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 2024-01-16.

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	17% 14% 6% 10% 8% 5% 7% 6% 5% 5% 17%	74519
	Night	15% 15% 7% 12% 10% 5% 7% 6% 5% 4 13%	75302
Transparency	Day	69% 3 9% 14% 5%	74186
	Night	72% 4 7% 12% 4	75171
Seeing	Day	25% 7% 21% 26% 15% 6%	15513
	Night	22% 7% 21% 28% 17% 5%	23660

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	9% 13% 6% 16% 13% 10% 12% 6% 5% 4 7%	1138
	11th to 20th	Day	5% 14% 5% 10% 12% 10% 18% 11% 7% 3 5%	1168
	21st to end	Day	3 7% 6% 15% 11% 10% 14% 14% 10% 4 7%	1386
February	1st to 10th	Day	4 6% 6% 11% 11% 10% 15% 18% 10% 4 5%	1358
	11th to 20th	Day	4 7% 5% 8% 12% 11% 14% 14% 9% 6% 11%	1520
	21st to end	Day	5% 9% 4 9% 9% 7% 13% 13% 12% 7% 12%	1332
March	1st to 10th	Day	4 10% 5% 12% 12% 6% 12% 12% 10% 6% 10%	1770
	11th to 20th	Day	6% 9% 5% 11% 10% 8% 9% 13% 8% 5% 14%	1944
	21st to end	Day	9% 12% 5% 10% 10% 7% 12% 10% 4 4 17%	2304
April	1st to 10th	Day	11% 14% 5% 10% 11% 8% 10% 6% 4 4 16%	2165
	11th to 20th	Day	8% 10% 4 11% 12% 8% 10% 5% 5% 6% 22%	2385
	21st to end	Day	11% 13% 6% 11% 12% 5% 6% 5% 4 6% 23%	2520
May	1st to 10th	Day	16% 14% 6% 14% 9% 4 4 5% 4 5% 17%	2521
	11th to 20th	Day	14% 14% 8% 16% 8% 4 5% 4 4 5% 20%	2796
	21st to end	Day	16% 15% 9% 12% 7% 4 4 5% 4 5% 20%	3113
June	1st to 10th	Day	12% 10% 8% 9% 6% 3 5% 5% 5% 7% 29%	2880
	11th to 20th	Day	17% 10% 5% 7% 6% 3 5% 6% 5% 6% 30%	2880
	21st to end	Day	22% 11% 4 7% 7% 3 5% 5% 5% 6% 25%	2880
July	1st to 10th	Day	23% 12% 5% 8% 6% 4 5% 5% 5% 6% 22%	2880
	11th to 20th	Day	23% 16% 5% 7% 6% 4 5% 5% 5% 6% 19%	2880
	21st to end	Day	23% 15% 4 8% 6% 4 5% 5% 5% 6% 22%	3022
August	1st to 10th	Day	30% 13% 4 8% 6% 4 5% 4 3 5% 17%	2627
	11th to 20th	Day	28% 13% 4 7% 6% 3 4 3 3 6% 24%	2481
	21st to end	Day	29% 11% 3 6% 6% 3 5% 5% 5% 6% 20%	2644
September	1st to 10th	Day	33% 16% 5% 7% 5% 4 4 5% 4 4 14%	2160
	11th to 20th	Day	31% 19% 4 9% 5% 3 4 4 3 4 15%	2160
	21st to end	Day	33% 22% 4 7% 5% 2 4 3 4 4 11%	1897
October	1st to 10th	Day	29% 24% 5% 7% 6% 3 3 3 3 2 14%	1800
	11th to 20th	Day	22% 22% 6% 9% 7% 4 3 4 4 4 14%	1699
	21st to end	Day	21% 25% 8% 10% 6% 3 3 3 3 4 13%	1627
November	1st to 10th	Day	19% 25% 9% 13% 8% 4 4 4 2 4 9%	1472
	11th to 20th	Day	18% 27% 11% 13% 7% 4 4 2 3 3 8%	1307
	21st to end	Day	11% 20% 13% 19% 11% 4 3 4 2 2 9%	1140
December	1st to 10th	Day	9% 17% 13% 21% 13% 4 4 2 4 4 7%	1140
	11th to 20th	Day	7% 13% 8% 20% 20% 9% 7% 5% 3 3 6%	1433
	21st to end	Day	7% 16% 7% 17% 20% 8% 8% 5% 2 3 9%	2090
January	1st to 10th	Night	8% 15% 7% 15% 14% 9% 14% 8% 4 3 4	3027
	11th to 20th	Night	6% 12% 5% 13% 14% 10% 16% 12% 6% 2 5%	2915
	21st to end	Night	4 8% 5% 14% 14% 10% 14% 14% 6% 3 8%	2970
February	1st to 10th	Night	4 8% 5% 11% 12% 10% 15% 16% 12% 3 4	2601
	11th to 20th	Night	3 8% 4 10% 11% 10% 14% 13% 13% 5% 9%	2322
	21st to end	Night	4 9% 5% 12% 10% 7% 14% 11% 11% 5% 11%	1924
March	1st to 10th	Night	6% 7% 6% 12% 14% 6% 11% 11% 11% 5% 11%	2176
	11th to 20th	Night	6% 12% 6% 11% 10% 6% 9% 13% 9% 5% 14%	2012
	21st to end	Night	8% 12% 6% 11% 9% 6% 12% 10% 5% 5% 17%	2052
April	1st to 10th	Night	12% 15% 5% 10% 8% 5% 10% 7% 5% 5% 17%	1800
	11th to 20th	Night	7% 10% 5% 11% 11% 8% 9% 5% 4 7% 24%	1534
	21st to end	Night	11% 14% 5% 9% 11% 6% 4 5% 4 6% 26%	1440
May	1st to 10th	Night	17% 16% 6% 12% 9% 4 5% 3 4 5% 19%	1436
	11th to 20th	Night	18% 15% 10% 14% 6% 2 5% 2 3 6% 19%	1098
	21st to end	Night	18% 15% 9% 11% 6% 2 6% 4 5% 4 20%	1163
June	1st to 10th	Night	13% 14% 8% 9% 4 2 3 3 4 7% 33%	1080
	11th to 20th	Night	18% 9% 5% 8% 6% 3 4 4 5% 6% 32%	1080
	21st to end	Night	19% 12% 6% 8% 6% 5% 4 4 5% 5% 27%	1080
July	1st to 10th	Night	24% 15% 5% 7% 5% 3 4 4 6% 6% 21%	1080
	11th to 20th	Night	26% 17% 6% 8% 6% 3 4 4 3 5% 19%	1080
	21st to end	Night	26% 14% 4 6% 5% 4 4 4 5% 6% 22%	1293
August	1st to 10th	Night	30% 16% 4 6% 5% 3 4 4 6% 5% 16%	1310
	11th to 20th	Night	29% 14% 4 6% 6% 3 4 4 4 6% 21%	1420
	21st to end	Night	33% 12% 3 6% 5% 3 5% 5% 4 5% 18%	1698
September	1st to 10th	Night	35% 17% 3 7% 5% 3 3 3 3 4 17%	1793
	11th to 20th	Night	32% 19% 5% 8% 5% 3 3 2 3 5% 15%	1800
	21st to end	Night	30% 23% 5% 6% 5% 2 3 4 4 5% 14%	2060
October	1st to 10th	Night	33% 23% 4 7% 5% 3 3 3 3 4 13%	2160
	11th to 20th	Night	25% 25% 7% 8% 6% 2 3 3 4 4 14%	2260
	21st to end	Night	23% 26% 8% 10% 6% 4 3 3 3 3 11%	2726
November	1st to 10th	Night	20% 25% 9% 11% 9% 3 4 4 3 3 8%	2606
	11th to 20th	Night	17% 27% 11% 14% 8% 3 4 3 3 3 6%	2869
	21st to end	Night	10% 20% 13% 19% 9% 3 6% 4 4 3 10%	3040
December	1st to 10th	Night	9% 17% 11% 24% 16% 4 5% 2 3 2 6%	3040
	11th to 20th	Night	7% 13% 8% 18% 20% 5% 6% 5% 3 4 10%	3769
	21st to end	Night	9% 14% 7% 16% 17% 6% 8% 6% 4 4 9%	5588

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	80% 3 6% 10% 1	1139
	11th to 20th	Day	76% 6% 5% 10% 3	1168
	21st to end	Day	67% 8% 3 14% 9%	1386
February	1st to 10th	Day	65% 9% 7% 14% 5%	1358
	11th to 20th	Day	63% 6% 9% 15% 7%	1529
	21st to end	Day	60% 6% 8% 14% 11%	1332
March	1st to 10th	Day	64% 8% 9% 14% 4	1773
	11th to 20th	Day	63% 5% 6% 18% 8%	1944
	21st to end	Day	70% 4 6% 14% 6%	2304
April	1st to 10th	Day	72% 3 5% 12% 6% 1	2165
	11th to 20th	Day	64% 2 6% 19% 6% 1	2385
	21st to end	Day	66% 3 9% 17% 6%	2520
May	1st to 10th	Day	71% 1 6% 17% 4	2521
	11th to 20th	Day	70% 2 8% 15% 5%	2800
	21st to end	Day	67% 3 8% 16% 5%	3113
June	1st to 10th	Day	56% 2 10% 23% 9%	2880
	11th to 20th	Day	53% 3 10% 22% 11%	2880
	21st to end	Day	59% 4 10% 21% 7%	2880
July	1st to 10th	Day	62% 4 11% 21% 3	2801
	11th to 20th	Day	64% 4 13% 17% 2	2793
	21st to end	Day	63% 4 17% 12% 4	2854
August	1st to 10th	Day	70% 4 12% 12% 2	2611
	11th to 20th	Day	64% 2 15% 15% 4	2481
	21st to end	Day	66% 3 12% 16% 3	2644
September	1st to 10th	Day	75% 3 10% 11% 1	2160
	11th to 20th	Day	76% 2 9% 11% 1	2160
	21st to end	Day	79% 2 10% 9% 1	1897
October	1st to 10th	Day	79% 3 8% 9% 1	1800
	11th to 20th	Day	74% 3 8% 12% 3	1699
	21st to end	Day	78% 2 10% 7% 1 1	1627
November	1st to 10th	Day	82% 2 6% 9% 1	1472
	11th to 20th	Day	83% 2 5% 8% 1	1307
	21st to end	Day	82% 3 5% 8% 1 1	1140
December	1st to 10th	Day	81% 2 8% 7% 2	1140
	11th to 20th	Day	82% 2 5% 6% 5%	1433
	21st to end	Day	82% 3 4 8% 3	2090
January	1st to 10th	Night	81% 5% 5% 8% 1	3027
	11th to 20th	Night	77% 6% 5% 9% 3	2915
	21st to end	Night	73% 6% 3 11% 7%	2970
February	1st to 10th	Night	66% 9% 7% 14% 4	2601
	11th to 20th	Night	62% 8% 9% 15% 6%	2324
	21st to end	Night	63% 6% 8% 15% 8%	1924
March	1st to 10th	Night	64% 5% 10% 16% 5% 1	2186
	11th to 20th	Night	64% 5% 5% 16% 10%	2013
	21st to end	Night	66% 6% 7% 14% 7%	2052
April	1st to 10th	Night	68% 4 3 15% 9% 1	1800
	11th to 20th	Night	63% 2 5% 20% 9% 1	1534
	21st to end	Night	61% 2 9% 19% 8% 1	1440
May	1st to 10th	Night	69% 1 4 19% 6%	1436
	11th to 20th	Night	69% 1 8% 16% 6%	1099
	21st to end	Night	67% 4 7% 18% 5%	1164
June	1st to 10th	Night	53% 2 9% 24% 11% 1	1080
	11th to 20th	Night	54% 3 8% 24% 11%	1080
	21st to end	Night	60% 4 8% 20% 7% 1	1080
July	1st to 10th	Night	62% 3 13% 17% 5%	1050
	11th to 20th	Night	66% 4 9% 18% 2	1044
	21st to end	Night	61% 4 15% 15% 5%	1221
August	1st to 10th	Night	69% 4 13% 11% 3	1302
	11th to 20th	Night	65% 3 12% 16% 4	1420
	21st to end	Night	68% 3 12% 13% 4	1698
September	1st to 10th	Night	74% 3 10% 11% 2	1793
	11th to 20th	Night	75% 2 10% 12% 1	1800
	21st to end	Night	75% 3 11% 9% 3	2060
October	1st to 10th	Night	78% 2 8% 10% 2	2160
	11th to 20th	Night	76% 3 6% 12% 3	2260
	21st to end	Night	81% 2 7% 7% 1 1	2726
November	1st to 10th	Night	82% 3 5% 8% 2	2606
	11th to 20th	Night	85% 2 5% 6% 2	2869
	21st to end	Night	79% 4 5% 10% 1 1	3040
December	1st to 10th	Night	85% 2 5% 6% 2	3040
	11th to 20th	Night	77% 3 6% 7% 6% 1	3769
	21st to end	Night	79% 3 4 9% 6%	5588

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	11% 9% 29% 29% 17% 4	180
	11th to 20th	Day	12% 12% 28% 27% 15% 5%	170
	21st to end	Day	7% 6% 31% 28% 19% 10%	176
February	1st to 10th	Day	4 6% 32% 33% 18% 8%	160
	11th to 20th	Day	4 6% 34% 39% 13% 6%	216
	21st to end	Day	8% 7% 30% 39% 11% 6%	198
March	1st to 10th	Day	8% 6% 23% 29% 23% 10%	393
	11th to 20th	Day	11% 7% 29% 33% 16% 4	420
	21st to end	Day	14% 10% 24% 29% 14% 10%	462
April	1st to 10th	Day	18% 4 20% 27% 23% 8%	420
	11th to 20th	Day	15% 8% 18% 28% 18% 12%	412
	21st to end	Day	16% 6% 27% 25% 17% 8%	420
May	1st to 10th	Day	21% 7% 21% 24% 19% 8%	424
	11th to 20th	Day	21% 8% 23% 27% 16% 5%	765
	21st to end	Day	24% 6% 25% 29% 12% 3	874
June	1st to 10th	Day	20% 4 28% 24% 17% 7%	810
	11th to 20th	Day	23% 6% 23% 29% 14% 6%	810
	21st to end	Day	29% 5% 20% 30% 15% 3	810
July	1st to 10th	Day	28% 6% 14% 32% 16% 6%	796
	11th to 20th	Day	33% 6% 18% 26% 13% 4	792
	21st to end	Day	30% 5% 13% 27% 18% 7%	766
August	1st to 10th	Day	39% 4 11% 21% 18% 6%	567
	11th to 20th	Day	37% 3 14% 19% 19% 8%	439
	21st to end	Day	37% 5% 17% 21% 13% 7%	495
September	1st to 10th	Day	43% 7% 18% 18% 9% 4	450
	11th to 20th	Day	44% 9% 18% 16% 11% 2	450
	21st to end	Day	46% 7% 19% 18% 6% 3	450
October	1st to 10th	Day	40% 13% 21% 16% 8% 2	450
	11th to 20th	Day	33% 8% 23% 21% 13% 3	399
	21st to end	Day	26% 12% 24% 20% 11% 7%	241
November	1st to 10th	Day	28% 7% 19% 27% 15% 4	180
	11th to 20th	Day	26% 11% 18% 26% 12% 7%	180
	21st to end	Day	14% 9% 25% 30% 18% 4	180
December	1st to 10th	Day	16% 11% 24% 29% 15% 4	180
	11th to 20th	Day	17% 9% 21% 32% 16% 6%	180
	21st to end	Day	15% 9% 28% 26% 14% 9%	198
January	1st to 10th	Night	13% 7% 24% 33% 16% 7%	1040
	11th to 20th	Night	11% 7% 25% 33% 18% 6%	989
	21st to end	Night	7% 5% 21% 35% 24% 8%	990
February	1st to 10th	Night	7% 5% 24% 33% 22% 9%	801
	11th to 20th	Night	5% 5% 23% 33% 25% 10%	703
	21st to end	Night	8% 7% 22% 32% 23% 8%	592
March	1st to 10th	Night	10% 3 20% 31% 25% 11%	720
	11th to 20th	Night	10% 7% 27% 33% 18% 6%	720
	21st to end	Night	13% 6% 24% 32% 19% 6%	792
April	1st to 10th	Night	18% 7% 22% 26% 20% 8%	720
	11th to 20th	Night	11% 6% 18% 34% 22% 9%	470
	21st to end	Night	16% 7% 23% 36% 15% 3	360
May	1st to 10th	Night	26% 4 21% 26% 19% 4	360
	11th to 20th	Night	25% 5% 23% 30% 15% 2	354
	21st to end	Night	22% 8% 23% 32% 14% 2	389
June	1st to 10th	Night	22% 3 22% 27% 21% 5%	360
	11th to 20th	Night	19% 6% 18% 36% 17% 5%	360
	21st to end	Night	24% 6% 15% 35% 18% 3	360
July	1st to 10th	Night	31% 5% 13% 29% 21% 3	350
	11th to 20th	Night	33% 6% 17% 29% 14% 1	348
	21st to end	Night	31% 6% 7% 26% 25% 5%	394
August	1st to 10th	Night	39% 3 8% 23% 23% 3	358
	11th to 20th	Night	36% 3 9% 25% 22% 4	356
	21st to end	Night	41% 3 12% 22% 15% 7%	510
September	1st to 10th	Night	45% 7% 15% 20% 10% 3	713
	11th to 20th	Night	43% 7% 16% 23% 11% 1	720
	21st to end	Night	44% 11% 16% 17% 12% 1	720
October	1st to 10th	Night	44% 11% 19% 17% 9% 1	720
	11th to 20th	Night	38% 10% 17% 21% 13% 1	720
	21st to end	Night	35% 9% 18% 20% 14% 3	792
November	1st to 10th	Night	31% 8% 21% 24% 12% 5%	746
	11th to 20th	Night	25% 10% 22% 25% 15% 2	869
	21st to end	Night	17% 10% 26% 30% 14% 3	1040
December	1st to 10th	Night	15% 12% 26% 30% 15% 2	1040
	11th to 20th	Night	14% 11% 23% 31% 18% 4	1040
	21st to end	Night	11% 8% 27% 31% 18% 5%	1144

Page generated at 2024-01-13 09:37:53. Version ac07

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