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 2024-02-05.

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	24% 18% 5% 8% 6% 3 4 4 4 5% 19%	77608
	Night	24% 21% 6% 9% 6% 3 4 4 4 4 16%	81211
Transparency	Day	68% 5% 10% 12% 5% 1	77309
	Night	72% 5% 8% 10% 4 1	81090
Seeing	Day	33% 16% 26% 19% 6% 1	14873
	Night	36% 13% 26% 19% 6%	22757

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	19% 29% 6% 8% 6% 3 4 5% 5% 4 12%	2219
	11th to 20th	Day	18% 21% 4 7% 6% 3 3 3 4 5% 26%	2199
	21st to end	Day	26% 25% 7% 9% 6% 3 4 3 3 4 10%	2547
February	1st to 10th	Day	22% 23% 6% 8% 6% 3 3 2 2 4 19%	1516
	11th to 20th	Day	16% 29% 6% 7% 5% 3 3 4 3 5% 18%	1575
	21st to end	Day	11% 24% 7% 11% 7% 3 4 3 3 5% 22%	1332
March	1st to 10th	Day	14% 20% 8% 11% 7% 4 5% 5% 4 4 18%	1840
	11th to 20th	Day	13% 28% 10% 11% 7% 4 5% 4 3 4 12%	1980
	21st to end	Day	17% 25% 7% 9% 7% 3 4 3 4 4 15%	2178
April	1st to 10th	Day	17% 29% 8% 11% 8% 4 4 3 3 4 11%	2242
	11th to 20th	Day	19% 21% 6% 8% 6% 3 5% 5% 5% 5% 17%	2308
	21st to end	Day	22% 24% 6% 7% 6% 3 4 3 3 4 16%	2340
May	1st to 10th	Day	20% 23% 6% 8% 5% 3 4 4 4 4 20%	2546
	11th to 20th	Day	21% 15% 5% 7% 6% 4 5% 4 5% 6% 21%	2656
	21st to end	Day	23% 17% 6% 7% 7% 4 6% 5% 4 4 17%	2917
June	1st to 10th	Day	27% 16% 5% 10% 7% 3 5% 4 5% 4 14%	2700
	11th to 20th	Day	34% 16% 5% 8% 7% 4 5% 4 4 4 11%	2700
	21st to end	Day	30% 11% 4 8% 6% 4 5% 4 3 5% 19%	2700
July	1st to 10th	Day	26% 10% 4 6% 6% 3 5% 5% 4 5% 26%	2700
	11th to 20th	Day	30% 10% 4 6% 5% 3 4 3 5% 6% 25%	2700
	21st to end	Day	27% 10% 3 6% 5% 3 4 5% 4 5% 29%	2938
August	1st to 10th	Day	19% 8% 3 6% 5% 3 4 5% 5% 7% 37%	2590
	11th to 20th	Day	20% 8% 3 6% 6% 3 4 5% 4 6% 36%	2298
	21st to end	Day	33% 12% 4 8% 6% 3 4 5% 3 5% 17%	2574
September	1st to 10th	Day	31% 10% 3 6% 6% 2 4 3 4 6% 24%	2267
	11th to 20th	Day	25% 10% 3 6% 7% 3 5% 5% 4 5% 26%	2001
	21st to end	Day	33% 16% 4 7% 6% 3 5% 4 3 4 16%	1980
October	1st to 10th	Day	29% 13% 3 6% 6% 3 4 4 4 5% 23%	1826
	11th to 20th	Day	30% 17% 4 9% 6% 3 5% 4 5% 4 13%	1735
	21st to end	Day	30% 18% 4 6% 6% 3 3 3 4 4 19%	1742
November	1st to 10th	Day	34% 20% 5% 9% 5% 3 3 3 3 3 13%	1488
	11th to 20th	Day	25% 28% 6% 8% 7% 3 5% 3 3 3 11%	1487
	21st to end	Day	26% 25% 5% 7% 5% 3 4 4 2 6% 13%	1330
December	1st to 10th	Day	20% 18% 5% 8% 6% 3 4 4 4 6% 21%	1330
	11th to 20th	Day	28% 25% 5% 6% 4 2 4 3 3 4 16%	1685
	21st to end	Day	15% 31% 9% 12% 7% 3 4 3 3 3 11%	2442
January	1st to 10th	Night	20% 27% 8% 11% 7% 3 4 3 4 5% 8%	4726
	11th to 20th	Night	22% 19% 4 8% 5% 4 4 3 3 4 23%	4699
	21st to end	Night	28% 25% 7% 10% 7% 3 4 3 3 3 6%	5111
February	1st to 10th	Night	25% 21% 7% 8% 7% 3 5% 3 4 3 14%	2537
	11th to 20th	Night	18% 25% 6% 8% 6% 3 4 3 4 6% 17%	2272
	21st to end	Night	12% 26% 8% 10% 6% 2 4 3 5% 4 20%	1923
March	1st to 10th	Night	13% 23% 8% 10% 8% 4 6% 4 4 5% 16%	2120
	11th to 20th	Night	13% 29% 9% 10% 7% 3 4 4 4 5% 11%	1979
	21st to end	Night	18% 25% 6% 9% 8% 4 5% 5% 4 4 12%	2178
April	1st to 10th	Night	16% 26% 8% 12% 8% 3 4 3 3 3 13%	1716
	11th to 20th	Night	19% 22% 5% 9% 8% 3 3 4 5% 5% 17%	1601
	21st to end	Night	23% 20% 6% 8% 6% 3 5% 3 4 4 18%	1620
May	1st to 10th	Night	20% 23% 5% 8% 4 4 3 4 4 6% 20%	1412
	11th to 20th	Night	24% 14% 6% 8% 8% 3 5% 5% 6% 6% 16%	1239
	21st to end	Night	25% 17% 5% 10% 5% 3 5% 4 4 6% 16%	1358
June	1st to 10th	Night	30% 18% 6% 7% 6% 2 3 5% 4 3 15%	1260
	11th to 20th	Night	37% 16% 4 7% 6% 3 4 3 4 5% 11%	1260
	21st to end	Night	29% 12% 4 7% 5% 3 4 4 4 5% 23%	1260
July	1st to 10th	Night	25% 10% 4 6% 5% 4 5% 3 4 5% 29%	1260
	11th to 20th	Night	29% 11% 3 6% 5% 3 4 5% 4 5% 25%	1260
	21st to end	Night	24% 14% 4 7% 4 2 2 4 4 7% 28%	1379
August	1st to 10th	Night	22% 10% 3 6% 5% 2 3 3 3 5% 37%	1347
	11th to 20th	Night	21% 10% 3 6% 6% 3 4 3 4 6% 36%	1602
	21st to end	Night	34% 16% 5% 8% 6% 3 3 3 3 4 16%	1782
September	1st to 10th	Night	29% 12% 4 6% 5% 3 3 3 3 4 27%	1692
	11th to 20th	Night	25% 13% 3 7% 5% 3 4 4 4 4 28%	1957
	21st to end	Night	34% 14% 5% 8% 6% 3 5% 3 3 5% 13%	1980
October	1st to 10th	Night	29% 15% 4 7% 5% 3 4 4 4 5% 23%	2133
	11th to 20th	Night	35% 16% 5% 8% 7% 3 4 3 3 4 12%	2222
	21st to end	Night	33% 18% 5% 7% 6% 3 3 4 3 3 16%	2614
November	1st to 10th	Night	35% 21% 6% 9% 6% 3 4 3 3 3 8%	2590
	11th to 20th	Night	25% 29% 6% 8% 5% 2 4 4 3 3 11%	2688
	21st to end	Night	24% 25% 6% 8% 6% 4 4 3 3 4 12%	2850
December	1st to 10th	Night	20% 20% 6% 9% 6% 3 4 4 4 6% 18%	2850
	11th to 20th	Night	30% 23% 5% 9% 6% 3 4 3 3 3 11%	3520
	21st to end	Night	20% 29% 7% 11% 7% 4 4 4 3 4 8%	5214

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	73% 6% 8% 11% 2	2219
	11th to 20th	Day	62% 3 8% 9% 9% 9%	2220
	21st to end	Day	80% 3 6% 5% 4 1	2547
February	1st to 10th	Day	71% 4 4 9% 9% 3	1516
	11th to 20th	Day	70% 4 7% 13% 6%	1584
	21st to end	Day	68% 3 7% 16% 4 2	1332
March	1st to 10th	Day	68% 5% 8% 12% 7% 1	1840
	11th to 20th	Day	79% 3 6% 9% 3 1	1980
	21st to end	Day	74% 4 8% 11% 2	2178
April	1st to 10th	Day	79% 4 6% 9% 2	2242
	11th to 20th	Day	69% 5% 9% 13% 4	2308
	21st to end	Day	74% 3 9% 11% 4	2340
May	1st to 10th	Day	68% 5% 11% 13% 3	2546
	11th to 20th	Day	64% 6% 13% 14% 4	2659
	21st to end	Day	69% 6% 9% 11% 4	2918
June	1st to 10th	Day	72% 5% 10% 8% 5%	2700
	11th to 20th	Day	77% 4 9% 8% 2	2700
	21st to end	Day	67% 5% 13% 12% 3	2700
July	1st to 10th	Day	59% 5% 13% 16% 6%	2626
	11th to 20th	Day	60% 5% 14% 16% 5%	2619
	21st to end	Day	54% 6% 17% 16% 7% 1	2775
August	1st to 10th	Day	46% 6% 19% 21% 7% 1	2572
	11th to 20th	Day	49% 6% 16% 20% 9%	2298
	21st to end	Day	69% 6% 12% 11% 2	2574
September	1st to 10th	Day	62% 4 16% 15% 3 1	2267
	11th to 20th	Day	61% 4 10% 18% 6% 1	2001
	21st to end	Day	72% 5% 8% 12% 3	1980
October	1st to 10th	Day	64% 5% 13% 12% 5%	1826
	11th to 20th	Day	73% 5% 8% 12% 2	1735
	21st to end	Day	71% 4 8% 11% 6%	1742
November	1st to 10th	Day	78% 3 5% 8% 4 1	1488
	11th to 20th	Day	80% 4 6% 5% 5%	1487
	21st to end	Day	76% 4 5% 8% 6% 1	1330
December	1st to 10th	Day	66% 6% 9% 14% 4 1	1330
	11th to 20th	Day	74% 2 8% 9% 6%	1688
	21st to end	Day	79% 5% 6% 7% 3 1	2442
January	1st to 10th	Night	78% 6% 6% 8% 2	4726
	11th to 20th	Night	67% 3 8% 8% 8% 7%	4740
	21st to end	Night	84% 3 3 5% 4	5111
February	1st to 10th	Night	76% 4 3 7% 8% 2	2537
	11th to 20th	Night	70% 6% 6% 11% 6% 1	2274
	21st to end	Night	68% 3 8% 15% 5% 2	1923
March	1st to 10th	Night	70% 5% 6% 11% 7%	2120
	11th to 20th	Night	76% 4 7% 8% 3 1	1980
	21st to end	Night	74% 5% 9% 9% 2	2178
April	1st to 10th	Night	75% 5% 6% 11% 3	1716
	11th to 20th	Night	69% 4 9% 13% 5%	1601
	21st to end	Night	71% 3 8% 16% 2	1620
May	1st to 10th	Night	66% 8% 10% 12% 4	1412
	11th to 20th	Night	67% 6% 12% 12% 3	1239
	21st to end	Night	67% 6% 12% 11% 3	1358
June	1st to 10th	Night	72% 5% 9% 9% 4 1	1260
	11th to 20th	Night	75% 4 12% 7% 1	1260
	21st to end	Night	63% 5% 17% 14% 2	1260
July	1st to 10th	Night	55% 7% 16% 18% 4	1225
	11th to 20th	Night	59% 6% 19% 14% 2	1218
	21st to end	Night	52% 8% 20% 16% 4	1302
August	1st to 10th	Night	48% 6% 21% 20% 5% 1	1340
	11th to 20th	Night	48% 8% 21% 16% 7%	1602
	21st to end	Night	72% 5% 10% 10% 2	1782
September	1st to 10th	Night	62% 4 16% 13% 3 2	1692
	11th to 20th	Night	58% 5% 11% 17% 8% 1	1957
	21st to end	Night	74% 5% 9% 10% 1	1980
October	1st to 10th	Night	65% 4 12% 15% 3	2133
	11th to 20th	Night	78% 3 8% 8% 3	2222
	21st to end	Night	74% 4 6% 11% 4	2614
November	1st to 10th	Night	83% 4 3 7% 2 1	2590
	11th to 20th	Night	80% 4 5% 6% 5%	2688
	21st to end	Night	80% 3 3 7% 6% 1	2850
December	1st to 10th	Night	68% 5% 8% 14% 5% 1	2850
	11th to 20th	Night	79% 4 4 7% 5% 1	3516
	21st to end	Night	81% 4 5% 6% 4 1	5214

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	33% 23% 28% 14% 2	180
	11th to 20th	Day	35% 19% 29% 14% 2	180
	21st to end	Day	38% 16% 25% 18% 3	264
February	1st to 10th	Day	40% 26% 22% 10% 2	353
	11th to 20th	Day	33% 24% 25% 15% 4	335
	21st to end	Day	31% 26% 24% 13% 5%	280
March	1st to 10th	Day	23% 24% 30% 18% 4 1	358
	11th to 20th	Day	28% 22% 29% 16% 4	420
	21st to end	Day	31% 20% 29% 18% 2 1	462
April	1st to 10th	Day	31% 25% 25% 15% 3 1	420
	11th to 20th	Day	29% 17% 27% 18% 7% 1	412
	21st to end	Day	36% 19% 23% 15% 6% 1	420
May	1st to 10th	Day	28% 17% 27% 24% 5%	459
	11th to 20th	Day	26% 12% 31% 20% 9% 1	625
	21st to end	Day	26% 15% 32% 22% 5%	680
June	1st to 10th	Day	35% 17% 27% 17% 3	630
	11th to 20th	Day	37% 16% 26% 16% 4	630
	21st to end	Day	32% 11% 27% 22% 6% 2	630
July	1st to 10th	Day	29% 10% 28% 24% 9% 1	621
	11th to 20th	Day	33% 14% 26% 20% 6% 1	618
	21st to end	Day	30% 10% 25% 25% 8% 2	684
August	1st to 10th	Day	21% 10% 31% 28% 7% 3	609
	11th to 20th	Day	23% 13% 28% 24% 10% 1	437
	21st to end	Day	35% 13% 27% 18% 6% 2	495
September	1st to 10th	Day	38% 13% 24% 15% 9% 1	450
	11th to 20th	Day	31% 12% 26% 22% 9% 1	450
	21st to end	Day	40% 19% 22% 14% 5% 1	450
October	1st to 10th	Day	37% 14% 23% 16% 9% 1	450
	11th to 20th	Day	41% 12% 22% 17% 6% 1	417
	21st to end	Day	43% 16% 21% 13% 6% 1	356
November	1st to 10th	Day	44% 21% 18% 12% 3 2	180
	11th to 20th	Day	41% 16% 24% 15% 4	180
	21st to end	Day	44% 14% 22% 12% 6% 1	180
December	1st to 10th	Day	29% 16% 28% 22% 4	180
	11th to 20th	Day	41% 17% 23% 16% 4	180
	21st to end	Day	40% 12% 29% 17% 2	198
January	1st to 10th	Night	37% 21% 29% 11% 1	850
	11th to 20th	Night	41% 17% 30% 11% 1	850
	21st to end	Night	38% 14% 29% 16% 3	935
February	1st to 10th	Night	39% 17% 32% 12% 1	802
	11th to 20th	Night	32% 17% 32% 17% 2	704
	21st to end	Night	27% 20% 35% 15% 3	592
March	1st to 10th	Night	25% 21% 33% 17% 3	720
	11th to 20th	Night	31% 16% 31% 18% 3	720
	21st to end	Night	31% 14% 30% 19% 6%	792
April	1st to 10th	Night	31% 12% 32% 18% 7%	590
	11th to 20th	Night	28% 14% 31% 18% 8%	533
	21st to end	Night	31% 14% 27% 22% 5%	540
May	1st to 10th	Night	31% 8% 23% 25% 12%	369
	11th to 20th	Night	31% 6% 30% 25% 7%	354
	21st to end	Night	33% 11% 23% 28% 5%	389
June	1st to 10th	Night	41% 8% 22% 24% 5%	360
	11th to 20th	Night	44% 10% 19% 20% 6%	360
	21st to end	Night	35% 6% 23% 29% 6%	360
July	1st to 10th	Night	28% 7% 21% 33% 12%	350
	11th to 20th	Night	34% 9% 15% 28% 14%	348
	21st to end	Night	29% 5% 17% 34% 14%	394
August	1st to 10th	Night	29% 4 16% 27% 25%	435
	11th to 20th	Night	27% 5% 14% 35% 19%	534
	21st to end	Night	41% 8% 20% 23% 9%	594
September	1st to 10th	Night	35% 7% 21% 27% 11%	612
	11th to 20th	Night	31% 8% 18% 28% 14%	720
	21st to end	Night	43% 9% 24% 18% 6%	720
October	1st to 10th	Night	39% 10% 23% 20% 8%	720
	11th to 20th	Night	44% 9% 22% 19% 6%	720
	21st to end	Night	45% 13% 22% 16% 4	792
November	1st to 10th	Night	49% 14% 24% 11% 2	740
	11th to 20th	Night	44% 16% 27% 12% 2	773
	21st to end	Night	42% 17% 27% 12% 2	850
December	1st to 10th	Night	32% 18% 31% 17% 2	850
	11th to 20th	Night	40% 17% 26% 14% 2	850
	21st to end	Night	38% 22% 30% 9% 1	935

Page generated at 2024-02-02 02:20:26. Version ac07

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