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 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	24% 10% 3 7% 4 4 4 3 4 5% 32%	105475
	Night	28% 11% 3 7% 4 3 3 3 4 5% 30%	102119
Transparency	Day	28% 47% 7% 11% 5% 1	105227
	Night	31% 47% 7% 10% 5% 1	102013
Seeing	Day	29% 10% 21% 24% 12% 4	15242
	Night	34% 7% 14% 24% 18% 3	23470

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% 16% 4 8% 5% 4 4 2 3 3 11%	2219
	11th to 20th	Day	29% 13% 4 8% 4 4 3 2 3 4 26%	2276
	21st to end	Day	50% 13% 3 6% 3 2 2 2 3 3 12%	2794
February	1st to 10th	Day	35% 12% 4 9% 5% 4 4 2 4 4 18%	1706
	11th to 20th	Day	32% 13% 3 7% 5% 4 3 2 4 5% 22%	1665
	21st to end	Day	27% 17% 4 9% 6% 4 4 3 3 4 20%	1456
March	1st to 10th	Day	24% 18% 5% 9% 5% 4 4 3 4 6% 18%	3192
	11th to 20th	Day	23% 12% 3 7% 4 4 3 3 4 4 33%	3490
	21st to end	Day	27% 14% 4 9% 5% 4 4 3 5% 5% 20%	3966
April	1st to 10th	Day	30% 12% 4 9% 6% 5% 4 4 5% 6% 17%	2280
	11th to 20th	Day	24% 12% 4 9% 6% 5% 5% 3 5% 5% 22%	2306
	21st to end	Day	27% 11% 4 8% 5% 5% 4 4 5% 5% 22%	2551
May	1st to 10th	Day	20% 9% 3 7% 4 4 4 3 4 4 37%	4420
	11th to 20th	Day	17% 8% 2 6% 4 5% 5% 4 6% 8% 34%	4377
	21st to end	Day	32% 12% 3 9% 4 4 4 3 4 5% 19%	4813
June	1st to 10th	Day	26% 9% 3 8% 5% 4 4 3 5% 6% 26%	2840
	11th to 20th	Day	28% 11% 4 8% 6% 4 5% 3 4 6% 21%	2850
	21st to end	Day	17% 8% 3 6% 6% 5% 5% 4 5% 6% 35%	2850
July	1st to 10th	Day	9% 4 2 4 3 2 3 3 4 4 62%	4740
	11th to 20th	Day	7% 4 1 3 2 2 2 2 3 5% 68%	4722
	21st to end	Day	14% 5% 2 4 3 3 3 2 5% 6% 53%	4790
August	1st to 10th	Day	7% 4 1 3 2 3 3 3 4 6% 64%	4401
	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% 10% 4 9% 5% 4 3 2 4 4 17%	1512
	11th to 20th	Day	38% 13% 3 6% 4 3 3 2 3 3 22%	1520
	21st to end	Day	37% 13% 3 7% 4 3 3 2 4 5% 19%	1520
December	1st to 10th	Day	33% 16% 3 7% 3 2 2 3 3 3 25%	1520
	11th to 20th	Day	35% 14% 4 8% 4 4 3 2 4 4 18%	1738
	21st to end	Day	37% 16% 4 9% 5% 4 4 2 3 4 11%	2442
January	1st to 10th	Night	42% 16% 4 8% 5% 3 3 2 3 3 12%	4726
	11th to 20th	Night	33% 10% 2 4 3 3 3 2 4 7% 29%	4606
	21st to end	Night	48% 14% 3 7% 3 2 2 2 3 3 13%	4862
February	1st to 10th	Night	37% 12% 3 7% 5% 5% 3 2 3 4 20%	2470
	11th to 20th	Night	32% 16% 3 7% 4 4 3 2 3 4 22%	2402
	21st to end	Night	31% 14% 4 6% 5% 3 3 2 4 4 25%	1997
March	1st to 10th	Night	24% 17% 4 8% 4 4 4 3 4 5% 22%	3679
	11th to 20th	Night	26% 9% 3 6% 3 3 3 3 4 5% 36%	3489
	21st to end	Night	33% 14% 4 9% 5% 4 3 3 3 3 20%	3686
April	1st to 10th	Night	29% 12% 3 8% 5% 5% 3 4 4 5% 21%	1900
	11th to 20th	Night	24% 11% 3 8% 7% 5% 5% 3 4 5% 26%	1820
	21st to end	Night	30% 12% 3 8% 5% 4 4 3 4 6% 21%	1629
May	1st to 10th	Night	18% 10% 3 7% 3 3 3 2 3 5% 43%	2540
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 5% 6% 43%	2516
	21st to end	Night	27% 12% 4 8% 4 4 4 3 4 5% 24%	2762
June	1st to 10th	Night	20% 11% 3 7% 6% 5% 4 3 5% 5% 31%	1337
	11th to 20th	Night	22% 12% 3 8% 5% 5% 5% 3 6% 6% 24%	1330
	21st to end	Night	16% 7% 3 6% 4 4 4 3 5% 6% 42%	1330
July	1st to 10th	Night	7% 3 1 3 3 2 3 2 3 5% 67%	2220
	11th to 20th	Night	5% 4 1 2 2 2 1 1 3 4 74%	2235
	21st to end	Night	11% 4 2 4 3 3 3 2 4 5% 59%	2762
August	1st to 10th	Night	6% 3 1 3 2 2 2 3 5% 7% 67%	2529
	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%	2636
	11th to 20th	Night	40% 11% 2 6% 4 3 3 3 3 4 22%	2660
	21st to end	Night	39% 11% 3 7% 4 4 4 2 3 3 20%	2660
December	1st to 10th	Night	33% 11% 3 6% 3 3 4 3 5% 5% 26%	2660
	11th to 20th	Night	42% 13% 3 8% 5% 3 3 2 3 3 15%	3463
	21st to end	Night	40% 14% 3 8% 4 4 4 3 2 4 14%	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	48% 40% 5% 4 2	2219
	11th to 20th	Day	38% 37% 4 11% 6% 3	2297
	21st to end	Day	53% 40% 3 3 1	2794
February	1st to 10th	Day	27% 64% 2 2 4 2	1706
	11th to 20th	Day	26% 64% 3 4 3 1	1674
	21st to end	Day	24% 64% 3 5% 2 1	1456
March	1st to 10th	Day	36% 44% 7% 9% 3	3192
	11th to 20th	Day	28% 42% 8% 21% 1	3490
	21st to end	Day	38% 43% 9% 6% 3 1	3966
April	1st to 10th	Day	24% 66% 4 5%	2280
	11th to 20th	Day	23% 66% 4 5% 2 1	2306
	21st to end	Day	24% 65% 4 4 3	2551
May	1st to 10th	Day	26% 41% 9% 17% 6% 1	4420
	11th to 20th	Day	24% 44% 19% 11% 1	4380
	21st to end	Day	41% 43% 10% 5% 1	4814
June	1st to 10th	Day	19% 65% 6% 7% 2	2840
	11th to 20th	Day	21% 65% 5% 6% 3	2850
	21st to end	Day	18% 64% 7% 9% 2	2850
July	1st to 10th	Day	14% 36% 4 16% 20% 9%	4666
	11th to 20th	Day	8% 36% 5% 28% 20% 2	4641
	21st to end	Day	23% 36% 16% 18% 6% 1	4639
August	1st to 10th	Day	10% 37% 8% 28% 16% 1	4384
	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	29% 58% 5% 6% 1	1512
	11th to 20th	Day	27% 59% 3 6% 3 2	1520
	21st to end	Day	24% 60% 3 7% 5% 1	1520
December	1st to 10th	Day	28% 59% 2 6% 5% 1	1520
	11th to 20th	Day	36% 50% 4 7% 2	1741
	21st to end	Day	47% 42% 6% 3 1 1	2442
January	1st to 10th	Night	48% 40% 3 6% 2	4726
	11th to 20th	Night	32% 38% 6% 12% 7% 4	4647
	21st to end	Night	53% 41% 3 4	4862
February	1st to 10th	Night	25% 64% 3 3 3 2	2470
	11th to 20th	Night	27% 64% 3 4 2 1	2404
	21st to end	Night	20% 64% 5% 7% 3 1	1997
March	1st to 10th	Night	36% 45% 5% 8% 6%	3679
	11th to 20th	Night	25% 43% 10% 20% 2	3490
	21st to end	Night	40% 45% 8% 6% 1	3686
April	1st to 10th	Night	23% 66% 4 6% 1	1900
	11th to 20th	Night	22% 66% 4 4 2 1	1820
	21st to end	Night	23% 65% 4 6% 2	1629
May	1st to 10th	Night	25% 40% 7% 19% 8% 1	2540
	11th to 20th	Night	23% 43% 19% 14% 2	2516
	21st to end	Night	40% 42% 10% 7% 1	2762
June	1st to 10th	Night	17% 65% 7% 8% 2 1	1337
	11th to 20th	Night	19% 66% 6% 6% 2	1330
	21st to end	Night	16% 63% 8% 10% 3	1330
July	1st to 10th	Night	9% 36% 4 24% 18% 9%	2185
	11th to 20th	Night	7% 35% 5% 29% 23% 1	2193
	21st to end	Night	22% 36% 10% 18% 14% 1	2674
August	1st to 10th	Night	8% 36% 11% 29% 16% 1	2521
	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% 58% 6% 5% 1	2636
	11th to 20th	Night	26% 60% 4 5% 4 2	2660
	21st to end	Night	27% 60% 3 4 5% 1	2660
December	1st to 10th	Night	25% 61% 3 5% 5%	2660
	11th to 20th	Night	41% 50% 3 3 2 1	3459
	21st to end	Night	47% 40% 5% 5% 2	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	46% 11% 19% 12% 9% 4	180
	11th to 20th	Day	48% 12% 13% 16% 8% 3	180
	21st to end	Day	43% 11% 17% 18% 10% 1	198
February	1st to 10th	Day	45% 13% 18% 15% 6% 2	366
	11th to 20th	Day	41% 10% 24% 17% 7% 1	365
	21st to end	Day	41% 12% 26% 14% 7% 1	328
March	1st to 10th	Day	38% 13% 22% 18% 8% 1	460
	11th to 20th	Day	36% 13% 17% 20% 12% 2	460
	21st to end	Day	39% 13% 20% 19% 8% 1	506
April	1st to 10th	Day	36% 14% 21% 19% 8% 2	460
	11th to 20th	Day	27% 15% 27% 18% 11% 3	452
	21st to end	Day	30% 16% 24% 18% 10% 2	460
May	1st to 10th	Day	23% 10% 29% 26% 10% 2	463
	11th to 20th	Day	26% 7% 22% 26% 14% 5%	488
	21st to end	Day	30% 11% 22% 23% 10% 4	529
June	1st to 10th	Day	25% 12% 26% 25% 9% 2	670
	11th to 20th	Day	29% 11% 26% 25% 7% 2	680
	21st to end	Day	20% 10% 25% 28% 15% 3	680
July	1st to 10th	Day	17% 6% 27% 33% 14% 3	671
	11th to 20th	Day	11% 8% 24% 37% 15% 5%	663
	21st to end	Day	11% 6% 19% 38% 19% 8%	531
August	1st to 10th	Day	14% 5% 18% 33% 18% 11%	487
	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% 17% 19% 16% 9%	186
	11th to 20th	Day	52% 4 15% 10% 12% 7%	180
	21st to end	Day	46% 7% 22% 8% 12% 6%	180
December	1st to 10th	Day	47% 9% 17% 11% 11% 6%	180
	11th to 20th	Day	48% 12% 16% 15% 8% 1	180
	21st to end	Day	49% 9% 19% 18% 5% 1	198
January	1st to 10th	Night	51% 11% 14% 15% 9% 1	850
	11th to 20th	Night	46% 9% 13% 21% 11%	824
	21st to end	Night	43% 9% 16% 21% 10% 1	836
February	1st to 10th	Night	44% 11% 18% 21% 6% 1	760
	11th to 20th	Night	42% 8% 19% 22% 8%	744
	21st to end	Night	38% 10% 20% 22% 9% 1	628
March	1st to 10th	Night	33% 11% 17% 23% 14% 1	760
	11th to 20th	Night	40% 7% 18% 21% 13% 1	760
	21st to end	Night	40% 8% 16% 24% 10% 2	836
April	1st to 10th	Night	36% 8% 16% 27% 12% 1	760
	11th to 20th	Night	29% 9% 20% 25% 15% 1	692
	21st to end	Night	35% 7% 14% 29% 13% 1	489
May	1st to 10th	Night	24% 6% 13% 31% 23% 2	380
	11th to 20th	Night	20% 3 10% 29% 33% 4	374
	21st to end	Night	26% 3 10% 31% 27% 3	411
June	1st to 10th	Night	24% 6% 14% 30% 22% 4	380
	11th to 20th	Night	27% 6% 14% 29% 20% 4	380
	21st to end	Night	20% 3 9% 31% 32% 5%	380
July	1st to 10th	Night	14% 2 10% 29% 41% 3	370
	11th to 20th	Night	11% 4 7% 30% 40% 8%	368
	21st to end	Night	9% 1 5% 27% 50% 8%	416
August	1st to 10th	Night	14% 1 4 21% 46% 15%	378
	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	49% 8% 17% 21% 5%	754
	11th to 20th	Night	48% 7% 17% 16% 10% 1	760
	21st to end	Night	47% 9% 16% 16% 11% 2	760
December	1st to 10th	Night	38% 8% 19% 24% 11% 1	760
	11th to 20th	Night	50% 10% 19% 17% 3 1	823
	21st to end	Night	52% 9% 20% 15% 4	935

Page generated at 2024-11-01 19:47:43. Version ac07

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