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 2026-10-29.

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%	154472
	Night	9% 9% 4 9% 6% 5% 5% 4 6% 7% 36%	146514
Transparency	Day	42% 7% 17% 25% 9% 1	154174
	Night	46% 7% 15% 23% 9% 1	146397
Seeing	Day	14% 9% 30% 29% 14% 4	19045
	Night	14% 8% 32% 33% 12% 1	28892

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% 6% 13% 7% 9% 7% 5% 6% 8% 21%	4125
	11th to 20th	Day	4 10% 4 12% 10% 9% 10% 8% 9% 8% 17%	4276
	21st to end	Day	4 11% 5% 10% 7% 7% 7% 4 7% 8% 31%	5188
February	1st to 10th	Day	8% 11% 4 12% 9% 7% 8% 6% 7% 5% 23%	1737
	11th to 20th	Day	5% 10% 4 10% 8% 6% 8% 6% 8% 7% 28%	1844
	21st to end	Day	7% 10% 4 11% 10% 7% 6% 7% 5% 7% 25%	1694
March	1st to 10th	Day	8% 10% 4 10% 7% 5% 5% 4 6% 9% 32%	4615
	11th to 20th	Day	8% 13% 4 10% 7% 6% 6% 5% 7% 9% 27%	5088
	21st to end	Day	9% 11% 5% 12% 7% 6% 5% 3 5% 7% 29%	5585
April	1st to 10th	Day	10% 11% 4 9% 6% 4 4 4 6% 6% 35%	2578
	11th to 20th	Day	14% 11% 4 8% 5% 5% 5% 4 6% 6% 32%	2702
	21st to end	Day	14% 8% 3 8% 4 5% 5% 4 6% 7% 37%	2730
May	1st to 10th	Day	10% 7% 2 6% 4 3 4 3 6% 7% 48%	7782
	11th to 20th	Day	18% 10% 3 8% 5% 5% 5% 4 5% 6% 31%	8786
	21st to end	Day	13% 6% 2 6% 4 4 4 3 5% 7% 47%	9683
June	1st to 10th	Day	13% 6% 2 6% 5% 4 5% 5% 6% 9% 38%	3150
	11th to 20th	Day	14% 6% 3 7% 5% 4 5% 5% 6% 8% 37%	3150
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 7% 9% 36%	3150
July	1st to 10th	Day	8% 4 2 6% 4 5% 5% 5% 8% 10% 43%	8850
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 9% 45%	8850
	21st to end	Day	6% 4 2 6% 4 4 5% 4 7% 9% 50%	9314
August	1st to 10th	Day	7% 5% 2 6% 4 5% 6% 5% 7% 10% 44%	6378
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 3 6% 9% 43%	5948
	21st to end	Day	9% 5% 2 6% 4 5% 5% 4 6% 9% 47%	6593
September	1st to 10th	Day	11% 6% 2 5% 4 4 4 3 5% 9% 47%	2589
	11th to 20th	Day	17% 7% 3 7% 4 4 4 4 5% 7% 38%	2310
	21st to end	Day	14% 6% 3 6% 4 4 4 3 6% 7% 44%	2310
October	1st to 10th	Day	11% 8% 2 5% 4 4 4 3 5% 5% 49%	3496
	11th to 20th	Day	10% 9% 4 8% 5% 5% 4 4 5% 8% 39%	3179
	21st to end	Day	14% 14% 4 7% 4 3 4 4 6% 8% 32%	3262
November	1st to 10th	Day	16% 14% 4 10% 5% 4 3 4 5% 6% 29%	1726
	11th to 20th	Day	9% 15% 6% 12% 7% 5% 4 3 4 6% 28%	1680
	21st to end	Day	11% 13% 6% 13% 8% 6% 5% 3 5% 6% 25%	1480
December	1st to 10th	Day	9% 15% 6% 13% 9% 9% 6% 4 6% 6% 17%	2360
	11th to 20th	Day	9% 13% 6% 11% 6% 6% 6% 5% 7% 8% 23%	2709
	21st to end	Day	6% 10% 5% 17% 7% 5% 5% 4 5% 5% 32%	3575
January	1st to 10th	Night	6% 12% 6% 15% 8% 8% 7% 4 5% 6% 22%	8799
	11th to 20th	Night	4 12% 5% 13% 9% 8% 10% 8% 7% 5% 19%	8647
	21st to end	Night	5% 13% 6% 12% 6% 6% 7% 5% 7% 8% 27%	9026
February	1st to 10th	Night	7% 14% 4 11% 6% 7% 7% 5% 5% 7% 27%	2882
	11th to 20th	Night	6% 9% 4 7% 5% 6% 7% 4 7% 7% 36%	2663
	21st to end	Night	7% 9% 5% 10% 7% 5% 6% 5% 5% 7% 34%	2129
March	1st to 10th	Night	9% 10% 4 11% 7% 5% 6% 4 5% 7% 33%	5477
	11th to 20th	Night	6% 11% 4 8% 6% 5% 5% 4 6% 6% 39%	5090
	21st to end	Night	10% 11% 5% 11% 6% 4 4 3 5% 6% 33%	5588
April	1st to 10th	Night	9% 9% 3 6% 4 4 4 4 6% 8% 42%	2039
	11th to 20th	Night	13% 11% 3 10% 6% 5% 4 4 5% 5% 34%	1869
	21st to end	Night	12% 10% 3 6% 5% 4 5% 4 6% 7% 37%	1890
May	1st to 10th	Night	11% 8% 3 7% 4 4 4 4 6% 8% 41%	5152
	11th to 20th	Night	16% 7% 3 6% 4 4 5% 4 6% 7% 38%	4107
	21st to end	Night	14% 5% 2 6% 3 3 4 3 5% 7% 48%	4523
June	1st to 10th	Night	13% 6% 2 7% 5% 4 5% 4 6% 7% 42%	1470
	11th to 20th	Night	12% 6% 2 5% 3 4 5% 4 6% 8% 44%	1470
	21st to end	Night	11% 7% 2 5% 5% 4 5% 4 7% 9% 41%	1470
July	1st to 10th	Night	7% 3 2 5% 4 4 5% 5% 7% 8% 50%	4140
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 4 6% 9% 48%	4140
	21st to end	Night	4 3 2 5% 4 4 5% 4 6% 8% 54%	4784
August	1st to 10th	Night	6% 4 2 6% 4 4 4 4 6% 9% 51%	3791
	11th to 20th	Night	9% 4 2 5% 4 4 4 4 7% 10% 47%	4118
	21st to end	Night	9% 5% 2 5% 3 3 4 3 6% 7% 51%	4555
September	1st to 10th	Night	10% 5% 2 4 3 3 5% 3 6% 8% 51%	2028
	11th to 20th	Night	13% 5% 2 7% 5% 3 4 3 6% 8% 44%	2310
	21st to end	Night	13% 7% 3 7% 5% 3 4 4 5% 7% 43%	2310
October	1st to 10th	Night	13% 7% 3 5% 3 3 3 3 5% 7% 47%	3870
	11th to 20th	Night	11% 8% 3 7% 5% 4 4 3 5% 7% 43%	4182
	21st to end	Night	8% 9% 3 8% 5% 5% 5% 4 6% 7% 40%	4715
November	1st to 10th	Night	13% 12% 4 10% 5% 5% 4 4 5% 7% 31%	2791
	11th to 20th	Night	11% 15% 6% 11% 5% 4 4 3 5% 6% 28%	2940
	21st to end	Night	10% 13% 5% 14% 7% 6% 4 3 5% 6% 26%	3136
December	1st to 10th	Night	7% 15% 6% 16% 10% 6% 6% 4 5% 5% 19%	5050
	11th to 20th	Night	9% 13% 5% 13% 7% 6% 6% 5% 5% 6% 23%	5718
	21st to end	Night	6% 9% 4 14% 7% 7% 6% 4 6% 6% 30%	7645

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	60% 7% 12% 16% 6%	4125
	11th to 20th	Day	59% 8% 10% 15% 7%	4297
	21st to end	Day	49% 6% 14% 23% 7%	5188
February	1st to 10th	Day	58% 8% 12% 13% 8% 1	1737
	11th to 20th	Day	49% 9% 14% 20% 8%	1853
	21st to end	Day	55% 7% 14% 16% 7%	1694
March	1st to 10th	Day	46% 8% 20% 16% 10%	4615
	11th to 20th	Day	47% 11% 17% 19% 6%	5090
	21st to end	Day	50% 9% 13% 21% 7%	5585
April	1st to 10th	Day	45% 8% 15% 23% 9% 1	2578
	11th to 20th	Day	49% 8% 12% 19% 11% 1	2702
	21st to end	Day	44% 7% 17% 23% 7% 2	2730
May	1st to 10th	Day	32% 6% 13% 33% 15% 1	7782
	11th to 20th	Day	50% 7% 10% 23% 8% 1	8790
	21st to end	Day	35% 7% 10% 24% 21% 3	9683
June	1st to 10th	Day	40% 10% 18% 23% 9% 1	3150
	11th to 20th	Day	42% 8% 19% 21% 9% 1	3150
	21st to end	Day	40% 11% 20% 23% 6% 1	3150
July	1st to 10th	Day	33% 8% 27% 27% 5%	8776
	11th to 20th	Day	34% 6% 18% 35% 6% 1	8769
	21st to end	Day	28% 7% 22% 34% 9%	9112
August	1st to 10th	Day	33% 7% 22% 29% 9%	6362
	11th to 20th	Day	35% 8% 25% 28% 5%	5987
	21st to end	Day	34% 7% 22% 31% 6%	6592
September	1st to 10th	Day	34% 8% 19% 29% 9% 1	2589
	11th to 20th	Day	44% 8% 17% 24% 6% 1	2310
	21st to end	Day	39% 6% 17% 29% 9%	2310
October	1st to 10th	Day	38% 6% 14% 32% 10%	3496
	11th to 20th	Day	43% 6% 12% 29% 10%	3179
	21st to end	Day	49% 6% 15% 24% 6%	3262
November	1st to 10th	Day	56% 8% 12% 17% 6% 1	1726
	11th to 20th	Day	57% 7% 16% 14% 5% 1	1680
	21st to end	Day	60% 7% 14% 15% 4 1	1480
December	1st to 10th	Day	66% 8% 13% 10% 3	2360
	11th to 20th	Day	54% 9% 16% 14% 8%	2710
	21st to end	Day	53% 6% 11% 21% 9%	3575
January	1st to 10th	Night	60% 7% 12% 16% 5%	8800
	11th to 20th	Night	62% 7% 9% 17% 5%	8688
	21st to end	Night	53% 6% 13% 21% 7%	9026
February	1st to 10th	Night	55% 7% 14% 16% 7%	2882
	11th to 20th	Night	42% 8% 16% 22% 11%	2664
	21st to end	Night	47% 7% 14% 21% 10%	2129
March	1st to 10th	Night	48% 8% 16% 17% 9% 2	5477
	11th to 20th	Night	41% 7% 14% 24% 13%	5090
	21st to end	Night	50% 6% 11% 24% 9% 1	5588
April	1st to 10th	Night	39% 6% 13% 24% 16% 2	2039
	11th to 20th	Night	50% 6% 11% 19% 13% 2	1869
	21st to end	Night	44% 7% 14% 22% 12% 2	1890
May	1st to 10th	Night	38% 6% 12% 26% 17% 1	5152
	11th to 20th	Night	43% 7% 13% 24% 10% 2	4107
	21st to end	Night	36% 5% 10% 21% 24% 4	4526
June	1st to 10th	Night	40% 8% 17% 22% 13% 1	1470
	11th to 20th	Night	36% 9% 19% 24% 11% 2	1470
	21st to end	Night	36% 11% 20% 26% 6% 1	1470
July	1st to 10th	Night	29% 9% 25% 30% 6% 1	4105
	11th to 20th	Night	32% 6% 15% 37% 8% 1	4098
	21st to end	Night	26% 6% 21% 31% 14% 1	4681
August	1st to 10th	Night	28% 6% 20% 33% 12% 1	3783
	11th to 20th	Night	31% 7% 26% 29% 7% 1	4145
	21st to end	Night	31% 5% 21% 34% 8%	4555
September	1st to 10th	Night	31% 7% 17% 31% 13% 1	2028
	11th to 20th	Night	38% 8% 18% 25% 10% 1	2310
	21st to end	Night	40% 8% 13% 28% 11% 1	2310
October	1st to 10th	Night	37% 5% 11% 28% 17% 1	3870
	11th to 20th	Night	40% 6% 13% 28% 12% 1	4182
	21st to end	Night	42% 6% 15% 30% 6%	4715
November	1st to 10th	Night	53% 8% 15% 16% 6% 2	2791
	11th to 20th	Night	57% 9% 15% 13% 5% 1	2940
	21st to end	Night	59% 7% 15% 14% 4	3136
December	1st to 10th	Night	66% 6% 12% 12% 3	5050
	11th to 20th	Night	59% 7% 13% 12% 9%	5716
	21st to end	Night	52% 7% 13% 18% 9% 1	7645

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% 35% 33% 11% 3	330
	11th to 20th	Day	9% 9% 36% 34% 11% 1	330
	21st to end	Day	15% 9% 33% 31% 11% 2	363
February	1st to 10th	Day	12% 11% 38% 29% 8% 1	330
	11th to 20th	Day	8% 10% 36% 29% 14% 2	330
	21st to end	Day	10% 8% 37% 32% 11% 1	273
March	1st to 10th	Day	14% 10% 33% 30% 13% 1	330
	11th to 20th	Day	14% 12% 32% 29% 10% 3	330
	21st to end	Day	15% 11% 34% 26% 11% 2	363
April	1st to 10th	Day	16% 11% 32% 29% 10% 2	598
	11th to 20th	Day	17% 12% 32% 27% 11% 1	740
	21st to end	Day	15% 11% 32% 28% 11% 2	750
May	1st to 10th	Day	15% 11% 29% 29% 14% 2	753
	11th to 20th	Day	19% 11% 29% 25% 13% 3	775
	21st to end	Day	18% 10% 22% 28% 18% 4	844
June	1st to 10th	Day	14% 13% 31% 24% 13% 5%	780
	11th to 20th	Day	16% 8% 33% 28% 12% 3	780
	21st to end	Day	14% 9% 26% 29% 18% 5%	780
July	1st to 10th	Day	8% 5% 26% 32% 19% 10%	771
	11th to 20th	Day	12% 7% 27% 32% 17% 5%	768
	21st to end	Day	5% 5% 29% 32% 22% 7%	849
August	1st to 10th	Day	8% 6% 27% 31% 21% 6%	776
	11th to 20th	Day	11% 5% 23% 30% 23% 8%	765
	21st to end	Day	13% 8% 26% 30% 20% 4	858
September	1st to 10th	Day	12% 7% 33% 29% 15% 4	639
	11th to 20th	Day	18% 9% 36% 25% 11% 2	360
	21st to end	Day	16% 10% 29% 29% 14% 2	360
October	1st to 10th	Day	20% 14% 28% 26% 11% 2	360
	11th to 20th	Day	17% 14% 34% 27% 7% 1	360
	21st to end	Day	25% 10% 30% 24% 9% 2	387
November	1st to 10th	Day	23% 13% 28% 24% 11% 1	330
	11th to 20th	Day	16% 13% 35% 27% 9%	330
	21st to end	Day	15% 10% 41% 28% 5% 1	330
December	1st to 10th	Day	15% 9% 36% 25% 12% 3	330
	11th to 20th	Day	15% 15% 35% 26% 7% 1	330
	21st to end	Day	14% 10% 29% 33% 12% 3	363
January	1st to 10th	Night	11% 9% 34% 33% 13% 1	1050
	11th to 20th	Night	14% 9% 33% 34% 8% 1	1050
	21st to end	Night	12% 10% 38% 29% 10% 1	1155
February	1st to 10th	Night	13% 9% 35% 32% 10% 1	1050
	11th to 20th	Night	10% 7% 32% 37% 12% 2	1029
	21st to end	Night	11% 8% 33% 32% 14% 1	745
March	1st to 10th	Night	15% 8% 32% 30% 13% 2	836
	11th to 20th	Night	10% 8% 38% 31% 12% 1	630
	21st to end	Night	17% 6% 30% 31% 13% 2	693
April	1st to 10th	Night	12% 7% 33% 35% 11% 1	630
	11th to 20th	Night	16% 8% 30% 35% 10% 1	623
	21st to end	Night	16% 7% 30% 34% 13%	630
May	1st to 10th	Night	17% 9% 29% 35% 10% 1	630
	11th to 20th	Night	17% 9% 27% 33% 13% 1	621
	21st to end	Night	19% 7% 25% 35% 14%	683
June	1st to 10th	Night	15% 8% 30% 32% 16%	630
	11th to 20th	Night	14% 6% 31% 34% 13% 1	630
	21st to end	Night	12% 5% 26% 37% 19% 1	630
July	1st to 10th	Night	6% 4 24% 42% 23% 1	615
	11th to 20th	Night	8% 5% 25% 41% 19% 2	612
	21st to end	Night	6% 3 26% 43% 19% 3	690
August	1st to 10th	Night	7% 4 24% 44% 20% 1	627
	11th to 20th	Night	7% 4 23% 39% 23% 4	624
	21st to end	Night	12% 6% 23% 38% 20% 1	693
September	1st to 10th	Night	14% 4 27% 34% 18% 2	630
	11th to 20th	Night	13% 7% 30% 38% 11%	630
	21st to end	Night	17% 7% 32% 30% 13%	630
October	1st to 10th	Night	21% 9% 35% 29% 6%	735
	11th to 20th	Night	21% 9% 32% 29% 9%	940
	21st to end	Night	18% 11% 34% 29% 7% 1	1141
November	1st to 10th	Night	18% 10% 34% 27% 9% 1	1025
	11th to 20th	Night	19% 10% 36% 26% 7% 2	1050
	21st to end	Night	16% 10% 42% 27% 6%	1050
December	1st to 10th	Night	12% 9% 34% 32% 11% 1	1050
	11th to 20th	Night	16% 10% 35% 30% 7% 2	1050
	21st to end	Night	17% 7% 33% 30% 12% 2	1155

Page generated at 2026-10-26 02:37:52. Version ac07

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