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 2026-06-01.

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	24% 9% 3 7% 4 4 4 3 5% 6% 32%	135840
	Night	28% 9% 3 7% 4 4 4 3 4 5% 29%	136030
Transparency	Day	53% 8% 14% 17% 7% 1	135549
	Night	56% 7% 13% 15% 7% 1	135899
Seeing	Day	33% 11% 21% 23% 10% 2	17258
	Night	37% 8% 19% 23% 12% 1	25558

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	43% 13% 4 8% 4 5% 4 3 4 5% 8%	4125
	11th to 20th	Day	22% 9% 3 6% 3 4 4 3 6% 9% 31%	4152
	21st to end	Day	42% 8% 2 6% 4 3 3 2 3 4 23%	5223
February	1st to 10th	Day	35% 11% 3 8% 5% 4 3 3 4 5% 17%	1890
	11th to 20th	Day	32% 10% 3 8% 5% 5% 4 2 4 5% 22%	1845
	21st to end	Day	28% 14% 4 8% 6% 4 4 3 4 5% 20%	1587
March	1st to 10th	Day	29% 15% 4 9% 5% 4 4 3 4 6% 17%	4742
	11th to 20th	Day	26% 13% 4 8% 5% 4 4 3 4 5% 24%	5110
	21st to end	Day	31% 13% 3 9% 6% 5% 4 4 5% 5% 16%	5779
April	1st to 10th	Day	29% 10% 3 9% 5% 6% 4 4 6% 6% 18%	2520
	11th to 20th	Day	23% 10% 3 8% 6% 5% 5% 4 5% 6% 25%	2578
	21st to end	Day	25% 11% 4 7% 5% 4 4 4 5% 5% 26%	2805
May	1st to 10th	Day	16% 8% 2 7% 4 4 4 3 4 5% 42%	6460
	11th to 20th	Day	19% 9% 3 8% 5% 5% 5% 4 6% 8% 27%	6417
	21st to end	Day	24% 8% 3 7% 4 4 5% 5% 6% 8% 26%	7145
June	1st to 10th	Day	23% 8% 3 7% 5% 5% 4 4 5% 6% 31%	3001
	11th to 20th	Day	24% 9% 3 8% 6% 5% 5% 4 5% 7% 23%	3000
	21st to end	Day	17% 9% 3 7% 4 5% 5% 3 6% 7% 34%	3000
July	1st to 10th	Day	10% 3 1 5% 3 3 3 3 4 5% 59%	6780
	11th to 20th	Day	6% 3 1 3 2 2 2 2 4 6% 69%	6780
	21st to end	Day	11% 4 1 4 3 3 3 3 4 7% 58%	6948
August	1st to 10th	Day	7% 3 1 4 3 3 3 2 4 6% 65%	4524
	11th to 20th	Day	16% 6% 2 5% 3 4 4 4 5% 7% 43%	4156
	21st to end	Day	18% 7% 2 6% 4 3 4 4 5% 7% 40%	4541
September	1st to 10th	Day	15% 7% 3 6% 3 3 3 3 5% 6% 45%	2400
	11th to 20th	Day	20% 8% 3 6% 4 4 4 3 4 5% 40%	2400
	21st to end	Day	27% 6% 2 6% 4 4 3 4 5% 6% 33%	2107
October	1st to 10th	Day	24% 7% 3 7% 5% 5% 5% 4 5% 7% 28%	3280
	11th to 20th	Day	37% 7% 2 6% 4 3 4 3 5% 6% 23%	3261
	21st to end	Day	34% 11% 4 9% 5% 5% 4 4 5% 6% 15%	3281
November	1st to 10th	Day	41% 9% 3 6% 6% 4 4 3 4 5% 16%	1648
	11th to 20th	Day	41% 11% 2 7% 3 3 4 3 3 3 19%	1680
	21st to end	Day	41% 11% 4 5% 4 3 3 4 5% 4 16%	1680
December	1st to 10th	Day	26% 11% 3 8% 5% 4 5% 4 7% 7% 20%	2700
	11th to 20th	Day	43% 15% 3 8% 4 4 4 2 3 4 9%	2720
	21st to end	Day	43% 14% 4 9% 5% 4 4 2 3 3 9%	3575
January	1st to 10th	Night	41% 13% 4 9% 5% 4 4 3 3 4 11%	8770
	11th to 20th	Night	26% 7% 2 5% 4 4 5% 4 5% 10% 28%	8744
	21st to end	Night	38% 8% 2 6% 3 3 3 3 4 5% 24%	8958
February	1st to 10th	Night	35% 12% 3 7% 4 4 4 2 4 5% 20%	2730
	11th to 20th	Night	30% 13% 3 8% 4 3 3 3 4 5% 24%	2662
	21st to end	Night	31% 13% 3 6% 4 3 3 3 4 5% 25%	2218
March	1st to 10th	Night	28% 15% 3 7% 4 4 4 4 5% 6% 21%	5367
	11th to 20th	Night	29% 12% 3 7% 4 4 3 3 4 6% 25%	5109
	21st to end	Night	39% 12% 4 8% 4 4 3 2 4 4 18%	5437
April	1st to 10th	Night	29% 11% 3 8% 5% 5% 4 4 4 6% 22%	2100
	11th to 20th	Night	21% 11% 3 9% 5% 5% 4 3 6% 6% 28%	1988
	21st to end	Night	26% 9% 3 6% 4 5% 4 3 4 6% 29%	1814
May	1st to 10th	Night	17% 8% 3 6% 4 3 3 2 3 4 47%	3720
	11th to 20th	Night	17% 8% 3 7% 4 3 4 3 6% 7% 35%	3696
	21st to end	Night	22% 9% 3 8% 5% 5% 5% 4 5% 6% 29%	3968
June	1st to 10th	Night	23% 8% 3 6% 5% 5% 5% 3 6% 5% 32%	1400
	11th to 20th	Night	17% 11% 4 9% 5% 5% 4 5% 6% 7% 28%	1400
	21st to end	Night	16% 7% 3 5% 5% 5% 4 4 6% 6% 41%	1400
July	1st to 10th	Night	10% 4 1 3 3 3 2 2 4 6% 62%	3180
	11th to 20th	Night	4 2 1 2 2 1 2 2 3 4 78%	3180
	21st to end	Night	6% 4 1 4 3 3 3 3 5% 6% 62%	3892
August	1st to 10th	Night	5% 3 1 2 1 1 2 3 5% 6% 70%	2624
	11th to 20th	Night	13% 5% 2 5% 4 4 4 3 4 7% 48%	2902
	21st to end	Night	14% 5% 2 6% 4 5% 5% 3 5% 8% 42%	3372
September	1st to 10th	Night	10% 4 2 5% 3 3 4 3 5% 6% 54%	2000
	11th to 20th	Night	20% 6% 2 5% 4 4 4 3 4 6% 43%	2000
	21st to end	Night	24% 6% 3 8% 5% 4 4 2 4 5% 37%	2290
October	1st to 10th	Night	21% 10% 3 9% 5% 5% 4 4 5% 5% 29%	3920
	11th to 20th	Night	32% 8% 2 7% 4 3 3 3 4 6% 28%	3897
	21st to end	Night	33% 11% 3 8% 4 4 4 3 4 6% 21%	4516
November	1st to 10th	Night	41% 10% 3 7% 4 4 4 2 4 4 17%	2870
	11th to 20th	Night	40% 10% 3 6% 4 3 4 3 4 4 21%	2940
	21st to end	Night	38% 11% 3 7% 5% 4 5% 3 3 3 18%	2940
December	1st to 10th	Night	28% 10% 3 7% 6% 6% 6% 5% 6% 5% 17%	4700
	11th to 20th	Night	45% 13% 4 8% 5% 4 3 3 3 3 11%	5703
	21st to end	Night	42% 14% 4 8% 4 3 3 2 3 4 13%	7623

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	79% 6% 6% 6% 1	4125
	11th to 20th	Day	48% 7% 8% 24% 10% 2	4173
	21st to end	Day	66% 4 6% 18% 5% 1	5224
February	1st to 10th	Day	70% 6% 9% 8% 5% 2	1890
	11th to 20th	Day	65% 6% 9% 11% 7% 1	1854
	21st to end	Day	67% 8% 9% 9% 5% 2	1587
March	1st to 10th	Day	65% 9% 11% 11% 3	4742
	11th to 20th	Day	64% 7% 9% 18% 2	5110
	21st to end	Day	69% 8% 12% 8% 2	5779
April	1st to 10th	Day	66% 9% 14% 9% 2	2520
	11th to 20th	Day	60% 8% 11% 11% 7% 2	2578
	21st to end	Day	59% 9% 13% 12% 7%	2805
May	1st to 10th	Day	43% 8% 15% 24% 9%	6460
	11th to 20th	Day	53% 11% 19% 14% 3	6420
	21st to end	Day	53% 10% 18% 16% 2	7146
June	1st to 10th	Day	54% 8% 18% 13% 5% 2	3001
	11th to 20th	Day	61% 10% 15% 10% 3	3000
	21st to end	Day	50% 8% 18% 16% 8% 1	3000
July	1st to 10th	Day	28% 7% 19% 22% 18% 7%	6706
	11th to 20th	Day	19% 4 21% 33% 21% 2	6699
	21st to end	Day	26% 7% 28% 27% 10% 1	6753
August	1st to 10th	Day	22% 7% 15% 40% 16% 1	4507
	11th to 20th	Day	41% 8% 23% 18% 8% 1	4195
	21st to end	Day	43% 8% 18% 20% 11% 1	4540
September	1st to 10th	Day	40% 8% 16% 22% 11% 4	2400
	11th to 20th	Day	47% 8% 12% 18% 13% 2	2400
	21st to end	Day	51% 9% 16% 15% 9% 1	2107
October	1st to 10th	Day	55% 7% 17% 16% 6%	3280
	11th to 20th	Day	62% 7% 12% 12% 7% 1	3261
	21st to end	Day	68% 7% 9% 10% 4	3281
November	1st to 10th	Day	71% 7% 11% 8% 3 1	1648
	11th to 20th	Day	70% 6% 8% 8% 5% 2	1680
	21st to end	Day	70% 6% 8% 8% 7% 1	1680
December	1st to 10th	Day	59% 9% 8% 17% 7%	2700
	11th to 20th	Day	77% 6% 9% 5% 2 1	2723
	21st to end	Day	79% 7% 6% 5% 1	3575
January	1st to 10th	Night	76% 6% 7% 7% 2	8770
	11th to 20th	Night	45% 9% 12% 19% 13% 2	8785
	21st to end	Night	62% 4 9% 18% 7% 1	8958
February	1st to 10th	Night	68% 6% 10% 9% 5% 3	2730
	11th to 20th	Night	64% 7% 8% 11% 8% 2	2664
	21st to end	Night	63% 7% 10% 13% 5% 2	2218
March	1st to 10th	Night	61% 8% 13% 11% 6%	5367
	11th to 20th	Night	60% 8% 13% 17% 3	5110
	21st to end	Night	72% 6% 13% 7% 1	5437
April	1st to 10th	Night	63% 9% 14% 12% 2	2100
	11th to 20th	Night	56% 9% 12% 13% 7% 3	1988
	21st to end	Night	57% 8% 15% 12% 7%	1814
May	1st to 10th	Night	43% 5% 13% 28% 10%	3717
	11th to 20th	Night	47% 11% 22% 16% 4	3696
	21st to end	Night	55% 9% 18% 16% 2	3968
June	1st to 10th	Night	52% 8% 18% 13% 6% 2	1400
	11th to 20th	Night	55% 10% 17% 14% 3	1400
	21st to end	Night	43% 9% 20% 18% 7% 3	1400
July	1st to 10th	Night	26% 5% 18% 28% 16% 7%	3145
	11th to 20th	Night	14% 4 21% 36% 24% 2	3138
	21st to end	Night	23% 6% 23% 31% 16% 2	3782
August	1st to 10th	Night	16% 5% 17% 39% 21% 2	2616
	11th to 20th	Night	36% 7% 26% 20% 8% 3	2929
	21st to end	Night	40% 8% 19% 21% 11% 1	3372
September	1st to 10th	Night	31% 10% 18% 24% 14% 4	2000
	11th to 20th	Night	44% 7% 14% 17% 15% 3	2000
	21st to end	Night	49% 8% 15% 19% 8% 2	2290
October	1st to 10th	Night	57% 7% 17% 14% 5%	3920
	11th to 20th	Night	58% 5% 13% 16% 7%	3897
	21st to end	Night	65% 8% 10% 12% 5%	4516
November	1st to 10th	Night	71% 6% 10% 9% 3 1	2870
	11th to 20th	Night	69% 7% 8% 9% 5% 2	2940
	21st to end	Night	69% 7% 9% 7% 7% 1	2940
December	1st to 10th	Night	60% 9% 13% 13% 5% 1	4700
	11th to 20th	Night	78% 5% 7% 6% 2 1	5699
	21st to end	Night	76% 6% 7% 7% 2	7623

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% 12% 7% 3	220
	11th to 20th	Day	47% 9% 15% 20% 10%	220
	21st to end	Day	49% 7% 19% 17% 8%	253
February	1st to 10th	Day	46% 12% 19% 17% 5% 1	430
	11th to 20th	Day	42% 13% 18% 22% 5% 1	425
	21st to end	Day	43% 15% 23% 14% 5%	372
March	1st to 10th	Day	42% 13% 20% 18% 5% 1	540
	11th to 20th	Day	44% 13% 16% 17% 8% 1	540
	21st to end	Day	46% 14% 19% 14% 6% 1	594
April	1st to 10th	Day	39% 15% 19% 20% 7% 1	540
	11th to 20th	Day	32% 14% 25% 18% 10% 1	532
	21st to end	Day	34% 17% 22% 16% 11% 1	540
May	1st to 10th	Day	27% 14% 24% 24% 9% 1	543
	11th to 20th	Day	31% 12% 21% 23% 10% 3	568
	21st to end	Day	26% 16% 25% 20% 9% 4	653
June	1st to 10th	Day	28% 13% 25% 24% 8% 2	731
	11th to 20th	Day	32% 14% 23% 22% 8% 2	730
	21st to end	Day	25% 11% 22% 28% 12% 2	730
July	1st to 10th	Day	20% 9% 27% 31% 10% 3	721
	11th to 20th	Day	15% 9% 28% 32% 12% 3	718
	21st to end	Day	13% 7% 26% 35% 12% 6%	610
August	1st to 10th	Day	18% 9% 19% 33% 14% 7%	527
	11th to 20th	Day	15% 5% 25% 34% 16% 5%	517
	21st to end	Day	19% 12% 23% 29% 14% 3	583
September	1st to 10th	Day	23% 9% 23% 28% 14% 3	530
	11th to 20th	Day	29% 8% 19% 28% 13% 2	530
	21st to end	Day	30% 13% 20% 25% 10% 2	530
October	1st to 10th	Day	33% 9% 22% 22% 13% 2	530
	11th to 20th	Day	43% 9% 14% 20% 12% 2	530
	21st to end	Day	45% 12% 18% 17% 7% 2	429
November	1st to 10th	Day	48% 10% 18% 19% 5%	220
	11th to 20th	Day	57% 7% 10% 11% 12% 3	220
	21st to end	Day	52% 9% 18% 9% 7% 5%	220
December	1st to 10th	Day	51% 10% 11% 7% 16% 4	220
	11th to 20th	Day	59% 10% 12% 14% 3 2	220
	21st to end	Day	52% 10% 17% 16% 4	242
January	1st to 10th	Night	54% 10% 19% 13% 4	950
	11th to 20th	Night	46% 6% 22% 23% 3	944
	21st to end	Night	45% 10% 20% 21% 4	924
February	1st to 10th	Night	44% 9% 25% 18% 4	840
	11th to 20th	Night	41% 10% 23% 22% 5%	824
	21st to end	Night	41% 11% 23% 18% 6%	692
March	1st to 10th	Night	41% 9% 20% 21% 8%	840
	11th to 20th	Night	47% 9% 18% 21% 5%	840
	21st to end	Night	45% 9% 19% 19% 8% 1	924
April	1st to 10th	Night	38% 8% 20% 24% 8% 1	840
	11th to 20th	Night	31% 10% 26% 24% 8% 1	740
	21st to end	Night	36% 8% 22% 25% 9%	554
May	1st to 10th	Night	23% 6% 22% 31% 17% 1	420
	11th to 20th	Night	25% 4 14% 34% 21% 2	414
	21st to end	Night	24% 5% 17% 33% 20%	455
June	1st to 10th	Night	29% 5% 16% 33% 16% 2	400
	11th to 20th	Night	25% 10% 17% 27% 19% 2	400
	21st to end	Night	23% 5% 16% 31% 23% 3	400
July	1st to 10th	Night	13% 6% 10% 36% 33% 3	390
	11th to 20th	Night	11% 4 10% 35% 36% 4	388
	21st to end	Night	8% 3 8% 32% 46% 3	438
August	1st to 10th	Night	12% 2 6% 29% 46% 5%	400
	11th to 20th	Night	11% 3 8% 36% 38% 5%	594
	21st to end	Night	18% 3 13% 36% 29% 2	735
September	1st to 10th	Night	15% 3 16% 37% 27% 1	800
	11th to 20th	Night	26% 4 15% 26% 26% 3	800
	21st to end	Night	33% 6% 14% 32% 15% 1	800
October	1st to 10th	Night	32% 5% 19% 27% 15% 1	800
	11th to 20th	Night	44% 5% 19% 21% 11% 1	800
	21st to end	Night	44% 8% 22% 19% 6% 1	880
November	1st to 10th	Night	51% 10% 21% 17% 1	820
	11th to 20th	Night	52% 8% 20% 14% 5%	840
	21st to end	Night	48% 10% 19% 16% 6%	840
December	1st to 10th	Night	41% 9% 22% 23% 6%	840
	11th to 20th	Night	57% 10% 18% 12% 2	947
	21st to end	Night	51% 12% 24% 12% 1	1045

Page generated at 2026-05-28 22:53:25. Version ac07

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