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 2024-11-04.

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 4 5% 6% 35%	105521
	Night	21% 12% 3 7% 5% 4 4 3 4 5% 31%	102086
Transparency	Day	49% 8% 15% 19% 8% 1	105261
	Night	57% 7% 14% 16% 6% 1	101992
Seeing	Day	25% 10% 19% 23% 17% 5%	15778
	Night	32% 9% 15% 25% 17% 3	23649

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% 21% 5% 9% 5% 4 4 2 3 3 14%	2219
	11th to 20th	Day	24% 16% 3 7% 5% 3 4 4 5% 6% 24%	2199
	21st to end	Day	46% 18% 3 6% 3 3 3 2 3 3 9%	2611
February	1st to 10th	Day	27% 15% 3 7% 5% 5% 4 5% 5% 5% 19%	1710
	11th to 20th	Day	21% 15% 3 9% 4 4 4 3 5% 5% 27%	1665
	21st to end	Day	19% 15% 4 8% 6% 5% 5% 4 6% 7% 22%	1413
March	1st to 10th	Day	15% 19% 3 9% 5% 5% 5% 5% 6% 7% 22%	3276
	11th to 20th	Day	17% 11% 3 9% 5% 5% 5% 4 6% 6% 29%	3490
	21st to end	Day	18% 12% 4 9% 6% 5% 6% 3 5% 6% 26%	3825
April	1st to 10th	Day	20% 14% 4 9% 6% 5% 4 5% 6% 7% 22%	2296
	11th to 20th	Day	19% 11% 3 8% 6% 5% 5% 4 7% 6% 28%	2438
	21st to end	Day	18% 13% 4 9% 5% 4 4 4 5% 7% 28%	2470
May	1st to 10th	Day	14% 7% 3 7% 5% 4 4 3 6% 5% 41%	4389
	11th to 20th	Day	9% 6% 3 7% 5% 5% 6% 5% 7% 9% 38%	4439
	21st to end	Day	24% 10% 3 8% 5% 5% 4 4 5% 6% 27%	5161
June	1st to 10th	Day	18% 9% 3 8% 6% 5% 5% 4 6% 8% 28%	2850
	11th to 20th	Day	13% 8% 3 9% 6% 5% 6% 5% 7% 8% 29%	2850
	21st to end	Day	14% 7% 3 7% 6% 5% 5% 4 5% 7% 37%	2850
July	1st to 10th	Day	7% 3 2 3 3 3 3 2 3 5% 66%	4740
	11th to 20th	Day	5% 3 1 3 3 2 2 3 4 5% 70%	4740
	21st to end	Day	11% 4 2 4 4 4 4 4 5% 8% 51%	5138
August	1st to 10th	Day	4 2 1 2 2 2 3 2 4 7% 70%	4234
	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 7% 5% 5% 4 4 5% 4 17%	1512
	11th to 20th	Day	27% 14% 3 6% 5% 4 5% 3 4 4 23%	1520
	21st to end	Day	27% 15% 4 7% 5% 4 4 4 4 5% 21%	1492
December	1st to 10th	Day	22% 16% 4 8% 6% 4 3 3 4 5% 26%	1330
	11th to 20th	Day	32% 18% 4 9% 5% 4 4 2 4 4 15%	1685
	21st to end	Day	32% 20% 5% 10% 5% 4 3 2 4 4 12%	2442
January	1st to 10th	Night	30% 18% 3 8% 5% 4 4 3 4 4 15%	4726
	11th to 20th	Night	26% 15% 4 9% 5% 4 3 3 4 5% 22%	4699
	21st to end	Night	44% 17% 3 6% 4 3 3 2 3 4 12%	5046
February	1st to 10th	Night	25% 16% 4 8% 5% 5% 5% 3 4 5% 21%	2470
	11th to 20th	Night	22% 12% 3 7% 4 4 3 3 6% 6% 31%	2402
	21st to end	Night	21% 16% 4 8% 4 5% 4 3 4 5% 26%	2041
March	1st to 10th	Night	19% 16% 3 8% 5% 5% 5% 4 5% 7% 24%	3591
	11th to 20th	Night	12% 10% 3 9% 6% 6% 6% 4 6% 6% 34%	3489
	21st to end	Night	22% 14% 4 8% 6% 5% 5% 3 4 4 26%	3828
April	1st to 10th	Night	18% 13% 4 8% 6% 5% 4 3 6% 6% 26%	1880
	11th to 20th	Night	18% 11% 3 6% 5% 5% 5% 3 6% 7% 30%	1691
	21st to end	Night	18% 12% 4 8% 5% 4 4 3 5% 7% 30%	1710
May	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 4 6% 46%	2572
	11th to 20th	Night	10% 6% 2 6% 4 4 4 5% 6% 9% 43%	2439
	21st to end	Night	20% 12% 4 8% 5% 4 4 4 5% 5% 28%	2414
June	1st to 10th	Night	16% 10% 4 7% 5% 4 4 4 5% 6% 34%	1330
	11th to 20th	Night	14% 8% 3 8% 8% 6% 5% 5% 6% 6% 30%	1330
	21st to end	Night	14% 7% 3 9% 5% 4 4 3 6% 7% 38%	1330
July	1st to 10th	Night	6% 4 2 5% 2 2 3 2 4 5% 64%	2220
	11th to 20th	Night	4 2 1 2 3 2 3 3 4 5% 71%	2220
	21st to end	Night	11% 4 1 4 3 3 4 4 4 6% 56%	2414
August	1st to 10th	Night	5% 2 1 3 2 2 2 2 3 6% 71%	2699
	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% 15% 3 7% 6% 5% 5% 3 5% 4 18%	2638
	11th to 20th	Night	24% 14% 4 7% 6% 5% 5% 4 5% 4 21%	2660
	21st to end	Night	26% 15% 4 8% 6% 4 5% 4 4 4 22%	2683
December	1st to 10th	Night	22% 17% 3 8% 6% 4 4 3 4 5% 24%	2850
	11th to 20th	Night	34% 18% 5% 7% 5% 3 4 3 4 4 14%	3520
	21st to end	Night	36% 18% 3 7% 5% 4 3 2 3 3 15%	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	75% 7% 6% 9% 3	2219
	11th to 20th	Day	60% 7% 15% 10% 7% 1	2220
	21st to end	Day	84% 5% 5% 4 1	2611
February	1st to 10th	Day	68% 9% 7% 9% 4 3	1710
	11th to 20th	Day	63% 6% 11% 14% 4 2	1674
	21st to end	Day	60% 8% 13% 11% 7% 2	1413
March	1st to 10th	Day	61% 8% 11% 13% 5%	3276
	11th to 20th	Day	56% 8% 11% 21% 3	3490
	21st to end	Day	58% 9% 17% 12% 4	3825
April	1st to 10th	Day	61% 8% 14% 11% 5%	2296
	11th to 20th	Day	54% 8% 12% 16% 8% 2	2438
	21st to end	Day	56% 8% 13% 14% 8% 1	2470
May	1st to 10th	Day	42% 7% 19% 23% 7% 1	4389
	11th to 20th	Day	38% 12% 21% 24% 4	4442
	21st to end	Day	56% 7% 17% 13% 7%	5162
June	1st to 10th	Day	51% 10% 17% 16% 5% 1	2850
	11th to 20th	Day	48% 10% 20% 16% 6%	2850
	21st to end	Day	44% 8% 19% 21% 7% 1	2850
July	1st to 10th	Day	22% 5% 13% 28% 25% 7%	4666
	11th to 20th	Day	17% 6% 20% 41% 16% 1	4659
	21st to end	Day	32% 8% 21% 26% 12% 1	4976
August	1st to 10th	Day	15% 5% 16% 46% 17% 1	4216
	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	71% 8% 9% 7% 5% 1	1512
	11th to 20th	Day	67% 9% 9% 10% 4 1	1520
	21st to end	Day	68% 8% 9% 10% 5% 1	1492
December	1st to 10th	Day	63% 7% 12% 11% 5% 1	1330
	11th to 20th	Day	77% 6% 7% 6% 4 1	1688
	21st to end	Day	78% 6% 6% 7% 3 1	2442
January	1st to 10th	Night	75% 8% 7% 7% 3 1	4726
	11th to 20th	Night	62% 8% 12% 8% 6% 3	4740
	21st to end	Night	81% 6% 5% 6% 2	5046
February	1st to 10th	Night	69% 6% 8% 9% 7% 1	2470
	11th to 20th	Night	57% 8% 12% 15% 6% 1	2404
	21st to end	Night	61% 6% 12% 14% 5% 2	2041
March	1st to 10th	Night	61% 8% 12% 14% 5%	3591
	11th to 20th	Night	53% 9% 12% 22% 3	3490
	21st to end	Night	64% 8% 12% 12% 5% 1	3828
April	1st to 10th	Night	59% 8% 14% 14% 4	1880
	11th to 20th	Night	55% 7% 12% 17% 8% 1	1691
	21st to end	Night	56% 7% 11% 18% 7%	1710
May	1st to 10th	Night	36% 9% 21% 26% 8%	2572
	11th to 20th	Night	38% 9% 28% 18% 6%	2439
	21st to end	Night	56% 8% 16% 14% 5%	2414
June	1st to 10th	Night	51% 8% 20% 15% 5% 1	1330
	11th to 20th	Night	50% 10% 18% 18% 4	1330
	21st to end	Night	46% 7% 20% 20% 7% 1	1330
July	1st to 10th	Night	25% 4 13% 35% 20% 3	2185
	11th to 20th	Night	18% 6% 24% 40% 12%	2178
	21st to end	Night	30% 7% 21% 32% 9% 1	2337
August	1st to 10th	Night	17% 5% 14% 50% 13% 1	2692
	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% 8% 8% 9% 4 1	2638
	11th to 20th	Night	68% 7% 10% 9% 4 1	2660
	21st to end	Night	68% 7% 7% 11% 5% 1	2683
December	1st to 10th	Night	65% 7% 11% 11% 5% 1	2850
	11th to 20th	Night	78% 5% 7% 7% 3 1	3516
	21st to end	Night	76% 7% 7% 7% 3 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	49% 6% 16% 19% 5% 5%	180
	11th to 20th	Day	47% 11% 12% 16% 13% 1	180
	21st to end	Day	48% 11% 10% 15% 13% 3	293
February	1st to 10th	Day	41% 15% 19% 14% 11% 1	370
	11th to 20th	Day	35% 13% 17% 23% 10% 3	365
	21st to end	Day	34% 11% 25% 19% 9% 2	307
March	1st to 10th	Day	31% 13% 18% 18% 15% 5%	424
	11th to 20th	Day	33% 15% 14% 18% 16% 4	460
	21st to end	Day	34% 15% 16% 18% 13% 4	506
April	1st to 10th	Day	31% 16% 24% 17% 8% 4	460
	11th to 20th	Day	29% 10% 23% 19% 13% 6%	452
	21st to end	Day	29% 16% 20% 20% 11% 4	460
May	1st to 10th	Day	19% 10% 25% 25% 16% 4	463
	11th to 20th	Day	19% 8% 23% 26% 19% 6%	523
	21st to end	Day	18% 11% 27% 24% 17% 4	735
June	1st to 10th	Day	22% 14% 24% 22% 15% 2	680
	11th to 20th	Day	16% 14% 26% 25% 16% 3	680
	21st to end	Day	18% 8% 21% 30% 18% 5%	680
July	1st to 10th	Day	14% 9% 23% 27% 21% 7%	671
	11th to 20th	Day	11% 9% 21% 30% 24% 5%	668
	21st to end	Day	9% 6% 18% 31% 29% 7%	739
August	1st to 10th	Day	9% 4 15% 28% 30% 14%	501
	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	41% 16% 17% 12% 12% 2	186
	11th to 20th	Day	39% 9% 13% 15% 13% 11%	180
	21st to end	Day	51% 9% 13% 12% 8% 7%	180
December	1st to 10th	Day	43% 6% 14% 14% 12% 10%	180
	11th to 20th	Day	41% 11% 16% 14% 12% 5%	180
	21st to end	Day	47% 10% 16% 17% 10% 2	198
January	1st to 10th	Night	46% 10% 14% 17% 9% 4	850
	11th to 20th	Night	44% 9% 9% 20% 16% 2	850
	21st to end	Night	43% 8% 10% 22% 13% 4	929
February	1st to 10th	Night	41% 9% 16% 21% 12% 1	760
	11th to 20th	Night	32% 9% 14% 27% 16% 1	744
	21st to end	Night	33% 13% 15% 24% 12% 3	628
March	1st to 10th	Night	33% 13% 16% 18% 16% 4	760
	11th to 20th	Night	30% 14% 14% 22% 18% 2	760
	21st to end	Night	33% 12% 17% 20% 15% 3	836
April	1st to 10th	Night	31% 11% 14% 26% 15% 3	724
	11th to 20th	Night	27% 12% 16% 30% 15% 1	563
	21st to end	Night	27% 12% 17% 25% 15% 3	570
May	1st to 10th	Night	20% 7% 21% 30% 18% 5%	399
	11th to 20th	Night	21% 6% 24% 27% 19% 4	374
	21st to end	Night	23% 10% 24% 26% 17% 1	411
June	1st to 10th	Night	23% 9% 24% 27% 15% 1	380
	11th to 20th	Night	18% 7% 26% 30% 18% 1	380
	21st to end	Night	19% 7% 23% 31% 18% 3	380
July	1st to 10th	Night	15% 7% 23% 27% 24% 4	370
	11th to 20th	Night	11% 7% 25% 35% 18% 3	368
	21st to end	Night	8% 5% 20% 43% 22% 3	416
August	1st to 10th	Night	9% 2 17% 39% 27% 6%	484
	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	44% 9% 11% 25% 10% 1	754
	11th to 20th	Night	40% 9% 14% 23% 12% 3	760
	21st to end	Night	42% 9% 13% 21% 12% 4	771
December	1st to 10th	Night	37% 9% 13% 21% 16% 4	850
	11th to 20th	Night	46% 9% 12% 18% 12% 3	850
	21st to end	Night	45% 11% 14% 21% 8%	935

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