Atikokan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Atikokan 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 6% 7% 32%	138346
	Night	13% 12% 5% 11% 6% 5% 5% 4 5% 6% 29%	134328
Transparency	Day	51% 5% 12% 22% 9% 1	141788
	Night	56% 5% 11% 19% 9% 1	138972
Seeing	Day	20% 14% 33% 21% 9% 2	18497
	Night	20% 11% 32% 26% 10% 1	28420

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% 7% 19% 9% 7% 6% 4 5% 5% 19%	4124
	11th to 20th	Day	6% 15% 6% 20% 7% 5% 8% 9% 8% 4 12%	4562
	21st to end	Day	5% 13% 10% 19% 7% 6% 6% 5% 7% 6% 15%	5156
February	1st to 10th	Day	7% 13% 5% 13% 7% 7% 8% 7% 7% 5% 20%	1883
	11th to 20th	Day	8% 11% 4 13% 8% 6% 5% 4 6% 6% 29%	1844
	21st to end	Day	7% 13% 6% 13% 8% 5% 4 4 6% 6% 28%	1638
March	1st to 10th	Day	10% 12% 4 10% 5% 4 4 3 4 6% 38%	4623
	11th to 20th	Day	8% 12% 7% 12% 6% 6% 4 3 5% 6% 31%	5090
	21st to end	Day	16% 15% 4 11% 5% 4 3 3 4 5% 29%	5855
April	1st to 10th	Day	15% 14% 4 8% 6% 5% 5% 4 5% 6% 29%	2520
	11th to 20th	Day	18% 13% 4 8% 5% 4 3 4 5% 6% 32%	2509
	21st to end	Day	17% 13% 4 8% 5% 5% 4 3 4 5% 32%	2840
May	1st to 10th	Day	13% 11% 3 7% 5% 4 4 3 5% 7% 38%	8241
	11th to 20th	Day	16% 10% 3 7% 4 4 4 4 5% 8% 37%	8222
	21st to end	Day	13% 5% 2 5% 3 4 5% 4 7% 8% 45%	9061
June	1st to 10th	Day	15% 8% 2 6% 4 4 5% 5% 6% 8% 37%	3045
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	3150
	21st to end	Day	18% 6% 2 6% 5% 5% 5% 4 7% 9% 33%	3150
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 5% 7% 10% 39%	6800
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 6% 9% 41%	6609
	21st to end	Day	12% 7% 2 7% 5% 5% 4 4 6% 8% 39%	6926
August	1st to 10th	Day	14% 6% 2 8% 6% 5% 6% 4 7% 8% 34%	4563
	11th to 20th	Day	14% 5% 1 4 3 4 4 4 7% 10% 44%	4233
	21st to end	Day	15% 7% 3 6% 4 4 5% 4 6% 9% 39%	4459
September	1st to 10th	Day	14% 7% 3 8% 4 4 4 3 5% 8% 38%	2400
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 4 6% 8% 35%	2400
	21st to end	Day	20% 9% 2 8% 4 4 4 3 5% 7% 33%	2110
October	1st to 10th	Day	17% 13% 3 8% 5% 4 5% 3 5% 7% 30%	2000
	11th to 20th	Day	19% 17% 5% 10% 5% 4 5% 3 4 6% 23%	2000
	21st to end	Day	20% 21% 4 10% 4 4 3 2 4 4 25%	2005
November	1st to 10th	Day	15% 20% 6% 10% 5% 5% 5% 3 5% 6% 20%	1692
	11th to 20th	Day	15% 19% 7% 15% 7% 5% 4 2 3 4 19%	1680
	21st to end	Day	15% 18% 6% 19% 8% 5% 3 3 3 5% 15%	1680
December	1st to 10th	Day	12% 18% 5% 22% 13% 6% 4 3 4 3 10%	2690
	11th to 20th	Day	8% 17% 8% 14% 6% 8% 5% 4 5% 5% 20%	3011
	21st to end	Day	17% 22% 7% 15% 7% 5% 4 3 4 4 14%	3575
January	1st to 10th	Night	6% 14% 7% 19% 8% 7% 6% 4 5% 5% 20%	8800
	11th to 20th	Night	7% 13% 7% 17% 11% 9% 8% 7% 6% 2 12%	8337
	21st to end	Night	6% 13% 9% 15% 8% 7% 8% 4 7% 7% 17%	9058
February	1st to 10th	Night	9% 12% 5% 11% 7% 8% 9% 4 7% 7% 22%	2735
	11th to 20th	Night	8% 11% 4 11% 7% 6% 8% 5% 6% 6% 29%	2663
	21st to end	Night	6% 15% 6% 12% 9% 7% 7% 4 5% 5% 24%	2167
March	1st to 10th	Night	10% 11% 3 9% 6% 5% 6% 4 5% 6% 35%	5482
	11th to 20th	Night	8% 14% 5% 14% 9% 7% 5% 4 4 6% 25%	5089
	21st to end	Night	19% 15% 4 9% 5% 4 3 3 4 6% 27%	5318
April	1st to 10th	Night	16% 13% 4 8% 4 4 4 4 4 6% 33%	2100
	11th to 20th	Night	16% 14% 5% 8% 5% 3 4 3 4 6% 32%	2057
	21st to end	Night	19% 11% 4 7% 4 4 5% 4 5% 5% 31%	1779
May	1st to 10th	Night	14% 8% 3 6% 3 4 4 3 5% 6% 45%	4688
	11th to 20th	Night	17% 8% 3 5% 4 4 3 3 4 6% 41%	4670
	21st to end	Night	15% 6% 2 4 3 3 4 4 5% 7% 47%	5148
June	1st to 10th	Night	18% 7% 2 6% 5% 4 4 4 5% 7% 40%	1571
	11th to 20th	Night	13% 5% 2 6% 5% 4 4 5% 7% 8% 42%	1470
	21st to end	Night	14% 5% 2 6% 5% 5% 5% 4 6% 7% 41%	1470
July	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 7% 9% 47%	3180
	11th to 20th	Night	13% 6% 2 5% 4 4 4 4 6% 9% 44%	3356
	21st to end	Night	13% 7% 2 6% 3 4 4 4 6% 7% 44%	3948
August	1st to 10th	Night	15% 6% 2 5% 3 4 4 4 6% 9% 43%	2597
	11th to 20th	Night	12% 4 2 5% 4 3 5% 4 5% 8% 47%	2822
	21st to end	Night	16% 5% 2 5% 4 4 4 3 5% 7% 44%	3443
September	1st to 10th	Night	12% 7% 2 6% 5% 4 5% 3 5% 7% 44%	2000
	11th to 20th	Night	16% 7% 3 6% 3 4 3 4 5% 5% 44%	2000
	21st to end	Night	21% 10% 2 5% 3 3 4 2 5% 7% 37%	2266
October	1st to 10th	Night	19% 11% 3 6% 4 4 4 3 5% 7% 34%	2400
	11th to 20th	Night	19% 15% 4 7% 5% 3 4 3 4 6% 30%	2400
	21st to end	Night	20% 14% 4 11% 5% 4 3 3 6% 6% 24%	2834
November	1st to 10th	Night	15% 17% 5% 12% 6% 4 4 3 5% 5% 24%	2824
	11th to 20th	Night	17% 17% 6% 15% 6% 5% 4 3 4 4 18%	2940
	21st to end	Night	13% 18% 8% 16% 9% 5% 4 3 4 4 16%	2940
December	1st to 10th	Night	11% 20% 9% 21% 10% 7% 4 3 3 3 9%	4720
	11th to 20th	Night	10% 15% 6% 16% 8% 6% 6% 5% 5% 5% 17%	5411
	21st to end	Night	19% 20% 7% 16% 6% 4 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	67% 3 5% 15% 7% 3	4125
	11th to 20th	Day	70% 3 5% 17% 5%	4593
	21st to end	Day	67% 3 8% 13% 9%	5156
February	1st to 10th	Day	61% 5% 10% 15% 9% 1	1883
	11th to 20th	Day	54% 4 10% 21% 9% 1	1853
	21st to end	Day	56% 4 12% 16% 11% 1	1638
March	1st to 10th	Day	48% 4 12% 18% 13% 5%	4625
	11th to 20th	Day	54% 5% 11% 20% 11%	5090
	21st to end	Day	57% 4 8% 16% 14% 1	5855
April	1st to 10th	Day	55% 5% 8% 18% 13% 1	2520
	11th to 20th	Day	53% 5% 11% 19% 11% 1	2509
	21st to end	Day	55% 4 7% 19% 12% 1	2840
May	1st to 10th	Day	44% 5% 11% 27% 13% 1	8250
	11th to 20th	Day	45% 5% 9% 23% 16% 2	8226
	21st to end	Day	35% 6% 10% 30% 18% 1	9061
June	1st to 10th	Day	43% 7% 15% 23% 11% 1	3045
	11th to 20th	Day	46% 6% 12% 23% 12%	3150
	21st to end	Day	45% 8% 16% 24% 7% 1	3150
July	1st to 10th	Day	39% 6% 18% 28% 8%	6727
	11th to 20th	Day	39% 5% 21% 31% 4	6528
	21st to end	Day	42% 5% 17% 28% 7%	6728
August	1st to 10th	Day	46% 6% 15% 25% 8% 1	4548
	11th to 20th	Day	34% 6% 23% 32% 4	4274
	21st to end	Day	42% 5% 20% 27% 6%	4458
September	1st to 10th	Day	43% 7% 16% 26% 8%	2400
	11th to 20th	Day	46% 7% 22% 21% 5%	2400
	21st to end	Day	50% 6% 15% 23% 6%	2110
October	1st to 10th	Day	45% 5% 16% 22% 11%	3260
	11th to 20th	Day	55% 4 14% 18% 8%	3240
	21st to end	Day	60% 3 16% 19% 2	3217
November	1st to 10th	Day	65% 6% 12% 11% 5% 1	1692
	11th to 20th	Day	70% 4 8% 13% 4	1680
	21st to end	Day	73% 5% 9% 8% 4	1680
December	1st to 10th	Day	80% 4 7% 7% 2	2690
	11th to 20th	Day	66% 5% 8% 10% 11%	3012
	21st to end	Day	76% 2 4 13% 5%	3575
January	1st to 10th	Night	66% 4 8% 12% 10% 1	8800
	11th to 20th	Night	74% 3 6% 10% 6%	8381
	21st to end	Night	66% 3 8% 16% 7%	9058
February	1st to 10th	Night	61% 5% 11% 15% 9%	2735
	11th to 20th	Night	53% 5% 13% 18% 10% 1	2664
	21st to end	Night	60% 5% 10% 16% 8% 1	2167
March	1st to 10th	Night	50% 4 11% 13% 17% 4	5493
	11th to 20th	Night	61% 5% 12% 14% 8% 1	5090
	21st to end	Night	58% 4 8% 18% 12% 1	5318
April	1st to 10th	Night	52% 5% 9% 19% 14% 1	2100
	11th to 20th	Night	53% 4 11% 19% 11% 2	2057
	21st to end	Night	53% 5% 9% 19% 13% 1	1779
May	1st to 10th	Night	40% 5% 10% 30% 16% 1	4695
	11th to 20th	Night	43% 5% 11% 24% 15% 2	4671
	21st to end	Night	36% 5% 10% 30% 16% 2	5149
June	1st to 10th	Night	43% 6% 14% 23% 13%	1571
	11th to 20th	Night	38% 8% 11% 25% 18%	1470
	21st to end	Night	40% 9% 15% 26% 9% 1	1470
July	1st to 10th	Night	33% 5% 21% 31% 10%	3145
	11th to 20th	Night	36% 6% 22% 28% 8%	3314
	21st to end	Night	40% 5% 15% 32% 8%	3832
August	1st to 10th	Night	37% 5% 18% 29% 10% 1	2588
	11th to 20th	Night	35% 6% 19% 34% 5%	2847
	21st to end	Night	40% 5% 21% 28% 7%	3443
September	1st to 10th	Night	38% 7% 16% 30% 8%	2000
	11th to 20th	Night	40% 8% 20% 26% 5%	2000
	21st to end	Night	47% 6% 12% 28% 6%	2266
October	1st to 10th	Night	41% 5% 11% 33% 11%	3920
	11th to 20th	Night	53% 4 12% 24% 7%	3899
	21st to end	Night	59% 6% 16% 17% 4	4572
November	1st to 10th	Night	62% 5% 12% 16% 5%	2824
	11th to 20th	Night	70% 5% 9% 11% 4	2940
	21st to end	Night	73% 6% 9% 9% 3	2940
December	1st to 10th	Night	82% 4 6% 6% 2	4720
	11th to 20th	Night	68% 5% 9% 12% 6%	5409
	21st to end	Night	76% 3 5% 12% 4	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	13% 15% 41% 21% 8%	330
	11th to 20th	Day	18% 12% 39% 25% 7% 1	330
	21st to end	Day	15% 12% 44% 23% 6%	363
February	1st to 10th	Day	16% 20% 43% 15% 6% 1	330
	11th to 20th	Day	17% 16% 42% 18% 5% 2	330
	21st to end	Day	17% 24% 42% 13% 3	273
March	1st to 10th	Day	18% 15% 39% 22% 5%	330
	11th to 20th	Day	13% 23% 43% 16% 4 2	330
	21st to end	Day	20% 18% 34% 17% 8% 2	478
April	1st to 10th	Day	23% 17% 34% 17% 9% 1	540
	11th to 20th	Day	27% 15% 28% 22% 8% 1	547
	21st to end	Day	27% 15% 30% 20% 7% 1	750
May	1st to 10th	Day	23% 18% 31% 19% 7% 2	753
	11th to 20th	Day	21% 15% 34% 19% 8% 3	775
	21st to end	Day	21% 12% 30% 25% 9% 2	844
June	1st to 10th	Day	20% 13% 32% 24% 9% 2	780
	11th to 20th	Day	19% 17% 33% 21% 8% 2	780
	21st to end	Day	22% 10% 29% 24% 11% 4	780
July	1st to 10th	Day	11% 10% 34% 26% 14% 5%	722
	11th to 20th	Day	17% 11% 30% 24% 14% 4	718
	21st to end	Day	12% 9% 33% 25% 16% 5%	794
August	1st to 10th	Day	14% 9% 31% 27% 15% 3	726
	11th to 20th	Day	17% 8% 25% 27% 16% 5%	715
	21st to end	Day	19% 10% 30% 24% 15% 1	678
September	1st to 10th	Day	16% 14% 29% 25% 13% 2	530
	11th to 20th	Day	22% 12% 30% 23% 10% 2	530
	21st to end	Day	27% 15% 27% 18% 11% 2	405
October	1st to 10th	Day	24% 20% 30% 17% 7% 2	330
	11th to 20th	Day	24% 20% 34% 18% 4	330
	21st to end	Day	35% 18% 33% 10% 3 1	363
November	1st to 10th	Day	26% 18% 35% 16% 5% 1	330
	11th to 20th	Day	26% 20% 35% 14% 3 1	330
	21st to end	Day	26% 20% 37% 14% 3 1	330
December	1st to 10th	Day	16% 17% 46% 16% 4	330
	11th to 20th	Day	19% 17% 43% 16% 5%	330
	21st to end	Day	23% 14% 37% 21% 3 2	363
January	1st to 10th	Night	15% 14% 37% 26% 7% 1	1050
	11th to 20th	Night	18% 12% 39% 23% 7% 1	1050
	21st to end	Night	17% 11% 39% 25% 7%	1155
February	1st to 10th	Night	16% 14% 36% 25% 9% 1	1050
	11th to 20th	Night	14% 14% 33% 28% 8% 2	1029
	21st to end	Night	14% 15% 35% 26% 9% 1	783
March	1st to 10th	Night	17% 13% 36% 25% 8%	840
	11th to 20th	Night	18% 16% 35% 23% 8% 1	630
	21st to end	Night	23% 12% 28% 25% 9% 2	693
April	1st to 10th	Night	21% 13% 33% 26% 7%	630
	11th to 20th	Night	21% 12% 32% 25% 9%	623
	21st to end	Night	24% 8% 28% 30% 9% 1	630
May	1st to 10th	Night	22% 10% 32% 29% 7% 1	630
	11th to 20th	Night	20% 12% 30% 24% 11% 1	621
	21st to end	Night	20% 8% 27% 34% 11%	683
June	1st to 10th	Night	21% 7% 29% 29% 14%	630
	11th to 20th	Night	17% 6% 33% 35% 10%	630
	21st to end	Night	16% 6% 25% 36% 15% 1	630
July	1st to 10th	Night	10% 5% 28% 37% 18% 1	585
	11th to 20th	Night	12% 6% 32% 30% 19% 2	582
	21st to end	Night	10% 6% 26% 36% 20% 2	657
August	1st to 10th	Night	11% 4 29% 37% 17% 1	597
	11th to 20th	Night	15% 7% 22% 31% 22% 3	594
	21st to end	Night	18% 7% 25% 33% 16% 1	660
September	1st to 10th	Night	15% 7% 27% 32% 18% 1	600
	11th to 20th	Night	20% 7% 28% 28% 16% 1	600
	21st to end	Night	27% 10% 27% 25% 10% 2	745
October	1st to 10th	Night	26% 12% 31% 23% 8% 1	800
	11th to 20th	Night	28% 13% 30% 22% 6% 1	800
	21st to end	Night	28% 13% 31% 23% 6%	880
November	1st to 10th	Night	26% 13% 31% 24% 5% 1	978
	11th to 20th	Night	27% 14% 32% 20% 7% 1	1050
	21st to end	Night	23% 17% 36% 19% 4	1050
December	1st to 10th	Night	18% 14% 38% 24% 6% 1	1050
	11th to 20th	Night	21% 14% 36% 22% 6% 1	1050
	21st to end	Night	25% 12% 32% 23% 7% 1	1155

Page generated at 2026-06-28 02:10:43. Version ac07

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