Strathcona Wilderness Centre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Strathcona Wilderness Centre clear sky chart from 2005-11-06 to 2024-04-10.

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	9% 9% 4 8% 7% 4 5% 5% 6% 8% 34%	82467
	Night	8% 9% 4 9% 8% 4 6% 6% 6% 8% 33%	86270
Transparency	Day	46% 9% 17% 21% 7% 1	82169
	Night	47% 8% 16% 20% 9% 1	86148
Seeing	Day	13% 6% 24% 31% 19% 7%	14623
	Night	12% 6% 28% 35% 16% 2	23852

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 11% 5% 11% 11% 5% 7% 6% 7% 8% 25%	2219
	11th to 20th	Day	4 9% 4 8% 8% 5% 6% 7% 9% 9% 30%	2199
	21st to end	Day	6% 13% 4 9% 8% 4 5% 4 5% 7% 36%	2581
February	1st to 10th	Day	8% 12% 7% 9% 11% 4 5% 6% 6% 8% 24%	1520
	11th to 20th	Day	5% 12% 8% 11% 7% 4 6% 6% 7% 7% 27%	1627
	21st to end	Day	4 11% 6% 11% 9% 4 8% 7% 5% 7% 27%	1444
March	1st to 10th	Day	4 10% 6% 12% 10% 4 6% 6% 6% 9% 27%	3138
	11th to 20th	Day	5% 11% 5% 8% 6% 3 4 4 5% 11% 38%	3483
	21st to end	Day	7% 13% 6% 16% 8% 4 5% 5% 5% 6% 25%	3845
April	1st to 10th	Day	9% 11% 5% 8% 7% 5% 6% 6% 6% 8% 30%	2379
	11th to 20th	Day	12% 12% 4 6% 6% 4 5% 5% 7% 8% 31%	2310
	21st to end	Day	12% 9% 4 6% 7% 4 6% 5% 7% 8% 32%	2340
May	1st to 10th	Day	10% 10% 4 8% 8% 4 6% 6% 6% 7% 31%	2632
	11th to 20th	Day	9% 5% 3 6% 6% 4 5% 6% 6% 8% 40%	2654
	21st to end	Day	16% 9% 3 6% 6% 4 5% 5% 5% 8% 34%	2917
June	1st to 10th	Day	15% 8% 4 8% 7% 4 5% 6% 6% 8% 31%	2700
	11th to 20th	Day	19% 9% 4 8% 8% 4 6% 6% 6% 7% 23%	2700
	21st to end	Day	11% 5% 2 6% 7% 3 6% 6% 8% 10% 36%	2731
July	1st to 10th	Day	11% 5% 2 6% 7% 4 5% 5% 6% 8% 39%	2700
	11th to 20th	Day	11% 5% 2 6% 6% 4 6% 6% 7% 10% 36%	2700
	21st to end	Day	9% 5% 2 5% 5% 3 5% 5% 7% 9% 44%	2938
August	1st to 10th	Day	10% 5% 2 5% 6% 3 6% 6% 8% 10% 38%	2598
	11th to 20th	Day	9% 4 2 5% 5% 4 5% 5% 7% 10% 43%	2358
	21st to end	Day	11% 5% 2 5% 5% 4 5% 5% 6% 9% 43%	2574
September	1st to 10th	Day	12% 6% 3 6% 5% 4 5% 5% 6% 8% 40%	2295
	11th to 20th	Day	14% 7% 3 5% 5% 4 4 5% 5% 7% 41%	1980
	21st to end	Day	8% 7% 3 6% 6% 3 5% 4 6% 8% 44%	1980
October	1st to 10th	Day	12% 8% 4 9% 7% 4 5% 5% 5% 5% 36%	1859
	11th to 20th	Day	9% 9% 4 7% 7% 3 4 4 6% 9% 38%	1666
	21st to end	Day	9% 12% 4 7% 7% 5% 6% 6% 6% 7% 31%	1742
November	1st to 10th	Day	9% 12% 7% 9% 7% 5% 6% 6% 5% 8% 27%	1488
	11th to 20th	Day	6% 11% 6% 12% 8% 5% 6% 4 6% 6% 29%	1386
	21st to end	Day	5% 9% 7% 12% 8% 3 5% 5% 6% 7% 32%	1330
December	1st to 10th	Day	5% 11% 6% 8% 10% 6% 8% 7% 5% 9% 25%	1330
	11th to 20th	Day	6% 10% 5% 10% 8% 5% 6% 7% 7% 9% 27%	1682
	21st to end	Day	4 7% 3 8% 7% 4 6% 5% 6% 8% 43%	2442
January	1st to 10th	Night	4 9% 5% 13% 11% 6% 8% 7% 7% 8% 24%	4726
	11th to 20th	Night	3 7% 4 9% 10% 6% 7% 7% 7% 7% 34%	4699
	21st to end	Night	6% 12% 5% 10% 7% 4 5% 5% 6% 8% 33%	5104
February	1st to 10th	Night	6% 9% 6% 12% 10% 6% 7% 6% 5% 7% 27%	2660
	11th to 20th	Night	5% 12% 5% 9% 7% 5% 6% 6% 7% 8% 30%	2440
	21st to end	Night	4 9% 5% 10% 9% 5% 7% 7% 6% 8% 31%	2008
March	1st to 10th	Night	4 10% 6% 10% 8% 4 6% 6% 7% 9% 29%	3736
	11th to 20th	Night	5% 7% 4 8% 8% 4 5% 6% 6% 10% 37%	3495
	21st to end	Night	6% 11% 7% 14% 9% 5% 6% 5% 6% 8% 23%	3804
April	1st to 10th	Night	7% 9% 4 7% 8% 5% 6% 6% 8% 8% 33%	1789
	11th to 20th	Night	10% 10% 5% 9% 8% 5% 6% 6% 6% 7% 29%	1601
	21st to end	Night	12% 10% 3 6% 6% 3 4 6% 6% 8% 35%	1620
May	1st to 10th	Night	13% 8% 4 7% 7% 6% 6% 7% 6% 5% 30%	1324
	11th to 20th	Night	10% 7% 3 8% 7% 4 7% 5% 6% 7% 37%	1239
	21st to end	Night	19% 7% 3 7% 6% 3 5% 5% 5% 7% 31%	1358
June	1st to 10th	Night	15% 8% 5% 6% 8% 4 5% 7% 6% 7% 29%	1260
	11th to 20th	Night	17% 8% 3 8% 8% 5% 7% 7% 7% 7% 23%	1260
	21st to end	Night	10% 6% 3 7% 5% 3 7% 5% 6% 10% 39%	1172
July	1st to 10th	Night	12% 6% 2 5% 6% 3 6% 6% 6% 9% 39%	1260
	11th to 20th	Night	10% 5% 3 6% 6% 4 6% 7% 7% 10% 36%	1260
	21st to end	Night	9% 4 3 4 4 4 5% 5% 7% 10% 46%	1379
August	1st to 10th	Night	10% 5% 3 5% 5% 4 5% 6% 7% 9% 41%	1338
	11th to 20th	Night	11% 5% 3 6% 5% 4 4 4 6% 8% 44%	1541
	21st to end	Night	11% 6% 2 5% 7% 4 4 5% 6% 8% 41%	1782
September	1st to 10th	Night	12% 5% 3 7% 5% 3 4 4 4 8% 45%	1661
	11th to 20th	Night	11% 6% 2 5% 5% 2 3 4 6% 9% 46%	1980
	21st to end	Night	9% 6% 3 6% 5% 3 4 5% 6% 8% 46%	1980
October	1st to 10th	Night	11% 8% 3 7% 6% 3 5% 4 6% 7% 40%	2101
	11th to 20th	Night	8% 8% 4 7% 7% 3 5% 6% 7% 7% 38%	2290
	21st to end	Night	8% 10% 4 8% 8% 4 5% 6% 6% 7% 33%	2596
November	1st to 10th	Night	12% 15% 5% 8% 7% 4 6% 5% 5% 6% 27%	2590
	11th to 20th	Night	7% 13% 6% 10% 8% 4 6% 5% 6% 6% 27%	2793
	21st to end	Night	5% 9% 6% 11% 9% 6% 7% 6% 6% 7% 29%	2850
December	1st to 10th	Night	7% 12% 5% 10% 9% 5% 6% 5% 6% 7% 28%	2850
	11th to 20th	Night	6% 11% 6% 12% 9% 5% 6% 6% 6% 9% 25%	3510
	21st to end	Night	3 7% 3 7% 7% 5% 6% 6% 6% 9% 42%	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	53% 9% 13% 19% 4 1	2219
	11th to 20th	Day	46% 6% 14% 16% 17% 1	2220
	21st to end	Day	47% 7% 19% 22% 5%	2581
February	1st to 10th	Day	56% 6% 15% 15% 8%	1520
	11th to 20th	Day	53% 8% 16% 15% 8%	1636
	21st to end	Day	52% 7% 12% 20% 8%	1444
March	1st to 10th	Day	53% 6% 15% 19% 7%	3138
	11th to 20th	Day	41% 7% 20% 22% 10%	3484
	21st to end	Day	56% 9% 11% 20% 3	3845
April	1st to 10th	Day	49% 9% 17% 18% 8% 1	2379
	11th to 20th	Day	49% 7% 16% 20% 8%	2310
	21st to end	Day	47% 8% 15% 22% 7% 1	2340
May	1st to 10th	Day	49% 8% 14% 19% 8% 1	2632
	11th to 20th	Day	39% 8% 12% 28% 11% 1	2658
	21st to end	Day	48% 8% 13% 21% 11%	2918
June	1st to 10th	Day	50% 7% 15% 20% 8%	2700
	11th to 20th	Day	56% 9% 16% 14% 4	2700
	21st to end	Day	40% 12% 22% 21% 6% 1	2731
July	1st to 10th	Day	40% 9% 20% 25% 5% 1	2626
	11th to 20th	Day	40% 13% 25% 21% 2	2619
	21st to end	Day	33% 11% 27% 26% 3	2775
August	1st to 10th	Day	37% 12% 27% 21% 3	2580
	11th to 20th	Day	32% 11% 25% 25% 6%	2358
	21st to end	Day	36% 10% 21% 26% 7% 1	2574
September	1st to 10th	Day	39% 10% 19% 24% 6% 2	2295
	11th to 20th	Day	41% 7% 19% 27% 7%	1980
	21st to end	Day	38% 9% 17% 26% 8% 2	1980
October	1st to 10th	Day	48% 7% 16% 20% 8%	1859
	11th to 20th	Day	42% 8% 17% 24% 10%	1666
	21st to end	Day	49% 10% 13% 22% 6%	1742
November	1st to 10th	Day	53% 9% 16% 15% 6% 1	1488
	11th to 20th	Day	55% 6% 15% 19% 5%	1386
	21st to end	Day	50% 8% 17% 19% 5% 1	1330
December	1st to 10th	Day	54% 9% 12% 16% 8% 1	1330
	11th to 20th	Day	50% 9% 17% 17% 7%	1684
	21st to end	Day	38% 6% 11% 28% 15% 1	2442
January	1st to 10th	Night	54% 9% 14% 16% 6% 1	4726
	11th to 20th	Night	46% 7% 15% 17% 14% 1	4740
	21st to end	Night	49% 7% 18% 19% 7%	5104
February	1st to 10th	Night	55% 7% 13% 16% 7% 1	2660
	11th to 20th	Night	49% 8% 15% 17% 11% 1	2441
	21st to end	Night	48% 8% 13% 21% 9% 1	2008
March	1st to 10th	Night	49% 7% 16% 20% 7%	3736
	11th to 20th	Night	40% 7% 22% 19% 11% 1	3495
	21st to end	Night	54% 10% 13% 16% 6%	3804
April	1st to 10th	Night	45% 9% 15% 20% 12% 1	1789
	11th to 20th	Night	51% 8% 12% 18% 9% 2	1601
	21st to end	Night	45% 7% 13% 22% 11% 2	1620
May	1st to 10th	Night	50% 8% 11% 21% 8% 1	1324
	11th to 20th	Night	43% 8% 10% 23% 14% 1	1239
	21st to end	Night	50% 8% 11% 19% 10% 2	1358
June	1st to 10th	Night	49% 9% 13% 20% 7% 1	1260
	11th to 20th	Night	57% 10% 13% 15% 5%	1260
	21st to end	Night	39% 9% 24% 21% 5% 1	1172
July	1st to 10th	Night	39% 10% 19% 24% 6% 2	1225
	11th to 20th	Night	40% 13% 21% 21% 4	1218
	21st to end	Night	30% 9% 26% 30% 5%	1302
August	1st to 10th	Night	37% 11% 24% 26% 3	1331
	11th to 20th	Night	37% 8% 23% 26% 6% 1	1541
	21st to end	Night	38% 9% 16% 27% 9% 1	1782
September	1st to 10th	Night	37% 9% 18% 25% 9% 2	1661
	11th to 20th	Night	35% 7% 17% 29% 9% 2	1980
	21st to end	Night	35% 9% 15% 26% 13% 2	1980
October	1st to 10th	Night	42% 7% 15% 25% 10% 1	2101
	11th to 20th	Night	42% 8% 16% 26% 8% 1	2290
	21st to end	Night	46% 9% 15% 22% 7% 1	2596
November	1st to 10th	Night	55% 8% 11% 19% 6%	2590
	11th to 20th	Night	55% 8% 12% 18% 6% 1	2793
	21st to end	Night	51% 9% 16% 18% 5% 1	2850
December	1st to 10th	Night	54% 7% 12% 17% 9% 1	2850
	11th to 20th	Night	54% 8% 17% 15% 6%	3507
	21st to end	Night	37% 7% 17% 19% 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	11% 3 29% 32% 21% 4	180
	11th to 20th	Day	9% 9% 33% 29% 17% 4	180
	21st to end	Day	11% 8% 33% 32% 11% 5%	198
February	1st to 10th	Day	13% 8% 30% 33% 13% 2	180
	11th to 20th	Day	10% 6% 31% 31% 17% 5%	252
	21st to end	Day	6% 6% 30% 30% 18% 10%	256
March	1st to 10th	Day	12% 6% 28% 32% 18% 4	460
	11th to 20th	Day	10% 5% 27% 35% 17% 7%	460
	21st to end	Day	12% 4 25% 33% 21% 4	506
April	1st to 10th	Day	11% 7% 25% 33% 17% 5%	457
	11th to 20th	Day	17% 5% 16% 31% 23% 9%	412
	21st to end	Day	15% 7% 19% 30% 22% 6%	420
May	1st to 10th	Day	11% 9% 22% 33% 20% 6%	584
	11th to 20th	Day	12% 5% 21% 34% 21% 8%	625
	21st to end	Day	17% 5% 19% 32% 18% 10%	679
June	1st to 10th	Day	17% 7% 22% 32% 17% 6%	630
	11th to 20th	Day	20% 7% 22% 23% 20% 8%	630
	21st to end	Day	14% 5% 17% 28% 25% 11%	661
July	1st to 10th	Day	12% 3 15% 32% 27% 10%	621
	11th to 20th	Day	11% 5% 20% 31% 24% 9%	618
	21st to end	Day	9% 4 18% 32% 26% 10%	684
August	1st to 10th	Day	12% 4 19% 29% 23% 13%	538
	11th to 20th	Day	9% 5% 23% 32% 24% 7%	437
	21st to end	Day	12% 5% 21% 31% 22% 10%	495
September	1st to 10th	Day	15% 10% 24% 28% 18% 5%	450
	11th to 20th	Day	18% 8% 23% 31% 16% 4	450
	21st to end	Day	12% 14% 28% 26% 15% 4	450
October	1st to 10th	Day	16% 7% 31% 27% 14% 6%	329
	11th to 20th	Day	11% 11% 30% 32% 13% 3	270
	21st to end	Day	15% 11% 34% 25% 12% 3	297
November	1st to 10th	Day	18% 6% 29% 33% 12% 3	270
	11th to 20th	Day	12% 7% 34% 34% 11% 2	206
	21st to end	Day	3 9% 41% 29% 12% 6%	180
December	1st to 10th	Day	9% 6% 32% 32% 17% 4	180
	11th to 20th	Day	7% 9% 32% 37% 12% 3	180
	21st to end	Day	8% 5% 24% 39% 20% 5%	198
January	1st to 10th	Night	10% 7% 33% 36% 13% 2	950
	11th to 20th	Night	10% 7% 35% 33% 14% 2	950
	21st to end	Night	12% 10% 34% 30% 12% 2	974
February	1st to 10th	Night	10% 9% 25% 36% 18% 3	760
	11th to 20th	Night	10% 5% 33% 35% 16% 1	744
	21st to end	Night	7% 5% 28% 34% 19% 6%	628
March	1st to 10th	Night	9% 5% 28% 39% 15% 3	760
	11th to 20th	Night	12% 4 31% 35% 14% 3	760
	21st to end	Night	12% 6% 27% 36% 16% 3	836
April	1st to 10th	Night	11% 7% 26% 35% 18% 3	649
	11th to 20th	Night	13% 6% 26% 37% 17% 1	533
	21st to end	Night	17% 6% 24% 36% 16% 2	540
May	1st to 10th	Night	15% 6% 21% 37% 18% 2	406
	11th to 20th	Night	12% 5% 23% 38% 18% 3	354
	21st to end	Night	20% 6% 20% 32% 20% 2	389
June	1st to 10th	Night	19% 7% 20% 38% 14% 2	360
	11th to 20th	Night	21% 5% 19% 33% 20% 2	360
	21st to end	Night	11% 4 20% 36% 25% 5%	360
July	1st to 10th	Night	15% 3 14% 43% 26% 1	350
	11th to 20th	Night	11% 3 20% 43% 22% 2	348
	21st to end	Night	12% 2 17% 40% 25% 4	394
August	1st to 10th	Night	13% 2 18% 33% 29% 6%	358
	11th to 20th	Night	13% 4 16% 39% 25% 3	473
	21st to end	Night	13% 2 19% 40% 25% 2	594
September	1st to 10th	Night	14% 2 22% 38% 22% 2	558
	11th to 20th	Night	14% 4 22% 40% 18% 2	720
	21st to end	Night	11% 5% 28% 40% 14% 2	720
October	1st to 10th	Night	15% 5% 28% 38% 14% 1	720
	11th to 20th	Night	13% 6% 33% 34% 13% 2	720
	21st to end	Night	13% 8% 33% 33% 12%	814
November	1st to 10th	Night	19% 7% 33% 30% 9% 2	925
	11th to 20th	Night	13% 8% 36% 30% 10% 3	950
	21st to end	Night	9% 6% 39% 33% 11% 2	950
December	1st to 10th	Night	12% 9% 33% 29% 14% 4	950
	11th to 20th	Night	11% 7% 33% 34% 14% 2	950
	21st to end	Night	10% 5% 32% 34% 16% 3	1045

Page generated at 2024-04-07 07:28:14. Version ac07

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