Whitecourt
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whitecourt clear sky chart from 2005-11-06 to 2026-01-02.

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% 34%	131661
	Night	8% 10% 4 10% 6% 5% 5% 4 6% 8% 32%	128368
Transparency	Day	45% 8% 17% 21% 8% 1	131348
	Night	47% 8% 16% 20% 8% 1	128258
Seeing	Day	15% 12% 29% 27% 13% 4	17696
	Night	13% 10% 29% 33% 13% 1	26117

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 14% 5% 13% 7% 6% 8% 5% 6% 7% 25%	2725
	11th to 20th	Day	4 9% 3 9% 6% 6% 5% 6% 7% 9% 35%	3002
	21st to end	Day	6% 11% 4 7% 6% 5% 5% 5% 6% 9% 35%	3894
February	1st to 10th	Day	7% 11% 4 12% 7% 7% 7% 4 8% 9% 24%	1600
	11th to 20th	Day	4 12% 6% 10% 6% 6% 6% 4 8% 8% 30%	1605
	21st to end	Day	5% 12% 5% 14% 8% 7% 5% 4 7% 7% 26%	1615
March	1st to 10th	Day	3 10% 5% 12% 8% 7% 6% 4 8% 9% 28%	4518
	11th to 20th	Day	7% 13% 4 11% 6% 5% 5% 3 5% 7% 34%	4794
	21st to end	Day	9% 15% 6% 16% 6% 5% 5% 4 5% 6% 22%	5783
April	1st to 10th	Day	8% 13% 4 11% 7% 5% 6% 4 7% 8% 27%	2435
	11th to 20th	Day	9% 12% 3 9% 6% 6% 6% 5% 7% 9% 29%	2570
	21st to end	Day	10% 10% 3 10% 6% 6% 6% 5% 8% 7% 29%	2687
May	1st to 10th	Day	11% 9% 3 8% 5% 5% 5% 4 6% 8% 36%	6540
	11th to 20th	Day	11% 11% 4 10% 7% 6% 6% 5% 7% 7% 25%	6734
	21st to end	Day	10% 7% 3 9% 5% 6% 5% 5% 7% 9% 35%	7405
June	1st to 10th	Day	16% 8% 3 8% 6% 5% 5% 5% 7% 7% 30%	3170
	11th to 20th	Day	17% 10% 3 9% 6% 6% 6% 5% 7% 8% 23%	3200
	21st to end	Day	10% 6% 3 7% 6% 6% 6% 5% 8% 10% 35%	3200
July	1st to 10th	Day	8% 5% 2 5% 4 5% 5% 5% 8% 10% 44%	7240
	11th to 20th	Day	9% 5% 3 7% 5% 5% 5% 4 7% 9% 40%	7103
	21st to end	Day	11% 5% 2 6% 4 4 5% 5% 8% 9% 40%	7376
August	1st to 10th	Day	14% 6% 2 6% 4 4 5% 3 6% 8% 42%	4543
	11th to 20th	Day	11% 6% 2 7% 4 5% 5% 4 7% 9% 40%	4441
	21st to end	Day	13% 5% 2 6% 5% 5% 6% 5% 7% 9% 38%	4664
September	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 5% 6% 8% 41%	2464
	11th to 20th	Day	12% 7% 2 6% 3 4 5% 4 5% 8% 43%	2265
	21st to end	Day	10% 7% 2 7% 5% 5% 5% 5% 6% 8% 39%	2200
October	1st to 10th	Day	10% 9% 4 7% 4 5% 5% 4 7% 8% 37%	3388
	11th to 20th	Day	12% 12% 4 9% 5% 4 4 3 6% 7% 33%	2932
	21st to end	Day	7% 12% 5% 11% 6% 5% 5% 3 6% 8% 34%	3200
November	1st to 10th	Day	12% 14% 5% 10% 6% 4 5% 4 7% 7% 28%	1610
	11th to 20th	Day	7% 13% 4 9% 5% 5% 6% 4 5% 6% 34%	1470
	21st to end	Day	5% 12% 5% 11% 9% 5% 5% 5% 6% 9% 27%	1470
December	1st to 10th	Day	9% 15% 5% 11% 7% 5% 7% 6% 7% 8% 21%	2360
	11th to 20th	Day	8% 15% 4 12% 8% 6% 6% 5% 5% 7% 23%	2400
	21st to end	Day	4 9% 3 8% 5% 6% 4 4 6% 9% 43%	3058
January	1st to 10th	Night	4 11% 5% 15% 8% 6% 6% 5% 6% 6% 28%	7243
	11th to 20th	Night	3 10% 4 10% 7% 6% 6% 5% 7% 7% 35%	6881
	21st to end	Night	6% 15% 4 9% 5% 5% 4 4 7% 8% 33%	7090
February	1st to 10th	Night	6% 13% 5% 11% 8% 7% 6% 5% 5% 8% 26%	2800
	11th to 20th	Night	4 11% 5% 12% 7% 6% 6% 5% 6% 7% 31%	2681
	21st to end	Night	4 11% 5% 11% 6% 6% 6% 6% 7% 7% 31%	2014
March	1st to 10th	Night	3 7% 4 12% 7% 6% 6% 5% 7% 10% 32%	5376
	11th to 20th	Night	5% 11% 4 11% 7% 6% 6% 5% 7% 9% 29%	5205
	21st to end	Night	11% 17% 6% 15% 6% 5% 5% 3 4 5% 22%	5189
April	1st to 10th	Night	8% 12% 4 10% 6% 6% 6% 4 6% 9% 30%	1965
	11th to 20th	Night	11% 12% 4 8% 5% 5% 6% 5% 6% 8% 30%	1781
	21st to end	Night	11% 11% 3 7% 6% 5% 5% 5% 7% 8% 31%	1710
May	1st to 10th	Night	13% 9% 4 8% 5% 4 4 4 5% 7% 37%	3418
	11th to 20th	Night	12% 11% 4 12% 7% 7% 6% 4 6% 7% 23%	3159
	21st to end	Night	13% 7% 3 7% 4 4 5% 3 7% 9% 38%	3470
June	1st to 10th	Night	17% 8% 3 7% 5% 6% 5% 4 5% 7% 33%	1226
	11th to 20th	Night	17% 8% 3 7% 8% 7% 6% 6% 7% 8% 23%	1200
	21st to end	Night	11% 5% 2 8% 7% 6% 7% 6% 7% 8% 33%	1200
July	1st to 10th	Night	9% 5% 2 6% 5% 5% 6% 4 7% 9% 42%	2720
	11th to 20th	Night	12% 6% 2 8% 5% 5% 7% 6% 7% 8% 34%	2854
	21st to end	Night	12% 5% 2 7% 4 5% 5% 4 6% 8% 41%	3467
August	1st to 10th	Night	14% 6% 2 6% 4 4 5% 5% 6% 8% 41%	2604
	11th to 20th	Night	16% 6% 3 7% 5% 4 5% 4 7% 8% 35%	2606
	21st to end	Night	11% 6% 2 7% 4 5% 5% 4 7% 8% 41%	3245
September	1st to 10th	Night	11% 5% 3 7% 4 4 5% 4 7% 8% 43%	1934
	11th to 20th	Night	13% 6% 3 5% 4 3 4 4 6% 9% 44%	2135
	21st to end	Night	9% 6% 3 8% 5% 4 4 4 7% 10% 40%	2200
October	1st to 10th	Night	9% 9% 3 9% 6% 6% 7% 5% 7% 8% 32%	3806
	11th to 20th	Night	8% 10% 3 8% 5% 4 5% 4 7% 9% 37%	4216
	21st to end	Night	7% 9% 4 9% 5% 6% 5% 5% 7% 9% 34%	4600
November	1st to 10th	Night	13% 15% 5% 9% 6% 5% 4 4 5% 8% 26%	2887
	11th to 20th	Night	7% 12% 5% 12% 7% 7% 6% 5% 6% 6% 27%	3150
	21st to end	Night	6% 14% 4 11% 7% 5% 5% 5% 7% 8% 28%	3150
December	1st to 10th	Night	9% 15% 5% 12% 6% 5% 5% 4 6% 7% 26%	5040
	11th to 20th	Night	10% 15% 5% 12% 7% 6% 5% 4 5% 8% 21%	6006
	21st to end	Night	2 6% 3 9% 6% 6% 6% 5% 7% 8% 41%	8140

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	53% 8% 15% 12% 11% 1	2725
	11th to 20th	Day	42% 8% 14% 14% 19% 3	3023
	21st to end	Day	43% 8% 26% 17% 6%	3894
February	1st to 10th	Day	54% 9% 14% 12% 10% 1	1600
	11th to 20th	Day	49% 9% 15% 19% 8%	1613
	21st to end	Day	54% 6% 14% 18% 8%	1615
March	1st to 10th	Day	48% 7% 15% 18% 11%	4518
	11th to 20th	Day	48% 6% 14% 23% 10%	4795
	21st to end	Day	61% 6% 12% 14% 7%	5783
April	1st to 10th	Day	52% 9% 15% 16% 7%	2435
	11th to 20th	Day	49% 7% 14% 19% 10%	2570
	21st to end	Day	50% 10% 12% 21% 7% 1	2687
May	1st to 10th	Day	44% 7% 10% 24% 14% 1	6540
	11th to 20th	Day	53% 8% 13% 19% 6%	6738
	21st to end	Day	42% 9% 18% 22% 8% 1	7406
June	1st to 10th	Day	48% 8% 17% 18% 7% 1	3170
	11th to 20th	Day	56% 9% 15% 17% 4	3200
	21st to end	Day	42% 10% 21% 21% 6%	3200
July	1st to 10th	Day	31% 8% 22% 26% 11% 1	7161
	11th to 20th	Day	39% 8% 16% 30% 7%	7016
	21st to end	Day	37% 10% 22% 25% 7%	7169
August	1st to 10th	Day	38% 9% 20% 31% 2	4525
	11th to 20th	Day	37% 9% 20% 24% 10%	4483
	21st to end	Day	40% 8% 26% 21% 5%	4663
September	1st to 10th	Day	38% 10% 20% 26% 5% 1	2464
	11th to 20th	Day	38% 8% 21% 26% 7%	2265
	21st to end	Day	41% 9% 16% 24% 9% 1	2200
October	1st to 10th	Day	42% 8% 26% 20% 4	3388
	11th to 20th	Day	49% 7% 15% 23% 6%	2932
	21st to end	Day	48% 6% 18% 23% 4	3200
November	1st to 10th	Day	54% 8% 16% 16% 6%	1610
	11th to 20th	Day	49% 8% 18% 17% 9%	1470
	21st to end	Day	52% 9% 16% 16% 6% 2	1470
December	1st to 10th	Day	58% 9% 16% 11% 5% 1	2360
	11th to 20th	Day	58% 8% 16% 13% 5%	2402
	21st to end	Day	36% 7% 14% 28% 14% 1	3058
January	1st to 10th	Night	52% 7% 13% 17% 10% 1	7243
	11th to 20th	Night	45% 7% 15% 14% 16% 3	6922
	21st to end	Night	46% 9% 22% 16% 7%	7090
February	1st to 10th	Night	53% 7% 13% 15% 9% 1	2800
	11th to 20th	Night	50% 7% 15% 17% 9% 1	2683
	21st to end	Night	49% 7% 14% 19% 9% 1	2014
March	1st to 10th	Night	45% 7% 19% 18% 11%	5376
	11th to 20th	Night	47% 8% 17% 19% 10%	5205
	21st to end	Night	61% 7% 9% 15% 7%	5189
April	1st to 10th	Night	49% 7% 15% 18% 10% 1	1965
	11th to 20th	Night	50% 7% 12% 19% 11% 2	1781
	21st to end	Night	46% 9% 13% 22% 9% 1	1710
May	1st to 10th	Night	46% 6% 10% 22% 15% 2	3415
	11th to 20th	Night	53% 10% 13% 18% 6%	3159
	21st to end	Night	40% 10% 20% 22% 8% 1	3470
June	1st to 10th	Night	49% 8% 14% 18% 10%	1226
	11th to 20th	Night	56% 9% 16% 18% 1	1200
	21st to end	Night	46% 12% 18% 18% 5% 1	1200
July	1st to 10th	Night	36% 9% 18% 25% 13% 1	2690
	11th to 20th	Night	44% 8% 15% 25% 7%	2818
	21st to end	Night	38% 8% 25% 23% 5%	3369
August	1st to 10th	Night	39% 10% 21% 28% 2	2597
	11th to 20th	Night	44% 9% 16% 20% 11%	2630
	21st to end	Night	39% 10% 25% 22% 5%	3245
September	1st to 10th	Night	36% 8% 21% 27% 6% 2	1934
	11th to 20th	Night	35% 8% 20% 28% 9% 1	2135
	21st to end	Night	38% 8% 18% 25% 10% 2	2200
October	1st to 10th	Night	46% 8% 21% 18% 7%	3806
	11th to 20th	Night	43% 7% 16% 27% 8%	4216
	21st to end	Night	44% 8% 21% 22% 5%	4600
November	1st to 10th	Night	56% 6% 14% 18% 6%	2887
	11th to 20th	Night	55% 8% 13% 16% 8% 1	3150
	21st to end	Night	52% 9% 15% 17% 5% 2	3150
December	1st to 10th	Night	57% 7% 14% 15% 6% 1	5040
	11th to 20th	Night	61% 7% 14% 14% 4	6003
	21st to end	Night	37% 8% 14% 29% 10% 1	8140

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	12% 13% 30% 31% 10% 4	202
	11th to 20th	Day	13% 13% 32% 29% 12% 2	200
	21st to end	Day	17% 14% 33% 25% 9% 3	220
February	1st to 10th	Day	13% 17% 37% 23% 11% 2	200
	11th to 20th	Day	10% 15% 37% 29% 8% 2	223
	21st to end	Day	10% 13% 36% 31% 7% 3	379
March	1st to 10th	Day	10% 17% 31% 31% 12% 1	500
	11th to 20th	Day	11% 15% 32% 28% 11% 3	500
	21st to end	Day	19% 14% 29% 27% 9% 1	550
April	1st to 10th	Day	17% 17% 36% 21% 7% 2	500
	11th to 20th	Day	15% 18% 28% 23% 11% 4	492
	21st to end	Day	15% 16% 35% 24% 9% 1	500
May	1st to 10th	Day	17% 18% 28% 23% 12% 3	593
	11th to 20th	Day	12% 10% 31% 27% 16% 4	725
	21st to end	Day	14% 10% 25% 29% 15% 5%	789
June	1st to 10th	Day	19% 13% 31% 24% 11% 2	900
	11th to 20th	Day	21% 10% 27% 24% 15% 3	930
	21st to end	Day	12% 9% 24% 29% 19% 6%	930
July	1st to 10th	Day	15% 8% 26% 31% 16% 5%	916
	11th to 20th	Day	13% 9% 27% 28% 17% 5%	853
	21st to end	Day	13% 7% 22% 31% 19% 8%	794
August	1st to 10th	Day	14% 9% 24% 27% 18% 8%	529
	11th to 20th	Day	12% 13% 32% 28% 13% 3	517
	21st to end	Day	15% 11% 24% 27% 17% 5%	583
September	1st to 10th	Day	13% 14% 28% 25% 15% 6%	530
	11th to 20th	Day	17% 9% 24% 30% 16% 3	530
	21st to end	Day	15% 17% 30% 25% 11% 2	530
October	1st to 10th	Day	17% 14% 26% 26% 15% 3	477
	11th to 20th	Day	19% 11% 32% 25% 12% 2	330
	21st to end	Day	17% 19% 28% 27% 6% 2	363
November	1st to 10th	Day	18% 12% 29% 29% 10% 2	289
	11th to 20th	Day	13% 13% 37% 28% 7% 2	220
	21st to end	Day	9% 12% 39% 29% 6% 5%	220
December	1st to 10th	Day	13% 12% 31% 35% 6% 3	220
	11th to 20th	Day	13% 19% 30% 26% 9% 2	220
	21st to end	Day	13% 9% 29% 32% 13% 5%	242
January	1st to 10th	Night	12% 12% 32% 31% 11% 2	1107
	11th to 20th	Night	11% 14% 33% 31% 9% 1	1032
	21st to end	Night	16% 17% 30% 27% 9% 1	940
February	1st to 10th	Night	11% 14% 28% 32% 14% 2	800
	11th to 20th	Night	10% 9% 35% 33% 11% 1	784
	21st to end	Night	9% 8% 33% 36% 11% 3	660
March	1st to 10th	Night	8% 11% 33% 34% 13% 1	800
	11th to 20th	Night	12% 8% 33% 35% 11% 2	800
	21st to end	Night	17% 9% 28% 33% 12% 1	880
April	1st to 10th	Night	13% 9% 30% 35% 12% 1	765
	11th to 20th	Night	16% 9% 32% 31% 12% 1	593
	21st to end	Night	14% 11% 28% 34% 13% 1	510
May	1st to 10th	Night	18% 13% 23% 33% 12% 2	400
	11th to 20th	Night	13% 8% 29% 32% 17% 1	394
	21st to end	Night	20% 8% 21% 32% 17% 2	433
June	1st to 10th	Night	19% 11% 25% 29% 17% 1	400
	11th to 20th	Night	20% 6% 24% 27% 22% 2	400
	21st to end	Night	13% 4 21% 35% 25% 3	400
July	1st to 10th	Night	16% 3 19% 37% 25%	390
	11th to 20th	Night	15% 5% 21% 34% 23% 2	388
	21st to end	Night	12% 5% 18% 40% 23% 3	438
August	1st to 10th	Night	13% 4 21% 29% 28% 5%	398
	11th to 20th	Night	13% 4 22% 35% 25% 1	412
	21st to end	Night	13% 4 22% 38% 22% 1	660
September	1st to 10th	Night	14% 5% 22% 37% 20% 3	734
	11th to 20th	Night	15% 6% 20% 39% 20% 1	800
	21st to end	Night	11% 10% 31% 32% 14% 2	800
October	1st to 10th	Night	17% 8% 28% 33% 14% 1	800
	11th to 20th	Night	13% 11% 28% 34% 14% 1	800
	21st to end	Night	15% 13% 33% 29% 9% 1	880
November	1st to 10th	Night	20% 10% 29% 30% 10% 1	963
	11th to 20th	Night	13% 14% 35% 28% 8% 2	1050
	21st to end	Night	12% 11% 34% 32% 9% 2	1050
December	1st to 10th	Night	13% 15% 32% 30% 9% 1	1050
	11th to 20th	Night	13% 14% 32% 30% 10% 1	1130
	21st to end	Night	10% 8% 33% 36% 11% 2	1276

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