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 2025-02-25.

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% 4 10% 5% 5% 5% 4 6% 7% 31%	108727
	Night	13% 12% 5% 12% 6% 5% 5% 4 5% 6% 28%	110127
Transparency	Day	52% 6% 13% 21% 8% 1	112217
	Night	56% 5% 11% 19% 8% 1	114799
Seeing	Day	20% 14% 33% 21% 9% 2	16544
	Night	19% 11% 32% 27% 10% 1	26654

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% 17% 9% 7% 7% 4 5% 6% 19%	3178
	11th to 20th	Day	5% 12% 5% 19% 7% 5% 9% 8% 10% 4 14%	3498
	21st to end	Day	7% 16% 13% 22% 7% 6% 4 3 4 4 12%	3982
February	1st to 10th	Day	8% 12% 5% 13% 7% 7% 9% 7% 7% 5% 21%	1793
	11th to 20th	Day	8% 11% 4 13% 8% 6% 5% 4 6% 6% 29%	1754
	21st to end	Day	7% 13% 6% 12% 8% 5% 4 4 6% 6% 29%	1522
March	1st to 10th	Day	10% 12% 3 8% 5% 4 4 3 5% 6% 41%	3148
	11th to 20th	Day	7% 13% 8% 13% 6% 5% 4 3 4 6% 31%	3480
	21st to end	Day	15% 16% 5% 11% 5% 4 3 3 4 4 30%	3995
April	1st to 10th	Day	14% 13% 3 9% 7% 4 5% 4 5% 7% 30%	2280
	11th to 20th	Day	18% 12% 3 7% 4 4 3 4 5% 6% 33%	2267
	21st to end	Day	17% 13% 4 8% 5% 5% 4 3 4 5% 33%	2570
May	1st to 10th	Day	18% 11% 3 7% 5% 4 4 3 5% 7% 33%	4428
	11th to 20th	Day	16% 9% 3 7% 5% 5% 4 4 5% 8% 34%	4399
	21st to end	Day	21% 7% 3 6% 4 4 4 3 5% 6% 37%	4837
June	1st to 10th	Day	17% 7% 2 6% 4 4 4 5% 6% 8% 36%	2755
	11th to 20th	Day	17% 7% 3 7% 5% 4 5% 4 5% 7% 36%	2850
	21st to end	Day	18% 6% 2 6% 5% 5% 5% 4 7% 9% 33%	2850
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 5% 8% 9% 39%	4750
	11th to 20th	Day	11% 4 2 5% 4 4 4 4 6% 10% 46%	4611
	21st to end	Day	12% 7% 2 7% 5% 5% 4 4 6% 8% 39%	4814
August	1st to 10th	Day	14% 6% 2 8% 6% 5% 6% 4 7% 8% 33%	4423
	11th to 20th	Day	14% 5% 1 4 3 4 4 4 7% 10% 44%	4101
	21st to end	Day	15% 7% 3 6% 4 4 5% 4 6% 9% 38%	4322
September	1st to 10th	Day	15% 7% 3 7% 4 4 4 3 5% 8% 40%	2280
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 4 6% 8% 34%	2280
	21st to end	Day	21% 9% 2 8% 4 4 4 3 5% 7% 32%	2004
October	1st to 10th	Day	18% 13% 3 8% 5% 4 4 3 5% 7% 29%	1900
	11th to 20th	Day	18% 17% 5% 10% 5% 4 5% 3 4 6% 23%	1900
	21st to end	Day	20% 21% 4 9% 4 4 3 2 4 4 25%	1905
November	1st to 10th	Day	16% 21% 6% 9% 5% 5% 5% 3 5% 6% 20%	1610
	11th to 20th	Day	15% 19% 7% 15% 7% 5% 4 2 3 4 18%	1600
	21st to end	Day	15% 19% 7% 19% 7% 5% 3 3 3 5% 15%	1600
December	1st to 10th	Day	12% 19% 5% 22% 13% 6% 4 3 4 3 9%	2610
	11th to 20th	Day	8% 17% 8% 14% 6% 8% 5% 4 5% 5% 21%	2933
	21st to end	Day	17% 22% 7% 15% 7% 5% 4 3 4 4 14%	3498
January	1st to 10th	Night	6% 14% 6% 18% 9% 6% 6% 4 5% 5% 21%	6787
	11th to 20th	Night	7% 11% 6% 18% 11% 9% 8% 6% 7% 3 13%	6391
	21st to end	Night	8% 17% 11% 18% 7% 5% 5% 3 6% 5% 14%	6996
February	1st to 10th	Night	8% 12% 5% 11% 7% 8% 9% 4 7% 7% 22%	2605
	11th to 20th	Night	8% 10% 3 11% 7% 6% 8% 5% 6% 6% 29%	2533
	21st to end	Night	6% 15% 6% 12% 8% 7% 6% 4 5% 5% 25%	2026
March	1st to 10th	Night	11% 12% 3 9% 6% 5% 5% 3 4 6% 35%	3722
	11th to 20th	Night	9% 13% 5% 12% 8% 6% 5% 4 4 6% 28%	3479
	21st to end	Night	19% 14% 4 10% 5% 4 3 3 5% 6% 26%	3636
April	1st to 10th	Night	16% 13% 3 8% 4 4 4 4 4 6% 33%	1900
	11th to 20th	Night	16% 14% 4 8% 5% 4 4 3 5% 7% 31%	1859
	21st to end	Night	19% 12% 3 7% 5% 4 5% 4 5% 5% 32%	1610
May	1st to 10th	Night	18% 9% 3 6% 3 4 4 3 5% 6% 38%	2523
	11th to 20th	Night	13% 8% 3 7% 5% 5% 4 4 5% 7% 38%	2506
	21st to end	Night	23% 7% 2 5% 4 3 4 4 4 5% 40%	2750
June	1st to 10th	Night	18% 6% 2 6% 5% 4 4 4 5% 7% 39%	1421
	11th to 20th	Night	13% 4 2 6% 5% 4 4 5% 7% 8% 42%	1330
	21st to end	Night	14% 5% 2 6% 5% 5% 5% 5% 6% 7% 41%	1330
July	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 7% 9% 44%	2220
	11th to 20th	Night	8% 4 1 5% 4 4 4 5% 7% 10% 48%	2344
	21st to end	Night	11% 6% 2 6% 3 4 3 4 5% 7% 49%	2750
August	1st to 10th	Night	15% 6% 2 5% 3 4 4 4 6% 10% 43%	2517
	11th to 20th	Night	11% 4 2 5% 4 3 5% 4 5% 9% 47%	2734
	21st to end	Night	17% 5% 2 5% 4 4 4 3 5% 7% 44%	3338
September	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	16% 7% 3 6% 3 4 3 4 5% 5% 44%	1900
	21st to end	Night	22% 10% 3 5% 4 3 4 2 5% 7% 36%	2153
October	1st to 10th	Night	19% 11% 3 6% 4 5% 4 3 5% 7% 33%	2280
	11th to 20th	Night	19% 15% 4 7% 5% 3 5% 3 4 6% 29%	2280
	21st to end	Night	20% 14% 4 11% 5% 4 3 3 6% 6% 23%	2692
November	1st to 10th	Night	15% 18% 5% 12% 6% 4 4 3 5% 5% 24%	2686
	11th to 20th	Night	17% 17% 6% 15% 7% 5% 4 3 4 4 18%	2800
	21st to end	Night	13% 18% 8% 16% 9% 5% 4 3 4 4 16%	2800
December	1st to 10th	Night	11% 20% 9% 21% 10% 7% 4 2 3 3 9%	4580
	11th to 20th	Night	10% 15% 6% 16% 8% 6% 6% 5% 5% 6% 17%	5269
	21st to end	Night	19% 20% 7% 16% 6% 4 4 3 4 4 13%	7480

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% 4 5% 13% 9% 3	3179
	11th to 20th	Day	67% 4 6% 20% 3	3529
	21st to end	Day	75% 3 4 11% 6%	3982
February	1st to 10th	Day	60% 5% 10% 15% 9% 1	1793
	11th to 20th	Day	54% 4 10% 21% 9% 1	1763
	21st to end	Day	55% 4 12% 16% 12% 1	1522
March	1st to 10th	Day	43% 5% 11% 23% 16% 1	3150
	11th to 20th	Day	53% 6% 12% 21% 8%	3480
	21st to end	Day	57% 5% 8% 15% 13% 1	3995
April	1st to 10th	Day	54% 5% 8% 18% 14% 2	2280
	11th to 20th	Day	51% 5% 11% 20% 12% 1	2267
	21st to end	Day	54% 5% 8% 19% 13% 1	2570
May	1st to 10th	Day	47% 7% 13% 22% 11% 1	4440
	11th to 20th	Day	46% 8% 13% 22% 11% 1	4403
	21st to end	Day	45% 8% 11% 21% 14% 1	4837
June	1st to 10th	Day	43% 7% 15% 24% 10% 1	2755
	11th to 20th	Day	46% 6% 12% 23% 13% 1	2850
	21st to end	Day	45% 8% 16% 24% 7%	2850
July	1st to 10th	Day	38% 7% 18% 28% 8%	4676
	11th to 20th	Day	32% 6% 22% 34% 6%	4530
	21st to end	Day	42% 6% 15% 30% 6%	4662
August	1st to 10th	Day	46% 6% 15% 24% 8% 1	4408
	11th to 20th	Day	34% 6% 23% 33% 4	4142
	21st to end	Day	42% 5% 20% 27% 6%	4321
September	1st to 10th	Day	42% 7% 16% 27% 8%	2280
	11th to 20th	Day	46% 8% 21% 21% 4	2280
	21st to end	Day	51% 7% 14% 22% 5%	2004
October	1st to 10th	Day	45% 5% 16% 22% 11%	3160
	11th to 20th	Day	55% 4 14% 19% 8%	3140
	21st to end	Day	60% 3 16% 19% 2	3117
November	1st to 10th	Day	65% 6% 12% 12% 4 1	1610
	11th to 20th	Day	71% 4 8% 12% 4	1600
	21st to end	Day	74% 5% 10% 7% 4	1600
December	1st to 10th	Day	80% 4 7% 6% 2	2610
	11th to 20th	Day	66% 5% 8% 10% 11% 1	2934
	21st to end	Day	76% 2 4 13% 5%	3498
January	1st to 10th	Night	65% 4 8% 13% 9% 1	6787
	11th to 20th	Night	71% 4 7% 12% 5%	6435
	21st to end	Night	71% 4 7% 13% 6%	6996
February	1st to 10th	Night	60% 5% 11% 14% 9%	2605
	11th to 20th	Night	53% 5% 14% 18% 10% 1	2534
	21st to end	Night	60% 5% 10% 16% 8% 1	2026
March	1st to 10th	Night	50% 5% 12% 17% 15% 1	3733
	11th to 20th	Night	56% 5% 13% 16% 7% 1	3480
	21st to end	Night	56% 6% 10% 17% 10% 2	3636
April	1st to 10th	Night	50% 6% 10% 18% 15% 1	1900
	11th to 20th	Night	53% 5% 10% 18% 12% 2	1859
	21st to end	Night	51% 5% 10% 20% 13% 1	1610
May	1st to 10th	Night	44% 7% 11% 25% 13%	2530
	11th to 20th	Night	42% 8% 14% 24% 10% 2	2507
	21st to end	Night	46% 7% 11% 22% 12% 2	2751
June	1st to 10th	Night	44% 7% 14% 24% 11%	1421
	11th to 20th	Night	37% 8% 11% 24% 19% 1	1330
	21st to end	Night	40% 10% 15% 25% 9% 1	1330
July	1st to 10th	Night	34% 7% 22% 27% 9%	2185
	11th to 20th	Night	29% 8% 20% 33% 10%	2302
	21st to end	Night	34% 6% 15% 36% 8% 1	2662
August	1st to 10th	Night	37% 6% 18% 29% 10% 1	2508
	11th to 20th	Night	34% 6% 19% 34% 6%	2759
	21st to end	Night	39% 5% 21% 28% 7%	3338
September	1st to 10th	Night	37% 7% 15% 31% 9%	1900
	11th to 20th	Night	41% 8% 20% 27% 5%	1900
	21st to end	Night	48% 6% 12% 27% 6%	2153
October	1st to 10th	Night	41% 5% 10% 33% 10%	3800
	11th to 20th	Night	53% 4 13% 24% 6%	3779
	21st to end	Night	59% 6% 16% 16% 3	4430
November	1st to 10th	Night	62% 6% 12% 15% 5%	2686
	11th to 20th	Night	71% 5% 10% 11% 4	2800
	21st to end	Night	73% 6% 9% 9% 3	2800
December	1st to 10th	Night	82% 4 6% 6% 2	4580
	11th to 20th	Night	68% 5% 9% 12% 6%	5267
	21st to end	Night	76% 3 5% 12% 4	7480

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	14% 14% 41% 22% 9%	300
	11th to 20th	Day	17% 10% 39% 27% 7% 1	300
	21st to end	Day	16% 12% 42% 24% 6%	330
February	1st to 10th	Day	14% 19% 45% 15% 5% 1	300
	11th to 20th	Day	17% 17% 41% 17% 5% 3	300
	21st to end	Day	17% 23% 44% 12% 4	237
March	1st to 10th	Day	12% 15% 41% 25% 6%	270
	11th to 20th	Day	11% 23% 41% 17% 5% 3	270
	21st to end	Day	18% 18% 34% 19% 9% 2	401
April	1st to 10th	Day	22% 16% 34% 18% 9% 1	460
	11th to 20th	Day	26% 14% 28% 21% 9% 1	465
	21st to end	Day	26% 15% 29% 21% 8% 2	650
May	1st to 10th	Day	25% 18% 31% 19% 5% 2	653
	11th to 20th	Day	21% 14% 33% 20% 9% 3	675
	21st to end	Day	24% 12% 30% 25% 7% 2	734
June	1st to 10th	Day	21% 14% 30% 23% 10% 3	680
	11th to 20th	Day	18% 18% 34% 20% 7% 3	680
	21st to end	Day	21% 10% 29% 24% 11% 4	680
July	1st to 10th	Day	11% 10% 33% 26% 14% 6%	671
	11th to 20th	Day	16% 11% 29% 25% 15% 5%	668
	21st to end	Day	12% 9% 31% 25% 17% 6%	739
August	1st to 10th	Day	14% 9% 32% 27% 15% 3	676
	11th to 20th	Day	18% 8% 24% 28% 17% 5%	665
	21st to end	Day	20% 9% 30% 24% 15% 2	629
September	1st to 10th	Day	16% 14% 31% 25% 13% 2	490
	11th to 20th	Day	22% 13% 30% 22% 11% 2	490
	21st to end	Day	29% 16% 28% 18% 9% 1	371
October	1st to 10th	Day	24% 19% 29% 17% 8% 2	300
	11th to 20th	Day	23% 19% 36% 18% 4	300
	21st to end	Day	36% 19% 32% 10% 2 1	330
November	1st to 10th	Day	26% 17% 34% 16% 6% 1	300
	11th to 20th	Day	25% 20% 36% 15% 3	300
	21st to end	Day	26% 20% 37% 14% 3 1	300
December	1st to 10th	Day	16% 18% 45% 16% 4	300
	11th to 20th	Day	19% 17% 42% 17% 5%	300
	21st to end	Day	22% 14% 37% 22% 4 2	330
January	1st to 10th	Night	16% 12% 38% 26% 8% 1	1000
	11th to 20th	Night	18% 12% 38% 24% 7% 1	1000
	21st to end	Night	18% 12% 39% 25% 7%	1100
February	1st to 10th	Night	15% 14% 37% 26% 9% 1	1000
	11th to 20th	Night	14% 14% 34% 28% 8% 2	979
	21st to end	Night	13% 15% 35% 26% 10% 1	734
March	1st to 10th	Night	16% 14% 35% 26% 9%	760
	11th to 20th	Night	17% 15% 35% 22% 9% 1	570
	21st to end	Night	22% 11% 28% 26% 10% 3	627
April	1st to 10th	Night	20% 13% 34% 26% 7%	570
	11th to 20th	Night	21% 12% 32% 24% 10%	563
	21st to end	Night	23% 8% 28% 29% 10% 1	570
May	1st to 10th	Night	22% 10% 33% 27% 7% 1	570
	11th to 20th	Night	20% 12% 30% 24% 12% 1	561
	21st to end	Night	21% 8% 27% 32% 11%	617
June	1st to 10th	Night	21% 7% 29% 29% 14%	570
	11th to 20th	Night	16% 6% 33% 35% 11%	570
	21st to end	Night	16% 6% 25% 36% 16% 1	570
July	1st to 10th	Night	10% 6% 28% 37% 18% 1	555
	11th to 20th	Night	11% 6% 31% 30% 20% 2	552
	21st to end	Night	9% 6% 26% 36% 21% 2	624
August	1st to 10th	Night	11% 4 29% 38% 17% 1	567
	11th to 20th	Night	14% 8% 22% 31% 23% 3	564
	21st to end	Night	19% 7% 25% 32% 16% 1	627
September	1st to 10th	Night	15% 7% 27% 33% 18% 1	570
	11th to 20th	Night	20% 7% 28% 27% 16% 1	570
	21st to end	Night	28% 10% 27% 25% 9% 2	708
October	1st to 10th	Night	26% 11% 30% 23% 8% 1	760
	11th to 20th	Night	28% 13% 30% 23% 6% 1	760
	21st to end	Night	28% 13% 31% 23% 5%	836
November	1st to 10th	Night	26% 12% 31% 24% 6% 1	930
	11th to 20th	Night	27% 14% 32% 20% 7% 1	1000
	21st to end	Night	23% 17% 37% 19% 4	1000
December	1st to 10th	Night	19% 13% 38% 24% 6% 1	1000
	11th to 20th	Night	20% 14% 36% 23% 7% 1	1000
	21st to end	Night	25% 12% 31% 23% 7% 1	1100

Page generated at 2025-02-22 06:51:36. Version ac07

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