Cambridge Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cambridge Bay clear sky chart from 2005-11-06 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	9% 10% 5% 10% 9% 5% 7% 6% 7% 8% 24%	76502
	Night	5% 8% 5% 10% 11% 7% 10% 9% 9% 10% 16%	87112
Transparency	Day	56% 9% 15% 17% 3	76013
	Night	56% 9% 14% 16% 4	87160
Seeing	Day	13% 2 12% 27% 31% 15%	17645
	Night	9% 2 12% 29% 33% 15%	22597

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 9% 13% 5% 12% 16% 11% 11% 17%	141
	21st to end	Day	2 7% 2 5% 8% 4 6% 10% 9% 14% 32%	1007
February	1st to 10th	Day	2 3 2 8% 10% 8% 11% 14% 13% 14% 16%	905
	11th to 20th	Day	2 4 3 7% 7% 5% 8% 11% 10% 17% 25%	1131
	21st to end	Day	2 3 3 9% 12% 7% 11% 12% 9% 14% 19%	1148
March	1st to 10th	Day	2 4 4 7% 13% 8% 10% 11% 9% 12% 19%	1650
	11th to 20th	Day	3 6% 3 7% 7% 6% 11% 11% 11% 15% 19%	1843
	21st to end	Day	4 5% 4 9% 11% 7% 10% 11% 10% 12% 18%	2363
April	1st to 10th	Day	4 8% 4 7% 10% 5% 11% 12% 11% 9% 18%	2426
	11th to 20th	Day	5% 6% 4 10% 11% 9% 12% 10% 8% 9% 17%	2603
	21st to end	Day	5% 9% 6% 12% 12% 8% 12% 8% 6% 7% 15%	2898
May	1st to 10th	Day	6% 10% 5% 10% 13% 6% 8% 6% 6% 7% 23%	3232
	11th to 20th	Day	5% 9% 8% 17% 13% 6% 8% 6% 5% 7% 16%	3521
	21st to end	Day	6% 11% 8% 16% 10% 4 5% 5% 7% 7% 21%	4567
June	1st to 10th	Day	11% 14% 7% 11% 7% 4 6% 5% 5% 7% 24%	4320
	11th to 20th	Day	16% 15% 6% 8% 7% 3 5% 4 6% 7% 24%	4320
	21st to end	Day	9% 10% 3 6% 6% 3 5% 5% 6% 9% 40%	4320
July	1st to 10th	Day	8% 6% 3 6% 6% 4 6% 5% 6% 9% 39%	4320
	11th to 20th	Day	13% 8% 4 7% 7% 4 5% 5% 7% 9% 33%	4305
	21st to end	Day	13% 7% 3 6% 7% 3 5% 6% 7% 10% 32%	4010
August	1st to 10th	Day	11% 9% 3 7% 6% 3 5% 5% 6% 10% 36%	3251
	11th to 20th	Day	13% 9% 4 7% 7% 4 7% 7% 7% 8% 26%	2893
	21st to end	Day	15% 13% 5% 8% 7% 4 6% 5% 6% 8% 26%	2954
September	1st to 10th	Day	18% 15% 7% 9% 7% 4 5% 5% 6% 6% 20%	2461
	11th to 20th	Day	16% 21% 8% 14% 6% 4 4 3 4 4 15%	2160
	21st to end	Day	18% 19% 11% 17% 8% 3 3 4 3 4 11%	1913
October	1st to 10th	Day	15% 18% 10% 20% 11% 5% 3 3 3 3 9%	1692
	11th to 20th	Day	18% 19% 9% 17% 13% 6% 5% 4 2 2 6%	1401
	21st to end	Day	12% 15% 6% 12% 14% 8% 7% 7% 3 4 11%	1264
November	1st to 10th	Day	4 13% 7% 12% 14% 7% 13% 8% 7% 6% 9%	859
	11th to 20th	Day	2 9% 7% 16% 15% 9% 7% 10% 10% 6% 7%	531
	21st to end	Day	2 9% 8% 18% 13% 11% 9% 6% 15% 2 8%	93
January	1st to 10th	Night	2 3 2 6% 12% 11% 17% 13% 12% 10% 12%	7585
	11th to 20th	Night	1 7% 3 8% 9% 5% 9% 9% 13% 16% 20%	7024
	21st to end	Night	1 4 3 5% 7% 5% 10% 12% 13% 15% 25%	6654
February	1st to 10th	Night	1 4 3 7% 11% 7% 12% 12% 14% 14% 14%	3259
	11th to 20th	Night	1 4 3 8% 8% 8% 9% 11% 12% 16% 20%	2713
	21st to end	Night	1 3 4 10% 11% 7% 9% 12% 11% 13% 19%	2108
March	1st to 10th	Night	2 5% 3 8% 11% 7% 13% 11% 11% 9% 20%	2326
	11th to 20th	Night	2 5% 3 8% 9% 6% 12% 12% 9% 13% 22%	2113
	21st to end	Night	2 5% 5% 8% 9% 6% 10% 11% 10% 11% 23%	1993
April	1st to 10th	Night	4 6% 5% 9% 9% 5% 7% 10% 10% 9% 27%	1533
	11th to 20th	Night	5% 6% 2 7% 7% 6% 11% 8% 8% 10% 30%	1305
	21st to end	Night	5% 9% 4 11% 11% 9% 11% 8% 5% 7% 20%	1062
May	1st to 10th	Night	5% 10% 6% 11% 11% 6% 8% 4 3 7% 30%	726
	11th to 20th	Night	6% 8% 6% 13% 14% 7% 5% 6% 8% 5% 22%	371
July	21st to end	Night	12% 12% 2 7% 8% 7% 4 4 6% 7% 32%	304
	August	1st to 10th	Night	12% 7% 2 6% 7% 5% 5% 9% 7% 8% 32%	688
11th to 20th		Night	15% 10% 5% 10% 7% 3 5% 6% 6% 9% 24%	1004
21st to end		Night	18% 14% 4 8% 6% 3 5% 4 6% 8% 26%	1399
September	1st to 10th	Night	16% 17% 7% 9% 6% 3 5% 5% 6% 7% 18%	1498
	11th to 20th	Night	13% 23% 10% 14% 6% 3 3 4 3 4 16%	1800
	21st to end	Night	19% 18% 10% 21% 8% 3 3 3 3 3 10%	2046
October	1st to 10th	Night	14% 19% 9% 19% 11% 4 4 4 3 3 10%	2250
	11th to 20th	Night	16% 21% 8% 16% 12% 6% 6% 3 3 2 6%	2556
	21st to end	Night	14% 15% 7% 15% 12% 6% 6% 5% 4 5% 12%	3091
November	1st to 10th	Night	6% 10% 5% 12% 12% 7% 11% 10% 9% 8% 10%	3218
	11th to 20th	Night	3 11% 6% 16% 13% 8% 10% 10% 7% 7% 10%	3647
	21st to end	Night	2 10% 7% 14% 13% 8% 10% 10% 8% 8% 9%	4244
December	1st to 10th	Night	2 6% 4 10% 13% 9% 11% 10% 10% 12% 13%	4560
	11th to 20th	Night	3 6% 3 9% 12% 8% 12% 12% 11% 13% 12%	5675
	21st to end	Night	4 7% 5% 13% 13% 7% 10% 9% 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	45% 12% 14% 24% 6%	905
	11th to 20th	Day	41% 9% 19% 28% 3	1137
	21st to end	Day	48% 10% 15% 20% 7%	1148
March	1st to 10th	Day	50% 9% 17% 16% 9%	1650
	11th to 20th	Day	46% 8% 17% 22% 7%	1844
	21st to end	Day	52% 8% 13% 20% 7%	2363
April	1st to 10th	Day	53% 10% 14% 16% 8%	2426
	11th to 20th	Day	58% 10% 10% 18% 4	2603
	21st to end	Day	67% 8% 7% 14% 3	2898
May	1st to 10th	Day	59% 9% 9% 18% 6%	3232
	11th to 20th	Day	67% 9% 9% 13% 2	3525
	21st to end	Day	62% 8% 10% 17% 3	4568
June	1st to 10th	Day	60% 8% 13% 16% 3	4320
	11th to 20th	Day	59% 8% 16% 15% 3	4320
	21st to end	Day	41% 10% 23% 24% 3	4320
July	1st to 10th	Day	40% 10% 17% 29% 4	4201
	11th to 20th	Day	48% 10% 18% 23% 1	4170
	21st to end	Day	45% 11% 24% 18% 1	3785
August	1st to 10th	Day	45% 9% 24% 20% 2	3229
	11th to 20th	Day	53% 13% 23% 12%	2893
	21st to end	Day	56% 11% 21% 12%	2954
September	1st to 10th	Day	65% 9% 19% 7% 1	2461
	11th to 20th	Day	73% 8% 11% 8%	2160
	21st to end	Day	78% 7% 9% 5% 1	1913
October	1st to 10th	Day	81% 6% 8% 5%	1692
	11th to 20th	Day	84% 6% 5% 4 1	1401
	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	47% 12% 17% 20% 4	3259
	11th to 20th	Night	43% 10% 17% 27% 4	2717
	21st to end	Night	46% 9% 14% 25% 6%	2108
March	1st to 10th	Night	49% 10% 14% 19% 8%	2326
	11th to 20th	Night	47% 9% 15% 19% 9%	2113
	21st to end	Night	47% 9% 14% 23% 8%	1993
April	1st to 10th	Night	45% 9% 16% 21% 9%	1533
	11th to 20th	Night	44% 9% 14% 25% 8% 1	1305
	21st to end	Night	61% 8% 9% 18% 3	1062
May	1st to 10th	Night	56% 6% 10% 21% 7%	726
	11th to 20th	Night	60% 9% 13% 13% 4	371
July	21st to end	Night	52% 9% 18% 21% 1	289
	August	1st to 10th	Night	46% 12% 22% 18% 2	685
11th to 20th		Night	56% 11% 22% 11% 1	1004
21st to end		Night	56% 10% 23% 10% 1	1399
September	1st to 10th	Night	64% 10% 17% 9%	1498
	11th to 20th	Night	72% 8% 13% 7%	1800
	21st to end	Night	81% 7% 7% 5%	2046
October	1st to 10th	Night	79% 8% 8% 4 1	2250
	11th to 20th	Night	83% 7% 5% 3 1	2556
	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%	151
	11th to 20th	Day	3 10% 30% 33% 25%	160
	21st to end	Day	2 6% 29% 40% 24%	182
March	1st to 10th	Day	1 1 12% 29% 39% 18%	240
	11th to 20th	Day	3 1 9% 30% 37% 20%	284
	21st to end	Day	3 8% 30% 39% 19%	462
April	1st to 10th	Day	6% 15% 26% 31% 22%	542
	11th to 20th	Day	4 2 10% 27% 33% 25%	590
	21st to end	Day	5% 1 12% 27% 35% 20%	600
May	1st to 10th	Day	9% 2 14% 24% 30% 21%	775
	11th to 20th	Day	8% 1 12% 30% 37% 13%	972
	21st to end	Day	10% 1 10% 29% 34% 16%	1215
June	1st to 10th	Day	15% 2 14% 28% 26% 15%	1170
	11th to 20th	Day	21% 3 14% 30% 24% 9%	1170
	21st to end	Day	12% 2 11% 31% 34% 12%	1170
July	1st to 10th	Day	10% 1 11% 28% 33% 17%	1146
	11th to 20th	Day	16% 1 14% 28% 30% 11%	1133
	21st to end	Day	16% 2 14% 29% 28% 12%	1063
August	1st to 10th	Day	15% 2 12% 23% 31% 16%	805
	11th to 20th	Day	17% 4 13% 20% 32% 14%	667
	21st to end	Day	19% 2 13% 24% 27% 15%	693
September	1st to 10th	Day	23% 4 11% 22% 24% 15%	607
	11th to 20th	Day	27% 4 15% 23% 22% 9%	450
	21st to end	Day	20% 5% 16% 24% 23% 11%	298
October	1st to 10th	Day	14% 7% 19% 26% 21% 13%	270
	11th to 20th	Day	20% 4 13% 28% 24% 12%	270
	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%	1029
	11th to 20th	Night	3 11% 32% 37% 17%	879
	21st to end	Night	1 10% 31% 38% 19%	740
March	1st to 10th	Night	3 1 10% 30% 40% 16%	759
	11th to 20th	Night	4 1 10% 28% 37% 21%	720
	21st to end	Night	3 1 10% 32% 40% 14%	607
April	1st to 10th	Night	6% 1 9% 34% 37% 13%	540
	11th to 20th	Night	7% 2 11% 31% 36% 13%	477
	21st to end	Night	8% 1 8% 28% 36% 18%	342
May	1st to 10th	Night	8% 2 8% 31% 33% 18%	180
	11th to 20th	Night	8% 1 16% 27% 42% 6%	173
July	21st to end	Night	14% 5% 12% 37% 28% 4	132
	August	1st to 10th	Night	15% 1 11% 31% 36% 7%	179
11th to 20th		Night	17% 3 17% 24% 33% 7%	344
21st to end		Night	25% 4 10% 25% 29% 8%	490
September	1st to 10th	Night	22% 4 14% 25% 25% 10%	540
	11th to 20th	Night	23% 3 14% 26% 25% 8%	540
	21st to end	Night	26% 4 14% 25% 24% 7%	634
October	1st to 10th	Night	24% 4 17% 27% 20% 9%	810
	11th to 20th	Night	25% 5% 14% 24% 23% 9%	900
	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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