Powell River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Powell River clear sky chart from 2005-11-06 to 2026-02-16.

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	19% 9% 3 7% 5% 4 4 3 5% 6% 34%	134551
	Night	24% 10% 3 8% 5% 4 4 3 4 5% 28%	134989
Transparency	Day	51% 8% 15% 18% 7% 1	134249
	Night	57% 7% 13% 16% 6% 1	134869
Seeing	Day	25% 11% 23% 24% 14% 3	17199
	Night	31% 8% 18% 24% 16% 3	25356

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	36% 16% 4 8% 5% 4 5% 3 5% 5% 9%	4125
	11th to 20th	Day	21% 9% 3 6% 5% 5% 6% 4 5% 9% 27%	4119
	21st to end	Day	36% 13% 4 10% 5% 4 7% 3 3 4 12%	4943
February	1st to 10th	Day	31% 13% 3 8% 5% 6% 5% 4 4 4 17%	1890
	11th to 20th	Day	26% 13% 3 7% 5% 4 5% 3 5% 5% 24%	1801
	21st to end	Day	26% 12% 3 8% 6% 5% 5% 4 5% 6% 21%	1485
March	1st to 10th	Day	24% 13% 5% 10% 6% 5% 5% 4 5% 5% 19%	4721
	11th to 20th	Day	19% 13% 4 9% 6% 5% 5% 4 5% 6% 24%	5000
	21st to end	Day	22% 12% 4 11% 7% 6% 5% 4 4 6% 19%	5518
April	1st to 10th	Day	23% 12% 3 9% 5% 5% 5% 3 5% 7% 23%	2400
	11th to 20th	Day	20% 9% 3 7% 5% 4 5% 4 5% 6% 31%	2563
	21st to end	Day	22% 9% 3 7% 4 4 4 4 5% 6% 33%	2607
May	1st to 10th	Day	13% 8% 3 7% 5% 4 5% 3 4 6% 42%	6320
	11th to 20th	Day	14% 9% 3 7% 4 5% 4 4 7% 10% 33%	6277
	21st to end	Day	21% 10% 3 8% 5% 5% 5% 4 5% 6% 30%	7376
June	1st to 10th	Day	19% 8% 2 7% 4 4 4 4 6% 7% 34%	3000
	11th to 20th	Day	14% 7% 3 8% 6% 6% 5% 4 7% 8% 33%	3000
	21st to end	Day	14% 7% 3 6% 5% 4 4 4 6% 7% 40%	3000
July	1st to 10th	Day	9% 3 1 3 3 3 3 2 5% 6% 61%	6780
	11th to 20th	Day	4 3 1 3 2 2 2 2 3 5% 73%	6780
	21st to end	Day	6% 4 1 4 3 3 3 3 5% 7% 61%	7291
August	1st to 10th	Day	5% 2 1 3 2 2 3 3 4 6% 70%	4398
	11th to 20th	Day	11% 6% 3 6% 4 5% 5% 4 6% 9% 42%	4156
	21st to end	Day	14% 5% 2 5% 4 4 4 4 5% 7% 46%	4664
September	1st to 10th	Day	10% 4 2 4 4 3 4 4 5% 9% 50%	2405
	11th to 20th	Day	18% 7% 2 7% 4 4 4 3 6% 6% 39%	2316
	21st to end	Day	23% 7% 3 6% 5% 5% 4 4 5% 6% 32%	2160
October	1st to 10th	Day	24% 8% 3 9% 6% 6% 5% 4 5% 6% 24%	3280
	11th to 20th	Day	30% 9% 3 7% 5% 4 4 3 5% 6% 23%	3261
	21st to end	Day	26% 13% 3 9% 6% 5% 4 4 4 6% 18%	3218
November	1st to 10th	Day	35% 12% 4 9% 4 4 4 4 3 4 17%	1648
	11th to 20th	Day	32% 14% 4 8% 5% 4 4 4 4 4 17%	1680
	21st to end	Day	34% 12% 4 9% 6% 5% 4 3 4 4 15%	1680
December	1st to 10th	Day	24% 12% 4 10% 6% 7% 6% 4 5% 6% 15%	2399
	11th to 20th	Day	42% 14% 4 10% 4 4 4 2 3 3 10%	2715
	21st to end	Day	34% 15% 5% 10% 6% 5% 3 3 4 4 11%	3575
January	1st to 10th	Night	35% 14% 4 10% 5% 4 5% 3 4 4 11%	8770
	11th to 20th	Night	24% 8% 3 6% 4 4 5% 4 5% 7% 31%	8779
	21st to end	Night	33% 11% 3 8% 4 5% 6% 3 4 4 18%	9244
February	1st to 10th	Night	31% 15% 4 8% 5% 4 4 3 3 5% 21%	2730
	11th to 20th	Night	25% 13% 3 8% 4 3 4 3 4 5% 28%	2597
	21st to end	Night	28% 13% 4 7% 5% 4 3 3 4 6% 23%	2145
March	1st to 10th	Night	26% 12% 4 8% 6% 5% 5% 3 4 5% 22%	5167
	11th to 20th	Night	19% 12% 4 9% 6% 5% 5% 5% 5% 5% 26%	4999
	21st to end	Night	28% 12% 5% 9% 6% 5% 4 3 4 4 19%	5457
April	1st to 10th	Night	24% 12% 3 9% 5% 5% 5% 4 5% 7% 23%	2000
	11th to 20th	Night	20% 11% 3 6% 5% 5% 5% 4 6% 7% 29%	1783
	21st to end	Night	22% 8% 3 6% 5% 5% 5% 3 6% 5% 31%	1791
May	1st to 10th	Night	15% 8% 3 7% 4 3 4 3 5% 6% 43%	3640
	11th to 20th	Night	16% 8% 3 7% 5% 4 5% 4 6% 8% 34%	3616
	21st to end	Night	21% 12% 4 10% 5% 4 4 4 5% 5% 25%	3483
June	1st to 10th	Night	18% 10% 3 9% 5% 5% 5% 4 6% 5% 32%	1400
	11th to 20th	Night	17% 9% 3 8% 5% 6% 5% 4 6% 6% 32%	1400
	21st to end	Night	17% 7% 3 5% 4 4 4 4 5% 8% 40%	1400
July	1st to 10th	Night	8% 5% 2 5% 3 4 4 4 5% 6% 55%	3180
	11th to 20th	Night	3 2 1 2 2 2 2 2 4 6% 72%	3180
	21st to end	Night	7% 5% 2 5% 4 3 4 3 5% 7% 55%	3550
August	1st to 10th	Night	5% 3 1 2 2 2 2 2 4 6% 70%	2740
	11th to 20th	Night	8% 6% 3 7% 4 5% 6% 3 6% 7% 44%	2902
	21st to end	Night	14% 7% 3 6% 4 4 4 3 4 5% 47%	3245
September	1st to 10th	Night	8% 5% 2 5% 4 3 4 3 5% 7% 55%	1994
	11th to 20th	Night	17% 8% 2 6% 5% 3 4 4 5% 5% 42%	2080
	21st to end	Night	23% 7% 3 6% 4 3 3 3 5% 6% 38%	2240
October	1st to 10th	Night	26% 9% 3 8% 5% 5% 4 3 5% 5% 27%	3920
	11th to 20th	Night	31% 8% 3 7% 3 4 4 3 5% 6% 26%	3897
	21st to end	Night	26% 10% 4 9% 5% 5% 4 4 5% 6% 23%	4581
November	1st to 10th	Night	35% 10% 4 8% 5% 5% 4 3 4 5% 16%	2870
	11th to 20th	Night	32% 11% 4 9% 6% 5% 3 4 4 4 19%	2940
	21st to end	Night	32% 11% 4 10% 5% 3 4 3 4 5% 19%	2940
December	1st to 10th	Night	26% 12% 4 9% 6% 7% 6% 3 5% 5% 18%	4996
	11th to 20th	Night	42% 15% 4 8% 5% 3 3 3 3 3 11%	5710
	21st to end	Night	33% 14% 4 10% 5% 5% 4 3 3 4 14%	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	75% 6% 8% 9% 1	4125
	11th to 20th	Day	49% 10% 12% 20% 9%	4140
	21st to end	Day	70% 5% 8% 16% 1	4944
February	1st to 10th	Day	69% 8% 8% 8% 4 3	1890
	11th to 20th	Day	62% 7% 12% 13% 4 2	1810
	21st to end	Day	65% 7% 12% 9% 5% 2	1485
March	1st to 10th	Day	65% 8% 11% 11% 4	4721
	11th to 20th	Day	61% 7% 11% 17% 4	5000
	21st to end	Day	67% 9% 13% 9% 2	5518
April	1st to 10th	Day	63% 9% 14% 11% 4	2400
	11th to 20th	Day	56% 8% 12% 14% 8% 1	2563
	21st to end	Day	55% 9% 15% 14% 7%	2607
May	1st to 10th	Day	43% 7% 16% 23% 10%	6320
	11th to 20th	Day	46% 11% 19% 20% 3	6280
	21st to end	Day	56% 9% 17% 13% 5%	7377
June	1st to 10th	Day	51% 10% 17% 15% 6% 2	3000
	11th to 20th	Day	50% 11% 19% 16% 4 1	3000
	21st to end	Day	46% 8% 20% 19% 6% 1	3000
July	1st to 10th	Day	26% 6% 20% 26% 17% 6%	6706
	11th to 20th	Day	16% 6% 20% 38% 18% 2	6699
	21st to end	Day	24% 7% 27% 29% 12% 2	7085
August	1st to 10th	Day	18% 6% 15% 46% 14% 1	4381
	11th to 20th	Day	40% 10% 24% 17% 8% 2	4195
	21st to end	Day	37% 9% 23% 23% 8% 1	4663
September	1st to 10th	Day	34% 9% 19% 25% 12% 2	2405
	11th to 20th	Day	45% 9% 16% 17% 12% 1	2316
	21st to end	Day	52% 9% 16% 16% 8%	2160
October	1st to 10th	Day	58% 10% 15% 13% 5%	3280
	11th to 20th	Day	62% 8% 12% 14% 4	3261
	21st to end	Day	67% 8% 11% 10% 3	3218
November	1st to 10th	Day	72% 7% 9% 7% 5%	1648
	11th to 20th	Day	71% 8% 8% 8% 4 1	1680
	21st to end	Day	72% 7% 9% 8% 4 1	1680
December	1st to 10th	Day	63% 8% 12% 13% 3 1	2399
	11th to 20th	Day	80% 6% 7% 5% 2 1	2718
	21st to end	Day	78% 7% 8% 5% 2 1	3575
January	1st to 10th	Night	76% 6% 6% 9% 2	8770
	11th to 20th	Night	48% 9% 13% 19% 11% 1	8820
	21st to end	Night	65% 4 9% 19% 2	9244
February	1st to 10th	Night	68% 6% 8% 10% 6% 2	2730
	11th to 20th	Night	60% 7% 13% 12% 6% 2	2599
	21st to end	Night	64% 6% 10% 13% 5% 1	2145
March	1st to 10th	Night	62% 8% 11% 14% 5%	5167
	11th to 20th	Night	58% 8% 11% 20% 3	5000
	21st to end	Night	68% 8% 10% 10% 3	5457
April	1st to 10th	Night	61% 9% 14% 13% 3	2000
	11th to 20th	Night	55% 9% 11% 16% 8% 2	1783
	21st to end	Night	55% 8% 14% 17% 6%	1791
May	1st to 10th	Night	41% 7% 15% 27% 10%	3637
	11th to 20th	Night	47% 9% 22% 19% 4	3616
	21st to end	Night	60% 8% 14% 15% 2	3483
June	1st to 10th	Night	52% 9% 18% 13% 7% 2	1400
	11th to 20th	Night	51% 10% 18% 16% 5%	1400
	21st to end	Night	42% 10% 19% 20% 6% 2	1400
July	1st to 10th	Night	29% 6% 21% 25% 15% 5%	3145
	11th to 20th	Night	15% 5% 24% 37% 18% 1	3138
	21st to end	Night	28% 5% 28% 25% 12% 1	3451
August	1st to 10th	Night	17% 6% 11% 46% 19% 1	2732
	11th to 20th	Night	37% 11% 27% 15% 9% 1	2929
	21st to end	Night	39% 8% 22% 24% 7%	3245
September	1st to 10th	Night	31% 8% 19% 29% 12% 2	1994
	11th to 20th	Night	44% 8% 15% 16% 15% 3	2080
	21st to end	Night	47% 8% 19% 16% 8% 1	2240
October	1st to 10th	Night	58% 7% 16% 13% 5%	3920
	11th to 20th	Night	61% 6% 13% 17% 2	3897
	21st to end	Night	61% 8% 14% 13% 4	4581
November	1st to 10th	Night	71% 8% 9% 8% 4 1	2870
	11th to 20th	Night	70% 8% 9% 8% 4 1	2940
	21st to end	Night	68% 7% 10% 9% 5% 1	2940
December	1st to 10th	Night	64% 7% 15% 11% 3 1	4996
	11th to 20th	Night	78% 6% 8% 6% 2	5706
	21st to end	Night	75% 7% 8% 7% 1	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	43% 11% 20% 15% 7% 4	220
	11th to 20th	Day	39% 10% 20% 16% 13% 3	220
	21st to end	Day	39% 11% 16% 20% 10% 3	319
February	1st to 10th	Day	40% 12% 23% 17% 8%	430
	11th to 20th	Day	31% 11% 29% 19% 9%	411
	21st to end	Day	36% 13% 26% 16% 8% 1	331
March	1st to 10th	Day	32% 13% 21% 21% 10% 3	476
	11th to 20th	Day	33% 15% 17% 20% 13% 2	500
	21st to end	Day	34% 16% 24% 18% 7% 1	550
April	1st to 10th	Day	31% 16% 27% 17% 8% 1	500
	11th to 20th	Day	26% 17% 27% 18% 11% 2	492
	21st to end	Day	26% 15% 29% 18% 10% 2	500
May	1st to 10th	Day	20% 13% 25% 30% 10% 1	503
	11th to 20th	Day	21% 8% 26% 29% 14% 2	528
	21st to end	Day	20% 11% 28% 27% 12% 2	774
June	1st to 10th	Day	23% 16% 25% 25% 11% 1	730
	11th to 20th	Day	17% 14% 32% 24% 12% 1	730
	21st to end	Day	18% 10% 25% 31% 15% 2	730
July	1st to 10th	Day	15% 8% 26% 31% 17% 2	721
	11th to 20th	Day	9% 9% 26% 35% 19% 3	718
	21st to end	Day	7% 7% 20% 36% 27% 4	760
August	1st to 10th	Day	10% 5% 19% 32% 26% 8%	527
	11th to 20th	Day	11% 4 23% 33% 24% 4	517
	21st to end	Day	15% 9% 18% 33% 20% 5%	583
September	1st to 10th	Day	13% 8% 25% 30% 18% 6%	530
	11th to 20th	Day	25% 10% 18% 25% 19% 3	530
	21st to end	Day	28% 13% 20% 24% 14% 2	530
October	1st to 10th	Day	31% 9% 21% 19% 16% 3	530
	11th to 20th	Day	35% 12% 19% 15% 14% 4	530
	21st to end	Day	37% 13% 22% 17% 9% 3	437
November	1st to 10th	Day	40% 14% 25% 12% 10%	220
	11th to 20th	Day	39% 13% 19% 11% 13% 5%	220
	21st to end	Day	46% 10% 14% 14% 11% 5%	220
December	1st to 10th	Day	38% 11% 17% 12% 15% 6%	220
	11th to 20th	Day	50% 9% 15% 17% 8% 1	220
	21st to end	Day	44% 12% 17% 21% 5% 1	242
January	1st to 10th	Night	47% 10% 16% 16% 9% 2	950
	11th to 20th	Night	40% 8% 15% 23% 14% 1	950
	21st to end	Night	39% 7% 18% 21% 13% 2	1009
February	1st to 10th	Night	39% 10% 18% 25% 8%	840
	11th to 20th	Night	32% 10% 18% 29% 10%	804
	21st to end	Night	37% 13% 17% 22% 8% 2	660
March	1st to 10th	Night	33% 11% 22% 20% 13% 2	800
	11th to 20th	Night	36% 12% 19% 20% 13% 1	800
	21st to end	Night	36% 9% 19% 20% 15% 2	880
April	1st to 10th	Night	31% 8% 20% 25% 13% 2	800
	11th to 20th	Night	26% 9% 25% 26% 12% 2	595
	21st to end	Night	27% 9% 22% 27% 14% 2	591
May	1st to 10th	Night	20% 8% 23% 31% 17% 2	400
	11th to 20th	Night	22% 6% 18% 32% 20% 3	394
	21st to end	Night	21% 8% 20% 32% 19% 1	433
June	1st to 10th	Night	23% 10% 19% 35% 13% 2	400
	11th to 20th	Night	21% 6% 23% 32% 17% 1	400
	21st to end	Night	21% 4 19% 32% 22% 2	400
July	1st to 10th	Night	12% 7% 18% 31% 28% 3	390
	11th to 20th	Night	10% 5% 21% 37% 26% 2	388
	21st to end	Night	8% 3 15% 37% 30% 6%	438
August	1st to 10th	Night	9% 4 11% 31% 37% 9%	477
	11th to 20th	Night	10% 2 15% 34% 33% 6%	594
	21st to end	Night	16% 5% 16% 30% 28% 5%	660
September	1st to 10th	Night	12% 4 16% 33% 28% 8%	794
	11th to 20th	Night	21% 8% 13% 21% 29% 9%	800
	21st to end	Night	29% 7% 18% 22% 19% 4	800
October	1st to 10th	Night	30% 7% 15% 24% 22% 3	800
	11th to 20th	Night	36% 6% 17% 21% 17% 4	800
	21st to end	Night	39% 9% 17% 20% 11% 3	880
November	1st to 10th	Night	44% 9% 19% 20% 8%	820
	11th to 20th	Night	41% 9% 22% 17% 9% 1	840
	21st to end	Night	39% 9% 20% 19% 11% 2	840
December	1st to 10th	Night	36% 7% 20% 21% 12% 3	934
	11th to 20th	Night	49% 10% 17% 16% 7% 1	950
	21st to end	Night	45% 10% 23% 18% 4	1045

Page generated at 2026-02-12 22:42:14. Version ac07

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