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 2024-11-03.

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 8% 5% 5% 5% 4 6% 8% 37%	101860
	Night	10% 10% 4 9% 6% 5% 5% 4 6% 7% 36%	97263
Transparency	Day	43% 8% 18% 23% 7%	101606
	Night	45% 8% 16% 21% 8% 1	97164
Seeing	Day	14% 9% 30% 29% 14% 4	16245
	Night	14% 7% 31% 33% 13% 1	26155

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% 16% 6% 12% 6% 9% 6% 4 5% 6% 24%	2219
	11th to 20th	Day	4 11% 5% 17% 12% 11% 9% 6% 6% 6% 14%	2272
	21st to end	Day	7% 16% 5% 12% 7% 5% 6% 3 6% 6% 25%	2794
February	1st to 10th	Day	8% 11% 5% 12% 9% 6% 8% 5% 7% 5% 23%	1571
	11th to 20th	Day	5% 10% 4 10% 8% 6% 7% 6% 7% 7% 27%	1664
	21st to end	Day	8% 10% 4 11% 10% 6% 5% 6% 5% 7% 26%	1536
March	1st to 10th	Day	11% 11% 3 9% 8% 5% 6% 4 6% 8% 29%	3145
	11th to 20th	Day	7% 11% 4 10% 8% 6% 6% 5% 6% 9% 28%	3478
	21st to end	Day	8% 11% 6% 13% 6% 5% 5% 3 5% 7% 32%	3814
April	1st to 10th	Day	10% 11% 4 9% 6% 4 4 4 6% 6% 35%	2332
	11th to 20th	Day	14% 11% 4 8% 5% 5% 5% 4 6% 6% 33%	2442
	21st to end	Day	15% 8% 3 9% 4 4 4 4 5% 7% 37%	2470
May	1st to 10th	Day	18% 10% 3 7% 4 3 4 3 5% 6% 38%	4193
	11th to 20th	Day	19% 9% 3 7% 4 5% 5% 4 5% 6% 33%	4705
	21st to end	Day	20% 7% 2 6% 4 4 4 4 6% 7% 37%	5173
June	1st to 10th	Day	14% 6% 2 6% 6% 4 5% 5% 6% 9% 38%	2850
	11th to 20th	Day	15% 6% 3 7% 5% 4 5% 4 6% 7% 38%	2850
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 9% 36%	2850
July	1st to 10th	Day	9% 4 2 5% 4 5% 5% 5% 8% 11% 43%	4750
	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	17% 11% 3 6% 4 5% 4 3 5% 5% 38%	1976
	11th to 20th	Day	11% 12% 4 9% 5% 5% 4 4 4 7% 34%	1807
	21st to end	Day	15% 15% 4 8% 5% 4 4 4 6% 7% 27%	1881
November	1st to 10th	Day	16% 15% 4 10% 5% 4 3 4 5% 6% 29%	1577
	11th to 20th	Day	9% 16% 7% 13% 7% 5% 4 3 4 6% 27%	1520
	21st to end	Day	12% 13% 6% 11% 8% 6% 5% 3 5% 6% 25%	1340
December	1st to 10th	Day	6% 15% 5% 14% 9% 7% 5% 4 7% 6% 22%	1330
	11th to 20th	Day	9% 15% 7% 12% 6% 7% 6% 5% 6% 7% 20%	1679
	21st to end	Day	7% 11% 4 12% 5% 4 5% 4 5% 7% 36%	2442
January	1st to 10th	Night	6% 13% 6% 12% 7% 8% 8% 5% 5% 6% 24%	4737
	11th to 20th	Night	5% 12% 6% 16% 11% 9% 10% 7% 5% 4 16%	4631
	21st to end	Night	8% 16% 8% 14% 6% 5% 4 4 5% 6% 24%	4873
February	1st to 10th	Night	8% 14% 4 11% 6% 6% 6% 6% 6% 7% 28%	2608
	11th to 20th	Night	6% 9% 4 8% 6% 7% 7% 4 7% 7% 35%	2403
	21st to end	Night	8% 9% 5% 10% 6% 5% 6% 5% 5% 7% 35%	1933
March	1st to 10th	Night	11% 10% 3 12% 8% 4 6% 4 4 6% 32%	3717
	11th to 20th	Night	5% 10% 4 8% 6% 5% 4 4 6% 7% 43%	3480
	21st to end	Night	8% 11% 5% 11% 7% 5% 5% 3 6% 7% 34%	3817
April	1st to 10th	Night	8% 9% 3 5% 4 5% 5% 5% 6% 8% 42%	1846
	11th to 20th	Night	14% 11% 3 10% 6% 5% 4 4 5% 5% 34%	1689
	21st to end	Night	12% 10% 4 6% 5% 4 5% 4 7% 7% 37%	1710
May	1st to 10th	Night	17% 10% 3 6% 4 4 5% 4 6% 7% 35%	2775
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 4 6% 6% 42%	2201
	21st to end	Night	19% 6% 2 6% 3 3 3 3 5% 7% 44%	2414
June	1st to 10th	Night	13% 6% 2 7% 5% 4 4 3 6% 7% 42%	1330
	11th to 20th	Night	13% 6% 2 5% 3 4 5% 4 6% 8% 44%	1330
	21st to end	Night	10% 7% 2 5% 5% 4 5% 4 7% 10% 42%	1330
July	1st to 10th	Night	9% 3 1 3 3 4 5% 4 6% 9% 52%	2220
	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	16% 8% 3 7% 5% 4 4 3 5% 7% 37%	2185
	11th to 20th	Night	15% 10% 3 8% 5% 4 4 3 4 6% 38%	2370
	21st to end	Night	11% 12% 4 9% 5% 5% 5% 4 6% 7% 32%	2717
November	1st to 10th	Night	13% 13% 4 9% 6% 5% 4 3 5% 6% 31%	2546
	11th to 20th	Night	10% 16% 6% 12% 5% 4 4 3 5% 6% 28%	2660
	21st to end	Night	11% 13% 6% 14% 7% 6% 4 3 5% 6% 26%	2836
December	1st to 10th	Night	7% 13% 5% 13% 8% 5% 6% 4 5% 6% 27%	2850
	11th to 20th	Night	10% 15% 6% 14% 6% 6% 6% 4 5% 6% 21%	3518
	21st to end	Night	8% 10% 4 11% 6% 6% 6% 4 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	49% 9% 18% 20% 4	3145
	11th to 20th	Day	45% 13% 17% 17% 7%	3480
	21st to end	Day	49% 8% 16% 20% 8%	3814
April	1st to 10th	Day	45% 8% 15% 23% 8% 1	2332
	11th to 20th	Day	48% 8% 12% 19% 11% 1	2442
	21st to end	Day	45% 7% 17% 22% 7% 2	2470
May	1st to 10th	Day	43% 7% 14% 25% 9% 1	4193
	11th to 20th	Day	47% 10% 11% 21% 10% 1	4709
	21st to end	Day	43% 9% 14% 24% 9% 1	5173
June	1st to 10th	Day	40% 10% 19% 21% 9% 1	2850
	11th to 20th	Day	43% 8% 18% 20% 10% 1	2850
	21st to end	Day	39% 11% 20% 23% 6% 1	2850
July	1st to 10th	Day	31% 10% 28% 26% 6%	4676
	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	47% 8% 15% 23% 7%	1976
	11th to 20th	Day	48% 7% 15% 23% 6% 1	1807
	21st to end	Day	55% 9% 17% 16% 4	1881
November	1st to 10th	Day	56% 8% 13% 17% 6% 1	1577
	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	50% 9% 15% 20% 6%	3717
	11th to 20th	Night	36% 8% 17% 25% 13% 1	3480
	21st to end	Night	47% 8% 13% 24% 8% 1	3817
April	1st to 10th	Night	38% 6% 13% 24% 16% 2	1846
	11th to 20th	Night	50% 6% 11% 18% 14% 2	1689
	21st to end	Night	43% 8% 15% 21% 11% 2	1710
May	1st to 10th	Night	44% 9% 14% 23% 11%	2775
	11th to 20th	Night	39% 9% 15% 23% 10% 4	2201
	21st to end	Night	39% 7% 15% 26% 11% 1	2414
June	1st to 10th	Night	40% 8% 17% 22% 13% 1	1330
	11th to 20th	Night	36% 9% 18% 23% 11% 2	1330
	21st to end	Night	34% 12% 21% 26% 6% 1	1330
July	1st to 10th	Night	26% 9% 28% 28% 8% 1	2185
	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	46% 8% 14% 22% 10%	2185
	11th to 20th	Night	47% 7% 14% 25% 7%	2370
	21st to end	Night	50% 8% 16% 21% 4	2717
November	1st to 10th	Night	54% 9% 15% 16% 6% 2	2546
	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	13% 11% 29% 31% 12% 3	270
	21st to end	Day	14% 8% 33% 30% 11% 3	297
April	1st to 10th	Day	15% 11% 32% 30% 10% 2	512
	11th to 20th	Day	17% 11% 32% 28% 11% 2	640
	21st to end	Day	15% 11% 32% 28% 11% 2	650
May	1st to 10th	Day	16% 10% 29% 28% 14% 2	653
	11th to 20th	Day	17% 11% 28% 26% 15% 3	675
	21st to end	Day	20% 11% 23% 26% 17% 3	734
June	1st to 10th	Day	14% 12% 30% 25% 13% 6%	680
	11th to 20th	Day	17% 8% 32% 28% 11% 3	680
	21st to end	Day	12% 8% 25% 30% 19% 5%	680
July	1st to 10th	Day	9% 4 27% 32% 18% 10%	671
	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% 26% 11% 1	276
	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% 8% 37% 31% 13% 1	570
	21st to end	Night	17% 6% 29% 33% 14% 2	627
April	1st to 10th	Night	11% 7% 34% 34% 12% 1	570
	11th to 20th	Night	17% 7% 29% 35% 11% 1	563
	21st to end	Night	15% 6% 31% 35% 12%	570
May	1st to 10th	Night	18% 8% 28% 34% 11% 1	570
	11th to 20th	Night	16% 9% 27% 34% 14% 1	561
	21st to end	Night	19% 7% 26% 34% 13%	617
June	1st to 10th	Night	15% 7% 29% 32% 17% 1	570
	11th to 20th	Night	15% 6% 32% 32% 14% 2	570
	21st to end	Night	11% 4 25% 38% 20% 1	570
July	1st to 10th	Night	6% 3 25% 42% 24% 1	555
	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% 10% 34% 27% 9% 1	936
	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

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