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 2024-11-04.

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	12% 9% 3 8% 6% 5% 5% 4 6% 7% 35%	105567
	Night	10% 10% 4 9% 6% 5% 5% 4 6% 7% 35%	102023
Transparency	Day	48% 4 16% 25% 8%	105310
	Night	49% 3 14% 24% 9% 1	101927
Seeing	Day	15% 9% 33% 27% 12% 3	16251
	Night	15% 7% 31% 32% 13% 1	26156

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	9% 16% 5% 12% 8% 7% 6% 6% 5% 5% 21%	2219
	11th to 20th	Day	5% 10% 6% 17% 14% 12% 9% 6% 8% 5% 9%	2199
	21st to end	Day	9% 19% 7% 15% 7% 7% 7% 4 5% 5% 15%	2776
February	1st to 10th	Day	9% 13% 6% 11% 9% 7% 7% 6% 8% 6% 18%	1628
	11th to 20th	Day	8% 11% 3 10% 8% 9% 7% 6% 7% 8% 24%	1664
	21st to end	Day	7% 10% 4 12% 8% 8% 6% 6% 6% 7% 25%	1486
March	1st to 10th	Day	12% 12% 3 10% 11% 6% 5% 4 7% 6% 24%	3210
	11th to 20th	Day	7% 11% 5% 17% 11% 7% 5% 4 5% 6% 22%	3478
	21st to end	Day	8% 14% 6% 13% 6% 4 4 3 5% 5% 31%	3814
April	1st to 10th	Day	10% 12% 4 9% 6% 4 5% 4 5% 7% 35%	2317
	11th to 20th	Day	13% 10% 4 8% 6% 5% 4 4 6% 7% 34%	2442
	21st to end	Day	16% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	2470
May	1st to 10th	Day	19% 10% 3 6% 5% 3 4 3 5% 6% 36%	4266
	11th to 20th	Day	22% 7% 3 7% 5% 4 5% 3 5% 7% 33%	4612
	21st to end	Day	20% 9% 3 7% 5% 4 5% 4 5% 6% 34%	5173
June	1st to 10th	Day	14% 7% 2 7% 5% 5% 4 5% 6% 8% 36%	2850
	11th to 20th	Day	16% 6% 3 7% 5% 5% 5% 4 6% 8% 35%	2850
	21st to end	Day	13% 6% 3 6% 5% 5% 6% 6% 8% 7% 36%	2850
July	1st to 10th	Day	9% 4 2 5% 5% 5% 6% 5% 8% 11% 41%	4750
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 7% 10% 48%	4750
	21st to end	Day	6% 4 2 6% 5% 4 5% 4 6% 9% 50%	5099
August	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 10% 47%	4265
	11th to 20th	Day	12% 4 1 6% 5% 4 5% 4 5% 8% 46%	4041
	21st to end	Day	14% 5% 2 6% 4 4 4 3 6% 8% 45%	4532
September	1st to 10th	Day	10% 6% 2 5% 3 4 4 3 5% 9% 51%	2360
	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% 16% 4 10% 4 5% 4 2 6% 6% 26%	1535
	11th to 20th	Day	10% 15% 4 14% 6% 6% 4 3 5% 5% 27%	1520
	21st to end	Day	12% 15% 5% 12% 8% 5% 6% 3 4 5% 25%	1402
December	1st to 10th	Day	8% 15% 7% 15% 8% 6% 6% 5% 5% 5% 19%	1330
	11th to 20th	Day	10% 16% 6% 14% 7% 5% 5% 5% 6% 7% 18%	1679
	21st to end	Day	9% 14% 4 11% 7% 6% 5% 5% 7% 8% 24%	2442
January	1st to 10th	Night	5% 14% 6% 13% 7% 9% 7% 6% 6% 6% 21%	4737
	11th to 20th	Night	5% 14% 6% 16% 11% 10% 10% 6% 6% 4 13%	4709
	21st to end	Night	9% 18% 7% 14% 7% 5% 6% 4 5% 6% 19%	4874
February	1st to 10th	Night	8% 12% 5% 11% 7% 7% 9% 5% 5% 6% 26%	2551
	11th to 20th	Night	7% 9% 4 9% 6% 7% 7% 5% 7% 7% 33%	2403
	21st to end	Night	7% 11% 5% 12% 6% 7% 5% 4 5% 7% 30%	1984
March	1st to 10th	Night	11% 11% 3 12% 7% 6% 5% 4 6% 7% 29%	3650
	11th to 20th	Night	5% 10% 4 8% 6% 5% 4 4 6% 9% 40%	3480
	21st to end	Night	10% 12% 4 11% 5% 4 4 4 6% 6% 35%	3817
April	1st to 10th	Night	11% 7% 3 7% 5% 3 4 4 6% 8% 42%	1862
	11th to 20th	Night	14% 10% 3 8% 6% 4 4 4 5% 6% 36%	1689
	21st to end	Night	12% 8% 3 8% 4 6% 5% 4 5% 7% 37%	1710
May	1st to 10th	Night	18% 10% 3 6% 4 4 4 3 5% 6% 36%	2704
	11th to 20th	Night	18% 6% 2 6% 3 4 4 3 6% 6% 41%	2279
	21st to end	Night	18% 7% 2 6% 3 3 3 3 5% 6% 44%	2414
June	1st to 10th	Night	11% 6% 2 7% 4 4 4 4 8% 8% 43%	1330
	11th to 20th	Night	15% 5% 2 5% 4 5% 3 4 6% 8% 44%	1330
	21st to end	Night	10% 5% 2 5% 5% 5% 5% 5% 7% 9% 43%	1330
July	1st to 10th	Night	8% 2 1 4 4 4 5% 4 6% 10% 51%	2220
	11th to 20th	Night	6% 2 1 4 3 4 4 4 6% 11% 56%	2220
	21st to end	Night	5% 3 2 5% 4 5% 5% 4 7% 10% 51%	2462
August	1st to 10th	Night	6% 4 2 6% 4 4 4 4 7% 8% 49%	2673
	11th to 20th	Night	9% 3 1 5% 3 4 5% 4 6% 8% 52%	2798
	21st to end	Night	11% 5% 2 6% 4 4 5% 4 5% 7% 48%	3135
September	1st to 10th	Night	10% 4 2 4 4 3 5% 3 6% 8% 53%	1816
	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% 15% 5% 10% 6% 5% 5% 4 4 6% 28%	2615
	11th to 20th	Night	10% 15% 7% 12% 7% 4 5% 4 5% 6% 26%	2660
	21st to end	Night	12% 14% 5% 12% 8% 6% 5% 4 4 5% 26%	2775
December	1st to 10th	Night	6% 14% 4 14% 10% 7% 6% 4 6% 6% 22%	2850
	11th to 20th	Night	10% 16% 6% 13% 6% 5% 6% 4 5% 6% 22%	3518
	21st to end	Night	9% 11% 4 13% 9% 7% 6% 4 6% 6% 26%	5225

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% 3 13% 15% 4	2219
	11th to 20th	Day	72% 4 11% 11% 3	2220
	21st to end	Day	71% 3 8% 13% 5%	2776
February	1st to 10th	Day	63% 3 12% 14% 8% 1	1628
	11th to 20th	Day	54% 5% 12% 21% 7%	1673
	21st to end	Day	56% 5% 11% 19% 8%	1486
March	1st to 10th	Day	56% 5% 14% 20% 5%	3210
	11th to 20th	Day	62% 3 12% 18% 4	3480
	21st to end	Day	55% 5% 12% 21% 7%	3814
April	1st to 10th	Day	47% 4 12% 26% 10% 1	2317
	11th to 20th	Day	49% 3 12% 24% 11% 2	2442
	21st to end	Day	49% 4 15% 24% 7% 1	2470
May	1st to 10th	Day	47% 5% 12% 24% 11% 1	4266
	11th to 20th	Day	51% 4 11% 22% 12% 1	4616
	21st to end	Day	51% 4 12% 23% 10%	5173
June	1st to 10th	Day	46% 5% 14% 24% 11% 1	2850
	11th to 20th	Day	46% 4 15% 24% 11% 1	2850
	21st to end	Day	43% 6% 19% 24% 8% 1	2850
July	1st to 10th	Day	36% 4 25% 28% 7% 1	4676
	11th to 20th	Day	30% 3 22% 37% 7%	4669
	21st to end	Day	31% 3 22% 36% 8%	4938
August	1st to 10th	Day	34% 3 20% 33% 10%	4249
	11th to 20th	Day	37% 2 21% 34% 5%	4080
	21st to end	Day	38% 2 23% 30% 6%	4531
September	1st to 10th	Day	32% 4 18% 35% 10% 1	2360
	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	59% 3 14% 19% 4 1	1535
	11th to 20th	Day	60% 3 15% 16% 5%	1520
	21st to end	Day	62% 3 15% 15% 3	1402
December	1st to 10th	Day	66% 4 13% 13% 4	1330
	11th to 20th	Day	64% 3 16% 13% 4	1680
	21st to end	Day	59% 3 13% 20% 6%	2442
January	1st to 10th	Night	62% 4 13% 16% 5%	4737
	11th to 20th	Night	72% 3 9% 13% 2	4750
	21st to end	Night	67% 3 11% 14% 4	4874
February	1st to 10th	Night	59% 3 13% 16% 9%	2551
	11th to 20th	Night	49% 4 15% 22% 10%	2404
	21st to end	Night	53% 3 11% 22% 11%	1984
March	1st to 10th	Night	53% 5% 11% 23% 8%	3650
	11th to 20th	Night	41% 4 18% 25% 11% 1	3480
	21st to end	Night	50% 4 11% 24% 10% 1	3817
April	1st to 10th	Night	41% 3 12% 25% 17% 3	1862
	11th to 20th	Night	50% 3 7% 22% 16% 2	1689
	21st to end	Night	46% 4 11% 27% 11% 2	1710
May	1st to 10th	Night	47% 4 11% 26% 13%	2704
	11th to 20th	Night	43% 3 14% 28% 9% 4	2279
	21st to end	Night	42% 4 12% 29% 13% 1	2414
June	1st to 10th	Night	38% 6% 18% 24% 14%	1330
	11th to 20th	Night	39% 4 18% 24% 14% 2	1330
	21st to end	Night	36% 5% 20% 29% 8% 1	1330
July	1st to 10th	Night	29% 4 24% 33% 9% 1	2185
	11th to 20th	Night	24% 3 22% 41% 9% 1	2178
	21st to end	Night	29% 4 23% 37% 7% 1	2384
August	1st to 10th	Night	32% 2 16% 34% 14% 1	2665
	11th to 20th	Night	31% 3 25% 32% 10%	2825
	21st to end	Night	36% 3 19% 33% 9%	3135
September	1st to 10th	Night	31% 4 17% 34% 14% 1	1816
	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	58% 3 16% 16% 6% 1	2615
	11th to 20th	Night	60% 5% 14% 15% 6%	2660
	21st to end	Night	62% 4 14% 14% 6%	2775
December	1st to 10th	Night	62% 4 17% 14% 4	2850
	11th to 20th	Night	63% 3 15% 13% 6%	3516
	21st to end	Night	58% 3 12% 19% 8%	5225

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% 10% 34% 27% 14% 2	270
	11th to 20th	Day	11% 10% 34% 32% 11% 1	270
	21st to end	Day	19% 6% 29% 31% 13% 2	297
February	1st to 10th	Day	15% 11% 34% 33% 6% 1	270
	11th to 20th	Day	12% 16% 33% 26% 11% 1	270
	21st to end	Day	10% 9% 42% 29% 8% 1	225
March	1st to 10th	Day	16% 10% 34% 29% 9% 1	270
	11th to 20th	Day	14% 14% 33% 24% 12% 2	270
	21st to end	Day	18% 7% 35% 26% 12% 1	297
April	1st to 10th	Day	13% 11% 34% 30% 9% 3	497
	11th to 20th	Day	19% 13% 31% 25% 10% 1	640
	21st to end	Day	16% 13% 34% 26% 10% 1	650
May	1st to 10th	Day	19% 11% 34% 25% 10% 1	653
	11th to 20th	Day	21% 10% 31% 24% 11% 2	675
	21st to end	Day	21% 9% 26% 29% 13% 2	734
June	1st to 10th	Day	18% 11% 30% 22% 14% 4	680
	11th to 20th	Day	17% 13% 33% 26% 7% 4	680
	21st to end	Day	13% 8% 30% 29% 15% 5%	680
July	1st to 10th	Day	8% 7% 32% 26% 17% 9%	671
	11th to 20th	Day	11% 9% 31% 27% 18% 4	668
	21st to end	Day	7% 6% 34% 30% 15% 8%	739
August	1st to 10th	Day	10% 6% 31% 30% 18% 5%	676
	11th to 20th	Day	13% 4 26% 32% 19% 7%	665
	21st to end	Day	15% 6% 31% 29% 15% 4	748
September	1st to 10th	Day	9% 10% 34% 32% 13% 2	570
	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% 8% 28% 27% 8% 1	279
	11th to 20th	Day	17% 11% 41% 23% 7% 1	270
	21st to end	Day	21% 14% 39% 22% 4	270
December	1st to 10th	Day	14% 6% 37% 27% 13% 3	270
	11th to 20th	Day	13% 11% 40% 29% 6%	270
	21st to end	Day	13% 6% 35% 30% 14% 2	297
January	1st to 10th	Night	12% 8% 33% 31% 14% 3	950
	11th to 20th	Night	16% 6% 34% 32% 12%	950
	21st to end	Night	14% 8% 32% 33% 13% 1	1045
February	1st to 10th	Night	14% 7% 30% 34% 14% 2	950
	11th to 20th	Night	12% 7% 30% 34% 14% 3	929
	21st to end	Night	10% 7% 38% 29% 14% 2	728
March	1st to 10th	Night	14% 8% 29% 33% 14% 2	715
	11th to 20th	Night	12% 8% 39% 28% 12% 1	570
	21st to end	Night	19% 7% 28% 28% 15% 3	627
April	1st to 10th	Night	14% 8% 30% 35% 12% 2	570
	11th to 20th	Night	18% 6% 29% 33% 12% 1	563
	21st to end	Night	17% 8% 31% 34% 10%	570
May	1st to 10th	Night	19% 7% 33% 31% 9% 1	570
	11th to 20th	Night	19% 7% 31% 29% 13% 1	561
	21st to end	Night	18% 6% 34% 32% 10%	617
June	1st to 10th	Night	14% 6% 31% 34% 14% 1	570
	11th to 20th	Night	17% 6% 33% 30% 13%	570
	21st to end	Night	11% 5% 25% 39% 20% 1	570
July	1st to 10th	Night	6% 3 28% 41% 20% 2	555
	11th to 20th	Night	8% 5% 28% 40% 18% 1	552
	21st to end	Night	7% 3 27% 39% 22% 3	624
August	1st to 10th	Night	8% 2 23% 48% 17% 2	567
	11th to 20th	Night	10% 4 25% 39% 19% 4	564
	21st to end	Night	12% 5% 23% 39% 20% 1	627
September	1st to 10th	Night	11% 5% 32% 34% 16% 2	570
	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	20% 10% 34% 25% 11% 1	943
	11th to 20th	Night	18% 9% 34% 28% 9% 2	950
	21st to end	Night	19% 10% 39% 24% 7% 1	950
December	1st to 10th	Night	13% 6% 32% 34% 12% 3	950
	11th to 20th	Night	18% 7% 35% 29% 8% 2	950
	21st to end	Night	20% 8% 30% 28% 13% 2	1045

Page generated at 2024-11-01 21:47:30. Version ac07

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