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 2025-02-06.

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 7% 4 4 4 3 4 6% 32%	112008
	Night	29% 9% 3 6% 4 4 4 3 4 5% 29%	114904
Transparency	Day	53% 8% 13% 17% 8% 1	111758
	Night	57% 7% 13% 15% 7% 1	114800
Seeing	Day	33% 11% 21% 23% 10% 2	15521
	Night	37% 7% 19% 23% 13% 1	23918

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	41% 13% 3 7% 5% 5% 4 3 4 5% 10%	3179
	11th to 20th	Day	22% 10% 3 6% 4 4 4 3 4 6% 33%	3178
	21st to end	Day	46% 8% 2 5% 3 2 2 2 3 3 23%	4027
February	1st to 10th	Day	36% 11% 4 8% 5% 4 3 3 4 5% 17%	1756
	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 6% 4 4 4 3 4 5% 39%	2280
	21st to end	Day	27% 6% 2 6% 4 4 3 4 5% 6% 34%	2002
October	1st to 10th	Day	24% 7% 3 7% 5% 5% 5% 4 5% 7% 28%	3180
	11th to 20th	Day	37% 7% 2 6% 4 4 3 3 5% 6% 22%	3161
	21st to end	Day	33% 10% 4 9% 5% 5% 4 4 5% 6% 15%	3179
November	1st to 10th	Day	42% 8% 3 6% 6% 4 4 3 4 5% 16%	1568
	11th to 20th	Day	40% 11% 2 7% 3 3 4 2 3 4 20%	1600
	21st to end	Day	41% 11% 4 5% 4 3 3 4 5% 4 16%	1600
December	1st to 10th	Day	25% 11% 3 8% 5% 4 5% 5% 7% 7% 21%	2620
	11th to 20th	Day	43% 15% 3 8% 4 4 4 2 3 4 9%	2650
	21st to end	Day	43% 14% 4 9% 5% 4 4 2 3 3 9%	3498
January	1st to 10th	Night	42% 12% 4 8% 5% 4 4 3 3 4 13%	6766
	11th to 20th	Night	24% 7% 2 6% 4 4 5% 4 6% 8% 30%	6718
	21st to end	Night	41% 9% 2 5% 3 2 3 3 4 4 23%	6929
February	1st to 10th	Night	36% 12% 2 7% 4 4 4 2 4 5% 19%	2535
	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	20% 6% 2 5% 4 4 3 3 4 6% 42%	1900
	21st to end	Night	23% 6% 2 8% 5% 4 4 3 4 5% 37%	2175
October	1st to 10th	Night	21% 10% 3 9% 6% 5% 4 4 5% 5% 28%	3800
	11th to 20th	Night	32% 8% 2 7% 4 3 3 3 4 6% 27%	3777
	21st to end	Night	33% 11% 3 8% 4 4 4 3 4 6% 21%	4376
November	1st to 10th	Night	41% 10% 2 7% 4 4 4 2 3 4 17%	2730
	11th to 20th	Night	40% 10% 3 6% 4 3 3 3 4 4 22%	2800
	21st to end	Night	38% 11% 3 7% 5% 4 5% 3 3 3 18%	2800
December	1st to 10th	Night	27% 10% 3 7% 6% 6% 6% 5% 6% 6% 18%	4560
	11th to 20th	Night	45% 13% 4 7% 5% 4 3 3 3 3 11%	5553
	21st to end	Night	43% 15% 4 8% 4 3 3 2 3 4 13%	7458

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% 7% 7% 8% 2	3179
	11th to 20th	Day	51% 8% 10% 21% 8% 3	3199
	21st to end	Day	67% 4 7% 16% 6%	4027
February	1st to 10th	Day	72% 6% 8% 8% 4 2	1756
	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% 12% 17% 13% 2	2280
	21st to end	Day	51% 9% 16% 15% 9% 1	2002
October	1st to 10th	Day	55% 7% 17% 16% 6%	3180
	11th to 20th	Day	62% 7% 12% 12% 6% 1	3161
	21st to end	Day	68% 7% 10% 10% 4	3179
November	1st to 10th	Day	71% 7% 10% 7% 3 1	1568
	11th to 20th	Day	70% 6% 8% 8% 5% 2	1600
	21st to end	Day	69% 6% 8% 8% 7% 1	1600
December	1st to 10th	Day	58% 9% 8% 18% 7%	2620
	11th to 20th	Day	77% 6% 9% 5% 2 1	2653
	21st to end	Day	79% 8% 6% 5% 1	3498
January	1st to 10th	Night	75% 7% 7% 9% 3	6766
	11th to 20th	Night	46% 9% 15% 18% 9% 3	6759
	21st to end	Night	64% 4 9% 16% 6% 1	6929
February	1st to 10th	Night	69% 7% 10% 8% 4 2	2535
	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% 7% 14% 16% 16% 4	1900
	21st to end	Night	48% 8% 15% 19% 8% 2	2175
October	1st to 10th	Night	57% 7% 16% 14% 6%	3800
	11th to 20th	Night	59% 5% 13% 16% 7%	3777
	21st to end	Night	65% 8% 10% 12% 5%	4376
November	1st to 10th	Night	71% 6% 10% 9% 3 1	2730
	11th to 20th	Night	69% 7% 8% 8% 6% 2	2800
	21st to end	Night	69% 7% 9% 7% 7% 1	2800
December	1st to 10th	Night	59% 9% 13% 13% 5% 1	4560
	11th to 20th	Night	77% 5% 7% 7% 2 1	5549
	21st to end	Night	77% 6% 7% 7% 2	7458

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	48% 10% 20% 13% 8% 3	200
	11th to 20th	Day	49% 9% 15% 19% 8%	200
	21st to end	Day	50% 7% 18% 17% 8%	230
February	1st to 10th	Day	47% 13% 19% 15% 5% 1	386
	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	30% 9% 19% 26% 13% 2	490
	21st to end	Day	30% 13% 19% 26% 11% 3	490
October	1st to 10th	Day	33% 9% 21% 22% 13% 2	490
	11th to 20th	Day	43% 8% 14% 20% 12% 3	490
	21st to end	Day	42% 12% 19% 17% 8% 2	393
November	1st to 10th	Day	47% 10% 17% 21% 6%	200
	11th to 20th	Day	56% 8% 10% 12% 13% 3	200
	21st to end	Day	51% 9% 18% 10% 8% 6%	200
December	1st to 10th	Day	48% 11% 12% 8% 18% 5%	200
	11th to 20th	Day	57% 9% 13% 16% 4 3	200
	21st to end	Day	52% 10% 17% 16% 4	220
January	1st to 10th	Night	54% 10% 19% 13% 4	900
	11th to 20th	Night	46% 6% 22% 23% 3	895
	21st to end	Night	46% 10% 19% 21% 4	880
February	1st to 10th	Night	44% 9% 26% 18% 4	780
	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	26% 4 14% 26% 26% 3	760
	21st to end	Night	33% 6% 13% 32% 16% 1	760
October	1st to 10th	Night	32% 4 19% 28% 16% 1	760
	11th to 20th	Night	43% 5% 18% 22% 11% 1	760
	21st to end	Night	43% 8% 22% 20% 7% 1	836
November	1st to 10th	Night	51% 9% 21% 17% 2	780
	11th to 20th	Night	52% 7% 20% 15% 6% 1	800
	21st to end	Night	47% 10% 20% 17% 7% 1	800
December	1st to 10th	Night	39% 9% 23% 23% 6%	800
	11th to 20th	Night	55% 11% 19% 13% 2	897
	21st to end	Night	52% 11% 24% 12% 1	990

Page generated at 2025-02-03 00:05:51. Version ac07

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