Umiujaq
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Umiujaq clear sky chart from 2005-11-06 to 2026-03-18.

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	16% 14% 5% 12% 7% 7% 7% 4 5% 5% 18%	131408
	Night	12% 15% 6% 15% 9% 8% 8% 5% 5% 4 13%	130496
Transparency	Day	68% 2 9% 15% 5%	134614
	Night	73% 3 8% 12% 5%	135380
Seeing	Day	25% 7% 22% 26% 14% 5%	18426
	Night	21% 7% 22% 28% 17% 4	26591

By Month

Percentage Cloud Cover NE (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	5% 14% 7% 24% 14% 12% 9% 4 4 2 6%	3526
	11th to 20th	Day	2 13% 5% 17% 14% 19% 15% 5% 5% 2 2	3704
	21st to end	Day	2 6% 5% 16% 10% 12% 17% 9% 9% 5% 10%	4500
February	1st to 10th	Day	3 9% 4 13% 10% 14% 15% 13% 9% 4 6%	1585
	11th to 20th	Day	3 8% 4 11% 11% 14% 13% 10% 9% 5% 11%	1782
	21st to end	Day	4 9% 4 12% 9% 10% 13% 10% 12% 7% 12%	1557
March	1st to 10th	Day	3 11% 5% 16% 13% 11% 16% 10% 6% 3 5%	4522
	11th to 20th	Day	5% 11% 6% 15% 10% 11% 12% 8% 7% 4 11%	4963
	21st to end	Day	6% 11% 4 13% 10% 11% 14% 6% 4 5% 15%	5786
April	1st to 10th	Day	10% 15% 4 12% 9% 10% 9% 5% 4 5% 17%	2407
	11th to 20th	Day	9% 11% 5% 13% 10% 10% 8% 4 5% 6% 20%	2654
	21st to end	Day	10% 13% 5% 13% 10% 7% 5% 4 4 6% 21%	2800
May	1st to 10th	Day	15% 10% 3 12% 11% 6% 5% 4 5% 6% 23%	6361
	11th to 20th	Day	17% 14% 7% 19% 6% 5% 4 3 4 5% 18%	7140
	21st to end	Day	9% 11% 5% 9% 4 4 4 4 5% 8% 37%	7953
June	1st to 10th	Day	13% 12% 7% 10% 6% 5% 5% 4 5% 6% 29%	3200
	11th to 20th	Day	17% 12% 4 8% 6% 4 4 5% 6% 6% 29%	3200
	21st to end	Day	21% 11% 4 9% 6% 5% 5% 4 5% 6% 23%	3200
July	1st to 10th	Day	24% 13% 4 8% 5% 4 4 3 5% 7% 23%	7279
	11th to 20th	Day	25% 15% 4 8% 5% 5% 5% 3 5% 6% 18%	7280
	21st to end	Day	27% 19% 4 9% 5% 3 3 3 4 4 18%	7622
August	1st to 10th	Day	39% 14% 3 6% 4 4 3 2 3 4 18%	4773
	11th to 20th	Day	25% 11% 3 7% 4 3 3 3 4 7% 31%	4499
	21st to end	Day	28% 11% 3 7% 4 4 4 3 5% 7% 24%	4790
September	1st to 10th	Day	32% 16% 4 8% 4 4 5% 3 5% 5% 14%	2400
	11th to 20th	Day	29% 20% 4 10% 5% 4 4 3 2 4 16%	2400
	21st to end	Day	32% 22% 4 8% 4 4 4 3 4 4 11%	2106
October	1st to 10th	Day	28% 24% 5% 9% 5% 4 3 3 3 3 13%	2000
	11th to 20th	Day	22% 23% 6% 10% 6% 4 4 3 4 5% 14%	1887
	21st to end	Day	21% 26% 8% 12% 5% 3 3 3 3 4 12%	1807
November	1st to 10th	Day	19% 27% 8% 14% 6% 4 4 3 3 4 8%	1630
	11th to 20th	Day	17% 28% 10% 14% 6% 5% 3 2 3 3 8%	1444
	21st to end	Day	10% 23% 11% 21% 8% 5% 3 3 2 2 10%	1260
December	1st to 10th	Day	5% 12% 8% 20% 11% 8% 8% 5% 6% 6% 10%	2020
	11th to 20th	Day	9% 21% 6% 25% 14% 9% 4 3 2 2 4	2313
	21st to end	Day	11% 19% 7% 21% 12% 8% 7% 3 2 3 8%	3058
January	1st to 10th	Night	4 15% 8% 26% 14% 11% 8% 4 4 3 5%	9428
	11th to 20th	Night	3 12% 6% 19% 14% 15% 13% 7% 5% 2 3	9231
	21st to end	Night	2 7% 4 16% 12% 14% 14% 8% 9% 4 9%	9714
February	1st to 10th	Night	3 11% 4 13% 11% 14% 14% 11% 11% 3 5%	3034
	11th to 20th	Night	2 9% 4 13% 10% 13% 13% 10% 11% 5% 9%	2720
	21st to end	Night	4 9% 5% 14% 9% 10% 14% 9% 10% 5% 11%	2249
March	1st to 10th	Night	4 8% 5% 16% 12% 13% 12% 10% 7% 4 9%	5537
	11th to 20th	Night	5% 13% 7% 15% 9% 9% 10% 9% 7% 5% 12%	5134
	21st to end	Night	8% 11% 5% 12% 9% 10% 15% 6% 5% 5% 14%	5146
April	1st to 10th	Night	11% 15% 5% 11% 7% 7% 10% 4 6% 6% 18%	2000
	11th to 20th	Night	8% 12% 6% 13% 9% 9% 6% 3 4 6% 23%	1705
	21st to end	Night	10% 15% 4 11% 10% 7% 4 4 4 6% 25%	1600
May	1st to 10th	Night	15% 14% 4 12% 7% 7% 6% 4 6% 6% 19%	3577
	11th to 20th	Night	17% 14% 6% 17% 7% 4 5% 3 5% 6% 16%	2790
	21st to end	Night	10% 11% 5% 8% 4 4 5% 4 5% 5% 39%	2967
June	1st to 10th	Night	14% 14% 7% 9% 5% 3 3 3 4 7% 32%	1200
	11th to 20th	Night	18% 12% 4 8% 5% 4 4 3 5% 6% 31%	1200
	21st to end	Night	18% 13% 5% 10% 6% 6% 4 3 5% 5% 27%	1200
July	1st to 10th	Night	24% 13% 4 10% 6% 4 3 3 5% 5% 23%	2720
	11th to 20th	Night	26% 15% 5% 9% 5% 4 4 3 4 5% 20%	2720
	21st to end	Night	25% 18% 4 11% 5% 4 4 3 4 5% 19%	3257
August	1st to 10th	Night	37% 17% 3 6% 3 3 3 2 4 3 17%	2381
	11th to 20th	Night	24% 10% 3 5% 4 4 4 3 6% 8% 28%	2550
	21st to end	Night	28% 11% 3 6% 3 4 3 4 5% 7% 26%	3079
September	1st to 10th	Night	34% 17% 3 8% 4 3 3 3 3 5% 16%	1993
	11th to 20th	Night	30% 21% 4 9% 4 4 3 2 3 5% 15%	2000
	21st to end	Night	29% 23% 4 7% 4 3 3 3 4 5% 14%	2290
October	1st to 10th	Night	31% 23% 4 8% 4 4 3 3 3 4 13%	2400
	11th to 20th	Night	25% 26% 6% 10% 5% 3 3 2 4 4 14%	2512
	21st to end	Night	23% 27% 7% 11% 5% 4 3 2 3 3 11%	3030
November	1st to 10th	Night	19% 28% 8% 13% 7% 4 4 3 3 3 8%	2888
	11th to 20th	Night	16% 29% 9% 15% 7% 5% 4 2 3 3 7%	3171
	21st to end	Night	10% 24% 10% 20% 7% 5% 6% 3 3 3 9%	3360
December	1st to 10th	Night	5% 13% 7% 21% 11% 7% 6% 5% 7% 6% 13%	5400
	11th to 20th	Night	9% 19% 7% 23% 13% 7% 4 3 2 3 8%	6129
	21st to end	Night	11% 20% 6% 20% 11% 8% 6% 3 3 4 9%	8184

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	84% 1 7% 7%	3527
	11th to 20th	Day	86% 2 5% 6% 2	3728
	21st to end	Day	69% 3 10% 11% 7%	4500
February	1st to 10th	Day	68% 8% 7% 13% 5%	1585
	11th to 20th	Day	64% 5% 9% 15% 7%	1791
	21st to end	Day	61% 6% 8% 15% 11%	1557
March	1st to 10th	Day	79% 4 4 9% 4	4525
	11th to 20th	Day	73% 2 5% 12% 7%	4963
	21st to end	Day	72% 2 3 15% 8%	5786
April	1st to 10th	Day	71% 3 5% 14% 6% 1	2407
	11th to 20th	Day	66% 2 6% 18% 6% 1	2654
	21st to end	Day	67% 3 9% 17% 6%	2800
May	1st to 10th	Day	63% 2 11% 17% 7%	6372
	11th to 20th	Day	71% 2 6% 15% 6%	7144
	21st to end	Day	47% 2 8% 28% 15%	7953
June	1st to 10th	Day	56% 2 10% 23% 9%	3200
	11th to 20th	Day	54% 3 10% 22% 11%	3200
	21st to end	Day	60% 4 10% 20% 6%	3200
July	1st to 10th	Day	60% 2 13% 20% 4	7201
	11th to 20th	Day	67% 2 10% 18% 3	7193
	21st to end	Day	70% 2 18% 8% 2	7405
August	1st to 10th	Day	73% 3 11% 13% 1	4757
	11th to 20th	Day	54% 1 16% 26% 2	4541
	21st to end	Day	61% 3 12% 22% 3	4790
September	1st to 10th	Day	74% 3 11% 11% 1	2400
	11th to 20th	Day	75% 2 10% 11% 1	2400
	21st to end	Day	78% 2 10% 9% 1	2106
October	1st to 10th	Day	69% 2 17% 11% 1	3260
	11th to 20th	Day	76% 3 13% 7% 2	3051
	21st to end	Day	83% 2 8% 6% 1	2893
November	1st to 10th	Day	82% 2 6% 8% 2	1630
	11th to 20th	Day	82% 2 5% 9% 1	1444
	21st to end	Day	82% 3 5% 8% 1	1260
December	1st to 10th	Day	68% 3 14% 12% 3	2020
	11th to 20th	Day	86% 2 5% 4 3	2313
	21st to end	Day	81% 2 6% 8% 2	3058
January	1st to 10th	Night	84% 2 5% 7% 2	9428
	11th to 20th	Night	83% 2 5% 6% 3	9282
	21st to end	Night	71% 3 8% 11% 6% 1	9714
February	1st to 10th	Night	68% 8% 7% 13% 4	3034
	11th to 20th	Night	63% 7% 9% 15% 6%	2722
	21st to end	Night	64% 5% 7% 16% 8%	2249
March	1st to 10th	Night	73% 3 6% 12% 6%	5547
	11th to 20th	Night	69% 3 7% 13% 8% 1	5135
	21st to end	Night	71% 3 3 13% 10%	5146
April	1st to 10th	Night	66% 4 4 17% 9% 1	2000
	11th to 20th	Night	65% 2 4 19% 9% 1	1705
	21st to end	Night	63% 2 8% 19% 8% 1	1600
May	1st to 10th	Night	66% 2 5% 19% 8% 1	3583
	11th to 20th	Night	71% 2 6% 16% 5%	2791
	21st to end	Night	48% 2 7% 24% 19%	2968
June	1st to 10th	Night	54% 2 9% 23% 11% 1	1200
	11th to 20th	Night	55% 3 8% 23% 11%	1200
	21st to end	Night	60% 3 8% 21% 7% 1	1200
July	1st to 10th	Night	64% 2 14% 13% 7%	2690
	11th to 20th	Night	68% 3 9% 17% 4	2684
	21st to end	Night	71% 2 16% 8% 3	3160
August	1st to 10th	Night	72% 2 12% 12% 2	2373
	11th to 20th	Night	57% 2 12% 26% 2	2574
	21st to end	Night	59% 3 16% 18% 4	3079
September	1st to 10th	Night	73% 3 11% 11% 2	1993
	11th to 20th	Night	74% 2 10% 12% 1	2000
	21st to end	Night	75% 2 11% 9% 2	2290
October	1st to 10th	Night	70% 2 17% 9% 1	3920
	11th to 20th	Night	78% 3 9% 8% 2	4087
	21st to end	Night	78% 2 8% 10% 1 1	4894
November	1st to 10th	Night	82% 3 5% 8% 2	2888
	11th to 20th	Night	84% 2 6% 7% 1	3171
	21st to end	Night	80% 3 6% 9% 1 1	3360
December	1st to 10th	Night	66% 2 15% 13% 4	5400
	11th to 20th	Night	82% 2 6% 5% 4 1	6129
	21st to end	Night	79% 2 6% 9% 4	8184

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	12% 9% 29% 31% 15% 4	220
	11th to 20th	Day	10% 10% 32% 27% 15% 5%	220
	21st to end	Day	7% 7% 32% 27% 19% 9%	242
February	1st to 10th	Day	7% 6% 29% 35% 18% 6%	220
	11th to 20th	Day	3 6% 30% 38% 14% 10%	298
	21st to end	Day	7% 8% 33% 38% 11% 4	273
March	1st to 10th	Day	9% 8% 25% 30% 19% 8%	510
	11th to 20th	Day	10% 8% 29% 32% 16% 6%	528
	21st to end	Day	14% 11% 24% 29% 14% 8%	550
April	1st to 10th	Day	17% 4 23% 28% 22% 7%	500
	11th to 20th	Day	18% 7% 20% 27% 16% 11%	492
	21st to end	Day	16% 6% 28% 25% 18% 8%	500
May	1st to 10th	Day	20% 8% 23% 24% 18% 7%	505
	11th to 20th	Day	21% 9% 23% 27% 15% 4	881
	21st to end	Day	22% 7% 26% 30% 12% 3	1006
June	1st to 10th	Day	20% 5% 28% 25% 16% 7%	930
	11th to 20th	Day	23% 7% 24% 28% 13% 5%	930
	21st to end	Day	27% 5% 22% 29% 14% 3	930
July	1st to 10th	Day	28% 6% 17% 30% 15% 5%	916
	11th to 20th	Day	33% 6% 19% 26% 13% 3	912
	21st to end	Day	32% 5% 15% 26% 16% 6%	884
August	1st to 10th	Day	41% 4 11% 22% 17% 6%	659
	11th to 20th	Day	38% 3 14% 21% 17% 7%	519
	21st to end	Day	36% 5% 17% 22% 13% 7%	583
September	1st to 10th	Day	41% 8% 19% 20% 8% 4	530
	11th to 20th	Day	43% 8% 18% 18% 11% 2	530
	21st to end	Day	45% 7% 18% 20% 6% 3	530
October	1st to 10th	Day	39% 14% 23% 15% 8% 2	530
	11th to 20th	Day	33% 8% 24% 21% 12% 2	467
	21st to end	Day	28% 12% 21% 21% 11% 6%	289
November	1st to 10th	Day	30% 7% 20% 25% 14% 4	220
	11th to 20th	Day	25% 11% 20% 25% 13% 6%	220
	21st to end	Day	14% 9% 25% 30% 18% 4	220
December	1st to 10th	Day	14% 11% 26% 29% 15% 5%	220
	11th to 20th	Day	19% 10% 21% 28% 16% 5%	220
	21st to end	Day	16% 9% 30% 26% 12% 7%	242
January	1st to 10th	Night	13% 7% 27% 32% 15% 6%	1160
	11th to 20th	Night	10% 7% 26% 33% 19% 5%	1124
	21st to end	Night	7% 6% 23% 35% 23% 7%	1155
February	1st to 10th	Night	7% 5% 24% 35% 21% 7%	934
	11th to 20th	Night	4 4 22% 33% 25% 11%	823
	21st to end	Night	7% 7% 24% 33% 22% 7%	692
March	1st to 10th	Night	10% 6% 22% 30% 23% 9%	840
	11th to 20th	Night	10% 7% 27% 32% 18% 6%	829
	21st to end	Night	13% 6% 25% 33% 18% 5%	880
April	1st to 10th	Night	18% 7% 23% 26% 20% 7%	800
	11th to 20th	Night	14% 7% 18% 33% 21% 8%	521
	21st to end	Night	16% 8% 22% 36% 15% 3	400
May	1st to 10th	Night	26% 5% 22% 26% 18% 4	400
	11th to 20th	Night	24% 6% 23% 30% 14% 3	394
	21st to end	Night	21% 7% 24% 32% 14% 1	433
June	1st to 10th	Night	22% 4 23% 27% 20% 5%	400
	11th to 20th	Night	20% 7% 18% 35% 17% 4	400
	21st to end	Night	23% 6% 16% 35% 19% 2	400
July	1st to 10th	Night	30% 4 14% 29% 20% 3	390
	11th to 20th	Night	32% 5% 18% 30% 13% 2	388
	21st to end	Night	32% 6% 8% 25% 24% 4	438
August	1st to 10th	Night	39% 3 8% 24% 23% 3	398
	11th to 20th	Night	37% 4 9% 26% 22% 3	396
	21st to end	Night	40% 3 13% 22% 15% 6%	568
September	1st to 10th	Night	44% 7% 16% 20% 10% 3	793
	11th to 20th	Night	42% 7% 17% 24% 10% 1	800
	21st to end	Night	43% 10% 16% 18% 12% 1	800
October	1st to 10th	Night	43% 10% 20% 17% 8% 1	800
	11th to 20th	Night	38% 10% 18% 20% 12% 1	800
	21st to end	Night	34% 9% 18% 21% 14% 3	880
November	1st to 10th	Night	32% 9% 20% 23% 12% 4	828
	11th to 20th	Night	24% 11% 23% 25% 14% 2	971
	21st to end	Night	16% 10% 26% 30% 15% 3	1160
December	1st to 10th	Night	14% 12% 26% 31% 15% 2	1160
	11th to 20th	Night	14% 11% 24% 30% 17% 4	1160
	21st to end	Night	12% 9% 28% 30% 16% 5%	1276

Page generated at 2026-03-15 02:23:52. Version ac07

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