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 2024-11-04.

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% 10% 3 6% 4 4 4 3 4 5% 30%	105501
	Night	31% 11% 3 6% 4 3 3 3 4 5% 29%	102117
Transparency	Day	56% 6% 13% 16% 7% 1	105250
	Night	58% 6% 12% 15% 7% 1	102014
Seeing	Day	31% 7% 20% 24% 13% 4	15340
	Night	36% 4 16% 25% 17% 2	23507

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% 14% 3 7% 5% 3 3 3 3 4 10%	2219
	11th to 20th	Day	31% 13% 5% 7% 3 3 2 2 2 4 27%	2199
	21st to end	Day	60% 10% 2 5% 3 2 2 2 2 2 11%	2802
February	1st to 10th	Day	37% 13% 3 9% 4 4 3 3 4 4 17%	1710
	11th to 20th	Day	34% 13% 3 7% 4 3 4 2 4 5% 21%	1665
	21st to end	Day	27% 18% 4 8% 5% 5% 3 2 3 4 20%	1437
March	1st to 10th	Day	29% 21% 4 8% 4 4 4 3 3 5% 14%	3224
	11th to 20th	Day	27% 12% 3 6% 4 3 3 2 3 4 32%	3490
	21st to end	Day	32% 14% 4 8% 4 4 3 3 3 5% 19%	3938
April	1st to 10th	Day	33% 13% 3 8% 6% 5% 5% 4 5% 5% 14%	2280
	11th to 20th	Day	27% 13% 3 8% 6% 4 5% 3 4 5% 21%	2334
	21st to end	Day	30% 12% 4 7% 4 5% 4 3 4 5% 20%	2536
May	1st to 10th	Day	20% 11% 3 6% 4 4 4 4 4 5% 35%	4420
	11th to 20th	Day	18% 8% 2 7% 4 5% 5% 4 7% 8% 32%	4377
	21st to end	Day	33% 11% 3 8% 5% 5% 4 3 4 5% 18%	4892
June	1st to 10th	Day	29% 9% 3 8% 5% 4 4 3 4 6% 25%	2850
	11th to 20th	Day	30% 11% 4 8% 6% 5% 5% 3 4 5% 20%	2850
	21st to end	Day	21% 9% 3 7% 5% 5% 4 3 5% 6% 32%	2850
July	1st to 10th	Day	10% 4 2 5% 3 3 3 3 4 5% 59%	4740
	11th to 20th	Day	8% 4 1 3 2 2 3 2 3 4 67%	4740
	21st to end	Day	16% 5% 2 5% 3 3 3 2 6% 7% 49%	4857
August	1st to 10th	Day	8% 4 2 4 2 2 2 2 4 6% 64%	4384
	11th to 20th	Day	20% 7% 2 6% 4 4 4 3 5% 6% 38%	4026
	21st to end	Day	23% 6% 2 6% 4 4 4 3 4 7% 37%	4406
September	1st to 10th	Day	19% 7% 2 6% 3 4 3 2 4 6% 43%	2280
	11th to 20th	Day	22% 8% 3 8% 5% 3 4 3 4 4 37%	2280
	21st to end	Day	30% 7% 2 6% 4 4 3 3 4 5% 33%	2001
October	1st to 10th	Day	29% 9% 3 7% 4 4 4 3 5% 6% 26%	3180
	11th to 20th	Day	41% 7% 2 6% 4 4 4 3 4 4 21%	3161
	21st to end	Day	38% 14% 4 8% 3 4 3 3 5% 4 14%	3178
November	1st to 10th	Day	45% 10% 3 8% 4 4 4 2 3 3 15%	1512
	11th to 20th	Day	44% 11% 3 5% 3 2 2 2 3 3 21%	1520
	21st to end	Day	43% 11% 2 5% 3 3 2 4 4 4 19%	1520
December	1st to 10th	Day	34% 15% 3 6% 3 3 3 2 3 4 24%	1516
	11th to 20th	Day	43% 14% 4 7% 4 3 2 2 4 3 14%	1685
	21st to end	Day	47% 16% 4 7% 4 3 3 2 3 3 9%	2442
January	1st to 10th	Night	44% 15% 4 7% 4 3 3 2 3 3 13%	4726
	11th to 20th	Night	34% 9% 2 5% 3 3 3 3 4 6% 27%	4699
	21st to end	Night	58% 11% 2 4 2 2 2 1 2 3 12%	4850
February	1st to 10th	Night	37% 13% 3 6% 5% 4 3 3 4 5% 19%	2470
	11th to 20th	Night	31% 15% 3 7% 5% 3 3 3 3 4 24%	2402
	21st to end	Night	31% 13% 2 6% 4 2 3 3 5% 5% 24%	2017
March	1st to 10th	Night	30% 21% 3 5% 3 4 3 2 3 4 22%	3648
	11th to 20th	Night	28% 10% 2 6% 3 3 3 3 4 5% 34%	3489
	21st to end	Night	36% 14% 4 7% 4 3 3 3 3 3 20%	3714
April	1st to 10th	Night	30% 13% 3 8% 5% 5% 3 3 5% 5% 20%	1900
	11th to 20th	Night	24% 12% 4 8% 5% 4 4 3 5% 6% 26%	1794
	21st to end	Night	28% 11% 4 7% 6% 5% 4 3 5% 6% 24%	1644
May	1st to 10th	Night	19% 9% 2 6% 4 3 3 3 4 3 44%	2540
	11th to 20th	Night	13% 7% 2 6% 4 3 3 4 6% 8% 43%	2516
	21st to end	Night	29% 11% 3 7% 5% 4 3 2 4 4 26%	2680
June	1st to 10th	Night	26% 8% 2 8% 5% 4 4 3 5% 5% 29%	1330
	11th to 20th	Night	21% 13% 3 7% 5% 5% 3 4 6% 7% 26%	1330
	21st to end	Night	17% 8% 2 6% 5% 4 4 4 6% 6% 38%	1330
July	1st to 10th	Night	7% 3 2 3 4 2 3 2 4 6% 65%	2220
	11th to 20th	Night	6% 2 1 3 2 2 2 2 3 4 74%	2220
	21st to end	Night	12% 4 1 4 3 3 3 3 5% 6% 56%	2694
August	1st to 10th	Night	5% 3 1 2 2 2 2 3 5% 7% 69%	2546
	11th to 20th	Night	13% 6% 3 6% 3 4 3 3 5% 6% 48%	2812
	21st to end	Night	18% 6% 2 6% 4 3 4 3 5% 7% 41%	3264
September	1st to 10th	Night	12% 4 2 6% 3 4 3 3 5% 5% 53%	1900
	11th to 20th	Night	23% 6% 2 5% 4 3 4 2 4 5% 41%	1900
	21st to end	Night	27% 7% 3 6% 4 3 3 3 3 6% 36%	2176
October	1st to 10th	Night	26% 12% 3 7% 5% 4 4 3 4 5% 27%	3800
	11th to 20th	Night	38% 8% 2 5% 3 3 3 3 5% 5% 25%	3777
	21st to end	Night	39% 13% 3 7% 3 3 3 2 3 4 21%	4377
November	1st to 10th	Night	44% 11% 3 7% 4 3 3 2 3 4 17%	2638
	11th to 20th	Night	42% 10% 2 5% 4 2 3 2 3 3 22%	2660
	21st to end	Night	40% 11% 3 6% 4 3 3 2 3 3 21%	2660
December	1st to 10th	Night	34% 12% 3 6% 4 4 3 2 3 4 25%	2660
	11th to 20th	Night	48% 15% 3 5% 3 3 3 2 3 3 13%	3520
	21st to end	Night	49% 13% 3 6% 3 2 3 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% 7% 10% 8% 3	3224
	11th to 20th	Day	56% 6% 11% 23% 3 1	3490
	21st to end	Day	68% 6% 13% 9% 3	3938
April	1st to 10th	Day	71% 7% 11% 8% 3	2280
	11th to 20th	Day	64% 6% 11% 11% 7% 2	2334
	21st to end	Day	65% 7% 11% 11% 6%	2536
May	1st to 10th	Day	49% 5% 17% 21% 7%	4420
	11th to 20th	Day	46% 9% 23% 18% 4	4380
	21st to end	Day	65% 8% 15% 10% 1	4893
June	1st to 10th	Day	60% 6% 16% 12% 4 2	2850
	11th to 20th	Day	66% 7% 15% 9% 3	2850
	21st to end	Day	52% 7% 16% 15% 8% 1	2850
July	1st to 10th	Day	28% 7% 10% 25% 22% 8%	4666
	11th to 20th	Day	22% 4 14% 41% 18% 1	4659
	21st to end	Day	34% 7% 22% 24% 11% 2	4703
August	1st to 10th	Day	23% 5% 12% 43% 15% 1	4367
	11th to 20th	Day	45% 8% 20% 17% 8% 1	4065
	21st to end	Day	46% 7% 17% 20% 9% 1	4405
September	1st to 10th	Day	43% 7% 13% 22% 11% 4	2280
	11th to 20th	Day	50% 6% 10% 17% 13% 2	2280
	21st to end	Day	54% 6% 15% 15% 9% 1	2001
October	1st to 10th	Day	59% 5% 15% 14% 6%	3180
	11th to 20th	Day	65% 7% 12% 11% 6%	3161
	21st to end	Day	71% 6% 9% 9% 4 1	3178
November	1st to 10th	Day	74% 5% 8% 8% 4 1	1512
	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	66% 5% 10% 12% 7%	3648
	11th to 20th	Night	54% 6% 13% 22% 5%	3490
	21st to end	Night	70% 6% 11% 10% 2	3714
April	1st to 10th	Night	66% 6% 14% 12% 3	1900
	11th to 20th	Night	59% 7% 11% 14% 7% 3	1794
	21st to end	Night	62% 7% 12% 12% 7% 1	1644
May	1st to 10th	Night	44% 6% 16% 24% 10% 1	2540
	11th to 20th	Night	38% 10% 26% 20% 6%	2516
	21st to end	Night	60% 8% 17% 11% 3	2680
June	1st to 10th	Night	56% 7% 16% 14% 4 3	1330
	11th to 20th	Night	56% 9% 18% 13% 4	1330
	21st to end	Night	44% 9% 20% 16% 8% 3	1330
July	1st to 10th	Night	22% 5% 12% 32% 21% 7%	2185
	11th to 20th	Night	17% 4 13% 44% 21% 1	2178
	21st to end	Night	28% 7% 17% 29% 17% 3	2609
August	1st to 10th	Night	16% 4 17% 38% 23% 2	2538
	11th to 20th	Night	36% 7% 28% 18% 8% 4	2839
	21st to end	Night	43% 7% 20% 20% 9% 1	3264
September	1st to 10th	Night	33% 8% 17% 23% 14% 5%	1900
	11th to 20th	Night	47% 5% 12% 16% 15% 4	1900
	21st to end	Night	52% 6% 14% 18% 8% 2	2176
October	1st to 10th	Night	59% 5% 17% 12% 6%	3800
	11th to 20th	Night	62% 5% 10% 15% 7%	3777
	21st to end	Night	69% 4 8% 13% 5%	4377
November	1st to 10th	Night	74% 4 8% 9% 4 1	2638
	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% 18% 8% 2	506
April	1st to 10th	Day	38% 11% 20% 20% 10% 1	460
	11th to 20th	Day	32% 10% 22% 21% 11% 4	452
	21st to end	Day	33% 10% 26% 20% 9% 2	460
May	1st to 10th	Day	25% 9% 22% 29% 12% 3	463
	11th to 20th	Day	27% 6% 20% 25% 17% 5%	488
	21st to end	Day	25% 8% 28% 23% 10% 5%	569
June	1st to 10th	Day	29% 7% 25% 27% 10% 2	680
	11th to 20th	Day	30% 12% 26% 22% 9% 1	680
	21st to end	Day	23% 7% 23% 27% 17% 3	680
July	1st to 10th	Day	18% 4 25% 34% 15% 3	671
	11th to 20th	Day	14% 7% 22% 38% 16% 4	668
	21st to end	Day	13% 5% 19% 39% 18% 6%	572
August	1st to 10th	Day	16% 6% 17% 33% 20% 8%	487
	11th to 20th	Day	14% 2 21% 34% 23% 7%	477
	21st to end	Day	20% 8% 22% 27% 16% 6%	539
September	1st to 10th	Day	22% 6% 23% 29% 15% 5%	490
	11th to 20th	Day	26% 7% 19% 28% 17% 3	490
	21st to end	Day	31% 8% 16% 24% 16% 5%	490
October	1st to 10th	Day	32% 5% 20% 21% 18% 4	490
	11th to 20th	Day	42% 7% 13% 20% 15% 4	490
	21st to end	Day	44% 8% 18% 19% 9% 4	393
November	1st to 10th	Day	46% 8% 17% 18% 10% 1	186
	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	36% 5% 19% 27% 12% 2	760
	11th to 20th	Night	30% 6% 22% 27% 12% 2	666
	21st to end	Night	36% 4 19% 29% 10% 2	504
May	1st to 10th	Night	22% 2 20% 32% 23% 1	380
	11th to 20th	Night	20% 5% 8% 35% 28% 4	374
	21st to end	Night	24% 2 13% 35% 25% 1	411
June	1st to 10th	Night	29% 4 11% 34% 20% 2	380
	11th to 20th	Night	27% 5% 18% 28% 21% 2	380
	21st to end	Night	19% 4 15% 29% 30% 3	380
July	1st to 10th	Night	12% 3 11% 35% 38% 2	370
	11th to 20th	Night	11% 2 8% 32% 41% 6%	368
	21st to end	Night	8% 1 8% 29% 49% 6%	416
August	1st to 10th	Night	12% 2 4 25% 48% 9%	382
	11th to 20th	Night	9% 1 6% 28% 45% 11%	564
	21st to end	Night	17% 2 12% 28% 36% 4	693
September	1st to 10th	Night	14% 1 12% 37% 33% 3	760
	11th to 20th	Night	25% 3 12% 25% 31% 5%	760
	21st to end	Night	33% 3 13% 29% 21% 2	760
October	1st to 10th	Night	30% 4 14% 27% 22% 3	760
	11th to 20th	Night	41% 3 14% 26% 14% 2	760
	21st to end	Night	43% 3 19% 24% 9% 2	836
November	1st to 10th	Night	50% 6% 18% 21% 5%	754
	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 2024-11-01 19:47:48. Version ac07

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