Bella Coola
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bella Coola clear sky chart from 2005-11-06 to 2026-06-01.

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	21% 18% 4 9% 5% 4 4 3 4 5% 22%	135951
	Night	22% 20% 5% 10% 5% 4 4 3 4 5% 18%	135891
Transparency	Day	65% 3 11% 15% 5%	135647
	Night	70% 4 10% 12% 4 1	135773
Seeing	Day	33% 15% 27% 18% 6% 1	17970
	Night	36% 13% 26% 19% 6%	25714

By Month

Percentage Cloud Cover NW (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	20% 31% 6% 10% 5% 4 4 3 4 4 9%	4125
	11th to 20th	Day	18% 16% 3 7% 3 3 3 3 4 6% 33%	4119
	21st to end	Day	24% 20% 5% 9% 4 4 3 3 3 5% 20%	4745
February	1st to 10th	Day	20% 22% 5% 10% 5% 4 3 2 3 5% 20%	1731
	11th to 20th	Day	15% 28% 5% 8% 4 4 3 3 4 5% 22%	1845
	21st to end	Day	11% 28% 6% 11% 6% 4 4 2 4 4 20%	1557
March	1st to 10th	Day	12% 23% 7% 11% 6% 5% 5% 4 5% 4 18%	4708
	11th to 20th	Day	9% 25% 7% 13% 7% 6% 6% 4 5% 5% 14%	5110
	21st to end	Day	15% 22% 5% 10% 5% 5% 5% 3 5% 5% 20%	5607
April	1st to 10th	Day	16% 29% 6% 12% 7% 5% 3 2 3 4 13%	2617
	11th to 20th	Day	16% 23% 5% 9% 6% 4 5% 4 5% 5% 19%	2698
	21st to end	Day	19% 24% 5% 9% 5% 4 4 2 4 5% 19%	2730
May	1st to 10th	Day	14% 19% 5% 10% 6% 5% 6% 5% 6% 6% 20%	6544
	11th to 20th	Day	26% 20% 5% 10% 5% 5% 4 3 4 4 14%	6886
	21st to end	Day	26% 24% 5% 10% 5% 4 4 3 3 4 12%	7570
June	1st to 10th	Day	26% 17% 5% 11% 6% 5% 4 3 5% 4 16%	3001
	11th to 20th	Day	31% 17% 4 9% 6% 5% 5% 3 4 4 11%	3000
	21st to end	Day	30% 13% 3 9% 6% 5% 4 3 3 5% 18%	3000
July	1st to 10th	Day	19% 9% 3 6% 4 4 5% 4 5% 6% 35%	6780
	11th to 20th	Day	19% 7% 2 5% 3 2 2 2 5% 7% 45%	6780
	21st to end	Day	23% 9% 3 7% 5% 4 5% 3 5% 6% 31%	7375
August	1st to 10th	Day	12% 5% 1 4 3 3 3 3 5% 7% 54%	4674
	11th to 20th	Day	22% 11% 3 8% 4 3 4 3 4 6% 32%	4156
	21st to end	Day	27% 10% 3 7% 5% 4 5% 4 6% 6% 23%	4664
September	1st to 10th	Day	28% 10% 3 7% 4 3 4 2 4 6% 27%	2518
	11th to 20th	Day	25% 11% 4 8% 5% 5% 4 4 5% 6% 24%	2223
	21st to end	Day	34% 16% 3 8% 5% 4 4 3 3 4 15%	2200
October	1st to 10th	Day	38% 12% 3 8% 5% 4 4 3 3 4 15%	3320
	11th to 20th	Day	28% 17% 3 9% 5% 5% 5% 3 5% 7% 13%	3138
	21st to end	Day	19% 19% 3 8% 5% 7% 5% 4 6% 5% 19%	3119
November	1st to 10th	Day	32% 22% 4 9% 5% 3 3 2 3 3 13%	1648
	11th to 20th	Day	23% 28% 5% 10% 5% 5% 5% 3 3 3 11%	1643
	21st to end	Day	25% 25% 5% 8% 4 4 3 3 3 4 14%	1470
December	1st to 10th	Day	29% 19% 5% 9% 5% 4 3 3 4 5% 16%	2360
	11th to 20th	Day	24% 26% 5% 9% 4 4 4 3 4 4 12%	2715
	21st to end	Day	13% 28% 7% 13% 6% 6% 5% 3 4 4 9%	3575
January	1st to 10th	Night	21% 28% 7% 12% 6% 4 3 3 4 4 8%	8770
	11th to 20th	Night	20% 16% 3 8% 3 4 3 3 4 5% 30%	8779
	21st to end	Night	22% 19% 5% 10% 5% 5% 4 3 4 4 20%	9445
February	1st to 10th	Night	22% 22% 6% 10% 6% 4 4 3 4 4 15%	2888
	11th to 20th	Night	16% 24% 6% 9% 5% 4 4 2 5% 6% 20%	2662
	21st to end	Night	12% 28% 6% 11% 5% 4 4 3 6% 4 17%	2247
March	1st to 10th	Night	11% 26% 6% 11% 6% 5% 5% 3 5% 5% 17%	5391
	11th to 20th	Night	9% 25% 8% 15% 7% 6% 5% 4 4 4 12%	5109
	21st to end	Night	12% 21% 5% 12% 7% 5% 5% 3 6% 6% 17%	5610
April	1st to 10th	Night	16% 26% 7% 12% 7% 4 4 3 3 3 14%	2001
	11th to 20th	Night	17% 24% 5% 9% 6% 4 3 3 5% 5% 19%	1871
	21st to end	Night	20% 21% 5% 10% 6% 4 4 3 4 4 19%	1890
May	1st to 10th	Night	13% 20% 5% 11% 5% 6% 5% 4 6% 6% 18%	3620
	11th to 20th	Night	28% 21% 6% 9% 6% 4 3 3 4 4 11%	3229
	21st to end	Night	31% 21% 6% 9% 4 4 4 2 3 4 12%	3547
June	1st to 10th	Night	30% 19% 5% 8% 5% 3 3 4 4 3 17%	1400
	11th to 20th	Night	35% 18% 3 9% 5% 4 4 2 4 4 12%	1400
	21st to end	Night	31% 13% 3 7% 5% 4 3 3 4 5% 22%	1400
July	1st to 10th	Night	21% 13% 4 7% 3 3 3 3 4 5% 34%	3180
	11th to 20th	Night	22% 10% 3 6% 3 3 3 3 4 6% 38%	3180
	21st to end	Night	23% 14% 3 7% 3 3 3 3 4 7% 30%	3468
August	1st to 10th	Night	14% 10% 2 4 3 2 2 2 3 5% 53%	2465
	11th to 20th	Night	23% 18% 3 6% 4 4 4 2 4 5% 27%	2902
	21st to end	Night	31% 17% 3 8% 4 4 3 3 4 4 18%	3245
September	1st to 10th	Night	27% 12% 4 6% 4 4 4 2 3 4 29%	1881
	11th to 20th	Night	25% 14% 4 8% 4 3 4 3 5% 5% 26%	2175
	21st to end	Night	36% 15% 4 9% 5% 5% 3 2 3 5% 12%	2200
October	1st to 10th	Night	40% 15% 3 8% 4 3 3 3 3 3 15%	3879
	11th to 20th	Night	30% 19% 5% 11% 6% 5% 5% 3 4 3 9%	4013
	21st to end	Night	25% 20% 5% 10% 5% 5% 4 4 4 3 15%	4679
November	1st to 10th	Night	33% 22% 6% 10% 5% 4 3 3 3 4 8%	2870
	11th to 20th	Night	24% 30% 6% 9% 5% 4 3 3 3 4 10%	2972
	21st to end	Night	23% 25% 6% 9% 5% 5% 4 3 4 4 12%	3150
December	1st to 10th	Night	30% 19% 5% 9% 5% 4 3 3 4 6% 13%	5040
	11th to 20th	Night	25% 22% 5% 10% 5% 5% 5% 3 4 4 13%	5710
	21st to end	Night	16% 26% 6% 12% 6% 6% 5% 4 5% 5% 9%	7623

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% 3 6% 10% 1	4125
	11th to 20th	Day	55% 2 9% 20% 9% 5%	4140
	21st to end	Day	69% 2 10% 13% 6%	4746
February	1st to 10th	Day	70% 3 4 10% 10% 3	1731
	11th to 20th	Day	66% 3 7% 15% 9%	1854
	21st to end	Day	70% 3 7% 15% 4 2	1557
March	1st to 10th	Day	67% 4 8% 12% 9%	4708
	11th to 20th	Day	74% 4 3 12% 7%	5110
	21st to end	Day	67% 5% 10% 12% 5%	5607
April	1st to 10th	Day	77% 3 7% 10% 2	2617
	11th to 20th	Day	66% 5% 10% 13% 5%	2698
	21st to end	Day	69% 3 12% 13% 4	2730
May	1st to 10th	Day	63% 5% 15% 13% 4	6544
	11th to 20th	Day	73% 4 11% 11% 1	6889
	21st to end	Day	78% 3 7% 9% 3	7571
June	1st to 10th	Day	71% 4 10% 10% 5%	3001
	11th to 20th	Day	76% 4 9% 10% 2	3000
	21st to end	Day	68% 4 13% 12% 3	3000
July	1st to 10th	Day	50% 3 10% 23% 13% 1	6706
	11th to 20th	Day	41% 3 21% 30% 5%	6699
	21st to end	Day	55% 3 20% 18% 4	7168
August	1st to 10th	Day	33% 3 13% 39% 11%	4656
	11th to 20th	Day	55% 4 19% 17% 5%	4195
	21st to end	Day	62% 5% 16% 15% 2	4663
September	1st to 10th	Day	59% 3 17% 16% 4 1	2518
	11th to 20th	Day	61% 4 11% 17% 6% 1	2223
	21st to end	Day	73% 4 8% 11% 3	2200
October	1st to 10th	Day	76% 3 9% 8% 4	3320
	11th to 20th	Day	72% 3 12% 12% 2	3138
	21st to end	Day	69% 3 8% 13% 6%	3119
November	1st to 10th	Day	77% 3 6% 9% 4	1648
	11th to 20th	Day	79% 3 6% 7% 5%	1643
	21st to end	Day	76% 4 6% 9% 5% 1	1470
December	1st to 10th	Day	75% 4 9% 10% 2 1	2360
	11th to 20th	Day	78% 2 8% 8% 5%	2718
	21st to end	Day	79% 4 7% 7% 2 1	3575
January	1st to 10th	Night	81% 4 5% 9% 2	8770
	11th to 20th	Night	60% 1 9% 19% 7% 4	8820
	21st to end	Night	70% 2 9% 12% 6%	9445
February	1st to 10th	Night	74% 4 3 8% 9% 2	2888
	11th to 20th	Night	66% 5% 6% 13% 8% 1	2664
	21st to end	Night	70% 3 8% 14% 4 2	2247
March	1st to 10th	Night	68% 5% 8% 12% 7%	5391
	11th to 20th	Night	76% 4 5% 11% 4	5110
	21st to end	Night	67% 6% 12% 11% 5%	5610
April	1st to 10th	Night	74% 4 8% 10% 4	2001
	11th to 20th	Night	67% 4 10% 12% 6% 1	1871
	21st to end	Night	69% 4 10% 15% 2	1890
May	1st to 10th	Night	63% 8% 15% 11% 3	3617
	11th to 20th	Night	76% 3 11% 9% 1	3229
	21st to end	Night	77% 3 10% 8% 2	3547
June	1st to 10th	Night	71% 5% 9% 10% 4 1	1400
	11th to 20th	Night	75% 4 13% 7% 1	1400
	21st to end	Night	64% 4 16% 14% 2	1400
July	1st to 10th	Night	52% 3 11% 24% 8% 1	3145
	11th to 20th	Night	48% 4 27% 20% 1	3138
	21st to end	Night	54% 6% 26% 13% 2	3370
August	1st to 10th	Night	35% 3 17% 38% 7%	2458
	11th to 20th	Night	59% 6% 18% 12% 4	2929
	21st to end	Night	72% 4 14% 9% 1	3245
September	1st to 10th	Night	59% 4 18% 15% 3 1	1881
	11th to 20th	Night	60% 5% 12% 15% 8% 1	2175
	21st to end	Night	76% 5% 9% 9% 1	2200
October	1st to 10th	Night	77% 3 8% 9% 2	3879
	11th to 20th	Night	82% 2 7% 7% 2	4013
	21st to end	Night	76% 4 8% 9% 3	4679
November	1st to 10th	Night	82% 4 4 7% 2 1	2870
	11th to 20th	Night	81% 3 5% 6% 5%	2972
	21st to end	Night	78% 3 4 8% 5% 1	3150
December	1st to 10th	Night	77% 3 7% 9% 3	5040
	11th to 20th	Night	77% 3 8% 9% 3	5706
	21st to end	Night	80% 3 7% 7% 3	7623

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	36% 20% 29% 13% 1	220
	11th to 20th	Day	34% 18% 30% 16% 2	220
	21st to end	Day	39% 15% 26% 18% 3	316
February	1st to 10th	Day	36% 24% 28% 10% 3	430
	11th to 20th	Day	30% 23% 28% 14% 4	425
	21st to end	Day	34% 25% 25% 11% 5%	355
March	1st to 10th	Day	27% 22% 31% 17% 3 1	455
	11th to 20th	Day	29% 22% 28% 16% 4	540
	21st to end	Day	30% 19% 29% 17% 4 1	594
April	1st to 10th	Day	31% 22% 26% 16% 3 1	540
	11th to 20th	Day	29% 18% 27% 18% 7% 1	532
	21st to end	Day	31% 19% 26% 18% 6% 1	540
May	1st to 10th	Day	25% 16% 28% 23% 7% 1	585
	11th to 20th	Day	29% 13% 31% 18% 8% 1	775
	21st to end	Day	29% 17% 30% 20% 4	845
June	1st to 10th	Day	35% 17% 28% 17% 3	731
	11th to 20th	Day	36% 15% 28% 17% 4 1	730
	21st to end	Day	34% 11% 27% 22% 5% 2	730
July	1st to 10th	Day	29% 11% 28% 23% 8% 1	721
	11th to 20th	Day	30% 13% 29% 20% 7% 1	718
	21st to end	Day	30% 10% 26% 23% 8% 2	794
August	1st to 10th	Day	21% 10% 30% 29% 8% 2	706
	11th to 20th	Day	26% 12% 28% 24% 10% 1	517
	21st to end	Day	32% 12% 26% 19% 9% 2	583
September	1st to 10th	Day	34% 12% 25% 18% 11% 1	530
	11th to 20th	Day	32% 12% 27% 21% 8% 1	530
	21st to end	Day	43% 19% 21% 12% 4 1	530
October	1st to 10th	Day	39% 14% 23% 15% 8% 1	530
	11th to 20th	Day	44% 12% 22% 16% 5% 1	489
	21st to end	Day	43% 15% 22% 13% 6% 1	417
November	1st to 10th	Day	45% 19% 20% 12% 2 1	220
	11th to 20th	Day	38% 14% 29% 15% 4	220
	21st to end	Day	43% 14% 26% 11% 5% 1	220
December	1st to 10th	Day	34% 13% 28% 20% 4	220
	11th to 20th	Day	42% 17% 24% 14% 3	220
	21st to end	Day	40% 12% 30% 16% 2	242
January	1st to 10th	Night	40% 20% 29% 11% 1	950
	11th to 20th	Night	39% 17% 31% 12% 1	950
	21st to end	Night	37% 15% 30% 16% 3	1045
February	1st to 10th	Night	36% 18% 33% 12% 1	922
	11th to 20th	Night	31% 18% 32% 17% 2	824
	21st to end	Night	29% 20% 33% 14% 3	692
March	1st to 10th	Night	26% 20% 33% 17% 3	840
	11th to 20th	Night	31% 16% 31% 19% 3	840
	21st to end	Night	29% 15% 30% 20% 5%	924
April	1st to 10th	Night	31% 12% 33% 18% 7%	688
	11th to 20th	Night	28% 13% 31% 20% 8%	623
	21st to end	Night	29% 14% 28% 24% 5%	630
May	1st to 10th	Night	29% 9% 23% 28% 11%	429
	11th to 20th	Night	33% 6% 29% 24% 7%	414
	21st to end	Night	34% 11% 23% 28% 4	455
June	1st to 10th	Night	40% 8% 23% 24% 6%	400
	11th to 20th	Night	44% 10% 18% 21% 8%	400
	21st to end	Night	37% 5% 21% 31% 6%	400
July	1st to 10th	Night	29% 6% 21% 33% 12%	390
	11th to 20th	Night	32% 8% 15% 29% 15%	388
	21st to end	Night	29% 5% 18% 32% 15%	438
August	1st to 10th	Night	29% 3 15% 27% 25% 1	485
	11th to 20th	Night	30% 4 13% 34% 18%	594
	21st to end	Night	40% 7% 18% 23% 11% 1	660
September	1st to 10th	Night	32% 7% 20% 28% 13%	681
	11th to 20th	Night	32% 8% 18% 28% 14%	800
	21st to end	Night	44% 9% 24% 18% 6%	800
October	1st to 10th	Night	41% 10% 23% 19% 7%	800
	11th to 20th	Night	43% 10% 23% 19% 6%	800
	21st to end	Night	45% 13% 22% 16% 4	880
November	1st to 10th	Night	48% 14% 25% 11% 2	820
	11th to 20th	Night	44% 16% 26% 12% 2	857
	21st to end	Night	42% 18% 26% 12% 2	950
December	1st to 10th	Night	35% 16% 30% 17% 2	950
	11th to 20th	Night	40% 18% 26% 14% 1	950
	21st to end	Night	38% 22% 30% 9% 1	1045

Page generated at 2026-05-28 22:53:31. Version ac07

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