Yellowknife
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yellowknife clear sky chart from 2005-11-06 to 2024-11-03.

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	8% 9% 4 9% 6% 6% 6% 5% 7% 8% 35%	103146
	Night	7% 11% 4 11% 7% 6% 6% 5% 7% 8% 28%	95872
Transparency	Day	46% 7% 14% 24% 8%	102830
	Night	52% 7% 14% 20% 7%	95834
Seeing	Day	11% 5% 19% 31% 25% 10%	17136
	Night	12% 4 21% 34% 23% 6%	24434

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 7% 4 12% 9% 8% 15% 10% 8% 10% 14%	1259
	11th to 20th	Day	4 8% 4 10% 6% 6% 8% 8% 13% 12% 21%	1515
	21st to end	Day	6% 17% 5% 14% 8% 7% 6% 4 6% 5% 20%	2037
February	1st to 10th	Day	3 8% 5% 12% 8% 7% 6% 6% 9% 10% 26%	1239
	11th to 20th	Day	2 11% 5% 12% 8% 8% 8% 6% 9% 7% 23%	1479
	21st to end	Day	2 8% 5% 14% 9% 7% 6% 5% 8% 9% 26%	1333
March	1st to 10th	Day	4 10% 4 11% 7% 7% 7% 7% 9% 11% 23%	3042
	11th to 20th	Day	5% 12% 4 13% 8% 7% 6% 5% 7% 7% 25%	3359
	21st to end	Day	2 7% 3 7% 6% 6% 7% 6% 7% 8% 42%	4024
April	1st to 10th	Day	5% 11% 5% 9% 6% 5% 7% 4 6% 8% 34%	2442
	11th to 20th	Day	5% 8% 3 8% 6% 6% 5% 5% 6% 7% 41%	2522
	21st to end	Day	4 8% 3 9% 7% 7% 5% 4 7% 8% 38%	2850
May	1st to 10th	Day	5% 8% 3 7% 5% 4 4 3 5% 6% 49%	4853
	11th to 20th	Day	8% 9% 3 9% 6% 6% 5% 4 6% 7% 38%	5330
	21st to end	Day	11% 7% 2 5% 3 4 4 4 6% 8% 46%	5882
June	1st to 10th	Day	11% 8% 3 7% 6% 5% 5% 4 7% 7% 37%	3515
	11th to 20th	Day	10% 7% 3 8% 6% 6% 6% 4 7% 8% 37%	3610
	21st to end	Day	9% 5% 2 6% 5% 4 5% 4 7% 8% 44%	3610
July	1st to 10th	Day	7% 7% 3 10% 7% 7% 7% 5% 8% 9% 30%	5764
	11th to 20th	Day	7% 6% 2 5% 4 4 5% 3 5% 7% 51%	5572
	21st to end	Day	8% 6% 2 6% 5% 5% 6% 5% 8% 9% 38%	5755
August	1st to 10th	Day	5% 5% 2 5% 4 5% 6% 4 6% 7% 53%	4957
	11th to 20th	Day	19% 7% 3 5% 3 4 4 3 5% 6% 41%	4628
	21st to end	Day	9% 9% 5% 10% 7% 7% 6% 5% 6% 9% 26%	4722
September	1st to 10th	Day	13% 10% 4 9% 5% 5% 5% 5% 7% 9% 29%	2470
	11th to 20th	Day	13% 12% 4 9% 6% 4 4 4 6% 7% 30%	2193
	21st to end	Day	17% 13% 5% 8% 6% 6% 6% 4 5% 7% 25%	2090
October	1st to 10th	Day	12% 16% 5% 10% 6% 6% 5% 4 6% 7% 22%	1826
	11th to 20th	Day	12% 18% 7% 13% 6% 5% 4 5% 4 6% 20%	1701
	21st to end	Day	12% 20% 7% 15% 6% 5% 6% 3 5% 5% 15%	1567
November	1st to 10th	Day	9% 16% 9% 16% 9% 6% 4 4 6% 6% 14%	1286
	11th to 20th	Day	9% 17% 5% 16% 10% 8% 5% 5% 6% 5% 14%	1037
	21st to end	Day	8% 15% 8% 17% 8% 7% 7% 6% 5% 6% 13%	950
December	1st to 10th	Day	6% 15% 5% 15% 9% 8% 7% 5% 7% 7% 15%	837
	11th to 20th	Day	4 12% 4 16% 7% 7% 6% 9% 7% 10% 19%	716
	21st to end	Day	5% 13% 5% 13% 10% 8% 10% 6% 6% 7% 17%	1174
January	1st to 10th	Night	3 9% 4 14% 10% 9% 10% 7% 8% 8% 17%	5686
	11th to 20th	Night	4 9% 4 10% 8% 6% 8% 6% 10% 12% 23%	5383
	21st to end	Night	4 12% 5% 14% 10% 8% 6% 4 6% 8% 24%	5616
February	1st to 10th	Night	3 7% 4 10% 9% 6% 7% 6% 9% 11% 29%	2940
	11th to 20th	Night	4 10% 5% 11% 7% 7% 6% 6% 9% 10% 26%	2605
	21st to end	Night	2 10% 5% 13% 10% 7% 7% 4 8% 8% 26%	2121
March	1st to 10th	Night	2 7% 3 15% 8% 7% 6% 6% 9% 9% 27%	3826
	11th to 20th	Night	5% 12% 5% 11% 7% 6% 6% 4 6% 6% 33%	3620
	21st to end	Night	2 5% 1 6% 4 4 5% 4 5% 7% 56%	3626
April	1st to 10th	Night	4 11% 4 10% 5% 5% 5% 5% 6% 7% 39%	1738
	11th to 20th	Night	5% 7% 2 6% 6% 6% 5% 5% 6% 8% 43%	1608
	21st to end	Night	4 7% 2 8% 7% 5% 4 4 8% 7% 44%	1330
May	1st to 10th	Night	7% 6% 2 7% 5% 5% 5% 3 7% 8% 45%	2105
	11th to 20th	Night	7% 8% 3 9% 6% 6% 7% 6% 7% 8% 35%	1565
	21st to end	Night	9% 7% 2 5% 4 4 4 4 5% 6% 49%	1691
June	1st to 10th	Night	12% 6% 2 6% 5% 4 5% 4 8% 9% 39%	665
	11th to 20th	Night	8% 7% 2 7% 4 4 5% 4 7% 9% 42%	570
	21st to end	Night	6% 5% 2 6% 5% 6% 6% 6% 6% 11% 42%	570
July	1st to 10th	Night	5% 4 3 10% 7% 7% 6% 5% 7% 11% 35%	1193
	11th to 20th	Night	7% 4 1 5% 4 4 4 4 5% 8% 53%	1387
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 4 7% 11% 44%	1795
August	1st to 10th	Night	4 3 2 4 4 4 4 4 6% 8% 58%	1973
	11th to 20th	Night	16% 7% 2 5% 4 3 4 3 5% 6% 45%	2196
	21st to end	Night	11% 9% 3 9% 5% 6% 5% 5% 6% 9% 31%	2939
September	1st to 10th	Night	10% 9% 3 8% 5% 5% 6% 4 6% 9% 36%	1710
	11th to 20th	Night	11% 8% 3 9% 5% 6% 6% 5% 7% 8% 33%	1984
	21st to end	Night	15% 11% 3 9% 6% 5% 6% 4 6% 7% 28%	2090
October	1st to 10th	Night	12% 14% 4 11% 7% 5% 5% 3 6% 7% 27%	2351
	11th to 20th	Night	13% 17% 5% 12% 7% 5% 5% 4 4 5% 23%	2470
	21st to end	Night	12% 18% 7% 15% 7% 5% 4 3 5% 5% 17%	3020
November	1st to 10th	Night	12% 18% 6% 17% 9% 6% 5% 4 5% 5% 13%	2835
	11th to 20th	Night	10% 15% 6% 15% 11% 9% 8% 5% 5% 5% 13%	3140
	21st to end	Night	7% 17% 7% 18% 8% 8% 6% 5% 7% 8% 10%	3230
December	1st to 10th	Night	6% 17% 6% 16% 10% 8% 6% 5% 5% 7% 14%	3338
	11th to 20th	Night	6% 14% 5% 14% 8% 6% 8% 5% 8% 8% 18%	4476
	21st to end	Night	7% 13% 5% 12% 9% 8% 7% 5% 6% 7% 22%	6480

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	59% 8% 16% 15% 2	1259
	11th to 20th	Day	44% 9% 13% 24% 9%	1530
	21st to end	Day	63% 6% 8% 12% 10%	2037
February	1st to 10th	Day	49% 7% 12% 23% 9%	1239
	11th to 20th	Day	52% 7% 16% 18% 6%	1487
	21st to end	Day	51% 7% 11% 22% 8% 1	1333
March	1st to 10th	Day	51% 8% 12% 23% 5% 1	3042
	11th to 20th	Day	53% 5% 12% 18% 11%	3360
	21st to end	Day	36% 6% 12% 33% 13%	4024
April	1st to 10th	Day	47% 6% 14% 23% 9% 1	2442
	11th to 20th	Day	39% 8% 14% 33% 6%	2522
	21st to end	Day	40% 10% 16% 28% 7%	2850
May	1st to 10th	Day	34% 7% 13% 29% 16%	4853
	11th to 20th	Day	43% 7% 11% 28% 11% 1	5334
	21st to end	Day	34% 6% 10% 27% 21% 2	5883
June	1st to 10th	Day	44% 7% 13% 27% 9%	3515
	11th to 20th	Day	41% 9% 14% 25% 10% 1	3610
	21st to end	Day	36% 9% 15% 28% 12% 1	3610
July	1st to 10th	Day	50% 7% 16% 24% 4	5675
	11th to 20th	Day	31% 7% 15% 37% 11%	5473
	21st to end	Day	38% 7% 19% 31% 5%	5573
August	1st to 10th	Day	31% 6% 17% 30% 16%	4938
	11th to 20th	Day	44% 6% 13% 27% 9%	4673
	21st to end	Day	55% 9% 22% 14%	4721
September	1st to 10th	Day	51% 11% 22% 15% 1	2470
	11th to 20th	Day	52% 9% 19% 19% 1	2193
	21st to end	Day	59% 9% 18% 12% 3	2090
October	1st to 10th	Day	62% 8% 18% 10% 2	1826
	11th to 20th	Day	65% 8% 14% 12%	1701
	21st to end	Day	73% 8% 11% 8% 1	1567
November	1st to 10th	Day	71% 7% 10% 10% 2	1286
	11th to 20th	Day	71% 8% 12% 8% 2	1037
	21st to end	Day	68% 9% 11% 10% 2	950
December	1st to 10th	Day	66% 8% 9% 13% 4	837
	11th to 20th	Day	56% 7% 12% 20% 5%	716
	21st to end	Day	63% 7% 12% 15% 3	1174
January	1st to 10th	Night	59% 7% 13% 16% 5%	5686
	11th to 20th	Night	48% 7% 16% 22% 7%	5430
	21st to end	Night	58% 4 8% 17% 13%	5616
February	1st to 10th	Night	45% 8% 14% 21% 10% 1	2940
	11th to 20th	Night	50% 8% 16% 19% 7%	2607
	21st to end	Night	53% 6% 12% 18% 10% 1	2121
March	1st to 10th	Night	48% 8% 15% 23% 5% 1	3826
	11th to 20th	Night	48% 7% 12% 19% 13%	3620
	21st to end	Night	26% 5% 13% 34% 22%	3626
April	1st to 10th	Night	42% 5% 14% 25% 14%	1738
	11th to 20th	Night	36% 7% 11% 35% 10% 1	1608
	21st to end	Night	35% 7% 14% 32% 12%	1330
May	1st to 10th	Night	33% 8% 16% 28% 14%	2105
	11th to 20th	Night	43% 7% 15% 26% 8%	1565
	21st to end	Night	32% 5% 10% 29% 23% 1	1691
June	1st to 10th	Night	37% 8% 15% 28% 12%	665
	11th to 20th	Night	36% 7% 17% 30% 10%	570
	21st to end	Night	34% 11% 15% 29% 11% 1	570
July	1st to 10th	Night	43% 6% 22% 24% 5%	1173
	11th to 20th	Night	28% 6% 14% 39% 13%	1363
	21st to end	Night	33% 6% 17% 38% 6%	1738
August	1st to 10th	Night	23% 6% 21% 30% 19%	1967
	11th to 20th	Night	41% 7% 13% 27% 12%	2217
	21st to end	Night	50% 6% 25% 17%	2939
September	1st to 10th	Night	42% 10% 26% 20% 2	1710
	11th to 20th	Night	47% 10% 20% 20% 3	1984
	21st to end	Night	56% 9% 18% 16% 2	2090
October	1st to 10th	Night	57% 8% 18% 14% 2	2351
	11th to 20th	Night	64% 7% 16% 12% 1	2470
	21st to end	Night	71% 7% 12% 10%	3020
November	1st to 10th	Night	74% 6% 9% 9% 2	2835
	11th to 20th	Night	74% 9% 9% 6% 2	3140
	21st to end	Night	71% 7% 11% 9% 1	3230
December	1st to 10th	Night	68% 6% 12% 11% 4	3338
	11th to 20th	Night	60% 6% 11% 16% 7%	4475
	21st to end	Night	59% 7% 15% 15% 4	6480

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	6% 3 21% 37% 21% 12%	180
	11th to 20th	Day	9% 4 19% 33% 22% 13%	180
	21st to end	Day	11% 7% 17% 35% 24% 6%	198
February	1st to 10th	Day	4 2 15% 39% 28% 12%	180
	11th to 20th	Day	3 1 14% 42% 33% 7%	180
	21st to end	Day	4 3 14% 33% 32% 14%	187
March	1st to 10th	Day	5% 5% 16% 34% 27% 14%	398
	11th to 20th	Day	10% 4 21% 40% 18% 6%	460
	21st to end	Day	5% 4 24% 33% 23% 12%	506
April	1st to 10th	Day	8% 6% 28% 29% 18% 12%	460
	11th to 20th	Day	7% 4 13% 33% 32% 12%	456
	21st to end	Day	7% 4 23% 34% 25% 6%	650
May	1st to 10th	Day	12% 7% 24% 30% 21% 5%	705
	11th to 20th	Day	7% 5% 23% 33% 24% 8%	862
	21st to end	Day	10% 5% 20% 34% 24% 6%	940
June	1st to 10th	Day	14% 5% 20% 29% 25% 7%	870
	11th to 20th	Day	13% 2 21% 31% 24% 8%	870
	21st to end	Day	9% 4 16% 29% 29% 13%	870
July	1st to 10th	Day	9% 5% 18% 30% 28% 11%	856
	11th to 20th	Day	10% 3 15% 27% 29% 15%	852
	21st to end	Day	10% 3 14% 26% 31% 17%	947
August	1st to 10th	Day	9% 3 12% 27% 33% 17%	823
	11th to 20th	Day	19% 4 16% 27% 25% 9%	661
	21st to end	Day	12% 4 16% 27% 28% 13%	539
September	1st to 10th	Day	16% 5% 21% 28% 17% 12%	490
	11th to 20th	Day	17% 6% 19% 27% 20% 11%	490
	21st to end	Day	17% 7% 26% 32% 14% 4	490
October	1st to 10th	Day	17% 8% 25% 25% 17% 8%	340
	11th to 20th	Day	20% 9% 21% 28% 15% 7%	300
	21st to end	Day	15% 5% 24% 34% 18% 4	274
November	1st to 10th	Day	10% 4 24% 30% 23% 8%	184
	11th to 20th	Day	8% 9% 22% 31% 23% 7%	180
	21st to end	Day	11% 6% 27% 32% 16% 8%	180
December	1st to 10th	Day	10% 5% 23% 30% 24% 8%	147
	11th to 20th	Day	9% 4 12% 41% 29% 4	90
	21st to end	Day	4 5% 22% 29% 28% 12%	141
January	1st to 10th	Night	10% 3 20% 35% 23% 9%	1040
	11th to 20th	Night	12% 4 19% 36% 22% 7%	1040
	21st to end	Night	10% 3 27% 37% 17% 6%	1144
February	1st to 10th	Night	5% 3 22% 37% 24% 9%	992
	11th to 20th	Night	7% 3 23% 38% 25% 4	763
	21st to end	Night	5% 2 23% 39% 26% 6%	628
March	1st to 10th	Night	4 2 19% 37% 26% 11%	760
	11th to 20th	Night	7% 6% 22% 39% 22% 4	760
	21st to end	Night	6% 2 20% 42% 26% 4	836
April	1st to 10th	Night	7% 5% 26% 36% 21% 6%	598
	11th to 20th	Night	8% 2 18% 39% 29% 3	484
	21st to end	Night	5% 3 24% 44% 23% 1	380
May	1st to 10th	Night	9% 7% 26% 38% 18% 2	380
	11th to 20th	Night	9% 5% 27% 38% 20% 2	374
	21st to end	Night	9% 5% 22% 40% 23%	411
June	1st to 10th	Night	14% 3 20% 37% 24% 2	285
	11th to 20th	Night	13% 4 16% 36% 30% 1	190
	21st to end	Night	7% 2 16% 37% 36% 2	190
July	1st to 10th	Night	8% 3 16% 36% 33% 4	329
	11th to 20th	Night	11% 2 13% 39% 31% 5%	368
	21st to end	Night	7% 3 13% 31% 39% 6%	416
August	1st to 10th	Night	10% 1 10% 33% 39% 7%	378
	11th to 20th	Night	19% 2 13% 35% 25% 6%	376
	21st to end	Night	17% 3 14% 29% 32% 5%	498
September	1st to 10th	Night	14% 4 18% 32% 27% 5%	570
	11th to 20th	Night	14% 5% 20% 33% 23% 5%	731
	21st to end	Night	23% 4 27% 29% 14% 4	760
October	1st to 10th	Night	19% 4 22% 34% 17% 4	760
	11th to 20th	Night	20% 6% 22% 30% 17% 4	760
	21st to end	Night	18% 6% 24% 28% 21% 4	1035
November	1st to 10th	Night	18% 4 20% 31% 22% 5%	936
	11th to 20th	Night	15% 5% 23% 30% 20% 7%	998
	21st to end	Night	14% 6% 23% 29% 22% 7%	1040
December	1st to 10th	Night	13% 4 24% 33% 21% 6%	1040
	11th to 20th	Night	12% 4 21% 37% 21% 5%	1040
	21st to end	Night	10% 3 20% 29% 29% 9%	1144

Page generated at 2024-10-31 01:39:26. Version ac07

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