Winnipeg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Winnipeg clear sky chart from 2005-11-06 to 2025-09-04.

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	11% 9% 3 9% 6% 5% 5% 4 6% 8% 35%	130398
	Night	9% 10% 4 10% 6% 5% 5% 4 6% 7% 34%	127087
Transparency	Day	48% 3 15% 25% 9% 1	130096
	Night	50% 3 13% 23% 10% 1	126970
Seeing	Day	16% 9% 33% 27% 12% 3	17469
	Night	15% 7% 32% 32% 13% 1	27303

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	1st to 10th	Day	7% 15% 6% 13% 7% 6% 7% 6% 6% 6% 20%	3179
	11th to 20th	Day	5% 11% 5% 14% 10% 9% 9% 11% 9% 7% 10%	3159
	21st to end	Day	6% 16% 7% 15% 8% 8% 7% 3 6% 7% 16%	3986
February	1st to 10th	Day	9% 13% 6% 11% 10% 8% 7% 6% 8% 6% 17%	1714
	11th to 20th	Day	7% 10% 3 9% 7% 9% 7% 6% 8% 8% 24%	1754
	21st to end	Day	7% 10% 4 13% 8% 8% 7% 6% 6% 7% 24%	1562
March	1st to 10th	Day	9% 12% 4 10% 8% 6% 5% 4 7% 8% 28%	4619
	11th to 20th	Day	8% 11% 5% 15% 10% 7% 5% 4 5% 8% 23%	4978
	21st to end	Day	9% 13% 6% 12% 6% 5% 5% 4 5% 6% 30%	5464
April	1st to 10th	Day	10% 12% 4 9% 6% 4 5% 4 5% 7% 34%	2440
	11th to 20th	Day	13% 11% 4 8% 6% 5% 4 4 6% 7% 34%	2572
	21st to end	Day	16% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	2600
May	1st to 10th	Day	13% 7% 2 5% 4 3 4 3 5% 7% 46%	6102
	11th to 20th	Day	20% 8% 2 6% 5% 4 5% 4 6% 8% 32%	6623
	21st to end	Day	14% 7% 2 6% 4 3 4 3 4 6% 46%	7428
June	1st to 10th	Day	15% 7% 2 7% 6% 5% 4 4 6% 8% 36%	3000
	11th to 20th	Day	16% 6% 3 7% 5% 4 5% 4 6% 8% 36%	3000
	21st to end	Day	12% 6% 3 6% 4 5% 6% 6% 8% 8% 36%	3000
July	1st to 10th	Day	7% 4 2 6% 4 5% 5% 5% 8% 10% 44%	6800
	11th to 20th	Day	9% 4 2 6% 5% 5% 5% 4 6% 9% 43%	6800
	21st to end	Day	8% 4 2 6% 5% 5% 5% 4 7% 10% 45%	7321
August	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 10% 46%	4400
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 4 5% 8% 46%	4171
	21st to end	Day	13% 5% 2 6% 3 4 4 3 6% 8% 45%	4675
September	1st to 10th	Day	10% 6% 2 5% 3 4 4 3 5% 8% 51%	2400
	11th to 20th	Day	13% 6% 3 7% 4 3 4 4 6% 8% 40%	2090
	21st to end	Day	16% 6% 3 6% 4 3 4 4 5% 8% 41%	2090
October	1st to 10th	Day	13% 7% 2 6% 3 4 5% 3 5% 6% 46%	3207
	11th to 20th	Day	12% 9% 3 7% 4 4 5% 4 6% 8% 39%	3080
	21st to end	Day	14% 13% 4 7% 4 5% 5% 4 5% 9% 32%	3091
November	1st to 10th	Day	17% 15% 4 10% 4 5% 4 2 6% 5% 27%	1591
	11th to 20th	Day	11% 15% 5% 14% 6% 6% 4 3 5% 5% 26%	1600
	21st to end	Day	12% 15% 5% 13% 8% 5% 6% 3 4 5% 24%	1475
December	1st to 10th	Day	10% 16% 6% 15% 8% 7% 6% 5% 6% 5% 15%	2290
	11th to 20th	Day	9% 14% 5% 14% 6% 5% 4 5% 8% 10% 20%	2639
	21st to end	Day	7% 15% 6% 18% 8% 6% 5% 4 5% 6% 19%	3498
January	1st to 10th	Night	4 13% 7% 15% 8% 9% 7% 6% 6% 5% 20%	6787
	11th to 20th	Night	4 14% 6% 13% 9% 8% 11% 9% 8% 5% 14%	6759
	21st to end	Night	7% 18% 8% 14% 7% 5% 6% 4 6% 6% 19%	6975
February	1st to 10th	Night	8% 12% 5% 11% 7% 7% 9% 5% 5% 6% 25%	2685
	11th to 20th	Night	6% 9% 3 8% 6% 7% 6% 6% 7% 7% 34%	2533
	21st to end	Night	7% 11% 5% 12% 6% 7% 5% 4 6% 7% 30%	2085
March	1st to 10th	Night	8% 11% 4 11% 6% 6% 6% 4 6% 7% 31%	5248
	11th to 20th	Night	7% 11% 4 8% 6% 5% 4 4 6% 8% 38%	4980
	21st to end	Night	12% 11% 4 10% 5% 4 4 3 5% 6% 36%	5467
April	1st to 10th	Night	11% 8% 3 7% 5% 3 4 4 6% 7% 42%	1959
	11th to 20th	Night	14% 10% 3 8% 6% 4 4 4 4 6% 36%	1779
	21st to end	Night	13% 8% 3 8% 5% 6% 5% 4 5% 7% 37%	1800
May	1st to 10th	Night	13% 8% 3 6% 4 4 4 3 5% 6% 43%	3878
	11th to 20th	Night	17% 6% 2 6% 4 5% 5% 4 7% 8% 36%	3278
	21st to end	Night	13% 5% 2 6% 3 3 3 3 5% 7% 50%	3470
June	1st to 10th	Night	11% 6% 2 7% 4 4 4 4 8% 7% 43%	1400
	11th to 20th	Night	15% 5% 2 5% 4 5% 3 4 6% 8% 43%	1400
	21st to end	Night	10% 5% 2 5% 5% 5% 5% 5% 6% 9% 42%	1400
July	1st to 10th	Night	7% 3 1 5% 4 4 5% 4 6% 10% 51%	3180
	11th to 20th	Night	7% 3 2 5% 4 5% 5% 4 6% 10% 50%	3180
	21st to end	Night	5% 4 2 5% 4 5% 5% 4 6% 9% 49%	3542
August	1st to 10th	Night	6% 4 2 6% 4 4 5% 5% 7% 8% 49%	2758
	11th to 20th	Night	9% 3 1 5% 3 4 5% 4 6% 9% 51%	2888
	21st to end	Night	10% 5% 2 6% 3 4 5% 4 5% 7% 48%	3234
September	1st to 10th	Night	9% 4 2 5% 4 3 5% 3 6% 8% 53%	1843
	11th to 20th	Night	14% 6% 2 5% 4 4 4 4 5% 8% 45%	2090
	21st to end	Night	16% 6% 3 7% 4 4 4 3 4 7% 42%	2090
October	1st to 10th	Night	16% 8% 3 5% 3 3 3 2 4 6% 46%	3720
	11th to 20th	Night	10% 9% 3 7% 5% 5% 5% 4 5% 7% 41%	3836
	21st to end	Night	9% 10% 3 8% 4 5% 6% 3 5% 6% 40%	4467
November	1st to 10th	Night	13% 14% 5% 10% 6% 5% 5% 4 5% 6% 28%	2706
	11th to 20th	Night	11% 15% 7% 12% 7% 4 4 3 5% 5% 26%	2800
	21st to end	Night	12% 14% 6% 13% 7% 6% 5% 4 4 5% 25%	2922
December	1st to 10th	Night	7% 17% 6% 17% 11% 7% 6% 4 6% 5% 15%	4900
	11th to 20th	Night	8% 14% 6% 14% 7% 5% 5% 5% 6% 7% 22%	5568
	21st to end	Night	8% 12% 5% 18% 10% 7% 6% 4 5% 5% 21%	7480

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	65% 2 10% 16% 6%	3179
	11th to 20th	Day	68% 3 8% 16% 5%	3180
	21st to end	Day	69% 2 12% 13% 3	3986
February	1st to 10th	Day	64% 3 11% 13% 8% 1	1714
	11th to 20th	Day	53% 4 13% 22% 7%	1763
	21st to end	Day	57% 5% 12% 18% 8%	1562
March	1st to 10th	Day	53% 4 17% 16% 9%	4619
	11th to 20th	Day	60% 3 14% 17% 5%	4980
	21st to end	Day	54% 4 11% 22% 8%	5464
April	1st to 10th	Day	48% 4 12% 26% 10% 1	2440
	11th to 20th	Day	49% 2 12% 24% 11% 1	2572
	21st to end	Day	49% 4 15% 23% 8% 1	2600
May	1st to 10th	Day	38% 3 13% 27% 19% 1	6102
	11th to 20th	Day	50% 3 10% 25% 11% 1	6627
	21st to end	Day	40% 3 8% 24% 21% 4	7428
June	1st to 10th	Day	46% 4 13% 25% 11% 1	3000
	11th to 20th	Day	45% 4 16% 24% 10% 1	3000
	21st to end	Day	42% 6% 20% 24% 8% 1	3000
July	1st to 10th	Day	35% 3 26% 29% 7%	6726
	11th to 20th	Day	37% 3 20% 35% 5%	6719
	21st to end	Day	35% 3 23% 33% 6%	7115
August	1st to 10th	Day	34% 3 20% 32% 10%	4384
	11th to 20th	Day	38% 2 21% 34% 5%	4210
	21st to end	Day	38% 2 23% 31% 6%	4674
September	1st to 10th	Day	33% 4 18% 35% 10% 1	2400
	11th to 20th	Day	42% 4 19% 29% 5% 1	2090
	21st to end	Day	43% 3 17% 30% 7%	2090
October	1st to 10th	Day	41% 2 15% 33% 9%	3207
	11th to 20th	Day	43% 3 11% 29% 13%	3080
	21st to end	Day	51% 3 17% 24% 6%	3091
November	1st to 10th	Day	60% 3 14% 19% 4 1	1591
	11th to 20th	Day	60% 3 15% 17% 5%	1600
	21st to end	Day	63% 3 15% 15% 3	1475
December	1st to 10th	Day	69% 6% 11% 9% 5%	2290
	11th to 20th	Day	59% 2 15% 16% 7%	2640
	21st to end	Day	67% 2 9% 17% 5%	3498
January	1st to 10th	Night	65% 3 10% 14% 8%	6787
	11th to 20th	Night	69% 3 7% 17% 4	6800
	21st to end	Night	66% 3 12% 15% 4	6975
February	1st to 10th	Night	59% 3 12% 16% 9%	2685
	11th to 20th	Night	47% 4 15% 24% 9%	2534
	21st to end	Night	54% 3 11% 22% 11%	2085
March	1st to 10th	Night	51% 4 14% 18% 10% 3	5248
	11th to 20th	Night	44% 3 15% 24% 12%	4980
	21st to end	Night	50% 3 9% 25% 12%	5467
April	1st to 10th	Night	42% 3 11% 25% 16% 3	1959
	11th to 20th	Night	50% 2 7% 23% 16% 2	1779
	21st to end	Night	47% 3 11% 26% 12% 2	1800
May	1st to 10th	Night	41% 3 10% 26% 19%	3878
	11th to 20th	Night	45% 2 12% 26% 12% 3	3278
	21st to end	Night	35% 3 9% 24% 24% 5%	3470
June	1st to 10th	Night	38% 6% 18% 24% 14%	1400
	11th to 20th	Night	39% 4 18% 25% 13% 2	1400
	21st to end	Night	37% 4 20% 29% 9% 1	1400
July	1st to 10th	Night	30% 3 24% 32% 10%	3145
	11th to 20th	Night	31% 3 20% 39% 7% 1	3138
	21st to end	Night	32% 3 25% 33% 6%	3443
August	1st to 10th	Night	32% 2 16% 34% 14% 1	2750
	11th to 20th	Night	31% 3 25% 32% 10%	2915
	21st to end	Night	36% 3 19% 34% 9%	3234
September	1st to 10th	Night	31% 4 17% 34% 14% 1	1843
	11th to 20th	Night	39% 4 18% 27% 11% 1	2090
	21st to end	Night	43% 3 12% 30% 10% 1	2090
October	1st to 10th	Night	41% 2 11% 33% 13%	3720
	11th to 20th	Night	44% 3 11% 31% 10%	3836
	21st to end	Night	46% 3 14% 32% 5%	4467
November	1st to 10th	Night	57% 3 16% 17% 7% 1	2706
	11th to 20th	Night	60% 4 14% 15% 5%	2800
	21st to end	Night	64% 4 13% 13% 5%	2922
December	1st to 10th	Night	73% 3 12% 9% 3	4900
	11th to 20th	Night	61% 2 13% 12% 12%	5566
	21st to end	Night	66% 2 9% 17% 6%	7480

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% 34% 28% 14% 2	300
	11th to 20th	Day	12% 9% 34% 32% 11% 1	300
	21st to end	Day	18% 8% 30% 29% 13% 2	330
February	1st to 10th	Day	16% 12% 33% 31% 6% 1	300
	11th to 20th	Day	11% 15% 33% 28% 12% 1	300
	21st to end	Day	10% 11% 43% 28% 8% 1	249
March	1st to 10th	Day	15% 10% 35% 29% 9% 1	300
	11th to 20th	Day	15% 14% 34% 23% 12% 2	300
	21st to end	Day	18% 8% 36% 26% 11% 1	330
April	1st to 10th	Day	14% 11% 34% 29% 9% 3	540
	11th to 20th	Day	19% 14% 31% 25% 10% 1	690
	21st to end	Day	18% 13% 33% 26% 9% 1	700
May	1st to 10th	Day	18% 12% 34% 25% 10% 1	703
	11th to 20th	Day	21% 10% 33% 24% 10% 2	725
	21st to end	Day	20% 9% 26% 28% 14% 3	789
June	1st to 10th	Day	18% 12% 30% 22% 14% 4	730
	11th to 20th	Day	16% 12% 34% 27% 8% 3	730
	21st to end	Day	13% 9% 31% 28% 14% 5%	730
July	1st to 10th	Day	8% 6% 33% 27% 17% 9%	721
	11th to 20th	Day	12% 8% 32% 27% 17% 4	718
	21st to end	Day	8% 6% 34% 31% 15% 7%	794
August	1st to 10th	Day	10% 6% 30% 30% 18% 5%	726
	11th to 20th	Day	12% 4 27% 31% 19% 7%	715
	21st to end	Day	14% 7% 31% 29% 15% 4	803
September	1st to 10th	Day	10% 10% 33% 32% 13% 2	586
	11th to 20th	Day	17% 9% 42% 24% 7% 2	300
	21st to end	Day	22% 9% 36% 26% 7% 1	300
October	1st to 10th	Day	23% 13% 27% 26% 9% 3	300
	11th to 20th	Day	19% 10% 39% 25% 6% 1	300
	21st to end	Day	26% 9% 32% 23% 8% 2	330
November	1st to 10th	Day	28% 9% 28% 24% 10% 1	300
	11th to 20th	Day	20% 11% 41% 21% 7% 1	300
	21st to end	Day	21% 13% 38% 24% 4	300
December	1st to 10th	Day	16% 6% 37% 26% 12% 3	300
	11th to 20th	Day	14% 11% 40% 29% 6%	300
	21st to end	Day	14% 7% 34% 30% 13% 3	330
January	1st to 10th	Night	12% 8% 33% 31% 14% 3	1000
	11th to 20th	Night	16% 7% 33% 33% 12%	1000
	21st to end	Night	14% 8% 32% 32% 12% 1	1100
February	1st to 10th	Night	14% 7% 30% 33% 14% 2	1000
	11th to 20th	Night	11% 7% 30% 35% 14% 3	979
	21st to end	Night	10% 8% 38% 29% 13% 2	765
March	1st to 10th	Night	14% 8% 31% 32% 14% 2	752
	11th to 20th	Night	13% 7% 39% 28% 12% 1	600
	21st to end	Night	19% 7% 29% 27% 15% 3	660
April	1st to 10th	Night	15% 7% 29% 35% 12% 2	600
	11th to 20th	Night	18% 7% 29% 34% 11% 1	593
	21st to end	Night	18% 8% 31% 34% 10% 1	600
May	1st to 10th	Night	18% 8% 34% 30% 9% 1	600
	11th to 20th	Night	19% 7% 32% 29% 13% 1	591
	21st to end	Night	17% 6% 33% 33% 11%	650
June	1st to 10th	Night	14% 6% 32% 34% 13% 1	600
	11th to 20th	Night	17% 6% 33% 32% 13%	600
	21st to end	Night	11% 5% 25% 38% 19% 1	600
July	1st to 10th	Night	6% 3 28% 41% 19% 2	585
	11th to 20th	Night	8% 5% 28% 40% 18% 1	582
	21st to end	Night	7% 3 27% 40% 21% 3	657
August	1st to 10th	Night	8% 2 22% 49% 17% 2	597
	11th to 20th	Night	10% 4 25% 39% 19% 4	594
	21st to end	Night	12% 5% 23% 39% 19% 1	660
September	1st to 10th	Night	11% 5% 32% 35% 16% 2	579
	11th to 20th	Night	15% 8% 28% 37% 13%	570
	21st to end	Night	19% 5% 36% 29% 11% 1	570
October	1st to 10th	Night	22% 7% 32% 29% 9%	706
	11th to 20th	Night	20% 8% 34% 28% 10%	793
	21st to end	Night	21% 9% 29% 30% 10% 1	1045
November	1st to 10th	Night	19% 10% 34% 25% 11% 1	975
	11th to 20th	Night	20% 9% 33% 27% 9% 2	1000
	21st to end	Night	19% 10% 39% 24% 7% 1	1000
December	1st to 10th	Night	14% 6% 32% 33% 12% 3	1000
	11th to 20th	Night	18% 7% 37% 29% 8% 2	1000
	21st to end	Night	20% 8% 30% 28% 13% 2	1100

Page generated at 2025-09-01 00:51:08. Version ac07

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