Pitt Meadows
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pitt Meadows clear sky chart from 2005-11-06 to 2024-09-14.

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	25% 9% 3 6% 4 4 4 3 4 5% 33%	101174
	Night	29% 9% 3 6% 4 3 3 3 4 5% 31%	96802
Transparency	Day	52% 8% 14% 16% 8% 1	100924
	Night	56% 7% 13% 15% 8% 2	96698
Seeing	Day	32% 11% 21% 23% 10% 2	15138
	Night	37% 7% 18% 24% 13% 1	23302

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% 13% 3 7% 4 4 4 3 4 4 10%	2219
	11th to 20th	Day	31% 13% 4 7% 4 3 3 2 3 4 27%	2204
	21st to end	Day	58% 9% 2 6% 3 2 2 2 3 3 10%	2803
February	1st to 10th	Day	37% 10% 3 8% 5% 4 3 3 4 5% 17%	1710
	11th to 20th	Day	34% 10% 3 8% 5% 5% 4 2 4 5% 22%	1665
	21st to end	Day	27% 14% 4 8% 6% 4 5% 3 4 5% 20%	1440
March	1st to 10th	Day	29% 16% 4 8% 4 4 4 3 4 6% 17%	3221
	11th to 20th	Day	25% 10% 3 7% 4 3 3 3 4 6% 32%	3490
	21st to end	Day	29% 13% 4 8% 5% 4 4 3 4 5% 20%	3941
April	1st to 10th	Day	30% 10% 3 9% 5% 6% 4 4 6% 6% 18%	2280
	11th to 20th	Day	24% 10% 3 8% 6% 5% 5% 3 5% 5% 24%	2330
	21st to end	Day	26% 11% 4 8% 6% 4 4 4 5% 5% 23%	2537
May	1st to 10th	Day	19% 8% 2 6% 4 3 4 4 4 5% 40%	4420
	11th to 20th	Day	14% 7% 3 6% 5% 5% 5% 5% 6% 9% 35%	4377
	21st to end	Day	30% 10% 3 8% 4 4 4 4 5% 6% 21%	4871
June	1st to 10th	Day	25% 8% 3 7% 5% 5% 4 4 5% 6% 28%	2850
	11th to 20th	Day	24% 10% 3 8% 6% 5% 5% 4 5% 7% 22%	2850
	21st to end	Day	16% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	2850
July	1st to 10th	Day	9% 3 1 4 3 2 3 3 4 4 62%	4740
	11th to 20th	Day	7% 3 1 3 2 2 2 2 4 5% 68%	4740
	21st to end	Day	14% 5% 2 4 3 3 3 3 4 6% 53%	4836
August	1st to 10th	Day	7% 3 1 3 3 3 3 2 4 6% 66%	4384
	11th to 20th	Day	16% 6% 2 5% 3 4 4 4 5% 7% 43%	4026
	21st to end	Day	19% 7% 2 6% 4 3 4 4 5% 7% 40%	4402
September	1st to 10th	Day	16% 7% 3 6% 3 3 3 3 5% 6% 45%	2280
	11th to 20th	Day	20% 8% 3 7% 4 4 4 3 4 4 40%	2198
	21st to end	Day	27% 6% 2 6% 4 4 3 4 5% 5% 34%	1898
October	1st to 10th	Day	26% 8% 3 6% 4 3 4 3 5% 6% 33%	1800
	11th to 20th	Day	34% 9% 3 7% 4 3 3 3 4 6% 23%	1800
	21st to end	Day	39% 7% 3 6% 4 3 3 2 5% 6% 22%	1832
November	1st to 10th	Day	43% 8% 3 6% 6% 4 4 3 3 5% 16%	1488
	11th to 20th	Day	41% 11% 2 7% 3 3 4 2 3 3 21%	1520
	21st to end	Day	41% 11% 4 5% 3 3 3 4 5% 4 17%	1520
December	1st to 10th	Day	35% 13% 3 6% 4 3 3 3 3 4 23%	1520
	11th to 20th	Day	39% 14% 3 8% 4 5% 5% 3 4 4 11%	1690
	21st to end	Day	44% 14% 4 8% 4 3 3 2 3 3 10%	2442
January	1st to 10th	Night	43% 12% 4 7% 4 3 4 3 3 3 14%	4726
	11th to 20th	Night	34% 9% 2 5% 3 3 3 3 5% 7% 26%	4692
	21st to end	Night	55% 11% 3 5% 3 2 2 2 2 3 12%	4852
February	1st to 10th	Night	37% 12% 2 7% 4 4 3 3 4 5% 20%	2470
	11th to 20th	Night	30% 13% 3 8% 4 3 3 3 4 5% 24%	2402
	21st to end	Night	31% 12% 3 5% 4 3 3 3 5% 5% 26%	2013
March	1st to 10th	Night	30% 17% 3 6% 4 4 4 3 4 5% 21%	3649
	11th to 20th	Night	26% 8% 2 5% 4 4 3 3 4 6% 35%	3489
	21st to end	Night	35% 13% 4 8% 4 3 3 2 3 3 21%	3711
April	1st to 10th	Night	30% 10% 3 8% 5% 5% 4 4 4 6% 21%	1900
	11th to 20th	Night	22% 12% 3 8% 5% 4 4 3 5% 6% 28%	1797
	21st to end	Night	28% 9% 4 6% 5% 6% 5% 3 4 6% 24%	1642
May	1st to 10th	Night	19% 8% 2 5% 4 3 3 2 4 4 45%	2540
	11th to 20th	Night	13% 5% 2 6% 4 3 4 3 6% 7% 46%	2516
	21st to end	Night	28% 10% 3 7% 5% 4 4 3 4 5% 26%	2700
June	1st to 10th	Night	24% 8% 3 6% 5% 5% 5% 3 6% 5% 30%	1330
	11th to 20th	Night	18% 11% 4 9% 5% 5% 4 5% 6% 7% 27%	1330
	21st to end	Night	15% 8% 3 5% 5% 5% 4 4 6% 6% 42%	1330
July	1st to 10th	Night	6% 3 1 3 3 3 2 2 4 6% 67%	2220
	11th to 20th	Night	5% 2 1 2 2 2 2 2 3 4 75%	2220
	21st to end	Night	9% 5% 2 5% 3 4 4 3 4 5% 57%	2713
August	1st to 10th	Night	5% 3 1 2 1 1 2 3 5% 6% 70%	2544
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 4 8% 49%	2812
	21st to end	Night	15% 5% 2 6% 4 5% 5% 3 5% 8% 41%	3269
September	1st to 10th	Night	11% 4 2 5% 3 3 4 4 5% 6% 54%	1900
	11th to 20th	Night	21% 6% 3 6% 4 3 3 3 4 5% 42%	1840
	21st to end	Night	23% 6% 2 8% 4 4 4 2 4 5% 38%	2059
October	1st to 10th	Night	22% 8% 2 6% 4 4 5% 3 4 5% 38%	2160
	11th to 20th	Night	32% 8% 2 7% 4 3 3 3 4 5% 29%	2160
	21st to end	Night	35% 8% 2 6% 4 4 3 3 4 5% 27%	2519
November	1st to 10th	Night	41% 10% 2 7% 4 4 3 2 3 4 18%	2590
	11th to 20th	Night	39% 10% 3 6% 4 3 3 3 4 4 23%	2660
	21st to end	Night	39% 11% 3 7% 5% 4 4 3 3 3 19%	2660
December	1st to 10th	Night	33% 10% 2 6% 5% 4 3 3 3 4 25%	2660
	11th to 20th	Night	46% 14% 4 7% 5% 3 2 2 2 3 12%	3513
	21st to end	Night	44% 13% 4 7% 3 3 2 2 2 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	77% 8% 7% 6% 2 1	2219
	11th to 20th	Day	62% 7% 7% 13% 7% 4	2225
	21st to end	Day	81% 4 6% 6% 2	2803
February	1st to 10th	Day	71% 6% 9% 8% 4 2	1710
	11th to 20th	Day	66% 7% 9% 10% 7% 1	1674
	21st to end	Day	66% 8% 9% 10% 5% 2	1440
March	1st to 10th	Day	63% 11% 14% 9% 3	3221
	11th to 20th	Day	54% 8% 12% 24% 2 1	3490
	21st to end	Day	65% 9% 13% 10% 3	3941
April	1st to 10th	Day	67% 10% 13% 8% 2	2280
	11th to 20th	Day	62% 8% 10% 10% 7% 2	2330
	21st to end	Day	62% 9% 12% 10% 7% 1	2537
May	1st to 10th	Day	45% 10% 16% 21% 8%	4420
	11th to 20th	Day	42% 13% 24% 17% 4	4380
	21st to end	Day	62% 12% 16% 10% 1	4872
June	1st to 10th	Day	56% 8% 17% 12% 5% 2	2850
	11th to 20th	Day	61% 10% 15% 10% 3	2850
	21st to end	Day	49% 8% 17% 16% 8% 1	2850
July	1st to 10th	Day	26% 6% 11% 25% 23% 9%	4666
	11th to 20th	Day	20% 4 14% 38% 22% 2	4659
	21st to end	Day	31% 7% 22% 27% 11% 2	4683
August	1st to 10th	Day	21% 7% 14% 41% 16% 1	4367
	11th to 20th	Day	41% 8% 23% 19% 8% 1	4065
	21st to end	Day	44% 8% 18% 20% 10% 1	4401
September	1st to 10th	Day	40% 8% 15% 21% 11% 4	2280
	11th to 20th	Day	48% 8% 11% 17% 14% 2	2198
	21st to end	Day	50% 9% 15% 15% 10% 1	1898
October	1st to 10th	Day	51% 8% 15% 16% 10%	1800
	11th to 20th	Day	61% 8% 12% 14% 4 1	1800
	21st to end	Day	63% 7% 11% 10% 8% 1	1832
November	1st to 10th	Day	71% 7% 10% 8% 3 1	1488
	11th to 20th	Day	69% 6% 8% 8% 6% 2	1520
	21st to end	Day	69% 6% 8% 9% 7% 1	1520
December	1st to 10th	Day	65% 8% 6% 11% 9% 1	1520
	11th to 20th	Day	72% 7% 11% 6% 3 2	1693
	21st to end	Day	78% 8% 6% 6% 2 1	2442
January	1st to 10th	Night	76% 7% 7% 7% 2 1	4726
	11th to 20th	Night	56% 7% 10% 15% 9% 3	4733
	21st to end	Night	80% 4 5% 8% 3 1	4852
February	1st to 10th	Night	69% 7% 10% 9% 4 2	2470
	11th to 20th	Night	65% 7% 9% 10% 7% 2	2404
	21st to end	Night	61% 7% 10% 14% 6% 2	2013
March	1st to 10th	Night	62% 9% 13% 10% 6%	3649
	11th to 20th	Night	49% 10% 16% 21% 3	3490
	21st to end	Night	69% 8% 13% 9% 2	3711
April	1st to 10th	Night	63% 10% 14% 12% 2	1900
	11th to 20th	Night	57% 9% 11% 13% 7% 3	1797
	21st to end	Night	61% 9% 13% 10% 7%	1642
May	1st to 10th	Night	44% 6% 14% 25% 9% 1	2540
	11th to 20th	Night	37% 12% 26% 19% 6%	2516
	21st to end	Night	59% 10% 17% 11% 3	2700
June	1st to 10th	Night	54% 8% 17% 13% 5% 2	1330
	11th to 20th	Night	56% 10% 18% 12% 3	1330
	21st to end	Night	42% 9% 20% 18% 8% 3	1330
July	1st to 10th	Night	22% 4 11% 32% 21% 10%	2185
	11th to 20th	Night	17% 4 12% 40% 26% 1	2178
	21st to end	Night	28% 6% 14% 29% 20% 3	2627
August	1st to 10th	Night	16% 4 16% 39% 22% 2	2536
	11th to 20th	Night	35% 7% 26% 20% 8% 3	2839
	21st to end	Night	41% 9% 19% 21% 10%	3269
September	1st to 10th	Night	31% 10% 17% 24% 15% 4	1900
	11th to 20th	Night	45% 6% 13% 15% 16% 4	1840
	21st to end	Night	48% 8% 15% 19% 9% 2	2059
October	1st to 10th	Night	49% 8% 14% 18% 9% 1	2160
	11th to 20th	Night	57% 7% 15% 14% 6% 1	2160
	21st to end	Night	60% 8% 10% 14% 8%	2519
November	1st to 10th	Night	71% 6% 10% 9% 3 1	2590
	11th to 20th	Night	68% 7% 8% 9% 6% 2	2660
	21st to end	Night	69% 7% 9% 7% 7% 1	2660
December	1st to 10th	Night	63% 6% 10% 11% 8% 1	2660
	11th to 20th	Night	77% 6% 7% 5% 3 1	3509
	21st to end	Night	75% 6% 7% 8% 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	49% 10% 19% 10% 8% 3	180
	11th to 20th	Day	54% 8% 13% 17% 7%	180
	21st to end	Day	53% 8% 16% 16% 7%	207
February	1st to 10th	Day	48% 11% 19% 16% 5% 1	370
	11th to 20th	Day	43% 13% 18% 21% 4 1	365
	21st to end	Day	40% 15% 24% 15% 6%	321
March	1st to 10th	Day	41% 15% 19% 18% 6% 1	460
	11th to 20th	Day	41% 12% 17% 19% 9% 1	460
	21st to end	Day	45% 14% 18% 16% 6% 1	506
April	1st to 10th	Day	40% 15% 18% 18% 7% 1	460
	11th to 20th	Day	34% 14% 24% 17% 9% 1	452
	21st to end	Day	35% 16% 23% 17% 9% 1	460
May	1st to 10th	Day	27% 14% 24% 25% 10% 1	463
	11th to 20th	Day	29% 10% 21% 25% 11% 4	488
	21st to end	Day	28% 15% 24% 21% 9% 4	561
June	1st to 10th	Day	30% 12% 24% 24% 8% 1	680
	11th to 20th	Day	33% 15% 23% 21% 7% 2	680
	21st to end	Day	24% 12% 22% 28% 13% 2	680
July	1st to 10th	Day	21% 8% 26% 31% 11% 3	671
	11th to 20th	Day	15% 9% 26% 34% 12% 4	668
	21st to end	Day	13% 7% 25% 35% 12% 6%	564
August	1st to 10th	Day	17% 9% 19% 34% 14% 7%	487
	11th to 20th	Day	14% 5% 23% 35% 17% 5%	477
	21st to end	Day	20% 12% 24% 28% 12% 3	539
September	1st to 10th	Day	24% 10% 23% 29% 13% 2	490
	11th to 20th	Day	29% 9% 19% 27% 14% 2	463
	21st to end	Day	29% 12% 18% 26% 12% 3	450
October	1st to 10th	Day	33% 7% 22% 21% 14% 2	450
	11th to 20th	Day	42% 8% 14% 20% 13% 3	450
	21st to end	Day	42% 10% 20% 17% 9% 2	358
November	1st to 10th	Day	47% 10% 15% 22% 6%	180
	11th to 20th	Day	54% 6% 9% 13% 14% 3	180
	21st to end	Day	51% 9% 17% 9% 8% 7%	180
December	1st to 10th	Day	51% 11% 12% 6% 16% 4	180
	11th to 20th	Day	56% 8% 14% 17% 4 2	180
	21st to end	Day	51% 11% 18% 16% 4 1	198
January	1st to 10th	Night	55% 9% 18% 14% 4	850
	11th to 20th	Night	49% 5% 20% 23% 3	846
	21st to end	Night	47% 10% 18% 20% 4	836
February	1st to 10th	Night	45% 8% 25% 18% 4	760
	11th to 20th	Night	42% 10% 22% 21% 5%	744
	21st to end	Night	39% 11% 24% 19% 7%	628
March	1st to 10th	Night	41% 9% 20% 21% 8% 1	760
	11th to 20th	Night	45% 9% 19% 21% 6%	760
	21st to end	Night	45% 9% 17% 21% 8% 1	836
April	1st to 10th	Night	38% 8% 21% 23% 9% 1	760
	11th to 20th	Night	32% 10% 26% 23% 9% 1	669
	21st to end	Night	38% 7% 22% 24% 9%	502
May	1st to 10th	Night	23% 7% 21% 31% 18% 1	380
	11th to 20th	Night	23% 4 13% 35% 23% 2	374
	21st to end	Night	26% 5% 17% 31% 21%	411
June	1st to 10th	Night	30% 6% 15% 32% 16% 2	380
	11th to 20th	Night	26% 11% 17% 26% 19% 2	380
	21st to end	Night	22% 5% 16% 32% 23% 2	380
July	1st to 10th	Night	13% 5% 10% 36% 32% 3	370
	11th to 20th	Night	12% 4 10% 33% 37% 5%	368
	21st to end	Night	8% 3 7% 33% 45% 3	416
August	1st to 10th	Night	11% 2 6% 29% 46% 6%	380
	11th to 20th	Night	10% 2 8% 36% 39% 5%	564
	21st to end	Night	19% 3 12% 35% 29% 2	698
September	1st to 10th	Night	15% 3 16% 37% 27% 1	760
	11th to 20th	Night	27% 5% 14% 25% 26% 4	736
	21st to end	Night	32% 6% 12% 33% 17% 1	720
October	1st to 10th	Night	31% 4 18% 28% 16% 1	720
	11th to 20th	Night	43% 5% 17% 22% 12% 1	720
	21st to end	Night	42% 7% 21% 21% 7% 1	792
November	1st to 10th	Night	51% 9% 21% 18% 2	740
	11th to 20th	Night	51% 7% 21% 15% 6% 1	760
	21st to end	Night	47% 10% 20% 16% 7% 1	760
December	1st to 10th	Night	40% 9% 23% 23% 6%	760
	11th to 20th	Night	55% 10% 19% 13% 2	847
	21st to end	Night	52% 10% 24% 12% 1	935

Page generated at 2024-09-11 07:00:01. Version ac07

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