Port Coquitlam
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Coquitlam clear sky chart from 2005-11-06 to 2024-04-03.

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	30% 10% 3 6% 5% 3 4 3 4 5% 28%	78401
	Night	33% 10% 3 5% 4 2 3 3 4 5% 27%	81679
Transparency	Day	60% 6% 12% 15% 6% 1	78111
	Night	61% 6% 12% 13% 7% 2	81549
Seeing	Day	31% 7% 20% 24% 13% 4	14441
	Night	36% 4 16% 25% 17% 2	22884

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	47% 13% 4 6% 5% 3 3 3 3 4 10%	2219
	11th to 20th	Day	32% 12% 5% 7% 4 2 3 2 2 4 28%	2199
	21st to end	Day	61% 9% 3 4 3 1 2 2 2 2 11%	2802
February	1st to 10th	Day	37% 12% 4 8% 5% 3 3 3 3 5% 17%	1710
	11th to 20th	Day	34% 12% 3 6% 6% 2 4 3 3 5% 22%	1665
	21st to end	Day	28% 16% 4 7% 6% 4 4 3 3 4 20%	1437
March	1st to 10th	Day	33% 15% 4 7% 5% 3 4 3 3 5% 17%	1950
	11th to 20th	Day	39% 13% 4 5% 5% 2 3 3 3 3 19%	2090
	21st to end	Day	34% 13% 4 8% 6% 3 4 4 3 4 17%	2365
April	1st to 10th	Day	33% 11% 4 7% 6% 4 5% 5% 5% 5% 15%	2185
	11th to 20th	Day	28% 12% 4 8% 7% 3 6% 3 5% 5% 20%	2209
	21st to end	Day	29% 12% 4 7% 6% 3 5% 4 5% 5% 21%	2402
May	1st to 10th	Day	23% 10% 4 6% 6% 3 5% 4 5% 5% 29%	2520
	11th to 20th	Day	22% 10% 3 6% 6% 3 5% 5% 5% 8% 28%	2477
	21st to end	Day	25% 9% 4 8% 6% 3 4 4 4 5% 27%	2760
June	1st to 10th	Day	29% 9% 3 7% 6% 3 4 4 4 6% 25%	2700
	11th to 20th	Day	31% 10% 4 7% 7% 4 5% 4 4 5% 19%	2700
	21st to end	Day	21% 8% 3 6% 6% 3 4 4 5% 6% 33%	2700
July	1st to 10th	Day	17% 5% 2 6% 5% 3 3 4 5% 6% 45%	2700
	11th to 20th	Day	15% 6% 3 5% 4 3 4 4 4 5% 48%	2700
	21st to end	Day	11% 4 2 4 3 2 3 3 4 6% 57%	2780
August	1st to 10th	Day	14% 6% 3 4 4 2 3 4 4 5% 51%	2503
	11th to 20th	Day	12% 5% 2 4 4 2 4 4 4 6% 53%	2298
	21st to end	Day	17% 7% 2 5% 5% 3 4 4 5% 7% 40%	2511
September	1st to 10th	Day	19% 7% 2 5% 4 3 3 3 4 6% 43%	2160
	11th to 20th	Day	22% 7% 3 7% 6% 2 3 3 3 4 39%	2160
	21st to end	Day	30% 6% 2 5% 4 3 4 3 4 5% 34%	1897
October	1st to 10th	Day	28% 9% 2 5% 3 2 3 4 4 5% 34%	1800
	11th to 20th	Day	36% 8% 3 6% 4 3 4 4 4 5% 24%	1800
	21st to end	Day	40% 10% 2 5% 3 2 3 3 4 5% 23%	1831
November	1st to 10th	Day	45% 10% 3 7% 5% 3 3 3 3 3 16%	1488
	11th to 20th	Day	45% 11% 4 4 4 2 2 2 2 3 21%	1520
	21st to end	Day	44% 10% 3 5% 3 2 3 4 3 4 19%	1520
December	1st to 10th	Day	35% 13% 4 6% 4 2 3 3 3 4 24%	1516
	11th to 20th	Day	43% 14% 3 6% 4 2 3 2 3 4 14%	1685
	21st to end	Day	47% 15% 4 6% 4 2 3 3 3 3 9%	2442
January	1st to 10th	Night	44% 14% 4 6% 5% 2 3 2 2 3 13%	4726
	11th to 20th	Night	34% 8% 2 4 4 2 3 4 4 6% 27%	4699
	21st to end	Night	58% 11% 3 4 3 1 2 2 2 3 12%	4850
February	1st to 10th	Night	37% 12% 3 5% 5% 3 4 4 3 5% 19%	2470
	11th to 20th	Night	31% 14% 3 6% 5% 3 3 3 3 4 24%	2402
	21st to end	Night	32% 11% 3 5% 5% 2 3 3 5% 5% 24%	2017
March	1st to 10th	Night	34% 14% 2 5% 4 3 4 3 4 4 22%	2228
	11th to 20th	Night	37% 12% 3 6% 4 3 3 4 3 4 21%	2089
	21st to end	Night	35% 13% 4 6% 5% 3 4 4 3 4 18%	2232
April	1st to 10th	Night	31% 12% 4 6% 5% 4 3 4 4 6% 21%	1820
	11th to 20th	Night	25% 11% 4 7% 6% 4 4 4 4 6% 25%	1699
	21st to end	Night	28% 11% 4 6% 6% 3 5% 3 4 6% 25%	1558
May	1st to 10th	Night	20% 7% 3 6% 5% 3 4 5% 6% 5% 37%	1440
	11th to 20th	Night	19% 7% 2 5% 6% 2 5% 6% 7% 8% 33%	1416
	21st to end	Night	20% 7% 4 7% 5% 3 4 4 5% 6% 35%	1512
June	1st to 10th	Night	25% 7% 3 7% 6% 3 4 4 5% 6% 30%	1260
	11th to 20th	Night	21% 12% 4 6% 6% 4 5% 4 6% 7% 26%	1260
	21st to end	Night	16% 7% 3 5% 5% 2 4 5% 6% 7% 40%	1260
July	1st to 10th	Night	12% 5% 3 4 6% 2 4 3 4 6% 51%	1260
	11th to 20th	Night	11% 3 1 5% 3 2 3 4 5% 6% 57%	1260
	21st to end	Night	6% 2 1 4 3 2 4 3 5% 5% 65%	1536
August	1st to 10th	Night	10% 5% 2 3 3 2 2 3 4 6% 61%	1435
	11th to 20th	Night	8% 3 2 2 2 2 3 3 5% 6% 63%	1602
	21st to end	Night	12% 6% 2 6% 5% 3 4 4 7% 8% 44%	1844
September	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 4 5% 53%	1800
	11th to 20th	Night	23% 5% 3 5% 4 2 4 3 4 5% 42%	1800
	21st to end	Night	27% 7% 3 5% 5% 2 3 3 3 6% 37%	2060
October	1st to 10th	Night	24% 8% 3 5% 5% 3 4 4 4 4 38%	2160
	11th to 20th	Night	35% 8% 3 5% 4 3 3 3 5% 4 27%	2160
	21st to end	Night	38% 8% 3 5% 4 3 3 3 3 5% 26%	2520
November	1st to 10th	Night	45% 10% 3 6% 5% 3 3 3 3 4 17%	2590
	11th to 20th	Night	42% 10% 3 5% 4 2 3 3 3 4 22%	2660
	21st to end	Night	41% 10% 3 6% 5% 2 3 3 3 3 21%	2660
December	1st to 10th	Night	35% 10% 3 5% 4 2 4 3 3 5% 25%	2660
	11th to 20th	Night	48% 14% 3 5% 4 2 3 3 2 3 13%	3520
	21st to end	Night	50% 13% 3 5% 4 2 2 2 2 3 13%	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% 6% 8% 5% 2 1	2219
	11th to 20th	Day	65% 4 12% 11% 4 4	2220
	21st to end	Day	82% 3 4 7% 2	2802
February	1st to 10th	Day	71% 6% 10% 8% 4 2	1710
	11th to 20th	Day	67% 5% 9% 11% 6% 1	1674
	21st to end	Day	69% 5% 10% 11% 3 2	1437
March	1st to 10th	Day	71% 6% 10% 9% 3	1950
	11th to 20th	Day	71% 4 8% 12% 4 1	2090
	21st to end	Day	72% 6% 10% 10% 2	2365
April	1st to 10th	Day	71% 7% 12% 8% 3	2185
	11th to 20th	Day	66% 6% 11% 10% 7% 1	2209
	21st to end	Day	65% 7% 11% 10% 6%	2402
May	1st to 10th	Day	56% 7% 15% 16% 5% 1	2520
	11th to 20th	Day	55% 8% 15% 17% 5%	2480
	21st to end	Day	60% 6% 15% 17% 3	2761
June	1st to 10th	Day	61% 5% 16% 11% 4 2	2700
	11th to 20th	Day	67% 7% 15% 9% 3	2700
	21st to end	Day	52% 7% 16% 15% 8% 1	2700
July	1st to 10th	Day	42% 7% 13% 23% 12% 3	2626
	11th to 20th	Day	38% 7% 18% 27% 10% 1	2619
	21st to end	Day	28% 6% 17% 31% 15% 3	2625
August	1st to 10th	Day	36% 7% 15% 28% 12% 2	2486
	11th to 20th	Day	31% 8% 19% 25% 15% 2	2298
	21st to end	Day	42% 7% 18% 26% 6% 1	2511
September	1st to 10th	Day	43% 7% 13% 23% 10% 4	2160
	11th to 20th	Day	50% 6% 10% 18% 14% 3	2160
	21st to end	Day	53% 6% 14% 15% 9% 2	1897
October	1st to 10th	Day	54% 5% 14% 16% 10%	1800
	11th to 20th	Day	63% 7% 12% 14% 4 1	1800
	21st to end	Day	65% 5% 11% 12% 6% 1	1831
November	1st to 10th	Day	74% 5% 8% 8% 4 1	1488
	11th to 20th	Day	71% 4 8% 9% 5% 2	1520
	21st to end	Day	70% 5% 6% 10% 8% 1	1520
December	1st to 10th	Day	66% 5% 8% 10% 9% 1	1516
	11th to 20th	Day	76% 5% 7% 8% 3 2	1688
	21st to end	Day	81% 5% 6% 6% 1 1	2442
January	1st to 10th	Night	77% 5% 6% 9% 2	4726
	11th to 20th	Night	58% 5% 14% 12% 7% 4	4740
	21st to end	Night	81% 3 5% 8% 2 1	4850
February	1st to 10th	Night	69% 6% 11% 8% 4 2	2470
	11th to 20th	Night	65% 7% 9% 10% 8% 1	2404
	21st to end	Night	62% 4 11% 13% 6% 3	2017
March	1st to 10th	Night	65% 5% 12% 12% 5%	2228
	11th to 20th	Night	68% 5% 9% 12% 6% 1	2090
	21st to end	Night	70% 6% 12% 9% 2	2232
April	1st to 10th	Night	65% 5% 15% 12% 3	1820
	11th to 20th	Night	61% 7% 11% 13% 7% 2	1699
	21st to end	Night	61% 8% 12% 12% 7% 1	1558
May	1st to 10th	Night	47% 9% 18% 18% 7% 1	1440
	11th to 20th	Night	48% 9% 19% 17% 6% 1	1416
	21st to end	Night	49% 10% 18% 17% 5%	1512
June	1st to 10th	Night	56% 7% 16% 14% 4 3	1260
	11th to 20th	Night	56% 10% 18% 13% 3	1260
	21st to end	Night	42% 9% 20% 17% 8% 3	1260
July	1st to 10th	Night	37% 7% 15% 24% 14% 4	1225
	11th to 20th	Night	30% 7% 21% 29% 12% 1	1218
	21st to end	Night	20% 7% 15% 34% 19% 5%	1451
August	1st to 10th	Night	26% 6% 19% 28% 18% 3	1427
	11th to 20th	Night	22% 7% 25% 27% 13% 7%	1602
	21st to end	Night	37% 7% 20% 26% 9% 1	1844
September	1st to 10th	Night	33% 8% 16% 24% 15% 4	1800
	11th to 20th	Night	47% 5% 11% 16% 16% 4	1800
	21st to end	Night	51% 6% 14% 18% 8% 2	2060
October	1st to 10th	Night	51% 5% 16% 18% 10% 1	2160
	11th to 20th	Night	60% 6% 12% 16% 6% 1	2160
	21st to end	Night	63% 5% 10% 14% 8%	2520
November	1st to 10th	Night	73% 4 9% 9% 4 1	2590
	11th to 20th	Night	69% 5% 8% 9% 6% 2	2660
	21st to end	Night	69% 5% 8% 8% 9% 1	2660
December	1st to 10th	Night	65% 6% 9% 12% 8% 1	2660
	11th to 20th	Night	78% 5% 6% 5% 4 1	3516
	21st to end	Night	78% 4 6% 8% 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	51% 4 16% 14% 9% 6%	180
	11th to 20th	Day	54% 10% 10% 13% 11% 2	180
	21st to end	Day	54% 4 13% 15% 13% 1	207
February	1st to 10th	Day	46% 6% 20% 18% 8% 1	370
	11th to 20th	Day	42% 6% 21% 22% 7% 2	365
	21st to end	Day	37% 12% 25% 18% 7% 2	319
March	1st to 10th	Day	41% 7% 22% 20% 9% 2	460
	11th to 20th	Day	40% 7% 15% 20% 16% 2	460
	21st to end	Day	43% 9% 21% 17% 8% 2	506
April	1st to 10th	Day	39% 10% 20% 20% 10% 1	429
	11th to 20th	Day	34% 10% 21% 20% 12% 4	412
	21st to end	Day	32% 11% 25% 21% 9% 2	420
May	1st to 10th	Day	25% 9% 22% 30% 11% 2	423
	11th to 20th	Day	29% 5% 19% 25% 18% 5%	448
	21st to end	Day	23% 7% 29% 25% 11% 6%	522
June	1st to 10th	Day	29% 7% 25% 26% 11% 2	630
	11th to 20th	Day	31% 12% 25% 23% 9% 1	630
	21st to end	Day	23% 7% 23% 27% 18% 3	630
July	1st to 10th	Day	19% 4 24% 34% 16% 3	621
	11th to 20th	Day	15% 8% 23% 35% 16% 3	618
	21st to end	Day	11% 3 18% 40% 20% 7%	526
August	1st to 10th	Day	17% 6% 17% 32% 21% 7%	447
	11th to 20th	Day	13% 2 21% 34% 24% 7%	437
	21st to end	Day	20% 8% 23% 28% 16% 6%	495
September	1st to 10th	Day	23% 6% 25% 29% 13% 4	450
	11th to 20th	Day	26% 5% 19% 29% 18% 3	450
	21st to end	Day	30% 8% 16% 25% 16% 5%	450
October	1st to 10th	Day	32% 5% 20% 21% 18% 4	450
	11th to 20th	Day	41% 7% 12% 20% 16% 5%	450
	21st to end	Day	43% 8% 17% 18% 9% 4	358
November	1st to 10th	Day	45% 8% 17% 19% 11% 1	180
	11th to 20th	Day	49% 6% 10% 12% 14% 9%	180
	21st to end	Day	48% 8% 16% 11% 6% 11%	180
December	1st to 10th	Day	51% 7% 12% 9% 14% 8%	180
	11th to 20th	Day	52% 5% 14% 17% 8% 3	180
	21st to end	Day	51% 5% 14% 23% 7% 1	198
January	1st to 10th	Night	54% 5% 15% 18% 7% 1	850
	11th to 20th	Night	47% 4 15% 24% 10%	850
	21st to end	Night	47% 5% 16% 21% 10%	836
February	1st to 10th	Night	43% 4 22% 23% 7% 1	760
	11th to 20th	Night	39% 7% 20% 24% 10%	744
	21st to end	Night	37% 8% 21% 23% 11%	628
March	1st to 10th	Night	41% 7% 17% 21% 14% 1	760
	11th to 20th	Night	43% 6% 16% 23% 12% 1	760
	21st to end	Night	44% 5% 16% 21% 12% 2	836
April	1st to 10th	Night	37% 5% 18% 27% 13% 2	728
	11th to 20th	Night	31% 6% 22% 27% 12% 2	631
	21st to end	Night	36% 3 18% 29% 11% 2	478
May	1st to 10th	Night	22% 2 20% 32% 23% 1	360
	11th to 20th	Night	21% 5% 7% 35% 28% 4	354
	21st to end	Night	23% 2 12% 35% 26% 1	389
June	1st to 10th	Night	29% 3 10% 34% 21% 3	360
	11th to 20th	Night	26% 4 18% 28% 21% 3	360
	21st to end	Night	18% 4 15% 30% 31% 3	360
July	1st to 10th	Night	13% 3 10% 33% 39% 2	350
	11th to 20th	Night	12% 2 8% 32% 40% 6%	348
	21st to end	Night	7% 1 8% 28% 50% 6%	394
August	1st to 10th	Night	12% 2 5% 24% 47% 10%	361
	11th to 20th	Night	9% 1 5% 28% 46% 10%	534
	21st to end	Night	17% 2 12% 29% 37% 4	656
September	1st to 10th	Night	14% 1 12% 38% 32% 3	720
	11th to 20th	Night	25% 2 11% 25% 31% 6%	720
	21st to end	Night	32% 2 13% 29% 22% 2	720
October	1st to 10th	Night	30% 3 13% 27% 23% 3	720
	11th to 20th	Night	41% 3 14% 25% 14% 2	720
	21st to end	Night	42% 3 19% 25% 10% 2	792
November	1st to 10th	Night	49% 5% 18% 22% 5%	740
	11th to 20th	Night	49% 5% 18% 17% 10% 1	760
	21st to end	Night	46% 6% 18% 18% 10% 2	760
December	1st to 10th	Night	41% 4 18% 25% 11% 1	760
	11th to 20th	Night	55% 6% 16% 18% 4 1	850
	21st to end	Night	52% 7% 19% 18% 3	935

Page generated at 2024-03-31 03:08:54. Version ac07

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