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 2024-02-10.

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% 4 8% 7% 4 6% 6% 6% 8% 33%	77621
	Night	8% 9% 4 8% 7% 4 6% 6% 6% 8% 33%	81296
Transparency	Day	47% 7% 17% 22% 7% 1	77323
	Night	47% 7% 16% 21% 9% 1	81174
Seeing	Day	14% 7% 25% 31% 18% 6%	14416
	Night	13% 6% 27% 36% 16% 2	23691

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% 13% 13% 6% 7% 5% 5% 7% 22%	2219
	11th to 20th	Day	5% 8% 3 8% 9% 5% 9% 11% 10% 8% 23%	2199
	21st to end	Day	7% 12% 5% 9% 9% 4 6% 5% 5% 7% 31%	2520
February	1st to 10th	Day	8% 14% 6% 11% 10% 5% 6% 5% 6% 8% 22%	1512
	11th to 20th	Day	6% 14% 7% 11% 7% 5% 6% 7% 7% 8% 24%	1575
	21st to end	Day	5% 12% 6% 10% 8% 5% 7% 7% 8% 8% 24%	1332
March	1st to 10th	Day	8% 12% 6% 10% 10% 5% 6% 6% 7% 8% 21%	1817
	11th to 20th	Day	8% 11% 6% 9% 6% 4 5% 4 6% 7% 34%	1979
	21st to end	Day	10% 13% 6% 12% 8% 4 6% 5% 6% 7% 25%	2178
April	1st to 10th	Day	9% 12% 6% 8% 7% 5% 6% 6% 6% 8% 29%	2265
	11th to 20th	Day	13% 11% 5% 7% 7% 3 4 5% 6% 8% 31%	2310
	21st to end	Day	13% 10% 3 7% 6% 3 5% 6% 6% 7% 34%	2353
May	1st to 10th	Day	11% 9% 4 8% 7% 4 6% 6% 7% 7% 30%	2612
	11th to 20th	Day	10% 6% 3 6% 6% 4 6% 6% 7% 8% 40%	2654
	21st to end	Day	17% 7% 3 6% 6% 3 6% 5% 5% 7% 35%	2917
June	1st to 10th	Day	14% 9% 4 6% 7% 4 6% 6% 7% 7% 31%	2700
	11th to 20th	Day	19% 8% 4 8% 7% 4 6% 6% 6% 8% 24%	2700
	21st to end	Day	10% 6% 2 6% 7% 4 6% 7% 9% 10% 33%	2700
July	1st to 10th	Day	10% 6% 2 6% 6% 4 6% 6% 7% 8% 39%	2700
	11th to 20th	Day	10% 6% 2 5% 5% 4 6% 7% 7% 10% 37%	2700
	21st to end	Day	9% 5% 2 5% 5% 3 5% 5% 6% 10% 45%	2938
August	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 6% 7% 10% 39%	2638
	11th to 20th	Day	9% 4 2 6% 4 4 6% 6% 6% 9% 44%	2325
	21st to end	Day	11% 6% 2 5% 5% 3 5% 5% 6% 9% 43%	2574
September	1st to 10th	Day	12% 5% 4 6% 6% 4 4 6% 7% 7% 41%	2286
	11th to 20th	Day	14% 7% 3 6% 5% 3 5% 5% 5% 8% 40%	1998
	21st to end	Day	9% 6% 2 6% 5% 3 4 5% 6% 9% 44%	1980
October	1st to 10th	Day	12% 10% 3 7% 6% 3 5% 5% 5% 6% 37%	1830
	11th to 20th	Day	10% 8% 4 8% 6% 3 4 5% 5% 8% 39%	1704
	21st to end	Day	9% 12% 4 9% 7% 4 5% 6% 6% 7% 31%	1709
November	1st to 10th	Day	10% 14% 5% 8% 7% 5% 7% 6% 5% 7% 27%	1488
	11th to 20th	Day	8% 10% 5% 12% 10% 4 6% 5% 5% 7% 28%	1425
	21st to end	Day	5% 10% 6% 12% 8% 3 6% 6% 6% 7% 30%	1330
December	1st to 10th	Day	7% 11% 5% 10% 10% 5% 8% 7% 6% 7% 24%	1330
	11th to 20th	Day	8% 9% 5% 10% 10% 5% 7% 7% 7% 8% 25%	1682
	21st to end	Day	3 8% 4 8% 7% 4 5% 5% 5% 7% 43%	2442
January	1st to 10th	Night	5% 11% 5% 14% 10% 6% 8% 7% 6% 8% 21%	4726
	11th to 20th	Night	3 7% 4 8% 10% 6% 7% 9% 6% 7% 32%	4699
	21st to end	Night	7% 11% 5% 10% 7% 4 6% 5% 6% 8% 31%	5153
February	1st to 10th	Night	6% 11% 5% 11% 9% 6% 8% 6% 6% 8% 25%	2652
	11th to 20th	Night	7% 10% 5% 9% 8% 6% 7% 6% 7% 7% 27%	2272
	21st to end	Night	3 9% 5% 10% 8% 5% 6% 7% 7% 9% 30%	1924
March	1st to 10th	Night	7% 9% 5% 11% 10% 4 7% 6% 6% 8% 27%	2142
	11th to 20th	Night	7% 10% 5% 9% 8% 4 7% 6% 6% 7% 32%	1980
	21st to end	Night	9% 11% 5% 9% 7% 4 6% 5% 7% 8% 28%	2178
April	1st to 10th	Night	6% 10% 4 7% 6% 4 7% 6% 6% 8% 37%	1693
	11th to 20th	Night	10% 9% 4 8% 8% 4 6% 6% 7% 8% 30%	1601
	21st to end	Night	15% 9% 3 6% 5% 4 5% 5% 6% 7% 35%	1607
May	1st to 10th	Night	13% 8% 3 6% 5% 5% 5% 7% 7% 8% 32%	1346
	11th to 20th	Night	11% 7% 3 7% 6% 3 5% 7% 6% 7% 39%	1239
	21st to end	Night	17% 7% 4 7% 7% 4 6% 4 5% 6% 33%	1358
June	1st to 10th	Night	14% 8% 3 7% 6% 4 6% 5% 7% 8% 31%	1260
	11th to 20th	Night	16% 9% 4 8% 7% 4 8% 6% 7% 8% 24%	1260
	21st to end	Night	9% 5% 3 5% 4 4 6% 8% 8% 10% 38%	1260
July	1st to 10th	Night	11% 5% 2 5% 5% 4 5% 5% 7% 10% 40%	1260
	11th to 20th	Night	9% 4 3 5% 5% 4 6% 7% 8% 12% 38%	1260
	21st to end	Night	8% 4 2 4 3 3 4 6% 8% 10% 48%	1379
August	1st to 10th	Night	8% 4 2 5% 6% 4 5% 7% 8% 11% 40%	1299
	11th to 20th	Night	12% 5% 2 5% 6% 3 5% 5% 5% 9% 43%	1576
	21st to end	Night	9% 5% 2 5% 6% 4 5% 6% 6% 8% 45%	1782
September	1st to 10th	Night	12% 5% 2 7% 5% 3 4 5% 5% 7% 45%	1673
	11th to 20th	Night	12% 5% 2 4 5% 3 5% 4 6% 7% 47%	1959
	21st to end	Night	7% 5% 2 5% 6% 3 5% 5% 6% 8% 47%	1980
October	1st to 10th	Night	12% 7% 3 5% 5% 4 5% 6% 6% 7% 40%	2129
	11th to 20th	Night	9% 9% 3 7% 5% 3 5% 6% 7% 7% 39%	2254
	21st to end	Night	9% 10% 5% 8% 6% 4 5% 5% 7% 9% 33%	2628
November	1st to 10th	Night	13% 15% 6% 8% 6% 4 5% 5% 5% 7% 27%	2590
	11th to 20th	Night	9% 12% 4 10% 10% 4 6% 5% 6% 8% 25%	2753
	21st to end	Night	5% 11% 6% 10% 10% 4 6% 5% 5% 8% 29%	2850
December	1st to 10th	Night	8% 11% 5% 11% 9% 4 6% 5% 6% 8% 27%	2850
	11th to 20th	Night	6% 11% 5% 13% 10% 5% 7% 6% 5% 8% 23%	3510
	21st to end	Night	4 7% 4 7% 7% 4 6% 5% 6% 8% 44%	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% 6% 12% 15% 7%	1512
	11th to 20th	Day	56% 5% 17% 15% 7%	1584
	21st to end	Day	53% 6% 13% 20% 8%	1332
March	1st to 10th	Day	59% 7% 16% 14% 4	1817
	11th to 20th	Day	49% 5% 16% 21% 10%	1980
	21st to end	Day	58% 7% 13% 17% 4	2178
April	1st to 10th	Day	52% 7% 15% 18% 7% 1	2265
	11th to 20th	Day	50% 5% 15% 21% 8% 1	2310
	21st to end	Day	47% 6% 15% 23% 8% 1	2353
May	1st to 10th	Day	50% 7% 13% 21% 9% 1	2612
	11th to 20th	Day	40% 6% 13% 29% 11% 1	2658
	21st to end	Day	47% 6% 13% 23% 11% 1	2918
June	1st to 10th	Day	50% 7% 14% 21% 9%	2700
	11th to 20th	Day	56% 8% 15% 17% 4 1	2700
	21st to end	Day	42% 9% 22% 21% 6% 1	2700
July	1st to 10th	Day	38% 9% 23% 25% 4 1	2626
	11th to 20th	Day	40% 10% 27% 21% 2	2619
	21st to end	Day	34% 8% 27% 28% 2	2775
August	1st to 10th	Day	38% 10% 26% 23% 3	2620
	11th to 20th	Day	35% 8% 27% 24% 6%	2325
	21st to end	Day	37% 7% 22% 28% 5% 1	2574
September	1st to 10th	Day	40% 7% 20% 24% 7% 2	2286
	11th to 20th	Day	42% 6% 17% 29% 6%	1998
	21st to end	Day	36% 7% 18% 29% 8% 2	1980
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	2652
	11th to 20th	Night	53% 7% 14% 17% 9%	2273
	21st to end	Night	48% 7% 13% 22% 9% 1	1924
March	1st to 10th	Night	53% 7% 14% 19% 6%	2142
	11th to 20th	Night	49% 6% 10% 23% 10% 1	1980
	21st to end	Night	50% 7% 15% 19% 8% 1	2178
April	1st to 10th	Night	43% 7% 15% 22% 13% 1	1693
	11th to 20th	Night	50% 6% 12% 20% 9% 3	1601
	21st to end	Night	46% 6% 14% 21% 10% 3	1607
May	1st to 10th	Night	46% 6% 13% 24% 10% 1	1346
	11th to 20th	Night	40% 7% 11% 27% 13% 2	1239
	21st to end	Night	51% 6% 10% 21% 10% 1	1358
June	1st to 10th	Night	50% 7% 12% 22% 8% 1	1260
	11th to 20th	Night	54% 8% 15% 17% 6%	1260
	21st to end	Night	36% 12% 22% 24% 5% 1	1260
July	1st to 10th	Night	36% 8% 22% 25% 7% 1	1225
	11th to 20th	Night	37% 11% 23% 23% 6%	1218
	21st to end	Night	27% 8% 27% 32% 4	1302
August	1st to 10th	Night	35% 9% 26% 26% 3	1292
	11th to 20th	Night	37% 7% 24% 25% 7%	1576
	21st to end	Night	36% 8% 17% 30% 10%	1782
September	1st to 10th	Night	37% 6% 20% 25% 9% 3	1673
	11th to 20th	Night	36% 6% 17% 30% 10% 2	1959
	21st to end	Night	34% 7% 16% 28% 13% 3	1980
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	10% 9% 27% 37% 13% 4	178
	11th to 20th	Day	13% 8% 32% 31% 12% 4	240
	21st to end	Day	11% 5% 26% 28% 22% 9%	198
March	1st to 10th	Day	11% 8% 29% 33% 16% 3	415
	11th to 20th	Day	11% 6% 31% 30% 14% 6%	420
	21st to end	Day	15% 5% 28% 30% 18% 4	462
April	1st to 10th	Day	10% 9% 33% 31% 15% 2	420
	11th to 20th	Day	18% 7% 22% 34% 14% 5%	412
	21st to end	Day	18% 10% 24% 31% 13% 3	433
May	1st to 10th	Day	14% 9% 23% 31% 17% 6%	603
	11th to 20th	Day	11% 6% 25% 32% 19% 7%	625
	21st to end	Day	19% 6% 21% 27% 19% 7%	679
June	1st to 10th	Day	18% 7% 24% 32% 16% 3	630
	11th to 20th	Day	20% 8% 24% 26% 15% 7%	630
	21st to end	Day	11% 6% 19% 31% 22% 11%	630
July	1st to 10th	Day	12% 4 18% 32% 27% 8%	621
	11th to 20th	Day	12% 5% 20% 33% 24% 6%	618
	21st to end	Day	10% 4 18% 31% 27% 10%	684
August	1st to 10th	Day	14% 4 15% 30% 25% 11%	578
	11th to 20th	Day	10% 5% 22% 33% 22% 7%	437
	21st to end	Day	14% 4 20% 29% 23% 10%	495
September	1st to 10th	Day	13% 8% 30% 28% 16% 5%	450
	11th to 20th	Day	19% 8% 22% 31% 16% 4	450
	21st to end	Day	13% 12% 30% 26% 16% 3	450
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% 27% 35% 16% 3	758
	11th to 20th	Night	11% 6% 32% 34% 15% 1	704
	21st to end	Night	7% 3 27% 38% 20% 5%	592
March	1st to 10th	Night	10% 5% 26% 41% 16% 2	720
	11th to 20th	Night	11% 5% 31% 34% 17% 3	720
	21st to end	Night	14% 6% 24% 35% 18% 3	792
April	1st to 10th	Night	9% 7% 28% 34% 18% 3	586
	11th to 20th	Night	15% 4 31% 34% 15% 1	533
	21st to end	Night	19% 5% 23% 38% 14% 1	540
May	1st to 10th	Night	17% 7% 20% 34% 18% 3	446
	11th to 20th	Night	15% 4 21% 41% 18% 2	354
	21st to end	Night	21% 5% 19% 34% 19% 1	389
June	1st to 10th	Night	19% 6% 19% 38% 16% 2	360
	11th to 20th	Night	21% 6% 23% 30% 19% 2	360
	21st to end	Night	12% 3 19% 35% 27% 4	360
July	1st to 10th	Night	13% 2 17% 41% 25% 1	350
	11th to 20th	Night	12% 2 19% 45% 20% 1	348
	21st to end	Night	9% 3 17% 41% 26% 4	394
August	1st to 10th	Night	11% 3 13% 39% 30% 4	358
	11th to 20th	Night	13% 5% 17% 40% 22% 3	508
	21st to end	Night	11% 3 21% 40% 23% 2	594
September	1st to 10th	Night	14% 4 22% 34% 24% 2	540
	11th to 20th	Night	13% 3 21% 44% 18% 1	699
	21st to end	Night	11% 5% 29% 38% 16% 1	720
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 2024-02-07 04:11:55. Version ac07

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