Lake Superior Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Superior Provincial Park clear sky chart from 2005-11-06 to 2025-05-26.

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	16% 12% 4 9% 5% 4 4 3 5% 7% 31%	113545
	Night	15% 15% 6% 11% 5% 4 4 3 5% 6% 26%	115877
Transparency	Day	52% 7% 13% 19% 9% 1	117038
	Night	57% 7% 11% 16% 7% 1	120548
Seeing	Day	21% 12% 29% 26% 11% 2	16250
	Night	22% 11% 29% 26% 10% 1	25767

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% 18% 10% 14% 8% 5% 6% 4 6% 6% 16%	3358
	11th to 20th	Day	8% 14% 6% 17% 6% 6% 5% 4 7% 7% 19%	3589
	21st to end	Day	6% 20% 11% 18% 6% 6% 5% 4 6% 5% 14%	3982
February	1st to 10th	Day	7% 16% 5% 14% 11% 9% 6% 3 5% 6% 18%	1671
	11th to 20th	Day	9% 17% 6% 12% 10% 6% 5% 4 4 5% 22%	1841
	21st to end	Day	8% 17% 8% 15% 6% 5% 4 3 6% 6% 21%	1650
March	1st to 10th	Day	14% 12% 3 11% 5% 4 4 4 5% 8% 29%	4478
	11th to 20th	Day	14% 17% 5% 9% 6% 5% 4 3 5% 7% 26%	4905
	21st to end	Day	18% 15% 7% 12% 5% 3 4 2 3 5% 26%	5596
April	1st to 10th	Day	16% 14% 5% 8% 5% 3 4 3 5% 7% 30%	2400
	11th to 20th	Day	19% 13% 4 7% 4 4 3 3 5% 6% 32%	2551
	21st to end	Day	16% 12% 4 7% 5% 4 4 4 6% 7% 32%	2600
May	1st to 10th	Day	17% 9% 3 7% 4 4 4 3 5% 6% 38%	4238
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 5% 7% 41%	4494
	21st to end	Day	19% 7% 2 6% 4 4 4 3 5% 7% 39%	5261
June	1st to 10th	Day	18% 7% 2 6% 5% 5% 6% 4 6% 8% 33%	2850
	11th to 20th	Day	16% 7% 3 6% 4 5% 4 4 6% 9% 35%	2850
	21st to end	Day	18% 7% 2 6% 4 4 5% 4 5% 8% 37%	2850
July	1st to 10th	Day	21% 8% 2 6% 4 4 4 3 5% 6% 37%	4760
	11th to 20th	Day	13% 8% 2 5% 4 3 4 3 6% 8% 44%	4521
	21st to end	Day	15% 6% 2 6% 3 4 4 3 5% 8% 44%	4814
August	1st to 10th	Day	12% 6% 2 6% 4 4 4 5% 7% 10% 41%	4313
	11th to 20th	Day	15% 6% 3 5% 3 4 4 3 5% 8% 44%	4044
	21st to end	Day	20% 7% 2 6% 3 3 3 3 4 5% 43%	4514
September	1st to 10th	Day	21% 7% 2 6% 4 3 3 3 5% 7% 38%	2241
	11th to 20th	Day	22% 6% 2 4 4 4 4 4 6% 7% 38%	2090
	21st to end	Day	24% 7% 3 7% 4 3 4 2 5% 7% 34%	2090
October	1st to 10th	Day	22% 11% 3 7% 3 4 3 3 6% 5% 31%	2047
	11th to 20th	Day	25% 18% 4 9% 6% 5% 3 3 5% 6% 18%	1787
	21st to end	Day	25% 19% 4 8% 6% 4 4 4 4 5% 19%	1881
November	1st to 10th	Day	21% 22% 4 8% 4 3 4 4 5% 5% 20%	1762
	11th to 20th	Day	18% 19% 7% 11% 5% 4 4 4 4 6% 17%	1667
	21st to end	Day	18% 27% 7% 10% 6% 4 5% 4 4 5% 11%	1473
December	1st to 10th	Day	12% 25% 11% 16% 7% 5% 3 2 4 4 11%	2280
	11th to 20th	Day	10% 20% 7% 16% 8% 6% 5% 4 5% 5% 14%	2621
	21st to end	Day	20% 22% 8% 13% 4 3 3 2 3 4 17%	3476
January	1st to 10th	Night	8% 18% 9% 15% 6% 5% 5% 4 5% 6% 19%	6606
	11th to 20th	Night	7% 19% 9% 17% 8% 5% 5% 3 5% 6% 17%	6316
	21st to end	Night	7% 17% 12% 19% 8% 6% 6% 3 4 5% 13%	6996
February	1st to 10th	Night	8% 18% 7% 16% 13% 6% 5% 4 5% 4 15%	2727
	11th to 20th	Night	10% 14% 7% 16% 8% 5% 5% 4 6% 5% 19%	2443
	21st to end	Night	9% 18% 7% 12% 7% 6% 5% 3 5% 5% 22%	1980
March	1st to 10th	Night	15% 12% 4 10% 4 3 4 3 6% 8% 31%	5362
	11th to 20th	Night	15% 16% 5% 9% 4 4 4 4 5% 6% 27%	5053
	21st to end	Night	18% 15% 7% 12% 5% 4 3 2 4 5% 26%	5377
April	1st to 10th	Night	18% 13% 4 7% 5% 4 4 4 5% 6% 31%	2000
	11th to 20th	Night	19% 13% 4 7% 5% 4 4 3 4 5% 33%	1797
	21st to end	Night	18% 11% 3 6% 5% 3 4 3 4 6% 36%	1800
May	1st to 10th	Night	19% 9% 4 6% 4 3 3 2 4 5% 40%	2923
	11th to 20th	Night	15% 8% 2 7% 4 4 4 3 6% 7% 39%	2612
	21st to end	Night	17% 9% 4 7% 4 4 4 3 4 5% 39%	2442
June	1st to 10th	Night	17% 7% 2 6% 5% 4 5% 3 5% 8% 38%	1330
	11th to 20th	Night	18% 10% 3 7% 3 3 3 3 5% 7% 36%	1330
	21st to end	Night	15% 7% 2 7% 5% 5% 4 4 6% 7% 39%	1330
July	1st to 10th	Night	17% 8% 3 8% 5% 3 4 4 5% 8% 36%	2210
	11th to 20th	Night	12% 6% 2 7% 4 4 4 4 5% 8% 44%	2432
	21st to end	Night	16% 7% 3 7% 4 4 3 3 5% 7% 42%	2750
August	1st to 10th	Night	14% 9% 3 7% 5% 5% 5% 4 5% 7% 35%	2609
	11th to 20th	Night	14% 5% 2 6% 4 4 4 3 5% 8% 47%	2785
	21st to end	Night	16% 7% 2 5% 4 3 3 2 5% 5% 48%	3140
September	1st to 10th	Night	16% 8% 3 6% 4 3 4 3 5% 7% 43%	1919
	11th to 20th	Night	20% 6% 2 5% 4 4 3 3 5% 8% 39%	2090
	21st to end	Night	24% 8% 2 5% 3 3 3 3 4 7% 36%	2090
October	1st to 10th	Night	24% 10% 3 6% 4 4 4 3 5% 5% 33%	2133
	11th to 20th	Night	26% 15% 3 7% 5% 4 3 3 4 6% 24%	2389
	21st to end	Night	25% 19% 3 8% 4 4 4 3 4 5% 20%	2717
November	1st to 10th	Night	22% 19% 5% 8% 4 4 4 3 4 5% 22%	2536
	11th to 20th	Night	20% 21% 6% 11% 5% 4 4 3 5% 5% 16%	2730
	21st to end	Night	17% 23% 8% 11% 5% 4 5% 3 5% 5% 14%	2925
December	1st to 10th	Night	12% 24% 8% 13% 6% 5% 4 4 4 5% 15%	4910
	11th to 20th	Night	10% 22% 8% 19% 7% 4 4 3 3 4 16%	5586
	21st to end	Night	17% 22% 8% 14% 5% 4 4 2 4 5% 15%	7502

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	66% 7% 10% 11% 3 3	3359
	11th to 20th	Day	63% 7% 11% 11% 9%	3620
	21st to end	Day	69% 9% 8% 8% 7%	3982
February	1st to 10th	Day	66% 8% 10% 10% 5%	1671
	11th to 20th	Day	63% 7% 11% 10% 7% 1	1850
	21st to end	Day	63% 5% 10% 13% 8% 1	1650
March	1st to 10th	Day	52% 6% 14% 13% 13% 3	4480
	11th to 20th	Day	58% 5% 12% 15% 9% 1	4905
	21st to end	Day	63% 4 10% 12% 9% 2	5596
April	1st to 10th	Day	53% 6% 12% 18% 10% 1	2400
	11th to 20th	Day	52% 4 11% 21% 11% 1	2551
	21st to end	Day	48% 6% 11% 19% 13% 3	2600
May	1st to 10th	Day	43% 7% 10% 26% 12% 2	4250
	11th to 20th	Day	41% 8% 13% 24% 13% 1	4498
	21st to end	Day	43% 7% 13% 20% 15% 2	5261
June	1st to 10th	Day	46% 8% 13% 20% 11% 2	2850
	11th to 20th	Day	43% 8% 14% 22% 12% 1	2850
	21st to end	Day	44% 8% 14% 22% 10% 1	2850
July	1st to 10th	Day	47% 7% 15% 22% 9% 1	4686
	11th to 20th	Day	38% 6% 21% 25% 9% 1	4443
	21st to end	Day	37% 7% 14% 32% 10%	4662
August	1st to 10th	Day	35% 8% 20% 29% 7%	4298
	11th to 20th	Day	38% 5% 17% 31% 9%	4083
	21st to end	Day	43% 6% 15% 25% 11% 1	4513
September	1st to 10th	Day	46% 6% 16% 23% 10%	2241
	11th to 20th	Day	44% 7% 20% 24% 5%	2090
	21st to end	Day	50% 6% 17% 20% 6% 1	2090
October	1st to 10th	Day	43% 6% 17% 22% 11%	3398
	11th to 20th	Day	57% 6% 15% 18% 4	2951
	21st to end	Day	68% 5% 11% 11% 5%	3081
November	1st to 10th	Day	66% 6% 11% 13% 3	1762
	11th to 20th	Day	67% 9% 11% 9% 3	1667
	21st to end	Day	77% 8% 7% 6% 2	1473
December	1st to 10th	Day	77% 6% 10% 6% 1	2280
	11th to 20th	Day	71% 7% 10% 9% 3	2621
	21st to end	Day	72% 6% 7% 10% 5%	3476
January	1st to 10th	Night	64% 8% 9% 10% 5% 3	6606
	11th to 20th	Night	68% 7% 9% 10% 6%	6360
	21st to end	Night	72% 9% 5% 8% 5% 1	6996
February	1st to 10th	Night	71% 7% 9% 8% 4	2727
	11th to 20th	Night	65% 8% 12% 11% 4	2445
	21st to end	Night	62% 7% 11% 13% 7%	1980
March	1st to 10th	Night	51% 6% 14% 14% 14% 2	5373
	11th to 20th	Night	55% 5% 16% 16% 7% 1	5054
	21st to end	Night	60% 7% 9% 14% 9% 1	5377
April	1st to 10th	Night	53% 6% 10% 18% 12% 1	2000
	11th to 20th	Night	53% 4 9% 22% 11% 2	1797
	21st to end	Night	49% 4 12% 18% 15% 3	1800
May	1st to 10th	Night	45% 5% 8% 24% 15% 2	2930
	11th to 20th	Night	43% 7% 12% 29% 9% 1	2613
	21st to end	Night	47% 7% 11% 18% 13% 5%	2443
June	1st to 10th	Night	43% 7% 12% 20% 16% 2	1330
	11th to 20th	Night	45% 8% 11% 20% 14% 2	1330
	21st to end	Night	43% 9% 14% 24% 10% 1	1330
July	1st to 10th	Night	45% 6% 14% 26% 8%	2175
	11th to 20th	Night	37% 6% 17% 29% 10% 1	2388
	21st to end	Night	41% 6% 11% 25% 17% 1	2662
August	1st to 10th	Night	45% 7% 13% 26% 8%	2600
	11th to 20th	Night	36% 6% 18% 30% 10%	2812
	21st to end	Night	38% 5% 11% 31% 14%	3140
September	1st to 10th	Night	41% 7% 14% 27% 10% 1	1919
	11th to 20th	Night	43% 9% 17% 24% 7%	2090
	21st to end	Night	47% 7% 17% 22% 7%	2090
October	1st to 10th	Night	42% 6% 14% 28% 10%	3562
	11th to 20th	Night	49% 6% 16% 25% 4	3964
	21st to end	Night	67% 8% 14% 9% 3	4467
November	1st to 10th	Night	65% 6% 10% 14% 4	2536
	11th to 20th	Night	71% 8% 9% 9% 3	2730
	21st to end	Night	72% 10% 12% 5% 1	2925
December	1st to 10th	Night	72% 7% 12% 7% 2	4910
	11th to 20th	Night	73% 6% 8% 9% 4 1	5585
	21st to end	Night	71% 8% 7% 10% 4	7502

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	20% 17% 34% 19% 9% 2	243
	11th to 20th	Day	16% 15% 36% 24% 7% 1	300
	21st to end	Day	16% 12% 38% 26% 7%	330
February	1st to 10th	Day	20% 21% 34% 19% 5% 1	300
	11th to 20th	Day	19% 18% 40% 17% 5% 1	300
	21st to end	Day	20% 24% 40% 14% 1	249
March	1st to 10th	Day	17% 18% 41% 19% 5%	300
	11th to 20th	Day	21% 16% 33% 23% 6% 1	464
	21st to end	Day	22% 18% 31% 21% 6% 1	550
April	1st to 10th	Day	21% 12% 35% 25% 5% 1	500
	11th to 20th	Day	26% 13% 32% 18% 10% 2	492
	21st to end	Day	22% 12% 33% 22% 9% 2	500
May	1st to 10th	Day	20% 11% 31% 25% 10% 3	503
	11th to 20th	Day	20% 8% 32% 27% 10% 3	685
	21st to end	Day	21% 9% 29% 29% 11% 2	760
June	1st to 10th	Day	20% 8% 32% 30% 10% 1	680
	11th to 20th	Day	19% 9% 29% 29% 12% 2	680
	21st to end	Day	20% 7% 26% 30% 15% 3	680
July	1st to 10th	Day	16% 6% 26% 36% 14% 2	671
	11th to 20th	Day	16% 7% 22% 35% 16% 3	668
	21st to end	Day	19% 4 23% 35% 16% 4	739
August	1st to 10th	Day	12% 9% 24% 32% 20% 4	618
	11th to 20th	Day	16% 5% 17% 33% 23% 6%	479
	21st to end	Day	26% 8% 20% 29% 13% 5%	539
September	1st to 10th	Day	23% 11% 25% 21% 16% 4	490
	11th to 20th	Day	22% 8% 26% 28% 13% 3	490
	21st to end	Day	27% 9% 20% 27% 16% 1	490
October	1st to 10th	Day	29% 14% 21% 25% 10% 1	490
	11th to 20th	Day	33% 14% 31% 19% 4	377
	21st to end	Day	35% 14% 32% 14% 5%	330
November	1st to 10th	Day	31% 16% 29% 19% 5%	300
	11th to 20th	Day	24% 26% 31% 13% 6%	233
	21st to end	Day	26% 22% 36% 15% 2	200
December	1st to 10th	Day	25% 24% 27% 16% 10% 1	200
	11th to 20th	Day	21% 18% 41% 15% 6% 1	200
	21st to end	Day	27% 19% 34% 12% 7%	220
January	1st to 10th	Night	20% 16% 36% 23% 5%	1000
	11th to 20th	Night	19% 15% 35% 25% 6% 1	1000
	21st to end	Night	19% 11% 34% 28% 7% 1	1100
February	1st to 10th	Night	17% 13% 40% 25% 5% 1	927
	11th to 20th	Night	16% 14% 38% 23% 8% 1	783
	21st to end	Night	19% 14% 35% 28% 5%	660
March	1st to 10th	Night	16% 10% 38% 28% 8% 1	800
	11th to 20th	Night	20% 12% 35% 25% 6% 1	800
	21st to end	Night	17% 10% 33% 29% 9% 1	841
April	1st to 10th	Night	26% 8% 30% 27% 8% 2	600
	11th to 20th	Night	26% 8% 25% 31% 10% 1	593
	21st to end	Night	21% 9% 28% 27% 15% 1	600
May	1st to 10th	Night	19% 7% 24% 39% 10% 1	600
	11th to 20th	Night	21% 7% 25% 29% 15% 3	581
	21st to end	Night	17% 7% 26% 34% 16% 1	423
June	1st to 10th	Night	17% 5% 24% 38% 15% 1	380
	11th to 20th	Night	20% 8% 20% 37% 14% 1	380
	21st to end	Night	16% 5% 22% 32% 22% 3	380
July	1st to 10th	Night	14% 3 21% 38% 22% 2	370
	11th to 20th	Night	17% 3 15% 38% 25% 2	497
	21st to end	Night	21% 4 15% 35% 22% 4	624
August	1st to 10th	Night	18% 5% 17% 34% 24% 2	567
	11th to 20th	Night	14% 4 14% 37% 27% 4	564
	21st to end	Night	21% 4 22% 31% 18% 3	627
September	1st to 10th	Night	18% 6% 25% 28% 18% 4	589
	11th to 20th	Night	22% 6% 24% 31% 14% 2	760
	21st to end	Night	27% 8% 19% 29% 14% 2	760
October	1st to 10th	Night	29% 8% 27% 22% 13% 1	760
	11th to 20th	Night	35% 12% 26% 20% 6%	760
	21st to end	Night	36% 13% 25% 22% 4	836
November	1st to 10th	Night	32% 14% 30% 19% 5%	780
	11th to 20th	Night	30% 17% 29% 18% 6% 1	800
	21st to end	Night	28% 16% 33% 19% 4	925
December	1st to 10th	Night	25% 14% 34% 20% 6% 1	1000
	11th to 20th	Night	22% 17% 37% 17% 6% 1	1000
	21st to end	Night	28% 16% 31% 19% 6%	1100

Page generated at 2025-05-23 09:20:59. Version ac07

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