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 2026-07-16.

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% 12% 7% 6% 6% 5% 7% 8% 25%	148094
	Night	4 8% 4 12% 9% 9% 9% 7% 10% 11% 16%	141663
Transparency	Day	54% 7% 15% 19% 5%	147596
	Night	55% 7% 15% 19% 5%	141723
Seeing	Day	12% 2 13% 28% 30% 15%	21347
	Night	9% 2 13% 30% 33% 14%	25584

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	1 2 7% 7% 11% 10% 10% 9% 15% 30%	301
	21st to end	Day	1 5% 2 5% 6% 7% 9% 11% 14% 14% 26%	1871
February	1st to 10th	Day	1 4 2 9% 8% 11% 12% 11% 12% 13% 16%	1007
	11th to 20th	Day	1 4 3 8% 7% 7% 9% 8% 10% 16% 26%	1325
	21st to end	Day	1 4 2 10% 9% 9% 10% 11% 11% 14% 20%	1343
March	1st to 10th	Day	1 3 2 9% 11% 11% 12% 10% 13% 16% 10%	4238
	11th to 20th	Day	1 5% 4 15% 8% 8% 9% 8% 14% 12% 16%	4770
	21st to end	Day	1 3 2 6% 6% 7% 11% 16% 18% 13% 16%	6087
April	1st to 10th	Day	4 9% 4 9% 9% 8% 11% 9% 11% 8% 18%	2831
	11th to 20th	Day	4 8% 3 11% 9% 11% 11% 7% 8% 9% 18%	3045
	21st to end	Day	4 9% 5% 14% 11% 13% 10% 6% 7% 6% 15%	3381
May	1st to 10th	Day	5% 9% 5% 16% 11% 8% 7% 6% 7% 6% 19%	10579
	11th to 20th	Day	4 13% 9% 23% 9% 7% 6% 4 5% 6% 14%	11697
	21st to end	Day	9% 16% 7% 16% 7% 5% 4 3 5% 7% 20%	15171
June	1st to 10th	Day	11% 15% 6% 12% 6% 5% 5% 4 6% 7% 24%	5040
	11th to 20th	Day	13% 18% 6% 9% 6% 4 4 3 5% 7% 24%	5040
	21st to end	Day	8% 10% 3 7% 6% 4 5% 4 7% 8% 39%	5040
July	1st to 10th	Day	8% 7% 3 9% 7% 6% 6% 5% 6% 9% 35%	11120
	11th to 20th	Day	10% 7% 3 8% 5% 5% 6% 4 7% 8% 37%	10932
	21st to end	Day	15% 7% 3 7% 5% 4 5% 4 6% 9% 36%	10080
August	1st to 10th	Day	7% 6% 3 7% 4 4 5% 4 5% 9% 47%	5898
	11th to 20th	Day	8% 7% 2 5% 4 4 5% 4 6% 9% 44%	5224
	21st to end	Day	12% 12% 4 9% 6% 5% 5% 4 6% 8% 28%	5339
September	1st to 10th	Day	17% 17% 6% 11% 6% 5% 5% 4 5% 5% 20%	2733
	11th to 20th	Day	16% 22% 8% 15% 5% 5% 4 2 4 4 14%	2400
	21st to end	Day	18% 22% 9% 17% 7% 3 3 3 3 4 10%	2123
October	1st to 10th	Day	15% 24% 10% 20% 9% 5% 3 2 3 2 7%	3072
	11th to 20th	Day	14% 20% 9% 18% 9% 6% 4 3 3 3 12%	2522
	21st to end	Day	7% 14% 8% 22% 11% 9% 6% 4 4 4 10%	2247
November	1st to 10th	Day	5% 15% 7% 12% 12% 11% 10% 6% 7% 6% 10%	951
	11th to 20th	Day	2 11% 7% 21% 11% 11% 7% 9% 9% 6% 7%	585
	21st to end	Day	2 10% 9% 18% 11% 11% 7% 6% 16% 2 10%	102
January	1st to 10th	Night	2 4 2 9% 9% 11% 13% 10% 13% 14% 14%	14089
	11th to 20th	Night	1 7% 4 10% 7% 6% 7% 7% 12% 17% 22%	13100
	21st to end	Night	1 4 2 7% 7% 7% 10% 9% 15% 15% 23%	12307
February	1st to 10th	Night	1 5% 3 8% 10% 10% 12% 10% 14% 13% 14%	3612
	11th to 20th	Night	1 4 2 9% 7% 10% 8% 9% 12% 14% 22%	3179
	21st to end	Night	4 3 10% 10% 8% 10% 9% 12% 15% 20%	2463
March	1st to 10th	Night	1 3 2 7% 13% 14% 12% 8% 12% 16% 12%	5899
	11th to 20th	Night	1 7% 5% 15% 8% 7% 8% 8% 12% 11% 18%	5432
	21st to end	Night	1 3 2 8% 6% 7% 11% 15% 16% 12% 18%	5108
April	1st to 10th	Night	4 7% 4 10% 9% 6% 9% 7% 9% 9% 25%	1787
	11th to 20th	Night	4 7% 2 8% 6% 8% 9% 7% 8% 10% 30%	1523
	21st to end	Night	4 10% 3 12% 11% 13% 11% 6% 5% 6% 18%	1239
May	1st to 10th	Night	5% 9% 7% 17% 13% 8% 6% 4 6% 6% 20%	2338
	11th to 20th	Night	5% 13% 7% 23% 10% 8% 4 3 6% 5% 17%	1178
July	21st to end	Night	17% 9% 3 8% 5% 5% 3 3 4 7% 36%	780
	August	1st to 10th	Night	7% 5% 2 6% 5% 5% 5% 6% 6% 9% 46%	1252
11th to 20th		Night	9% 7% 4 8% 4 4 4 4 6% 9% 41%	1821
21st to end		Night	16% 11% 3 7% 5% 4 4 3 6% 8% 33%	2562
September	1st to 10th	Night	15% 18% 7% 10% 5% 5% 5% 4 6% 7% 18%	1666
	11th to 20th	Night	14% 24% 10% 14% 4 4 4 3 3 4 16%	2000
	21st to end	Night	19% 20% 9% 22% 7% 4 3 2 3 3 9%	2275
October	1st to 10th	Night	13% 24% 8% 23% 8% 5% 3 2 2 3 8%	4085
	11th to 20th	Night	15% 22% 7% 18% 9% 7% 4 2 3 3 11%	4624
	21st to end	Night	8% 13% 7% 22% 10% 9% 7% 4 4 4 12%	5545
November	1st to 10th	Night	5% 11% 5% 14% 10% 10% 10% 7% 9% 7% 11%	3566
	11th to 20th	Night	3 12% 6% 18% 11% 10% 9% 8% 7% 7% 9%	4033
	21st to end	Night	2 11% 6% 16% 11% 10% 9% 7% 9% 7% 10%	4693
December	1st to 10th	Night	1 5% 3 9% 10% 13% 12% 10% 16% 11% 10%	8080
	11th to 20th	Night	2 4 2 14% 11% 11% 12% 10% 11% 11% 14%	9195
	21st to end	Night	4 11% 6% 18% 11% 9% 8% 7% 11% 8% 8%	12232

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	37% 4 23% 35% 1	301
	21st to end	Day	37% 5% 16% 30% 12%	1871
February	1st to 10th	Day	46% 11% 14% 23% 6%	1007
	11th to 20th	Day	40% 8% 19% 28% 6%	1331
	21st to end	Day	44% 9% 16% 23% 8%	1343
March	1st to 10th	Day	50% 6% 10% 22% 12%	4238
	11th to 20th	Day	49% 5% 11% 18% 17%	4771
	21st to end	Day	39% 8% 12% 25% 17%	6087
April	1st to 10th	Day	53% 9% 13% 16% 8%	2831
	11th to 20th	Day	56% 9% 10% 19% 6%	3045
	21st to end	Day	67% 8% 7% 14% 4	3381
May	1st to 10th	Day	59% 11% 8% 17% 6%	10576
	11th to 20th	Day	67% 8% 9% 15% 1	11701
	21st to end	Day	65% 5% 10% 17% 3	15176
June	1st to 10th	Day	59% 8% 13% 17% 3	5040
	11th to 20th	Day	58% 7% 15% 15% 4	5040
	21st to end	Day	41% 9% 24% 24% 3	5040
July	1st to 10th	Day	44% 7% 18% 29% 3	11001
	11th to 20th	Day	44% 6% 21% 25% 4	10797
	21st to end	Day	46% 6% 31% 16% 1	9796
August	1st to 10th	Day	35% 6% 26% 22% 11%	5876
	11th to 20th	Day	37% 8% 27% 25% 2	5274
	21st to end	Day	53% 7% 21% 18%	5338
September	1st to 10th	Day	66% 8% 19% 6% 1	2733
	11th to 20th	Day	74% 7% 11% 7%	2400
	21st to end	Day	79% 7% 9% 4 1	2123
October	1st to 10th	Day	81% 5% 5% 7% 2	3072
	11th to 20th	Day	76% 4 5% 12% 2	2522
	21st to end	Day	73% 7% 11% 9%	2247
November	1st to 10th	Day	69% 10% 9% 11% 2	951
	11th to 20th	Day	69% 11% 9% 9% 2	585
	21st to end	Day	69% 12% 6% 14%	102
January	1st to 10th	Night	51% 6% 11% 25% 6%	14090
	11th to 20th	Night	43% 4 21% 29% 3	13162
	21st to end	Night	39% 4 19% 27% 10%	12308
February	1st to 10th	Night	48% 12% 17% 20% 4	3612
	11th to 20th	Night	42% 9% 16% 27% 7%	3183
	21st to end	Night	43% 8% 14% 27% 7%	2463
March	1st to 10th	Night	49% 7% 9% 25% 10% 1	5899
	11th to 20th	Night	50% 6% 9% 18% 17%	5432
	21st to end	Night	42% 7% 12% 23% 17%	5108
April	1st to 10th	Night	46% 8% 15% 21% 9%	1787
	11th to 20th	Night	43% 9% 13% 27% 8%	1523
	21st to end	Night	63% 8% 8% 17% 3	1239
May	1st to 10th	Night	62% 7% 8% 18% 5%	2338
	11th to 20th	Night	64% 8% 11% 15% 1	1178
July	21st to end	Night	50% 4 26% 18% 1	759
	August	1st to 10th	Night	34% 7% 27% 19% 12%	1249
11th to 20th		Night	41% 7% 19% 28% 5%	1837
21st to end		Night	48% 7% 24% 20% 2	2562
September	1st to 10th	Night	64% 10% 18% 8%	1666
	11th to 20th	Night	72% 7% 13% 8%	2000
	21st to end	Night	81% 7% 7% 4	2275
October	1st to 10th	Night	78% 8% 6% 7% 1	4085
	11th to 20th	Night	78% 5% 8% 9% 1	4624
	21st to end	Night	73% 6% 10% 11% 1	5545
November	1st to 10th	Night	63% 12% 14% 10% 1	3566
	11th to 20th	Night	68% 10% 10% 10% 2	4033
	21st to end	Night	66% 10% 11% 13% 1	4693
December	1st to 10th	Night	54% 8% 22% 13% 3	8080
	11th to 20th	Night	54% 7% 20% 17% 2	9195
	21st to end	Night	67% 6% 12% 11% 3	12232

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	19% 56% 19% 6%	16
	21st to end	Day	2 1 10% 45% 32% 10%	121
February	1st to 10th	Day	1 2 11% 24% 36% 26%	187
	11th to 20th	Day	2 1 10% 31% 34% 22%	220
	21st to end	Day	1 9% 31% 38% 22%	252
March	1st to 10th	Day	1 1 10% 26% 43% 19%	330
	11th to 20th	Day	2 2 11% 30% 33% 22%	383
	21st to end	Day	3 7% 29% 39% 22%	594
April	1st to 10th	Day	6% 1 16% 26% 31% 21%	683
	11th to 20th	Day	4 2 11% 26% 33% 23%	740
	21st to end	Day	4 1 12% 28% 35% 20%	750
May	1st to 10th	Day	9% 2 14% 27% 30% 19%	955
	11th to 20th	Day	7% 1 12% 29% 37% 13%	1182
	21st to end	Day	12% 2 12% 27% 31% 15%	1471
June	1st to 10th	Day	15% 2 15% 30% 25% 13%	1410
	11th to 20th	Day	18% 3 15% 31% 25% 9%	1410
	21st to end	Day	11% 2 11% 31% 33% 12%	1410
July	1st to 10th	Day	10% 1 12% 30% 32% 15%	1386
	11th to 20th	Day	16% 2 14% 29% 29% 10%	1332
	21st to end	Day	16% 2 14% 29% 28% 11%	1215
August	1st to 10th	Day	14% 3 13% 25% 30% 15%	925
	11th to 20th	Day	15% 4 13% 20% 32% 16%	773
	21st to end	Day	19% 3 14% 24% 25% 15%	803
September	1st to 10th	Day	23% 4 12% 23% 23% 14%	703
	11th to 20th	Day	29% 4 17% 23% 20% 8%	530
	21st to end	Day	24% 5% 16% 23% 22% 11%	360
October	1st to 10th	Day	16% 7% 20% 27% 19% 11%	330
	11th to 20th	Day	20% 5% 18% 26% 21% 10%	330
	21st to end	Day	12% 6% 16% 28% 26% 12%	285
November	1st to 10th	Day	6% 2 9% 26% 34% 23%	110
	11th to 20th	Day	3 15% 27% 42% 14%	110
	21st to end	Day	7% 7% 46% 32% 7%	41
January	1st to 10th	Night	3 2 11% 27% 40% 17%	1380
	11th to 20th	Night	3 2 17% 38% 30% 12%	1316
	21st to end	Night	3 1 14% 37% 34% 11%	1316
February	1st to 10th	Night	2 1 12% 30% 34% 21%	1149
	11th to 20th	Night	2 1 12% 34% 36% 14%	1029
	21st to end	Night	1 12% 32% 36% 18%	865
March	1st to 10th	Night	3 1 9% 29% 42% 16%	885
	11th to 20th	Night	3 1 10% 29% 37% 20%	840
	21st to end	Night	2 1 9% 32% 41% 14%	707
April	1st to 10th	Night	6% 1 11% 33% 36% 13%	630
	11th to 20th	Night	6% 2 13% 32% 36% 12%	557
	21st to end	Night	7% 2 8% 29% 38% 16%	399
May	1st to 10th	Night	8% 1 10% 32% 32% 16%	210
	11th to 20th	Night	8% 1 15% 29% 40% 6%	202
July	21st to end	Night	17% 4 13% 36% 27% 3	148
	August	1st to 10th	Night	14% 2 11% 32% 36% 7%	199
11th to 20th		Night	16% 3 16% 24% 34% 8%	384
21st to end		Night	24% 4 11% 26% 27% 8%	546
September	1st to 10th	Night	22% 4 14% 26% 25% 9%	600
	11th to 20th	Night	24% 3 14% 27% 24% 8%	600
	21st to end	Night	27% 4 14% 23% 24% 7%	705
October	1st to 10th	Night	24% 4 18% 27% 19% 8%	900
	11th to 20th	Night	26% 6% 15% 24% 22% 8%	1000
	21st to end	Night	19% 3 14% 26% 28% 10%	1100
November	1st to 10th	Night	10% 2 12% 25% 36% 15%	1066
	11th to 20th	Night	7% 2 15% 32% 32% 13%	1256
	21st to end	Night	6% 2 12% 30% 31% 19%	1317
December	1st to 10th	Night	3 1 13% 31% 36% 16%	1380
	11th to 20th	Night	5% 1 13% 29% 35% 17%	1380
	21st to end	Night	4 1 12% 28% 37% 18%	1518

Page generated at 2026-07-13 01:14:50. Version ac07

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