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 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% 10% 3 8% 5% 4 4 4 5% 7% 36%	108174
	Night	15% 12% 4 9% 5% 4 4 4 5% 6% 31%	110629
Transparency	Day	27% 46% 7% 13% 7% 1	111692
	Night	30% 43% 7% 12% 6% 1	115262
Seeing	Day	19% 11% 28% 27% 12% 3	15729
	Night	21% 8% 28% 30% 12% 1	25241

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% 18% 6% 9% 4 4 5% 4 5% 6% 28%	3268
	11th to 20th	Day	10% 16% 5% 14% 7% 6% 6% 5% 5% 6% 20%	3589
	21st to end	Day	12% 22% 8% 12% 5% 5% 4 4 5% 5% 17%	4022
February	1st to 10th	Day	10% 14% 4 12% 7% 7% 5% 4 6% 7% 27%	1800
	11th to 20th	Day	11% 14% 4 9% 7% 6% 4 4 5% 6% 30%	1779
	21st to end	Day	11% 14% 5% 10% 7% 5% 4 4 5% 6% 29%	1610
March	1st to 10th	Day	15% 13% 3 6% 4 3 5% 4 5% 7% 36%	3181
	11th to 20th	Day	9% 12% 4 10% 6% 6% 5% 4 5% 7% 33%	3480
	21st to end	Day	14% 9% 5% 8% 5% 4 5% 4 6% 7% 33%	3815
April	1st to 10th	Day	17% 11% 3 7% 5% 5% 4 4 5% 7% 32%	2260
	11th to 20th	Day	19% 9% 3 6% 4 4 4 4 5% 7% 36%	2442
	21st to end	Day	19% 9% 2 7% 4 4 3 3 6% 7% 36%	2470
May	1st to 10th	Day	17% 6% 2 6% 4 4 4 3 5% 7% 41%	4108
	11th to 20th	Day	12% 8% 2 7% 4 4 5% 4 5% 7% 42%	4176
	21st to end	Day	15% 6% 2 5% 4 3 4 3 5% 7% 46%	5172
June	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 6% 8% 41%	2850
	11th to 20th	Day	12% 6% 3 6% 4 4 5% 5% 6% 9% 41%	2850
	21st to end	Day	15% 7% 2 5% 4 4 5% 4 6% 8% 40%	2850
July	1st to 10th	Day	15% 8% 2 6% 4 4 4 3 5% 8% 40%	4760
	11th to 20th	Day	9% 4 2 5% 4 4 4 4 6% 8% 50%	4607
	21st to end	Day	10% 5% 2 4 3 3 4 4 5% 7% 53%	4798
August	1st to 10th	Day	8% 5% 2 6% 4 5% 4 4 7% 8% 45%	4104
	11th to 20th	Day	13% 5% 2 6% 4 4 4 3 5% 8% 45%	4044
	21st to end	Day	12% 5% 2 6% 4 4 4 4 5% 7% 47%	4532
September	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 5% 7% 45%	2238
	11th to 20th	Day	13% 5% 3 6% 3 4 4 3 6% 9% 45%	2090
	21st to end	Day	18% 7% 3 7% 4 3 3 3 5% 8% 39%	2090
October	1st to 10th	Day	19% 6% 2 7% 5% 4 5% 3 5% 6% 38%	1990
	11th to 20th	Day	20% 10% 3 7% 5% 6% 5% 5% 5% 7% 26%	1899
	21st to end	Day	22% 11% 3 8% 5% 6% 4 4 6% 6% 24%	1881
November	1st to 10th	Day	20% 11% 3 8% 5% 4 4 4 5% 8% 27%	1762
	11th to 20th	Day	15% 16% 6% 11% 7% 4 5% 3 5% 6% 23%	1611
	21st to end	Day	21% 21% 5% 9% 6% 4 3 3 5% 5% 18%	1600
December	1st to 10th	Day	14% 20% 6% 10% 6% 5% 4 4 6% 6% 19%	2349
	11th to 20th	Day	17% 16% 6% 14% 6% 5% 5% 4 5% 7% 14%	2621
	21st to end	Day	29% 21% 6% 9% 4 4 2 2 2 5% 14%	3476
January	1st to 10th	Night	11% 14% 5% 11% 5% 4 4 4 6% 7% 27%	6697
	11th to 20th	Night	12% 17% 6% 14% 6% 5% 5% 4 5% 6% 20%	6316
	21st to end	Night	11% 17% 7% 14% 7% 7% 5% 3 5% 5% 19%	6952
February	1st to 10th	Night	11% 15% 4 11% 8% 6% 5% 4 5% 6% 26%	2600
	11th to 20th	Night	12% 15% 4 10% 7% 6% 4 4 5% 6% 26%	2503
	21st to end	Night	12% 16% 5% 10% 6% 4 6% 4 5% 6% 26%	1939
March	1st to 10th	Night	16% 10% 3 6% 3 3 4 3 5% 7% 41%	3659
	11th to 20th	Night	11% 12% 4 7% 4 5% 4 3 4 7% 38%	3479
	21st to end	Night	13% 10% 6% 6% 5% 4 4 4 5% 6% 38%	3817
April	1st to 10th	Night	20% 10% 3 7% 4 4 4 3 5% 7% 33%	1934
	11th to 20th	Night	20% 8% 2 5% 4 4 3 3 5% 7% 39%	1687
	21st to end	Night	20% 8% 3 7% 6% 4 3 3 5% 6% 35%	1710
May	1st to 10th	Night	17% 8% 3 9% 5% 4 4 3 5% 5% 36%	2833
	11th to 20th	Night	12% 9% 3 8% 5% 4 5% 3 6% 8% 37%	2703
	21st to end	Night	16% 7% 2 6% 4 4 4 4 5% 7% 42%	2411
June	1st to 10th	Night	13% 5% 3 6% 4 5% 5% 5% 6% 9% 41%	1330
	11th to 20th	Night	11% 7% 2 7% 6% 5% 5% 4 6% 7% 42%	1330
	21st to end	Night	13% 6% 2 7% 5% 5% 4 3 5% 7% 41%	1330
July	1st to 10th	Night	14% 7% 3 5% 4 4 5% 4 6% 8% 41%	2210
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 6% 52%	2360
	21st to end	Night	9% 5% 2 5% 3 4 4 4 6% 9% 50%	2763
August	1st to 10th	Night	7% 7% 2 7% 5% 4 5% 5% 7% 9% 43%	2825
	11th to 20th	Night	12% 5% 2 5% 3 4 5% 4 7% 9% 43%	2785
	21st to end	Night	10% 5% 2 6% 4 3 4 2 4 6% 53%	3124
September	1st to 10th	Night	13% 5% 2 6% 4 5% 4 4 5% 7% 45%	1919
	11th to 20th	Night	12% 4 1 5% 3 3 3 3 4 7% 53%	2090
	21st to end	Night	18% 7% 3 7% 4 4 3 3 5% 7% 39%	2090
October	1st to 10th	Night	18% 9% 3 7% 4 3 3 3 5% 6% 39%	2190
	11th to 20th	Night	23% 9% 3 7% 5% 5% 4 4 5% 6% 29%	2280
	21st to end	Night	26% 10% 3 8% 4 4 4 2 6% 6% 26%	2716
November	1st to 10th	Night	18% 11% 3 7% 4 5% 5% 4 5% 6% 33%	2536
	11th to 20th	Night	18% 15% 3 9% 6% 5% 4 4 6% 7% 23%	2787
	21st to end	Night	21% 19% 6% 8% 4 4 4 4 5% 5% 20%	2800
December	1st to 10th	Night	15% 19% 5% 10% 6% 5% 5% 4 5% 7% 19%	4836
	11th to 20th	Night	17% 15% 5% 13% 6% 5% 6% 4 5% 6% 18%	5586
	21st to end	Night	28% 21% 7% 10% 4 3 3 2 4 4 14%	7502

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	39% 31% 7% 14% 7% 3	3269
	11th to 20th	Day	48% 32% 6% 7% 7% 1	3620
	21st to end	Day	50% 32% 4 7% 7%	4022
February	1st to 10th	Day	22% 63% 4 7% 3	1800
	11th to 20th	Day	22% 62% 4 6% 6%	1788
	21st to end	Day	20% 64% 4 7% 5%	1610
March	1st to 10th	Day	29% 44% 10% 7% 9% 1	3184
	11th to 20th	Day	31% 43% 7% 13% 5% 1	3480
	21st to end	Day	30% 46% 7% 7% 8% 3	3815
April	1st to 10th	Day	19% 65% 5% 6% 5%	2260
	11th to 20th	Day	18% 66% 3 7% 5% 2	2442
	21st to end	Day	17% 65% 3 9% 5% 1	2470
May	1st to 10th	Day	24% 43% 7% 16% 9% 1	4120
	11th to 20th	Day	23% 43% 8% 15% 10% 1	4180
	21st to end	Day	23% 42% 8% 11% 13% 3	5172
June	1st to 10th	Day	14% 66% 3 10% 6% 1	2850
	11th to 20th	Day	15% 66% 3 8% 6% 1	2850
	21st to end	Day	16% 64% 4 9% 7% 1	2850
July	1st to 10th	Day	31% 38% 10% 13% 7% 1	4686
	11th to 20th	Day	20% 39% 11% 25% 5%	4526
	21st to end	Day	18% 36% 6% 25% 15%	4646
August	1st to 10th	Day	20% 40% 8% 23% 9%	4091
	11th to 20th	Day	27% 40% 9% 17% 8%	4083
	21st to end	Day	24% 39% 10% 19% 7%	4531
September	1st to 10th	Day	17% 61% 6% 11% 5%	2238
	11th to 20th	Day	13% 60% 6% 14% 6%	2090
	21st to end	Day	16% 62% 7% 10% 4	2090
October	1st to 10th	Day	19% 38% 9% 18% 16%	3302
	11th to 20th	Day	26% 39% 9% 23% 2	3127
	21st to end	Day	38% 39% 7% 9% 6%	3081
November	1st to 10th	Day	26% 57% 5% 8% 4	1762
	11th to 20th	Day	27% 58% 5% 6% 3	1611
	21st to end	Day	29% 58% 6% 4 3	1600
December	1st to 10th	Day	41% 39% 11% 7% 2	2349
	11th to 20th	Day	46% 34% 5% 10% 4 1	2621
	21st to end	Day	57% 28% 4 5% 6%	3476
January	1st to 10th	Night	38% 30% 10% 13% 6% 3	6697
	11th to 20th	Night	47% 31% 7% 9% 6%	6360
	21st to end	Night	50% 32% 5% 7% 6% 1	6952
February	1st to 10th	Night	22% 63% 3 8% 4	2600
	11th to 20th	Night	21% 62% 4 9% 4	2505
	21st to end	Night	21% 64% 3 5% 5%	1939
March	1st to 10th	Night	26% 43% 9% 13% 9% 1	3669
	11th to 20th	Night	25% 43% 9% 15% 6% 1	3480
	21st to end	Night	27% 43% 9% 11% 8% 1	3817
April	1st to 10th	Night	20% 65% 4 6% 5%	1934
	11th to 20th	Night	17% 65% 3 8% 5% 2	1687
	21st to end	Night	18% 65% 3 8% 5% 1	1710
May	1st to 10th	Night	29% 44% 6% 15% 6% 1	2840
	11th to 20th	Night	25% 43% 7% 16% 9% 1	2704
	21st to end	Night	26% 43% 8% 11% 8% 4	2412
June	1st to 10th	Night	13% 66% 3 9% 7% 1	1330
	11th to 20th	Night	17% 65% 3 7% 6% 1	1330
	21st to end	Night	16% 63% 4 9% 7% 1	1330
July	1st to 10th	Night	29% 38% 10% 13% 8% 2	2175
	11th to 20th	Night	19% 37% 10% 25% 9%	2318
	21st to end	Night	18% 37% 7% 21% 16%	2675
August	1st to 10th	Night	23% 39% 9% 20% 9%	2814
	11th to 20th	Night	25% 41% 10% 17% 7%	2812
	21st to end	Night	20% 38% 7% 23% 11%	3124
September	1st to 10th	Night	16% 62% 6% 10% 6%	1919
	11th to 20th	Night	11% 61% 7% 16% 5%	2090
	21st to end	Night	17% 62% 6% 10% 5%	2090
October	1st to 10th	Night	21% 38% 6% 24% 11%	3658
	11th to 20th	Night	20% 39% 13% 22% 6%	3779
	21st to end	Night	32% 39% 14% 10% 5%	4466
November	1st to 10th	Night	24% 57% 6% 8% 4	2536
	11th to 20th	Night	25% 59% 6% 7% 3	2787
	21st to end	Night	29% 58% 4 5% 3 1	2800
December	1st to 10th	Night	41% 38% 9% 9% 2	4836
	11th to 20th	Night	44% 35% 5% 8% 7% 1	5585
	21st to end	Night	56% 27% 5% 6% 5%	7502

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% 13% 27% 24% 7% 4	223
	11th to 20th	Day	19% 11% 32% 26% 11% 2	300
	21st to end	Day	21% 14% 29% 25% 10% 1	330
February	1st to 10th	Day	21% 20% 31% 20% 7% 1	300
	11th to 20th	Day	15% 19% 38% 20% 7% 1	300
	21st to end	Day	23% 23% 30% 21% 3	237
March	1st to 10th	Day	19% 18% 35% 19% 7% 2	308
	11th to 20th	Day	17% 14% 29% 32% 7% 1	460
	21st to end	Day	24% 13% 29% 25% 8% 2	506
April	1st to 10th	Day	22% 13% 29% 26% 9% 1	460
	11th to 20th	Day	27% 14% 26% 19% 11% 3	452
	21st to end	Day	23% 12% 30% 22% 11% 2	460
May	1st to 10th	Day	21% 10% 30% 26% 10% 3	463
	11th to 20th	Day	17% 7% 28% 29% 14% 5%	487
	21st to end	Day	16% 9% 29% 31% 12% 3	721
June	1st to 10th	Day	14% 8% 34% 29% 13% 2	680
	11th to 20th	Day	17% 9% 28% 32% 12% 2	680
	21st to end	Day	18% 7% 30% 30% 12% 3	680
July	1st to 10th	Day	10% 6% 30% 35% 17% 2	671
	11th to 20th	Day	12% 6% 30% 32% 15% 6%	668
	21st to end	Day	11% 5% 28% 35% 16% 6%	735
August	1st to 10th	Day	14% 5% 20% 32% 24% 6%	486
	11th to 20th	Day	12% 6% 16% 33% 21% 12%	479
	21st to end	Day	14% 8% 24% 28% 20% 6%	539
September	1st to 10th	Day	16% 9% 20% 30% 18% 6%	490
	11th to 20th	Day	15% 5% 22% 30% 21% 6%	490
	21st to end	Day	21% 11% 21% 28% 15% 4	490
October	1st to 10th	Day	24% 13% 22% 23% 16% 3	490
	11th to 20th	Day	23% 15% 30% 26% 6% 1	489
	21st to end	Day	28% 16% 32% 22% 3 1	330
November	1st to 10th	Day	28% 15% 28% 23% 6%	300
	11th to 20th	Day	27% 19% 28% 21% 4 1	205
	21st to end	Day	27% 17% 33% 16% 7% 1	200
December	1st to 10th	Day	25% 12% 32% 21% 8% 3	200
	11th to 20th	Day	26% 12% 41% 17% 5% 1	200
	21st to end	Day	35% 13% 31% 14% 7% 1	220
January	1st to 10th	Night	22% 8% 34% 28% 8% 1	1000
	11th to 20th	Night	23% 11% 29% 26% 10% 1	1000
	21st to end	Night	22% 7% 28% 32% 10% 1	1082
February	1st to 10th	Night	19% 11% 38% 26% 7%	800
	11th to 20th	Night	18% 10% 33% 30% 8%	783
	21st to end	Night	19% 11% 34% 29% 6% 1	647
March	1st to 10th	Night	17% 8% 33% 33% 8% 1	760
	11th to 20th	Night	19% 10% 33% 29% 9% 1	760
	21st to end	Night	18% 7% 31% 33% 10% 1	836
April	1st to 10th	Night	23% 9% 30% 30% 8%	637
	11th to 20th	Night	23% 8% 29% 28% 11% 1	563
	21st to end	Night	22% 7% 29% 29% 12% 1	570
May	1st to 10th	Night	17% 5% 28% 38% 11% 2	570
	11th to 20th	Night	17% 6% 25% 41% 12% 1	504
	21st to end	Night	16% 5% 26% 38% 16%	411
June	1st to 10th	Night	13% 5% 30% 40% 12%	380
	11th to 20th	Night	12% 6% 23% 43% 14% 1	380
	21st to end	Night	16% 4 21% 37% 21% 1	380
July	1st to 10th	Night	10% 3 18% 51% 17%	370
	11th to 20th	Night	8% 3 20% 44% 23% 2	453
	21st to end	Night	13% 1 21% 39% 23% 2	624
August	1st to 10th	Night	11% 2 22% 38% 27% 1	567
	11th to 20th	Night	12% 2 18% 35% 28% 4	564
	21st to end	Night	15% 4 20% 35% 24% 2	627
September	1st to 10th	Night	16% 6% 21% 32% 20% 5%	665
	11th to 20th	Night	13% 5% 22% 33% 23% 5%	760
	21st to end	Night	21% 5% 23% 32% 16% 3	760
October	1st to 10th	Night	24% 7% 25% 29% 13% 2	760
	11th to 20th	Night	27% 11% 24% 29% 9% 1	760
	21st to end	Night	29% 11% 31% 24% 6% 1	836
November	1st to 10th	Night	24% 11% 28% 27% 9%	780
	11th to 20th	Night	26% 13% 31% 23% 8%	800
	21st to end	Night	30% 12% 33% 21% 4 1	800
December	1st to 10th	Night	26% 14% 31% 21% 7%	952
	11th to 20th	Night	26% 14% 36% 18% 5% 1	1000
	21st to end	Night	33% 10% 29% 20% 8%	1100

Page generated at 2025-02-22 06:51:35. Version ac07

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