Chimnissing
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chimnissing clear sky chart from 2005-11-06 to 2025-05-11.

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% 11% 4 10% 6% 5% 4 3 5% 6% 32%	113985
	Night	17% 15% 6% 12% 6% 4 4 3 4 5% 24%	114940
Transparency	Day	51% 8% 12% 18% 9% 1	117589
	Night	59% 8% 10% 15% 8% 1	119500
Seeing	Day	19% 10% 25% 27% 15% 4	15604
	Night	22% 12% 27% 25% 12% 2	24833

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	14% 20% 12% 19% 16% 5% 3 2 2 2 5%	3158
	11th to 20th	Day	11% 19% 11% 26% 12% 7% 4 2 3 2 3	3813
	21st to end	Day	13% 19% 9% 19% 9% 6% 6% 3 4 4 8%	4466
February	1st to 10th	Day	13% 17% 7% 20% 9% 7% 4 2 4 4 13%	1800
	11th to 20th	Day	13% 16% 6% 16% 8% 6% 5% 3 4 5% 17%	1753
	21st to end	Day	15% 17% 6% 13% 7% 7% 4 3 5% 4 20%	1550
March	1st to 10th	Day	18% 11% 4 8% 6% 5% 4 3 5% 4 31%	4878
	11th to 20th	Day	13% 12% 4 10% 6% 6% 5% 4 5% 7% 28%	4980
	21st to end	Day	17% 10% 4 11% 5% 4 4 3 4 6% 31%	5465
April	1st to 10th	Day	19% 11% 3 8% 5% 5% 4 3 5% 6% 32%	2337
	11th to 20th	Day	19% 9% 2 5% 4 4 4 3 4 6% 39%	2524
	21st to end	Day	20% 9% 2 7% 4 3 4 2 5% 7% 37%	2600
May	1st to 10th	Day	17% 7% 3 6% 5% 4 3 3 5% 7% 40%	4238
	11th to 20th	Day	13% 7% 3 7% 5% 5% 4 3 6% 6% 40%	4366
	21st to end	Day	14% 6% 2 6% 4 4 4 3 5% 7% 45%	4837
June	1st to 10th	Day	15% 6% 2 6% 4 4 5% 4 6% 7% 41%	2715
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 6% 8% 46%	2850
	21st to end	Day	14% 6% 2 5% 3 4 4 4 6% 7% 43%	2850
July	1st to 10th	Day	13% 5% 2 6% 5% 4 5% 4 6% 9% 41%	4760
	11th to 20th	Day	12% 5% 2 4 3 3 3 3 5% 7% 53%	4610
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 7% 53%	4510
August	1st to 10th	Day	13% 6% 2 5% 4 4 4 4 6% 8% 44%	4104
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 6% 8% 43%	4044
	21st to end	Day	10% 4 3 5% 4 4 4 4 6% 8% 48%	4441
September	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 4 4 7% 43%	2280
	11th to 20th	Day	14% 5% 3 5% 4 4 4 3 5% 7% 47%	2127
	21st to end	Day	18% 6% 2 8% 5% 5% 5% 3 4 6% 37%	2078
October	1st to 10th	Day	21% 8% 2 7% 4 5% 4 4 4 7% 35%	1900
	11th to 20th	Day	24% 12% 3 9% 6% 4 5% 3 4 6% 24%	1900
	21st to end	Day	32% 15% 3 10% 4 4 4 3 4 4 18%	2063
November	1st to 10th	Day	21% 17% 4 9% 5% 4 4 3 4 6% 22%	1655
	11th to 20th	Day	18% 22% 6% 12% 5% 5% 4 4 4 5% 16%	1600
	21st to end	Day	23% 28% 6% 12% 5% 4 4 3 4 4 9%	1600
December	1st to 10th	Day	20% 33% 11% 15% 5% 4 3 2 3 3 3	2600
	11th to 20th	Day	18% 23% 9% 21% 6% 5% 3 2 3 3 8%	2986
	21st to end	Day	25% 20% 8% 15% 7% 8% 4 2 2 2 8%	3547
January	1st to 10th	Night	15% 25% 11% 21% 12% 4 3 2 1 2 4	6808
	11th to 20th	Night	13% 20% 12% 25% 10% 5% 4 3 3 2 4	6054
	21st to end	Night	14% 18% 9% 19% 10% 6% 5% 2 4 3 9%	6490
February	1st to 10th	Night	14% 18% 8% 19% 8% 5% 5% 3 4 4 13%	2600
	11th to 20th	Night	13% 17% 7% 17% 7% 5% 5% 2 4 4 18%	2533
	21st to end	Night	17% 13% 5% 14% 7% 5% 5% 4 4 5% 22%	2075
March	1st to 10th	Night	17% 12% 5% 10% 5% 5% 4 3 5% 7% 28%	4961
	11th to 20th	Night	11% 12% 5% 10% 5% 4 5% 4 5% 7% 30%	4979
	21st to end	Night	21% 12% 5% 13% 5% 4 4 3 4 4 27%	5467
April	1st to 10th	Night	20% 11% 3 9% 6% 4 5% 3 5% 5% 30%	2061
	11th to 20th	Night	19% 9% 3 6% 4 5% 4 2 5% 7% 35%	1842
	21st to end	Night	18% 9% 4 9% 5% 4 5% 3 5% 7% 32%	1800
May	1st to 10th	Night	15% 7% 3 6% 6% 4 4 4 5% 7% 38%	2923
	11th to 20th	Night	16% 6% 3 7% 4 5% 4 3 6% 7% 38%	2533
	21st to end	Night	10% 6% 3 6% 5% 4 4 3 5% 7% 46%	2738
June	1st to 10th	Night	15% 6% 2 7% 5% 5% 4 4 6% 8% 38%	1459
	11th to 20th	Night	10% 5% 2 4 5% 4 6% 5% 7% 9% 43%	1330
	21st to end	Night	13% 8% 2 7% 5% 5% 3 4 6% 7% 41%	1330
July	1st to 10th	Night	11% 6% 3 8% 4 4 3 4 5% 7% 46%	2210
	11th to 20th	Night	14% 4 1 5% 3 3 4 3 5% 6% 51%	2351
	21st to end	Night	9% 4 1 6% 3 4 5% 3 6% 8% 50%	3040
August	1st to 10th	Night	12% 5% 2 6% 4 5% 5% 4 6% 7% 45%	2825
	11th to 20th	Night	16% 6% 3 6% 4 3 4 3 5% 7% 43%	2785
	21st to end	Night	15% 5% 2 6% 4 3 4 3 4 7% 47%	3183
September	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 7% 8% 44%	1900
	11th to 20th	Night	16% 5% 2 5% 4 3 4 3 5% 8% 45%	2050
	21st to end	Night	21% 6% 3 6% 5% 4 4 3 5% 6% 38%	2100
October	1st to 10th	Night	22% 8% 2 8% 5% 5% 4 3 4 5% 34%	2280
	11th to 20th	Night	26% 12% 3 9% 5% 5% 4 3 4 6% 24%	2280
	21st to end	Night	31% 16% 4 8% 4 4 3 3 5% 5% 18%	2532
November	1st to 10th	Night	22% 17% 4 8% 5% 4 4 3 4 5% 24%	2641
	11th to 20th	Night	19% 23% 6% 11% 5% 4 3 4 4 5% 17%	2800
	21st to end	Night	24% 28% 7% 10% 4 4 4 2 3 3 11%	2800
December	1st to 10th	Night	22% 34% 9% 15% 4 3 3 2 2 2 4	4580
	11th to 20th	Night	17% 24% 10% 20% 6% 4 4 2 3 3 7%	5208
	21st to end	Night	23% 22% 9% 16% 6% 6% 4 2 3 3 7%	7392

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	80% 12% 5% 3	3159
	11th to 20th	Day	83% 11% 4 2 1	3847
	21st to end	Day	75% 11% 8% 5% 2	4466
February	1st to 10th	Day	73% 8% 9% 8% 2	1800
	11th to 20th	Day	66% 7% 12% 10% 4	1762
	21st to end	Day	65% 8% 11% 12% 4	1550
March	1st to 10th	Day	53% 9% 14% 11% 13% 1	4881
	11th to 20th	Day	53% 8% 13% 18% 6% 2	4980
	21st to end	Day	52% 7% 11% 19% 9% 1	5465
April	1st to 10th	Day	53% 6% 10% 20% 10% 1	2337
	11th to 20th	Day	47% 6% 8% 23% 15% 1	2524
	21st to end	Day	48% 6% 12% 19% 13% 2	2600
May	1st to 10th	Day	41% 8% 12% 21% 15% 2	4250
	11th to 20th	Day	38% 12% 15% 22% 12% 1	4370
	21st to end	Day	36% 9% 13% 20% 19% 3	4837
June	1st to 10th	Day	40% 9% 12% 23% 15% 1	2715
	11th to 20th	Day	35% 7% 13% 25% 17% 1	2850
	21st to end	Day	39% 9% 14% 23% 14% 1	2850
July	1st to 10th	Day	38% 8% 17% 22% 13% 1	4686
	11th to 20th	Day	30% 7% 14% 35% 12% 1	4529
	21st to end	Day	31% 8% 12% 29% 19% 1	4366
August	1st to 10th	Day	36% 8% 15% 26% 13% 1	4091
	11th to 20th	Day	38% 8% 18% 24% 11%	4083
	21st to end	Day	32% 8% 14% 34% 11% 1	4441
September	1st to 10th	Day	41% 8% 15% 26% 11% 1	2280
	11th to 20th	Day	36% 8% 16% 27% 12%	2127
	21st to end	Day	47% 9% 12% 24% 8%	2078
October	1st to 10th	Day	44% 8% 14% 23% 10% 1	3160
	11th to 20th	Day	52% 7% 11% 23% 7%	3140
	21st to end	Day	64% 8% 11% 13% 3	3377
November	1st to 10th	Day	62% 9% 10% 14% 5%	1655
	11th to 20th	Day	70% 8% 10% 8% 4	1600
	21st to end	Day	78% 8% 8% 6% 1	1600
December	1st to 10th	Day	87% 6% 4 2	2600
	11th to 20th	Day	81% 7% 6% 6%	2986
	21st to end	Day	79% 9% 5% 6% 1	3547
January	1st to 10th	Night	84% 9% 4 2	6808
	11th to 20th	Night	82% 11% 5% 2 1	6095
	21st to end	Night	75% 10% 8% 5% 2	6490
February	1st to 10th	Night	74% 6% 9% 9% 2	2600
	11th to 20th	Night	67% 8% 9% 12% 4	2535
	21st to end	Night	62% 7% 12% 13% 5%	2075
March	1st to 10th	Night	53% 9% 11% 15% 11% 2	4971
	11th to 20th	Night	49% 9% 18% 16% 8% 1	4980
	21st to end	Night	57% 8% 9% 14% 10% 1	5467
April	1st to 10th	Night	55% 6% 9% 18% 11% 1	2061
	11th to 20th	Night	50% 5% 7% 21% 15% 2	1842
	21st to end	Night	51% 7% 11% 13% 16% 1	1800
May	1st to 10th	Night	42% 9% 13% 20% 14% 2	2930
	11th to 20th	Night	40% 9% 13% 22% 14% 2	2534
	21st to end	Night	34% 8% 13% 24% 19% 2	2739
June	1st to 10th	Night	42% 9% 11% 19% 18% 1	1459
	11th to 20th	Night	35% 7% 12% 25% 20% 1	1330
	21st to end	Night	40% 8% 12% 25% 13% 1	1330
July	1st to 10th	Night	37% 7% 13% 23% 17% 3	2175
	11th to 20th	Night	34% 6% 12% 35% 13% 1	2309
	21st to end	Night	32% 7% 11% 30% 18% 1	2943
August	1st to 10th	Night	37% 7% 14% 26% 15% 1	2814
	11th to 20th	Night	39% 7% 18% 24% 12% 1	2812
	21st to end	Night	37% 6% 12% 31% 13% 1	3183
September	1st to 10th	Night	35% 8% 15% 28% 13% 1	1900
	11th to 20th	Night	37% 9% 14% 26% 14%	2050
	21st to end	Night	46% 8% 13% 24% 9%	2100
October	1st to 10th	Night	42% 7% 11% 25% 15%	3800
	11th to 20th	Night	52% 6% 15% 19% 9%	3779
	21st to end	Night	56% 7% 14% 19% 4	4168
November	1st to 10th	Night	60% 7% 11% 16% 5%	2641
	11th to 20th	Night	68% 7% 12% 8% 3 1	2800
	21st to end	Night	77% 8% 8% 6% 1	2800
December	1st to 10th	Night	88% 6% 3 2 1	4580
	11th to 20th	Night	81% 8% 7% 4	5208
	21st to end	Night	83% 6% 6% 5% 1	7392

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	19% 20% 37% 17% 7% 2	200
	11th to 20th	Day	19% 19% 39% 17% 6%	272
	21st to end	Day	25% 10% 36% 24% 5%	330
February	1st to 10th	Day	24% 21% 34% 17% 4	300
	11th to 20th	Day	17% 18% 41% 21% 3 1	300
	21st to end	Day	22% 25% 31% 22% 1	249
March	1st to 10th	Day	20% 12% 38% 23% 6%	470
	11th to 20th	Day	17% 15% 33% 27% 6% 1	500
	21st to end	Day	25% 11% 30% 24% 9%	550
April	1st to 10th	Day	19% 14% 31% 26% 9% 1	500
	11th to 20th	Day	27% 11% 26% 20% 12% 4	492
	21st to end	Day	24% 12% 26% 27% 8% 2	500
May	1st to 10th	Day	18% 7% 25% 33% 13% 3	503
	11th to 20th	Day	15% 5% 22% 34% 19% 5%	487
	21st to end	Day	14% 4 23% 30% 22% 7%	529
June	1st to 10th	Day	17% 6% 20% 31% 23% 2	545
	11th to 20th	Day	13% 5% 21% 37% 20% 5%	680
	21st to end	Day	18% 5% 20% 35% 19% 4	680
July	1st to 10th	Day	10% 3 16% 38% 26% 6%	671
	11th to 20th	Day	12% 5% 20% 31% 26% 7%	583
	21st to end	Day	9% 4 18% 39% 23% 6%	532
August	1st to 10th	Day	13% 5% 17% 32% 24% 9%	486
	11th to 20th	Day	13% 6% 12% 31% 26% 12%	479
	21st to end	Day	14% 6% 21% 29% 23% 7%	539
September	1st to 10th	Day	14% 7% 23% 27% 22% 9%	490
	11th to 20th	Day	12% 4 20% 23% 28% 13%	490
	21st to end	Day	18% 8% 22% 24% 22% 6%	490
October	1st to 10th	Day	21% 11% 23% 24% 16% 4	490
	11th to 20th	Day	23% 17% 27% 24% 7% 1	490
	21st to end	Day	36% 17% 24% 17% 6%	512
November	1st to 10th	Day	24% 21% 24% 23% 7%	245
	11th to 20th	Day	25% 22% 32% 19% 3 1	200
	21st to end	Day	32% 17% 39% 13% 1	200
December	1st to 10th	Day	26% 23% 31% 17% 4 1	200
	11th to 20th	Day	30% 29% 25% 13% 5%	200
	21st to end	Day	33% 17% 35% 10% 5%	220
January	1st to 10th	Night	26% 21% 31% 16% 5% 1	1000
	11th to 20th	Night	28% 18% 31% 19% 4 1	836
	21st to end	Night	20% 13% 34% 24% 7% 1	880
February	1st to 10th	Night	21% 19% 35% 21% 4	800
	11th to 20th	Night	20% 13% 36% 24% 6%	783
	21st to end	Night	22% 15% 34% 25% 6%	660
March	1st to 10th	Night	21% 11% 36% 25% 7%	800
	11th to 20th	Night	18% 13% 37% 25% 7% 1	800
	21st to end	Night	22% 9% 27% 29% 12% 1	880
April	1st to 10th	Night	24% 11% 29% 30% 6% 1	800
	11th to 20th	Night	22% 9% 28% 26% 14% 1	658
	21st to end	Night	22% 9% 27% 29% 14%	600
May	1st to 10th	Night	18% 4 20% 39% 18% 2	600
	11th to 20th	Night	17% 3 23% 38% 15% 3	395
	21st to end	Night	12% 2 19% 40% 25% 2	411
June	1st to 10th	Night	15% 6% 20% 41% 17% 2	380
	11th to 20th	Night	13% 4 18% 38% 24% 2	380
	21st to end	Night	17% 4 19% 34% 24% 2	380
July	1st to 10th	Night	10% 3 11% 43% 31% 2	370
	11th to 20th	Night	10% 4 20% 32% 31% 4	368
	21st to end	Night	9% 2 19% 38% 30% 2	590
August	1st to 10th	Night	11% 4 15% 34% 29% 6%	567
	11th to 20th	Night	12% 4 16% 31% 31% 6%	564
	21st to end	Night	17% 5% 21% 26% 28% 3	660
September	1st to 10th	Night	13% 6% 21% 30% 22% 7%	760
	11th to 20th	Night	16% 5% 17% 31% 25% 6%	760
	21st to end	Night	19% 9% 18% 31% 17% 6%	760
October	1st to 10th	Night	25% 9% 27% 24% 14% 2	760
	11th to 20th	Night	30% 14% 24% 23% 8% 2	760
	21st to end	Night	37% 14% 26% 17% 5%	836
November	1st to 10th	Night	29% 16% 27% 19% 8% 1	780
	11th to 20th	Night	27% 21% 30% 16% 6%	800
	21st to end	Night	34% 18% 28% 16% 4	800
December	1st to 10th	Night	35% 21% 27% 14% 3	800
	11th to 20th	Night	26% 24% 34% 13% 3 1	800
	21st to end	Night	31% 18% 32% 16% 2	1055

Page generated at 2025-05-08 09:33:57. Version ac07

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