Aldergrove Lake Regional Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aldergrove Lake Regional Park clear sky chart from 2005-11-06 to 2024-03-18.

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% 5% 3 4 4 4 6% 30%	78261
	Night	30% 9% 3 6% 5% 3 4 4 4 5% 28%	81471
Transparency	Day	59% 2 13% 17% 7% 1	77973
	Night	61% 2 12% 16% 7% 2	81339
Seeing	Day	29% 8% 21% 24% 13% 4	14311
	Night	35% 5% 14% 24% 18% 3	22805

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 6% 6% 3 4 3 4 4 11%	2219
	11th to 20th	Day	30% 11% 4 7% 5% 3 3 2 3 5% 26%	2264
	21st to end	Day	53% 11% 3 6% 4 2 3 2 2 3 11%	2798
February	1st to 10th	Day	35% 11% 4 7% 5% 3 5% 3 4 5% 17%	1710
	11th to 20th	Day	32% 10% 4 7% 5% 4 4 3 4 5% 22%	1665
	21st to end	Day	28% 15% 4 7% 5% 4 4 3 4 4 21%	1451
March	1st to 10th	Day	30% 14% 4 6% 6% 3 4 4 5% 5% 19%	1939
	11th to 20th	Day	32% 12% 4 7% 6% 3 4 3 3 5% 21%	2059
	21st to end	Day	30% 11% 4 9% 6% 3 6% 4 4 5% 19%	2250
April	1st to 10th	Day	29% 11% 4 8% 6% 3 6% 4 5% 5% 19%	2160
	11th to 20th	Day	24% 10% 4 9% 8% 4 6% 4 5% 6% 22%	2191
	21st to end	Day	25% 10% 4 8% 6% 3 4 5% 5% 6% 25%	2407
May	1st to 10th	Day	20% 7% 3 7% 6% 3 5% 5% 5% 6% 33%	2520
	11th to 20th	Day	18% 8% 3 7% 6% 3 5% 5% 5% 8% 32%	2477
	21st to end	Day	22% 9% 4 7% 6% 3 4 4 5% 6% 30%	2723
June	1st to 10th	Day	24% 7% 3 7% 6% 3 5% 4 5% 7% 28%	2700
	11th to 20th	Day	23% 9% 4 7% 6% 3 5% 5% 5% 7% 24%	2700
	21st to end	Day	14% 7% 3 6% 6% 3 6% 5% 6% 7% 37%	2700
July	1st to 10th	Day	13% 5% 2 5% 4 3 4 4 5% 6% 50%	2700
	11th to 20th	Day	10% 5% 2 4 4 3 4 3 4 7% 53%	2700
	21st to end	Day	9% 3 2 2 3 2 3 3 4 6% 64%	2746
August	1st to 10th	Day	11% 4 2 4 3 2 3 3 4 7% 56%	2507
	11th to 20th	Day	8% 4 2 4 3 3 4 4 5% 6% 57%	2298
	21st to end	Day	15% 5% 2 5% 5% 3 4 4 5% 7% 45%	2496
September	1st to 10th	Day	15% 6% 2 5% 5% 3 3 3 4 6% 47%	2160
	11th to 20th	Day	17% 7% 3 7% 6% 3 4 3 4 6% 40%	2160
	21st to end	Day	25% 6% 3 5% 5% 3 4 3 5% 6% 36%	1901
October	1st to 10th	Day	24% 9% 2 7% 5% 3 3 4 4 6% 34%	1800
	11th to 20th	Day	31% 9% 3 6% 6% 3 4 4 5% 6% 24%	1800
	21st to end	Day	35% 8% 3 5% 4 3 4 4 4 6% 24%	1845
November	1st to 10th	Day	41% 8% 4 5% 5% 3 4 4 4 4 17%	1488
	11th to 20th	Day	37% 11% 3 6% 4 3 3 3 4 4 22%	1520
	21st to end	Day	38% 12% 4 6% 4 3 3 4 4 5% 18%	1520
December	1st to 10th	Day	35% 11% 4 6% 4 2 3 4 3 3 25%	1520
	11th to 20th	Day	36% 14% 4 6% 5% 3 3 4 4 6% 14%	1725
	21st to end	Day	39% 14% 5% 8% 6% 3 3 3 3 4 11%	2442
January	1st to 10th	Night	42% 14% 5% 7% 5% 3 3 3 3 3 13%	4726
	11th to 20th	Night	33% 8% 2 4 4 2 3 3 5% 8% 27%	4631
	21st to end	Night	50% 12% 4 5% 4 2 3 2 2 3 13%	4853
February	1st to 10th	Night	37% 10% 3 7% 5% 3 3 3 3 5% 20%	2470
	11th to 20th	Night	31% 13% 3 7% 5% 3 4 3 3 4 24%	2402
	21st to end	Night	30% 12% 4 5% 5% 2 4 4 3 5% 25%	2003
March	1st to 10th	Night	30% 11% 3 6% 5% 3 4 4 4 5% 24%	2237
	11th to 20th	Night	34% 9% 3 6% 5% 3 4 4 4 5% 22%	2066
	21st to end	Night	34% 11% 4 7% 5% 3 4 4 4 5% 19%	2106
April	1st to 10th	Night	30% 10% 3 6% 6% 3 5% 5% 5% 5% 22%	1800
	11th to 20th	Night	25% 10% 3 7% 6% 4 5% 5% 4 6% 26%	1718
	21st to end	Night	28% 9% 4 7% 6% 3 5% 5% 4 6% 24%	1552
May	1st to 10th	Night	19% 8% 3 5% 5% 3 5% 4 5% 6% 38%	1440
	11th to 20th	Night	15% 7% 3 6% 6% 3 6% 6% 7% 7% 34%	1416
	21st to end	Night	18% 6% 4 6% 5% 3 6% 4 5% 8% 35%	1549
June	1st to 10th	Night	22% 6% 3 8% 5% 5% 5% 5% 4 6% 31%	1260
	11th to 20th	Night	19% 10% 5% 8% 6% 4 4 7% 6% 7% 26%	1260
	21st to end	Night	13% 6% 3 6% 6% 3 4 4 4 7% 44%	1260
July	1st to 10th	Night	11% 4 3 6% 5% 3 3 3 4 4 53%	1260
	11th to 20th	Night	10% 5% 2 3 4 2 4 2 3 5% 59%	1260
	21st to end	Night	6% 2 1 2 2 2 3 4 4 5% 68%	1567
August	1st to 10th	Night	9% 3 2 3 3 1 3 4 4 6% 61%	1432
	11th to 20th	Night	6% 3 2 3 3 2 2 3 5% 8% 62%	1599
	21st to end	Night	10% 5% 3 5% 5% 3 4 5% 6% 9% 46%	1859
September	1st to 10th	Night	10% 3 2 3 5% 3 5% 5% 4 6% 54%	1800
	11th to 20th	Night	20% 5% 2 5% 5% 2 4 3 4 7% 42%	1800
	21st to end	Night	21% 6% 3 5% 5% 3 4 3 4 5% 40%	2055
October	1st to 10th	Night	22% 7% 3 5% 6% 3 5% 4 4 5% 38%	2160
	11th to 20th	Night	30% 7% 3 5% 4 3 4 4 4 6% 30%	2160
	21st to end	Night	33% 7% 2 6% 4 2 4 4 4 5% 29%	2509
November	1st to 10th	Night	40% 9% 3 6% 5% 3 4 4 4 4 19%	2590
	11th to 20th	Night	39% 8% 3 6% 5% 2 3 3 3 3 23%	2660
	21st to end	Night	38% 10% 4 6% 6% 3 4 3 3 4 19%	2660
December	1st to 10th	Night	32% 9% 3 5% 5% 3 4 4 5% 5% 25%	2660
	11th to 20th	Night	43% 13% 4 7% 5% 3 3 3 3 3 14%	3477
	21st to end	Night	40% 13% 4 7% 5% 3 3 3 3 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	81% 1 6% 8% 3 1	2219
	11th to 20th	Day	65% 2 7% 13% 8% 5%	2285
	21st to end	Day	81% 1 6% 8% 3 1	2798
February	1st to 10th	Day	72% 2 9% 8% 6% 2	1710
	11th to 20th	Day	68% 2 9% 12% 8% 2	1674
	21st to end	Day	69% 2 10% 11% 6% 2	1451
March	1st to 10th	Day	70% 2 11% 12% 5% 1	1939
	11th to 20th	Day	71% 2 7% 14% 5% 1	2059
	21st to end	Day	72% 2 10% 13% 2	2250
April	1st to 10th	Day	70% 3 13% 11% 3	2160
	11th to 20th	Day	67% 2 8% 14% 8% 2	2191
	21st to end	Day	64% 2 12% 12% 8% 1	2407
May	1st to 10th	Day	57% 3 14% 18% 8% 1	2520
	11th to 20th	Day	55% 3 18% 18% 7%	2480
	21st to end	Day	60% 4 16% 18% 3	2724
June	1st to 10th	Day	59% 3 16% 16% 5% 2	2700
	11th to 20th	Day	65% 2 16% 12% 4	2700
	21st to end	Day	51% 2 18% 19% 8% 2	2700
July	1st to 10th	Day	40% 2 17% 26% 12% 2	2626
	11th to 20th	Day	36% 2 18% 31% 10% 2	2619
	21st to end	Day	25% 2 19% 37% 15% 3	2593
August	1st to 10th	Day	33% 3 21% 30% 12% 2	2490
	11th to 20th	Day	30% 3 21% 30% 14% 2	2298
	21st to end	Day	41% 2 20% 28% 7% 1	2496
September	1st to 10th	Day	41% 3 16% 24% 12% 4	2160
	11th to 20th	Day	50% 2 12% 19% 15% 2	2160
	21st to end	Day	52% 3 15% 18% 11% 1	1901
October	1st to 10th	Day	53% 2 15% 18% 11% 1	1800
	11th to 20th	Day	63% 3 12% 17% 4 1	1800
	21st to end	Day	63% 3 11% 14% 9% 1	1845
November	1st to 10th	Day	73% 2 10% 11% 4 1	1488
	11th to 20th	Day	71% 2 8% 11% 6% 2	1520
	21st to end	Day	70% 2 8% 11% 8% 2	1520
December	1st to 10th	Day	67% 3 8% 11% 10% 1	1520
	11th to 20th	Day	73% 2 8% 12% 4 2	1728
	21st to end	Day	80% 1 8% 7% 3 1	2442
January	1st to 10th	Night	80% 1 5% 11% 2 1	4726
	11th to 20th	Night	59% 2 8% 15% 10% 5%	4672
	21st to end	Night	80% 1 6% 8% 3 1	4853
February	1st to 10th	Night	71% 2 10% 10% 5% 2	2470
	11th to 20th	Night	68% 2 8% 12% 7% 2	2404
	21st to end	Night	64% 2 9% 16% 7% 2	2003
March	1st to 10th	Night	64% 2 12% 15% 6% 1	2237
	11th to 20th	Night	66% 3 10% 14% 6% 1	2067
	21st to end	Night	70% 3 15% 10% 2	2106
April	1st to 10th	Night	65% 3 14% 15% 3	1800
	11th to 20th	Night	62% 2 10% 16% 8% 2	1718
	21st to end	Night	65% 2 12% 13% 8% 1	1552
May	1st to 10th	Night	50% 2 19% 20% 8% 1	1440
	11th to 20th	Night	49% 4 21% 18% 7%	1416
	21st to end	Night	51% 3 20% 21% 5%	1549
June	1st to 10th	Night	57% 2 17% 16% 5% 3	1260
	11th to 20th	Night	59% 4 18% 16% 4	1260
	21st to end	Night	43% 2 23% 21% 8% 3	1260
July	1st to 10th	Night	38% 3 15% 27% 14% 4	1225
	11th to 20th	Night	32% 2 18% 33% 14% 1	1218
	21st to end	Night	19% 2 15% 36% 22% 5%	1480
August	1st to 10th	Night	26% 2 18% 32% 18% 3	1424
	11th to 20th	Night	22% 3 25% 31% 14% 6%	1599
	21st to end	Night	37% 3 18% 30% 11% 1	1859
September	1st to 10th	Night	34% 3 18% 28% 14% 4	1800
	11th to 20th	Night	46% 2 14% 19% 16% 4	1800
	21st to end	Night	49% 3 15% 20% 10% 2	2055
October	1st to 10th	Night	52% 2 14% 21% 10% 1	2160
	11th to 20th	Night	59% 2 14% 17% 7% 1	2160
	21st to end	Night	61% 2 11% 16% 9%	2509
November	1st to 10th	Night	72% 1 10% 12% 4 1	2590
	11th to 20th	Night	70% 2 10% 10% 6% 2	2660
	21st to end	Night	72% 2 8% 9% 8% 2	2660
December	1st to 10th	Night	63% 4 10% 13% 9% 1	2660
	11th to 20th	Night	78% 1 8% 6% 4 2	3473
	21st to end	Night	77% 1 7% 10% 4 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	46% 7% 22% 11% 9% 4	180
	11th to 20th	Day	50% 9% 14% 16% 9% 3	180
	21st to end	Day	48% 8% 15% 17% 10% 2	202
February	1st to 10th	Day	46% 11% 17% 16% 7% 3	370
	11th to 20th	Day	40% 10% 22% 17% 9% 2	365
	21st to end	Day	41% 11% 26% 13% 8% 2	325
March	1st to 10th	Day	39% 10% 20% 20% 9% 2	460
	11th to 20th	Day	37% 10% 19% 22% 11% 2	449
	21st to end	Day	42% 10% 19% 18% 9% 2	462
April	1st to 10th	Day	37% 10% 20% 20% 11% 2	420
	11th to 20th	Day	29% 13% 24% 19% 10% 4	412
	21st to end	Day	29% 11% 25% 21% 10% 3	420
May	1st to 10th	Day	23% 9% 25% 30% 11% 3	423
	11th to 20th	Day	24% 7% 19% 28% 16% 6%	448
	21st to end	Day	25% 9% 26% 22% 14% 5%	485
June	1st to 10th	Day	25% 10% 25% 26% 11% 3	630
	11th to 20th	Day	27% 9% 27% 26% 8% 2	630
	21st to end	Day	20% 7% 24% 30% 16% 4	630
July	1st to 10th	Day	18% 4 25% 34% 15% 4	621
	11th to 20th	Day	13% 6% 24% 36% 17% 5%	618
	21st to end	Day	10% 4 20% 37% 21% 9%	492
August	1st to 10th	Day	15% 4 17% 32% 20% 11%	447
	11th to 20th	Day	10% 3 17% 35% 24% 11%	437
	21st to end	Day	18% 7% 22% 30% 16% 8%	495
September	1st to 10th	Day	21% 7% 23% 26% 17% 6%	450
	11th to 20th	Day	22% 6% 17% 30% 19% 5%	450
	21st to end	Day	26% 6% 22% 22% 18% 5%	450
October	1st to 10th	Day	33% 7% 16% 20% 19% 5%	450
	11th to 20th	Day	37% 6% 15% 19% 17% 6%	450
	21st to end	Day	41% 9% 19% 16% 11% 4	362
November	1st to 10th	Day	44% 11% 19% 14% 11%	180
	11th to 20th	Day	48% 4 16% 11% 14% 7%	180
	21st to end	Day	47% 5% 21% 9% 11% 7%	180
December	1st to 10th	Day	50% 6% 17% 11% 9% 7%	180
	11th to 20th	Day	52% 9% 12% 16% 8% 2	180
	21st to end	Day	52% 5% 18% 19% 6%	198
January	1st to 10th	Night	54% 6% 14% 16% 8% 1	850
	11th to 20th	Night	47% 7% 13% 21% 11% 1	830
	21st to end	Night	46% 6% 15% 21% 12% 1	836
February	1st to 10th	Night	45% 9% 18% 20% 7% 1	760
	11th to 20th	Night	43% 8% 17% 23% 9%	744
	21st to end	Night	40% 8% 20% 21% 10% 2	628
March	1st to 10th	Night	37% 7% 19% 22% 14% 1	760
	11th to 20th	Night	42% 4 19% 22% 11% 1	752
	21st to end	Night	42% 5% 15% 24% 11% 3	792
April	1st to 10th	Night	38% 5% 15% 26% 14% 2	720
	11th to 20th	Night	32% 6% 19% 24% 17% 2	650
	21st to end	Night	35% 4 15% 29% 15% 2	472
May	1st to 10th	Night	24% 4 12% 33% 24% 3	360
	11th to 20th	Night	21% 3 7% 29% 35% 5%	354
	21st to end	Night	23% 4 6% 34% 28% 5%	389
June	1st to 10th	Night	26% 2 14% 28% 27% 4	360
	11th to 20th	Night	24% 5% 13% 33% 21% 4	360
	21st to end	Night	17% 2 9% 32% 35% 5%	360
July	1st to 10th	Night	15% 2 9% 28% 43% 3	350
	11th to 20th	Night	13% 4 7% 30% 39% 8%	348
	21st to end	Night	7% 2 6% 25% 51% 9%	394
August	1st to 10th	Night	14% 1 4 21% 46% 15%	358
	11th to 20th	Night	10% 1 4 25% 47% 13%	531
	21st to end	Night	14% 3 8% 29% 39% 7%	671
September	1st to 10th	Night	15% 2 9% 38% 30% 7%	720
	11th to 20th	Night	23% 3 10% 22% 34% 8%	720
	21st to end	Night	26% 4 12% 28% 26% 3	720
October	1st to 10th	Night	28% 4 12% 28% 25% 5%	720
	11th to 20th	Night	37% 4 13% 24% 18% 4	720
	21st to end	Night	41% 6% 16% 24% 11% 2	792
November	1st to 10th	Night	48% 5% 18% 23% 6% 1	740
	11th to 20th	Night	48% 6% 16% 18% 10% 2	760
	21st to end	Night	48% 7% 13% 18% 12% 2	760
December	1st to 10th	Night	40% 6% 17% 25% 11% 1	760
	11th to 20th	Night	53% 7% 17% 17% 5% 1	829
	21st to end	Night	52% 8% 20% 16% 4	935

Page generated at 2024-03-15 11:01:45. Version ac07

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