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 2024-09-29.

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%	101718
	Night	8% 9% 4 10% 6% 6% 6% 5% 6% 8% 33%	96590
Transparency	Day	46% 6% 17% 23% 7%	101459
	Night	47% 6% 16% 21% 9% 1	96495
Seeing	Day	14% 7% 25% 30% 18% 6%	15424
	Night	13% 6% 27% 36% 16% 2	24360

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	5% 11% 5% 14% 11% 8% 7% 4 5% 7% 22%	2219
	11th to 20th	Day	5% 9% 2 10% 7% 7% 9% 9% 10% 8% 23%	2199
	21st to end	Day	7% 13% 4 11% 8% 5% 5% 4 5% 7% 31%	2520
February	1st to 10th	Day	8% 15% 5% 12% 9% 6% 6% 4 6% 8% 22%	1520
	11th to 20th	Day	6% 14% 6% 12% 7% 6% 6% 5% 7% 7% 25%	1665
	21st to end	Day	4 14% 4 11% 8% 6% 7% 6% 8% 8% 25%	1413
March	1st to 10th	Day	5% 11% 5% 11% 7% 6% 7% 5% 7% 9% 27%	3181
	11th to 20th	Day	5% 11% 5% 13% 4 4 3 3 5% 9% 37%	3489
	21st to end	Day	8% 12% 5% 18% 6% 5% 5% 4 5% 6% 26%	3825
April	1st to 10th	Day	9% 14% 4 8% 6% 6% 6% 5% 6% 8% 29%	2392
	11th to 20th	Day	13% 11% 5% 8% 5% 4 4 4 6% 8% 31%	2440
	21st to end	Day	14% 11% 3 7% 5% 5% 4 5% 6% 7% 33%	2484
May	1st to 10th	Day	15% 10% 4 10% 6% 5% 5% 4 6% 6% 30%	4600
	11th to 20th	Day	14% 10% 3 8% 6% 5% 6% 5% 6% 7% 29%	4694
	21st to end	Day	13% 9% 3 10% 7% 6% 6% 5% 6% 8% 29%	5161
June	1st to 10th	Day	14% 9% 3 8% 6% 5% 5% 5% 7% 7% 31%	2850
	11th to 20th	Day	19% 9% 4 8% 7% 6% 5% 5% 6% 8% 25%	2850
	21st to end	Day	10% 6% 2 7% 6% 6% 6% 5% 9% 9% 34%	2850
July	1st to 10th	Day	7% 5% 2 7% 5% 5% 5% 4 6% 9% 47%	4740
	11th to 20th	Day	9% 5% 2 5% 4 5% 5% 4 6% 8% 46%	4740
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 9% 45%	5138
August	1st to 10th	Day	12% 6% 2 7% 4 4 4 4 6% 9% 42%	4630
	11th to 20th	Day	7% 5% 3 6% 4 5% 5% 5% 7% 11% 43%	4066
	21st to end	Day	10% 5% 2 6% 4 5% 4 4 7% 10% 44%	4521
September	1st to 10th	Day	11% 5% 3 7% 5% 4 4 4 7% 7% 43%	2413
	11th to 20th	Day	14% 7% 2 7% 4 4 5% 4 5% 8% 40%	2109
	21st to end	Day	9% 6% 2 6% 5% 3 5% 4 6% 9% 45%	2069
October	1st to 10th	Day	11% 10% 3 9% 5% 4 5% 5% 5% 6% 37%	1830
	11th to 20th	Day	10% 9% 4 9% 5% 4 4 4 5% 7% 39%	1704
	21st to end	Day	8% 12% 4 10% 6% 5% 5% 4 6% 8% 31%	1709
November	1st to 10th	Day	10% 15% 4 10% 6% 6% 6% 4 5% 7% 27%	1488
	11th to 20th	Day	8% 11% 5% 13% 8% 5% 5% 4 6% 7% 28%	1425
	21st to end	Day	4 12% 6% 13% 7% 4 6% 5% 6% 7% 30%	1330
December	1st to 10th	Day	7% 12% 4 13% 8% 7% 7% 5% 6% 7% 24%	1330
	11th to 20th	Day	7% 10% 4 12% 8% 7% 6% 6% 7% 8% 25%	1682
	21st to end	Day	3 9% 4 9% 6% 5% 5% 3 5% 7% 43%	2442
January	1st to 10th	Night	4 11% 5% 16% 8% 8% 6% 5% 7% 8% 21%	4726
	11th to 20th	Night	3 8% 3 9% 9% 8% 7% 7% 6% 7% 32%	4699
	21st to end	Night	7% 12% 5% 11% 7% 5% 6% 4 6% 8% 31%	5153
February	1st to 10th	Night	6% 12% 5% 12% 8% 8% 6% 5% 6% 8% 25%	2660
	11th to 20th	Night	6% 11% 4 11% 7% 7% 6% 5% 7% 7% 28%	2402
	21st to end	Night	3 10% 4 11% 8% 6% 7% 5% 7% 8% 29%	2041
March	1st to 10th	Night	5% 10% 5% 13% 8% 6% 6% 5% 8% 10% 25%	3692
	11th to 20th	Night	4 8% 4 12% 5% 5% 6% 4 6% 9% 37%	3490
	21st to end	Night	6% 11% 6% 15% 7% 6% 6% 4 7% 7% 23%	3828
April	1st to 10th	Night	6% 11% 3 8% 6% 6% 6% 5% 6% 7% 35%	1786
	11th to 20th	Night	11% 9% 4 9% 7% 5% 6% 4 7% 8% 30%	1691
	21st to end	Night	14% 10% 3 7% 5% 5% 5% 4 6% 6% 35%	1696
May	1st to 10th	Night	22% 10% 2 7% 4 5% 4 5% 5% 6% 29%	2362
	11th to 20th	Night	14% 9% 3 8% 5% 5% 6% 6% 7% 8% 30%	2199
	21st to end	Night	14% 8% 3 8% 6% 6% 6% 5% 6% 8% 30%	2414
June	1st to 10th	Night	14% 8% 3 8% 5% 6% 5% 5% 7% 7% 31%	1330
	11th to 20th	Night	16% 10% 4 8% 7% 6% 7% 5% 7% 8% 24%	1330
	21st to end	Night	9% 6% 2 6% 4 5% 6% 6% 8% 10% 37%	1330
July	1st to 10th	Night	8% 6% 3 6% 5% 5% 5% 4 7% 8% 43%	2220
	11th to 20th	Night	7% 5% 2 5% 5% 4 5% 5% 7% 12% 43%	2220
	21st to end	Night	12% 6% 2 5% 3 3 4 4 6% 9% 46%	2414
August	1st to 10th	Night	13% 4 2 5% 4 4 4 4 6% 8% 44%	2298
	11th to 20th	Night	9% 6% 3 7% 5% 5% 5% 4 6% 9% 41%	2772
	21st to end	Night	9% 6% 2 5% 4 4 5% 5% 6% 8% 46%	3146
September	1st to 10th	Night	11% 4 2 8% 4 4 5% 4 5% 7% 46%	1766
	11th to 20th	Night	13% 6% 2 5% 4 4 5% 3 6% 7% 46%	2068
	21st to end	Night	7% 6% 2 7% 5% 5% 4 4 6% 8% 46%	2079
October	1st to 10th	Night	12% 8% 3 7% 4 5% 4 5% 6% 7% 40%	2129
	11th to 20th	Night	9% 9% 3 8% 4 4 5% 5% 7% 7% 39%	2254
	21st to end	Night	8% 10% 5% 10% 4 5% 5% 4 7% 8% 33%	2628
November	1st to 10th	Night	13% 16% 5% 9% 6% 5% 5% 3 5% 7% 27%	2590
	11th to 20th	Night	9% 13% 4 12% 8% 6% 6% 4 6% 8% 25%	2753
	21st to end	Night	5% 13% 5% 12% 8% 6% 6% 4 5% 8% 29%	2850
December	1st to 10th	Night	7% 13% 4 12% 8% 6% 6% 4 6% 7% 27%	2850
	11th to 20th	Night	6% 11% 5% 15% 9% 7% 6% 5% 6% 8% 23%	3510
	21st to end	Night	4 7% 3 8% 6% 6% 5% 4 6% 7% 43%	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	62% 5% 10% 18% 4	2219
	11th to 20th	Day	51% 6% 14% 16% 12% 1	2220
	21st to end	Day	52% 5% 16% 21% 6%	2520
February	1st to 10th	Day	60% 5% 12% 15% 7%	1520
	11th to 20th	Day	55% 5% 16% 16% 7%	1674
	21st to end	Day	53% 6% 12% 20% 8%	1413
March	1st to 10th	Day	52% 5% 17% 19% 6%	3181
	11th to 20th	Day	45% 6% 22% 20% 8%	3490
	21st to end	Day	58% 7% 11% 20% 4	3825
April	1st to 10th	Day	52% 7% 15% 18% 8% 1	2392
	11th to 20th	Day	50% 5% 14% 22% 8% 1	2440
	21st to end	Day	47% 6% 14% 23% 8% 1	2484
May	1st to 10th	Day	54% 6% 11% 24% 5%	4600
	11th to 20th	Day	50% 7% 10% 23% 9% 1	4698
	21st to end	Day	49% 8% 15% 19% 8%	5162
June	1st to 10th	Day	49% 7% 13% 20% 10%	2850
	11th to 20th	Day	55% 8% 15% 18% 4 1	2850
	21st to end	Day	41% 9% 21% 21% 8% 1	2850
July	1st to 10th	Day	33% 7% 22% 28% 9% 1	4666
	11th to 20th	Day	34% 7% 18% 28% 13%	4659
	21st to end	Day	36% 7% 22% 28% 8%	4976
August	1st to 10th	Day	38% 7% 18% 33% 3	4612
	11th to 20th	Day	33% 7% 27% 25% 8%	4105
	21st to end	Day	34% 6% 28% 28% 3 1	4520
September	1st to 10th	Day	38% 7% 19% 26% 8% 2	2413
	11th to 20th	Day	41% 6% 17% 30% 6%	2109
	21st to end	Day	36% 7% 18% 29% 8% 2	2069
October	1st to 10th	Day	47% 6% 18% 21% 8%	1830
	11th to 20th	Day	44% 6% 16% 26% 9%	1704
	21st to end	Day	50% 7% 14% 22% 6%	1709
November	1st to 10th	Day	57% 5% 15% 17% 6% 1	1488
	11th to 20th	Day	54% 7% 17% 18% 4	1425
	21st to end	Day	51% 8% 18% 18% 5% 1	1330
December	1st to 10th	Day	57% 7% 13% 14% 8% 1	1330
	11th to 20th	Day	54% 6% 16% 17% 6%	1684
	21st to end	Day	41% 4 11% 29% 13% 2	2442
January	1st to 10th	Night	59% 6% 13% 15% 5% 1	4726
	11th to 20th	Night	49% 6% 13% 19% 12% 1	4740
	21st to end	Night	51% 5% 19% 19% 6%	5153
February	1st to 10th	Night	56% 6% 13% 16% 8% 1	2660
	11th to 20th	Night	52% 7% 13% 17% 10% 1	2403
	21st to end	Night	49% 7% 12% 22% 8% 1	2041
March	1st to 10th	Night	52% 6% 15% 20% 8%	3692
	11th to 20th	Night	42% 6% 19% 22% 10% 1	3490
	21st to end	Night	54% 8% 13% 19% 6%	3828
April	1st to 10th	Night	44% 7% 14% 21% 12% 1	1786
	11th to 20th	Night	50% 6% 12% 20% 9% 3	1691
	21st to end	Night	46% 6% 13% 21% 11% 3	1696
May	1st to 10th	Night	54% 5% 9% 24% 7% 1	2362
	11th to 20th	Night	46% 8% 12% 23% 10% 1	2199
	21st to end	Night	50% 8% 14% 20% 8% 1	2414
June	1st to 10th	Night	49% 7% 12% 21% 9% 1	1330
	11th to 20th	Night	53% 8% 15% 17% 7%	1330
	21st to end	Night	37% 11% 21% 23% 7% 1	1330
July	1st to 10th	Night	37% 6% 20% 19% 17% 1	2185
	11th to 20th	Night	32% 8% 19% 30% 11% 1	2178
	21st to end	Night	33% 6% 25% 29% 8%	2337
August	1st to 10th	Night	35% 8% 20% 34% 2	2291
	11th to 20th	Night	39% 6% 23% 24% 8%	2799
	21st to end	Night	34% 6% 24% 30% 6%	3146
September	1st to 10th	Night	36% 6% 19% 26% 10% 3	1766
	11th to 20th	Night	37% 6% 17% 29% 10% 2	2068
	21st to end	Night	35% 7% 16% 28% 13% 3	2079
October	1st to 10th	Night	42% 6% 16% 24% 11% 1	2129
	11th to 20th	Night	41% 6% 16% 27% 9% 1	2254
	21st to end	Night	46% 8% 15% 23% 7% 1	2628
November	1st to 10th	Night	57% 6% 11% 20% 6% 1	2590
	11th to 20th	Night	56% 7% 15% 17% 5% 1	2753
	21st to end	Night	53% 7% 17% 18% 5%	2850
December	1st to 10th	Night	54% 6% 12% 18% 8% 1	2850
	11th to 20th	Night	58% 7% 15% 12% 6%	3507
	21st to end	Night	39% 4 16% 21% 17% 3	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	9% 4 26% 38% 18% 4	180
	11th to 20th	Day	13% 9% 24% 36% 14% 5%	180
	21st to end	Day	12% 7% 31% 32% 14% 5%	198
February	1st to 10th	Day	13% 9% 27% 36% 12% 3	180
	11th to 20th	Day	11% 8% 31% 33% 13% 4	270
	21st to end	Day	10% 5% 29% 28% 20% 8%	225
March	1st to 10th	Day	11% 9% 28% 33% 16% 3	455
	11th to 20th	Day	10% 7% 32% 30% 14% 6%	460
	21st to end	Day	15% 6% 29% 29% 17% 4	506
April	1st to 10th	Day	10% 12% 33% 30% 13% 2	460
	11th to 20th	Day	17% 8% 23% 33% 13% 5%	452
	21st to end	Day	19% 10% 24% 30% 14% 3	474
May	1st to 10th	Day	15% 10% 23% 30% 16% 6%	653
	11th to 20th	Day	12% 7% 26% 31% 18% 6%	675
	21st to end	Day	18% 7% 21% 26% 20% 9%	734
June	1st to 10th	Day	18% 8% 25% 30% 16% 3	680
	11th to 20th	Day	19% 8% 24% 26% 15% 8%	680
	21st to end	Day	11% 5% 19% 31% 22% 11%	680
July	1st to 10th	Day	11% 4 17% 31% 28% 8%	671
	11th to 20th	Day	12% 5% 19% 32% 25% 7%	668
	21st to end	Day	10% 4 17% 31% 27% 10%	739
August	1st to 10th	Day	14% 4 16% 31% 25% 11%	625
	11th to 20th	Day	9% 5% 21% 34% 23% 8%	477
	21st to end	Day	14% 4 21% 29% 22% 10%	539
September	1st to 10th	Day	12% 9% 29% 28% 16% 7%	490
	11th to 20th	Day	19% 8% 22% 30% 18% 4	490
	21st to end	Day	12% 12% 32% 26% 15% 3	483
October	1st to 10th	Day	16% 7% 26% 29% 18% 4	300
	11th to 20th	Day	15% 7% 34% 29% 15% 1	270
	21st to end	Day	16% 13% 32% 24% 12% 3	297
November	1st to 10th	Day	16% 7% 28% 34% 12% 3	270
	11th to 20th	Day	13% 8% 32% 37% 8% 1	225
	21st to end	Day	5% 8% 41% 31% 10% 6%	180
December	1st to 10th	Day	7% 7% 34% 32% 15% 4	180
	11th to 20th	Day	11% 9% 28% 33% 18% 1	180
	21st to end	Day	11% 4 24% 39% 17% 6%	198
January	1st to 10th	Night	12% 6% 31% 36% 13% 2	950
	11th to 20th	Night	9% 8% 32% 36% 13% 1	950
	21st to end	Night	14% 10% 32% 32% 10% 2	1010
February	1st to 10th	Night	12% 7% 28% 34% 17% 3	760
	11th to 20th	Night	11% 6% 31% 36% 16% 1	744
	21st to end	Night	7% 4 27% 38% 20% 5%	628
March	1st to 10th	Night	10% 6% 26% 40% 15% 2	760
	11th to 20th	Night	11% 5% 31% 35% 16% 3	760
	21st to end	Night	13% 6% 25% 36% 17% 3	836
April	1st to 10th	Night	10% 8% 29% 33% 17% 3	618
	11th to 20th	Night	15% 4 31% 34% 15% 1	563
	21st to end	Night	19% 5% 24% 38% 14% 1	570
May	1st to 10th	Night	19% 7% 20% 34% 17% 3	470
	11th to 20th	Night	15% 5% 21% 41% 18% 2	374
	21st to end	Night	19% 6% 20% 34% 19% 1	411
June	1st to 10th	Night	19% 6% 22% 37% 16% 2	380
	11th to 20th	Night	21% 6% 23% 30% 19% 2	380
	21st to end	Night	12% 3 21% 34% 26% 4	380
July	1st to 10th	Night	13% 2 17% 41% 26% 1	370
	11th to 20th	Night	12% 3 18% 45% 21% 2	368
	21st to end	Night	10% 3 17% 41% 25% 4	416
August	1st to 10th	Night	11% 2 13% 39% 30% 4	378
	11th to 20th	Night	12% 5% 16% 41% 23% 3	537
	21st to end	Night	11% 3 22% 40% 22% 2	627
September	1st to 10th	Night	13% 4 22% 35% 24% 2	570
	11th to 20th	Night	14% 3 21% 44% 17% 1	738
	21st to end	Night	11% 5% 31% 37% 16% 1	756
October	1st to 10th	Night	16% 4 28% 35% 17% 1	720
	11th to 20th	Night	13% 5% 31% 37% 13% 2	720
	21st to end	Night	14% 7% 33% 33% 12% 1	846
November	1st to 10th	Night	20% 7% 29% 33% 10% 2	925
	11th to 20th	Night	15% 7% 31% 31% 12% 3	950
	21st to end	Night	9% 6% 39% 32% 11% 2	950
December	1st to 10th	Night	14% 8% 31% 29% 15% 4	950
	11th to 20th	Night	12% 7% 32% 34% 13% 2	950
	21st to end	Night	11% 4 29% 37% 15% 4	1045

Page generated at 2024-09-26 07:52:19. Version ac07

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