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 2024-02-05.

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	14% 11% 5% 9% 7% 4 5% 5% 5% 6% 29%	77824
	Night	13% 12% 5% 10% 8% 4 6% 5% 5% 6% 26%	81077
Transparency	Day	54% 7% 12% 19% 7% 1	77516
	Night	59% 6% 11% 17% 7% 1	80919
Seeing	Day	19% 13% 33% 23% 10% 2	15135
	Night	19% 11% 31% 27% 10% 1	25238

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% 13% 7% 16% 10% 11% 9% 4 4 4 14%	2218
	11th to 20th	Day	6% 10% 6% 13% 12% 7% 11% 8% 6% 5% 16%	2220
	21st to end	Day	10% 18% 9% 17% 9% 5% 7% 6% 5% 4 9%	2783
February	1st to 10th	Day	7% 12% 6% 10% 7% 6% 9% 10% 6% 6% 21%	1618
	11th to 20th	Day	8% 11% 4 11% 9% 5% 7% 9% 6% 5% 25%	1574
	21st to end	Day	5% 12% 5% 13% 9% 4 6% 6% 6% 7% 27%	1372
March	1st to 10th	Day	8% 13% 6% 9% 8% 5% 7% 4 4 5% 32%	1818
	11th to 20th	Day	11% 11% 6% 12% 6% 3 4 5% 4 5% 33%	1980
	21st to end	Day	14% 11% 4 8% 7% 4 6% 5% 5% 6% 30%	2272
April	1st to 10th	Day	14% 11% 4 8% 7% 4 4 4 5% 6% 33%	2160
	11th to 20th	Day	14% 11% 5% 8% 6% 3 4 4 5% 6% 35%	2190
	21st to end	Day	14% 10% 4 6% 5% 3 4 6% 5% 6% 37%	2452
May	1st to 10th	Day	15% 11% 4 7% 6% 4 6% 5% 5% 6% 31%	2520
	11th to 20th	Day	17% 8% 4 5% 6% 3 4 5% 6% 8% 32%	2479
	21st to end	Day	21% 6% 2 5% 4 4 5% 5% 4 7% 36%	2765
June	1st to 10th	Day	18% 6% 2 6% 5% 3 5% 6% 7% 8% 33%	2700
	11th to 20th	Day	17% 6% 3 6% 6% 3 5% 5% 6% 9% 33%	2700
	21st to end	Day	17% 6% 3 6% 5% 4 6% 7% 7% 8% 33%	2700
July	1st to 10th	Day	11% 6% 3 6% 5% 3 5% 5% 6% 8% 43%	2700
	11th to 20th	Day	16% 6% 3 5% 4 4 4 5% 5% 8% 40%	2700
	21st to end	Day	13% 5% 2 6% 5% 3 5% 5% 6% 8% 42%	2783
August	1st to 10th	Day	12% 5% 3 6% 4 4 5% 5% 7% 9% 40%	2507
	11th to 20th	Day	12% 5% 3 5% 4 4 6% 6% 7% 9% 40%	2365
	21st to end	Day	17% 7% 3 5% 5% 3 4 5% 6% 9% 37%	2495
September	1st to 10th	Day	17% 7% 2 6% 6% 4 5% 5% 4 6% 39%	2160
	11th to 20th	Day	20% 9% 3 6% 6% 4 5% 6% 5% 6% 29%	2160
	21st to end	Day	25% 10% 4 5% 5% 3 3 3 4 6% 32%	1894
October	1st to 10th	Day	21% 16% 4 8% 6% 3 5% 4 5% 5% 23%	1800
	11th to 20th	Day	19% 20% 5% 10% 7% 3 4 3 5% 5% 19%	1800
	21st to end	Day	22% 21% 8% 11% 5% 3 3 3 3 4 17%	1785
November	1st to 10th	Day	16% 20% 7% 11% 7% 4 4 3 5% 3 19%	1487
	11th to 20th	Day	17% 20% 9% 14% 9% 5% 4 3 3 4 12%	1520
	21st to end	Day	16% 18% 8% 18% 10% 4 4 4 3 3 11%	1520
December	1st to 10th	Day	9% 15% 8% 15% 11% 7% 8% 6% 5% 4 11%	1506
	11th to 20th	Day	11% 16% 7% 13% 8% 6% 5% 6% 4 4 19%	1679
	21st to end	Day	16% 16% 9% 11% 8% 5% 6% 4 4 5% 14%	2442
January	1st to 10th	Night	6% 16% 8% 15% 11% 8% 7% 6% 6% 4 14%	4737
	11th to 20th	Night	6% 11% 6% 14% 14% 9% 10% 8% 5% 4 13%	4749
	21st to end	Night	10% 19% 10% 14% 8% 4 6% 7% 5% 5% 13%	4884
February	1st to 10th	Night	7% 13% 5% 9% 8% 6% 11% 8% 7% 6% 20%	2436
	11th to 20th	Night	9% 13% 4 7% 7% 5% 8% 9% 5% 5% 28%	2273
	21st to end	Night	6% 13% 6% 11% 8% 5% 7% 6% 6% 6% 27%	1884
March	1st to 10th	Night	9% 11% 6% 9% 8% 4 6% 5% 5% 6% 31%	2145
	11th to 20th	Night	11% 13% 5% 9% 6% 2 3 3 4 5% 39%	1979
	21st to end	Night	14% 11% 5% 7% 5% 3 5% 4 5% 6% 35%	2084
April	1st to 10th	Night	15% 11% 4 8% 6% 2 4 4 5% 6% 36%	1800
	11th to 20th	Night	14% 11% 3 7% 4 3 4 5% 6% 5% 37%	1718
	21st to end	Night	13% 10% 4 6% 7% 4 4 6% 5% 5% 36%	1507
May	1st to 10th	Night	17% 10% 3 7% 5% 3 5% 5% 6% 7% 32%	1440
	11th to 20th	Night	20% 8% 3 4 5% 3 4 4 4 7% 39%	1416
	21st to end	Night	20% 8% 3 5% 5% 3 4 4 6% 8% 36%	1507
June	1st to 10th	Night	18% 8% 3 5% 4 3 5% 5% 6% 8% 35%	1260
	11th to 20th	Night	14% 6% 3 5% 6% 3 5% 5% 5% 8% 40%	1260
	21st to end	Night	14% 5% 2 5% 5% 3 5% 5% 6% 8% 41%	1260
July	1st to 10th	Night	10% 5% 3 4 5% 3 5% 4 6% 9% 47%	1260
	11th to 20th	Night	13% 5% 2 4 4 3 3 4 6% 10% 47%	1260
	21st to end	Night	11% 5% 3 4 4 3 4 4 6% 10% 46%	1534
August	1st to 10th	Night	11% 6% 3 5% 5% 3 4 5% 6% 8% 45%	1432
	11th to 20th	Night	13% 7% 2 5% 5% 2 4 4 6% 8% 44%	1534
	21st to end	Night	16% 6% 2 6% 5% 4 4 4 5% 8% 40%	1860
September	1st to 10th	Night	16% 5% 3 5% 5% 3 5% 4 5% 8% 41%	1800
	11th to 20th	Night	21% 8% 3 6% 5% 2 4 4 5% 5% 37%	1800
	21st to end	Night	21% 10% 4 5% 7% 3 4 4 4 5% 33%	2046
October	1st to 10th	Night	20% 13% 4 7% 5% 3 4 4 5% 6% 29%	2160
	11th to 20th	Night	22% 15% 4 8% 6% 3 4 4 4 6% 25%	2160
	21st to end	Night	22% 18% 5% 10% 7% 4 4 3 4 5% 19%	2569
November	1st to 10th	Night	18% 19% 7% 10% 6% 3 4 4 3 4 21%	2591
	11th to 20th	Night	17% 16% 7% 14% 10% 4 6% 4 3 4 14%	2660
	21st to end	Night	17% 19% 8% 13% 11% 5% 5% 4 3 4 12%	2660
December	1st to 10th	Night	8% 13% 7% 18% 14% 6% 7% 6% 3 4 13%	2669
	11th to 20th	Night	11% 13% 7% 14% 10% 5% 7% 6% 5% 5% 15%	3518
	21st to end	Night	13% 18% 8% 12% 12% 5% 6% 5% 4 3 13%	5225

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	73% 6% 6% 12% 4	2219
	11th to 20th	Day	67% 5% 9% 16% 3	2220
	21st to end	Day	75% 5% 7% 8% 4	2783
February	1st to 10th	Day	61% 6% 10% 14% 9%	1618
	11th to 20th	Day	56% 7% 10% 19% 8% 1	1583
	21st to end	Day	56% 5% 10% 19% 9% 1	1372
March	1st to 10th	Day	55% 6% 12% 17% 9% 1	1820
	11th to 20th	Day	54% 5% 10% 19% 10% 1	1980
	21st to end	Day	52% 7% 11% 19% 9% 2	2272
April	1st to 10th	Day	51% 5% 9% 19% 13% 3	2160
	11th to 20th	Day	50% 5% 10% 23% 12% 1	2190
	21st to end	Day	48% 6% 10% 23% 11% 2	2452
May	1st to 10th	Day	52% 8% 10% 20% 9% 1	2520
	11th to 20th	Day	48% 8% 12% 21% 10% 1	2483
	21st to end	Day	47% 8% 12% 19% 12% 2	2765
June	1st to 10th	Day	46% 10% 13% 20% 10% 1	2700
	11th to 20th	Day	47% 8% 13% 20% 12%	2700
	21st to end	Day	45% 10% 16% 22% 6% 1	2700
July	1st to 10th	Day	37% 9% 14% 30% 10% 1	2626
	11th to 20th	Day	40% 8% 15% 29% 8%	2619
	21st to end	Day	40% 9% 17% 27% 7% 1	2628
August	1st to 10th	Day	38% 9% 20% 26% 6%	2492
	11th to 20th	Day	38% 10% 19% 27% 6%	2365
	21st to end	Day	43% 8% 17% 24% 7%	2495
September	1st to 10th	Day	46% 7% 14% 27% 7%	2160
	11th to 20th	Day	53% 9% 16% 19% 3	2160
	21st to end	Day	55% 6% 15% 20% 4	1894
October	1st to 10th	Day	62% 6% 14% 15% 3	1800
	11th to 20th	Day	67% 6% 11% 14% 3	1800
	21st to end	Day	73% 5% 10% 10% 2	1785
November	1st to 10th	Day	70% 5% 12% 8% 4 1	1487
	11th to 20th	Day	79% 4 7% 7% 3	1520
	21st to end	Day	78% 5% 9% 6% 2	1520
December	1st to 10th	Day	75% 5% 8% 9% 3	1506
	11th to 20th	Day	67% 6% 8% 14% 5%	1680
	21st to end	Day	71% 5% 7% 12% 5%	2442
January	1st to 10th	Night	70% 6% 9% 12% 2	4737
	11th to 20th	Night	73% 6% 10% 9% 2	4749
	21st to end	Night	72% 6% 11% 8% 3	4884
February	1st to 10th	Night	62% 5% 10% 15% 7% 1	2436
	11th to 20th	Night	55% 7% 11% 19% 8%	2274
	21st to end	Night	55% 7% 11% 19% 7% 1	1884
March	1st to 10th	Night	53% 6% 12% 16% 12% 2	2156
	11th to 20th	Night	49% 4 13% 21% 11% 2	1980
	21st to end	Night	50% 5% 10% 20% 12% 3	2084
April	1st to 10th	Night	49% 5% 9% 20% 16% 2	1800
	11th to 20th	Night	46% 5% 10% 21% 15% 1	1718
	21st to end	Night	49% 5% 10% 21% 13% 2	1507
May	1st to 10th	Night	49% 7% 11% 19% 13%	1440
	11th to 20th	Night	45% 6% 11% 22% 14% 2	1417
	21st to end	Night	46% 8% 11% 18% 14% 2	1508
June	1st to 10th	Night	45% 8% 14% 20% 12% 1	1260
	11th to 20th	Night	41% 9% 9% 23% 18% 1	1260
	21st to end	Night	37% 10% 17% 27% 8% 1	1260
July	1st to 10th	Night	31% 9% 15% 32% 12% 1	1225
	11th to 20th	Night	32% 8% 17% 31% 11% 2	1218
	21st to end	Night	34% 10% 16% 30% 9% 1	1449
August	1st to 10th	Night	36% 8% 16% 30% 8% 1	1423
	11th to 20th	Night	38% 8% 16% 28% 10%	1534
	21st to end	Night	43% 6% 17% 26% 8% 1	1860
September	1st to 10th	Night	42% 7% 17% 24% 10%	1800
	11th to 20th	Night	48% 8% 16% 25% 4	1800
	21st to end	Night	52% 6% 16% 21% 4	2046
October	1st to 10th	Night	54% 7% 14% 19% 5%	2160
	11th to 20th	Night	61% 6% 12% 18% 3	2160
	21st to end	Night	67% 7% 12% 11% 2	2569
November	1st to 10th	Night	68% 6% 11% 12% 3	2591
	11th to 20th	Night	76% 5% 9% 8% 2	2660
	21st to end	Night	78% 5% 8% 7% 2	2660
December	1st to 10th	Night	75% 6% 9% 8% 3	2669
	11th to 20th	Night	66% 8% 10% 11% 3	3516
	21st to end	Night	74% 6% 6% 12% 2	5225

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% 13% 39% 24% 8% 1	270
	11th to 20th	Day	13% 10% 37% 29% 10% 1	270
	21st to end	Day	16% 10% 38% 26% 9% 1	297
February	1st to 10th	Day	14% 13% 45% 21% 6%	252
	11th to 20th	Day	16% 19% 37% 18% 10% 2	240
	21st to end	Day	13% 19% 43% 16% 6% 3	198
March	1st to 10th	Day	10% 13% 43% 26% 7% 2	240
	11th to 20th	Day	11% 21% 40% 21% 5% 3	240
	21st to end	Day	18% 13% 36% 20% 10% 3	358
April	1st to 10th	Day	21% 15% 32% 22% 10% 1	420
	11th to 20th	Day	23% 15% 28% 23% 11%	468
	21st to end	Day	20% 12% 34% 24% 10% 2	600
May	1st to 10th	Day	20% 16% 32% 22% 7% 2	603
	11th to 20th	Day	22% 14% 29% 23% 10% 2	625
	21st to end	Day	24% 11% 30% 23% 10% 1	679
June	1st to 10th	Day	20% 12% 31% 24% 10% 3	630
	11th to 20th	Day	18% 14% 37% 20% 8% 2	630
	21st to end	Day	16% 10% 32% 25% 12% 4	630
July	1st to 10th	Day	12% 14% 33% 24% 13% 4	621
	11th to 20th	Day	16% 14% 28% 22% 16% 4	618
	21st to end	Day	12% 9% 30% 30% 12% 7%	684
August	1st to 10th	Day	13% 9% 31% 29% 14% 3	626
	11th to 20th	Day	15% 8% 27% 28% 17% 4	615
	21st to end	Day	20% 11% 30% 24% 14% 1	614
September	1st to 10th	Day	20% 14% 32% 21% 10% 2	450
	11th to 20th	Day	24% 12% 29% 26% 8% 1	450
	21st to end	Day	30% 12% 32% 18% 7% 1	323
October	1st to 10th	Day	28% 17% 24% 24% 5% 2	270
	11th to 20th	Day	25% 17% 36% 19% 3 1	270
	21st to end	Day	37% 15% 34% 11% 3	297
November	1st to 10th	Day	26% 17% 33% 19% 6%	270
	11th to 20th	Day	28% 19% 33% 15% 4	270
	21st to end	Day	25% 23% 36% 13% 3	270
December	1st to 10th	Day	16% 17% 39% 23% 4 2	270
	11th to 20th	Day	20% 18% 37% 23% 3	270
	21st to end	Day	17% 15% 34% 24% 6% 4	297
January	1st to 10th	Night	14% 13% 37% 27% 8% 1	950
	11th to 20th	Night	16% 10% 37% 28% 7% 1	950
	21st to end	Night	17% 11% 35% 29% 8% 1	1045
February	1st to 10th	Night	13% 12% 37% 29% 8% 1	923
	11th to 20th	Night	14% 13% 32% 26% 12% 3	879
	21st to end	Night	10% 13% 33% 29% 12% 3	700
March	1st to 10th	Night	14% 13% 34% 27% 11% 1	716
	11th to 20th	Night	17% 14% 34% 24% 9% 2	540
	21st to end	Night	20% 12% 27% 28% 9% 4	594
April	1st to 10th	Night	20% 12% 27% 32% 9%	540
	11th to 20th	Night	19% 11% 30% 28% 11% 1	533
	21st to end	Night	16% 10% 28% 33% 10% 2	540
May	1st to 10th	Night	21% 11% 31% 29% 7% 1	540
	11th to 20th	Night	24% 11% 29% 25% 10% 1	531
	21st to end	Night	23% 6% 30% 31% 9%	584
June	1st to 10th	Night	22% 6% 26% 30% 14% 1	540
	11th to 20th	Night	14% 10% 30% 32% 13% 1	540
	21st to end	Night	16% 8% 21% 37% 18% 1	540
July	1st to 10th	Night	10% 7% 29% 35% 17% 2	525
	11th to 20th	Night	13% 7% 29% 33% 16% 3	522
	21st to end	Night	14% 3 25% 34% 21% 4	591
August	1st to 10th	Night	13% 6% 27% 34% 19% 1	537
	11th to 20th	Night	16% 8% 19% 33% 20% 4	534
	21st to end	Night	19% 6% 30% 27% 17%	594
September	1st to 10th	Night	19% 9% 28% 31% 13% 1	540
	11th to 20th	Night	25% 10% 27% 26% 11% 1	540
	21st to end	Night	26% 10% 28% 26% 8% 1	660
October	1st to 10th	Night	27% 13% 29% 24% 7%	720
	11th to 20th	Night	31% 12% 27% 22% 7% 1	720
	21st to end	Night	31% 13% 30% 20% 5% 1	800
November	1st to 10th	Night	26% 16% 31% 20% 6% 1	925
	11th to 20th	Night	26% 13% 33% 22% 5% 1	950
	21st to end	Night	27% 18% 33% 19% 3 1	950
December	1st to 10th	Night	14% 13% 41% 25% 6% 2	950
	11th to 20th	Night	18% 14% 35% 24% 7% 1	950
	21st to end	Night	21% 12% 31% 26% 9% 2	1045

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