Sioux Lookout
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sioux Lookout clear sky chart from 2005-11-06 to 2026-07-01.

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% 5% 5% 5% 4 5% 6% 31%	138132
	Night	12% 13% 5% 11% 6% 6% 5% 4 5% 5% 27%	134564
Transparency	Day	52% 6% 12% 21% 9% 1	141546
	Night	57% 5% 11% 18% 8% 1	139237
Seeing	Day	19% 13% 33% 23% 9% 2	18562
	Night	19% 11% 31% 27% 10% 1	28496

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% 14% 8% 20% 8% 11% 8% 3 4 4 15%	4124
	11th to 20th	Day	6% 14% 7% 19% 7% 7% 9% 9% 8% 3 10%	4112
	21st to end	Day	6% 13% 7% 18% 8% 6% 8% 6% 8% 6% 15%	5156
February	1st to 10th	Day	8% 14% 6% 12% 7% 8% 9% 7% 6% 5% 19%	1848
	11th to 20th	Day	7% 11% 4 12% 8% 7% 7% 8% 6% 5% 25%	1844
	21st to end	Day	5% 14% 5% 15% 8% 6% 5% 5% 6% 6% 25%	1604
March	1st to 10th	Day	9% 13% 6% 11% 5% 5% 4 3 4 5% 36%	4641
	11th to 20th	Day	9% 11% 6% 15% 7% 6% 6% 3 4 5% 29%	5090
	21st to end	Day	12% 16% 5% 9% 5% 5% 4 4 4 6% 29%	5837
April	1st to 10th	Day	13% 12% 4 9% 6% 4 4 4 5% 7% 33%	2520
	11th to 20th	Day	15% 12% 4 9% 5% 4 3 4 6% 6% 33%	2560
	21st to end	Day	15% 10% 3 8% 4 4 5% 5% 5% 6% 35%	2862
May	1st to 10th	Day	11% 11% 4 7% 5% 5% 5% 3 5% 7% 38%	8241
	11th to 20th	Day	16% 10% 3 7% 5% 4 4 4 5% 7% 35%	8222
	21st to end	Day	14% 6% 2 5% 4 4 4 3 5% 7% 47%	9205
June	1st to 10th	Day	17% 6% 2 6% 5% 4 5% 5% 7% 8% 33%	3150
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 5% 7% 9% 33%	3150
	21st to end	Day	16% 6% 2 7% 5% 5% 6% 5% 7% 8% 33%	3150
July	1st to 10th	Day	10% 6% 2 7% 4 5% 5% 4 6% 8% 43%	6800
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 40%	6800
	21st to end	Day	15% 7% 3 6% 4 4 4 4 6% 8% 40%	7018
August	1st to 10th	Day	18% 5% 2 6% 4 5% 4 4 6% 8% 37%	4563
	11th to 20th	Day	10% 5% 2 5% 3 4 5% 5% 6% 10% 45%	4277
	21st to end	Day	15% 7% 3 6% 4 4 4 4 6% 9% 39%	4521
September	1st to 10th	Day	17% 8% 2 7% 5% 5% 5% 4 4 6% 39%	2400
	11th to 20th	Day	19% 9% 3 7% 6% 5% 5% 4 5% 7% 29%	2400
	21st to end	Day	23% 10% 3 6% 4 4 3 3 4 6% 34%	2103
October	1st to 10th	Day	19% 15% 3 9% 5% 5% 4 3 5% 6% 24%	2000
	11th to 20th	Day	18% 21% 4 11% 6% 4 4 2 5% 5% 19%	2000
	21st to end	Day	21% 22% 7% 12% 4 3 3 3 3 4 19%	1981
November	1st to 10th	Day	16% 21% 5% 12% 6% 5% 4 2 5% 4 20%	1647
	11th to 20th	Day	18% 21% 8% 15% 7% 5% 4 2 3 4 14%	1680
	21st to end	Day	15% 19% 8% 22% 8% 5% 4 2 3 3 11%	1680
December	1st to 10th	Day	12% 17% 7% 19% 14% 9% 5% 4 3 3 7%	2662
	11th to 20th	Day	10% 14% 5% 17% 7% 8% 8% 5% 5% 4 17%	2709
	21st to end	Day	14% 20% 8% 17% 7% 6% 5% 3 4 5% 11%	3575
January	1st to 10th	Night	5% 15% 8% 19% 7% 8% 7% 4 5% 4 18%	8800
	11th to 20th	Night	6% 14% 7% 17% 10% 9% 9% 8% 7% 3 11%	8789
	21st to end	Night	6% 15% 7% 14% 8% 8% 7% 7% 9% 6% 14%	9058
February	1st to 10th	Night	8% 14% 5% 10% 8% 9% 10% 6% 6% 6% 19%	2770
	11th to 20th	Night	8% 13% 4 9% 7% 7% 8% 7% 6% 6% 26%	2663
	21st to end	Night	6% 14% 5% 12% 7% 7% 6% 5% 6% 6% 25%	2202
March	1st to 10th	Night	10% 13% 4 10% 6% 5% 5% 4 5% 6% 33%	5464
	11th to 20th	Night	9% 14% 6% 12% 8% 8% 5% 3 5% 5% 25%	5089
	21st to end	Night	15% 18% 4 8% 4 4 4 3 5% 6% 28%	5336
April	1st to 10th	Night	14% 12% 3 9% 5% 4 4 3 4 5% 36%	2100
	11th to 20th	Night	14% 12% 3 8% 4 4 4 3 6% 5% 36%	2007
	21st to end	Night	14% 11% 4 8% 6% 5% 4 5% 5% 5% 34%	1757
May	1st to 10th	Night	12% 10% 3 7% 4 4 5% 4 5% 6% 41%	4688
	11th to 20th	Night	19% 9% 2 6% 4 3 4 3 4 7% 37%	4670
	21st to end	Night	17% 6% 2 4 3 3 3 3 5% 7% 48%	5000
June	1st to 10th	Night	18% 8% 2 6% 3 5% 4 4 6% 8% 37%	1470
	11th to 20th	Night	14% 7% 2 6% 5% 5% 4 4 5% 8% 40%	1470
	21st to end	Night	14% 5% 2 6% 5% 5% 5% 4 6% 8% 39%	1470
July	1st to 10th	Night	11% 6% 2 5% 4 3 4 4 5% 8% 48%	3180
	11th to 20th	Night	12% 6% 2 5% 4 4 4 4 7% 8% 43%	3180
	21st to end	Night	11% 7% 3 6% 4 4 4 4 5% 9% 43%	3855
August	1st to 10th	Night	17% 6% 3 6% 3 4 4 3 5% 7% 42%	2597
	11th to 20th	Night	12% 5% 2 6% 4 3 4 4 6% 8% 47%	2779
	21st to end	Night	18% 6% 2 6% 4 4 3 4 5% 8% 41%	3382
September	1st to 10th	Night	16% 6% 3 6% 4 5% 4 4 6% 7% 41%	2000
	11th to 20th	Night	20% 8% 3 7% 4 3 4 3 5% 5% 38%	2000
	21st to end	Night	20% 10% 3 6% 5% 3 4 3 5% 5% 36%	2274
October	1st to 10th	Night	19% 12% 4 8% 4 4 5% 3 6% 6% 30%	2400
	11th to 20th	Night	22% 16% 4 10% 5% 4 4 3 4 6% 25%	2400
	21st to end	Night	21% 18% 5% 11% 6% 4 4 3 4 5% 20%	2857
November	1st to 10th	Night	16% 20% 6% 11% 5% 5% 4 3 3 4 21%	2871
	11th to 20th	Night	18% 18% 6% 15% 8% 5% 5% 3 3 4 14%	2940
	21st to end	Night	15% 21% 8% 15% 9% 6% 4 3 3 4 11%	2940
December	1st to 10th	Night	10% 20% 10% 21% 13% 6% 5% 3 2 3 8%	4743
	11th to 20th	Night	10% 14% 6% 15% 9% 9% 8% 5% 5% 5% 15%	5718
	21st to end	Night	12% 20% 8% 18% 8% 6% 5% 3 3 3 14%	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	74% 4 4 10% 8%	4125
	11th to 20th	Day	73% 4 6% 14% 4	4140
	21st to end	Day	67% 4 8% 13% 8%	5156
February	1st to 10th	Day	64% 6% 9% 13% 8%	1848
	11th to 20th	Day	56% 7% 10% 20% 7% 1	1853
	21st to end	Day	58% 5% 10% 17% 9% 1	1604
March	1st to 10th	Day	50% 6% 11% 15% 14% 4	4643
	11th to 20th	Day	57% 5% 8% 18% 11% 1	5090
	21st to end	Day	55% 6% 8% 19% 12% 1	5837
April	1st to 10th	Day	51% 5% 9% 19% 13% 2	2520
	11th to 20th	Day	52% 5% 10% 22% 11% 1	2560
	21st to end	Day	49% 6% 10% 23% 10% 2	2862
May	1st to 10th	Day	44% 7% 9% 28% 12%	8250
	11th to 20th	Day	47% 6% 10% 20% 15% 1	8226
	21st to end	Day	36% 6% 10% 27% 19% 1	9205
June	1st to 10th	Day	45% 9% 13% 21% 11% 1	3150
	11th to 20th	Day	45% 8% 13% 21% 12%	3150
	21st to end	Day	44% 9% 16% 22% 7% 1	3150
July	1st to 10th	Day	38% 7% 17% 29% 8%	6727
	11th to 20th	Day	39% 7% 21% 30% 4	6719
	21st to end	Day	42% 6% 16% 30% 6%	6817
August	1st to 10th	Day	44% 7% 15% 27% 8%	4548
	11th to 20th	Day	33% 8% 23% 33% 4	4319
	21st to end	Day	41% 7% 18% 29% 5%	4520
September	1st to 10th	Day	46% 6% 14% 27% 6%	2400
	11th to 20th	Day	52% 8% 17% 19% 3	2400
	21st to end	Day	52% 6% 15% 21% 5%	2103
October	1st to 10th	Day	51% 6% 14% 22% 7%	3260
	11th to 20th	Day	58% 4 16% 17% 5%	3240
	21st to end	Day	62% 5% 18% 13% 1	3170
November	1st to 10th	Day	68% 5% 12% 9% 5% 1	1647
	11th to 20th	Day	77% 4 7% 8% 3	1680
	21st to end	Day	79% 4 8% 6% 2	1680
December	1st to 10th	Day	83% 4 6% 5% 2	2662
	11th to 20th	Day	69% 5% 7% 10% 8%	2710
	21st to end	Day	75% 4 6% 11% 4	3575
January	1st to 10th	Night	69% 4 7% 12% 7% 1	8800
	11th to 20th	Night	75% 4 6% 11% 4	8836
	21st to end	Night	66% 4 9% 16% 4	9058
February	1st to 10th	Night	64% 5% 9% 15% 7%	2770
	11th to 20th	Night	55% 7% 11% 20% 7%	2664
	21st to end	Night	57% 7% 10% 19% 7% 1	2202
March	1st to 10th	Night	50% 5% 9% 13% 19% 3	5475
	11th to 20th	Night	60% 7% 10% 14% 8% 1	5090
	21st to end	Night	57% 5% 7% 18% 13% 1	5336
April	1st to 10th	Night	49% 5% 8% 20% 16% 2	2100
	11th to 20th	Night	47% 5% 11% 22% 14% 1	2007
	21st to end	Night	50% 5% 9% 22% 12% 2	1757
May	1st to 10th	Night	42% 7% 10% 28% 13%	4695
	11th to 20th	Night	46% 6% 12% 23% 12% 1	4671
	21st to end	Night	35% 6% 11% 29% 17% 2	5001
June	1st to 10th	Night	44% 7% 14% 21% 13% 1	1470
	11th to 20th	Night	41% 9% 9% 25% 16% 1	1470
	21st to end	Night	39% 9% 16% 27% 8% 1	1470
July	1st to 10th	Night	35% 7% 18% 32% 9%	3145
	11th to 20th	Night	37% 6% 20% 30% 7% 1	3138
	21st to end	Night	38% 7% 18% 30% 7%	3742
August	1st to 10th	Night	41% 6% 14% 31% 8% 1	2588
	11th to 20th	Night	33% 7% 20% 33% 7%	2803
	21st to end	Night	42% 5% 20% 27% 5% 1	3382
September	1st to 10th	Night	42% 7% 17% 25% 9%	2000
	11th to 20th	Night	47% 7% 17% 25% 4	2000
	21st to end	Night	49% 6% 17% 22% 5%	2274
October	1st to 10th	Night	47% 7% 14% 25% 7%	3920
	11th to 20th	Night	56% 5% 14% 21% 4	3899
	21st to end	Night	61% 6% 16% 14% 3	4619
November	1st to 10th	Night	67% 6% 10% 13% 4	2871
	11th to 20th	Night	75% 5% 9% 8% 3	2940
	21st to end	Night	79% 4 8% 7% 2	2940
December	1st to 10th	Night	84% 3 6% 5% 2	4743
	11th to 20th	Night	70% 6% 10% 10% 5%	5716
	21st to end	Night	76% 4 5% 13% 2	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	15% 14% 38% 25% 8% 1	330
	11th to 20th	Day	14% 11% 36% 30% 8% 1	330
	21st to end	Day	14% 10% 40% 26% 9% 1	363
February	1st to 10th	Day	16% 15% 43% 20% 6% 1	330
	11th to 20th	Day	13% 18% 35% 23% 10% 1	330
	21st to end	Day	14% 21% 40% 19% 4 2	273
March	1st to 10th	Day	14% 15% 43% 22% 5% 1	330
	11th to 20th	Day	10% 20% 44% 20% 4 2	330
	21st to end	Day	19% 14% 35% 20% 10% 2	473
April	1st to 10th	Day	19% 14% 35% 22% 9% 1	540
	11th to 20th	Day	25% 16% 28% 22% 10%	598
	21st to end	Day	21% 11% 33% 24% 9% 2	750
May	1st to 10th	Day	19% 15% 33% 23% 8% 2	753
	11th to 20th	Day	22% 14% 30% 23% 9% 1	775
	21st to end	Day	22% 10% 32% 24% 11% 2	844
June	1st to 10th	Day	20% 12% 32% 24% 10% 3	780
	11th to 20th	Day	18% 15% 36% 22% 7% 2	780
	21st to end	Day	17% 11% 31% 24% 13% 4	780
July	1st to 10th	Day	12% 12% 33% 24% 13% 5%	722
	11th to 20th	Day	16% 13% 29% 24% 15% 3	718
	21st to end	Day	12% 9% 31% 29% 13% 6%	794
August	1st to 10th	Day	14% 9% 31% 30% 13% 3	726
	11th to 20th	Day	16% 7% 27% 29% 17% 4	715
	21st to end	Day	19% 10% 31% 25% 14% 1	714
September	1st to 10th	Day	21% 13% 30% 22% 11% 3	530
	11th to 20th	Day	24% 11% 28% 27% 8% 1	530
	21st to end	Day	26% 12% 32% 19% 9% 2	388
October	1st to 10th	Day	25% 18% 29% 22% 4 2	330
	11th to 20th	Day	26% 16% 35% 19% 3 1	330
	21st to end	Day	33% 15% 37% 12% 3	363
November	1st to 10th	Day	26% 16% 33% 18% 5% 1	330
	11th to 20th	Day	28% 19% 33% 15% 5% 1	330
	21st to end	Day	25% 21% 38% 14% 2	330
December	1st to 10th	Day	15% 16% 41% 23% 3 2	330
	11th to 20th	Day	19% 16% 38% 23% 4 1	330
	21st to end	Day	18% 15% 33% 24% 6% 3	363
January	1st to 10th	Night	14% 14% 36% 27% 8% 1	1050
	11th to 20th	Night	16% 11% 38% 28% 6% 1	1050
	21st to end	Night	16% 11% 36% 29% 8% 1	1155
February	1st to 10th	Night	15% 12% 36% 28% 8% 1	1050
	11th to 20th	Night	13% 12% 32% 28% 12% 2	1029
	21st to end	Night	11% 13% 33% 29% 12% 3	818
March	1st to 10th	Night	16% 13% 34% 27% 9% 1	835
	11th to 20th	Night	16% 14% 35% 24% 9% 2	630
	21st to end	Night	22% 12% 27% 27% 8% 3	693
April	1st to 10th	Night	19% 12% 28% 32% 9%	630
	11th to 20th	Night	19% 11% 30% 29% 10% 1	623
	21st to end	Night	18% 10% 27% 33% 10% 2	630
May	1st to 10th	Night	20% 10% 30% 31% 7%	630
	11th to 20th	Night	24% 10% 30% 26% 9% 1	621
	21st to end	Night	22% 6% 29% 32% 9% 1	683
June	1st to 10th	Night	21% 6% 27% 31% 14% 1	630
	11th to 20th	Night	15% 10% 30% 33% 11%	630
	21st to end	Night	16% 7% 22% 37% 16% 1	630
July	1st to 10th	Night	10% 7% 29% 34% 19% 1	585
	11th to 20th	Night	13% 7% 28% 33% 16% 2	582
	21st to end	Night	13% 4 24% 35% 20% 3	657
August	1st to 10th	Night	14% 6% 26% 34% 18% 2	597
	11th to 20th	Night	16% 8% 19% 32% 21% 4	594
	21st to end	Night	19% 6% 29% 28% 17%	660
September	1st to 10th	Night	19% 8% 28% 30% 14% 2	600
	11th to 20th	Night	24% 9% 27% 28% 11% 1	600
	21st to end	Night	24% 10% 28% 27% 10% 1	734
October	1st to 10th	Night	26% 14% 30% 24% 6%	800
	11th to 20th	Night	31% 13% 27% 22% 7% 1	800
	21st to end	Night	30% 13% 31% 20% 5% 1	890
November	1st to 10th	Night	26% 16% 31% 20% 6% 2	1025
	11th to 20th	Night	27% 13% 32% 21% 5% 1	1050
	21st to end	Night	26% 18% 33% 20% 3 1	1050
December	1st to 10th	Night	14% 13% 41% 25% 6% 1	1050
	11th to 20th	Night	19% 13% 36% 24% 7% 1	1050
	21st to end	Night	21% 12% 31% 25% 9% 2	1155

Page generated at 2026-06-28 01:10:50. Version ac07

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