West Vancouver
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Vancouver clear sky chart from 2005-11-06 to 2024-02-05.

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	27% 9% 3 6% 5% 3 4 4 4 6% 29%	77787
	Night	32% 10% 3 5% 4 3 3 3 4 5% 28%	81028
Transparency	Day	58% 5% 13% 15% 6% 1	77496
	Night	60% 5% 12% 14% 7% 1	80899
Seeing	Day	24% 4 15% 26% 24% 7%	14312
	Night	31% 4 13% 24% 22% 6%	22683

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% 4 6% 6% 3 3 3 3 4 10%	2219
	11th to 20th	Day	32% 13% 4 5% 4 2 3 2 3 6% 26%	2199
	21st to end	Day	60% 8% 3 4 4 2 2 2 3 3 9%	2769
February	1st to 10th	Day	36% 12% 5% 7% 5% 3 4 4 4 6% 16%	1657
	11th to 20th	Day	33% 11% 3 6% 5% 3 4 4 3 5% 22%	1575
	21st to end	Day	26% 13% 5% 7% 6% 4 6% 4 3 5% 21%	1338
March	1st to 10th	Day	31% 12% 4 8% 6% 3 3 4 5% 4 19%	1866
	11th to 20th	Day	37% 13% 4 6% 5% 2 3 3 2 5% 19%	1980
	21st to end	Day	31% 13% 4 7% 6% 3 5% 3 3 4 19%	2227
April	1st to 10th	Day	29% 12% 4 6% 5% 5% 5% 5% 6% 6% 17%	2160
	11th to 20th	Day	26% 11% 4 7% 6% 4 4 5% 5% 6% 22%	2231
	21st to end	Day	26% 12% 4 7% 5% 3 4 5% 5% 6% 24%	2388
May	1st to 10th	Day	18% 9% 3 7% 6% 4 5% 5% 5% 6% 32%	2520
	11th to 20th	Day	18% 8% 4 7% 6% 3 5% 6% 6% 7% 30%	2477
	21st to end	Day	20% 9% 4 6% 6% 3 5% 5% 5% 7% 30%	2793
June	1st to 10th	Day	23% 9% 4 7% 6% 3 5% 4 5% 7% 28%	2700
	11th to 20th	Day	23% 9% 5% 8% 6% 3 6% 6% 5% 7% 23%	2700
	21st to end	Day	16% 7% 3 6% 6% 4 5% 5% 6% 6% 37%	2700
July	1st to 10th	Day	13% 6% 3 5% 4 3 4 5% 5% 7% 47%	2700
	11th to 20th	Day	12% 4 2 4 4 2 4 5% 5% 6% 51%	2700
	21st to end	Day	8% 3 2 4 3 2 3 3 4 7% 60%	2809
August	1st to 10th	Day	10% 5% 3 5% 4 2 4 4 4 5% 54%	2484
	11th to 20th	Day	9% 6% 2 5% 4 2 3 4 5% 6% 55%	2298
	21st to end	Day	14% 5% 2 6% 4 3 4 4 5% 8% 43%	2525
September	1st to 10th	Day	15% 7% 2 6% 4 3 4 3 5% 6% 45%	2160
	11th to 20th	Day	20% 8% 4 6% 4 3 4 4 4 6% 38%	2151
	21st to end	Day	27% 6% 2 5% 4 2 4 4 5% 7% 35%	1900
October	1st to 10th	Day	26% 7% 3 6% 4 2 3 4 4 6% 34%	1800
	11th to 20th	Day	34% 9% 3 5% 5% 3 4 4 5% 6% 23%	1800
	21st to end	Day	37% 10% 3 6% 4 2 3 3 5% 6% 23%	1828
November	1st to 10th	Day	43% 9% 3 7% 5% 3 4 3 3 4 16%	1488
	11th to 20th	Day	41% 12% 4 5% 4 3 3 3 3 4 19%	1520
	21st to end	Day	42% 9% 4 6% 3 2 4 4 3 4 19%	1520
December	1st to 10th	Day	35% 13% 4 5% 4 2 4 3 3 4 23%	1478
	11th to 20th	Day	42% 14% 4 6% 4 2 3 4 3 4 14%	1685
	21st to end	Day	46% 13% 3 6% 5% 2 4 3 3 3 10%	2442
January	1st to 10th	Night	43% 13% 4 7% 5% 3 3 3 3 4 13%	4726
	11th to 20th	Night	35% 8% 3 5% 5% 3 3 3 4 8% 23%	4699
	21st to end	Night	56% 12% 2 4 3 1 2 2 3 3 12%	4884
February	1st to 10th	Night	37% 11% 4 6% 5% 3 4 3 4 4 19%	2397
	11th to 20th	Night	30% 13% 4 6% 5% 2 4 4 3 5% 24%	2272
	21st to end	Night	29% 12% 4 5% 5% 2 4 4 4 5% 25%	1917
March	1st to 10th	Night	33% 12% 3 5% 5% 3 4 4 4 5% 23%	2093
	11th to 20th	Night	38% 11% 3 5% 5% 3 4 3 3 4 21%	1979
	21st to end	Night	35% 10% 4 7% 5% 3 5% 3 4 4 19%	2129
April	1st to 10th	Night	30% 12% 3 6% 7% 3 4 3 5% 6% 22%	1800
	11th to 20th	Night	24% 12% 4 6% 7% 3 5% 4 4 6% 26%	1677
	21st to end	Night	25% 10% 4 7% 5% 4 4 4 5% 6% 26%	1571
May	1st to 10th	Night	18% 6% 3 5% 5% 3 4 6% 6% 5% 39%	1440
	11th to 20th	Night	17% 6% 3 5% 5% 4 5% 5% 7% 7% 35%	1416
	21st to end	Night	18% 8% 3 7% 5% 3 4 4 5% 7% 36%	1479
June	1st to 10th	Night	24% 8% 4 5% 6% 3 4 5% 5% 6% 32%	1260
	11th to 20th	Night	19% 10% 3 6% 5% 3 6% 5% 6% 8% 29%	1260
	21st to end	Night	15% 5% 3 5% 6% 3 5% 5% 6% 7% 42%	1260
July	1st to 10th	Night	11% 4 2 5% 5% 3 3 3 3 7% 52%	1260
	11th to 20th	Night	9% 4 1 3 3 2 3 4 5% 7% 57%	1260
	21st to end	Night	6% 2 1 3 3 2 3 4 5% 6% 65%	1506
August	1st to 10th	Night	9% 4 1 3 4 2 3 4 4 5% 62%	1453
	11th to 20th	Night	6% 3 2 3 2 2 2 4 5% 7% 63%	1602
	21st to end	Night	11% 5% 3 6% 5% 3 5% 5% 6% 8% 45%	1830
September	1st to 10th	Night	10% 4 2 4 3 3 4 4 5% 6% 55%	1800
	11th to 20th	Night	22% 6% 2 5% 4 2 3 5% 4 6% 42%	1808
	21st to end	Night	23% 8% 3 5% 4 3 3 3 3 5% 39%	2060
October	1st to 10th	Night	22% 7% 3 6% 4 2 4 4 5% 4 39%	2160
	11th to 20th	Night	34% 8% 2 5% 3 2 4 4 3 5% 30%	2160
	21st to end	Night	37% 8% 2 5% 3 2 3 3 4 5% 27%	2528
November	1st to 10th	Night	41% 11% 3 6% 4 2 4 3 3 4 18%	2590
	11th to 20th	Night	39% 10% 3 6% 4 2 3 3 3 4 22%	2660
	21st to end	Night	40% 9% 3 6% 5% 2 3 3 4 4 21%	2660
December	1st to 10th	Night	34% 11% 3 5% 4 2 4 3 4 5% 25%	2698
	11th to 20th	Night	47% 14% 3 6% 4 2 3 3 3 4 13%	3520
	21st to end	Night	47% 14% 3 5% 3 2 2 2 3 3 15%	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	78% 5% 7% 7% 2 1	2219
	11th to 20th	Day	63% 5% 11% 11% 5% 5%	2220
	21st to end	Day	83% 3 5% 7% 2	2769
February	1st to 10th	Day	73% 5% 9% 8% 4 2	1657
	11th to 20th	Day	67% 5% 10% 12% 7%	1584
	21st to end	Day	68% 4 11% 12% 3 2	1338
March	1st to 10th	Day	69% 7% 11% 9% 4	1866
	11th to 20th	Day	73% 3 8% 10% 4 1	1980
	21st to end	Day	72% 4 11% 11% 3	2227
April	1st to 10th	Day	69% 6% 13% 9% 2	2160
	11th to 20th	Day	65% 6% 11% 11% 7% 1	2231
	21st to end	Day	64% 6% 12% 11% 6%	2388
May	1st to 10th	Day	55% 6% 17% 16% 5% 1	2520
	11th to 20th	Day	55% 7% 15% 19% 4	2480
	21st to end	Day	56% 7% 15% 19% 3	2794
June	1st to 10th	Day	59% 4 18% 12% 4 2	2700
	11th to 20th	Day	64% 6% 16% 11% 3	2700
	21st to end	Day	49% 7% 17% 17% 8% 2	2700
July	1st to 10th	Day	40% 7% 16% 23% 11% 3	2626
	11th to 20th	Day	36% 6% 19% 28% 10% 1	2619
	21st to end	Day	26% 5% 19% 31% 16% 3	2653
August	1st to 10th	Day	35% 6% 16% 30% 12% 2	2467
	11th to 20th	Day	31% 6% 20% 25% 15% 2	2298
	21st to end	Day	40% 6% 20% 26% 6% 1	2525
September	1st to 10th	Day	42% 6% 14% 24% 10% 4	2160
	11th to 20th	Day	50% 5% 11% 18% 14% 2	2151
	21st to end	Day	52% 7% 15% 16% 8% 2	1900
October	1st to 10th	Day	53% 5% 15% 18% 9%	1800
	11th to 20th	Day	63% 7% 11% 15% 4 1	1800
	21st to end	Day	64% 6% 11% 11% 7% 1	1828
November	1st to 10th	Day	74% 4 8% 9% 4 1	1488
	11th to 20th	Day	72% 3 8% 9% 6% 2	1520
	21st to end	Day	70% 4 7% 11% 7% 1	1520
December	1st to 10th	Day	66% 5% 8% 12% 8% 1	1478
	11th to 20th	Day	77% 4 7% 8% 2 2	1688
	21st to end	Day	80% 5% 6% 7% 2 1	2442
January	1st to 10th	Night	76% 5% 5% 11% 2 1	4726
	11th to 20th	Night	59% 5% 14% 12% 8% 3	4740
	21st to end	Night	81% 3 5% 8% 2 1	4884
February	1st to 10th	Night	69% 5% 10% 10% 4 3	2397
	11th to 20th	Night	65% 7% 9% 11% 7% 1	2274
	21st to end	Night	62% 4 11% 14% 6% 2	1917
March	1st to 10th	Night	65% 6% 12% 12% 5%	2093
	11th to 20th	Night	70% 4 8% 12% 6% 1	1980
	21st to end	Night	70% 6% 12% 10% 2	2129
April	1st to 10th	Night	65% 5% 15% 13% 3	1800
	11th to 20th	Night	60% 6% 11% 15% 6% 2	1677
	21st to end	Night	61% 5% 13% 13% 8%	1571
May	1st to 10th	Night	45% 10% 18% 18% 8% 1	1440
	11th to 20th	Night	47% 8% 21% 18% 6% 1	1416
	21st to end	Night	50% 7% 20% 18% 5%	1479
June	1st to 10th	Night	54% 5% 18% 15% 4 3	1260
	11th to 20th	Night	53% 9% 20% 14% 4	1260
	21st to end	Night	42% 9% 21% 17% 8% 3	1260
July	1st to 10th	Night	35% 6% 17% 26% 13% 3	1225
	11th to 20th	Night	28% 7% 23% 29% 13% 1	1218
	21st to end	Night	20% 6% 15% 34% 19% 5%	1422
August	1st to 10th	Night	27% 5% 20% 28% 18% 3	1445
	11th to 20th	Night	21% 8% 25% 26% 14% 6%	1602
	21st to end	Night	37% 5% 21% 27% 9% 1	1830
September	1st to 10th	Night	31% 7% 17% 27% 14% 4	1800
	11th to 20th	Night	44% 7% 12% 16% 16% 5%	1808
	21st to end	Night	50% 5% 15% 20% 8% 2	2060
October	1st to 10th	Night	49% 6% 14% 19% 11% 1	2160
	11th to 20th	Night	59% 4 13% 17% 6%	2160
	21st to end	Night	61% 6% 10% 14% 9%	2528
November	1st to 10th	Night	73% 4 9% 9% 4 1	2590
	11th to 20th	Night	69% 4 9% 10% 6% 2	2660
	21st to end	Night	70% 3 9% 9% 8% 1	2660
December	1st to 10th	Night	65% 5% 11% 11% 7% 1	2698
	11th to 20th	Night	78% 4 7% 6% 4 1	3516
	21st to end	Night	77% 3 6% 9% 4 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	44% 7% 9% 19% 12% 8%	180
	11th to 20th	Day	45% 8% 14% 12% 16% 5%	180
	21st to end	Day	49% 4 12% 18% 15% 4	224
February	1st to 10th	Day	41% 6% 15% 22% 14% 2	353
	11th to 20th	Day	38% 2 20% 22% 16% 2	335
	21st to end	Day	27% 8% 17% 30% 13% 5%	284
March	1st to 10th	Day	33% 5% 15% 27% 15% 5%	420
	11th to 20th	Day	34% 5% 17% 21% 19% 5%	420
	21st to end	Day	34% 8% 16% 24% 14% 4	462
April	1st to 10th	Day	30% 6% 22% 20% 19% 3	420
	11th to 20th	Day	28% 5% 17% 23% 20% 7%	412
	21st to end	Day	23% 5% 24% 25% 19% 4	420
May	1st to 10th	Day	16% 5% 19% 29% 27% 4	423
	11th to 20th	Day	16% 4 13% 26% 32% 9%	448
	21st to end	Day	15% 5% 16% 34% 22% 9%	555
June	1st to 10th	Day	19% 3 17% 31% 26% 4	630
	11th to 20th	Day	18% 4 22% 28% 24% 4	630
	21st to end	Day	15% 2 15% 33% 29% 6%	630
July	1st to 10th	Day	13% 1 14% 31% 33% 9%	621
	11th to 20th	Day	8% 2 15% 32% 37% 7%	618
	21st to end	Day	5% 1 10% 29% 43% 12%	555
August	1st to 10th	Day	11% 2 10% 23% 38% 15%	447
	11th to 20th	Day	8% 2 9% 31% 38% 12%	437
	21st to end	Day	11% 2 17% 33% 27% 10%	495
September	1st to 10th	Day	16% 2 17% 34% 25% 7%	450
	11th to 20th	Day	21% 4 15% 25% 26% 10%	450
	21st to end	Day	25% 3 16% 24% 25% 7%	450
October	1st to 10th	Day	28% 4 14% 26% 20% 9%	450
	11th to 20th	Day	37% 4 14% 18% 18% 9%	450
	21st to end	Day	36% 9% 14% 21% 14% 5%	365
November	1st to 10th	Day	37% 7% 18% 19% 14% 4	180
	11th to 20th	Day	42% 4 12% 14% 17% 11%	180
	21st to end	Day	42% 7% 14% 14% 11% 11%	180
December	1st to 10th	Day	48% 4 16% 8% 13% 11%	180
	11th to 20th	Day	40% 8% 12% 20% 16% 3	180
	21st to end	Day	44% 6% 13% 24% 10% 3	198
January	1st to 10th	Night	49% 6% 13% 17% 11% 4	850
	11th to 20th	Night	43% 5% 11% 20% 18% 2	850
	21st to end	Night	42% 4 14% 23% 14% 3	852
February	1st to 10th	Night	38% 5% 17% 24% 14% 2	738
	11th to 20th	Night	36% 4 16% 27% 15% 2	704
	21st to end	Night	32% 5% 18% 24% 17% 4	592
March	1st to 10th	Night	34% 6% 16% 20% 20% 3	720
	11th to 20th	Night	38% 4 15% 23% 15% 4	720
	21st to end	Night	36% 4 16% 22% 16% 6%	792
April	1st to 10th	Night	33% 5% 13% 27% 19% 5%	720
	11th to 20th	Night	26% 5% 17% 29% 19% 4	609
	21st to end	Night	27% 4 15% 32% 18% 5%	491
May	1st to 10th	Night	19% 2 13% 31% 29% 6%	360
	11th to 20th	Night	20% 2 9% 25% 34% 10%	354
	21st to end	Night	20% 3 10% 29% 32% 6%	389
June	1st to 10th	Night	23% 5% 8% 29% 31% 5%	360
	11th to 20th	Night	18% 4 16% 31% 25% 6%	360
	21st to end	Night	14% 3 9% 30% 39% 6%	360
July	1st to 10th	Night	13% 1 9% 26% 42% 9%	350
	11th to 20th	Night	9% 2 7% 27% 45% 10%	348
	21st to end	Night	6% 1 6% 23% 49% 16%	394
August	1st to 10th	Night	9% 1 6% 20% 44% 20%	379
	11th to 20th	Night	7% 3 21% 51% 16%	534
	21st to end	Night	14% 2 9% 23% 41% 11%	642
September	1st to 10th	Night	11% 2 7% 32% 37% 11%	720
	11th to 20th	Night	21% 3 9% 19% 32% 16%	720
	21st to end	Night	25% 3 11% 25% 29% 7%	720
October	1st to 10th	Night	23% 3 13% 25% 27% 9%	720
	11th to 20th	Night	36% 3 12% 23% 21% 6%	720
	21st to end	Night	39% 3 13% 26% 14% 5%	792
November	1st to 10th	Night	42% 6% 13% 23% 15% 1	740
	11th to 20th	Night	41% 5% 14% 22% 13% 4	760
	21st to end	Night	42% 4 15% 19% 16% 4	760
December	1st to 10th	Night	36% 4 15% 25% 16% 4	778
	11th to 20th	Night	52% 4 13% 22% 8% 1	850
	21st to end	Night	47% 7% 17% 18% 9% 1	935

Page generated at 2024-02-02 02:20:32. Version ac07

Copyright 2024 Attilla Danko