Vegreville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vegreville clear sky chart from 2005-11-06 to 2026-07-01.

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	10% 9% 3 9% 6% 5% 5% 4 6% 8% 35%	142195
	Night	8% 9% 4 10% 6% 6% 5% 5% 6% 8% 33%	138876
Transparency	Day	46% 6% 17% 24% 8% 1	141892
	Night	47% 6% 16% 21% 9% 1	138765
Seeing	Day	14% 7% 25% 30% 18% 6%	17672
	Night	13% 6% 28% 35% 15% 2	26699

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	7% 13% 5% 13% 9% 7% 6% 4 6% 7% 22%	4125
	11th to 20th	Day	3 9% 2 10% 7% 6% 8% 7% 9% 11% 29%	4119
	21st to end	Day	7% 11% 4 10% 9% 5% 6% 4 6% 8% 31%	4692
February	1st to 10th	Day	8% 14% 5% 12% 8% 6% 6% 4 6% 8% 23%	1680
	11th to 20th	Day	6% 14% 6% 11% 7% 6% 6% 5% 7% 7% 26%	1845
	21st to end	Day	4 14% 4 11% 8% 6% 7% 6% 8% 8% 25%	1557
March	1st to 10th	Day	5% 9% 4 12% 7% 6% 7% 5% 7% 8% 29%	4675
	11th to 20th	Day	6% 12% 6% 14% 5% 6% 4 3 5% 8% 31%	5109
	21st to end	Day	10% 14% 5% 16% 5% 5% 5% 4 5% 7% 25%	5607
April	1st to 10th	Day	8% 13% 4 8% 6% 6% 6% 5% 6% 8% 30%	2644
	11th to 20th	Day	12% 11% 5% 9% 5% 4 5% 4 6% 8% 31%	2700
	21st to end	Day	13% 11% 3 7% 5% 5% 5% 5% 6% 7% 33%	2746
May	1st to 10th	Day	9% 7% 3 8% 5% 5% 5% 4 6% 8% 40%	8523
	11th to 20th	Day	18% 11% 3 8% 5% 5% 5% 4 6% 8% 27%	8755
	21st to end	Day	11% 6% 3 8% 6% 5% 5% 4 6% 8% 36%	9649
June	1st to 10th	Day	14% 9% 3 7% 6% 5% 5% 4 7% 7% 32%	3150
	11th to 20th	Day	19% 9% 4 8% 7% 6% 6% 5% 6% 7% 24%	3150
	21st to end	Day	11% 6% 2 7% 6% 6% 6% 5% 8% 10% 34%	3150
July	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 4 7% 9% 46%	6781
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 5% 6% 8% 43%	6780
	21st to end	Day	10% 6% 2 6% 5% 5% 4 4 7% 9% 43%	7376
August	1st to 10th	Day	12% 6% 2 7% 4 5% 4 4 6% 8% 42%	4777
	11th to 20th	Day	8% 5% 3 7% 4 5% 5% 5% 7% 11% 42%	4197
	21st to end	Day	9% 5% 2 5% 4 5% 4 4 7% 10% 45%	4664
September	1st to 10th	Day	10% 5% 3 7% 5% 4 4 4 7% 7% 44%	2540
	11th to 20th	Day	14% 6% 2 6% 3 3 5% 4 5% 8% 42%	2220
	21st to end	Day	9% 6% 2 6% 5% 4 5% 4 6% 9% 45%	2200
October	1st to 10th	Day	9% 9% 3 9% 5% 4 5% 4 5% 7% 40%	3315
	11th to 20th	Day	10% 9% 4 8% 4 5% 5% 4 6% 9% 38%	3072
	21st to end	Day	7% 11% 4 8% 5% 5% 5% 4 6% 7% 38%	3057
November	1st to 10th	Day	10% 14% 4 9% 6% 6% 6% 4 5% 6% 28%	1648
	11th to 20th	Day	8% 11% 5% 13% 8% 5% 5% 4 6% 7% 29%	1575
	21st to end	Day	4 12% 6% 13% 7% 4 6% 5% 6% 8% 29%	1470
December	1st to 10th	Day	8% 14% 5% 12% 7% 7% 6% 6% 7% 7% 20%	2360
	11th to 20th	Day	9% 14% 4 11% 8% 7% 6% 6% 7% 7% 21%	2712
	21st to end	Day	3 9% 4 11% 7% 6% 5% 4 6% 7% 38%	3575
January	1st to 10th	Night	7% 11% 5% 14% 9% 8% 7% 5% 7% 7% 20%	8768
	11th to 20th	Night	3 9% 3 9% 7% 6% 6% 5% 6% 8% 38%	8779
	21st to end	Night	6% 11% 4 11% 7% 5% 5% 4 7% 8% 30%	9533
February	1st to 10th	Night	6% 11% 5% 11% 8% 8% 6% 5% 6% 8% 25%	2940
	11th to 20th	Night	6% 10% 4 11% 7% 8% 6% 5% 8% 7% 28%	2662
	21st to end	Night	3 11% 4 12% 8% 6% 7% 5% 7% 8% 29%	2249
March	1st to 10th	Night	5% 9% 4 12% 7% 5% 6% 5% 8% 11% 27%	5438
	11th to 20th	Night	3 9% 5% 13% 7% 6% 6% 5% 7% 8% 30%	5110
	21st to end	Night	10% 13% 6% 14% 7% 5% 5% 4 6% 7% 24%	5610
April	1st to 10th	Night	6% 11% 3 8% 6% 6% 6% 5% 7% 8% 35%	1973
	11th to 20th	Night	10% 10% 4 9% 6% 6% 6% 4 7% 8% 30%	1871
	21st to end	Night	14% 10% 3 7% 4 5% 5% 4 6% 7% 35%	1874
May	1st to 10th	Night	12% 7% 2 6% 4 5% 4 4 6% 7% 43%	4408
	11th to 20th	Night	14% 10% 4 9% 6% 6% 6% 5% 6% 7% 26%	4105
	21st to end	Night	12% 7% 3 7% 6% 5% 5% 5% 6% 9% 35%	4522
June	1st to 10th	Night	15% 8% 3 8% 5% 6% 5% 5% 7% 7% 31%	1470
	11th to 20th	Night	16% 9% 4 9% 6% 6% 6% 5% 8% 7% 24%	1470
	21st to end	Night	11% 6% 2 6% 4 5% 6% 6% 7% 10% 37%	1470
July	1st to 10th	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 9% 45%	3180
	11th to 20th	Night	9% 6% 2 6% 5% 5% 5% 5% 6% 10% 40%	3180
	21st to end	Night	11% 5% 2 5% 3 4 4 4 7% 10% 44%	3467
August	1st to 10th	Night	13% 4 2 5% 4 4 4 4 6% 8% 44%	2371
	11th to 20th	Night	9% 6% 3 7% 5% 5% 5% 4 6% 9% 40%	2861
	21st to end	Night	9% 6% 2 5% 4 4 5% 5% 6% 8% 47%	3245
September	1st to 10th	Night	11% 4 2 7% 4 4 5% 4 6% 7% 47%	1859
	11th to 20th	Night	12% 6% 2 5% 4 4 5% 3 6% 7% 47%	2177
	21st to end	Night	8% 6% 2 7% 5% 5% 4 4 6% 8% 45%	2200
October	1st to 10th	Night	8% 7% 3 7% 4 5% 5% 5% 6% 8% 41%	3875
	11th to 20th	Night	9% 7% 3 7% 4 4 5% 4 7% 9% 42%	4073
	21st to end	Night	6% 9% 5% 9% 4 4 5% 4 7% 9% 37%	4710
November	1st to 10th	Night	13% 16% 5% 9% 5% 5% 5% 3 5% 6% 28%	2870
	11th to 20th	Night	8% 13% 4 12% 8% 6% 6% 4 6% 8% 26%	3043
	21st to end	Night	5% 13% 5% 12% 8% 6% 6% 4 5% 9% 28%	3150
December	1st to 10th	Night	10% 15% 5% 13% 8% 6% 5% 4 7% 7% 20%	5040
	11th to 20th	Night	7% 14% 5% 15% 8% 7% 7% 5% 6% 7% 19%	5700
	21st to end	Night	3 7% 3 11% 6% 6% 6% 5% 6% 7% 40%	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	61% 4 9% 16% 10%	4125
	11th to 20th	Day	47% 5% 16% 16% 16%	4140
	21st to end	Day	51% 6% 19% 19% 6%	4693
February	1st to 10th	Day	59% 5% 12% 16% 8%	1680
	11th to 20th	Day	54% 5% 15% 16% 9%	1854
	21st to end	Day	53% 6% 13% 20% 8%	1557
March	1st to 10th	Day	50% 5% 20% 20% 5%	4675
	11th to 20th	Day	51% 5% 16% 20% 7%	5110
	21st to end	Day	57% 6% 10% 21% 6%	5607
April	1st to 10th	Day	51% 7% 15% 19% 8% 1	2644
	11th to 20th	Day	49% 5% 15% 21% 9% 1	2700
	21st to end	Day	47% 6% 14% 24% 8% 1	2746
May	1st to 10th	Day	41% 5% 11% 27% 14% 1	8523
	11th to 20th	Day	54% 5% 10% 25% 7% 1	8759
	21st to end	Day	43% 6% 17% 23% 10% 1	9650
June	1st to 10th	Day	48% 7% 13% 21% 10% 1	3150
	11th to 20th	Day	56% 8% 14% 18% 4	3150
	21st to end	Day	42% 9% 20% 21% 7% 1	3150
July	1st to 10th	Day	33% 7% 24% 29% 8%	6707
	11th to 20th	Day	37% 6% 16% 29% 11%	6699
	21st to end	Day	37% 6% 22% 28% 6%	7169
August	1st to 10th	Day	39% 7% 18% 33% 3	4759
	11th to 20th	Day	34% 6% 27% 25% 8%	4236
	21st to end	Day	34% 6% 27% 28% 4 1	4663
September	1st to 10th	Day	37% 7% 19% 27% 8% 2	2540
	11th to 20th	Day	39% 6% 17% 31% 6% 1	2220
	21st to end	Day	36% 7% 18% 29% 8% 2	2200
October	1st to 10th	Day	42% 5% 23% 24% 5%	3315
	11th to 20th	Day	43% 4 14% 29% 9%	3072
	21st to end	Day	44% 5% 18% 28% 4	3057
November	1st to 10th	Day	56% 5% 15% 17% 6%	1648
	11th to 20th	Day	53% 6% 17% 18% 5%	1575
	21st to end	Day	51% 8% 17% 18% 5%	1470
December	1st to 10th	Day	60% 6% 18% 11% 4	2360
	11th to 20th	Day	59% 5% 17% 15% 4	2714
	21st to end	Day	45% 4 12% 29% 9% 1	3575
January	1st to 10th	Night	61% 5% 12% 13% 10%	8769
	11th to 20th	Night	44% 5% 17% 18% 15% 1	8820
	21st to end	Night	50% 5% 20% 18% 7%	9533
February	1st to 10th	Night	55% 5% 13% 16% 9% 1	2940
	11th to 20th	Night	52% 6% 12% 18% 11% 1	2663
	21st to end	Night	50% 7% 12% 22% 8% 1	2249
March	1st to 10th	Night	47% 6% 19% 20% 8%	5438
	11th to 20th	Night	48% 6% 15% 22% 9% 1	5110
	21st to end	Night	57% 6% 11% 17% 9%	5610
April	1st to 10th	Night	44% 7% 15% 21% 13% 1	1973
	11th to 20th	Night	49% 6% 13% 20% 9% 3	1871
	21st to end	Night	46% 6% 13% 21% 11% 3	1874
May	1st to 10th	Night	39% 4 9% 30% 17% 2	4408
	11th to 20th	Night	53% 6% 11% 21% 8% 1	4105
	21st to end	Night	44% 6% 17% 25% 8%	4526
June	1st to 10th	Night	49% 7% 11% 21% 10% 1	1470
	11th to 20th	Night	54% 8% 15% 17% 6%	1470
	21st to end	Night	38% 10% 21% 24% 6% 1	1470
July	1st to 10th	Night	34% 6% 25% 22% 14% 1	3145
	11th to 20th	Night	38% 6% 15% 29% 10% 1	3138
	21st to end	Night	34% 7% 25% 28% 7%	3369
August	1st to 10th	Night	36% 8% 20% 34% 2	2364
	11th to 20th	Night	39% 6% 23% 24% 8%	2888
	21st to end	Night	34% 6% 23% 30% 7%	3245
September	1st to 10th	Night	35% 6% 19% 27% 10% 3	1859
	11th to 20th	Night	36% 6% 17% 29% 10% 2	2177
	21st to end	Night	35% 6% 16% 28% 12% 3	2200
October	1st to 10th	Night	39% 5% 21% 27% 7% 1	3875
	11th to 20th	Night	37% 5% 15% 34% 8%	4073
	21st to end	Night	42% 6% 23% 25% 4	4710
November	1st to 10th	Night	57% 5% 11% 20% 7% 1	2870
	11th to 20th	Night	55% 7% 15% 17% 5% 1	3043
	21st to end	Night	53% 7% 16% 18% 5% 1	3150
December	1st to 10th	Night	62% 6% 14% 12% 5% 1	5040
	11th to 20th	Night	62% 6% 16% 11% 4	5697
	21st to end	Night	43% 4 15% 22% 14% 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% 5% 25% 38% 16% 5%	220
	11th to 20th	Day	12% 11% 26% 35% 12% 4	220
	21st to end	Day	11% 9% 33% 30% 14% 4	242
February	1st to 10th	Day	12% 9% 27% 35% 13% 5%	220
	11th to 20th	Day	11% 8% 30% 34% 12% 4	330
	21st to end	Day	10% 7% 30% 30% 18% 6%	273
March	1st to 10th	Day	11% 9% 29% 32% 16% 2	535
	11th to 20th	Day	11% 6% 32% 30% 15% 5%	540
	21st to end	Day	15% 6% 30% 28% 17% 4	594
April	1st to 10th	Day	10% 10% 32% 32% 15% 2	540
	11th to 20th	Day	16% 10% 25% 32% 13% 4	532
	21st to end	Day	19% 9% 25% 29% 14% 3	556
May	1st to 10th	Day	14% 11% 25% 30% 16% 5%	753
	11th to 20th	Day	14% 7% 26% 29% 17% 7%	775
	21st to end	Day	17% 6% 22% 27% 19% 8%	844
June	1st to 10th	Day	19% 9% 25% 29% 15% 3	780
	11th to 20th	Day	20% 9% 23% 26% 15% 7%	780
	21st to end	Day	12% 6% 20% 30% 21% 11%	780
July	1st to 10th	Day	11% 4 18% 31% 27% 8%	722
	11th to 20th	Day	12% 5% 20% 31% 24% 8%	718
	21st to end	Day	10% 4 18% 31% 28% 10%	794
August	1st to 10th	Day	14% 4 16% 30% 25% 11%	672
	11th to 20th	Day	11% 5% 21% 33% 22% 8%	517
	21st to end	Day	14% 4 21% 30% 22% 10%	583
September	1st to 10th	Day	12% 8% 28% 28% 17% 7%	530
	11th to 20th	Day	17% 7% 21% 31% 20% 4	530
	21st to end	Day	12% 12% 33% 27% 15% 3	530
October	1st to 10th	Day	15% 7% 27% 30% 17% 4	362
	11th to 20th	Day	15% 8% 35% 28% 14% 1	330
	21st to end	Day	16% 12% 34% 24% 10% 3	363
November	1st to 10th	Day	17% 7% 32% 30% 11% 3	330
	11th to 20th	Day	12% 9% 33% 36% 9% 1	275
	21st to end	Day	6% 6% 37% 33% 13% 5%	220
December	1st to 10th	Day	7% 9% 35% 33% 13% 4	220
	11th to 20th	Day	13% 9% 30% 32% 16% 1	220
	21st to end	Day	13% 3 24% 37% 17% 6%	242
January	1st to 10th	Night	12% 6% 31% 36% 13% 2	1050
	11th to 20th	Night	10% 9% 33% 35% 12% 1	1050
	21st to end	Night	14% 10% 33% 31% 10% 2	1116
February	1st to 10th	Night	11% 7% 28% 35% 16% 2	840
	11th to 20th	Night	10% 6% 30% 38% 15% 1	824
	21st to end	Night	7% 5% 29% 36% 18% 5%	692
March	1st to 10th	Night	10% 6% 27% 40% 15% 2	840
	11th to 20th	Night	10% 5% 32% 35% 15% 3	840
	21st to end	Night	14% 6% 26% 35% 17% 2	924
April	1st to 10th	Night	10% 7% 30% 34% 16% 3	683
	11th to 20th	Night	14% 5% 33% 33% 14% 1	623
	21st to end	Night	19% 5% 23% 38% 14% 1	630
May	1st to 10th	Night	17% 7% 23% 34% 17% 3	520
	11th to 20th	Night	15% 5% 21% 40% 18% 1	414
	21st to end	Night	19% 5% 20% 35% 19% 1	455
June	1st to 10th	Night	21% 5% 22% 35% 15% 2	420
	11th to 20th	Night	20% 6% 24% 30% 18% 2	420
	21st to end	Night	13% 3 20% 35% 25% 4	420
July	1st to 10th	Night	13% 2 19% 41% 24% 1	390
	11th to 20th	Night	12% 3 19% 44% 21% 2	388
	21st to end	Night	9% 3 17% 42% 25% 3	438
August	1st to 10th	Night	12% 3 14% 38% 30% 4	398
	11th to 20th	Night	12% 5% 18% 41% 22% 3	566
	21st to end	Night	10% 4 22% 40% 23% 2	660
September	1st to 10th	Night	13% 4 22% 36% 24% 2	600
	11th to 20th	Night	14% 3 20% 44% 19% 1	777
	21st to end	Night	11% 6% 32% 36% 15% 1	800
October	1st to 10th	Night	16% 5% 28% 36% 15% 1	800
	11th to 20th	Night	13% 5% 32% 37% 12% 2	800
	21st to end	Night	13% 7% 34% 32% 12% 1	941
November	1st to 10th	Night	20% 8% 30% 32% 9% 2	1025
	11th to 20th	Night	15% 7% 33% 31% 11% 3	1050
	21st to end	Night	10% 6% 37% 33% 11% 2	1050
December	1st to 10th	Night	14% 8% 33% 27% 14% 3	1050
	11th to 20th	Night	12% 7% 33% 34% 12% 2	1050
	21st to end	Night	11% 4 29% 37% 15% 4	1155

Page generated at 2026-06-28 00:10:44. Version ac07

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