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 2025-02-06.

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	22% 19% 4 9% 5% 4 4 3 4 5% 21%	111899
	Night	23% 21% 5% 10% 5% 4 4 3 4 4 17%	114988
Transparency	Day	66% 4 11% 14% 5% 1	111639
	Night	71% 4 9% 11% 4 1	114894
Seeing	Day	33% 16% 26% 19% 6% 1	16198
	Night	36% 13% 26% 19% 6%	24053

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% 29% 5% 9% 5% 4 4 3 5% 4 11%	3179
	11th to 20th	Day	18% 19% 4 8% 4 4 4 3 4 5% 27%	3159
	21st to end	Day	25% 23% 5% 8% 4 3 3 2 3 4 21%	3659
February	1st to 10th	Day	21% 23% 6% 10% 5% 3 3 2 2 5% 19%	1606
	11th to 20th	Day	15% 29% 5% 8% 4 4 3 3 3 5% 20%	1665
	21st to end	Day	10% 27% 6% 12% 6% 4 4 2 3 4 21%	1413
March	1st to 10th	Day	10% 24% 7% 12% 6% 6% 5% 4 5% 4 18%	3208
	11th to 20th	Day	12% 29% 7% 12% 6% 4 4 3 3 4 16%	3490
	21st to end	Day	11% 23% 5% 9% 5% 5% 4 3 4 5% 25%	3825
April	1st to 10th	Day	16% 31% 7% 12% 6% 5% 3 2 3 4 11%	2368
	11th to 20th	Day	16% 24% 5% 9% 6% 4 5% 4 4 5% 18%	2438
	21st to end	Day	21% 27% 5% 9% 6% 4 4 2 4 4 15%	2470
May	1st to 10th	Day	15% 21% 5% 9% 5% 5% 5% 4 5% 5% 21%	4474
	11th to 20th	Day	27% 19% 5% 9% 5% 4 3 3 4 4 16%	4696
	21st to end	Day	24% 26% 6% 9% 5% 4 3 3 3 3 13%	5161
June	1st to 10th	Day	27% 17% 5% 11% 6% 5% 4 3 5% 4 14%	2850
	11th to 20th	Day	32% 17% 4 9% 6% 5% 4 3 4 4 11%	2850
	21st to end	Day	30% 13% 3 9% 6% 5% 4 3 3 5% 18%	2850
July	1st to 10th	Day	15% 8% 3 5% 4 4 4 4 4 5% 43%	4740
	11th to 20th	Day	17% 7% 2 5% 3 3 3 3 5% 7% 45%	4740
	21st to end	Day	33% 11% 3 7% 5% 4 4 3 4 5% 20%	5138
August	1st to 10th	Day	11% 5% 1 4 3 3 3 3 5% 7% 55%	4530
	11th to 20th	Day	21% 11% 3 8% 4 3 4 3 4 6% 32%	4026
	21st to end	Day	28% 10% 3 8% 5% 5% 5% 4 6% 7% 21%	4521
September	1st to 10th	Day	30% 11% 3 7% 4 4 4 2 4 6% 25%	2392
	11th to 20th	Day	24% 11% 4 8% 6% 5% 4 4 5% 5% 25%	2112
	21st to end	Day	34% 16% 3 8% 5% 4 4 4 3 4 15%	2090
October	1st to 10th	Day	39% 13% 3 8% 6% 4 4 3 3 4 14%	3219
	11th to 20th	Day	28% 17% 3 9% 5% 5% 5% 3 5% 7% 12%	3042
	21st to end	Day	19% 18% 3 8% 5% 6% 5% 4 6% 5% 19%	3022
November	1st to 10th	Day	33% 22% 4 10% 5% 3 3 2 2 3 13%	1568
	11th to 20th	Day	24% 28% 5% 10% 6% 4 4 2 3 3 11%	1565
	21st to end	Day	25% 26% 5% 8% 4 4 3 3 4 5% 14%	1400
December	1st to 10th	Day	28% 19% 5% 10% 5% 4 3 3 4 5% 16%	2290
	11th to 20th	Day	24% 26% 5% 9% 4 4 4 3 4 4 12%	2645
	21st to end	Day	13% 28% 7% 13% 6% 6% 5% 3 4 4 9%	3498
January	1st to 10th	Night	22% 24% 6% 12% 6% 5% 4 3 4 5% 10%	6766
	11th to 20th	Night	21% 19% 4 9% 4 4 4 3 5% 5% 24%	6739
	21st to end	Night	25% 22% 6% 11% 4 4 3 2 3 3 17%	7303
February	1st to 10th	Night	23% 22% 6% 9% 6% 4 4 3 4 4 15%	2684
	11th to 20th	Night	16% 26% 6% 9% 5% 4 4 2 4 5% 19%	2402
	21st to end	Night	12% 28% 6% 10% 5% 3 3 2 6% 4 19%	2039
March	1st to 10th	Night	9% 26% 6% 11% 6% 6% 5% 4 6% 6% 16%	3659
	11th to 20th	Night	12% 27% 8% 13% 7% 4 4 3 3 4 14%	3489
	21st to end	Night	11% 21% 5% 10% 6% 4 5% 4 6% 6% 22%	3828
April	1st to 10th	Night	16% 27% 7% 13% 7% 4 4 3 3 3 13%	1810
	11th to 20th	Night	18% 23% 5% 10% 7% 4 3 3 4 5% 18%	1691
	21st to end	Night	22% 22% 5% 10% 6% 4 4 3 4 3 17%	1710
May	1st to 10th	Night	12% 21% 5% 11% 5% 5% 5% 4 6% 6% 20%	2470
	11th to 20th	Night	27% 20% 6% 8% 5% 4 3 4 4 5% 14%	2199
	21st to end	Night	28% 22% 6% 9% 4 3 4 2 4 4 14%	2414
June	1st to 10th	Night	30% 19% 5% 8% 5% 3 3 4 4 3 15%	1330
	11th to 20th	Night	36% 18% 3 9% 5% 4 4 2 3 4 11%	1330
	21st to end	Night	30% 13% 4 7% 5% 4 3 3 4 5% 22%	1330
July	1st to 10th	Night	17% 10% 2 6% 3 4 3 3 4 5% 44%	2220
	11th to 20th	Night	17% 9% 3 6% 4 3 4 3 5% 7% 40%	2220
	21st to end	Night	32% 18% 3 7% 4 2 3 2 4 5% 20%	2414
August	1st to 10th	Night	13% 9% 2 4 3 2 2 2 3 5% 54%	2389
	11th to 20th	Night	23% 17% 3 6% 4 4 4 2 4 5% 28%	2812
	21st to end	Night	32% 18% 3 8% 4 4 4 3 4 4 16%	3146
September	1st to 10th	Night	28% 12% 4 7% 4 4 4 2 3 4 28%	1787
	11th to 20th	Night	25% 14% 4 8% 4 3 4 3 5% 4 27%	2066
	21st to end	Night	35% 14% 4 9% 5% 5% 3 2 3 5% 13%	2090
October	1st to 10th	Night	41% 15% 4 8% 4 3 3 3 3 3 14%	3760
	11th to 20th	Night	30% 19% 5% 11% 6% 5% 5% 3 4 3 9%	3889
	21st to end	Night	25% 20% 5% 10% 5% 5% 4 3 4 3 15%	4534
November	1st to 10th	Night	34% 22% 6% 10% 4 3 3 3 3 3 8%	2730
	11th to 20th	Night	23% 31% 5% 9% 4 4 3 3 3 4 10%	2830
	21st to end	Night	23% 26% 6% 9% 5% 5% 4 3 4 4 12%	3000
December	1st to 10th	Night	30% 18% 5% 9% 4 4 3 3 4 6% 14%	4890
	11th to 20th	Night	25% 22% 5% 10% 5% 4 5% 3 4 4 14%	5560
	21st to end	Night	16% 26% 6% 12% 6% 6% 5% 4 5% 5% 9%	7458

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	76% 4 7% 12% 1	3179
	11th to 20th	Day	62% 2 8% 15% 6% 6%	3180
	21st to end	Day	70% 2 12% 11% 4 1	3659
February	1st to 10th	Day	71% 4 4 9% 10% 3	1606
	11th to 20th	Day	68% 4 7% 14% 7%	1674
	21st to end	Day	68% 3 7% 15% 4 2	1413
March	1st to 10th	Day	67% 6% 8% 10% 10%	3208
	11th to 20th	Day	73% 4 4 13% 4	3490
	21st to end	Day	61% 6% 12% 12% 8% 1	3825
April	1st to 10th	Day	79% 4 6% 9% 2	2368
	11th to 20th	Day	67% 5% 9% 13% 5% 1	2438
	21st to end	Day	74% 3 9% 11% 4	2470
May	1st to 10th	Day	61% 8% 14% 13% 4	4474
	11th to 20th	Day	70% 6% 11% 11% 2	4699
	21st to end	Day	76% 5% 6% 9% 4	5162
June	1st to 10th	Day	73% 5% 9% 9% 4	2850
	11th to 20th	Day	76% 4 9% 9% 2	2850
	21st to end	Day	68% 4 13% 12% 3	2850
July	1st to 10th	Day	43% 3 10% 25% 17% 2	4666
	11th to 20th	Day	40% 3 23% 28% 5%	4659
	21st to end	Day	65% 3 12% 14% 5%	4976
August	1st to 10th	Day	32% 4 13% 40% 11%	4512
	11th to 20th	Day	55% 4 20% 17% 5%	4065
	21st to end	Day	63% 5% 16% 14% 2	4520
September	1st to 10th	Day	61% 4 16% 15% 4 1	2392
	11th to 20th	Day	62% 4 10% 18% 6% 1	2112
	21st to end	Day	72% 5% 8% 12% 3	2090
October	1st to 10th	Day	77% 3 9% 8% 3	3219
	11th to 20th	Day	72% 3 12% 11% 1	3042
	21st to end	Day	69% 3 8% 14% 7%	3022
November	1st to 10th	Day	78% 3 5% 8% 5% 1	1568
	11th to 20th	Day	79% 4 6% 7% 5%	1565
	21st to end	Day	76% 4 5% 9% 5% 1	1400
December	1st to 10th	Day	74% 4 9% 10% 2 1	2290
	11th to 20th	Day	77% 2 8% 8% 5%	2648
	21st to end	Day	79% 4 7% 7% 2 1	3498
January	1st to 10th	Night	77% 4 6% 11% 1	6766
	11th to 20th	Night	65% 2 11% 12% 5% 5%	6780
	21st to end	Night	75% 2 9% 9% 4	7303
February	1st to 10th	Night	74% 4 3 7% 9% 2	2684
	11th to 20th	Night	68% 6% 6% 12% 7% 1	2404
	21st to end	Night	68% 3 8% 14% 5% 2	2039
March	1st to 10th	Night	64% 7% 8% 12% 9%	3659
	11th to 20th	Night	74% 5% 6% 12% 3	3490
	21st to end	Night	60% 9% 13% 12% 6%	3828
April	1st to 10th	Night	75% 5% 6% 10% 4	1810
	11th to 20th	Night	68% 5% 9% 12% 6% 1	1691
	21st to end	Night	71% 4 8% 15% 2	1710
May	1st to 10th	Night	59% 12% 13% 13% 3	2470
	11th to 20th	Night	71% 5% 12% 11% 2	2199
	21st to end	Night	74% 4 8% 10% 3	2414
June	1st to 10th	Night	72% 5% 9% 9% 4 1	1330
	11th to 20th	Night	75% 4 12% 7% 1	1330
	21st to end	Night	64% 4 16% 14% 2	1330
July	1st to 10th	Night	40% 4 13% 30% 11% 1	2185
	11th to 20th	Night	43% 5% 32% 18% 2	2178
	21st to end	Night	64% 5% 14% 15% 2	2337
August	1st to 10th	Night	34% 4 16% 39% 7%	2382
	11th to 20th	Night	58% 6% 18% 13% 4	2839
	21st to end	Night	73% 4 14% 8% 1	3146
September	1st to 10th	Night	60% 4 17% 14% 3 1	1787
	11th to 20th	Night	60% 5% 11% 16% 8% 1	2066
	21st to end	Night	75% 5% 9% 10% 1	2090
October	1st to 10th	Night	78% 3 8% 9% 2	3760
	11th to 20th	Night	83% 2 7% 7% 2	3889
	21st to end	Night	75% 4 8% 9% 3	4534
November	1st to 10th	Night	83% 4 3 7% 2 1	2730
	11th to 20th	Night	80% 3 5% 6% 5%	2830
	21st to end	Night	79% 3 4 8% 5% 1	3000
December	1st to 10th	Night	77% 3 7% 10% 3	4890
	11th to 20th	Night	77% 3 8% 9% 3	5556
	21st to end	Night	80% 3 7% 7% 3	7458

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	35% 22% 29% 14% 2	200
	11th to 20th	Day	35% 19% 30% 15% 2	200
	21st to end	Day	39% 15% 25% 18% 3	290
February	1st to 10th	Day	37% 25% 26% 9% 2	386
	11th to 20th	Day	32% 25% 25% 14% 5%	365
	21st to end	Day	32% 26% 23% 12% 6%	307
March	1st to 10th	Day	23% 24% 29% 19% 4 1	391
	11th to 20th	Day	28% 22% 29% 16% 4	460
	21st to end	Day	29% 20% 28% 18% 4 1	506
April	1st to 10th	Day	33% 24% 26% 15% 3 1	460
	11th to 20th	Day	28% 18% 28% 19% 6% 1	452
	21st to end	Day	34% 20% 23% 16% 6% 1	460
May	1st to 10th	Day	26% 17% 28% 24% 5%	501
	11th to 20th	Day	27% 13% 31% 19% 9% 1	675
	21st to end	Day	28% 17% 30% 20% 4	735
June	1st to 10th	Day	35% 17% 28% 16% 3	680
	11th to 20th	Day	37% 15% 25% 18% 4 1	680
	21st to end	Day	33% 11% 26% 22% 5% 2	680
July	1st to 10th	Day	28% 11% 27% 24% 8% 1	671
	11th to 20th	Day	30% 13% 27% 21% 7% 1	668
	21st to end	Day	32% 10% 24% 24% 8% 2	739
August	1st to 10th	Day	20% 10% 30% 30% 9% 3	657
	11th to 20th	Day	24% 12% 28% 25% 10% 1	477
	21st to end	Day	34% 13% 28% 18% 6% 1	539
September	1st to 10th	Day	36% 12% 25% 16% 9% 1	490
	11th to 20th	Day	31% 12% 26% 21% 8% 1	490
	21st to end	Day	42% 19% 21% 13% 4 1	490
October	1st to 10th	Day	40% 13% 22% 15% 9% 1	490
	11th to 20th	Day	42% 12% 23% 16% 5% 1	453
	21st to end	Day	42% 16% 22% 13% 6% 2	386
November	1st to 10th	Day	46% 20% 19% 12% 3 2	200
	11th to 20th	Day	40% 15% 26% 16% 4	200
	21st to end	Day	44% 14% 24% 12% 6% 1	200
December	1st to 10th	Day	31% 14% 30% 22% 5%	200
	11th to 20th	Day	42% 17% 24% 14% 4	200
	21st to end	Day	41% 11% 29% 17% 2	220
January	1st to 10th	Night	38% 21% 30% 10% 1	900
	11th to 20th	Night	40% 17% 30% 11% 1	900
	21st to end	Night	37% 15% 29% 16% 3	990
February	1st to 10th	Night	37% 17% 33% 12% 1	853
	11th to 20th	Night	31% 18% 32% 17% 2	744
	21st to end	Night	27% 21% 34% 15% 3	628
March	1st to 10th	Night	25% 21% 33% 17% 4	760
	11th to 20th	Night	31% 16% 31% 19% 3	760
	21st to end	Night	30% 14% 30% 20% 6%	836
April	1st to 10th	Night	31% 12% 32% 18% 7%	622
	11th to 20th	Night	28% 14% 31% 20% 8%	563
	21st to end	Night	31% 14% 27% 23% 5%	570
May	1st to 10th	Night	30% 9% 23% 26% 12% 1	389
	11th to 20th	Night	32% 6% 30% 25% 7%	374
	21st to end	Night	33% 11% 23% 28% 5%	411
June	1st to 10th	Night	41% 8% 23% 23% 5%	380
	11th to 20th	Night	45% 10% 19% 20% 7%	380
	21st to end	Night	36% 6% 22% 30% 6%	380
July	1st to 10th	Night	27% 6% 21% 33% 12%	370
	11th to 20th	Night	32% 8% 15% 28% 16%	368
	21st to end	Night	31% 5% 17% 33% 14%	416
August	1st to 10th	Night	28% 3 15% 28% 25% 1	460
	11th to 20th	Night	29% 5% 13% 35% 18%	564
	21st to end	Night	42% 7% 19% 23% 8%	627
September	1st to 10th	Night	33% 6% 20% 28% 12%	647
	11th to 20th	Night	32% 8% 18% 28% 14%	760
	21st to end	Night	43% 9% 24% 18% 6%	760
October	1st to 10th	Night	41% 10% 23% 20% 7%	760
	11th to 20th	Night	44% 10% 23% 18% 6%	760
	21st to end	Night	45% 13% 22% 16% 4	836
November	1st to 10th	Night	49% 14% 24% 11% 2	780
	11th to 20th	Night	44% 15% 26% 12% 2	815
	21st to end	Night	42% 17% 27% 12% 2	900
December	1st to 10th	Night	33% 17% 32% 17% 2	900
	11th to 20th	Night	40% 17% 27% 14% 1	900
	21st to end	Night	38% 22% 29% 10% 1	990

Page generated at 2025-02-03 00:05:56. Version ac07

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