Tofino
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tofino clear sky chart from 2005-11-06 to 2025-10-19.

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	26% 10% 3 7% 4 4 4 3 5% 6% 28%	130769
	Night	31% 11% 3 7% 4 3 3 3 4 5% 27%	127672
Transparency	Day	56% 6% 14% 16% 7% 1	130464
	Night	61% 5% 12% 15% 7% 1	127554
Seeing	Day	30% 8% 18% 24% 16% 5%	17136
	Night	36% 6% 11% 22% 18% 6%	24961

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	45% 12% 3 6% 3 3 3 2 3 4 15%	3179
	11th to 20th	Day	25% 12% 3 6% 3 3 3 2 4 5% 33%	3159
	21st to end	Day	45% 10% 3 6% 4 3 2 1 2 2 22%	3916
February	1st to 10th	Day	39% 13% 3 5% 3 3 4 3 6% 4 16%	1800
	11th to 20th	Day	34% 11% 3 7% 4 3 3 2 3 4 25%	1755
	21st to end	Day	33% 10% 3 8% 4 3 4 3 5% 5% 23%	1496
March	1st to 10th	Day	34% 13% 3 7% 5% 4 3 2 4 5% 19%	4741
	11th to 20th	Day	28% 12% 4 10% 5% 4 4 3 4 4 23%	5000
	21st to end	Day	37% 12% 3 9% 5% 4 4 3 4 5% 16%	5486
April	1st to 10th	Day	33% 12% 3 7% 4 3 3 3 4 6% 22%	2405
	11th to 20th	Day	27% 10% 3 6% 4 4 4 3 5% 6% 27%	2568
	21st to end	Day	31% 9% 3 5% 4 4 3 3 4 7% 28%	2600
May	1st to 10th	Day	20% 8% 3 8% 5% 4 4 3 4 5% 37%	6143
	11th to 20th	Day	19% 9% 3 7% 4 4 4 4 5% 8% 33%	6355
	21st to end	Day	24% 10% 4 8% 5% 4 4 3 5% 7% 26%	7405
June	1st to 10th	Day	26% 11% 3 7% 5% 4 5% 4 4 6% 27%	3000
	11th to 20th	Day	19% 10% 3 8% 6% 6% 6% 5% 6% 7% 25%	3000
	21st to end	Day	23% 9% 3 8% 4 4 4 3 5% 6% 30%	3000
July	1st to 10th	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 46%	6780
	11th to 20th	Day	6% 7% 2 6% 4 4 4 4 6% 8% 49%	6780
	21st to end	Day	13% 9% 4 7% 4 5% 5% 4 8% 9% 31%	7375
August	1st to 10th	Day	9% 7% 3 8% 5% 6% 7% 5% 8% 11% 31%	4237
	11th to 20th	Day	18% 12% 4 10% 4 5% 5% 4 6% 7% 25%	4156
	21st to end	Day	18% 7% 2 6% 3 3 4 3 5% 8% 40%	4664
September	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 7% 36%	2450
	11th to 20th	Day	23% 8% 2 6% 4 5% 5% 4 5% 6% 32%	2235
	21st to end	Day	27% 8% 2 6% 2 3 4 2 4 6% 35%	2200
October	1st to 10th	Day	29% 9% 3 7% 5% 4 5% 4 5% 5% 24%	3293
	11th to 20th	Day	36% 7% 3 8% 4 4 4 2 5% 5% 22%	3242
	21st to end	Day	30% 9% 4 8% 4 4 4 3 4 4 25%	3150
November	1st to 10th	Day	43% 11% 3 5% 4 3 3 4 4 4 17%	1577
	11th to 20th	Day	41% 10% 3 6% 4 4 2 2 4 4 21%	1600
	21st to end	Day	40% 8% 3 7% 4 3 2 3 3 5% 21%	1589
December	1st to 10th	Day	28% 11% 3 8% 4 5% 3 4 3 6% 26%	2290
	11th to 20th	Day	51% 11% 3 6% 4 4 3 2 3 3 11%	2645
	21st to end	Day	50% 12% 4 7% 4 3 3 2 3 3 10%	3498
January	1st to 10th	Night	42% 14% 4 7% 4 3 3 2 3 3 14%	6766
	11th to 20th	Night	29% 9% 2 5% 3 2 3 3 3 5% 36%	6739
	21st to end	Night	46% 9% 2 4 2 2 2 2 2 3 25%	7052
February	1st to 10th	Night	38% 12% 3 6% 4 3 4 3 4 5% 19%	2600
	11th to 20th	Night	32% 13% 3 6% 3 3 3 2 3 5% 28%	2532
	21st to end	Night	34% 13% 3 8% 4 3 2 3 4 4 23%	2130
March	1st to 10th	Night	32% 14% 4 7% 4 4 3 2 4 5% 21%	5143
	11th to 20th	Night	25% 15% 4 9% 5% 4 3 3 4 4 24%	4999
	21st to end	Night	39% 14% 3 7% 4 4 3 2 3 3 17%	5489
April	1st to 10th	Night	31% 12% 3 6% 4 4 4 3 4 5% 24%	1992
	11th to 20th	Night	28% 12% 2 6% 4 3 3 3 5% 5% 29%	1781
	21st to end	Night	29% 10% 3 7% 5% 4 4 3 3 4 29%	1800
May	1st to 10th	Night	17% 8% 2 6% 3 3 4 3 5% 7% 42%	3824
	11th to 20th	Night	20% 7% 3 6% 4 4 5% 4 4 7% 36%	3535
	21st to end	Night	29% 10% 3 6% 4 3 4 3 4 5% 29%	3470
June	1st to 10th	Night	25% 9% 3 6% 6% 5% 4 4 3 6% 28%	1400
	11th to 20th	Night	21% 11% 4 7% 5% 4 4 3 5% 7% 30%	1400
	21st to end	Night	19% 10% 4 7% 5% 4 5% 3 5% 6% 32%	1400
July	1st to 10th	Night	10% 7% 2 5% 2 3 3 4 6% 7% 51%	3180
	11th to 20th	Night	5% 8% 3 3 2 2 2 3 3 6% 61%	3180
	21st to end	Night	12% 13% 5% 9% 3 3 4 3 4 5% 39%	3468
August	1st to 10th	Night	8% 9% 3 8% 5% 4 4 2 5% 8% 45%	2920
	11th to 20th	Night	18% 14% 3 7% 5% 4 4 3 5% 6% 31%	2902
	21st to end	Night	16% 9% 3 6% 3 3 3 3 4 6% 45%	3245
September	1st to 10th	Night	13% 9% 3 6% 5% 3 3 3 6% 7% 43%	1950
	11th to 20th	Night	22% 10% 3 5% 3 3 4 3 4 5% 37%	2161
	21st to end	Night	30% 6% 2 5% 3 3 3 2 4 7% 36%	2200
October	1st to 10th	Night	32% 8% 3 7% 4 3 3 3 4 5% 27%	3906
	11th to 20th	Night	39% 8% 2 7% 3 3 3 3 4 5% 22%	3873
	21st to end	Night	33% 9% 3 7% 4 3 3 3 3 5% 27%	4397
November	1st to 10th	Night	42% 10% 3 6% 4 4 4 3 4 4 17%	2720
	11th to 20th	Night	38% 11% 3 7% 4 4 4 2 3 4 19%	2800
	21st to end	Night	41% 9% 2 6% 3 3 3 2 3 5% 23%	2810
December	1st to 10th	Night	31% 11% 3 8% 4 4 3 3 4 5% 24%	4890
	11th to 20th	Night	47% 13% 3 8% 4 4 3 2 2 3 11%	5560
	21st to end	Night	49% 12% 3 7% 4 3 3 2 3 3 11%	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	74% 4 6% 11% 4 1	3179
	11th to 20th	Day	54% 4 13% 21% 7% 1	3180
	21st to end	Day	72% 2 8% 13% 5%	3916
February	1st to 10th	Day	71% 6% 7% 9% 5% 3	1800
	11th to 20th	Day	65% 5% 7% 13% 9% 1	1764
	21st to end	Day	64% 7% 8% 11% 7% 2	1496
March	1st to 10th	Day	67% 8% 6% 13% 6%	4741
	11th to 20th	Day	65% 5% 7% 15% 8% 1	5000
	21st to end	Day	72% 7% 12% 8% 2	5486
April	1st to 10th	Day	66% 7% 11% 11% 4 1	2405
	11th to 20th	Day	60% 8% 9% 15% 7% 1	2568
	21st to end	Day	59% 9% 11% 15% 6% 1	2600
May	1st to 10th	Day	51% 6% 13% 21% 10%	6143
	11th to 20th	Day	51% 9% 20% 17% 3	6358
	21st to end	Day	58% 9% 17% 10% 6% 1	7406
June	1st to 10th	Day	58% 10% 14% 11% 5% 1	3000
	11th to 20th	Day	59% 10% 13% 13% 4	3000
	21st to end	Day	55% 8% 17% 14% 5% 1	3000
July	1st to 10th	Day	37% 6% 20% 18% 13% 5%	6706
	11th to 20th	Day	30% 6% 21% 28% 15%	6699
	21st to end	Day	42% 5% 27% 21% 5%	7168
August	1st to 10th	Day	35% 7% 16% 35% 7% 1	4219
	11th to 20th	Day	54% 7% 21% 11% 6% 2	4195
	21st to end	Day	43% 7% 20% 21% 8% 1	4663
September	1st to 10th	Day	45% 9% 16% 19% 8% 3	2450
	11th to 20th	Day	52% 8% 14% 15% 11% 1	2235
	21st to end	Day	51% 7% 14% 18% 8% 2	2200
October	1st to 10th	Day	60% 6% 15% 12% 6% 1	3293
	11th to 20th	Day	64% 5% 11% 15% 5%	3242
	21st to end	Day	63% 4 9% 16% 7% 1	3150
November	1st to 10th	Day	72% 6% 8% 8% 5% 1	1577
	11th to 20th	Day	70% 4 7% 10% 7% 2	1600
	21st to end	Day	68% 4 9% 12% 5% 2	1589
December	1st to 10th	Day	61% 4 11% 18% 6% 1	2290
	11th to 20th	Day	81% 2 7% 6% 3 1	2648
	21st to end	Day	81% 4 6% 5% 2 1	3498
January	1st to 10th	Night	77% 3 6% 10% 4 1	6766
	11th to 20th	Night	51% 4 12% 21% 10% 1	6780
	21st to end	Night	68% 2 7% 15% 8% 1	7052
February	1st to 10th	Night	68% 7% 6% 10% 7% 2	2600
	11th to 20th	Night	62% 5% 8% 12% 10% 3	2534
	21st to end	Night	66% 4 8% 14% 6% 1	2130
March	1st to 10th	Night	65% 6% 9% 12% 8%	5143
	11th to 20th	Night	63% 4 7% 15% 10% 1	5000
	21st to end	Night	73% 5% 9% 9% 3	5489
April	1st to 10th	Night	64% 6% 10% 13% 6% 1	1992
	11th to 20th	Night	56% 6% 11% 17% 8% 2	1781
	21st to end	Night	61% 5% 10% 16% 7% 1	1800
May	1st to 10th	Night	42% 5% 18% 25% 10%	3821
	11th to 20th	Night	50% 7% 20% 17% 5% 1	3535
	21st to end	Night	58% 8% 13% 16% 3 2	3470
June	1st to 10th	Night	57% 7% 18% 12% 5% 2	1400
	11th to 20th	Night	56% 8% 16% 16% 4	1400
	21st to end	Night	52% 8% 18% 15% 6% 1	1400
July	1st to 10th	Night	34% 8% 18% 20% 13% 7%	3145
	11th to 20th	Night	26% 5% 22% 33% 13%	3138
	21st to end	Night	49% 4 23% 19% 5% 1	3370
August	1st to 10th	Night	37% 9% 14% 32% 7% 1	2913
	11th to 20th	Night	55% 5% 18% 13% 6% 3	2929
	21st to end	Night	42% 5% 20% 25% 8% 1	3245
September	1st to 10th	Night	41% 7% 15% 24% 11% 3	1950
	11th to 20th	Night	48% 6% 14% 17% 13% 2	2161
	21st to end	Night	50% 7% 14% 17% 9% 3	2200
October	1st to 10th	Night	60% 4 14% 15% 7% 1	3906
	11th to 20th	Night	66% 3 9% 15% 6%	3873
	21st to end	Night	62% 4 11% 14% 8% 1	4397
November	1st to 10th	Night	71% 6% 7% 10% 5% 1	2720
	11th to 20th	Night	71% 6% 8% 8% 6% 2	2800
	21st to end	Night	67% 4 9% 11% 6% 2	2810
December	1st to 10th	Night	64% 3 11% 16% 4 2	4890
	11th to 20th	Night	81% 3 6% 6% 3 1	5556
	21st to end	Night	80% 4 7% 6% 2 1	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	53% 9% 14% 18% 4 3	200
	11th to 20th	Day	44% 11% 14% 13% 15% 3	200
	21st to end	Day	45% 8% 13% 15% 14% 6%	390
February	1st to 10th	Day	47% 8% 17% 21% 6% 1	400
	11th to 20th	Day	41% 10% 18% 19% 11% 1	395
	21st to end	Day	40% 11% 22% 19% 6% 2	331
March	1st to 10th	Day	37% 11% 16% 21% 13% 3	452
	11th to 20th	Day	38% 9% 18% 20% 11% 3	500
	21st to end	Day	43% 9% 16% 20% 10% 2	550
April	1st to 10th	Day	40% 10% 19% 22% 8% 2	500
	11th to 20th	Day	28% 10% 26% 19% 14% 4	492
	21st to end	Day	33% 11% 24% 18% 9% 5%	500
May	1st to 10th	Day	24% 9% 23% 26% 15% 3	503
	11th to 20th	Day	25% 8% 21% 26% 17% 3	553
	21st to end	Day	21% 11% 21% 31% 14% 3	790
June	1st to 10th	Day	30% 10% 17% 28% 13% 3	730
	11th to 20th	Day	21% 9% 26% 26% 14% 3	730
	21st to end	Day	24% 6% 18% 27% 20% 4	730
July	1st to 10th	Day	20% 5% 20% 31% 21% 3	721
	11th to 20th	Day	13% 6% 20% 33% 23% 6%	718
	21st to end	Day	14% 3 16% 29% 30% 8%	794
August	1st to 10th	Day	16% 6% 12% 29% 27% 9%	537
	11th to 20th	Day	17% 4 15% 26% 28% 9%	517
	21st to end	Day	20% 8% 16% 26% 22% 9%	583
September	1st to 10th	Day	21% 6% 18% 28% 18% 7%	530
	11th to 20th	Day	29% 8% 14% 21% 21% 8%	530
	21st to end	Day	32% 8% 18% 23% 15% 5%	530
October	1st to 10th	Day	32% 7% 15% 24% 17% 5%	530
	11th to 20th	Day	40% 9% 14% 19% 14% 5%	523
	21st to end	Day	36% 11% 20% 19% 10% 4	448
November	1st to 10th	Day	48% 6% 17% 19% 9% 2	209
	11th to 20th	Day	46% 8% 13% 12% 11% 11%	200
	21st to end	Day	46% 8% 16% 10% 13% 9%	200
December	1st to 10th	Day	40% 11% 13% 14% 12% 10%	200
	11th to 20th	Day	49% 6% 16% 15% 11% 4	200
	21st to end	Day	51% 7% 13% 19% 9% 1	220
January	1st to 10th	Night	53% 9% 14% 16% 7% 2	900
	11th to 20th	Night	48% 7% 11% 22% 11% 1	900
	21st to end	Night	47% 6% 10% 20% 14% 3	983
February	1st to 10th	Night	46% 6% 16% 25% 7% 1	800
	11th to 20th	Night	38% 8% 16% 25% 13%	784
	21st to end	Night	43% 8% 16% 23% 8% 2	660
March	1st to 10th	Night	39% 10% 11% 19% 17% 4	800
	11th to 20th	Night	39% 10% 13% 23% 13% 2	800
	21st to end	Night	43% 9% 13% 18% 15% 4	880
April	1st to 10th	Night	39% 6% 12% 23% 17% 4	742
	11th to 20th	Night	34% 7% 11% 27% 17% 4	593
	21st to end	Night	32% 7% 13% 26% 18% 5%	600
May	1st to 10th	Night	26% 6% 9% 27% 27% 5%	480
	11th to 20th	Night	26% 5% 7% 22% 31% 8%	394
	21st to end	Night	26% 6% 7% 28% 27% 6%	433
June	1st to 10th	Night	29% 5% 9% 24% 28% 6%	400
	11th to 20th	Night	26% 5% 9% 30% 25% 5%	400
	21st to end	Night	23% 5% 9% 28% 28% 8%	400
July	1st to 10th	Night	21% 3 7% 19% 37% 13%	390
	11th to 20th	Night	14% 2 8% 21% 40% 15%	388
	21st to end	Night	14% 3 4 20% 39% 21%	438
August	1st to 10th	Night	20% 2 2 15% 35% 25%	589
	11th to 20th	Night	18% 1 4 18% 38% 22%	594
	21st to end	Night	22% 4 6% 22% 33% 13%	660
September	1st to 10th	Night	19% 3 7% 24% 32% 16%	750
	11th to 20th	Night	25% 3 8% 23% 28% 14%	800
	21st to end	Night	33% 4 11% 24% 22% 6%	800
October	1st to 10th	Night	31% 4 10% 24% 24% 7%	800
	11th to 20th	Night	39% 4 10% 23% 19% 6%	792
	21st to end	Night	42% 7% 11% 26% 11% 3	836
November	1st to 10th	Night	47% 7% 17% 21% 8%	780
	11th to 20th	Night	43% 12% 16% 18% 9% 2	800
	21st to end	Night	45% 8% 13% 21% 10% 3	805
December	1st to 10th	Night	37% 9% 15% 22% 13% 4	900
	11th to 20th	Night	48% 10% 16% 17% 9% 1	900
	21st to end	Night	50% 9% 15% 21% 5%	990

Page generated at 2025-10-15 22:50:28. Version ac07

Copyright © 2025 Attilla Danko.