Tumbler Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tumbler Ridge 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	7% 10% 4 10% 6% 6% 6% 5% 7% 8% 32%	130106
	Night	5% 10% 4 10% 6% 6% 6% 5% 7% 8% 33%	126646
Transparency	Day	48% 9% 16% 19% 8% 1	129792
	Night	46% 9% 16% 19% 8% 1	126539
Seeing	Day	20% 19% 29% 21% 10% 2	17639
	Night	16% 18% 29% 25% 12% 1	25416

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	2 10% 4 13% 8% 8% 8% 4 7% 8% 28%	2719
	11th to 20th	Day	4 10% 5% 13% 6% 7% 8% 5% 9% 7% 26%	2998
	21st to end	Day	3 12% 5% 10% 5% 5% 6% 5% 7% 9% 34%	3498
February	1st to 10th	Day	3 11% 5% 13% 7% 7% 8% 6% 5% 7% 28%	1593
	11th to 20th	Day	2 13% 4 13% 8% 7% 6% 5% 6% 8% 28%	1700
	21st to end	Day	3 12% 7% 13% 8% 8% 8% 6% 5% 6% 25%	1495
March	1st to 10th	Day	1 7% 3 12% 9% 8% 6% 6% 9% 9% 29%	4518
	11th to 20th	Day	3 10% 5% 14% 8% 5% 5% 5% 7% 9% 28%	4858
	21st to end	Day	4 12% 4 17% 6% 5% 5% 4 5% 6% 31%	5831
April	1st to 10th	Day	4 12% 5% 13% 8% 7% 6% 5% 7% 7% 28%	2400
	11th to 20th	Day	7% 16% 5% 11% 7% 5% 6% 4 6% 6% 27%	2580
	21st to end	Day	10% 14% 5% 10% 6% 5% 6% 4 6% 8% 28%	2800
May	1st to 10th	Day	6% 9% 4 10% 6% 6% 6% 5% 7% 8% 32%	6320
	11th to 20th	Day	7% 11% 4 10% 7% 7% 7% 6% 7% 9% 23%	6783
	21st to end	Day	10% 10% 4 10% 7% 6% 7% 5% 8% 9% 25%	7907
June	1st to 10th	Day	12% 9% 3 8% 6% 6% 6% 5% 6% 8% 30%	3200
	11th to 20th	Day	17% 9% 4 10% 7% 6% 6% 5% 7% 7% 24%	3200
	21st to end	Day	10% 8% 3 8% 7% 6% 6% 5% 7% 8% 31%	3200
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 4 6% 8% 42%	7240
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 4 6% 7% 41%	7240
	21st to end	Day	9% 6% 2 6% 5% 6% 7% 6% 8% 9% 36%	7421
August	1st to 10th	Day	8% 6% 2 6% 5% 5% 6% 4 6% 7% 45%	4532
	11th to 20th	Day	12% 7% 2 6% 4 5% 6% 5% 8% 9% 37%	4330
	21st to end	Day	12% 6% 2 8% 6% 6% 6% 5% 6% 7% 35%	4567
September	1st to 10th	Day	12% 8% 3 7% 4 5% 5% 5% 6% 8% 37%	2280
	11th to 20th	Day	12% 10% 3 7% 5% 6% 6% 4 6% 7% 35%	2280
	21st to end	Day	8% 11% 3 8% 5% 6% 7% 5% 7% 9% 30%	2023
October	1st to 10th	Day	9% 12% 3 10% 7% 6% 6% 5% 6% 7% 27%	3180
	11th to 20th	Day	8% 12% 4 9% 6% 5% 6% 5% 7% 8% 31%	3012
	21st to end	Day	5% 12% 4 11% 5% 5% 5% 5% 8% 10% 30%	2916
November	1st to 10th	Day	8% 15% 5% 11% 6% 5% 5% 4 5% 7% 29%	1568
	11th to 20th	Day	5% 14% 5% 11% 6% 7% 6% 5% 6% 7% 29%	1427
	21st to end	Day	3 12% 4 11% 10% 5% 4 5% 8% 8% 29%	1276
December	1st to 10th	Day	6% 14% 6% 13% 7% 7% 6% 5% 6% 8% 22%	1960
	11th to 20th	Day	3 15% 7% 12% 6% 8% 7% 5% 7% 7% 23%	2262
	21st to end	Day	2 11% 3 9% 6% 5% 6% 4 7% 9% 38%	2992
January	1st to 10th	Night	2 9% 5% 14% 9% 6% 6% 5% 7% 9% 28%	7226
	11th to 20th	Night	3 11% 4 11% 8% 8% 7% 6% 11% 9% 23%	6943
	21st to end	Night	4 11% 5% 10% 6% 6% 6% 5% 7% 9% 31%	7458
February	1st to 10th	Night	4 13% 5% 13% 7% 6% 6% 5% 7% 7% 27%	2806
	11th to 20th	Night	3 10% 5% 12% 7% 7% 6% 6% 7% 9% 28%	2585
	21st to end	Night	2 11% 6% 14% 8% 6% 7% 5% 6% 7% 27%	2135
March	1st to 10th	Night	6% 4 13% 9% 8% 6% 5% 7% 8% 32%	5376
	11th to 20th	Night	4 10% 5% 12% 8% 6% 7% 5% 7% 8% 28%	5139
	21st to end	Night	6% 11% 4 13% 5% 4 4 4 6% 6% 37%	5143
April	1st to 10th	Night	4 8% 5% 8% 7% 6% 6% 5% 9% 9% 36%	2000
	11th to 20th	Night	6% 12% 5% 7% 6% 5% 6% 5% 7% 8% 33%	1768
	21st to end	Night	10% 12% 4 10% 6% 4 6% 4 6% 7% 32%	1600
May	1st to 10th	Night	4 7% 3 9% 7% 6% 6% 5% 8% 9% 37%	3640
	11th to 20th	Night	7% 9% 3 8% 5% 6% 5% 5% 7% 10% 36%	3094
	21st to end	Night	10% 9% 3 8% 5% 6% 5% 5% 8% 10% 29%	2968
June	1st to 10th	Night	11% 9% 2 9% 6% 5% 6% 4 5% 7% 36%	1200
	11th to 20th	Night	15% 11% 5% 9% 6% 5% 5% 5% 6% 8% 26%	1200
	21st to end	Night	9% 6% 2 7% 6% 5% 6% 5% 9% 9% 37%	1200
July	1st to 10th	Night	9% 6% 2 6% 5% 6% 5% 4 6% 8% 43%	2720
	11th to 20th	Night	11% 6% 3 6% 4 4 4 4 6% 7% 45%	2720
	21st to end	Night	9% 7% 2 6% 4 5% 6% 5% 7% 9% 41%	3419
August	1st to 10th	Night	8% 6% 2 6% 4 4 4 3 5% 8% 50%	2486
	11th to 20th	Night	12% 5% 1 4 4 4 4 4 7% 8% 46%	2497
	21st to end	Night	9% 7% 3 9% 7% 6% 5% 5% 7% 8% 35%	3095
September	1st to 10th	Night	12% 8% 3 8% 4 5% 4 4 6% 7% 40%	1900
	11th to 20th	Night	10% 9% 2 6% 3 4 4 4 6% 10% 40%	1900
	21st to end	Night	10% 9% 4 7% 6% 5% 5% 4 7% 7% 36%	2156
October	1st to 10th	Night	9% 12% 4 11% 6% 5% 5% 4 6% 8% 29%	3800
	11th to 20th	Night	5% 8% 4 9% 6% 6% 7% 5% 7% 9% 36%	3921
	21st to end	Night	6% 14% 6% 10% 6% 6% 5% 5% 6% 7% 29%	4635
November	1st to 10th	Night	7% 13% 4 10% 7% 5% 5% 4 6% 7% 31%	2730
	11th to 20th	Night	3 14% 5% 12% 6% 6% 5% 5% 6% 8% 30%	2952
	21st to end	Night	4 14% 4 11% 7% 6% 6% 5% 8% 8% 28%	3120
December	1st to 10th	Night	3 13% 5% 11% 7% 6% 6% 4 7% 7% 29%	5220
	11th to 20th	Night	4 14% 5% 12% 9% 7% 6% 5% 6% 6% 24%	5930
	21st to end	Night	2 10% 5% 9% 6% 6% 6% 5% 8% 8% 36%	7964

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	52% 8% 17% 14% 6% 2	2719
	11th to 20th	Day	51% 9% 13% 15% 10% 1	3019
	21st to end	Day	43% 14% 20% 13% 10%	3498
February	1st to 10th	Day	55% 9% 13% 11% 10% 2	1593
	11th to 20th	Day	55% 7% 15% 16% 6% 1	1709
	21st to end	Day	58% 7% 14% 14% 5% 2	1495
March	1st to 10th	Day	47% 8% 11% 19% 13%	4518
	11th to 20th	Day	49% 8% 14% 21% 7% 1	4858
	21st to end	Day	52% 7% 12% 18% 12%	5831
April	1st to 10th	Day	54% 7% 15% 17% 6%	2400
	11th to 20th	Day	56% 7% 11% 17% 8%	2580
	21st to end	Day	54% 9% 15% 18% 5%	2800
May	1st to 10th	Day	45% 7% 14% 22% 10% 2	6320
	11th to 20th	Day	52% 9% 15% 18% 6%	6787
	21st to end	Day	51% 8% 15% 16% 10% 1	7908
June	1st to 10th	Day	50% 8% 13% 20% 8% 1	3200
	11th to 20th	Day	58% 8% 12% 18% 5%	3200
	21st to end	Day	48% 9% 15% 21% 6% 1	3200
July	1st to 10th	Day	39% 7% 15% 19% 19% 1	7161
	11th to 20th	Day	40% 8% 15% 29% 8% 1	7153
	21st to end	Day	38% 10% 21% 25% 6%	7213
August	1st to 10th	Day	36% 9% 15% 31% 10%	4514
	11th to 20th	Day	40% 10% 16% 22% 12%	4372
	21st to end	Day	47% 8% 24% 18% 3	4566
September	1st to 10th	Day	45% 8% 23% 19% 5% 1	2280
	11th to 20th	Day	48% 9% 18% 19% 7%	2280
	21st to end	Day	49% 10% 19% 17% 5% 1	2023
October	1st to 10th	Day	52% 9% 18% 16% 5%	3180
	11th to 20th	Day	48% 9% 19% 21% 3	3012
	21st to end	Day	47% 9% 28% 13% 3	2916
November	1st to 10th	Day	56% 8% 14% 17% 4 1	1568
	11th to 20th	Day	55% 10% 16% 13% 5% 1	1427
	21st to end	Day	51% 11% 17% 13% 6% 1	1276
December	1st to 10th	Day	61% 9% 14% 10% 5%	1960
	11th to 20th	Day	59% 9% 16% 12% 4	2264
	21st to end	Day	39% 9% 17% 25% 9%	2992
January	1st to 10th	Night	50% 9% 14% 17% 8% 2	7226
	11th to 20th	Night	50% 9% 13% 13% 13% 1	6984
	21st to end	Night	47% 12% 20% 12% 9%	7458
February	1st to 10th	Night	55% 8% 14% 11% 11% 1	2806
	11th to 20th	Night	51% 9% 16% 16% 6% 1	2587
	21st to end	Night	54% 8% 12% 19% 7% 1	2135
March	1st to 10th	Night	47% 7% 15% 18% 13%	5376
	11th to 20th	Night	48% 9% 11% 20% 10% 1	5140
	21st to end	Night	44% 7% 12% 24% 13%	5143
April	1st to 10th	Night	42% 10% 14% 25% 8% 1	2000
	11th to 20th	Night	48% 8% 13% 21% 9%	1768
	21st to end	Night	51% 7% 13% 21% 6% 1	1600
May	1st to 10th	Night	39% 7% 17% 24% 12% 1	3637
	11th to 20th	Night	40% 10% 17% 25% 7%	3094
	21st to end	Night	46% 10% 16% 18% 7% 2	2968
June	1st to 10th	Night	46% 7% 11% 25% 10%	1200
	11th to 20th	Night	55% 7% 13% 19% 6% 1	1200
	21st to end	Night	41% 9% 20% 23% 6%	1200
July	1st to 10th	Night	36% 8% 17% 25% 13% 1	2690
	11th to 20th	Night	37% 7% 16% 26% 13%	2684
	21st to end	Night	35% 10% 25% 25% 5%	3323
August	1st to 10th	Night	33% 8% 20% 35% 5%	2479
	11th to 20th	Night	32% 9% 18% 28% 12% 1	2521
	21st to end	Night	45% 11% 22% 18% 3	3095
September	1st to 10th	Night	44% 7% 20% 22% 5% 1	1900
	11th to 20th	Night	40% 8% 20% 26% 6%	1900
	21st to end	Night	46% 12% 16% 17% 9%	2156
October	1st to 10th	Night	50% 12% 14% 17% 6%	3800
	11th to 20th	Night	40% 11% 21% 24% 4	3921
	21st to end	Night	53% 9% 18% 16% 5%	4635
November	1st to 10th	Night	51% 10% 15% 17% 6% 1	2730
	11th to 20th	Night	53% 10% 15% 16% 6% 1	2952
	21st to end	Night	51% 11% 17% 15% 5% 1	3120
December	1st to 10th	Night	51% 9% 17% 17% 5%	5220
	11th to 20th	Night	57% 12% 13% 14% 4	5927
	21st to end	Night	42% 10% 18% 24% 6%	7964

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	16% 15% 28% 28% 9% 6%	200
	11th to 20th	Day	19% 20% 30% 23% 5% 4	200
	21st to end	Day	21% 27% 26% 17% 8%	220
February	1st to 10th	Day	17% 24% 25% 22% 12% 2	200
	11th to 20th	Day	17% 21% 31% 19% 11% 1	341
	21st to end	Day	21% 23% 35% 14% 6% 1	337
March	1st to 10th	Day	15% 20% 30% 24% 9% 2	500
	11th to 20th	Day	18% 23% 32% 18% 8% 1	500
	21st to end	Day	21% 20% 28% 19% 10% 2	550
April	1st to 10th	Day	19% 24% 30% 19% 6% 2	500
	11th to 20th	Day	23% 20% 29% 18% 7% 2	492
	21st to end	Day	24% 23% 27% 17% 7% 2	500
May	1st to 10th	Day	23% 19% 31% 18% 7% 1	503
	11th to 20th	Day	20% 15% 28% 24% 11% 3	733
	21st to end	Day	20% 16% 25% 23% 12% 3	1006
June	1st to 10th	Day	18% 21% 31% 20% 9% 2	930
	11th to 20th	Day	23% 17% 25% 21% 12% 2	930
	21st to end	Day	17% 14% 27% 23% 16% 4	930
July	1st to 10th	Day	18% 13% 26% 27% 14% 2	916
	11th to 20th	Day	17% 13% 31% 22% 15% 3	912
	21st to end	Day	15% 13% 33% 24% 11% 4	814
August	1st to 10th	Day	15% 12% 27% 26% 16% 3	553
	11th to 20th	Day	15% 22% 31% 17% 11% 3	477
	21st to end	Day	17% 22% 32% 17% 8% 3	539
September	1st to 10th	Day	23% 19% 29% 17% 7% 5%	490
	11th to 20th	Day	24% 17% 30% 18% 9% 2	490
	21st to end	Day	24% 28% 28% 13% 7% 1	490
October	1st to 10th	Day	30% 19% 27% 18% 6% 2	490
	11th to 20th	Day	24% 22% 30% 18% 5% 1	405
	21st to end	Day	19% 22% 29% 20% 8% 2	271
November	1st to 10th	Day	27% 25% 27% 14% 8% 1	200
	11th to 20th	Day	24% 30% 28% 14% 5%	200
	21st to end	Day	23% 23% 27% 18% 8% 2	200
December	1st to 10th	Day	17% 24% 28% 22% 8% 2	200
	11th to 20th	Day	17% 19% 29% 25% 10% 2	200
	21st to end	Day	18% 17% 29% 24% 10% 2	220
January	1st to 10th	Night	13% 19% 30% 27% 8% 2	1100
	11th to 20th	Night	18% 20% 31% 24% 6%	987
	21st to end	Night	18% 26% 30% 22% 3 1	990
February	1st to 10th	Night	18% 20% 23% 23% 14% 2	803
	11th to 20th	Night	12% 18% 30% 30% 9% 1	784
	21st to end	Night	12% 19% 32% 23% 12% 2	660
March	1st to 10th	Night	12% 18% 30% 30% 9% 1	800
	11th to 20th	Night	10% 20% 34% 25% 10% 1	800
	21st to end	Night	15% 15% 25% 28% 16% 2	880
April	1st to 10th	Night	11% 13% 28% 31% 14% 2	800
	11th to 20th	Night	15% 14% 28% 28% 14% 1	580
	21st to end	Night	18% 15% 26% 26% 15%	400
May	1st to 10th	Night	13% 12% 31% 27% 16% 2	400
	11th to 20th	Night	16% 8% 24% 32% 18% 2	394
	21st to end	Night	19% 10% 20% 28% 21% 2	433
June	1st to 10th	Night	14% 14% 27% 29% 15% 1	400
	11th to 20th	Night	19% 11% 23% 26% 19% 2	400
	21st to end	Night	11% 11% 25% 31% 20% 2	400
July	1st to 10th	Night	12% 7% 27% 35% 18% 1	390
	11th to 20th	Night	16% 9% 25% 29% 20% 1	388
	21st to end	Night	8% 11% 24% 33% 20% 4	438
August	1st to 10th	Night	13% 8% 20% 30% 25% 4	386
	11th to 20th	Night	11% 11% 24% 27% 25% 1	376
	21st to end	Night	13% 10% 31% 26% 18% 1	589
September	1st to 10th	Night	19% 13% 24% 29% 14% 1	760
	11th to 20th	Night	17% 11% 26% 24% 21% 2	760
	21st to end	Night	20% 23% 28% 21% 8% 1	760
October	1st to 10th	Night	23% 16% 26% 26% 9% 1	760
	11th to 20th	Night	17% 20% 30% 25% 7% 1	760
	21st to end	Night	23% 20% 31% 20% 6%	836
November	1st to 10th	Night	19% 22% 29% 20% 9% 1	780
	11th to 20th	Night	18% 25% 32% 20% 4	952
	21st to end	Night	18% 23% 33% 19% 6%	1060
December	1st to 10th	Night	13% 23% 33% 23% 6% 1	1100
	11th to 20th	Night	15% 22% 31% 22% 9% 1	1100
	21st to end	Night	15% 20% 29% 26% 9% 1	1210

Page generated at 2025-08-01 22:32:26. Version ac07

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