Malahat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Malahat clear sky chart from 2005-11-06 to 2026-06-01.

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	14% 9% 3 8% 5% 5% 5% 4 5% 7% 35%	135920
	Night	16% 10% 3 8% 5% 5% 5% 4 5% 6% 34%	135929
Transparency	Day	28% 41% 12% 14% 6% 1	135628
	Night	31% 39% 10% 13% 6% 1	135799
Seeing	Day	16% 9% 21% 27% 22% 5%	17385
	Night	20% 9% 18% 27% 21% 5%	25657

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	24% 17% 5% 11% 6% 6% 5% 3 5% 4 13%	4125
	11th to 20th	Day	16% 9% 4 8% 4 4 5% 4 6% 7% 34%	4119
	21st to end	Day	22% 14% 4 10% 5% 5% 5% 4 5% 4 22%	5382
February	1st to 10th	Day	22% 16% 4 10% 7% 6% 5% 4 5% 6% 14%	1890
	11th to 20th	Day	20% 18% 4 10% 6% 4 4 3 5% 5% 21%	1845
	21st to end	Day	19% 14% 4 11% 8% 6% 5% 4 5% 6% 18%	1558
March	1st to 10th	Day	15% 15% 5% 11% 7% 7% 6% 5% 6% 6% 17%	4858
	11th to 20th	Day	17% 13% 4 10% 6% 5% 5% 4 5% 6% 26%	5110
	21st to end	Day	19% 13% 5% 12% 6% 6% 6% 5% 6% 6% 15%	5691
April	1st to 10th	Day	19% 12% 4 9% 7% 6% 7% 4 7% 7% 19%	2520
	11th to 20th	Day	16% 11% 4 9% 7% 6% 6% 4 6% 6% 24%	2613
	21st to end	Day	18% 10% 3 8% 5% 5% 5% 4 5% 7% 28%	2742
May	1st to 10th	Day	11% 7% 2 8% 6% 5% 5% 4 5% 6% 41%	6460
	11th to 20th	Day	10% 9% 3 8% 5% 5% 6% 5% 7% 10% 32%	6417
	21st to end	Day	13% 8% 3 8% 5% 5% 5% 4 7% 9% 33%	7184
June	1st to 10th	Day	15% 8% 3 7% 5% 4 6% 5% 9% 8% 32%	3001
	11th to 20th	Day	11% 8% 3 9% 6% 6% 6% 4 7% 9% 31%	3000
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 4 7% 8% 40%	3000
July	1st to 10th	Day	4 3 1 4 2 3 3 3 4 6% 65%	6780
	11th to 20th	Day	4 3 1 3 2 2 3 2 4 5% 72%	6780
	21st to end	Day	5% 3 1 3 2 3 3 3 5% 8% 63%	6978
August	1st to 10th	Day	5% 3 1 3 2 2 3 2 4 6% 69%	4398
	11th to 20th	Day	8% 8% 4 10% 5% 4 4 4 6% 7% 40%	4156
	21st to end	Day	10% 5% 2 7% 5% 4 4 4 6% 7% 45%	4578
September	1st to 10th	Day	8% 5% 2 5% 4 3 4 4 6% 8% 50%	2400
	11th to 20th	Day	12% 7% 3 6% 5% 4 4 4 5% 7% 42%	2364
	21st to end	Day	16% 7% 3 7% 4 5% 4 4 5% 8% 39%	2126
October	1st to 10th	Day	14% 7% 2 7% 6% 7% 7% 6% 8% 8% 28%	3280
	11th to 20th	Day	23% 10% 4 9% 5% 5% 5% 3 5% 7% 24%	3261
	21st to end	Day	17% 11% 4 10% 6% 5% 5% 5% 7% 7% 22%	3326
November	1st to 10th	Day	27% 12% 4 9% 7% 5% 6% 3 5% 6% 15%	1648
	11th to 20th	Day	25% 13% 4 10% 5% 5% 4 3 5% 4 21%	1680
	21st to end	Day	26% 13% 4 10% 5% 5% 5% 4 4 6% 19%	1680
December	1st to 10th	Day	16% 14% 5% 9% 6% 5% 6% 4 5% 6% 25%	2680
	11th to 20th	Day	30% 14% 4 10% 6% 5% 5% 4 4 5% 13%	2715
	21st to end	Day	25% 20% 6% 11% 6% 6% 5% 3 4 4 10%	3575
January	1st to 10th	Night	26% 17% 5% 11% 6% 6% 5% 4 4 4 12%	8770
	11th to 20th	Night	16% 9% 4 7% 3 3 4 3 5% 7% 39%	8779
	21st to end	Night	21% 13% 4 9% 5% 5% 4 3 4 6% 28%	8794
February	1st to 10th	Night	22% 13% 5% 9% 6% 5% 5% 4 5% 6% 20%	2730
	11th to 20th	Night	18% 13% 4 8% 5% 4 5% 3 5% 6% 29%	2662
	21st to end	Night	20% 14% 4 8% 6% 5% 5% 4 5% 5% 24%	2247
March	1st to 10th	Night	13% 10% 3 8% 6% 6% 6% 5% 7% 9% 26%	5254
	11th to 20th	Night	12% 11% 3 9% 5% 7% 6% 5% 6% 7% 30%	5109
	21st to end	Night	20% 14% 5% 11% 6% 6% 5% 4 6% 5% 19%	5525
April	1st to 10th	Night	17% 10% 3 8% 6% 5% 5% 4 6% 7% 28%	2100
	11th to 20th	Night	14% 9% 3 7% 6% 4 5% 4 5% 8% 33%	1955
	21st to end	Night	16% 9% 3 7% 5% 4 5% 4 5% 8% 35%	1876
May	1st to 10th	Night	10% 7% 3 7% 4 3 3 2 4 5% 52%	3720
	11th to 20th	Night	9% 6% 3 7% 4 5% 4 4 7% 9% 43%	3696
	21st to end	Night	11% 7% 3 8% 6% 5% 6% 5% 7% 8% 33%	3929
June	1st to 10th	Night	13% 7% 3 7% 5% 4 4 4 5% 6% 42%	1400
	11th to 20th	Night	10% 5% 2 6% 4 5% 4 5% 7% 11% 40%	1400
	21st to end	Night	8% 4 2 4 3 4 4 4 6% 10% 51%	1400
July	1st to 10th	Night	4 3 1 3 2 3 2 2 3 6% 70%	3180
	11th to 20th	Night	2 1 1 2 2 1 2 2 3 4 80%	3180
	21st to end	Night	5% 2 1 3 2 2 3 3 4 6% 71%	3850
August	1st to 10th	Night	3 2 2 2 2 2 2 4 6% 74%	2740
	11th to 20th	Night	8% 6% 2 6% 4 4 4 3 5% 7% 51%	2902
	21st to end	Night	10% 3 1 4 3 3 4 3 6% 10% 54%	3334
September	1st to 10th	Night	5% 3 2 4 3 4 4 3 6% 6% 62%	2000
	11th to 20th	Night	12% 6% 2 5% 4 3 4 3 4 6% 49%	2033
	21st to end	Night	13% 6% 3 6% 4 4 4 3 5% 7% 44%	2273
October	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 7% 42%	3920
	11th to 20th	Night	21% 8% 3 8% 5% 5% 4 4 6% 7% 30%	3897
	21st to end	Night	18% 10% 4 8% 5% 5% 5% 4 5% 7% 29%	4473
November	1st to 10th	Night	25% 11% 3 9% 6% 6% 6% 3 5% 6% 21%	2870
	11th to 20th	Night	25% 11% 3 8% 6% 5% 5% 4 5% 6% 23%	2940
	21st to end	Night	22% 13% 4 10% 6% 5% 5% 3 5% 5% 22%	2940
December	1st to 10th	Night	16% 11% 4 11% 6% 5% 6% 5% 5% 6% 26%	4718
	11th to 20th	Night	30% 16% 5% 10% 6% 6% 4 3 4 4 12%	5710
	21st to end	Night	22% 14% 5% 12% 7% 6% 6% 3 5% 5% 15%	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	54% 26% 8% 9% 3	4125
	11th to 20th	Day	36% 26% 13% 19% 6%	4140
	21st to end	Day	50% 28% 6% 11% 5%	5383
February	1st to 10th	Day	29% 61% 3 4 3 1	1890
	11th to 20th	Day	28% 60% 4 6% 1	1854
	21st to end	Day	26% 61% 6% 4 2 1	1558
March	1st to 10th	Day	41% 36% 10% 10% 4	4858
	11th to 20th	Day	36% 33% 9% 19% 3	5110
	21st to end	Day	45% 35% 11% 8% 2	5691
April	1st to 10th	Day	22% 63% 6% 8% 1	2520
	11th to 20th	Day	22% 62% 6% 6% 3 1	2613
	21st to end	Day	19% 61% 7% 9% 3 1	2742
May	1st to 10th	Day	24% 32% 15% 20% 9% 1	6460
	11th to 20th	Day	29% 39% 18% 12% 2	6420
	21st to end	Day	30% 35% 17% 16% 3 1	7185
June	1st to 10th	Day	14% 65% 9% 8% 3	3001
	11th to 20th	Day	15% 64% 8% 8% 4	3000
	21st to end	Day	14% 64% 9% 10% 3	3000
July	1st to 10th	Day	11% 27% 18% 20% 17% 7%	6706
	11th to 20th	Day	7% 27% 15% 27% 22% 2	6699
	21st to end	Day	14% 28% 28% 23% 7%	6782
August	1st to 10th	Day	7% 37% 7% 33% 15% 1	4381
	11th to 20th	Day	24% 44% 18% 10% 4 1	4195
	21st to end	Day	24% 40% 12% 16% 7%	4577
September	1st to 10th	Day	14% 62% 10% 9% 5%	2400
	11th to 20th	Day	18% 61% 7% 9% 6%	2364
	21st to end	Day	19% 60% 8% 9% 4	2126
October	1st to 10th	Day	30% 41% 13% 13% 2	3280
	11th to 20th	Day	39% 39% 7% 11% 4	3261
	21st to end	Day	36% 41% 10% 9% 4	3326
November	1st to 10th	Day	33% 56% 6% 4 1	1648
	11th to 20th	Day	26% 57% 6% 7% 2 1	1680
	21st to end	Day	28% 56% 7% 5% 4	1680
December	1st to 10th	Day	36% 37% 10% 13% 3	2680
	11th to 20th	Day	48% 36% 8% 6% 1	2718
	21st to end	Day	54% 32% 8% 4 2	3575
January	1st to 10th	Night	57% 25% 7% 7% 3	8770
	11th to 20th	Night	32% 25% 13% 19% 11%	8820
	21st to end	Night	45% 28% 9% 15% 4	8794
February	1st to 10th	Night	27% 60% 4 4 4 1	2730
	11th to 20th	Night	26% 60% 5% 5% 3 1	2664
	21st to end	Night	23% 61% 6% 7% 3 1	2247
March	1st to 10th	Night	34% 34% 12% 14% 6%	5254
	11th to 20th	Night	32% 33% 11% 20% 4	5110
	21st to end	Night	46% 33% 9% 10% 2	5525
April	1st to 10th	Night	20% 61% 8% 9% 2	2100
	11th to 20th	Night	19% 61% 7% 9% 4 1	1955
	21st to end	Night	17% 60% 9% 9% 5% 1	1876
May	1st to 10th	Night	24% 29% 9% 22% 15% 1	3717
	11th to 20th	Night	25% 32% 20% 19% 4	3696
	21st to end	Night	31% 33% 16% 18% 2	3929
June	1st to 10th	Night	14% 62% 7% 12% 5%	1400
	11th to 20th	Night	13% 63% 8% 12% 5%	1400
	21st to end	Night	12% 61% 12% 11% 4	1400
July	1st to 10th	Night	12% 27% 13% 26% 14% 8%	3145
	11th to 20th	Night	5% 25% 15% 25% 26% 3	3138
	21st to end	Night	14% 27% 20% 28% 11% 1	3741
August	1st to 10th	Night	5% 36% 9% 27% 22% 1	2732
	11th to 20th	Night	26% 41% 17% 10% 4 2	2929
	21st to end	Night	18% 39% 13% 20% 10% 1	3334
September	1st to 10th	Night	10% 59% 12% 10% 6% 2	2000
	11th to 20th	Night	17% 59% 7% 9% 7% 1	2033
	21st to end	Night	18% 58% 7% 11% 6%	2273
October	1st to 10th	Night	25% 39% 16% 15% 5%	3920
	11th to 20th	Night	35% 38% 9% 14% 3	3897
	21st to end	Night	34% 39% 11% 10% 6%	4473
November	1st to 10th	Night	30% 55% 7% 7% 1	2870
	11th to 20th	Night	27% 56% 6% 6% 3 2	2940
	21st to end	Night	27% 57% 5% 5% 5%	2940
December	1st to 10th	Night	35% 41% 9% 13% 3	4718
	11th to 20th	Night	52% 36% 7% 3 1	5706
	21st to end	Night	45% 33% 11% 8% 2	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	28% 17% 31% 14% 10% 1	220
	11th to 20th	Day	25% 16% 24% 21% 13% 1	220
	21st to end	Day	29% 13% 23% 24% 10% 1	325
February	1st to 10th	Day	28% 16% 26% 22% 7% 1	430
	11th to 20th	Day	26% 14% 26% 25% 9%	425
	21st to end	Day	26% 19% 23% 22% 8% 1	356
March	1st to 10th	Day	21% 13% 27% 24% 14% 2	540
	11th to 20th	Day	24% 14% 22% 21% 16% 4	540
	21st to end	Day	23% 11% 26% 25% 13% 2	594
April	1st to 10th	Day	19% 14% 24% 26% 14% 3	540
	11th to 20th	Day	16% 12% 26% 29% 14% 5%	532
	21st to end	Day	18% 9% 27% 26% 16% 4	540
May	1st to 10th	Day	10% 8% 20% 36% 23% 4	543
	11th to 20th	Day	14% 9% 18% 27% 25% 7%	568
	21st to end	Day	11% 6% 24% 29% 24% 5%	666
June	1st to 10th	Day	13% 6% 23% 33% 22% 4	731
	11th to 20th	Day	10% 9% 27% 34% 18% 3	730
	21st to end	Day	8% 5% 18% 33% 30% 6%	730
July	1st to 10th	Day	7% 2 15% 32% 35% 8%	721
	11th to 20th	Day	5% 3 16% 34% 34% 9%	718
	21st to end	Day	4 3 14% 27% 39% 14%	627
August	1st to 10th	Day	6% 2 11% 27% 38% 17%	527
	11th to 20th	Day	5% 2 12% 29% 40% 13%	517
	21st to end	Day	8% 3 16% 32% 31% 10%	583
September	1st to 10th	Day	9% 2 14% 34% 32% 8%	530
	11th to 20th	Day	12% 5% 18% 29% 28% 8%	530
	21st to end	Day	15% 7% 24% 27% 24% 3	530
October	1st to 10th	Day	18% 7% 21% 25% 23% 6%	530
	11th to 20th	Day	24% 10% 21% 23% 17% 4	530
	21st to end	Day	23% 16% 28% 21% 10% 3	470
November	1st to 10th	Day	25% 13% 29% 22% 10%	220
	11th to 20th	Day	29% 10% 21% 22% 14% 3	220
	21st to end	Day	30% 10% 28% 17% 10% 6%	220
December	1st to 10th	Day	32% 12% 20% 19% 16% 2	220
	11th to 20th	Day	34% 17% 23% 16% 10%	220
	21st to end	Day	32% 16% 26% 19% 6% 1	242
January	1st to 10th	Night	31% 14% 24% 19% 10% 2	950
	11th to 20th	Night	26% 13% 17% 25% 17% 1	950
	21st to end	Night	26% 9% 18% 25% 18% 2	930
February	1st to 10th	Night	28% 14% 21% 22% 13% 3	840
	11th to 20th	Night	23% 12% 20% 27% 16% 2	824
	21st to end	Night	24% 17% 21% 21% 13% 4	692
March	1st to 10th	Night	20% 13% 21% 25% 18% 3	840
	11th to 20th	Night	23% 11% 23% 24% 16% 4	840
	21st to end	Night	22% 12% 20% 26% 16% 3	924
April	1st to 10th	Night	20% 10% 19% 28% 20% 4	840
	11th to 20th	Night	16% 8% 22% 31% 18% 4	707
	21st to end	Night	18% 6% 21% 34% 18% 3	616
May	1st to 10th	Night	11% 6% 17% 36% 26% 4	420
	11th to 20th	Night	13% 5% 18% 29% 29% 7%	414
	21st to end	Night	11% 4 18% 36% 27% 4	455
June	1st to 10th	Night	15% 6% 19% 29% 29% 3	400
	11th to 20th	Night	12% 6% 24% 33% 22% 4	400
	21st to end	Night	9% 5% 18% 29% 33% 7%	400
July	1st to 10th	Night	8% 2 12% 33% 38% 7%	390
	11th to 20th	Night	5% 1 11% 38% 38% 6%	388
	21st to end	Night	4 2 9% 31% 44% 10%	438
August	1st to 10th	Night	5% 1 8% 26% 44% 15%	477
	11th to 20th	Night	5% 2 5% 26% 48% 14%	594
	21st to end	Night	8% 2 13% 31% 38% 8%	710
September	1st to 10th	Night	6% 2 10% 34% 37% 11%	800
	11th to 20th	Night	13% 3 12% 24% 33% 15%	800
	21st to end	Night	15% 5% 16% 29% 29% 7%	800
October	1st to 10th	Night	18% 5% 14% 28% 27% 9%	800
	11th to 20th	Night	22% 7% 15% 27% 21% 8%	800
	21st to end	Night	25% 9% 19% 27% 16% 4	880
November	1st to 10th	Night	29% 11% 20% 27% 12% 1	820
	11th to 20th	Night	28% 13% 22% 23% 13% 2	840
	21st to end	Night	26% 10% 23% 23% 14% 4	840
December	1st to 10th	Night	26% 10% 18% 26% 18% 2	843
	11th to 20th	Night	29% 15% 25% 20% 9% 1	950
	21st to end	Night	31% 14% 26% 21% 7% 1	1045

Page generated at 2026-05-28 22:53:26. Version ac07

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