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 2024-03-23.

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 8% 7% 4 6% 6% 7% 8% 32%	76789
	Night	7% 10% 5% 10% 9% 5% 6% 6% 7% 8% 26%	83021
Transparency	Day	48% 9% 15% 21% 6%	76428
	Night	54% 7% 14% 18% 6%	82962
Seeing	Day	11% 4 19% 30% 25% 10%	16062
	Night	12% 4 21% 34% 24% 6%	23843

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 9% 11% 5% 15% 14% 8% 10% 14%	1259
	11th to 20th	Day	4 7% 4 8% 7% 4 8% 11% 13% 12% 21%	1515
	21st to end	Day	7% 16% 6% 12% 10% 6% 7% 5% 6% 5% 20%	2037
February	1st to 10th	Day	3 7% 5% 10% 10% 4 8% 7% 8% 11% 26%	1239
	11th to 20th	Day	2 9% 6% 11% 9% 6% 9% 8% 9% 8% 23%	1479
	21st to end	Day	3 8% 5% 12% 11% 5% 8% 6% 7% 9% 26%	1333
March	1st to 10th	Day	4 9% 4 8% 7% 5% 8% 8% 8% 9% 30%	1838
	11th to 20th	Day	5% 11% 4 10% 9% 5% 6% 6% 7% 8% 29%	2007
	21st to end	Day	4 9% 5% 8% 8% 5% 7% 8% 7% 7% 31%	2310
April	1st to 10th	Day	6% 10% 5% 7% 7% 4 7% 6% 6% 8% 34%	2313
	11th to 20th	Day	6% 7% 3 6% 7% 5% 5% 6% 6% 8% 41%	2386
	21st to end	Day	4 7% 4 8% 8% 5% 6% 5% 6% 9% 39%	2700
May	1st to 10th	Day	7% 9% 4 7% 6% 3 5% 5% 6% 8% 40%	2757
	11th to 20th	Day	6% 8% 4 6% 6% 4 5% 5% 7% 8% 42%	3010
	21st to end	Day	10% 5% 3 4 4 2 5% 5% 5% 7% 50%	3316
June	1st to 10th	Day	11% 7% 3 6% 7% 4 5% 5% 7% 8% 38%	3330
	11th to 20th	Day	10% 6% 3 7% 7% 4 5% 6% 6% 9% 37%	3420
	21st to end	Day	9% 5% 2 5% 6% 3 5% 5% 6% 8% 45%	3420
July	1st to 10th	Day	9% 7% 3 7% 7% 5% 7% 6% 7% 8% 35%	3276
	11th to 20th	Day	7% 7% 3 6% 7% 4 7% 6% 7% 9% 37%	3168
	21st to end	Day	8% 5% 3 5% 6% 3 6% 6% 8% 9% 41%	3292
August	1st to 10th	Day	8% 6% 3 5% 6% 4 5% 6% 7% 9% 42%	2826
	11th to 20th	Day	17% 8% 4 7% 6% 4 6% 5% 6% 7% 32%	2650
	21st to end	Day	12% 9% 4 8% 7% 5% 6% 6% 6% 9% 28%	2697
September	1st to 10th	Day	13% 9% 4 7% 6% 4 5% 6% 6% 10% 30%	2340
	11th to 20th	Day	13% 12% 5% 7% 7% 3 4 6% 6% 7% 30%	2078
	21st to end	Day	17% 12% 5% 7% 7% 4 7% 6% 5% 7% 24%	1980
October	1st to 10th	Day	12% 16% 5% 8% 8% 4 6% 5% 6% 7% 21%	1730
	11th to 20th	Day	12% 18% 7% 11% 8% 4 5% 5% 4 6% 20%	1612
	21st to end	Day	13% 20% 9% 13% 8% 4 6% 5% 4 5% 14%	1485
November	1st to 10th	Day	10% 15% 9% 14% 10% 5% 5% 5% 6% 6% 15%	1272
	11th to 20th	Day	9% 15% 7% 14% 11% 6% 7% 5% 7% 5% 14%	1037
	21st to end	Day	8% 14% 9% 15% 9% 5% 7% 8% 5% 7% 13%	950
December	1st to 10th	Day	6% 12% 7% 14% 11% 5% 8% 7% 7% 8% 15%	837
	11th to 20th	Day	4 11% 5% 13% 10% 4 7% 9% 7% 10% 19%	716
	21st to end	Day	5% 12% 5% 10% 13% 6% 9% 9% 6% 7% 17%	1174
January	1st to 10th	Night	4 8% 5% 11% 12% 7% 10% 10% 7% 8% 17%	5686
	11th to 20th	Night	4 7% 4 9% 9% 5% 8% 8% 10% 12% 23%	5383
	21st to end	Night	4 11% 6% 12% 11% 6% 7% 5% 6% 8% 24%	5616
February	1st to 10th	Night	3 6% 4 9% 9% 5% 6% 8% 9% 11% 29%	2940
	11th to 20th	Night	4 10% 5% 9% 9% 5% 6% 7% 9% 10% 26%	2605
	21st to end	Night	3 9% 6% 11% 11% 5% 8% 5% 8% 8% 27%	2121
March	1st to 10th	Night	3 6% 5% 9% 9% 6% 7% 6% 8% 8% 35%	2339
	11th to 20th	Night	4 9% 5% 9% 8% 5% 6% 6% 7% 7% 32%	2172
	21st to end	Night	4 6% 3 7% 6% 4 6% 7% 6% 8% 43%	2088
April	1st to 10th	Night	4 10% 5% 9% 6% 4 5% 6% 6% 7% 38%	1647
	11th to 20th	Night	5% 6% 3 6% 7% 5% 6% 6% 6% 8% 42%	1524
	21st to end	Night	4 6% 3 6% 8% 3 4 5% 8% 8% 45%	1260
May	1st to 10th	Night	7% 8% 4 8% 6% 4 5% 5% 7% 6% 39%	1201
	11th to 20th	Night	7% 5% 4 7% 6% 3 5% 6% 5% 9% 41%	885
	21st to end	Night	9% 6% 3 4 5% 3 4 4 4 7% 51%	957
June	1st to 10th	Night	12% 6% 2 6% 5% 4 4 5% 7% 10% 40%	630
	11th to 20th	Night	9% 7% 2 6% 6% 4 5% 5% 6% 9% 41%	540
	21st to end	Night	6% 5% 2 5% 6% 4 6% 7% 6% 11% 43%	540
July	1st to 10th	Night	7% 5% 3 8% 6% 4 5% 4 7% 10% 39%	681
	11th to 20th	Night	7% 6% 2 7% 8% 4 7% 6% 6% 8% 39%	791
	21st to end	Night	7% 4 3 5% 7% 4 5% 5% 7% 10% 44%	1023
August	1st to 10th	Night	6% 5% 3 4 6% 3 5% 6% 7% 10% 45%	1113
	11th to 20th	Night	14% 9% 3 7% 6% 3 4 6% 7% 7% 33%	1246
	21st to end	Night	12% 8% 3 6% 6% 4 4 5% 7% 10% 35%	1659
September	1st to 10th	Night	10% 8% 3 6% 6% 4 6% 5% 6% 9% 37%	1620
	11th to 20th	Night	11% 8% 3 7% 6% 4 6% 6% 7% 8% 33%	1879
	21st to end	Night	16% 11% 4 7% 8% 4 6% 5% 5% 7% 28%	1980
October	1st to 10th	Night	12% 14% 5% 10% 8% 4 5% 4 6% 7% 26%	2227
	11th to 20th	Night	14% 16% 5% 11% 8% 3 5% 5% 4 5% 24%	2340
	21st to end	Night	12% 18% 8% 13% 10% 4 5% 4 5% 5% 17%	2860
November	1st to 10th	Night	12% 16% 7% 15% 10% 5% 6% 5% 5% 5% 13%	2804
	11th to 20th	Night	11% 13% 7% 13% 12% 7% 8% 6% 6% 5% 13%	3140
	21st to end	Night	8% 15% 8% 16% 10% 6% 6% 6% 6% 8% 10%	3230
December	1st to 10th	Night	6% 15% 8% 14% 12% 7% 6% 6% 5% 7% 15%	3338
	11th to 20th	Night	6% 13% 6% 12% 9% 4 8% 7% 8% 8% 19%	4476
	21st to end	Night	7% 11% 6% 10% 10% 6% 8% 6% 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	47% 8% 13% 23% 8% 1	1838
	11th to 20th	Day	50% 6% 15% 22% 8%	2008
	21st to end	Day	48% 7% 15% 23% 6%	2310
April	1st to 10th	Day	47% 6% 14% 23% 9% 1	2313
	11th to 20th	Day	40% 8% 14% 33% 6%	2386
	21st to end	Day	40% 10% 16% 28% 6%	2700
May	1st to 10th	Day	42% 8% 14% 25% 11%	2757
	11th to 20th	Day	38% 7% 10% 31% 13% 1	3014
	21st to end	Day	33% 7% 10% 31% 18% 2	3317
June	1st to 10th	Day	43% 7% 13% 27% 9%	3330
	11th to 20th	Day	42% 9% 15% 24% 9% 1	3420
	21st to end	Day	36% 9% 15% 27% 12% 1	3420
July	1st to 10th	Day	45% 10% 15% 24% 5%	3187
	11th to 20th	Day	40% 12% 19% 24% 5%	3069
	21st to end	Day	34% 12% 22% 30% 2	3109
August	1st to 10th	Day	38% 11% 20% 24% 6%	2807
	11th to 20th	Day	50% 11% 17% 16% 5%	2650
	21st to end	Day	52% 13% 23% 13%	2697
September	1st to 10th	Day	50% 11% 22% 15% 1	2340
	11th to 20th	Day	52% 9% 20% 18% 1	2078
	21st to end	Day	59% 9% 18% 11% 3	1980
October	1st to 10th	Day	62% 8% 19% 9% 2	1730
	11th to 20th	Day	66% 8% 14% 11%	1612
	21st to end	Day	73% 8% 11% 7% 1	1485
November	1st to 10th	Day	71% 7% 10% 10% 2	1272
	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	43% 7% 16% 24% 8% 2	2339
	11th to 20th	Night	48% 7% 13% 22% 10%	2172
	21st to end	Night	37% 6% 17% 27% 12% 1	2088
April	1st to 10th	Night	43% 5% 14% 26% 12%	1647
	11th to 20th	Night	37% 8% 11% 34% 10% 1	1524
	21st to end	Night	35% 6% 14% 33% 12%	1260
May	1st to 10th	Night	40% 6% 15% 26% 11% 1	1201
	11th to 20th	Night	39% 6% 15% 27% 12% 1	885
	21st to end	Night	33% 5% 9% 33% 18% 1	957
June	1st to 10th	Night	37% 8% 14% 28% 13%	630
	11th to 20th	Night	37% 7% 18% 30% 8%	540
	21st to end	Night	33% 12% 15% 28% 11% 1	540
July	1st to 10th	Night	38% 10% 16% 30% 7%	661
	11th to 20th	Night	40% 11% 16% 30% 4	767
	21st to end	Night	32% 11% 22% 33% 3	966
August	1st to 10th	Night	30% 11% 22% 29% 7%	1107
	11th to 20th	Night	47% 12% 19% 16% 5% 1	1246
	21st to end	Night	45% 11% 21% 22%	1659
September	1st to 10th	Night	41% 11% 27% 19% 2	1620
	11th to 20th	Night	47% 10% 20% 19% 3	1879
	21st to end	Night	56% 9% 19% 15% 2	1980
October	1st to 10th	Night	58% 9% 19% 13% 1	2227
	11th to 20th	Night	64% 8% 16% 11% 1	2340
	21st to end	Night	72% 7% 11% 9%	2860
November	1st to 10th	Night	74% 6% 9% 9% 2	2804
	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 22% 33% 23% 13%	471
April	1st to 10th	Day	8% 5% 28% 29% 18% 11%	420
	11th to 20th	Day	7% 4 13% 33% 31% 12%	415
	21st to end	Day	8% 4 23% 35% 25% 6%	600
May	1st to 10th	Day	12% 7% 25% 30% 21% 5%	652
	11th to 20th	Day	7% 5% 23% 32% 24% 7%	802
	21st to end	Day	10% 5% 21% 34% 25% 6%	874
June	1st to 10th	Day	14% 4 20% 29% 25% 8%	810
	11th to 20th	Day	14% 2 21% 30% 24% 9%	810
	21st to end	Day	9% 4 16% 28% 29% 14%	810
July	1st to 10th	Day	9% 4 16% 30% 29% 11%	796
	11th to 20th	Day	10% 3 15% 27% 29% 16%	792
	21st to end	Day	9% 3 13% 26% 31% 18%	881
August	1st to 10th	Day	9% 3 12% 26% 32% 18%	766
	11th to 20th	Day	18% 4 16% 26% 26% 9%	612
	21st to end	Day	12% 4 14% 27% 29% 14%	495
September	1st to 10th	Day	16% 4 19% 29% 19% 13%	450
	11th to 20th	Day	18% 6% 18% 26% 19% 12%	450
	21st to end	Day	17% 6% 26% 32% 15% 4	450
October	1st to 10th	Day	18% 8% 24% 25% 17% 8%	308
	11th to 20th	Day	20% 9% 21% 28% 15% 7%	270
	21st to end	Day	15% 4 23% 34% 20% 4	247
November	1st to 10th	Day	11% 4 24% 29% 23% 8%	180
	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% 41% 27% 4	800
April	1st to 10th	Night	7% 5% 24% 36% 21% 6%	567
	11th to 20th	Night	9% 2 19% 39% 28% 3	459
	21st to end	Night	5% 2 25% 45% 22% 1	360
May	1st to 10th	Night	9% 8% 27% 37% 19% 2	360
	11th to 20th	Night	9% 5% 27% 37% 19% 3	354
	21st to end	Night	10% 5% 21% 40% 24% 1	389
June	1st to 10th	Night	14% 3 19% 38% 24% 2	270
	11th to 20th	Night	13% 4 16% 36% 31% 1	180
	21st to end	Night	8% 2 16% 36% 37% 2	180
July	1st to 10th	Night	7% 3 14% 36% 35% 4	311
	11th to 20th	Night	11% 2 12% 38% 31% 5%	348
	21st to end	Night	7% 3 13% 30% 40% 7%	394
August	1st to 10th	Night	10% 1 10% 33% 38% 8%	358
	11th to 20th	Night	19% 2 12% 35% 26% 6%	356
	21st to end	Night	17% 3 13% 29% 33% 5%	471
September	1st to 10th	Night	13% 4 17% 32% 29% 5%	540
	11th to 20th	Night	14% 4 21% 32% 23% 5%	692
	21st to end	Night	23% 4 26% 29% 15% 4	720
October	1st to 10th	Night	20% 4 22% 34% 16% 4	720
	11th to 20th	Night	21% 5% 22% 30% 18% 4	720
	21st to end	Night	18% 6% 23% 28% 21% 4	980
November	1st to 10th	Night	18% 5% 20% 30% 22% 6%	925
	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 2024-03-19 21:31:05. Version ac07

Copyright © 2024 Attilla Danko.