 4 5% 4 13%	2884
February	1st to 10th	Day	7% 14% 5% 13% 6% 5% 8% 5% 7% 6% 22%	1710
	11th to 20th	Day	9% 11% 5% 11% 8% 6% 6% 4 5% 6% 29%	1664
	21st to end	Day	8% 13% 4 11% 7% 6% 5% 3 4 6% 32%	1437
March	1st to 10th	Day	10% 10% 4 7% 4 4 4 3 5% 6% 42%	3268
	11th to 20th	Day	7% 10% 7% 15% 6% 5% 4 3 5% 6% 33%	3480
	21st to end	Day	15% 16% 5% 10% 5% 3 3 3 4 6% 32%	3908
April	1st to 10th	Day	15% 12% 4 8% 6% 5% 5% 3 5% 6% 31%	2280
	11th to 20th	Day	16% 12% 3 9% 5% 4 4 4 5% 7% 30%	2328
	21st to end	Day	18% 12% 4 7% 5% 4 4 4 5% 5% 33%	2508
May	1st to 10th	Day	18% 9% 2 6% 4 4 5% 4 5% 7% 35%	4428
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	4399
	21st to end	Day	20% 9% 3 6% 4 3 3 3 5% 7% 37%	4837
June	1st to 10th	Day	15% 7% 3 6% 4 4 6% 5% 6% 8% 37%	2840
	11th to 20th	Day	16% 7% 2 7% 6% 5% 5% 4 4 8% 36%	2850
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 5% 7% 9% 34%	2850
July	1st to 10th	Day	8% 5% 2 6% 5% 6% 6% 5% 7% 10% 40%	4750
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 7% 9% 47%	4750
	21st to end	Day	10% 6% 3 6% 5% 5% 5% 5% 8% 9% 39%	4819
August	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 9% 38%	4342
	11th to 20th	Day	12% 4 2 5% 4 4 5% 4 6% 9% 43%	4041
	21st to end	Day	15% 7% 2 5% 4 4 4 4 6% 9% 40%	4409
September	1st to 10th	Day	13% 7% 2 6% 4 5% 4 4 5% 8% 43%	2280
	11th to 20th	Day	15% 8% 3 7% 5% 4 5% 4 5% 8% 38%	2280
	21st to end	Day	20% 8% 3 6% 4 4 3 4 5% 7% 35%	1982
October	1st to 10th	Day	19% 12% 3 7% 4 4 4 3 5% 7% 33%	1900
	11th to 20th	Day	18% 15% 4 8% 5% 4 5% 3 5% 6% 26%	1900
	21st to end	Day	20% 18% 4 8% 6% 5% 3 2 3 5% 26%	1955
November	1st to 10th	Day	13% 20% 6% 10% 5% 4 5% 4 5% 5% 23%	1567
	11th to 20th	Day	14% 20% 7% 15% 6% 5% 3 3 4 4 20%	1600
	21st to end	Day	15% 16% 8% 18% 8% 5% 3 3 4 4 16%	1600
December	1st to 10th	Day	11% 16% 6% 18% 9% 5% 7% 5% 5% 5% 14%	1600
	11th to 20th	Day	10% 18% 9% 13% 7% 5% 5% 4 4 4 20%	1804
	21st to end	Day	20% 21% 6% 12% 8% 4 4 3 4 4 13%	2463
January	1st to 10th	Night	6% 16% 6% 17% 9% 6% 5% 4 5% 5% 22%	4737
	11th to 20th	Night	6% 12% 6% 14% 12% 11% 10% 6% 5% 4 15%	4684
	21st to end	Night	8% 20% 13% 15% 6% 4 5% 4 5% 5% 17%	4779
February	1st to 10th	Night	7% 12% 5% 12% 7% 7% 7% 6% 6% 6% 25%	2470
	11th to 20th	Night	8% 9% 4 11% 7% 5% 6% 4 5% 6% 33%	2403
	21st to end	Night	7% 14% 6% 12% 7% 5% 6% 4 5% 5% 29%	2016
March	1st to 10th	Night	12% 10% 4 9% 5% 5% 5% 3 5% 6% 36%	3604
	11th to 20th	Night	8% 11% 4 13% 9% 7% 5% 4 5% 7% 28%	3479
	21st to end	Night	19% 16% 4 9% 5% 4 4 3 4 4 30%	3722
April	1st to 10th	Night	15% 12% 4 10% 6% 4 4 2 6% 5% 33%	1900
	11th to 20th	Night	14% 13% 4 8% 5% 4 4 4 5% 6% 34%	1799
	21st to end	Night	19% 12% 3 7% 5% 4 5% 4 5% 4 33%	1672
May	1st to 10th	Night	18% 9% 2 5% 4 4 4 4 5% 7% 38%	2523
	11th to 20th	Night	14% 8% 2 7% 5% 4 5% 5% 6% 9% 36%	2506
	21st to end	Night	22% 6% 2 5% 3 4 4 3 5% 6% 39%	2750
June	1st to 10th	Night	17% 5% 2 7% 4 4 4 3 5% 7% 42%	1335
	11th to 20th	Night	12% 7% 2 6% 4 5% 4 3 5% 8% 45%	1330
	21st to end	Night	13% 7% 2 6% 4 4 4 4 4 9% 44%	1330
July	1st to 10th	Night	8% 4 1 5% 4 4 5% 4 8% 10% 46%	2220
	11th to 20th	Night	6% 5% 2 3 3 3 5% 3 7% 10% 53%	2220
	21st to end	Night	9% 5% 2 5% 3 3 3 3 5% 8% 51%	2743
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 9% 44%	2596
	11th to 20th	Night	12% 5% 2 6% 3 4 4 4 6% 9% 45%	2798
	21st to end	Night	14% 5% 2 6% 4 4 3 3 5% 7% 45%	3254
September	1st to 10th	Night	12% 6% 2 7% 4 4 4 3 5% 6% 46%	1900
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 5% 7% 45%	1900
	21st to end	Night	19% 8% 3 6% 4 3 4 3 4 7% 39%	2175
October	1st to 10th	Night	17% 10% 3 7% 4 4 4 4 4 7% 35%	2280
	11th to 20th	Night	19% 14% 3 8% 4 3 4 3 4 6% 32%	2280
	21st to end	Night	19% 16% 4 10% 5% 4 4 3 5% 6% 24%	2640
November	1st to 10th	Night	15% 17% 6% 11% 6% 4 4 3 5% 5% 26%	2731
	11th to 20th	Night	15% 17% 7% 17% 8% 5% 4 3 4 4 17%	2800
	21st to end	Night	13% 15% 6% 17% 9% 5% 5% 4 5% 5% 18%	2800
December	1st to 10th	Night	9% 17% 7% 18% 10% 7% 5% 4 5% 6% 14%	2800
	11th to 20th	Night	10% 16% 6% 14% 10% 7% 6% 5% 5% 6% 16%	3608
	21st to end	Night	20% 19% 7% 13% 7% 5% 4 3 3 3 13%	5277

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% 6% 8% 15% 5%	2219
	11th to 20th	Day	66% 8% 7% 16% 3	2283
	21st to end	Day	71% 8% 8% 9% 4	2884
February	1st to 10th	Day	58% 7% 11% 14% 9% 1	1710
	11th to 20th	Day	53% 6% 12% 19% 9% 1	1673
	21st to end	Day	53% 5% 13% 17% 12% 1	1437
March	1st to 10th	Day	42% 6% 13% 23% 16% 1	3270
	11th to 20th	Day	49% 8% 14% 20% 9%	3480
	21st to end	Day	53% 7% 10% 20% 9% 2	3908
April	1st to 10th	Day	52% 5% 10% 17% 14% 2	2280
	11th to 20th	Day	52% 7% 11% 18% 10% 1	2328
	21st to end	Day	52% 6% 10% 20% 11% 1	2508
May	1st to 10th	Day	44% 9% 14% 21% 11% 1	4440
	11th to 20th	Day	45% 10% 12% 21% 10% 2	4403
	21st to end	Day	46% 7% 11% 24% 11% 1	4837
June	1st to 10th	Day	41% 10% 16% 22% 10% 1	2840
	11th to 20th	Day	45% 8% 13% 21% 13%	2850
	21st to end	Day	43% 10% 17% 23% 7%	2850
July	1st to 10th	Day	35% 9% 20% 28% 7%	4676
	11th to 20th	Day	30% 7% 21% 34% 7%	4669
	21st to end	Day	39% 8% 15% 31% 6%	4666
August	1st to 10th	Day	41% 7% 18% 23% 10% 1	4327
	11th to 20th	Day	34% 10% 23% 28% 5%	4080
	21st to end	Day	40% 7% 21% 26% 6%	4408
September	1st to 10th	Day	39% 7% 16% 29% 9%	2280
	11th to 20th	Day	43% 8% 20% 23% 5%	2280
	21st to end	Day	48% 8% 13% 25% 6%	1982
October	1st to 10th	Day	41% 5% 18% 27% 10%	3160
	11th to 20th	Day	51% 6% 14% 19% 10%	3140
	21st to end	Day	59% 5% 15% 18% 3	3195
November	1st to 10th	Day	62% 7% 11% 15% 5% 1	1567
	11th to 20th	Day	68% 6% 9% 12% 5%	1600
	21st to end	Day	72% 6% 10% 8% 3	1600
December	1st to 10th	Day	70% 8% 11% 9% 2	1600
	11th to 20th	Day	67% 6% 10% 13% 4	1805
	21st to end	Day	74% 4 7% 10% 5%	2463
January	1st to 10th	Night	63% 6% 12% 15% 4	4737
	11th to 20th	Night	68% 8% 9% 11% 3	4684
	21st to end	Night	69% 5% 10% 12% 3	4779
February	1st to 10th	Night	56% 6% 12% 16% 9% 1	2470
	11th to 20th	Night	50% 6% 14% 20% 10% 1	2404
	21st to end	Night	56% 6% 11% 18% 8% 2	2016
March	1st to 10th	Night	47% 8% 13% 18% 14% 1	3615
	11th to 20th	Night	53% 8% 14% 17% 7% 1	3480
	21st to end	Night	58% 6% 9% 15% 11% 1	3722
April	1st to 10th	Night	52% 5% 9% 17% 16% 1	1900
	11th to 20th	Night	50% 6% 10% 20% 13% 2	1799
	21st to end	Night	54% 5% 9% 19% 12% 1	1672
May	1st to 10th	Night	42% 9% 10% 24% 15%	2530
	11th to 20th	Night	41% 10% 15% 21% 10% 3	2507
	21st to end	Night	45% 7% 12% 24% 11% 1	2751
June	1st to 10th	Night	40% 8% 17% 23% 12% 1	1335
	11th to 20th	Night	38% 7% 12% 25% 16% 2	1330
	21st to end	Night	38% 8% 17% 26% 9% 1	1330
July	1st to 10th	Night	29% 11% 24% 27% 9%	2185
	11th to 20th	Night	24% 7% 18% 38% 12%	2178
	21st to end	Night	31% 7% 17% 36% 9% 1	2656
August	1st to 10th	Night	37% 7% 17% 28% 11% 1	2587
	11th to 20th	Night	34% 8% 20% 31% 7%	2825
	21st to end	Night	38% 7% 21% 26% 8%	3254
September	1st to 10th	Night	37% 8% 16% 28% 11%	1900
	11th to 20th	Night	37% 10% 20% 26% 7%	1900
	21st to end	Night	45% 6% 14% 28% 6%	2175
October	1st to 10th	Night	37% 6% 12% 34% 10% 1	3800
	11th to 20th	Night	49% 5% 15% 23% 8%	3779
	21st to end	Night	57% 5% 12% 21% 5%	4351
November	1st to 10th	Night	60% 6% 12% 16% 6% 1	2731
	11th to 20th	Night	71% 6% 9% 10% 4	2800
	21st to end	Night	67% 8% 12% 9% 4	2800
December	1st to 10th	Night	70% 8% 10% 9% 2	2800
	11th to 20th	Night	67% 7% 10% 11% 4	3606
	21st to end	Night	76% 5% 7% 9% 3	5277

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% 15% 43% 22% 8%	270
	11th to 20th	Day	14% 10% 44% 26% 6% 1	270
	21st to end	Day	15% 10% 42% 23% 9%	297
February	1st to 10th	Day	16% 15% 44% 17% 7% 1	270
	11th to 20th	Day	15% 24% 34% 16% 9% 3	270
	21st to end	Day	19% 19% 43% 14% 4	225
March	1st to 10th	Day	14% 16% 40% 21% 7% 1	270
	11th to 20th	Day	13% 21% 33% 21% 9% 3	270
	21st to end	Day	19% 17% 34% 20% 8% 2	353
April	1st to 10th	Day	22% 15% 36% 18% 9%	460
	11th to 20th	Day	23% 16% 29% 23% 7% 2	526
	21st to end	Day	22% 14% 30% 21% 11% 1	650
May	1st to 10th	Day	22% 18% 34% 17% 7% 2	653
	11th to 20th	Day	21% 12% 31% 23% 10% 2	675
	21st to end	Day	23% 12% 27% 29% 7% 2	734
June	1st to 10th	Day	17% 14% 31% 24% 12% 3	680
	11th to 20th	Day	18% 14% 36% 23% 9% 2	680
	21st to end	Day	19% 8% 31% 27% 10% 5%	680
July	1st to 10th	Day	12% 9% 28% 29% 14% 7%	671
	11th to 20th	Day	14% 11% 28% 25% 17% 5%	668
	21st to end	Day	9% 9% 29% 28% 17% 6%	739
August	1st to 10th	Day	12% 9% 29% 32% 16% 3	676
	11th to 20th	Day	14% 8% 26% 28% 18% 6%	665
	21st to end	Day	16% 10% 29% 26% 15% 3	677
September	1st to 10th	Day	15% 13% 33% 25% 12% 2	490
	11th to 20th	Day	19% 12% 31% 26% 10% 2	490
	21st to end	Day	24% 18% 30% 18% 9%	301
October	1st to 10th	Day	25% 16% 32% 16% 10% 1	300
	11th to 20th	Day	21% 19% 40% 17% 2	300
	21st to end	Day	31% 21% 32% 13% 2 1	330
November	1st to 10th	Day	22% 20% 31% 20% 5% 1	300
	11th to 20th	Day	26% 19% 34% 17% 4	300
	21st to end	Day	28% 19% 35% 15% 3	300
December	1st to 10th	Day	21% 16% 39% 19% 5%	300
	11th to 20th	Day	21% 18% 41% 18% 1	300
	21st to end	Day	20% 15% 41% 18% 5% 2	306
January	1st to 10th	Night	13% 14% 38% 23% 10% 1	950
	11th to 20th	Night	17% 10% 41% 24% 7% 1	950
	21st to end	Night	17% 11% 38% 27% 6%	1045
February	1st to 10th	Night	13% 11% 38% 29% 9% 1	950
	11th to 20th	Night	13% 14% 36% 25% 9% 3	929
	21st to end	Night	14% 12% 37% 26% 10% 3	760
March	1st to 10th	Night	16% 15% 32% 28% 10% 1	694
	11th to 20th	Night	15% 15% 36% 27% 6% 1	570
	21st to end	Night	22% 10% 31% 24% 11% 3	627
April	1st to 10th	Night	19% 12% 34% 27% 8% 1	570
	11th to 20th	Night	20% 11% 34% 27% 7% 1	563
	21st to end	Night	25% 10% 23% 33% 9% 1	570
May	1st to 10th	Night	20% 11% 34% 27% 7% 1	570
	11th to 20th	Night	18% 10% 35% 27% 9% 1	561
	21st to end	Night	19% 9% 30% 33% 9%	617
June	1st to 10th	Night	18% 7% 29% 33% 12% 1	570
	11th to 20th	Night	13% 9% 31% 35% 12%	570
	21st to end	Night	15% 6% 28% 35% 15% 2	570
July	1st to 10th	Night	8% 3 27% 40% 20% 1	555
	11th to 20th	Night	9% 7% 30% 35% 18% 1	552
	21st to end	Night	8% 5% 28% 35% 22% 2	624
August	1st to 10th	Night	10% 4 29% 39% 18% 1	567
	11th to 20th	Night	14% 6% 20% 38% 18% 4	564
	21st to end	Night	14% 7% 29% 32% 16% 1	627
September	1st to 10th	Night	15% 6% 29% 33% 16% 1	570
	11th to 20th	Night	18% 7% 31% 27% 15% 1	570
	21st to end	Night	23% 11% 29% 25% 12% 1	660
October	1st to 10th	Night	24% 12% 32% 25% 6% 1	760
	11th to 20th	Night	26% 15% 30% 22% 6%	760
	21st to end	Night	27% 14% 33% 22% 4	845
November	1st to 10th	Night	22% 14% 32% 25% 5% 1	975
	11th to 20th	Night	23% 16% 32% 21% 6% 1	1000
	21st to end	Night	22% 18% 39% 17% 4	1000
December	1st to 10th	Night	18% 13% 38% 25% 6% 1	1000
	11th to 20th	Night	20% 12% 39% 22% 6% 1	1000
	21st to end	Night	25% 12% 30% 25% 7% 1	1063

Page generated at 2024-12-21 03:13:50. Version ac07

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