Whitemud Lake Gravel Pit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whitemud Lake Gravel Pit clear sky chart from 2005-11-06 to 2026-01-17.

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	9% 9% 3 9% 6% 5% 5% 4 7% 8% 33%	132426
	Night	8% 9% 4 10% 6% 6% 6% 4 7% 8% 33%	127966
Transparency	Day	47% 5% 17% 23% 7%	132123
	Night	48% 4 16% 22% 8% 1	127849
Seeing	Day	14% 8% 27% 29% 17% 5%	17461
	Night	13% 6% 29% 35% 16% 2	26096

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	4 13% 6% 14% 9% 7% 6% 5% 7% 7% 21%	3249
	11th to 20th	Day	3 7% 4 12% 8% 7% 7% 8% 9% 9% 26%	3201
	21st to end	Day	6% 12% 4 11% 6% 5% 6% 4 7% 8% 30%	3611
February	1st to 10th	Day	7% 13% 4 10% 9% 7% 9% 6% 7% 8% 21%	1600
	11th to 20th	Day	6% 10% 5% 14% 6% 6% 6% 4 9% 8% 26%	1704
	21st to end	Day	3 12% 5% 9% 9% 7% 8% 6% 8% 8% 24%	1495
March	1st to 10th	Day	5% 9% 5% 12% 8% 6% 8% 6% 7% 9% 26%	4518
	11th to 20th	Day	5% 11% 4 13% 8% 6% 5% 4 6% 9% 30%	4996
	21st to end	Day	10% 14% 5% 16% 6% 4 4 4 6% 8% 23%	5516
April	1st to 10th	Day	7% 13% 4 9% 7% 6% 5% 5% 5% 8% 30%	2535
	11th to 20th	Day	10% 11% 3 8% 7% 6% 5% 4 6% 8% 31%	2570
	21st to end	Day	11% 11% 4 10% 6% 6% 6% 5% 7% 7% 28%	2615
May	1st to 10th	Day	12% 7% 3 8% 6% 6% 5% 5% 6% 6% 36%	6723
	11th to 20th	Day	15% 13% 3 8% 6% 5% 5% 4 5% 7% 28%	6734
	21st to end	Day	9% 8% 3 8% 5% 5% 5% 4 7% 8% 38%	7405
June	1st to 10th	Day	14% 7% 3 8% 5% 6% 7% 5% 7% 8% 31%	3000
	11th to 20th	Day	21% 9% 4 8% 6% 5% 6% 4 6% 8% 22%	3147
	21st to end	Day	10% 7% 3 7% 5% 6% 6% 5% 7% 9% 34%	3200
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 6% 5% 7% 10% 42%	7058
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 9% 42%	6780
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 6% 9% 42%	7376
August	1st to 10th	Day	13% 7% 2 6% 4 5% 4 4 6% 7% 43%	4782
	11th to 20th	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 40%	4281
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 43%	4664
September	1st to 10th	Day	10% 8% 3 8% 4 4 4 4 6% 7% 42%	2569
	11th to 20th	Day	13% 8% 2 6% 5% 4 5% 3 6% 8% 40%	2200
	21st to end	Day	8% 7% 3 7% 5% 6% 5% 4 6% 8% 42%	2200
October	1st to 10th	Day	8% 10% 3 10% 5% 5% 4 4 6% 9% 36%	3346
	11th to 20th	Day	12% 10% 4 7% 4 4 5% 4 5% 8% 36%	3006
	21st to end	Day	8% 12% 5% 10% 6% 5% 4 4 6% 6% 33%	3073
November	1st to 10th	Day	10% 13% 6% 10% 7% 5% 6% 3 6% 7% 27%	1648
	11th to 20th	Day	7% 11% 4 14% 7% 5% 6% 4 6% 8% 28%	1507
	21st to end	Day	5% 11% 5% 14% 8% 5% 5% 4 7% 8% 27%	1470
December	1st to 10th	Day	7% 12% 5% 13% 8% 8% 7% 6% 8% 8% 18%	2360
	11th to 20th	Day	9% 14% 5% 11% 7% 7% 6% 5% 6% 7% 23%	2712
	21st to end	Day	4 7% 3 11% 9% 8% 7% 5% 7% 8% 31%	3575
January	1st to 10th	Night	4 11% 6% 16% 9% 8% 7% 6% 6% 8% 20%	6916
	11th to 20th	Night	3 9% 4 11% 7% 6% 7% 5% 5% 7% 37%	6830
	21st to end	Night	6% 11% 4 11% 7% 6% 5% 4 6% 8% 32%	7389
February	1st to 10th	Night	5% 11% 4 11% 8% 7% 8% 5% 8% 7% 25%	2800
	11th to 20th	Night	5% 10% 4 11% 7% 7% 7% 4 6% 7% 30%	2582
	21st to end	Night	3 9% 3 10% 8% 8% 6% 7% 8% 8% 31%	2135
March	1st to 10th	Night	3 9% 5% 11% 7% 7% 7% 5% 9% 10% 29%	5376
	11th to 20th	Night	5% 9% 4 12% 7% 6% 6% 5% 7% 9% 32%	5002
	21st to end	Night	10% 16% 6% 14% 6% 5% 4 4 5% 6% 24%	5456
April	1st to 10th	Night	7% 10% 4 8% 7% 6% 5% 5% 6% 8% 34%	1865
	11th to 20th	Night	8% 10% 3 9% 7% 6% 7% 4 7% 7% 33%	1781
	21st to end	Night	10% 11% 3 8% 5% 5% 6% 4 7% 7% 34%	1785
May	1st to 10th	Night	13% 8% 3 7% 4 4 4 4 6% 8% 40%	3236
	11th to 20th	Night	14% 11% 3 9% 6% 6% 6% 4 5% 7% 28%	3159
	21st to end	Night	11% 8% 2 6% 5% 5% 5% 4 8% 10% 34%	3470
June	1st to 10th	Night	16% 6% 3 9% 7% 5% 4 4 6% 8% 33%	1400
	11th to 20th	Night	17% 9% 2 7% 6% 5% 5% 6% 8% 10% 25%	1249
	21st to end	Night	10% 6% 3 7% 6% 6% 4 4 6% 7% 41%	1200
July	1st to 10th	Night	7% 4 2 6% 5% 5% 5% 4 8% 9% 45%	2899
	11th to 20th	Night	8% 6% 3 7% 5% 5% 5% 5% 7% 8% 42%	3180
	21st to end	Night	12% 6% 2 6% 4 3 4 4 7% 8% 45%	3467
August	1st to 10th	Night	10% 6% 2 6% 5% 4 6% 3 7% 7% 43%	2367
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 4 7% 9% 39%	2773
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 6% 7% 46%	3245
September	1st to 10th	Night	12% 6% 2 6% 4 3 4 4 5% 8% 46%	1829
	11th to 20th	Night	11% 6% 2 6% 4 3 3 3 5% 9% 47%	2200
	21st to end	Night	9% 6% 2 6% 5% 4 5% 4 6% 8% 44%	2200
October	1st to 10th	Night	7% 7% 3 8% 6% 5% 6% 3 7% 9% 38%	3846
	11th to 20th	Night	9% 8% 4 8% 5% 5% 6% 4 7% 9% 37%	4141
	21st to end	Night	8% 9% 4 10% 5% 5% 6% 5% 8% 8% 32%	4694
November	1st to 10th	Night	12% 14% 6% 10% 7% 5% 4 4 5% 6% 27%	2870
	11th to 20th	Night	7% 13% 5% 12% 8% 6% 6% 4 6% 7% 26%	3111
	21st to end	Night	5% 11% 5% 14% 9% 6% 5% 4 6% 7% 27%	3150
December	1st to 10th	Night	9% 15% 6% 14% 8% 6% 5% 4 6% 7% 20%	5040
	11th to 20th	Night	7% 15% 5% 13% 8% 7% 6% 5% 7% 7% 18%	5700
	21st to end	Night	3 7% 4 11% 7% 7% 7% 4 7% 9% 35%	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	60% 2 12% 16% 9%	3249
	11th to 20th	Day	51% 5% 14% 14% 16% 1	3222
	21st to end	Day	51% 4 22% 17% 6%	3611
February	1st to 10th	Day	59% 4 12% 16% 10%	1600
	11th to 20th	Day	53% 4 16% 18% 8%	1713
	21st to end	Day	53% 6% 14% 19% 7%	1495
March	1st to 10th	Day	51% 4 18% 20% 7%	4518
	11th to 20th	Day	51% 4 16% 22% 6%	4997
	21st to end	Day	58% 4 12% 21% 5%	5516
April	1st to 10th	Day	50% 5% 15% 20% 9% 1	2535
	11th to 20th	Day	50% 4 13% 22% 10%	2570
	21st to end	Day	51% 5% 12% 24% 8% 1	2615
May	1st to 10th	Day	46% 4 10% 24% 15% 1	6723
	11th to 20th	Day	54% 5% 9% 24% 7%	6738
	21st to end	Day	42% 5% 20% 21% 10% 1	7406
June	1st to 10th	Day	49% 4 14% 23% 8% 1	3000
	11th to 20th	Day	58% 5% 14% 18% 5%	3147
	21st to end	Day	45% 6% 19% 23% 6% 1	3200
July	1st to 10th	Day	35% 6% 23% 28% 7%	6982
	11th to 20th	Day	36% 5% 17% 32% 10%	6699
	21st to end	Day	38% 6% 23% 28% 5%	7169
August	1st to 10th	Day	39% 5% 22% 31% 3	4764
	11th to 20th	Day	37% 6% 25% 24% 7%	4323
	21st to end	Day	36% 4 30% 25% 4	4663
September	1st to 10th	Day	41% 4 19% 27% 7% 1	2569
	11th to 20th	Day	42% 3 21% 28% 6%	2200
	21st to end	Day	39% 5% 19% 26% 10% 2	2200
October	1st to 10th	Day	46% 3 22% 24% 4	3346
	11th to 20th	Day	46% 3 15% 28% 7%	3006
	21st to end	Day	51% 4 17% 25% 3	3073
November	1st to 10th	Day	55% 4 14% 19% 7%	1648
	11th to 20th	Day	53% 5% 19% 18% 6%	1507
	21st to end	Day	54% 5% 16% 19% 5% 1	1470
December	1st to 10th	Day	60% 6% 17% 12% 5%	2360
	11th to 20th	Day	59% 4 17% 16% 4	2714
	21st to end	Day	49% 4 10% 28% 8% 1	3575
January	1st to 10th	Night	61% 3 12% 14% 9% 1	6916
	11th to 20th	Night	46% 3 14% 19% 15% 2	6871
	21st to end	Night	50% 3 23% 18% 5%	7389
February	1st to 10th	Night	55% 4 13% 18% 10% 1	2800
	11th to 20th	Night	53% 4 12% 20% 10% 1	2583
	21st to end	Night	46% 5% 14% 24% 10% 1	2135
March	1st to 10th	Night	47% 4 18% 23% 7%	5376
	11th to 20th	Night	47% 5% 17% 23% 8%	5002
	21st to end	Night	60% 3 11% 16% 10%	5456
April	1st to 10th	Night	47% 4 13% 22% 13% 1	1865
	11th to 20th	Night	49% 3 10% 22% 13% 3	1781
	21st to end	Night	46% 4 12% 23% 13% 1	1785
May	1st to 10th	Night	41% 3 10% 26% 16% 3	3236
	11th to 20th	Night	54% 4 12% 23% 7% 1	3159
	21st to end	Night	44% 4 20% 23% 8% 1	3470
June	1st to 10th	Night	49% 3 13% 23% 10% 1	1400
	11th to 20th	Night	51% 6% 18% 18% 6%	1249
	21st to end	Night	41% 4 22% 25% 7% 1	1200
July	1st to 10th	Night	34% 6% 24% 22% 14%	2866
	11th to 20th	Night	38% 4 16% 33% 8% 1	3138
	21st to end	Night	36% 4 23% 31% 5%	3369
August	1st to 10th	Night	39% 4 21% 34% 2	2360
	11th to 20th	Night	40% 6% 21% 24% 8%	2797
	21st to end	Night	36% 4 25% 29% 6%	3245
September	1st to 10th	Night	38% 3 21% 30% 7% 2	1829
	11th to 20th	Night	36% 3 18% 32% 11% 1	2200
	21st to end	Night	38% 4 16% 28% 11% 2	2200
October	1st to 10th	Night	40% 4 21% 27% 7%	3846
	11th to 20th	Night	42% 3 16% 32% 7%	4141
	21st to end	Night	46% 5% 22% 22% 5%	4694
November	1st to 10th	Night	58% 3 11% 22% 6%	2870
	11th to 20th	Night	56% 6% 14% 17% 6%	3111
	21st to end	Night	55% 4 17% 18% 5% 1	3150
December	1st to 10th	Night	63% 5% 12% 14% 5% 1	5040
	11th to 20th	Night	63% 4 16% 12% 4	5697
	21st to end	Night	45% 4 14% 23% 12% 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	11% 4 37% 25% 19% 4	220
	11th to 20th	Day	9% 9% 38% 26% 12% 5%	212
	21st to end	Day	10% 11% 39% 29% 8% 4	220
February	1st to 10th	Day	12% 9% 38% 27% 13% 3	200
	11th to 20th	Day	11% 7% 31% 31% 18% 3	275
	21st to end	Day	7% 11% 35% 28% 14% 4	259
March	1st to 10th	Day	10% 10% 34% 31% 13% 2	500
	11th to 20th	Day	11% 7% 35% 30% 12% 4	500
	21st to end	Day	18% 6% 30% 31% 13% 2	550
April	1st to 10th	Day	11% 11% 37% 27% 12% 3	500
	11th to 20th	Day	15% 9% 30% 31% 11% 4	492
	21st to end	Day	17% 10% 31% 28% 12% 2	515
May	1st to 10th	Day	15% 12% 24% 27% 19% 4	703
	11th to 20th	Day	14% 7% 24% 30% 18% 6%	725
	21st to end	Day	17% 6% 22% 28% 20% 7%	789
June	1st to 10th	Day	17% 8% 28% 32% 12% 3	730
	11th to 20th	Day	22% 6% 20% 26% 20% 6%	877
	21st to end	Day	12% 5% 19% 32% 24% 9%	930
July	1st to 10th	Day	14% 4 17% 34% 22% 8%	841
	11th to 20th	Day	13% 6% 19% 30% 22% 9%	718
	21st to end	Day	10% 4 19% 31% 27% 8%	794
August	1st to 10th	Day	15% 4 16% 30% 23% 12%	677
	11th to 20th	Day	11% 6% 28% 30% 20% 5%	517
	21st to end	Day	13% 6% 23% 30% 20% 8%	583
September	1st to 10th	Day	17% 8% 28% 23% 18% 6%	530
	11th to 20th	Day	17% 8% 24% 30% 17% 3	530
	21st to end	Day	12% 15% 33% 25% 13% 3	530
October	1st to 10th	Day	16% 9% 27% 31% 15% 3	380
	11th to 20th	Day	17% 9% 37% 27% 10% 1	330
	21st to end	Day	21% 11% 34% 21% 10% 2	363
November	1st to 10th	Day	18% 8% 34% 30% 8% 2	330
	11th to 20th	Day	11% 9% 45% 26% 8% 2	239
	21st to end	Day	8% 8% 38% 30% 11% 5%	220
December	1st to 10th	Day	13% 8% 40% 24% 12% 4	220
	11th to 20th	Day	13% 9% 39% 30% 8% 1	220
	21st to end	Day	10% 5% 29% 31% 19% 6%	242
January	1st to 10th	Night	14% 7% 33% 33% 12% 2	1050
	11th to 20th	Night	10% 7% 36% 34% 11% 1	1031
	21st to end	Night	13% 10% 38% 29% 9% 2	1070
February	1st to 10th	Night	11% 7% 28% 34% 17% 3	800
	11th to 20th	Night	9% 4 30% 40% 15% 1	784
	21st to end	Night	6% 5% 30% 37% 19% 3	660
March	1st to 10th	Night	9% 6% 30% 40% 13% 3	800
	11th to 20th	Night	12% 6% 30% 36% 15% 2	800
	21st to end	Night	15% 5% 27% 35% 15% 3	880
April	1st to 10th	Night	13% 5% 26% 35% 17% 4	665
	11th to 20th	Night	13% 5% 31% 36% 13% 2	593
	21st to end	Night	17% 6% 24% 34% 18% 2	600
May	1st to 10th	Night	13% 6% 23% 36% 18% 4	430
	11th to 20th	Night	15% 5% 21% 37% 20% 3	394
	21st to end	Night	18% 6% 17% 34% 24% 2	433
June	1st to 10th	Night	18% 7% 18% 39% 17% 2	400
	11th to 20th	Night	21% 3 18% 34% 22% 3	400
	21st to end	Night	13% 2 17% 40% 25% 4	400
July	1st to 10th	Night	13% 3 16% 42% 25% 1	390
	11th to 20th	Night	10% 4 20% 42% 22% 2	388
	21st to end	Night	11% 4 14% 38% 28% 5%	438
August	1st to 10th	Night	10% 3 14% 35% 31% 7%	398
	11th to 20th	Night	10% 4 20% 38% 25% 3	514
	21st to end	Night	14% 4 21% 37% 24% 1	660
September	1st to 10th	Night	16% 5% 20% 32% 26% 2	600
	11th to 20th	Night	15% 5% 17% 43% 19% 2	800
	21st to end	Night	13% 6% 30% 35% 16% 1	800
October	1st to 10th	Night	14% 5% 29% 36% 15% 2	800
	11th to 20th	Night	13% 5% 34% 34% 11% 3	800
	21st to end	Night	14% 8% 34% 30% 13% 1	938
November	1st to 10th	Night	19% 6% 31% 30% 11% 2	1025
	11th to 20th	Night	14% 8% 36% 30% 11% 3	1050
	21st to end	Night	10% 6% 40% 32% 11% 2	1050
December	1st to 10th	Night	13% 8% 35% 29% 12% 3	1050
	11th to 20th	Night	12% 9% 35% 32% 11% 1	1050
	21st to end	Night	10% 5% 32% 34% 16% 3	1155

Page generated at 2026-01-13 23:14:25. Version ac07

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