Campbell River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Campbell River clear sky chart from 2005-11-06 to 2025-08-05.

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	17% 10% 3 7% 5% 4 4 3 5% 6% 36%	129900
	Night	21% 12% 3 7% 5% 4 4 3 4 5% 31%	126862
Transparency	Day	50% 7% 16% 19% 7% 1	129595
	Night	57% 7% 14% 16% 5% 1	126744
Seeing	Day	25% 10% 20% 22% 17% 5%	16745
	Night	32% 9% 15% 25% 17% 3	24593

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	30% 22% 6% 9% 4 4 4 2 3 3 13%	3179
	11th to 20th	Day	17% 14% 3 9% 4 3 4 3 4 6% 31%	3159
	21st to end	Day	35% 17% 4 7% 3 3 3 2 2 3 22%	3751
February	1st to 10th	Day	26% 15% 3 7% 6% 5% 4 4 5% 5% 20%	1800
	11th to 20th	Day	22% 15% 3 9% 4 4 4 3 5% 5% 27%	1755
	21st to end	Day	20% 15% 4 7% 6% 5% 5% 4 6% 7% 21%	1485
March	1st to 10th	Day	17% 19% 4 9% 4 4 5% 4 5% 6% 23%	4717
	11th to 20th	Day	16% 13% 4 10% 5% 6% 6% 4 6% 5% 24%	5000
	21st to end	Day	22% 13% 4 10% 6% 6% 5% 3 5% 5% 20%	5486
April	1st to 10th	Day	20% 13% 4 9% 5% 5% 4 5% 6% 7% 22%	2417
	11th to 20th	Day	18% 11% 3 8% 6% 4 5% 4 7% 6% 29%	2568
	21st to end	Day	18% 13% 4 8% 5% 4 4 4 5% 7% 30%	2600
May	1st to 10th	Day	13% 7% 3 8% 6% 5% 5% 4 5% 5% 40%	6276
	11th to 20th	Day	12% 8% 3 8% 5% 5% 5% 4 7% 8% 34%	6367
	21st to end	Day	20% 10% 3 8% 6% 6% 5% 4 5% 6% 27%	7405
June	1st to 10th	Day	17% 9% 3 7% 5% 5% 5% 4 6% 8% 31%	3000
	11th to 20th	Day	12% 8% 3 10% 6% 6% 7% 5% 7% 8% 29%	3000
	21st to end	Day	14% 7% 3 7% 6% 5% 5% 4 5% 6% 37%	3000
July	1st to 10th	Day	8% 4 2 4 3 3 3 3 4 6% 60%	6780
	11th to 20th	Day	4 3 1 3 2 2 2 3 4 5% 73%	6780
	21st to end	Day	8% 3 1 4 3 3 4 3 5% 7% 59%	7375
August	1st to 10th	Day	4 2 1 2 2 2 3 2 4 7% 70%	4292
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 7% 8% 45%	4026
	21st to end	Day	13% 5% 2 5% 4 4 5% 3 5% 6% 48%	4521
September	1st to 10th	Day	9% 4 2 5% 4 3 5% 4 5% 7% 51%	2313
	11th to 20th	Day	18% 7% 3 6% 4 4 3 3 4 5% 43%	2165
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 5% 6% 36%	2076
October	1st to 10th	Day	22% 12% 3 8% 5% 4 5% 3 5% 5% 26%	3180
	11th to 20th	Day	24% 10% 3 7% 4 5% 5% 3 5% 5% 28%	3161
	21st to end	Day	23% 12% 4 10% 5% 5% 4 4 4 7% 22%	3095
November	1st to 10th	Day	32% 12% 3 8% 5% 6% 4 4 5% 4 17%	1568
	11th to 20th	Day	26% 14% 3 7% 5% 5% 5% 3 4 4 23%	1600
	21st to end	Day	27% 15% 4 7% 5% 4 4 4 4 5% 21%	1570
December	1st to 10th	Day	19% 21% 5% 9% 5% 4 3 3 4 5% 22%	2290
	11th to 20th	Day	35% 19% 4 9% 4 3 3 2 3 3 14%	2645
	21st to end	Day	33% 20% 5% 10% 5% 4 4 2 3 4 10%	3498
January	1st to 10th	Night	29% 20% 4 11% 5% 4 4 3 3 3 12%	6766
	11th to 20th	Night	20% 13% 4 8% 5% 4 3 3 5% 6% 30%	6739
	21st to end	Night	33% 15% 3 5% 3 3 3 2 3 4 26%	7198
February	1st to 10th	Night	24% 16% 4 8% 5% 5% 5% 3 4 5% 22%	2600
	11th to 20th	Night	22% 13% 3 7% 4 4 3 3 5% 6% 31%	2532
	21st to end	Night	21% 16% 4 8% 4 5% 5% 3 5% 5% 25%	2145
March	1st to 10th	Night	18% 16% 3 8% 6% 5% 5% 4 4 6% 26%	5166
	11th to 20th	Night	12% 11% 3 10% 7% 6% 6% 4 6% 6% 30%	4999
	21st to end	Night	29% 14% 4 8% 5% 5% 4 3 3 4 21%	5489
April	1st to 10th	Night	18% 13% 4 8% 6% 5% 4 3 6% 6% 27%	1979
	11th to 20th	Night	17% 11% 3 6% 5% 5% 5% 3 6% 7% 32%	1781
	21st to end	Night	18% 12% 4 7% 5% 4 3 3 5% 7% 33%	1800
May	1st to 10th	Night	12% 6% 3 6% 4 4 5% 4 5% 7% 45%	3686
	11th to 20th	Night	12% 7% 2 8% 5% 5% 5% 5% 6% 9% 39%	3511
	21st to end	Night	19% 12% 4 10% 5% 4 4 4 5% 6% 27%	3470
June	1st to 10th	Night	15% 10% 4 7% 5% 4 4 4 5% 6% 36%	1400
	11th to 20th	Night	14% 9% 3 8% 8% 6% 5% 6% 6% 6% 30%	1400
	21st to end	Night	14% 7% 3 9% 5% 4 5% 3 6% 7% 38%	1400
July	1st to 10th	Night	7% 4 2 5% 3 3 4 3 5% 6% 57%	3180
	11th to 20th	Night	3 1 1 2 2 2 2 3 4 5% 75%	3180
	21st to end	Night	8% 3 1 4 3 3 3 3 5% 7% 59%	3468
August	1st to 10th	Night	5% 2 1 3 2 2 2 2 3 6% 71%	2730
	11th to 20th	Night	10% 6% 2 7% 4 4 5% 4 6% 9% 44%	2812
	21st to end	Night	12% 7% 2 7% 4 4 3 3 4 6% 48%	3146
September	1st to 10th	Night	9% 5% 3 6% 5% 3 3 3 5% 6% 53%	1866
	11th to 20th	Night	18% 7% 3 6% 4 3 3 3 4 5% 44%	2013
	21st to end	Night	20% 9% 3 6% 3 3 4 3 5% 5% 39%	2104
October	1st to 10th	Night	22% 9% 3 9% 5% 5% 4 3 4 6% 30%	3800
	11th to 20th	Night	26% 11% 3 7% 5% 4 4 3 5% 6% 26%	3777
	21st to end	Night	23% 11% 3 8% 5% 5% 4 4 5% 6% 27%	4462
November	1st to 10th	Night	30% 16% 3 7% 5% 4 4 3 5% 4 18%	2730
	11th to 20th	Night	24% 14% 4 7% 5% 5% 5% 4 5% 4 21%	2800
	21st to end	Night	25% 15% 4 8% 6% 4 4 4 4 4 22%	2825
December	1st to 10th	Night	22% 19% 5% 10% 5% 4 4 3 5% 5% 18%	4890
	11th to 20th	Night	34% 21% 5% 8% 5% 3 3 2 4 4 11%	5560
	21st to end	Night	34% 19% 5% 8% 5% 4 3 2 3 3 13%	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	77% 6% 5% 10% 2	3179
	11th to 20th	Day	53% 7% 17% 16% 6% 1	3180
	21st to end	Day	72% 5% 12% 11% 1	3751
February	1st to 10th	Day	67% 8% 7% 9% 5% 3	1800
	11th to 20th	Day	62% 6% 11% 15% 4 2	1764
	21st to end	Day	61% 8% 12% 10% 7% 2	1485
March	1st to 10th	Day	63% 6% 11% 14% 5%	4717
	11th to 20th	Day	61% 7% 9% 19% 5%	5000
	21st to end	Day	67% 7% 13% 10% 3	5486
April	1st to 10th	Day	62% 8% 14% 12% 5%	2417
	11th to 20th	Day	53% 7% 13% 17% 8% 2	2568
	21st to end	Day	54% 8% 15% 15% 7% 1	2600
May	1st to 10th	Day	45% 7% 16% 22% 9%	6276
	11th to 20th	Day	45% 10% 19% 22% 3	6370
	21st to end	Day	57% 7% 17% 12% 6% 1	7406
June	1st to 10th	Day	49% 10% 17% 17% 6% 1	3000
	11th to 20th	Day	48% 10% 20% 17% 5%	3000
	21st to end	Day	45% 9% 20% 20% 6% 1	3000
July	1st to 10th	Day	25% 6% 20% 27% 18% 5%	6706
	11th to 20th	Day	16% 6% 21% 41% 15% 2	6699
	21st to end	Day	25% 7% 27% 32% 10% 1	7168
August	1st to 10th	Day	15% 5% 16% 46% 17% 1	4274
	11th to 20th	Day	36% 10% 28% 18% 8% 1	4065
	21st to end	Day	37% 7% 25% 25% 7%	4520
September	1st to 10th	Day	33% 9% 20% 25% 12% 2	2313
	11th to 20th	Day	44% 8% 14% 20% 12% 1	2165
	21st to end	Day	51% 8% 15% 18% 8%	2076
October	1st to 10th	Day	61% 7% 13% 13% 5%	3180
	11th to 20th	Day	58% 7% 12% 20% 3	3161
	21st to end	Day	65% 7% 9% 14% 5%	3095
November	1st to 10th	Day	72% 7% 8% 7% 5% 1	1568
	11th to 20th	Day	68% 8% 8% 10% 4 1	1600
	21st to end	Day	69% 7% 8% 10% 5% 1	1570
December	1st to 10th	Day	67% 7% 10% 12% 4 1	2290
	11th to 20th	Day	79% 6% 5% 6% 3	2648
	21st to end	Day	81% 6% 5% 6% 2	3498
January	1st to 10th	Night	78% 6% 7% 7% 2	6766
	11th to 20th	Night	55% 7% 14% 15% 6% 2	6780
	21st to end	Night	67% 5% 10% 15% 2	7198
February	1st to 10th	Night	68% 6% 8% 10% 7% 1	2600
	11th to 20th	Night	57% 8% 12% 15% 6% 1	2534
	21st to end	Night	63% 6% 11% 13% 5% 2	2145
March	1st to 10th	Night	61% 7% 11% 16% 5%	5166
	11th to 20th	Night	58% 8% 10% 20% 5%	5000
	21st to end	Night	70% 6% 9% 11% 4	5489
April	1st to 10th	Night	58% 8% 14% 15% 4	1979
	11th to 20th	Night	53% 7% 12% 19% 8% 1	1781
	21st to end	Night	54% 7% 14% 18% 7%	1800
May	1st to 10th	Night	38% 7% 19% 27% 9%	3683
	11th to 20th	Night	43% 8% 26% 16% 6%	3511
	21st to end	Night	59% 7% 16% 14% 3	3470
June	1st to 10th	Night	49% 8% 21% 15% 6% 1	1400
	11th to 20th	Night	50% 10% 18% 18% 4	1400
	21st to end	Night	47% 7% 20% 19% 6% 1	1400
July	1st to 10th	Night	30% 5% 20% 29% 14% 2	3145
	11th to 20th	Night	14% 6% 28% 39% 12%	3138
	21st to end	Night	25% 6% 31% 31% 7% 1	3370
August	1st to 10th	Night	17% 5% 14% 50% 13% 1	2723
	11th to 20th	Night	36% 10% 30% 16% 7% 1	2839
	21st to end	Night	36% 7% 26% 24% 6%	3146
September	1st to 10th	Night	32% 7% 20% 29% 11% 1	1866
	11th to 20th	Night	45% 7% 14% 20% 13% 2	2013
	21st to end	Night	49% 7% 18% 16% 9% 1	2104
October	1st to 10th	Night	58% 8% 15% 14% 5%	3800
	11th to 20th	Night	63% 5% 15% 16% 2	3777
	21st to end	Night	62% 7% 14% 13% 5%	4462
November	1st to 10th	Night	71% 7% 8% 9% 4 1	2730
	11th to 20th	Night	68% 7% 10% 9% 4 1	2800
	21st to end	Night	68% 7% 8% 11% 5% 1	2825
December	1st to 10th	Night	68% 7% 11% 10% 3	4890
	11th to 20th	Night	80% 5% 6% 6% 3	5556
	21st to end	Night	79% 6% 6% 6% 2	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	50% 6% 16% 19% 6% 5%	200
	11th to 20th	Day	44% 10% 13% 19% 14% 1	200
	21st to end	Day	46% 11% 9% 16% 13% 5%	320
February	1st to 10th	Day	38% 14% 20% 14% 12% 3	400
	11th to 20th	Day	35% 12% 16% 22% 12% 3	395
	21st to end	Day	35% 13% 24% 18% 8% 2	331
March	1st to 10th	Day	32% 12% 18% 18% 15% 4	460
	11th to 20th	Day	34% 14% 14% 18% 16% 4	500
	21st to end	Day	35% 15% 16% 18% 12% 3	550
April	1st to 10th	Day	32% 16% 23% 17% 9% 4	500
	11th to 20th	Day	27% 9% 25% 20% 13% 6%	492
	21st to end	Day	27% 15% 20% 21% 12% 5%	500
May	1st to 10th	Day	18% 11% 26% 25% 16% 4	503
	11th to 20th	Day	20% 8% 23% 25% 18% 6%	565
	21st to end	Day	18% 12% 27% 23% 16% 4	790
June	1st to 10th	Day	21% 15% 26% 22% 15% 2	730
	11th to 20th	Day	16% 13% 26% 26% 16% 3	730
	21st to end	Day	19% 8% 20% 30% 18% 5%	730
July	1st to 10th	Day	14% 9% 22% 27% 21% 7%	721
	11th to 20th	Day	10% 9% 23% 30% 23% 5%	718
	21st to end	Day	9% 5% 18% 31% 29% 8%	794
August	1st to 10th	Day	8% 4 15% 28% 30% 14%	519
	11th to 20th	Day	8% 4 17% 35% 28% 7%	477
	21st to end	Day	14% 9% 19% 31% 21% 6%	539
September	1st to 10th	Day	16% 8% 20% 29% 20% 9%	490
	11th to 20th	Day	28% 8% 15% 19% 20% 9%	490
	21st to end	Day	29% 11% 17% 20% 18% 4	490
October	1st to 10th	Day	32% 9% 16% 17% 18% 8%	490
	11th to 20th	Day	38% 8% 17% 16% 16% 6%	490
	21st to end	Day	39% 10% 17% 16% 11% 6%	411
November	1st to 10th	Day	42% 17% 18% 12% 11% 2	200
	11th to 20th	Day	39% 9% 13% 17% 13% 11%	200
	21st to end	Day	51% 10% 12% 11% 10% 7%	200
December	1st to 10th	Day	41% 7% 14% 15% 14% 10%	200
	11th to 20th	Day	44% 10% 16% 15% 12% 5%	200
	21st to end	Day	49% 9% 15% 17% 9% 1	220
January	1st to 10th	Night	46% 10% 13% 18% 9% 4	900
	11th to 20th	Night	42% 10% 9% 21% 16% 2	900
	21st to end	Night	41% 8% 10% 22% 14% 5%	983
February	1st to 10th	Night	40% 9% 16% 23% 12% 1	800
	11th to 20th	Night	32% 9% 13% 27% 17% 1	784
	21st to end	Night	35% 12% 15% 23% 12% 3	660
March	1st to 10th	Night	34% 13% 16% 18% 16% 4	800
	11th to 20th	Night	31% 13% 13% 23% 18% 2	800
	21st to end	Night	34% 11% 17% 20% 14% 3	880
April	1st to 10th	Night	30% 11% 14% 26% 15% 3	762
	11th to 20th	Night	25% 12% 16% 31% 15% 1	593
	21st to end	Night	26% 12% 18% 25% 16% 3	600
May	1st to 10th	Night	20% 7% 20% 31% 17% 5%	420
	11th to 20th	Night	22% 7% 24% 26% 18% 4	394
	21st to end	Night	24% 9% 23% 27% 17% 1	433
June	1st to 10th	Night	22% 11% 25% 27% 15% 1	400
	11th to 20th	Night	18% 7% 25% 31% 18% 1	400
	21st to end	Night	19% 7% 23% 30% 18% 3	400
July	1st to 10th	Night	15% 7% 24% 28% 23% 3	390
	11th to 20th	Night	10% 7% 27% 34% 18% 3	388
	21st to end	Night	8% 5% 19% 43% 22% 4	438
August	1st to 10th	Night	9% 2 16% 40% 26% 6%	492
	11th to 20th	Night	12% 4 16% 35% 30% 3	564
	21st to end	Night	16% 6% 20% 31% 25% 3	627
September	1st to 10th	Night	15% 6% 15% 33% 28% 4	726
	11th to 20th	Night	23% 7% 11% 23% 26% 11%	760
	21st to end	Night	30% 7% 14% 24% 20% 5%	760
October	1st to 10th	Night	28% 6% 13% 27% 22% 4	760
	11th to 20th	Night	36% 6% 11% 24% 18% 5%	760
	21st to end	Night	41% 9% 13% 20% 13% 3	836
November	1st to 10th	Night	45% 10% 11% 24% 10% 1	780
	11th to 20th	Night	41% 9% 14% 23% 11% 3	800
	21st to end	Night	42% 8% 13% 21% 12% 4	813
December	1st to 10th	Night	36% 9% 12% 21% 17% 4	900
	11th to 20th	Night	46% 9% 12% 19% 12% 3	900
	21st to end	Night	46% 11% 14% 21% 8% 1	990

Page generated at 2025-08-01 22:32:25. Version ac07

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