Portage La Prairie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Portage La Prairie clear sky chart from 2005-11-06 to 2024-03-18.

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	11% 9% 4 7% 6% 4 5% 5% 6% 7% 36%	78120
	Night	10% 9% 5% 8% 7% 4 6% 5% 5% 7% 35%	81657
Transparency	Day	45% 8% 16% 21% 8% 1	77827
	Night	48% 8% 15% 20% 9% 1	81531
Seeing	Day	14% 9% 30% 29% 15% 4	15243
	Night	14% 7% 31% 33% 13% 1	25421

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	6% 15% 7% 11% 7% 6% 8% 5% 5% 6% 24%	2219
	11th to 20th	Day	4 10% 5% 15% 14% 8% 10% 8% 6% 6% 14%	2272
	21st to end	Day	8% 15% 6% 11% 8% 4 6% 4 6% 6% 25%	2794
February	1st to 10th	Day	8% 10% 5% 11% 10% 4 9% 7% 7% 6% 23%	1571
	11th to 20th	Day	5% 10% 5% 10% 9% 4 8% 7% 7% 7% 27%	1664
	21st to end	Day	8% 9% 4 10% 11% 5% 6% 8% 5% 7% 27%	1536
March	1st to 10th	Day	11% 11% 5% 10% 9% 4 6% 7% 6% 8% 24%	1903
	11th to 20th	Day	7% 9% 5% 9% 8% 4 6% 7% 6% 8% 29%	2055
	21st to end	Day	12% 12% 5% 8% 6% 3 6% 5% 5% 8% 30%	2178
April	1st to 10th	Day	10% 10% 4 9% 6% 3 5% 6% 6% 6% 35%	2208
	11th to 20th	Day	14% 10% 4 7% 6% 4 6% 5% 5% 7% 33%	2312
	21st to end	Day	15% 7% 3 8% 5% 3 4 5% 5% 7% 36%	2340
May	1st to 10th	Day	15% 8% 3 5% 5% 2 4 4 5% 6% 42%	2372
	11th to 20th	Day	17% 8% 2 5% 4 3 4 4 5% 7% 40%	2655
	21st to end	Day	20% 7% 2 4 5% 3 4 4 6% 7% 37%	2918
June	1st to 10th	Day	14% 5% 3 5% 6% 3 4 6% 7% 9% 39%	2700
	11th to 20th	Day	15% 6% 3 6% 6% 3 5% 5% 6% 7% 38%	2700
	21st to end	Day	12% 5% 3 5% 6% 4 5% 7% 7% 9% 37%	2700
July	1st to 10th	Day	7% 4 2 4 4 3 5% 6% 8% 9% 48%	2700
	11th to 20th	Day	11% 4 2 4 5% 3 4 5% 6% 9% 46%	2700
	21st to end	Day	8% 3 2 4 4 2 4 5% 7% 9% 53%	2855
August	1st to 10th	Day	9% 5% 2 4 5% 3 5% 5% 5% 8% 48%	2477
	11th to 20th	Day	11% 4 2 4 4 2 4 4 6% 9% 48%	2301
	21st to end	Day	13% 5% 2 5% 4 3 4 4 5% 7% 47%	2574
September	1st to 10th	Day	11% 6% 2 4 4 3 4 5% 5% 9% 48%	2220
	11th to 20th	Day	16% 6% 3 6% 5% 3 4 5% 5% 8% 41%	1980
	21st to end	Day	15% 5% 3 5% 5% 3 4 5% 6% 8% 41%	1980
October	1st to 10th	Day	17% 11% 3 6% 5% 3 4 4 6% 5% 36%	1872
	11th to 20th	Day	12% 12% 4 8% 7% 4 4 5% 4 7% 34%	1712
	21st to end	Day	16% 15% 5% 7% 6% 3 4 5% 5% 7% 27%	1782
November	1st to 10th	Day	16% 14% 5% 9% 5% 3 4 4 5% 7% 28%	1559
	11th to 20th	Day	9% 14% 8% 12% 9% 4 5% 4 3 6% 27%	1520
	21st to end	Day	12% 12% 7% 10% 9% 4 6% 5% 5% 6% 25%	1340
December	1st to 10th	Day	6% 14% 6% 12% 10% 5% 6% 5% 6% 7% 23%	1330
	11th to 20th	Day	9% 13% 9% 10% 8% 5% 6% 6% 6% 7% 20%	1679
	21st to end	Day	8% 10% 5% 11% 6% 4 4 5% 5% 7% 36%	2442
January	1st to 10th	Night	6% 13% 6% 11% 9% 6% 9% 6% 5% 6% 24%	4737
	11th to 20th	Night	5% 11% 6% 13% 13% 7% 11% 9% 5% 4 16%	4631
	21st to end	Night	8% 15% 8% 13% 7% 4 4 5% 5% 6% 24%	4873
February	1st to 10th	Night	8% 13% 4 9% 7% 4 7% 7% 6% 7% 28%	2608
	11th to 20th	Night	6% 8% 4 8% 6% 4 9% 6% 7% 8% 36%	2403
	21st to end	Night	8% 8% 5% 9% 8% 4 6% 6% 5% 7% 35%	1933
March	1st to 10th	Night	11% 10% 5% 10% 7% 3 6% 5% 5% 5% 31%	2276
	11th to 20th	Night	6% 8% 5% 6% 7% 4 5% 4 6% 7% 43%	2068
	21st to end	Night	12% 11% 4 8% 6% 3 5% 5% 5% 7% 34%	2178
April	1st to 10th	Night	9% 8% 4 5% 5% 3 5% 5% 6% 7% 43%	1750
	11th to 20th	Night	13% 10% 4 9% 7% 3 4 5% 5% 5% 35%	1599
	21st to end	Night	11% 10% 4 6% 5% 3 5% 5% 6% 7% 37%	1620
May	1st to 10th	Night	14% 8% 3 6% 4 2 4 4 6% 7% 42%	1586
	11th to 20th	Night	13% 7% 4 5% 5% 3 5% 4 6% 6% 42%	1241
	21st to end	Night	18% 6% 3 5% 4 2 3 4 5% 7% 41%	1358
June	1st to 10th	Night	14% 6% 3 6% 5% 3 5% 4 6% 7% 42%	1260
	11th to 20th	Night	13% 5% 3 5% 4 3 5% 5% 6% 8% 45%	1260
	21st to end	Night	9% 6% 2 4 5% 3 5% 5% 7% 10% 43%	1260
July	1st to 10th	Night	7% 2 1 3 3 2 5% 4 6% 8% 58%	1260
	11th to 20th	Night	6% 3 1 3 5% 2 5% 6% 7% 8% 52%	1260
	21st to end	Night	6% 3 2 4 3 2 4 5% 5% 8% 58%	1459
August	1st to 10th	Night	6% 4 1 5% 6% 3 3 5% 6% 8% 52%	1461
	11th to 20th	Night	9% 3 1 4 4 3 4 4 7% 9% 53%	1600
	21st to end	Night	11% 5% 2 4 4 2 3 4 6% 6% 54%	1782
September	1st to 10th	Night	10% 5% 2 4 3 2 4 4 5% 8% 53%	1737
	11th to 20th	Night	13% 5% 2 6% 5% 2 4 4 5% 8% 46%	1980
	21st to end	Night	14% 7% 3 6% 6% 3 4 5% 5% 7% 40%	1980
October	1st to 10th	Night	17% 8% 4 7% 6% 3 4 4 4 7% 36%	2070
	11th to 20th	Night	16% 10% 4 7% 5% 3 4 4 4 6% 37%	2245
	21st to end	Night	12% 11% 5% 8% 6% 4 5% 5% 6% 7% 31%	2574
November	1st to 10th	Night	13% 12% 5% 8% 6% 4 5% 5% 5% 6% 31%	2519
	11th to 20th	Night	10% 14% 7% 11% 6% 3 4 5% 5% 6% 28%	2660
	21st to end	Night	11% 11% 7% 12% 8% 5% 5% 4 5% 6% 27%	2836
December	1st to 10th	Night	8% 11% 6% 11% 9% 4 7% 5% 5% 7% 27%	2850
	11th to 20th	Night	10% 14% 7% 12% 8% 4 6% 5% 5% 6% 21%	3518
	21st to end	Night	8% 9% 4 9% 7% 5% 6% 5% 6% 6% 34%	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	58% 9% 16% 14% 3	2219
	11th to 20th	Day	67% 8% 12% 11% 3	2293
	21st to end	Day	56% 8% 12% 19% 5%	2794
February	1st to 10th	Day	58% 8% 13% 13% 7%	1571
	11th to 20th	Day	49% 10% 15% 19% 8%	1673
	21st to end	Day	54% 7% 14% 17% 7%	1536
March	1st to 10th	Day	56% 9% 14% 16% 5%	1903
	11th to 20th	Day	49% 10% 16% 19% 7%	2057
	21st to end	Day	52% 8% 15% 18% 8%	2178
April	1st to 10th	Day	46% 8% 16% 22% 9% 1	2208
	11th to 20th	Day	48% 8% 12% 19% 12% 2	2312
	21st to end	Day	46% 7% 18% 20% 7% 2	2340
May	1st to 10th	Day	41% 7% 14% 25% 11% 1	2372
	11th to 20th	Day	43% 7% 12% 24% 13% 1	2659
	21st to end	Day	44% 7% 14% 22% 11% 1	2918
June	1st to 10th	Day	39% 10% 19% 22% 9% 1	2700
	11th to 20th	Day	43% 8% 18% 19% 10% 1	2700
	21st to end	Day	39% 12% 21% 23% 6% 1	2700
July	1st to 10th	Day	28% 9% 22% 30% 10%	2626
	11th to 20th	Day	32% 10% 21% 28% 9%	2619
	21st to end	Day	27% 9% 22% 32% 10% 1	2696
August	1st to 10th	Day	31% 9% 21% 29% 9% 1	2461
	11th to 20th	Day	30% 10% 23% 29% 7%	2301
	21st to end	Day	36% 8% 17% 29% 10%	2574
September	1st to 10th	Day	34% 8% 19% 28% 10% 1	2220
	11th to 20th	Day	41% 9% 18% 25% 7% 1	1980
	21st to end	Day	40% 7% 19% 28% 7%	1980
October	1st to 10th	Day	48% 9% 16% 21% 7%	1872
	11th to 20th	Day	49% 7% 15% 22% 6% 1	1712
	21st to end	Day	55% 9% 17% 15% 3	1782
November	1st to 10th	Day	56% 8% 13% 17% 6% 1	1559
	11th to 20th	Day	58% 8% 16% 14% 4	1520
	21st to end	Day	60% 7% 14% 15% 4	1340
December	1st to 10th	Day	59% 9% 15% 12% 5%	1330
	11th to 20th	Day	59% 10% 14% 11% 5%	1680
	21st to end	Day	46% 7% 15% 21% 11%	2442
January	1st to 10th	Night	56% 10% 14% 17% 4	4737
	11th to 20th	Night	67% 8% 11% 11% 3	4672
	21st to end	Night	59% 8% 13% 16% 4	4873
February	1st to 10th	Night	54% 7% 15% 17% 8%	2608
	11th to 20th	Night	43% 8% 17% 20% 11%	2404
	21st to end	Night	47% 7% 14% 21% 10%	1933
March	1st to 10th	Night	53% 7% 14% 18% 7%	2276
	11th to 20th	Night	40% 6% 15% 27% 10% 1	2068
	21st to end	Night	48% 9% 16% 18% 9% 1	2178
April	1st to 10th	Night	39% 6% 13% 23% 17% 2	1750
	11th to 20th	Night	50% 6% 11% 18% 14% 2	1599
	21st to end	Night	44% 7% 15% 21% 11% 2	1620
May	1st to 10th	Night	41% 7% 14% 25% 14%	1586
	11th to 20th	Night	40% 7% 14% 22% 14% 3	1241
	21st to end	Night	42% 7% 11% 22% 16% 2	1358
June	1st to 10th	Night	40% 8% 18% 22% 12% 1	1260
	11th to 20th	Night	36% 9% 19% 23% 11% 2	1260
	21st to end	Night	33% 12% 21% 27% 6% 1	1260
July	1st to 10th	Night	21% 9% 20% 34% 14% 2	1225
	11th to 20th	Night	25% 11% 20% 29% 14% 1	1218
	21st to end	Night	23% 9% 19% 34% 13% 2	1378
August	1st to 10th	Night	28% 9% 20% 31% 12% 1	1453
	11th to 20th	Night	27% 10% 20% 31% 11% 1	1600
	21st to end	Night	29% 7% 16% 32% 14% 1	1782
September	1st to 10th	Night	30% 7% 17% 31% 15% 1	1737
	11th to 20th	Night	36% 8% 17% 26% 11% 1	1980
	21st to end	Night	42% 8% 13% 27% 9% 1	1980
October	1st to 10th	Night	47% 9% 14% 21% 9%	2070
	11th to 20th	Night	48% 7% 14% 25% 7%	2245
	21st to end	Night	50% 9% 17% 20% 5%	2574
November	1st to 10th	Night	54% 9% 15% 15% 6% 2	2519
	11th to 20th	Night	57% 9% 15% 13% 5% 1	2660
	21st to end	Night	59% 7% 15% 14% 5%	2836
December	1st to 10th	Night	57% 7% 16% 15% 5%	2850
	11th to 20th	Night	61% 7% 16% 11% 5%	3516
	21st to end	Night	47% 8% 15% 16% 12% 1	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	8% 10% 33% 34% 11% 3	270
	11th to 20th	Day	9% 9% 34% 36% 12% 1	270
	21st to end	Day	17% 7% 29% 32% 12% 2	297
February	1st to 10th	Day	12% 9% 38% 31% 7% 1	270
	11th to 20th	Day	8% 10% 39% 29% 13% 2	270
	21st to end	Day	8% 8% 39% 32% 12% 2	225
March	1st to 10th	Day	14% 10% 29% 33% 14% 1	270
	11th to 20th	Day	12% 11% 30% 32% 12% 3	261
	21st to end	Day	16% 8% 33% 28% 12% 3	264
April	1st to 10th	Day	16% 12% 34% 28% 10% 2	468
	11th to 20th	Day	16% 11% 32% 28% 12% 2	590
	21st to end	Day	15% 12% 33% 28% 10% 3	600
May	1st to 10th	Day	16% 10% 29% 29% 15% 2	603
	11th to 20th	Day	18% 10% 27% 26% 16% 4	625
	21st to end	Day	20% 10% 23% 26% 18% 3	679
June	1st to 10th	Day	14% 10% 30% 26% 14% 6%	630
	11th to 20th	Day	17% 8% 32% 28% 12% 3	630
	21st to end	Day	12% 7% 24% 31% 20% 6%	630
July	1st to 10th	Day	9% 5% 28% 33% 18% 8%	621
	11th to 20th	Day	11% 8% 27% 32% 17% 5%	618
	21st to end	Day	5% 5% 27% 32% 23% 8%	684
August	1st to 10th	Day	8% 6% 27% 30% 22% 7%	626
	11th to 20th	Day	9% 6% 23% 29% 24% 8%	615
	21st to end	Day	15% 7% 24% 30% 21% 4	693
September	1st to 10th	Day	11% 7% 35% 31% 13% 3	510
	11th to 20th	Day	17% 10% 33% 26% 12% 3	270
	21st to end	Day	19% 10% 29% 29% 12% 1	270
October	1st to 10th	Day	23% 13% 24% 26% 12% 2	270
	11th to 20th	Day	14% 11% 34% 31% 7% 1	270
	21st to end	Day	26% 10% 32% 22% 8% 2	297
November	1st to 10th	Day	23% 12% 28% 25% 11% 1	270
	11th to 20th	Day	14% 13% 36% 28% 9%	270
	21st to end	Day	16% 10% 44% 26% 4 1	270
December	1st to 10th	Day	13% 9% 37% 25% 13% 4	270
	11th to 20th	Day	14% 13% 37% 27% 8% 1	270
	21st to end	Day	13% 8% 29% 34% 14% 3	297
January	1st to 10th	Night	11% 9% 34% 32% 13% 1	950
	11th to 20th	Night	15% 8% 32% 35% 9% 1	950
	21st to end	Night	13% 9% 36% 31% 11% 1	1045
February	1st to 10th	Night	13% 8% 33% 34% 10% 1	950
	11th to 20th	Night	10% 8% 32% 36% 12% 2	929
	21st to end	Night	12% 7% 32% 33% 15% 1	677
March	1st to 10th	Night	15% 8% 30% 31% 14% 2	756
	11th to 20th	Night	10% 7% 37% 32% 13% 1	564
	21st to end	Night	17% 6% 27% 32% 15% 2	594
April	1st to 10th	Night	12% 8% 35% 32% 12% 1	540
	11th to 20th	Night	16% 6% 29% 36% 12% 1	533
	21st to end	Night	15% 6% 31% 36% 12%	540
May	1st to 10th	Night	18% 7% 28% 35% 11% 1	540
	11th to 20th	Night	16% 8% 26% 34% 15% 2	531
	21st to end	Night	19% 7% 25% 35% 13%	584
June	1st to 10th	Night	16% 7% 28% 32% 18% 1	540
	11th to 20th	Night	14% 5% 32% 33% 14% 2	540
	21st to end	Night	11% 4 25% 38% 21% 1	540
July	1st to 10th	Night	6% 3 25% 42% 22% 1	525
	11th to 20th	Night	7% 5% 27% 39% 20% 2	522
	21st to end	Night	7% 3 25% 40% 22% 3	591
August	1st to 10th	Night	6% 3 24% 45% 20% 1	537
	11th to 20th	Night	7% 4 23% 38% 23% 4	534
	21st to end	Night	12% 6% 22% 39% 20% 1	594
September	1st to 10th	Night	14% 3 27% 36% 17% 2	540
	11th to 20th	Night	14% 7% 29% 39% 11%	540
	21st to end	Night	19% 6% 32% 30% 13%	540
October	1st to 10th	Night	23% 8% 32% 29% 7%	630
	11th to 20th	Night	20% 9% 30% 30% 10%	805
	21st to end	Night	18% 11% 34% 28% 8% 1	990
November	1st to 10th	Night	19% 10% 34% 27% 9% 1	925
	11th to 20th	Night	18% 9% 36% 27% 8% 2	950
	21st to end	Night	16% 10% 41% 26% 6% 1	950
December	1st to 10th	Night	12% 9% 33% 33% 12% 2	950
	11th to 20th	Night	16% 10% 33% 31% 8% 2	950
	21st to end	Night	18% 6% 33% 30% 12% 2	1045

Page generated at 2024-03-15 13:01:45. Version ac07

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