Blind River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blind River 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	14% 10% 3 8% 5% 4 4 4 5% 7% 37%	137602
	Night	15% 12% 4 9% 5% 4 4 3 5% 6% 32%	134951
Transparency	Day	31% 37% 8% 15% 8% 1	141073
	Night	34% 36% 7% 14% 8% 1	139556
Seeing	Day	19% 11% 29% 27% 12% 3	17596
	Night	21% 8% 28% 30% 12% 1	26916

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	11% 19% 6% 12% 6% 5% 4 3 5% 5% 24%	4232
	11th to 20th	Day	9% 18% 6% 15% 7% 6% 6% 4 4 5% 19%	4679
	21st to end	Day	9% 19% 7% 12% 6% 6% 5% 4 5% 6% 21%	5209
February	1st to 10th	Day	10% 14% 4 12% 6% 6% 5% 3 6% 6% 27%	1890
	11th to 20th	Day	12% 14% 4 9% 7% 5% 4 4 5% 6% 29%	1871
	21st to end	Day	11% 14% 5% 10% 7% 5% 5% 4 5% 6% 28%	1730
March	1st to 10th	Day	16% 11% 3 6% 4 4 5% 3 5% 7% 36%	4671
	11th to 20th	Day	12% 12% 4 9% 6% 6% 6% 4 5% 7% 30%	5090
	21st to end	Day	17% 10% 5% 8% 4 4 4 4 5% 6% 33%	5586
April	1st to 10th	Day	17% 11% 3 7% 5% 5% 4 4 5% 6% 32%	2498
	11th to 20th	Day	19% 8% 3 6% 4 4 4 4 5% 7% 37%	2702
	21st to end	Day	18% 9% 2 7% 5% 4 3 3 6% 7% 36%	2730
May	1st to 10th	Day	15% 6% 2 6% 4 4 4 3 5% 7% 44%	7642
	11th to 20th	Day	16% 9% 2 7% 4 4 4 3 4 7% 40%	7805
	21st to end	Day	14% 8% 3 6% 4 4 4 3 4 6% 45%	9689
June	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 6% 8% 42%	3150
	11th to 20th	Day	12% 6% 3 6% 4 4 5% 4 6% 9% 41%	3150
	21st to end	Day	15% 7% 2 6% 4 4 4 4 5% 8% 40%	3150
July	1st to 10th	Day	15% 7% 2 5% 4 4 4 3 5% 8% 43%	6820
	11th to 20th	Day	10% 4 2 5% 4 4 4 3 6% 8% 51%	6597
	21st to end	Day	9% 5% 2 4 3 3 4 4 5% 8% 52%	6910
August	1st to 10th	Day	8% 5% 2 6% 4 5% 4 4 7% 8% 46%	4234
	11th to 20th	Day	13% 5% 2 6% 4 4 4 3 5% 8% 45%	4174
	21st to end	Day	12% 5% 2 6% 4 4 4 4 6% 7% 47%	4675
September	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 5% 7% 44%	2356
	11th to 20th	Day	12% 5% 3 6% 3 4 4 3 6% 9% 46%	2200
	21st to end	Day	17% 8% 3 7% 4 3 3 3 5% 8% 39%	2200
October	1st to 10th	Day	18% 6% 2 7% 5% 4 5% 3 6% 6% 39%	2095
	11th to 20th	Day	21% 9% 3 7% 5% 6% 5% 5% 5% 7% 27%	1999
	21st to end	Day	21% 11% 3 8% 5% 6% 4 4 6% 6% 25%	1980
November	1st to 10th	Day	20% 11% 2 8% 6% 4 4 4 6% 9% 27%	1852
	11th to 20th	Day	15% 16% 6% 10% 7% 4 5% 3 5% 7% 24%	1691
	21st to end	Day	21% 21% 5% 9% 6% 4 4 3 5% 5% 17%	1680
December	1st to 10th	Day	14% 20% 6% 10% 6% 5% 4 4 5% 7% 19%	2421
	11th to 20th	Day	17% 16% 6% 14% 6% 5% 5% 4 5% 7% 14%	2691
	21st to end	Day	29% 21% 6% 9% 4 4 2 2 2 5% 15%	3553
January	1st to 10th	Night	12% 15% 6% 14% 6% 5% 4 3 5% 6% 24%	8678
	11th to 20th	Night	11% 19% 7% 15% 6% 5% 5% 4 5% 5% 18%	8236
	21st to end	Night	9% 14% 6% 14% 8% 7% 6% 4 6% 6% 20%	9000
February	1st to 10th	Night	11% 15% 4 11% 8% 6% 5% 4 5% 6% 26%	2730
	11th to 20th	Night	12% 14% 4 10% 7% 6% 4 4 5% 6% 26%	2631
	21st to end	Night	12% 16% 5% 10% 6% 4 6% 4 5% 5% 27%	2076
March	1st to 10th	Night	17% 10% 3 6% 3 3 4 3 5% 7% 38%	5389
	11th to 20th	Night	14% 11% 4 7% 5% 6% 5% 4 5% 8% 33%	5089
	21st to end	Night	18% 12% 5% 8% 4 3 3 3 4 5% 35%	5588
April	1st to 10th	Night	19% 10% 3 8% 4 4 4 3 5% 7% 33%	2137
	11th to 20th	Night	20% 9% 2 6% 4 4 3 3 4 7% 39%	1867
	21st to end	Night	20% 8% 3 7% 5% 4 4 3 5% 6% 35%	1890
May	1st to 10th	Night	15% 7% 3 8% 5% 4 4 4 6% 6% 39%	5257
	11th to 20th	Night	17% 7% 2 6% 4 3 4 3 5% 6% 42%	5041
	21st to end	Night	15% 8% 2 6% 4 3 3 3 4 6% 45%	4514
June	1st to 10th	Night	13% 5% 3 6% 4 4 5% 4 6% 8% 42%	1470
	11th to 20th	Night	11% 7% 2 7% 6% 5% 5% 4 6% 7% 41%	1470
	21st to end	Night	13% 6% 2 7% 5% 5% 4 3 5% 7% 40%	1470
July	1st to 10th	Night	13% 7% 3 7% 4 4 5% 4 6% 8% 40%	3160
	11th to 20th	Night	9% 4 2 5% 3 4 4 4 5% 7% 52%	3380
	21st to end	Night	9% 5% 2 5% 3 3 4 4 5% 9% 51%	3961
August	1st to 10th	Night	7% 7% 2 7% 5% 4 5% 5% 7% 9% 43%	2915
	11th to 20th	Night	12% 5% 2 5% 3 4 5% 4 7% 9% 43%	2875
	21st to end	Night	10% 5% 2 6% 4 3 4 2 4 6% 53%	3223
September	1st to 10th	Night	13% 5% 2 6% 4 5% 4 4 5% 7% 44%	2020
	11th to 20th	Night	12% 4 1 5% 3 3 3 3 5% 8% 53%	2200
	21st to end	Night	18% 7% 3 7% 4 4 3 3 5% 7% 39%	2200
October	1st to 10th	Night	18% 9% 3 7% 4 3 3 3 5% 6% 40%	2305
	11th to 20th	Night	23% 9% 3 7% 5% 5% 4 4 5% 6% 29%	2400
	21st to end	Night	24% 10% 3 8% 5% 4 5% 3 6% 7% 27%	2859
November	1st to 10th	Night	18% 11% 3 7% 5% 5% 5% 4 5% 7% 33%	2666
	11th to 20th	Night	18% 14% 3 9% 6% 5% 4 4 6% 7% 24%	2927
	21st to end	Night	21% 19% 6% 8% 4 4 4 3 5% 5% 20%	2940
December	1st to 10th	Night	15% 19% 5% 11% 6% 5% 5% 4 5% 7% 19%	4984
	11th to 20th	Night	16% 15% 5% 13% 6% 5% 6% 4 5% 6% 18%	5736
	21st to end	Night	28% 21% 7% 10% 4 3 3 2 4 4 14%	7667

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	49% 25% 6% 12% 6% 2	4233
	11th to 20th	Day	54% 25% 5% 8% 7% 1	4710
	21st to end	Day	50% 26% 4 11% 10%	5209
February	1st to 10th	Day	23% 60% 4 8% 4	1890
	11th to 20th	Day	25% 59% 4 6% 6%	1880
	21st to end	Day	22% 60% 4 8% 5%	1730
March	1st to 10th	Day	35% 32% 9% 6% 13% 4	4674
	11th to 20th	Day	41% 31% 9% 10% 8% 1	5090
	21st to end	Day	38% 33% 9% 10% 9% 2	5586
April	1st to 10th	Day	22% 60% 5% 7% 5% 1	2498
	11th to 20th	Day	20% 60% 4 8% 6% 1	2702
	21st to end	Day	20% 60% 5% 10% 5% 1	2730
May	1st to 10th	Day	30% 28% 8% 21% 12% 2	7651
	11th to 20th	Day	34% 25% 7% 17% 14% 2	7809
	21st to end	Day	33% 24% 7% 20% 13% 4	9690
June	1st to 10th	Day	16% 60% 4 11% 8% 2	3150
	11th to 20th	Day	18% 60% 4 11% 6% 1	3150
	21st to end	Day	18% 59% 5% 10% 7% 1	3150
July	1st to 10th	Day	32% 28% 11% 20% 8% 1	6747
	11th to 20th	Day	23% 28% 14% 29% 6%	6516
	21st to end	Day	22% 27% 10% 28% 12%	6712
August	1st to 10th	Day	20% 39% 8% 23% 9%	4221
	11th to 20th	Day	27% 39% 9% 17% 8%	4213
	21st to end	Day	24% 39% 11% 19% 7%	4674
September	1st to 10th	Day	19% 59% 7% 11% 5%	2356
	11th to 20th	Day	14% 58% 6% 16% 7%	2200
	21st to end	Day	18% 59% 7% 11% 4	2200
October	1st to 10th	Day	19% 37% 9% 19% 16%	3407
	11th to 20th	Day	27% 38% 9% 24% 3	3227
	21st to end	Day	38% 38% 7% 10% 7%	3180
November	1st to 10th	Day	27% 55% 5% 9% 4	1852
	11th to 20th	Day	28% 56% 6% 7% 4	1691
	21st to end	Day	31% 56% 6% 4 3	1680
December	1st to 10th	Day	41% 38% 11% 8% 3	2421
	11th to 20th	Day	46% 34% 5% 10% 4 1	2691
	21st to end	Day	57% 27% 4 5% 6%	3553
January	1st to 10th	Night	46% 24% 9% 13% 6% 2	8678
	11th to 20th	Night	54% 24% 6% 9% 7%	8280
	21st to end	Night	50% 26% 6% 10% 8% 1	9000
February	1st to 10th	Night	24% 60% 3 9% 4	2730
	11th to 20th	Night	23% 59% 4 9% 4	2633
	21st to end	Night	24% 60% 3 8% 5%	2076
March	1st to 10th	Night	34% 30% 10% 11% 12% 3	5399
	11th to 20th	Night	37% 31% 13% 13% 6% 1	5090
	21st to end	Night	39% 30% 7% 12% 11% 1	5588
April	1st to 10th	Night	23% 59% 4 7% 6%	2137
	11th to 20th	Night	20% 59% 3 9% 6% 2	1867
	21st to end	Night	21% 59% 4 9% 6% 1	1890
May	1st to 10th	Night	33% 26% 7% 20% 12% 2	5264
	11th to 20th	Night	32% 25% 7% 22% 12% 2	5042
	21st to end	Night	32% 24% 6% 21% 13% 4	4515
June	1st to 10th	Night	15% 60% 4 10% 10% 1	1470
	11th to 20th	Night	20% 59% 4 9% 6% 1	1470
	21st to end	Night	19% 58% 5% 10% 7% 1	1470
July	1st to 10th	Night	33% 28% 11% 17% 9% 1	3125
	11th to 20th	Night	22% 27% 11% 30% 9%	3338
	21st to end	Night	21% 27% 11% 27% 14%	3845
August	1st to 10th	Night	23% 38% 9% 20% 9%	2904
	11th to 20th	Night	25% 40% 10% 17% 7%	2902
	21st to end	Night	20% 37% 8% 23% 11%	3223
September	1st to 10th	Night	17% 59% 7% 11% 6%	2020
	11th to 20th	Night	11% 58% 8% 17% 6%	2200
	21st to end	Night	18% 59% 7% 10% 6%	2200
October	1st to 10th	Night	21% 37% 6% 24% 11%	3773
	11th to 20th	Night	21% 38% 13% 21% 6%	3899
	21st to end	Night	32% 38% 14% 11% 5%	4609
November	1st to 10th	Night	25% 54% 6% 10% 5%	2666
	11th to 20th	Night	25% 56% 6% 8% 4	2927
	21st to end	Night	31% 55% 4 5% 4 1	2940
December	1st to 10th	Night	42% 37% 9% 10% 3	4984
	11th to 20th	Night	44% 34% 5% 8% 7% 1	5735
	21st to end	Night	57% 27% 6% 6% 5%	7667

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	25% 14% 27% 24% 6% 3	245
	11th to 20th	Day	18% 12% 33% 25% 10% 2	330
	21st to end	Day	19% 14% 29% 26% 10% 1	363
February	1st to 10th	Day	20% 20% 33% 19% 7% 1	330
	11th to 20th	Day	18% 18% 36% 19% 8% 1	330
	21st to end	Day	22% 22% 31% 22% 3	273
March	1st to 10th	Day	20% 19% 35% 17% 6% 1	372
	11th to 20th	Day	19% 16% 30% 28% 6% 1	540
	21st to end	Day	25% 16% 28% 24% 7% 2	594
April	1st to 10th	Day	23% 14% 29% 24% 9% 1	540
	11th to 20th	Day	27% 15% 26% 19% 10% 3	532
	21st to end	Day	23% 13% 31% 21% 11% 2	540
May	1st to 10th	Day	20% 11% 31% 26% 10% 3	543
	11th to 20th	Day	18% 9% 29% 26% 14% 4	567
	21st to end	Day	17% 9% 31% 30% 11% 2	830
June	1st to 10th	Day	14% 9% 35% 29% 12% 2	780
	11th to 20th	Day	17% 10% 29% 31% 11% 2	780
	21st to end	Day	18% 7% 32% 30% 11% 3	780
July	1st to 10th	Day	10% 6% 31% 34% 16% 2	722
	11th to 20th	Day	11% 6% 32% 31% 14% 5%	718
	21st to end	Day	11% 5% 29% 35% 15% 5%	790
August	1st to 10th	Day	13% 5% 19% 33% 24% 6%	526
	11th to 20th	Day	12% 6% 18% 33% 21% 11%	519
	21st to end	Day	14% 8% 24% 28% 20% 6%	583
September	1st to 10th	Day	16% 10% 20% 29% 18% 6%	530
	11th to 20th	Day	14% 5% 21% 30% 22% 8%	530
	21st to end	Day	20% 11% 21% 29% 15% 4	530
October	1st to 10th	Day	22% 13% 22% 24% 16% 3	530
	11th to 20th	Day	23% 15% 31% 25% 5% 1	529
	21st to end	Day	25% 15% 33% 23% 4 1	363
November	1st to 10th	Day	28% 15% 28% 22% 6%	330
	11th to 20th	Day	25% 20% 28% 21% 4 1	225
	21st to end	Day	28% 18% 31% 16% 7%	220
December	1st to 10th	Day	24% 13% 32% 20% 9% 3	220
	11th to 20th	Day	27% 14% 38% 15% 5% 1	220
	21st to end	Day	34% 14% 32% 13% 6% 1	242
January	1st to 10th	Night	22% 8% 34% 27% 8%	1050
	11th to 20th	Night	23% 11% 30% 26% 10% 1	1050
	21st to end	Night	21% 7% 28% 33% 9% 1	1136
February	1st to 10th	Night	18% 11% 37% 26% 7%	840
	11th to 20th	Night	18% 11% 32% 30% 9%	823
	21st to end	Night	20% 11% 34% 29% 7% 1	692
March	1st to 10th	Night	18% 9% 34% 31% 8% 1	840
	11th to 20th	Night	20% 10% 33% 27% 9%	840
	21st to end	Night	19% 8% 31% 32% 9% 1	924
April	1st to 10th	Night	24% 9% 31% 29% 7%	704
	11th to 20th	Night	24% 8% 28% 27% 11% 2	623
	21st to end	Night	23% 7% 28% 29% 12% 1	630
May	1st to 10th	Night	16% 5% 28% 39% 10% 1	630
	11th to 20th	Night	17% 6% 26% 40% 11% 1	558
	21st to end	Night	16% 5% 26% 38% 14%	455
June	1st to 10th	Night	13% 5% 30% 40% 12%	420
	11th to 20th	Night	13% 6% 24% 43% 13% 1	420
	21st to end	Night	16% 4 21% 39% 20% 1	420
July	1st to 10th	Night	11% 3 19% 51% 16%	390
	11th to 20th	Night	9% 3 20% 45% 22% 2	478
	21st to end	Night	12% 1 21% 40% 23% 2	657
August	1st to 10th	Night	11% 2 21% 38% 27% 1	597
	11th to 20th	Night	12% 3 18% 36% 27% 4	594
	21st to end	Night	15% 3 20% 35% 24% 2	660
September	1st to 10th	Night	16% 7% 21% 31% 21% 5%	700
	11th to 20th	Night	12% 5% 21% 33% 24% 5%	800
	21st to end	Night	21% 5% 23% 32% 16% 3	800
October	1st to 10th	Night	23% 7% 25% 30% 14% 2	800
	11th to 20th	Night	27% 11% 25% 29% 8% 1	800
	21st to end	Night	28% 10% 31% 25% 6% 1	880
November	1st to 10th	Night	24% 12% 29% 26% 9%	820
	11th to 20th	Night	25% 13% 31% 23% 8%	840
	21st to end	Night	30% 12% 33% 20% 4	840
December	1st to 10th	Night	25% 15% 32% 21% 7%	1000
	11th to 20th	Night	25% 14% 36% 19% 5% 1	1050
	21st to end	Night	33% 11% 29% 20% 7%	1155

Page generated at 2026-06-28 02:10:48. Version ac07

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