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 2024-11-05.

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	26% 9% 3 7% 4 4 4 3 5% 6% 29%	105510
	Night	31% 11% 3 6% 4 3 3 3 4 5% 28%	102135
Transparency	Day	56% 7% 13% 16% 7% 1	105250
	Night	60% 6% 11% 15% 7% 1	102041
Seeing	Day	30% 8% 18% 24% 16% 5%	15869
	Night	36% 6% 11% 22% 18% 6%	23747

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	46% 11% 2 5% 3 3 3 2 4 4 16%	2219
	11th to 20th	Day	34% 13% 4 6% 4 3 3 3 3 5% 22%	2199
	21st to end	Day	57% 11% 3 5% 4 2 2 1 2 3 10%	2720
February	1st to 10th	Day	41% 13% 3 5% 3 3 3 3 6% 4 16%	1710
	11th to 20th	Day	34% 11% 3 7% 4 4 3 2 3 4 25%	1665
	21st to end	Day	31% 9% 3 7% 4 3 4 3 5% 5% 24%	1423
March	1st to 10th	Day	29% 13% 3 7% 5% 4 4 3 5% 7% 21%	3301
	11th to 20th	Day	30% 10% 3 8% 4 4 4 2 3 4 27%	3490
	21st to end	Day	31% 11% 3 8% 4 4 4 4 5% 6% 22%	3825
April	1st to 10th	Day	33% 12% 3 7% 4 3 3 3 4 6% 22%	2284
	11th to 20th	Day	28% 11% 3 6% 4 4 4 3 5% 6% 26%	2438
	21st to end	Day	32% 9% 3 5% 4 4 3 3 4 6% 27%	2470
May	1st to 10th	Day	22% 7% 3 6% 4 3 4 3 4 5% 38%	4295
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 6% 8% 37%	4427
	21st to end	Day	25% 10% 3 8% 5% 4 5% 3 5% 6% 26%	5161
June	1st to 10th	Day	27% 11% 3 7% 4 4 5% 4 4 6% 25%	2850
	11th to 20th	Day	20% 11% 3 8% 5% 5% 5% 4 6% 7% 26%	2850
	21st to end	Day	23% 9% 3 8% 4 4 4 3 5% 6% 30%	2850
July	1st to 10th	Day	10% 6% 2 5% 3 4 4 3 5% 7% 51%	4740
	11th to 20th	Day	8% 8% 2 6% 4 5% 5% 4 6% 8% 45%	4740
	21st to end	Day	18% 9% 2 5% 3 4 4 4 6% 8% 36%	5138
August	1st to 10th	Day	9% 7% 3 8% 4 6% 7% 5% 8% 12% 31%	4107
	11th to 20th	Day	17% 12% 4 10% 5% 5% 5% 4 6% 7% 25%	4026
	21st to end	Day	18% 7% 2 6% 3 3 4 3 4 8% 40%	4521
September	1st to 10th	Day	17% 7% 2 7% 5% 4 5% 4 6% 7% 37%	2328
	11th to 20th	Day	23% 8% 3 6% 4 5% 5% 4 5% 6% 31%	2123
	21st to end	Day	26% 8% 2 6% 2 3 4 2 4 6% 36%	2090
October	1st to 10th	Day	29% 9% 3 7% 5% 4 5% 4 5% 6% 23%	3193
	11th to 20th	Day	36% 7% 3 8% 4 4 4 2 5% 5% 21%	3161
	21st to end	Day	30% 9% 4 8% 4 4 4 3 4 4 25%	3150
November	1st to 10th	Day	42% 10% 3 5% 5% 3 3 4 4 4 18%	1529
	11th to 20th	Day	42% 10% 3 6% 4 3 2 2 3 4 21%	1520
	21st to end	Day	41% 9% 3 6% 4 3 2 3 4 5% 21%	1510
December	1st to 10th	Day	32% 11% 2 6% 4 4 4 4 4 5% 25%	1330
	11th to 20th	Day	45% 10% 3 6% 3 4 3 2 3 4 16%	1685
	21st to end	Day	51% 10% 3 6% 3 3 3 2 3 3 13%	2442
January	1st to 10th	Night	43% 14% 4 6% 4 3 3 2 3 3 15%	4726
	11th to 20th	Night	38% 9% 2 6% 3 3 3 2 3 5% 26%	4699
	21st to end	Night	60% 10% 2 4 2 2 2 2 2 2 10%	4939
February	1st to 10th	Night	39% 12% 3 5% 3 3 4 3 4 5% 19%	2470
	11th to 20th	Night	32% 13% 3 6% 3 3 3 2 3 4 28%	2402
	21st to end	Night	33% 13% 3 8% 4 3 2 3 4 4 24%	2027
March	1st to 10th	Night	29% 14% 3 7% 5% 4 4 3 4 5% 22%	3568
	11th to 20th	Night	25% 14% 4 9% 4 4 3 3 4 4 26%	3489
	21st to end	Night	33% 14% 4 8% 4 3 3 2 3 3 23%	3828
April	1st to 10th	Night	31% 12% 3 6% 5% 4 4 3 3 5% 24%	1893
	11th to 20th	Night	30% 12% 2 5% 4 3 3 3 5% 5% 27%	1691
	21st to end	Night	30% 10% 3 7% 5% 4 4 3 3 3 28%	1710
May	1st to 10th	Night	19% 8% 2 5% 4 3 3 3 4 7% 42%	2668
	11th to 20th	Night	13% 7% 3 6% 4 4 4 4 5% 8% 42%	2463
	21st to end	Night	26% 10% 3 6% 4 4 4 3 4 5% 31%	2414
June	1st to 10th	Night	27% 10% 3 6% 6% 5% 4 4 3 6% 27%	1330
	11th to 20th	Night	22% 12% 4 6% 4 4 4 3 5% 7% 30%	1330
	21st to end	Night	19% 10% 4 7% 5% 4 5% 3 5% 6% 32%	1330
July	1st to 10th	Night	10% 8% 2 4 2 2 2 3 5% 6% 57%	2220
	11th to 20th	Night	8% 10% 2 3 3 2 3 3 4 6% 56%	2220
	21st to end	Night	17% 10% 3 6% 3 3 4 3 4 5% 44%	2414
August	1st to 10th	Night	7% 8% 4 8% 5% 4 4 2 5% 8% 45%	2830
	11th to 20th	Night	18% 14% 3 7% 5% 4 4 3 5% 6% 31%	2812
	21st to end	Night	16% 9% 3 6% 3 3 3 3 4 6% 45%	3146
September	1st to 10th	Night	13% 8% 2 5% 4 3 3 3 6% 7% 45%	1852
	11th to 20th	Night	22% 10% 3 6% 3 3 4 3 4 5% 37%	2053
	21st to end	Night	29% 6% 2 5% 3 3 3 2 4 7% 37%	2090
October	1st to 10th	Night	33% 9% 3 7% 4 3 3 3 3 5% 27%	3786
	11th to 20th	Night	40% 8% 2 7% 3 3 3 3 4 5% 21%	3777
	21st to end	Night	33% 9% 3 7% 4 3 3 3 3 5% 27%	4397
November	1st to 10th	Night	41% 10% 3 6% 4 4 4 3 4 4 18%	2648
	11th to 20th	Night	38% 12% 3 7% 4 4 4 2 3 4 20%	2660
	21st to end	Night	41% 9% 2 6% 3 3 3 2 3 4 23%	2669
December	1st to 10th	Night	32% 12% 3 7% 4 4 3 3 4 4 24%	2850
	11th to 20th	Night	46% 11% 3 6% 4 3 3 2 3 3 16%	3520
	21st to end	Night	50% 11% 3 6% 3 3 3 1 3 3 14%	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	73% 5% 7% 9% 5% 1	2219
	11th to 20th	Day	66% 6% 6% 14% 6% 2	2220
	21st to end	Day	83% 3 4 6% 3	2720
February	1st to 10th	Day	72% 6% 7% 8% 4 2	1710
	11th to 20th	Day	65% 5% 7% 13% 8% 1	1674
	21st to end	Day	63% 7% 8% 12% 8% 3	1423
March	1st to 10th	Day	61% 11% 8% 12% 7%	3301
	11th to 20th	Day	60% 6% 9% 17% 7% 1	3490
	21st to end	Day	63% 9% 16% 10% 2	3825
April	1st to 10th	Day	66% 8% 11% 11% 4 1	2284
	11th to 20th	Day	61% 9% 8% 14% 8% 1	2438
	21st to end	Day	61% 9% 9% 14% 7% 1	2470
May	1st to 10th	Day	49% 8% 15% 21% 7%	4295
	11th to 20th	Day	45% 13% 19% 18% 4	4430
	21st to end	Day	58% 12% 14% 10% 5% 1	5162
June	1st to 10th	Day	60% 11% 14% 10% 4 1	2850
	11th to 20th	Day	59% 11% 13% 12% 4	2850
	21st to end	Day	54% 8% 17% 14% 6% 1	2850
July	1st to 10th	Day	34% 6% 13% 21% 19% 8%	4666
	11th to 20th	Day	33% 7% 18% 32% 10%	4659
	21st to end	Day	42% 6% 22% 22% 8% 1	4976
August	1st to 10th	Day	34% 7% 16% 35% 7% 1	4089
	11th to 20th	Day	54% 7% 21% 10% 5% 2	4065
	21st to end	Day	43% 8% 20% 22% 7%	4520
September	1st to 10th	Day	44% 9% 15% 20% 9% 3	2328
	11th to 20th	Day	52% 8% 13% 14% 11% 1	2123
	21st to end	Day	50% 7% 14% 18% 8% 2	2090
October	1st to 10th	Day	61% 6% 15% 12% 6% 1	3193
	11th to 20th	Day	65% 5% 11% 15% 4	3161
	21st to end	Day	63% 4 9% 16% 7% 1	3150
November	1st to 10th	Day	71% 6% 9% 8% 5% 1	1529
	11th to 20th	Day	70% 5% 7% 9% 8% 2	1520
	21st to end	Day	67% 4 9% 13% 5% 2	1510
December	1st to 10th	Day	63% 6% 11% 11% 7% 2	1330
	11th to 20th	Day	74% 3 8% 8% 4 2	1688
	21st to end	Day	78% 5% 6% 6% 3 1	2442
January	1st to 10th	Night	76% 4 7% 8% 4 1	4726
	11th to 20th	Night	61% 5% 8% 15% 10% 2	4740
	21st to end	Night	83% 3 4 7% 3 1	4939
February	1st to 10th	Night	69% 7% 7% 9% 6% 2	2470
	11th to 20th	Night	62% 5% 9% 11% 10% 2	2404
	21st to end	Night	64% 5% 9% 14% 7% 2	2027
March	1st to 10th	Night	62% 8% 10% 14% 6% 1	3568
	11th to 20th	Night	61% 5% 9% 15% 10% 1	3490
	21st to end	Night	67% 7% 11% 11% 4	3828
April	1st to 10th	Night	64% 6% 10% 13% 6% 1	1893
	11th to 20th	Night	58% 7% 10% 17% 7% 2	1691
	21st to end	Night	63% 5% 8% 15% 8% 1	1710
May	1st to 10th	Night	42% 6% 20% 23% 9%	2668
	11th to 20th	Night	43% 9% 21% 19% 7% 1	2463
	21st to end	Night	55% 10% 12% 16% 4 3	2414
June	1st to 10th	Night	59% 7% 16% 12% 4 2	1330
	11th to 20th	Night	56% 9% 15% 15% 5%	1330
	21st to end	Night	52% 8% 18% 16% 6% 1	1330
July	1st to 10th	Night	31% 5% 10% 25% 19% 10%	2185
	11th to 20th	Night	29% 7% 14% 39% 9%	2178
	21st to end	Night	43% 5% 19% 24% 7% 1	2337
August	1st to 10th	Night	37% 9% 14% 32% 8% 1	2823
	11th to 20th	Night	55% 5% 19% 13% 6% 3	2839
	21st to end	Night	42% 5% 20% 25% 7%	3146
September	1st to 10th	Night	39% 7% 16% 25% 11% 3	1852
	11th to 20th	Night	49% 6% 14% 16% 13% 2	2053
	21st to end	Night	49% 7% 14% 17% 9% 3	2090
October	1st to 10th	Night	60% 4 14% 15% 7% 1	3786
	11th to 20th	Night	67% 3 9% 14% 6%	3777
	21st to end	Night	62% 4 11% 14% 8% 1	4397
November	1st to 10th	Night	71% 6% 8% 10% 5% 1	2648
	11th to 20th	Night	71% 6% 7% 8% 6% 2	2660
	21st to end	Night	67% 5% 9% 11% 6% 2	2669
December	1st to 10th	Night	65% 5% 11% 11% 6% 3	2850
	11th to 20th	Night	76% 5% 7% 6% 5% 2	3516
	21st to end	Night	77% 5% 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	52% 9% 14% 17% 4 3	180
	11th to 20th	Day	48% 11% 15% 13% 11% 3	180
	21st to end	Day	48% 8% 13% 14% 12% 4	359
February	1st to 10th	Day	49% 8% 17% 20% 5% 1	370
	11th to 20th	Day	40% 10% 19% 19% 10% 1	365
	21st to end	Day	37% 11% 23% 20% 7% 2	307
March	1st to 10th	Day	35% 11% 16% 21% 13% 3	417
	11th to 20th	Day	38% 9% 18% 21% 11% 3	460
	21st to end	Day	41% 9% 17% 20% 10% 2	506
April	1st to 10th	Day	41% 10% 20% 21% 7% 2	460
	11th to 20th	Day	30% 10% 25% 18% 13% 4	452
	21st to end	Day	35% 12% 25% 17% 8% 4	460
May	1st to 10th	Day	24% 10% 22% 26% 16% 3	463
	11th to 20th	Day	24% 7% 21% 27% 18% 3	511
	21st to end	Day	21% 11% 20% 31% 14% 3	735
June	1st to 10th	Day	32% 10% 17% 26% 13% 3	680
	11th to 20th	Day	21% 10% 27% 25% 13% 3	680
	21st to end	Day	23% 6% 19% 27% 20% 4	680
July	1st to 10th	Day	21% 5% 18% 31% 22% 3	671
	11th to 20th	Day	13% 6% 19% 33% 24% 6%	668
	21st to end	Day	14% 3 17% 27% 31% 8%	739
August	1st to 10th	Day	15% 6% 12% 29% 28% 10%	497
	11th to 20th	Day	15% 4 14% 27% 30% 9%	477
	21st to end	Day	21% 8% 17% 27% 20% 7%	539
September	1st to 10th	Day	21% 6% 19% 28% 19% 7%	490
	11th to 20th	Day	28% 8% 15% 22% 20% 8%	490
	21st to end	Day	31% 8% 17% 23% 16% 5%	490
October	1st to 10th	Day	31% 7% 16% 24% 18% 6%	490
	11th to 20th	Day	41% 9% 13% 19% 13% 5%	490
	21st to end	Day	36% 11% 20% 19% 10% 4	448
November	1st to 10th	Day	46% 6% 17% 20% 9% 3	197
	11th to 20th	Day	45% 8% 13% 12% 11% 11%	180
	21st to end	Day	47% 8% 16% 9% 12% 8%	180
December	1st to 10th	Day	41% 11% 14% 13% 11% 9%	180
	11th to 20th	Day	46% 7% 15% 17% 12% 4	180
	21st to end	Day	49% 8% 13% 19% 10% 1	198
January	1st to 10th	Night	54% 9% 13% 15% 7% 2	850
	11th to 20th	Night	50% 7% 11% 20% 11% 1	850
	21st to end	Night	49% 7% 11% 19% 13% 1	929
February	1st to 10th	Night	48% 6% 15% 24% 6% 1	760
	11th to 20th	Night	37% 8% 17% 25% 12%	744
	21st to end	Night	41% 7% 17% 24% 9% 2	628
March	1st to 10th	Night	38% 10% 12% 19% 17% 4	760
	11th to 20th	Night	39% 10% 13% 23% 13% 3	760
	21st to end	Night	42% 9% 13% 18% 15% 4	836
April	1st to 10th	Night	38% 6% 12% 23% 16% 4	705
	11th to 20th	Night	36% 7% 10% 27% 17% 4	563
	21st to end	Night	34% 7% 13% 26% 17% 3	570
May	1st to 10th	Night	27% 6% 8% 27% 27% 5%	456
	11th to 20th	Night	25% 5% 6% 23% 33% 8%	374
	21st to end	Night	24% 6% 7% 28% 28% 6%	411
June	1st to 10th	Night	31% 4 9% 22% 28% 6%	380
	11th to 20th	Night	27% 6% 9% 29% 24% 5%	380
	21st to end	Night	22% 5% 9% 28% 29% 8%	380
July	1st to 10th	Night	22% 3 6% 18% 38% 14%	370
	11th to 20th	Night	15% 2 7% 21% 39% 16%	368
	21st to end	Night	14% 3 4 20% 38% 21%	416
August	1st to 10th	Night	19% 2 2 15% 35% 26%	559
	11th to 20th	Night	17% 1 4 18% 38% 23%	564
	21st to end	Night	23% 4 6% 23% 34% 11%	627
September	1st to 10th	Night	19% 3 7% 24% 32% 16%	712
	11th to 20th	Night	25% 3 8% 22% 27% 14%	760
	21st to end	Night	32% 4 11% 24% 23% 6%	760
October	1st to 10th	Night	32% 4 10% 23% 24% 6%	760
	11th to 20th	Night	40% 4 9% 23% 19% 6%	760
	21st to end	Night	42% 7% 11% 26% 11% 3	836
November	1st to 10th	Night	46% 8% 18% 21% 8%	760
	11th to 20th	Night	43% 12% 15% 19% 9% 3	760
	21st to end	Night	44% 8% 13% 21% 10% 3	764
December	1st to 10th	Night	37% 9% 16% 22% 12% 4	850
	11th to 20th	Night	48% 9% 16% 17% 10% 1	850
	21st to end	Night	49% 9% 16% 21% 5%	935

Page generated at 2024-11-02 23:11:23. Version ac07

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