Cambridge Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cambridge Bay clear sky chart from 2005-11-05 to 2024-10-14.

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% 10% 5% 11% 7% 6% 6% 5% 7% 9% 26%	107883
	Night	5% 9% 4 12% 9% 9% 9% 7% 10% 10% 17%	96284
Transparency	Day	53% 8% 16% 19% 4	107444
	Night	55% 9% 14% 17% 5%	96348
Seeing	Day	13% 2 12% 28% 30% 15%	18963
	Night	9% 2 12% 29% 33% 14%	23128

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	11th to 20th	Day	2 4 1 12% 10% 10% 11% 13% 11% 11% 17%	141
	21st to end	Day	2 7% 3 6% 7% 6% 5% 10% 9% 14% 32%	1007
February	1st to 10th	Day	2 3 2 9% 8% 11% 11% 12% 13% 14% 16%	911
	11th to 20th	Day	2 4 3 9% 7% 7% 9% 9% 10% 16% 24%	1195
	21st to end	Day	1 5% 3 11% 9% 9% 10% 11% 11% 12% 18%	1218
March	1st to 10th	Day	1 5% 3 8% 10% 9% 10% 9% 13% 18% 14%	2881
	11th to 20th	Day	1 7% 3 9% 6% 8% 11% 9% 16% 12% 17%	3255
	21st to end	Day	2 4 2 8% 8% 8% 10% 13% 13% 13% 20%	4152
April	1st to 10th	Day	4 9% 4 9% 9% 7% 11% 9% 11% 9% 18%	2561
	11th to 20th	Day	4 8% 3 11% 9% 12% 11% 7% 8% 9% 18%	2751
	21st to end	Day	4 10% 6% 14% 11% 12% 10% 6% 6% 7% 15%	3059
May	1st to 10th	Day	8% 11% 6% 14% 9% 7% 6% 5% 7% 7% 21%	5692
	11th to 20th	Day	5% 15% 10% 15% 9% 8% 6% 4 6% 8% 14%	6274
	21st to end	Day	4 9% 6% 15% 7% 5% 5% 4 7% 9% 29%	8121
June	1st to 10th	Day	11% 15% 6% 12% 6% 5% 5% 4 6% 7% 24%	4560
	11th to 20th	Day	14% 18% 6% 9% 6% 4 4 3 5% 7% 23%	4560
	21st to end	Day	8% 11% 3 7% 6% 4 5% 4 7% 9% 38%	4560
July	1st to 10th	Day	10% 9% 4 10% 7% 6% 6% 5% 7% 8% 29%	7600
	11th to 20th	Day	9% 7% 3 7% 5% 4 5% 4 7% 9% 39%	7558
	21st to end	Day	18% 8% 3 7% 5% 4 5% 4 5% 9% 33%	7020
August	1st to 10th	Day	7% 6% 3 7% 4 4 5% 4 5% 9% 48%	5717
	11th to 20th	Day	8% 7% 2 6% 4 4 6% 4 6% 9% 44%	5061
	21st to end	Day	13% 12% 4 9% 5% 5% 5% 4 6% 8% 29%	5176
September	1st to 10th	Day	18% 16% 6% 10% 5% 5% 5% 4 6% 6% 20%	2597
	11th to 20th	Day	16% 23% 8% 15% 5% 5% 4 2 4 3 15%	2280
	21st to end	Day	18% 22% 9% 18% 7% 3 3 3 3 4 10%	2018
October	1st to 10th	Day	15% 20% 9% 22% 9% 5% 3 3 3 3 8%	1786
	11th to 20th	Day	17% 20% 9% 20% 10% 7% 4 3 2 2 6%	1425
	21st to end	Day	12% 15% 6% 15% 11% 10% 7% 5% 4 4 11%	1264
November	1st to 10th	Day	4 15% 6% 13% 12% 11% 11% 6% 7% 6% 9%	859
	11th to 20th	Day	2 11% 6% 20% 12% 10% 7% 9% 10% 6% 7%	531
	21st to end	Day	2 10% 9% 18% 12% 12% 8% 5% 15% 2 8%	93
January	1st to 10th	Night	2 4 2 7% 11% 15% 15% 10% 12% 10% 12%	7585
	11th to 20th	Night	1 7% 3 10% 8% 7% 9% 7% 13% 16% 20%	7024
	21st to end	Night	1 5% 2 6% 7% 7% 11% 9% 13% 14% 25%	6654
February	1st to 10th	Night	1 5% 3 8% 10% 10% 12% 10% 14% 13% 14%	3268
	11th to 20th	Night	1 5% 3 9% 7% 10% 8% 9% 12% 15% 21%	2869
	21st to end	Night	4 3 11% 10% 9% 10% 9% 11% 13% 19%	2236
March	1st to 10th	Night	1 5% 3 8% 8% 8% 11% 9% 13% 17% 17%	4011
	11th to 20th	Night	1 7% 4 10% 7% 7% 10% 10% 13% 12% 19%	3714
	21st to end	Night	1 5% 3 10% 7% 7% 10% 11% 11% 11% 24%	3490
April	1st to 10th	Night	4 7% 4 10% 9% 6% 9% 7% 9% 9% 25%	1617
	11th to 20th	Night	5% 7% 2 9% 6% 9% 9% 7% 8% 10% 30%	1377
	21st to end	Night	4 10% 3 12% 11% 12% 11% 6% 5% 6% 19%	1121
May	1st to 10th	Night	8% 9% 7% 17% 9% 7% 6% 4 4 7% 21%	1266
	11th to 20th	Night	6% 14% 7% 15% 9% 10% 4 4 8% 5% 19%	628
July	21st to end	Night	22% 10% 2 8% 5% 5% 4 3 6% 6% 28%	539
	August	1st to 10th	Night	7% 5% 2 6% 5% 5% 5% 6% 6% 8% 46%	1213
11th to 20th		Night	9% 7% 4 7% 4 4 4 4 6% 9% 40%	1764
21st to end		Night	16% 11% 3 7% 5% 4 4 3 6% 8% 33%	2483
September	1st to 10th	Night	15% 18% 7% 10% 5% 5% 5% 4 6% 7% 18%	1583
	11th to 20th	Night	14% 24% 10% 15% 4 4 4 3 3 4 16%	1900
	21st to end	Night	19% 19% 9% 22% 6% 3 3 2 3 3 9%	2161
October	1st to 10th	Night	14% 20% 8% 21% 9% 4 4 2 3 3 10%	2375
	11th to 20th	Night	16% 22% 7% 19% 10% 8% 5% 2 3 2 6%	2611
	21st to end	Night	13% 16% 7% 17% 9% 8% 6% 3 4 5% 12%	3091
November	1st to 10th	Night	5% 11% 5% 15% 10% 10% 10% 7% 9% 8% 10%	3218
	11th to 20th	Night	2 11% 6% 18% 12% 10% 9% 8% 8% 7% 10%	3647
	21st to end	Night	2 12% 6% 16% 12% 10% 10% 8% 9% 7% 9%	4244
December	1st to 10th	Night	2 7% 3 12% 11% 11% 10% 8% 10% 12% 13%	4560
	11th to 20th	Night	3 6% 3 11% 10% 11% 12% 9% 11% 13% 12%	5675
	21st to end	Night	4 8% 5% 15% 11% 10% 8% 7% 11% 9% 10%	8360

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	11th to 20th	Day	48% 8% 23% 18% 3	141
	21st to end	Day	34% 6% 12% 30% 18%	1007
February	1st to 10th	Day	44% 12% 14% 24% 6%	911
	11th to 20th	Day	41% 8% 19% 28% 4	1201
	21st to end	Day	47% 9% 16% 20% 8%	1218
March	1st to 10th	Day	46% 7% 13% 24% 10%	2881
	11th to 20th	Day	45% 7% 14% 19% 15%	3256
	21st to end	Day	44% 7% 16% 20% 14%	4152
April	1st to 10th	Day	53% 10% 13% 16% 8%	2561
	11th to 20th	Day	57% 10% 11% 18% 5%	2751
	21st to end	Day	67% 8% 7% 14% 4	3059
May	1st to 10th	Day	57% 13% 13% 14% 3	5692
	11th to 20th	Day	66% 9% 10% 14% 2	6278
	21st to end	Day	49% 9% 11% 27% 4	8122
June	1st to 10th	Day	60% 8% 13% 16% 3	4560
	11th to 20th	Day	60% 8% 15% 15% 2	4560
	21st to end	Day	42% 10% 23% 23% 3	4560
July	1st to 10th	Day	50% 8% 14% 25% 3	7481
	11th to 20th	Day	41% 6% 21% 26% 5%	7423
	21st to end	Day	49% 7% 26% 17% 2	6796
August	1st to 10th	Day	35% 6% 26% 21% 12%	5695
	11th to 20th	Day	37% 9% 26% 26% 3	5111
	21st to end	Day	53% 7% 21% 18%	5175
September	1st to 10th	Day	65% 9% 19% 7% 1	2597
	11th to 20th	Day	74% 8% 11% 8%	2280
	21st to end	Day	79% 7% 9% 5% 1	2018
October	1st to 10th	Day	81% 6% 7% 5%	1786
	11th to 20th	Day	83% 6% 5% 5% 1	1425
	21st to end	Day	73% 9% 10% 7% 1	1264
November	1st to 10th	Day	70% 10% 9% 9% 1	859
	11th to 20th	Day	67% 12% 10% 9% 2	531
	21st to end	Day	72% 12% 4 12%	93
January	1st to 10th	Night	55% 10% 16% 16% 2	7585
	11th to 20th	Night	44% 7% 18% 28% 3	7086
	21st to end	Night	38% 6% 13% 26% 16%	6654
February	1st to 10th	Night	46% 13% 17% 20% 4	3268
	11th to 20th	Night	42% 9% 17% 27% 4	2873
	21st to end	Night	45% 9% 14% 25% 7%	2236
March	1st to 10th	Night	43% 7% 11% 31% 7%	4011
	11th to 20th	Night	46% 8% 12% 18% 16% 1	3714
	21st to end	Night	43% 7% 15% 23% 12%	3490
April	1st to 10th	Night	46% 8% 16% 21% 9%	1617
	11th to 20th	Night	44% 9% 13% 25% 8% 1	1377
	21st to end	Night	62% 8% 9% 17% 3	1121
May	1st to 10th	Night	62% 9% 11% 14% 4	1266
	11th to 20th	Night	61% 11% 12% 13% 3	628
July	21st to end	Night	57% 6% 16% 19% 2	524
	August	1st to 10th	Night	34% 7% 27% 19% 12%	1210
11th to 20th		Night	42% 7% 18% 29% 5%	1780
21st to end		Night	48% 7% 24% 20% 1	2483
September	1st to 10th	Night	64% 10% 18% 8%	1583
	11th to 20th	Night	72% 7% 12% 8%	1900
	21st to end	Night	81% 7% 7% 5%	2161
October	1st to 10th	Night	79% 8% 8% 5% 1	2375
	11th to 20th	Night	83% 7% 6% 4 1	2611
	21st to end	Night	75% 8% 7% 9% 1	3091
November	1st to 10th	Night	64% 13% 15% 8% 1	3218
	11th to 20th	Night	66% 11% 11% 10% 2	3647
	21st to end	Night	66% 11% 11% 11% 1	4244
December	1st to 10th	Night	56% 11% 13% 15% 4	4560
	11th to 20th	Night	54% 10% 18% 16% 2	5675
	21st to end	Night	61% 8% 12% 14% 5%	8360

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	11th to 20th	Day	8% 58% 25% 8%	12
	21st to end	Day	2 10% 47% 31% 9%	99
February	1st to 10th	Day	1 1 10% 23% 36% 30%	153
	11th to 20th	Day	2 1 10% 32% 32% 23%	180
	21st to end	Day	1 6% 30% 40% 23%	207
March	1st to 10th	Day	1 1 12% 28% 39% 19%	270
	11th to 20th	Day	3 3 10% 32% 35% 18%	317
	21st to end	Day	3 8% 29% 40% 20%	506
April	1st to 10th	Day	6% 1 15% 27% 32% 21%	589
	11th to 20th	Day	4 2 11% 26% 33% 24%	640
	21st to end	Day	5% 1 12% 28% 36% 18%	650
May	1st to 10th	Day	10% 2 13% 25% 30% 20%	835
	11th to 20th	Day	8% 1 12% 30% 36% 13%	1042
	21st to end	Day	9% 1 10% 28% 34% 17%	1301
June	1st to 10th	Day	15% 2 14% 29% 26% 14%	1250
	11th to 20th	Day	20% 3 14% 30% 25% 9%	1250
	21st to end	Day	12% 2 11% 31% 33% 11%	1250
July	1st to 10th	Day	11% 1 11% 29% 32% 16%	1226
	11th to 20th	Day	16% 1 14% 28% 30% 11%	1212
	21st to end	Day	16% 2 14% 29% 27% 11%	1139
August	1st to 10th	Day	14% 2 12% 24% 32% 16%	865
	11th to 20th	Day	16% 4 14% 21% 32% 14%	720
	21st to end	Day	20% 3 13% 24% 26% 15%	748
September	1st to 10th	Day	24% 4 11% 22% 24% 15%	655
	11th to 20th	Day	29% 4 14% 23% 21% 9%	490
	21st to end	Day	23% 5% 17% 24% 21% 10%	329
October	1st to 10th	Day	15% 7% 20% 26% 20% 12%	300
	11th to 20th	Day	19% 4 14% 28% 24% 11%	279
	21st to end	Day	11% 6% 15% 28% 27% 12%	235
November	1st to 10th	Day	4 2 9% 22% 37% 26%	90
	11th to 20th	Day	2 12% 28% 44% 13%	90
	21st to end	Day	6% 6% 50% 32% 6%	34
January	1st to 10th	Night	3 1 10% 28% 39% 18%	1220
	11th to 20th	Night	3 1 15% 37% 31% 13%	1168
	21st to end	Night	3 1 12% 38% 35% 11%	1178
February	1st to 10th	Night	2 1 11% 28% 35% 22%	1031
	11th to 20th	Night	3 1 11% 34% 35% 16%	929
	21st to end	Night	1 10% 32% 38% 19%	785
March	1st to 10th	Night	3 1 10% 29% 40% 16%	801
	11th to 20th	Night	4 1 10% 29% 36% 20%	760
	21st to end	Night	3 1 10% 32% 40% 14%	640
April	1st to 10th	Night	6% 1 11% 33% 37% 12%	570
	11th to 20th	Night	7% 2 12% 31% 36% 13%	503
	21st to end	Night	7% 2 9% 30% 35% 17%	361
May	1st to 10th	Night	8% 2 8% 32% 33% 17%	190
	11th to 20th	Night	8% 1 16% 27% 41% 7%	182
July	21st to end	Night	16% 4 14% 36% 26% 4	140
	August	1st to 10th	Night	14% 1 11% 30% 38% 7%	189
11th to 20th		Night	16% 3 17% 24% 33% 7%	364
21st to end		Night	25% 4 10% 26% 28% 8%	518
September	1st to 10th	Night	22% 4 14% 26% 26% 9%	570
	11th to 20th	Night	24% 3 13% 26% 25% 8%	570
	21st to end	Night	28% 4 14% 24% 23% 7%	670
October	1st to 10th	Night	24% 4 18% 26% 20% 9%	855
	11th to 20th	Night	25% 5% 14% 25% 23% 8%	918
	21st to end	Night	20% 3 14% 25% 28% 10%	990
November	1st to 10th	Night	9% 2 12% 24% 36% 16%	958
	11th to 20th	Night	6% 2 16% 31% 32% 13%	1118
	21st to end	Night	6% 2 11% 30% 31% 20%	1168
December	1st to 10th	Night	4 1 13% 31% 35% 16%	1220
	11th to 20th	Night	5% 1 12% 27% 36% 18%	1220
	21st to end	Night	4 1 10% 27% 39% 20%	1342

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