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 2026-09-14.

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	15% 10% 4 9% 5% 5% 4 3 5% 6% 34%	149815
	Night	17% 14% 5% 12% 6% 4 4 3 4 5% 26%	141262
Transparency	Day	49% 8% 12% 20% 10% 1	153376
	Night	58% 7% 10% 16% 8% 1	145790
Seeing	Day	18% 10% 25% 27% 15% 4	17452
	Night	22% 12% 27% 25% 13% 2	26424

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% 19% 11% 20% 15% 4 3 2 2 2 6%	4094
	11th to 20th	Day	11% 20% 10% 25% 13% 7% 4 2 3 2 2	4965
	21st to end	Day	10% 17% 8% 21% 11% 8% 6% 3 3 3 8%	5780
February	1st to 10th	Day	13% 17% 7% 20% 9% 6% 4 2 4 4 14%	1890
	11th to 20th	Day	13% 16% 6% 17% 8% 6% 5% 3 4 5% 16%	1843
	21st to end	Day	15% 17% 6% 13% 7% 7% 4 3 5% 4 20%	1625
March	1st to 10th	Day	18% 11% 4 9% 6% 5% 4 4 5% 4 31%	4987
	11th to 20th	Day	13% 12% 4 10% 6% 5% 5% 4 5% 6% 28%	5090
	21st to end	Day	17% 11% 4 11% 5% 4 4 3 4 6% 30%	5586
April	1st to 10th	Day	19% 11% 3 8% 5% 5% 4 3 5% 6% 32%	2454
	11th to 20th	Day	20% 9% 2 5% 4 4 4 3 4 6% 39%	2652
	21st to end	Day	20% 9% 3 7% 4 3 4 2 5% 7% 37%	2730
May	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 5% 7% 42%	7642
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 4 5% 7% 41%	8162
	21st to end	Day	18% 7% 2 6% 4 4 4 3 5% 6% 42%	9060
June	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 6% 7% 42%	3001
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 9% 45%	3150
	21st to end	Day	14% 6% 2 5% 4 4 4 4 7% 7% 43%	3150
July	1st to 10th	Day	13% 5% 3 6% 4 4 4 3 5% 9% 44%	8879
	11th to 20th	Day	10% 4 1 4 3 3 3 3 5% 8% 54%	8604
	21st to end	Day	10% 4 2 5% 4 4 4 3 5% 7% 52%	8425
August	1st to 10th	Day	17% 6% 2 5% 3 4 4 3 5% 7% 43%	6014
	11th to 20th	Day	13% 5% 2 6% 3 3 4 3 5% 8% 47%	5951
	21st to end	Day	16% 6% 3 6% 4 4 4 4 6% 8% 41%	6458
September	1st to 10th	Day	14% 6% 2 6% 5% 4 4 4 4 7% 43%	2520
	11th to 20th	Day	13% 5% 2 5% 3 4 4 3 5% 6% 49%	2274
	21st to end	Day	18% 7% 2 7% 5% 5% 5% 3 4 6% 38%	2187
October	1st to 10th	Day	20% 8% 2 6% 4 5% 4 4 5% 7% 36%	2000
	11th to 20th	Day	24% 12% 3 9% 6% 4 5% 3 4 6% 24%	2000
	21st to end	Day	32% 14% 3 10% 4 4 4 3 4 4 18%	2171
November	1st to 10th	Day	21% 18% 4 9% 5% 4 4 3 4 6% 22%	1739
	11th to 20th	Day	18% 23% 6% 11% 5% 5% 4 3 4 5% 16%	1680
	21st to end	Day	22% 28% 6% 12% 5% 5% 4 3 4 4 9%	1680
December	1st to 10th	Day	19% 33% 10% 15% 5% 4 3 2 2 3 4	2680
	11th to 20th	Day	18% 22% 9% 21% 6% 5% 3 2 3 3 8%	3066
	21st to end	Day	25% 19% 8% 15% 7% 8% 4 2 2 2 8%	3626
January	1st to 10th	Night	14% 24% 11% 22% 12% 4 3 2 2 2 5%	8831
	11th to 20th	Night	13% 23% 12% 24% 11% 4 3 2 2 2 4	7904
	21st to end	Night	11% 17% 8% 21% 13% 7% 7% 2 3 3 9%	8401
February	1st to 10th	Night	14% 18% 7% 19% 8% 5% 4 3 4 4 15%	2730
	11th to 20th	Night	13% 17% 7% 17% 7% 6% 5% 3 4 4 18%	2663
	21st to end	Night	17% 14% 5% 14% 7% 5% 5% 3 4 4 21%	2176
March	1st to 10th	Night	17% 12% 4 9% 5% 5% 4 3 5% 7% 28%	5072
	11th to 20th	Night	11% 12% 5% 10% 6% 4 5% 4 5% 7% 30%	5089
	21st to end	Night	20% 12% 5% 13% 5% 4 4 3 4 4 26%	5588
April	1st to 10th	Night	20% 11% 3 9% 6% 4 5% 3 5% 6% 30%	2164
	11th to 20th	Night	19% 9% 3 6% 4 5% 4 2 5% 7% 35%	1935
	21st to end	Night	18% 9% 4 9% 5% 4 5% 3 5% 7% 32%	1890
May	1st to 10th	Night	16% 7% 3 7% 5% 4 4 4 5% 7% 37%	5257
	11th to 20th	Night	16% 6% 2 7% 4 4 4 3 6% 7% 41%	4698
	21st to end	Night	17% 6% 2 6% 4 4 4 3 5% 6% 44%	5114
June	1st to 10th	Night	15% 6% 2 6% 5% 5% 4 4 6% 7% 40%	1613
	11th to 20th	Night	11% 5% 2 4 5% 4 6% 5% 7% 9% 42%	1470
	21st to end	Night	13% 7% 2 7% 4 5% 3 3 6% 7% 41%	1470
July	1st to 10th	Night	12% 6% 2 7% 4 4 4 4 5% 7% 44%	4110
	11th to 20th	Night	12% 4 2 5% 4 4 4 3 6% 8% 49%	4355
	21st to end	Night	11% 5% 2 6% 3 4 4 3 6% 8% 48%	5635
August	1st to 10th	Night	14% 6% 3 6% 4 4 5% 4 5% 6% 43%	4135
	11th to 20th	Night	16% 5% 2 5% 4 3 4 3 4 6% 48%	4095
	21st to end	Night	20% 6% 3 7% 4 4 4 3 5% 6% 39%	4621
September	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 7% 8% 44%	2100
	11th to 20th	Night	15% 5% 2 4 4 3 5% 3 5% 7% 46%	2190
	21st to end	Night	20% 6% 3 6% 5% 5% 4 3 5% 6% 38%	2211
October	1st to 10th	Night	22% 8% 2 7% 4 4 4 3 4 6% 36%	2400
	11th to 20th	Night	27% 11% 3 9% 4 5% 4 3 4 6% 25%	2400
	21st to end	Night	30% 16% 4 7% 4 4 3 3 5% 4 19%	2665
November	1st to 10th	Night	22% 18% 4 8% 5% 4 4 3 4 5% 24%	2777
	11th to 20th	Night	19% 25% 5% 11% 5% 4 3 4 4 5% 16%	2940
	21st to end	Night	24% 28% 7% 10% 4 4 4 2 3 3 11%	2940
December	1st to 10th	Night	22% 34% 9% 15% 4 3 3 2 2 2 4	4720
	11th to 20th	Night	17% 23% 10% 21% 6% 4 4 2 3 3 7%	5348
	21st to end	Night	23% 22% 9% 16% 6% 6% 4 2 2 3 7%	7555

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% 10% 6% 3	4095
	11th to 20th	Day	85% 9% 3 2 1	4999
	21st to end	Day	74% 11% 9% 4 2	5780
February	1st to 10th	Day	72% 8% 9% 9% 3	1890
	11th to 20th	Day	67% 7% 11% 10% 4	1852
	21st to end	Day	65% 8% 11% 12% 4	1625
March	1st to 10th	Day	53% 9% 14% 11% 12% 1	4990
	11th to 20th	Day	54% 8% 13% 18% 6% 2	5090
	21st to end	Day	53% 7% 11% 18% 9% 1	5586
April	1st to 10th	Day	53% 6% 10% 20% 10% 1	2454
	11th to 20th	Day	47% 6% 8% 23% 14% 1	2652
	21st to end	Day	48% 6% 12% 20% 12% 2	2730
May	1st to 10th	Day	39% 7% 14% 23% 13% 4	7651
	11th to 20th	Day	40% 10% 12% 21% 17% 1	8166
	21st to end	Day	42% 6% 10% 24% 15% 2	9061
June	1st to 10th	Day	39% 9% 12% 23% 17% 1	3001
	11th to 20th	Day	36% 7% 14% 26% 16% 1	3150
	21st to end	Day	39% 9% 14% 24% 14% 1	3150
July	1st to 10th	Day	37% 7% 17% 25% 13% 1	8806
	11th to 20th	Day	28% 6% 12% 38% 16% 1	8523
	21st to end	Day	32% 7% 14% 31% 15% 1	8239
August	1st to 10th	Day	40% 7% 15% 22% 14% 1	6001
	11th to 20th	Day	34% 7% 21% 28% 10%	5990
	21st to end	Day	40% 8% 15% 28% 8%	6458
September	1st to 10th	Day	40% 8% 15% 26% 10% 1	2520
	11th to 20th	Day	35% 8% 15% 30% 12%	2274
	21st to end	Day	47% 9% 11% 24% 8%	2187
October	1st to 10th	Day	43% 8% 14% 24% 10% 1	3260
	11th to 20th	Day	52% 7% 11% 23% 7%	3240
	21st to end	Day	63% 8% 11% 13% 4	3485
November	1st to 10th	Day	62% 9% 9% 14% 5%	1739
	11th to 20th	Day	70% 8% 10% 8% 4	1680
	21st to end	Day	78% 8% 8% 5% 1	1680
December	1st to 10th	Day	87% 6% 4 2	2680
	11th to 20th	Day	81% 7% 6% 6%	3066
	21st to end	Day	79% 9% 5% 6% 1	3626
January	1st to 10th	Night	83% 9% 5% 3 1	8831
	11th to 20th	Night	84% 9% 4 2 1	7945
	21st to end	Night	75% 9% 9% 4 3	8401
February	1st to 10th	Night	72% 6% 9% 10% 3	2730
	11th to 20th	Night	68% 8% 9% 12% 4	2665
	21st to end	Night	63% 7% 12% 13% 5%	2176
March	1st to 10th	Night	52% 9% 11% 16% 11% 2	5082
	11th to 20th	Night	49% 9% 17% 16% 8% 1	5090
	21st to end	Night	57% 8% 9% 14% 10% 1	5588
April	1st to 10th	Night	55% 6% 9% 18% 10% 1	2164
	11th to 20th	Night	50% 5% 7% 21% 15% 2	1935
	21st to end	Night	51% 7% 11% 15% 16% 1	1890
May	1st to 10th	Night	44% 7% 10% 21% 14% 4	5264
	11th to 20th	Night	41% 8% 10% 22% 17% 1	4699
	21st to end	Night	40% 6% 10% 27% 15% 2	5115
June	1st to 10th	Night	41% 8% 11% 20% 19% 1	1613
	11th to 20th	Night	36% 7% 12% 26% 18% 1	1470
	21st to end	Night	40% 8% 12% 26% 13% 1	1470
July	1st to 10th	Night	38% 7% 15% 25% 13% 2	4075
	11th to 20th	Night	33% 6% 13% 34% 14% 1	4313
	21st to end	Night	33% 7% 10% 33% 17% 1	5506
August	1st to 10th	Night	40% 6% 12% 23% 17% 1	4124
	11th to 20th	Night	36% 6% 20% 28% 9%	4122
	21st to end	Night	45% 6% 13% 26% 10% 1	4621
September	1st to 10th	Night	35% 8% 15% 29% 12% 1	2100
	11th to 20th	Night	35% 9% 14% 27% 15%	2190
	21st to end	Night	46% 8% 13% 23% 10%	2211
October	1st to 10th	Night	41% 7% 11% 26% 16%	3920
	11th to 20th	Night	52% 5% 15% 19% 9%	3899
	21st to end	Night	56% 7% 14% 19% 4	4301
November	1st to 10th	Night	61% 7% 11% 16% 5%	2777
	11th to 20th	Night	69% 7% 11% 8% 3 1	2940
	21st to end	Night	78% 8% 8% 6% 1	2940
December	1st to 10th	Night	88% 6% 3 2 1	4720
	11th to 20th	Night	82% 8% 7% 4	5348
	21st to end	Night	83% 6% 6% 5% 1	7555

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	18% 20% 37% 17% 6% 1	220
	11th to 20th	Day	18% 20% 40% 16% 5%	299
	21st to end	Day	23% 12% 36% 24% 5%	363
February	1st to 10th	Day	22% 20% 32% 20% 5% 1	330
	11th to 20th	Day	18% 16% 41% 21% 3 1	330
	21st to end	Day	21% 24% 30% 23% 1	273
March	1st to 10th	Day	19% 12% 38% 25% 6%	509
	11th to 20th	Day	20% 16% 32% 26% 6% 1	540
	21st to end	Day	26% 11% 31% 23% 8%	594
April	1st to 10th	Day	20% 14% 31% 26% 8% 1	540
	11th to 20th	Day	28% 11% 26% 19% 12% 4	532
	21st to end	Day	23% 12% 26% 28% 9% 2	540
May	1st to 10th	Day	18% 7% 27% 33% 13% 3	543
	11th to 20th	Day	14% 5% 23% 34% 19% 5%	567
	21st to end	Day	16% 5% 25% 29% 20% 6%	617
June	1st to 10th	Day	17% 6% 20% 32% 23% 2	631
	11th to 20th	Day	13% 5% 22% 37% 19% 4	780
	21st to end	Day	17% 4 20% 35% 19% 4	780
July	1st to 10th	Day	10% 3 16% 39% 26% 6%	771
	11th to 20th	Day	12% 5% 20% 32% 25% 6%	674
	21st to end	Day	9% 4 18% 40% 24% 5%	620
August	1st to 10th	Day	12% 5% 16% 32% 26% 8%	566
	11th to 20th	Day	13% 5% 13% 33% 26% 11%	559
	21st to end	Day	14% 6% 22% 30% 23% 6%	627
September	1st to 10th	Day	14% 7% 22% 27% 22% 8%	570
	11th to 20th	Day	12% 4 19% 24% 27% 15%	542
	21st to end	Day	17% 8% 20% 26% 22% 6%	530
October	1st to 10th	Day	21% 10% 22% 24% 18% 5%	530
	11th to 20th	Day	23% 16% 27% 25% 7% 1	530
	21st to end	Day	34% 16% 25% 18% 6%	554
November	1st to 10th	Day	26% 22% 23% 23% 6%	269
	11th to 20th	Day	25% 21% 31% 19% 2 1	220
	21st to end	Day	32% 18% 37% 13%	220
December	1st to 10th	Day	25% 23% 31% 16% 4	220
	11th to 20th	Day	30% 28% 26% 12% 4	220
	21st to end	Day	33% 18% 35% 10% 5%	242
January	1st to 10th	Night	26% 21% 31% 16% 5%	1050
	11th to 20th	Night	28% 18% 32% 18% 4 1	878
	21st to end	Night	20% 14% 35% 23% 7% 1	924
February	1st to 10th	Night	21% 19% 34% 21% 5%	840
	11th to 20th	Night	19% 14% 36% 24% 7%	823
	21st to end	Night	22% 15% 34% 24% 5%	692
March	1st to 10th	Night	21% 11% 36% 26% 6%	840
	11th to 20th	Night	18% 14% 36% 25% 6% 1	840
	21st to end	Night	22% 10% 28% 28% 11% 1	924
April	1st to 10th	Night	24% 11% 29% 30% 6%	840
	11th to 20th	Night	22% 9% 28% 26% 13% 1	691
	21st to end	Night	21% 9% 26% 29% 15%	630
May	1st to 10th	Night	18% 4 20% 39% 17% 1	630
	11th to 20th	Night	17% 4 24% 38% 15% 3	435
	21st to end	Night	14% 2 19% 40% 23% 2	455
June	1st to 10th	Night	15% 6% 20% 40% 17% 3	420
	11th to 20th	Night	14% 4 20% 38% 23% 2	420
	21st to end	Night	16% 4 20% 34% 24% 2	420
July	1st to 10th	Night	10% 3 11% 42% 32% 2	410
	11th to 20th	Night	10% 4 19% 33% 30% 3	408
	21st to end	Night	9% 2 19% 38% 30% 2	652
August	1st to 10th	Night	12% 4 15% 34% 30% 5%	627
	11th to 20th	Night	13% 4 16% 32% 30% 6%	624
	21st to end	Night	17% 5% 21% 26% 27% 3	730
September	1st to 10th	Night	13% 7% 20% 30% 23% 7%	840
	11th to 20th	Night	15% 5% 16% 31% 26% 7%	813
	21st to end	Night	19% 9% 17% 32% 18% 5%	800
October	1st to 10th	Night	24% 9% 26% 25% 15% 2	800
	11th to 20th	Night	30% 14% 24% 23% 8% 2	800
	21st to end	Night	37% 13% 26% 18% 5%	880
November	1st to 10th	Night	29% 16% 28% 18% 8% 1	820
	11th to 20th	Night	28% 21% 29% 16% 6%	840
	21st to end	Night	35% 18% 28% 15% 4	840
December	1st to 10th	Night	34% 22% 27% 13% 3	840
	11th to 20th	Night	26% 24% 34% 13% 3	840
	21st to end	Night	31% 19% 32% 16% 2	1108

Page generated at 2026-09-11 04:11:54. Version ac07

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