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 2025-07-06.

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	10% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	123735
	Night	9% 10% 4 10% 6% 5% 5% 4 6% 7% 35%	123824
Transparency	Day	43% 8% 17% 23% 9% 1	123481
	Night	46% 7% 15% 22% 9% 1	123725
Seeing	Day	14% 9% 30% 29% 14% 4	17167
	Night	14% 8% 32% 33% 13% 1	27129

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	5% 13% 7% 13% 6% 8% 6% 6% 7% 9% 19%	3179
	11th to 20th	Day	4 10% 4 13% 10% 9% 8% 8% 9% 7% 18%	3274
	21st to end	Day	5% 13% 6% 12% 8% 6% 7% 3 6% 6% 27%	4004
February	1st to 10th	Day	8% 11% 4 12% 9% 7% 8% 6% 7% 5% 23%	1654
	11th to 20th	Day	5% 10% 4 10% 8% 6% 8% 6% 8% 7% 28%	1754
	21st to end	Day	8% 10% 4 11% 10% 7% 6% 6% 5% 7% 26%	1615
March	1st to 10th	Day	8% 10% 4 10% 7% 5% 5% 4 6% 9% 32%	4515
	11th to 20th	Day	7% 13% 4 9% 7% 6% 6% 5% 7% 9% 27%	4978
	21st to end	Day	9% 11% 5% 12% 7% 6% 5% 3 4 7% 29%	5464
April	1st to 10th	Day	10% 11% 4 9% 6% 4 4 4 6% 6% 36%	2456
	11th to 20th	Day	14% 10% 4 8% 5% 5% 5% 4 6% 6% 33%	2572
	21st to end	Day	15% 8% 3 8% 4 5% 4 4 5% 7% 37%	2600
May	1st to 10th	Day	13% 7% 2 6% 4 3 4 3 6% 7% 47%	6014
	11th to 20th	Day	19% 9% 3 7% 5% 5% 5% 4 5% 7% 30%	6755
	21st to end	Day	14% 6% 2 5% 3 3 3 3 5% 6% 49%	7428
June	1st to 10th	Day	14% 6% 2 6% 5% 4 5% 4 6% 9% 38%	3000
	11th to 20th	Day	14% 6% 3 7% 5% 4 5% 5% 6% 8% 38%	3000
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 9% 36%	3000
July	1st to 10th	Day	9% 4 2 5% 4 5% 5% 5% 8% 11% 43%	4826
	11th to 20th	Day	8% 4 2 4 4 4 4 4 6% 9% 53%	4750
	21st to end	Day	6% 3 2 5% 4 4 5% 4 8% 9% 51%	4999
August	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 7% 9% 45%	4356
	11th to 20th	Day	11% 5% 2 5% 3 4 5% 3 6% 9% 47%	4041
	21st to end	Day	11% 5% 2 6% 4 4 4 4 5% 8% 47%	4532
September	1st to 10th	Day	11% 6% 2 5% 3 4 4 3 5% 9% 49%	2342
	11th to 20th	Day	15% 6% 3 6% 4 4 4 4 5% 8% 41%	2090
	21st to end	Day	15% 6% 3 6% 4 4 4 4 6% 7% 42%	2090
October	1st to 10th	Day	12% 8% 2 5% 4 4 4 3 5% 5% 48%	3288
	11th to 20th	Day	9% 9% 4 8% 5% 5% 5% 4 5% 8% 39%	2989
	21st to end	Day	14% 14% 4 7% 4 3 4 4 6% 8% 32%	3091
November	1st to 10th	Day	16% 14% 4 10% 5% 4 3 4 5% 6% 29%	1642
	11th to 20th	Day	9% 16% 7% 13% 7% 5% 4 3 4 6% 27%	1600
	21st to end	Day	12% 13% 6% 12% 8% 6% 5% 3 5% 6% 24%	1410
December	1st to 10th	Day	9% 15% 6% 13% 10% 9% 6% 4 7% 6% 17%	2290
	11th to 20th	Day	9% 13% 6% 10% 6% 6% 6% 5% 7% 8% 24%	2639
	21st to end	Day	6% 10% 5% 17% 7% 5% 5% 3 5% 5% 32%	3498
January	1st to 10th	Night	4 12% 6% 15% 9% 9% 7% 5% 6% 6% 22%	6787
	11th to 20th	Night	4 12% 5% 13% 9% 8% 10% 8% 7% 5% 19%	6639
	21st to end	Night	7% 16% 7% 14% 6% 5% 5% 4 5% 7% 24%	6974
February	1st to 10th	Night	7% 14% 4 10% 6% 6% 7% 6% 6% 7% 27%	2745
	11th to 20th	Night	5% 8% 4 7% 6% 6% 7% 5% 8% 8% 36%	2533
	21st to end	Night	8% 9% 5% 10% 6% 5% 6% 5% 5% 7% 35%	2031
March	1st to 10th	Night	9% 10% 4 11% 7% 5% 6% 4 5% 7% 33%	5357
	11th to 20th	Night	6% 11% 4 8% 6% 5% 5% 4 6% 6% 39%	4980
	21st to end	Night	10% 11% 5% 11% 6% 4 5% 3 5% 6% 34%	5467
April	1st to 10th	Night	9% 9% 3 6% 4 5% 5% 4 6% 8% 42%	1942
	11th to 20th	Night	14% 11% 3 10% 6% 5% 4 4 5% 5% 34%	1779
	21st to end	Night	12% 10% 4 6% 5% 4 5% 4 6% 7% 37%	1800
May	1st to 10th	Night	13% 9% 3 7% 4 4 4 3 5% 6% 41%	3964
	11th to 20th	Night	16% 7% 3 6% 4 4 5% 4 7% 8% 35%	3161
	21st to end	Night	14% 5% 2 5% 3 3 3 3 5% 7% 50%	3470
June	1st to 10th	Night	13% 6% 2 7% 5% 4 5% 4 6% 7% 42%	1400
	11th to 20th	Night	12% 6% 2 5% 3 3 5% 4 6% 8% 45%	1400
	21st to end	Night	10% 7% 2 5% 5% 4 5% 4 7% 10% 42%	1400
July	1st to 10th	Night	9% 3 1 4 3 4 5% 4 6% 9% 53%	2255
	11th to 20th	Night	7% 3 1 4 3 4 5% 4 7% 8% 55%	2220
	21st to end	Night	4 3 1 4 3 4 5% 4 7% 9% 54%	2561
August	1st to 10th	Night	6% 4 2 6% 5% 4 4 4 7% 8% 49%	2583
	11th to 20th	Night	8% 3 1 5% 3 4 4 4 7% 10% 50%	2798
	21st to end	Night	10% 5% 2 5% 3 3 3 3 6% 7% 52%	3135
September	1st to 10th	Night	10% 5% 2 4 3 3 4 3 6% 8% 53%	1835
	11th to 20th	Night	12% 5% 2 7% 4 3 4 4 6% 7% 46%	2090
	21st to end	Night	14% 8% 3 7% 5% 4 4 4 5% 7% 41%	2090
October	1st to 10th	Night	13% 7% 3 6% 3 3 3 3 5% 7% 46%	3640
	11th to 20th	Night	10% 8% 3 7% 4 4 4 3 5% 8% 43%	3932
	21st to end	Night	7% 9% 3 8% 5% 5% 5% 4 6% 7% 40%	4467
November	1st to 10th	Night	13% 12% 4 10% 6% 5% 4 4 5% 6% 31%	2655
	11th to 20th	Night	11% 16% 7% 11% 5% 4 4 3 5% 6% 27%	2800
	21st to end	Night	10% 13% 6% 14% 7% 6% 4 3 5% 5% 26%	2986
December	1st to 10th	Night	8% 15% 6% 17% 11% 6% 6% 4 5% 5% 19%	4900
	11th to 20th	Night	9% 13% 5% 13% 7% 6% 6% 5% 5% 6% 23%	5568
	21st to end	Night	6% 9% 4 14% 7% 7% 6% 4 6% 6% 30%	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	58% 8% 13% 16% 4	3179
	11th to 20th	Day	58% 9% 9% 16% 8%	3295
	21st to end	Day	55% 7% 17% 18% 3	4004
February	1st to 10th	Day	58% 8% 12% 13% 8% 1	1654
	11th to 20th	Day	48% 9% 15% 19% 8%	1763
	21st to end	Day	54% 7% 14% 17% 7%	1615
March	1st to 10th	Day	45% 8% 20% 16% 10%	4515
	11th to 20th	Day	47% 11% 18% 19% 6%	4980
	21st to end	Day	50% 9% 13% 21% 6%	5464
April	1st to 10th	Day	45% 8% 15% 23% 9% 1	2456
	11th to 20th	Day	48% 8% 12% 20% 11% 1	2572
	21st to end	Day	45% 7% 17% 22% 7% 2	2600
May	1st to 10th	Day	35% 6% 14% 27% 16% 2	6014
	11th to 20th	Day	50% 8% 11% 22% 8% 1	6759
	21st to end	Day	34% 7% 10% 23% 22% 4	7428
June	1st to 10th	Day	39% 10% 18% 23% 9% 1	3000
	11th to 20th	Day	42% 8% 19% 20% 10% 1	3000
	21st to end	Day	39% 11% 20% 23% 6% 1	3000
July	1st to 10th	Day	31% 10% 27% 26% 6%	4752
	11th to 20th	Day	26% 8% 23% 37% 6%	4669
	21st to end	Day	27% 7% 25% 33% 7%	4841
August	1st to 10th	Day	33% 8% 21% 29% 10%	4340
	11th to 20th	Day	32% 8% 21% 32% 6%	4080
	21st to end	Day	34% 7% 23% 29% 7%	4531
September	1st to 10th	Day	32% 8% 19% 29% 10% 1	2342
	11th to 20th	Day	41% 8% 18% 25% 7% 1	2090
	21st to end	Day	39% 6% 19% 28% 8%	2090
October	1st to 10th	Day	38% 6% 14% 32% 10%	3288
	11th to 20th	Day	42% 6% 12% 29% 9%	2989
	21st to end	Day	49% 6% 15% 24% 6%	3091
November	1st to 10th	Day	56% 8% 13% 17% 6% 1	1642
	11th to 20th	Day	58% 8% 15% 14% 4	1600
	21st to end	Day	61% 7% 14% 15% 4	1410
December	1st to 10th	Day	67% 8% 13% 9% 3	2290
	11th to 20th	Day	53% 9% 16% 14% 8%	2640
	21st to end	Day	53% 6% 11% 21% 9%	3498
January	1st to 10th	Night	59% 8% 11% 17% 5%	6787
	11th to 20th	Night	62% 8% 9% 16% 5%	6680
	21st to end	Night	59% 7% 14% 16% 4	6974
February	1st to 10th	Night	54% 7% 14% 16% 8%	2745
	11th to 20th	Night	42% 8% 17% 22% 11%	2534
	21st to end	Night	47% 7% 14% 21% 10%	2031
March	1st to 10th	Night	47% 8% 16% 17% 9% 2	5357
	11th to 20th	Night	41% 7% 14% 24% 13%	4980
	21st to end	Night	49% 6% 11% 24% 9% 1	5467
April	1st to 10th	Night	39% 6% 13% 24% 16% 2	1942
	11th to 20th	Night	50% 6% 10% 19% 13% 2	1779
	21st to end	Night	44% 7% 14% 21% 12% 2	1800
May	1st to 10th	Night	41% 7% 12% 21% 18% 1	3964
	11th to 20th	Night	44% 8% 14% 22% 9% 3	3161
	21st to end	Night	33% 6% 11% 22% 22% 6%	3470
June	1st to 10th	Night	40% 8% 17% 22% 13% 1	1400
	11th to 20th	Night	36% 9% 19% 23% 11% 2	1400
	21st to end	Night	35% 11% 21% 26% 7% 1	1400
July	1st to 10th	Night	26% 9% 28% 28% 8% 1	2220
	11th to 20th	Night	25% 8% 20% 38% 9% 1	2178
	21st to end	Night	24% 7% 24% 33% 11% 1	2480
August	1st to 10th	Night	30% 7% 18% 30% 13% 1	2575
	11th to 20th	Night	27% 7% 25% 30% 10% 1	2825
	21st to end	Night	30% 6% 21% 33% 9% 1	3135
September	1st to 10th	Night	29% 7% 16% 32% 14% 1	1835
	11th to 20th	Night	36% 8% 18% 26% 10% 1	2090
	21st to end	Night	41% 8% 13% 27% 9% 1	2090
October	1st to 10th	Night	38% 5% 11% 28% 17% 1	3640
	11th to 20th	Night	39% 6% 14% 29% 12%	3932
	21st to end	Night	42% 6% 15% 31% 6%	4467
November	1st to 10th	Night	53% 8% 15% 16% 6% 2	2655
	11th to 20th	Night	58% 9% 15% 13% 5% 1	2800
	21st to end	Night	59% 7% 15% 14% 4	2986
December	1st to 10th	Night	67% 6% 12% 11% 3	4900
	11th to 20th	Night	59% 7% 13% 12% 9%	5566
	21st to end	Night	52% 7% 13% 18% 9% 1	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	7% 9% 34% 34% 12% 3	300
	11th to 20th	Day	9% 9% 34% 35% 12% 1	300
	21st to end	Day	16% 8% 32% 31% 11% 2	330
February	1st to 10th	Day	12% 10% 39% 30% 8% 1	300
	11th to 20th	Day	7% 9% 38% 30% 14% 2	300
	21st to end	Day	9% 8% 38% 32% 11% 2	249
March	1st to 10th	Day	13% 10% 30% 32% 14% 1	300
	11th to 20th	Day	14% 11% 31% 31% 11% 3	300
	21st to end	Day	14% 9% 34% 28% 12% 3	330
April	1st to 10th	Day	16% 12% 31% 29% 10% 2	556
	11th to 20th	Day	16% 12% 32% 28% 10% 1	690
	21st to end	Day	16% 11% 32% 28% 11% 2	700
May	1st to 10th	Day	15% 11% 29% 28% 14% 3	703
	11th to 20th	Day	18% 11% 28% 26% 14% 3	725
	21st to end	Day	19% 10% 22% 27% 18% 4	789
June	1st to 10th	Day	14% 12% 30% 25% 13% 5%	730
	11th to 20th	Day	16% 8% 33% 28% 12% 3	730
	21st to end	Day	12% 8% 27% 29% 18% 5%	730
July	1st to 10th	Day	9% 4 27% 32% 18% 10%	697
	11th to 20th	Day	11% 7% 26% 32% 18% 6%	668
	21st to end	Day	6% 5% 28% 32% 22% 8%	739
August	1st to 10th	Day	8% 6% 27% 31% 21% 7%	676
	11th to 20th	Day	11% 6% 22% 29% 24% 9%	665
	21st to end	Day	14% 8% 25% 29% 20% 4	748
September	1st to 10th	Day	10% 7% 35% 31% 14% 3	552
	11th to 20th	Day	16% 10% 34% 26% 12% 2	300
	21st to end	Day	18% 11% 29% 29% 12% 1	300
October	1st to 10th	Day	22% 13% 25% 26% 12% 2	300
	11th to 20th	Day	14% 13% 35% 30% 7% 1	300
	21st to end	Day	25% 10% 32% 24% 8% 2	330
November	1st to 10th	Day	22% 12% 28% 25% 12% 1	300
	11th to 20th	Day	16% 13% 35% 27% 9%	300
	21st to end	Day	15% 9% 42% 28% 4 1	300
December	1st to 10th	Day	14% 9% 37% 25% 12% 3	300
	11th to 20th	Day	14% 13% 36% 28% 8% 1	300
	21st to end	Day	12% 8% 29% 34% 13% 3	330
January	1st to 10th	Night	11% 9% 35% 33% 13% 1	1000
	11th to 20th	Night	15% 8% 33% 35% 9% 1	1000
	21st to end	Night	13% 10% 36% 30% 10% 1	1100
February	1st to 10th	Night	13% 8% 34% 33% 10% 1	1000
	11th to 20th	Night	9% 7% 32% 37% 12% 2	979
	21st to end	Night	11% 8% 33% 32% 14% 1	711
March	1st to 10th	Night	15% 8% 31% 31% 14% 2	796
	11th to 20th	Night	10% 8% 37% 32% 13% 1	600
	21st to end	Night	17% 6% 29% 32% 14% 2	660
April	1st to 10th	Night	12% 7% 34% 34% 12% 1	600
	11th to 20th	Night	17% 7% 30% 35% 11% 1	593
	21st to end	Night	16% 6% 30% 35% 12%	600
May	1st to 10th	Night	17% 9% 29% 34% 11% 1	600
	11th to 20th	Night	16% 9% 27% 33% 13% 1	591
	21st to end	Night	18% 7% 25% 34% 15%	650
June	1st to 10th	Night	15% 8% 30% 31% 16% 1	600
	11th to 20th	Night	15% 6% 31% 34% 13% 2	600
	21st to end	Night	12% 5% 26% 38% 19% 1	600
July	1st to 10th	Night	6% 3 25% 42% 23% 1	570
	11th to 20th	Night	7% 5% 26% 39% 21% 2	552
	21st to end	Night	7% 3 26% 41% 21% 3	624
August	1st to 10th	Night	7% 4 24% 44% 20% 2	567
	11th to 20th	Night	7% 4 23% 38% 24% 4	564
	21st to end	Night	12% 6% 23% 38% 20% 1	627
September	1st to 10th	Night	14% 2 28% 36% 17% 2	570
	11th to 20th	Night	13% 7% 30% 38% 11%	570
	21st to end	Night	18% 7% 34% 29% 13%	570
October	1st to 10th	Night	22% 8% 33% 29% 7%	665
	11th to 20th	Night	19% 9% 31% 30% 10%	850
	21st to end	Night	17% 11% 34% 29% 8% 1	1045
November	1st to 10th	Night	19% 9% 34% 27% 10% 1	975
	11th to 20th	Night	19% 9% 36% 26% 8% 2	1000
	21st to end	Night	16% 9% 41% 26% 6% 1	1000
December	1st to 10th	Night	13% 9% 33% 32% 12% 2	1000
	11th to 20th	Night	16% 10% 34% 31% 8% 2	1000
	21st to end	Night	17% 6% 32% 30% 13% 2	1100

Page generated at 2025-07-03 00:30:12. Version ac07

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