Abbotsford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Abbotsford clear sky chart from 2005-11-06 to 2025-08-05.

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	23% 10% 3 7% 4 4 4 3 4 5% 33%	129842
	Night	27% 11% 3 7% 4 4 3 3 4 5% 30%	126904
Transparency	Day	33% 39% 9% 12% 6% 1	129552
	Night	36% 39% 9% 11% 5% 1	126771
Seeing	Day	29% 10% 21% 24% 13% 4	16186
	Night	34% 7% 14% 24% 18% 3	24390

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	40% 15% 4 8% 5% 4 4 2 3 3 11%	3179
	11th to 20th	Day	20% 12% 4 7% 3 4 4 3 4 5% 34%	3278
	21st to end	Day	39% 10% 3 6% 3 2 2 2 2 3 26%	4004
February	1st to 10th	Day	34% 12% 4 9% 5% 4 4 2 4 4 18%	1796
	11th to 20th	Day	32% 13% 3 7% 5% 4 3 2 4 5% 22%	1755
	21st to end	Day	28% 17% 4 8% 6% 4 4 3 3 4 20%	1531
March	1st to 10th	Day	25% 16% 4 9% 5% 5% 5% 3 4 5% 19%	4598
	11th to 20th	Day	22% 14% 5% 10% 6% 5% 4 3 4 4 24%	5000
	21st to end	Day	27% 14% 4 10% 6% 5% 5% 4 5% 6% 16%	5692
April	1st to 10th	Day	30% 12% 4 9% 6% 5% 4 4 5% 6% 17%	2400
	11th to 20th	Day	23% 12% 4 9% 6% 5% 5% 3 5% 5% 23%	2429
	21st to end	Day	27% 11% 4 8% 5% 5% 4 4 5% 5% 23%	2685
May	1st to 10th	Day	17% 9% 3 7% 5% 4 4 3 4 5% 39%	6320
	11th to 20th	Day	22% 10% 4 9% 5% 5% 5% 3 6% 7% 25%	6277
	21st to end	Day	25% 9% 3 7% 4 4 5% 4 6% 8% 24%	6903
June	1st to 10th	Day	25% 8% 3 8% 5% 4 4 4 5% 6% 28%	2990
	11th to 20th	Day	27% 11% 4 8% 6% 4 5% 3 4 6% 22%	3000
	21st to end	Day	18% 9% 3 7% 6% 5% 5% 4 5% 6% 35%	3000
July	1st to 10th	Day	10% 4 2 4 3 3 3 3 5% 5% 59%	6780
	11th to 20th	Day	6% 3 1 3 2 2 2 2 3 5% 69%	6762
	21st to end	Day	11% 4 2 4 3 3 3 3 5% 7% 57%	6874
August	1st to 10th	Day	7% 4 1 3 2 3 3 3 4 6% 64%	4458
	11th to 20th	Day	14% 8% 2 6% 4 4 4 3 5% 7% 42%	4035
	21st to end	Day	18% 8% 3 7% 4 4 4 3 4 7% 39%	4372
September	1st to 10th	Day	15% 8% 2 6% 4 3 3 2 4 6% 47%	2280
	11th to 20th	Day	18% 8% 3 8% 5% 5% 3 3 5% 4 37%	2280
	21st to end	Day	24% 8% 3 7% 4 4 3 3 4 5% 35%	2008
October	1st to 10th	Day	22% 7% 2 7% 5% 4 5% 3 6% 7% 30%	3180
	11th to 20th	Day	36% 8% 3 6% 4 4 4 3 4 5% 22%	3161
	21st to end	Day	31% 12% 4 9% 5% 4 4 4 6% 5% 16%	3203
November	1st to 10th	Day	39% 9% 3 9% 5% 4 3 2 4 5% 17%	1568
	11th to 20th	Day	38% 13% 4 7% 4 3 3 2 3 3 21%	1600
	21st to end	Day	37% 13% 3 7% 4 4 3 2 4 5% 18%	1600
December	1st to 10th	Day	24% 11% 2 8% 5% 4 4 3 5% 6% 27%	2620
	11th to 20th	Day	38% 15% 4 8% 4 4 3 2 4 4 13%	2726
	21st to end	Day	38% 15% 5% 9% 5% 4 4 3 4 4 10%	3498
January	1st to 10th	Night	40% 15% 4 9% 5% 3 3 2 3 3 14%	6766
	11th to 20th	Night	24% 10% 2 5% 3 4 4 3 5% 8% 32%	6604
	21st to end	Night	36% 11% 3 6% 3 3 2 2 3 4 27%	6952
February	1st to 10th	Night	35% 12% 3 7% 5% 5% 3 2 3 4 20%	2600
	11th to 20th	Night	32% 16% 3 7% 4 4 3 2 3 4 22%	2532
	21st to end	Night	31% 14% 4 6% 5% 4 3 2 4 4 24%	2098
March	1st to 10th	Night	23% 17% 4 8% 4 4 4 3 5% 6% 22%	5293
	11th to 20th	Night	26% 14% 4 8% 4 4 3 3 4 4 26%	4999
	21st to end	Night	37% 13% 4 9% 5% 3 3 3 3 4 17%	5282
April	1st to 10th	Night	29% 13% 3 8% 5% 5% 3 4 4 4 21%	2000
	11th to 20th	Night	23% 10% 3 8% 6% 5% 5% 3 4 5% 27%	1917
	21st to end	Night	29% 11% 3 8% 5% 4 4 3 4 6% 24%	1715
May	1st to 10th	Night	16% 10% 3 8% 4 3 3 2 4 4 43%	3640
	11th to 20th	Night	21% 10% 3 8% 5% 4 4 3 5% 5% 33%	3616
	21st to end	Night	20% 11% 3 8% 5% 5% 5% 4 5% 6% 27%	3972
June	1st to 10th	Night	19% 10% 3 7% 6% 5% 4 3 5% 5% 32%	1407
	11th to 20th	Night	21% 12% 3 8% 6% 5% 5% 3 7% 6% 24%	1400
	21st to end	Night	17% 7% 3 6% 4 4 4 3 5% 6% 41%	1400
July	1st to 10th	Night	10% 4 1 4 3 2 3 2 3 5% 63%	3180
	11th to 20th	Night	4 3 1 2 2 2 2 2 3 4 76%	3195
	21st to end	Night	8% 3 1 4 3 3 3 2 4 6% 63%	3969
August	1st to 10th	Night	6% 3 1 3 2 2 2 3 5% 7% 67%	2561
	11th to 20th	Night	12% 6% 2 5% 3 4 4 3 6% 7% 48%	2799
	21st to end	Night	16% 7% 2 7% 4 4 4 3 7% 8% 37%	3299
September	1st to 10th	Night	12% 4 1 5% 4 3 4 3 5% 7% 52%	1900
	11th to 20th	Night	20% 7% 2 6% 5% 4 3 3 4 6% 42%	1900
	21st to end	Night	22% 8% 3 7% 4 3 3 3 4 5% 39%	2167
October	1st to 10th	Night	23% 10% 3 8% 5% 5% 5% 4 5% 5% 28%	3800
	11th to 20th	Night	35% 9% 2 5% 3 2 3 2 4 5% 29%	3777
	21st to end	Night	32% 12% 4 8% 4 4 4 3 4 5% 21%	4357
November	1st to 10th	Night	41% 11% 3 6% 4 3 4 3 3 4 18%	2728
	11th to 20th	Night	40% 12% 3 6% 4 3 3 2 3 4 21%	2800
	21st to end	Night	38% 11% 3 8% 4 4 4 2 3 3 19%	2800
December	1st to 10th	Night	26% 11% 3 7% 4 3 5% 4 7% 8% 22%	4560
	11th to 20th	Night	41% 13% 4 9% 4 4 3 2 3 4 13%	5461
	21st to end	Night	39% 15% 4 9% 5% 4 4 3 3 4 12%	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	57% 29% 5% 6% 2	3179
	11th to 20th	Day	36% 28% 7% 18% 8% 2	3299
	21st to end	Day	47% 28% 5% 13% 6%	4004
February	1st to 10th	Day	28% 61% 2 2 5% 2	1796
	11th to 20th	Day	28% 61% 3 5% 3 1	1764
	21st to end	Day	27% 61% 4 5% 2 1	1531
March	1st to 10th	Day	46% 32% 6% 12% 4	4598
	11th to 20th	Day	45% 31% 6% 16% 1	5000
	21st to end	Day	49% 32% 9% 7% 2	5692
April	1st to 10th	Day	26% 63% 5% 6%	2400
	11th to 20th	Day	23% 63% 5% 6% 2 1	2429
	21st to end	Day	24% 62% 5% 6% 3	2685
May	1st to 10th	Day	31% 30% 11% 21% 7%	6320
	11th to 20th	Day	42% 33% 15% 9% 1	6280
	21st to end	Day	39% 32% 15% 13% 2	6904
June	1st to 10th	Day	19% 62% 8% 8% 3	2990
	11th to 20th	Day	23% 62% 5% 7% 3	3000
	21st to end	Day	20% 61% 7% 9% 2	3000
July	1st to 10th	Day	19% 26% 15% 17% 16% 7%	6706
	11th to 20th	Day	11% 26% 14% 27% 19% 3	6681
	21st to end	Day	22% 26% 23% 22% 6% 1	6681
August	1st to 10th	Day	11% 37% 9% 28% 16% 1	4441
	11th to 20th	Day	32% 39% 15% 11% 3 1	4074
	21st to end	Day	31% 38% 10% 12% 8%	4371
September	1st to 10th	Day	20% 60% 6% 9% 4 1	2280
	11th to 20th	Day	23% 60% 4 6% 6% 1	2280
	21st to end	Day	21% 60% 7% 7% 5%	2008
October	1st to 10th	Day	36% 38% 11% 13% 2	3180
	11th to 20th	Day	43% 38% 7% 6% 5%	3161
	21st to end	Day	46% 38% 5% 8% 3	3203
November	1st to 10th	Day	30% 57% 6% 6% 1	1568
	11th to 20th	Day	29% 57% 4 6% 3 2	1600
	21st to end	Day	27% 57% 4 7% 4 1	1600
December	1st to 10th	Day	36% 36% 10% 12% 6%	2620
	11th to 20th	Day	54% 34% 5% 6% 1	2729
	21st to end	Day	58% 31% 7% 4 1	3498
January	1st to 10th	Night	55% 28% 5% 8% 3	6766
	11th to 20th	Night	32% 30% 12% 14% 9% 3	6645
	21st to end	Night	45% 29% 8% 14% 4	6952
February	1st to 10th	Night	27% 61% 3 3 4 3	2600
	11th to 20th	Night	28% 61% 3 5% 2 1	2534
	21st to end	Night	23% 61% 5% 7% 3 1	2098
March	1st to 10th	Night	44% 33% 8% 10% 6%	5293
	11th to 20th	Night	42% 32% 8% 16% 1	5000
	21st to end	Night	52% 32% 10% 5% 1	5282
April	1st to 10th	Night	25% 63% 5% 6% 1	2000
	11th to 20th	Night	22% 63% 6% 5% 3 1	1917
	21st to end	Night	22% 62% 6% 7% 2	1715
May	1st to 10th	Night	31% 29% 8% 24% 8%	3637
	11th to 20th	Night	40% 31% 17% 11% 1	3616
	21st to end	Night	42% 31% 13% 13% 1	3972
June	1st to 10th	Night	17% 62% 8% 9% 3 1	1407
	11th to 20th	Night	20% 63% 6% 9% 2	1400
	21st to end	Night	19% 60% 8% 10% 3	1400
July	1st to 10th	Night	17% 26% 14% 23% 14% 6%	3145
	11th to 20th	Night	7% 25% 16% 29% 22% 1	3153
	21st to end	Night	20% 25% 21% 23% 11% 1	3857
August	1st to 10th	Night	8% 36% 11% 29% 16% 1	2553
	11th to 20th	Night	26% 38% 20% 12% 3 1	2826
	21st to end	Night	30% 39% 13% 11% 7%	3299
September	1st to 10th	Night	18% 61% 7% 9% 5% 1	1900
	11th to 20th	Night	22% 61% 5% 5% 6% 1	1900
	21st to end	Night	20% 60% 6% 9% 4	2167
October	1st to 10th	Night	40% 38% 12% 8% 2	3800
	11th to 20th	Night	40% 37% 7% 11% 5%	3777
	21st to end	Night	44% 38% 6% 10% 3	4357
November	1st to 10th	Night	31% 56% 6% 5% 1	2728
	11th to 20th	Night	29% 57% 4 5% 3 2	2800
	21st to end	Night	30% 57% 3 4 5% 1	2800
December	1st to 10th	Night	37% 37% 13% 9% 4	4560
	11th to 20th	Night	54% 34% 5% 6% 1 1	5457
	21st to end	Night	57% 30% 6% 6% 1	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	46% 11% 18% 14% 9% 4	200
	11th to 20th	Day	45% 12% 12% 18% 11% 4	200
	21st to end	Day	41% 10% 16% 20% 9% 4	220
February	1st to 10th	Day	45% 13% 18% 15% 7% 2	396
	11th to 20th	Day	41% 9% 23% 18% 7% 1	395
	21st to end	Day	41% 12% 25% 14% 7% 1	355
March	1st to 10th	Day	37% 13% 22% 19% 9% 1	500
	11th to 20th	Day	36% 13% 18% 20% 12% 2	500
	21st to end	Day	39% 12% 21% 19% 8% 1	550
April	1st to 10th	Day	35% 14% 21% 19% 9% 2	500
	11th to 20th	Day	26% 15% 26% 18% 12% 3	492
	21st to end	Day	29% 15% 23% 19% 10% 4	500
May	1st to 10th	Day	23% 10% 28% 26% 10% 3	503
	11th to 20th	Day	27% 8% 21% 25% 14% 5%	528
	21st to end	Day	29% 10% 21% 24% 11% 4	573
June	1st to 10th	Day	23% 12% 27% 26% 10% 2	720
	11th to 20th	Day	28% 11% 25% 25% 8% 2	730
	21st to end	Day	21% 9% 24% 28% 16% 3	730
July	1st to 10th	Day	17% 7% 26% 34% 14% 3	721
	11th to 20th	Day	11% 8% 25% 37% 15% 5%	713
	21st to end	Day	11% 6% 19% 37% 19% 8%	575
August	1st to 10th	Day	13% 5% 18% 33% 18% 12%	504
	11th to 20th	Day	10% 5% 18% 36% 23% 9%	477
	21st to end	Day	17% 9% 21% 28% 17% 7%	539
September	1st to 10th	Day	20% 8% 21% 28% 15% 7%	490
	11th to 20th	Day	22% 9% 18% 31% 17% 4	490
	21st to end	Day	28% 8% 20% 25% 14% 4	490
October	1st to 10th	Day	31% 8% 18% 20% 18% 5%	490
	11th to 20th	Day	37% 8% 14% 21% 16% 4	490
	21st to end	Day	41% 12% 17% 17% 11% 2	395
November	1st to 10th	Day	40% 15% 19% 17% 10%	200
	11th to 20th	Day	51% 6% 17% 10% 11% 6%	200
	21st to end	Day	46% 8% 20% 10% 12% 6%	200
December	1st to 10th	Day	44% 8% 16% 11% 13% 10%	200
	11th to 20th	Day	50% 11% 16% 15% 8% 1	200
	21st to end	Day	50% 9% 18% 18% 5% 1	220
January	1st to 10th	Night	50% 10% 14% 16% 9% 1	900
	11th to 20th	Night	44% 8% 13% 23% 12% 1	871
	21st to end	Night	42% 9% 16% 22% 11% 1	880
February	1st to 10th	Night	43% 11% 17% 21% 6% 1	800
	11th to 20th	Night	42% 8% 19% 23% 9%	784
	21st to end	Night	38% 10% 20% 21% 9% 1	660
March	1st to 10th	Night	33% 12% 17% 24% 14% 1	800
	11th to 20th	Night	41% 7% 17% 22% 12% 1	800
	21st to end	Night	41% 8% 16% 24% 10% 2	880
April	1st to 10th	Night	37% 8% 16% 27% 12% 1	800
	11th to 20th	Night	28% 9% 20% 26% 16% 2	729
	21st to end	Night	35% 7% 13% 29% 15% 2	515
May	1st to 10th	Night	24% 7% 13% 32% 23% 2	400
	11th to 20th	Night	21% 3 10% 29% 32% 4	394
	21st to end	Night	25% 4 10% 31% 27% 3	433
June	1st to 10th	Night	23% 6% 14% 31% 23% 4	400
	11th to 20th	Night	26% 6% 14% 30% 21% 5%	400
	21st to end	Night	21% 4 9% 30% 32% 5%	400
July	1st to 10th	Night	14% 2 10% 29% 42% 3	390
	11th to 20th	Night	11% 4 7% 31% 40% 8%	388
	21st to end	Night	8% 1 5% 26% 50% 8%	438
August	1st to 10th	Night	14% 1 4 21% 45% 15%	386
	11th to 20th	Night	9% 1 6% 24% 47% 12%	551
	21st to end	Night	16% 3 7% 30% 38% 6%	715
September	1st to 10th	Night	16% 2 8% 38% 29% 7%	760
	11th to 20th	Night	22% 5% 11% 23% 32% 7%	760
	21st to end	Night	28% 5% 12% 29% 25% 3	760
October	1st to 10th	Night	28% 4 13% 27% 24% 3	760
	11th to 20th	Night	37% 7% 13% 24% 17% 3	760
	21st to end	Night	40% 8% 16% 24% 10% 2	836
November	1st to 10th	Night	48% 8% 17% 22% 5%	780
	11th to 20th	Night	50% 7% 17% 16% 10% 1	800
	21st to end	Night	46% 9% 16% 16% 11% 2	800
December	1st to 10th	Night	37% 8% 18% 24% 12% 1	800
	11th to 20th	Night	50% 10% 19% 17% 4 1	870
	21st to end	Night	51% 9% 20% 15% 4	990

Page generated at 2025-08-01 22:32:24. Version ac07

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