Porteau Cove Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Porteau Cove Provincial Park clear sky chart from 2005-11-06 to 2026-04-02.

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	23% 11% 3 7% 4 4 4 3 4 5% 32%	135002
	Night	27% 13% 3 6% 4 3 3 3 4 5% 30%	135528
Transparency	Day	56% 7% 12% 15% 8% 1	134707
	Night	59% 6% 11% 14% 9% 2	135401
Seeing	Day	27% 13% 25% 23% 10% 2	17137
	Night	33% 7% 21% 23% 14% 1	25441

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	34% 22% 4 7% 4 3 3 3 4 4 12%	4125
	11th to 20th	Day	19% 8% 4 6% 3 3 3 2 5% 5% 42%	4119
	21st to end	Day	40% 11% 2 4 3 3 3 2 3 3 27%	5096
February	1st to 10th	Day	30% 15% 4 8% 4 3 3 3 5% 6% 18%	1890
	11th to 20th	Day	25% 19% 4 8% 4 3 2 2 4 6% 24%	1845
	21st to end	Day	21% 20% 5% 9% 6% 4 4 3 4 3 19%	1559
March	1st to 10th	Day	25% 19% 4 10% 6% 4 4 2 4 4 19%	4793
	11th to 20th	Day	23% 19% 4 8% 5% 4 3 2 4 4 24%	5110
	21st to end	Day	28% 18% 4 10% 6% 5% 4 3 4 4 14%	5736
April	1st to 10th	Day	27% 17% 4 9% 6% 5% 4 3 5% 5% 15%	2413
	11th to 20th	Day	23% 14% 3 10% 6% 5% 4 3 4 5% 23%	2491
	21st to end	Day	27% 13% 3 7% 5% 5% 5% 4 5% 4 22%	2656
May	1st to 10th	Day	15% 11% 3 7% 4 4 4 3 4 5% 40%	6320
	11th to 20th	Day	19% 10% 3 8% 5% 4 4 4 7% 9% 26%	6277
	21st to end	Day	24% 9% 3 7% 5% 5% 5% 4 6% 7% 23%	7133
June	1st to 10th	Day	26% 10% 3 7% 5% 4 4 3 5% 6% 27%	3000
	11th to 20th	Day	24% 12% 4 10% 6% 6% 5% 3 4 5% 21%	3000
	21st to end	Day	20% 9% 3 7% 5% 5% 4 3 5% 6% 33%	3000
July	1st to 10th	Day	10% 5% 1 4 3 2 3 3 4 5% 59%	6780
	11th to 20th	Day	5% 3 1 3 2 2 2 2 4 6% 69%	6780
	21st to end	Day	11% 5% 1 4 3 3 3 3 5% 7% 57%	7085
August	1st to 10th	Day	7% 4 1 4 2 2 2 2 4 7% 64%	4496
	11th to 20th	Day	16% 8% 3 7% 4 4 3 3 4 5% 42%	4156
	21st to end	Day	18% 7% 2 6% 3 3 4 3 6% 7% 41%	4580
September	1st to 10th	Day	14% 6% 2 5% 4 5% 4 3 5% 6% 47%	2400
	11th to 20th	Day	21% 8% 3 6% 3 4 4 3 4 5% 39%	2385
	21st to end	Day	27% 7% 2 6% 4 4 4 3 3 6% 33%	2112
October	1st to 10th	Day	27% 9% 3 7% 4 5% 4 3 4 6% 28%	3280
	11th to 20th	Day	36% 9% 2 7% 4 4 4 4 4 6% 21%	3261
	21st to end	Day	32% 12% 4 9% 4 4 5% 4 5% 6% 16%	3251
November	1st to 10th	Day	41% 10% 3 7% 5% 4 3 3 4 3 17%	1648
	11th to 20th	Day	40% 16% 3 6% 2 2 3 2 3 3 20%	1680
	21st to end	Day	37% 15% 3 6% 4 4 4 2 2 4 19%	1680
December	1st to 10th	Day	26% 13% 3 6% 4 4 3 3 4 4 31%	2575
	11th to 20th	Day	44% 15% 4 7% 4 2 2 2 3 3 13%	2715
	21st to end	Day	39% 18% 4 9% 5% 3 4 2 2 3 10%	3575
January	1st to 10th	Night	33% 19% 5% 9% 5% 4 3 2 3 3 14%	8770
	11th to 20th	Night	23% 8% 2 4 3 3 3 3 4 8% 40%	8779
	21st to end	Night	35% 11% 2 5% 3 3 2 2 3 4 30%	9084
February	1st to 10th	Night	31% 13% 4 8% 5% 4 4 3 4 4 20%	2730
	11th to 20th	Night	24% 18% 4 7% 5% 4 3 2 3 4 25%	2662
	21st to end	Night	29% 18% 3 7% 4 4 3 3 3 4 23%	2246
March	1st to 10th	Night	25% 19% 5% 8% 5% 4 3 3 5% 4 21%	5319
	11th to 20th	Night	24% 21% 4 8% 4 3 3 2 4 4 24%	5109
	21st to end	Night	33% 18% 4 8% 5% 3 3 2 4 3 17%	5481
April	1st to 10th	Night	28% 15% 4 8% 6% 5% 4 3 4 5% 19%	2010
	11th to 20th	Night	22% 15% 3 6% 5% 4 4 3 4 6% 28%	1856
	21st to end	Night	26% 13% 3 7% 4 3 4 3 5% 5% 27%	1742
May	1st to 10th	Night	17% 10% 3 5% 3 3 3 2 4 4 46%	3640
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 3 6% 8% 32%	3616
	21st to end	Night	21% 14% 4 8% 6% 4 4 3 4 6% 26%	3725
June	1st to 10th	Night	24% 9% 3 7% 4 4 3 3 5% 5% 32%	1400
	11th to 20th	Night	20% 13% 4 8% 5% 5% 5% 3 5% 5% 27%	1400
	21st to end	Night	16% 9% 3 7% 4 4 4 3 5% 7% 37%	1400
July	1st to 10th	Night	9% 5% 2 3 2 2 3 3 4 5% 62%	3180
	11th to 20th	Night	4 2 1 2 2 2 2 2 3 5% 76%	3180
	21st to end	Night	10% 4 1 3 2 2 3 3 5% 6% 59%	3758
August	1st to 10th	Night	6% 3 1 2 2 1 2 2 4 5% 72%	2641
	11th to 20th	Night	16% 6% 2 7% 3 4 3 4 5% 6% 44%	2902
	21st to end	Night	17% 5% 2 6% 5% 4 4 3 5% 6% 44%	3332
September	1st to 10th	Night	11% 5% 2 6% 4 3 3 3 4 6% 55%	2000
	11th to 20th	Night	21% 7% 2 6% 4 3 3 4 4 5% 41%	2011
	21st to end	Night	26% 11% 2 5% 3 3 3 3 4 6% 34%	2287
October	1st to 10th	Night	24% 12% 3 7% 5% 4 4 3 4 5% 29%	3920
	11th to 20th	Night	34% 10% 3 5% 3 4 3 2 3 5% 27%	3897
	21st to end	Night	33% 12% 4 7% 4 3 4 3 3 4 21%	4548
November	1st to 10th	Night	41% 13% 3 7% 4 3 3 3 3 4 17%	2870
	11th to 20th	Night	37% 15% 4 6% 4 3 3 2 3 3 20%	2940
	21st to end	Night	36% 13% 3 8% 4 4 3 2 3 4 21%	2940
December	1st to 10th	Night	27% 14% 3 6% 4 4 3 3 4 5% 27%	4820
	11th to 20th	Night	42% 17% 4 7% 4 3 3 2 3 3 12%	5710
	21st to end	Night	42% 19% 4 7% 4 3 2 2 2 3 12%	7623

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	76% 6% 7% 7% 2 1	4125
	11th to 20th	Day	47% 7% 10% 16% 17% 3	4140
	21st to end	Day	67% 3 5% 14% 10% 1	5097
February	1st to 10th	Day	71% 6% 7% 8% 5% 3	1890
	11th to 20th	Day	66% 5% 8% 12% 7% 2	1854
	21st to end	Day	72% 5% 8% 9% 4 3	1559
March	1st to 10th	Day	70% 7% 7% 10% 5%	4793
	11th to 20th	Day	66% 6% 7% 15% 6% 1	5110
	21st to end	Day	75% 7% 7% 7% 2 1	5736
April	1st to 10th	Day	73% 7% 10% 7% 2	2413
	11th to 20th	Day	66% 8% 6% 12% 7% 1	2491
	21st to end	Day	69% 7% 7% 10% 6%	2656
May	1st to 10th	Day	47% 10% 14% 18% 10% 1	6320
	11th to 20th	Day	55% 10% 17% 15% 3	6280
	21st to end	Day	60% 11% 14% 13% 3	7134
June	1st to 10th	Day	62% 7% 13% 11% 4 2	3000
	11th to 20th	Day	68% 8% 11% 10% 4	3000
	21st to end	Day	55% 7% 13% 16% 7% 2	3000
July	1st to 10th	Day	30% 7% 17% 22% 17% 7%	6706
	11th to 20th	Day	20% 6% 18% 33% 21% 2	6699
	21st to end	Day	26% 10% 28% 22% 12% 2	6886
August	1st to 10th	Day	23% 4 11% 43% 17% 1	4479
	11th to 20th	Day	45% 9% 19% 18% 8% 2	4195
	21st to end	Day	44% 7% 18% 20% 10% 2	4579
September	1st to 10th	Day	41% 6% 13% 24% 12% 4	2400
	11th to 20th	Day	50% 5% 10% 19% 15% 2	2385
	21st to end	Day	55% 6% 13% 16% 9% 2	2112
October	1st to 10th	Day	59% 9% 12% 15% 6%	3280
	11th to 20th	Day	65% 7% 10% 12% 6%	3261
	21st to end	Day	69% 10% 8% 7% 4 1	3251
November	1st to 10th	Day	74% 5% 8% 8% 5% 1	1648
	11th to 20th	Day	74% 5% 6% 6% 7% 3	1680
	21st to end	Day	73% 4 5% 9% 8% 2	1680
December	1st to 10th	Day	59% 7% 12% 12% 9% 1	2575
	11th to 20th	Day	79% 6% 7% 5% 2 1	2718
	21st to end	Day	82% 6% 4 4 3 1	3575
January	1st to 10th	Night	78% 5% 5% 7% 5% 1	8770
	11th to 20th	Night	45% 7% 10% 17% 18% 3	8820
	21st to end	Night	62% 4 7% 15% 11% 1	9084
February	1st to 10th	Night	69% 5% 7% 9% 7% 3	2730
	11th to 20th	Night	66% 5% 8% 12% 7% 3	2664
	21st to end	Night	66% 6% 8% 12% 7% 2	2246
March	1st to 10th	Night	66% 7% 8% 11% 8% 1	5319
	11th to 20th	Night	65% 7% 8% 13% 7%	5110
	21st to end	Night	74% 6% 10% 6% 3 1	5481
April	1st to 10th	Night	69% 7% 12% 11% 2	2010
	11th to 20th	Night	60% 7% 9% 15% 9% 1	1856
	21st to end	Night	61% 5% 13% 13% 7%	1742
May	1st to 10th	Night	43% 7% 15% 24% 11%	3637
	11th to 20th	Night	47% 13% 21% 16% 4	3616
	21st to end	Night	59% 9% 15% 14% 3	3725
June	1st to 10th	Night	54% 7% 17% 13% 5% 3	1400
	11th to 20th	Night	59% 8% 14% 13% 5%	1400
	21st to end	Night	49% 9% 16% 16% 7% 3	1400
July	1st to 10th	Night	26% 6% 21% 23% 16% 7%	3145
	11th to 20th	Night	14% 7% 20% 32% 26% 2	3138
	21st to end	Night	26% 6% 25% 25% 14% 4	3652
August	1st to 10th	Night	17% 4 15% 35% 27% 2	2633
	11th to 20th	Night	41% 10% 22% 15% 9% 4	2929
	21st to end	Night	42% 7% 20% 20% 10% 2	3332
September	1st to 10th	Night	33% 8% 17% 25% 14% 4	2000
	11th to 20th	Night	46% 7% 11% 17% 13% 5%	2011
	21st to end	Night	53% 5% 13% 18% 8% 2	2287
October	1st to 10th	Night	59% 7% 15% 12% 7% 1	3920
	11th to 20th	Night	62% 6% 8% 15% 9%	3897
	21st to end	Night	66% 8% 8% 12% 6% 1	4548
November	1st to 10th	Night	75% 5% 7% 8% 5% 1	2870
	11th to 20th	Night	73% 5% 6% 8% 6% 3	2940
	21st to end	Night	71% 4 6% 9% 8% 2	2940
December	1st to 10th	Night	61% 6% 11% 14% 6% 2	4820
	11th to 20th	Night	79% 6% 6% 5% 3 1	5706
	21st to end	Night	81% 5% 5% 6% 3 1	7623

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	47% 9% 19% 16% 5% 3	220
	11th to 20th	Day	38% 12% 20% 20% 10% 1	220
	21st to end	Day	46% 9% 19% 18% 6% 1	266
February	1st to 10th	Day	40% 11% 26% 18% 4 1	430
	11th to 20th	Day	35% 13% 25% 20% 5% 1	425
	21st to end	Day	33% 18% 28% 13% 6% 1	357
March	1st to 10th	Day	33% 17% 25% 20% 5% 1	540
	11th to 20th	Day	37% 17% 19% 17% 9% 1	540
	21st to end	Day	36% 18% 24% 16% 5% 1	594
April	1st to 10th	Day	37% 17% 20% 18% 7% 1	505
	11th to 20th	Day	27% 18% 27% 20% 6% 2	492
	21st to end	Day	29% 18% 27% 16% 9% 1	500
May	1st to 10th	Day	21% 17% 29% 25% 7% 1	503
	11th to 20th	Day	23% 13% 26% 26% 10% 2	528
	21st to end	Day	23% 15% 28% 24% 8% 2	673
June	1st to 10th	Day	25% 14% 27% 25% 7% 2	730
	11th to 20th	Day	23% 17% 32% 19% 8% 1	730
	21st to end	Day	17% 13% 28% 29% 11% 2	730
July	1st to 10th	Day	18% 10% 25% 35% 11% 2	721
	11th to 20th	Day	9% 10% 31% 36% 12% 3	718
	21st to end	Day	9% 9% 25% 37% 16% 4	669
August	1st to 10th	Day	12% 7% 23% 35% 16% 8%	527
	11th to 20th	Day	10% 7% 24% 38% 16% 4	517
	21st to end	Day	16% 10% 26% 30% 14% 3	583
September	1st to 10th	Day	17% 10% 28% 28% 15% 2	530
	11th to 20th	Day	25% 12% 22% 26% 13% 2	530
	21st to end	Day	30% 12% 25% 20% 11% 3	530
October	1st to 10th	Day	31% 11% 22% 22% 12% 2	530
	11th to 20th	Day	41% 8% 19% 18% 10% 4	530
	21st to end	Day	41% 12% 22% 15% 7% 3	427
November	1st to 10th	Day	38% 15% 25% 15% 6%	220
	11th to 20th	Day	46% 8% 17% 12% 11% 5%	220
	21st to end	Day	47% 14% 18% 10% 5% 8%	220
December	1st to 10th	Day	45% 9% 14% 15% 14% 3	220
	11th to 20th	Day	47% 11% 17% 16% 7% 2	220
	21st to end	Day	44% 8% 29% 16% 4	242
January	1st to 10th	Night	47% 12% 20% 14% 6% 1	950
	11th to 20th	Night	40% 7% 26% 21% 7%	950
	21st to end	Night	42% 7% 22% 21% 7%	954
February	1st to 10th	Night	36% 10% 28% 21% 6%	840
	11th to 20th	Night	34% 8% 29% 22% 6%	824
	21st to end	Night	37% 12% 22% 20% 9% 1	692
March	1st to 10th	Night	36% 10% 23% 19% 11% 1	840
	11th to 20th	Night	42% 9% 20% 21% 8%	840
	21st to end	Night	40% 8% 20% 21% 10% 1	924
April	1st to 10th	Night	35% 7% 21% 26% 10% 1	804
	11th to 20th	Night	28% 9% 27% 25% 10% 1	668
	21st to end	Night	32% 5% 25% 25% 13%	542
May	1st to 10th	Night	19% 3 24% 34% 19% 2	400
	11th to 20th	Night	21% 4 18% 30% 25% 2	394
	21st to end	Night	21% 5% 19% 35% 19% 2	433
June	1st to 10th	Night	26% 4 18% 32% 18% 2	400
	11th to 20th	Night	21% 9% 22% 28% 18% 2	400
	21st to end	Night	16% 7% 19% 31% 26% 2	400
July	1st to 10th	Night	13% 1 17% 30% 36% 4	390
	11th to 20th	Night	11% 2 10% 37% 36% 4	388
	21st to end	Night	9% 2 9% 30% 43% 7%	438
August	1st to 10th	Night	11% 2 6% 29% 42% 9%	417
	11th to 20th	Night	11% 2 9% 34% 39% 5%	594
	21st to end	Night	16% 4 15% 33% 30% 3	708
September	1st to 10th	Night	12% 4 17% 35% 29% 3	800
	11th to 20th	Night	25% 3 16% 24% 27% 5%	800
	21st to end	Night	33% 5% 17% 27% 17% 1	800
October	1st to 10th	Night	27% 8% 20% 27% 18% 1	800
	11th to 20th	Night	38% 6% 19% 22% 13% 2	800
	21st to end	Night	42% 9% 24% 19% 6% 1	880
November	1st to 10th	Night	46% 10% 23% 18% 2	820
	11th to 20th	Night	44% 8% 26% 15% 6% 1	840
	21st to end	Night	43% 9% 23% 17% 7% 1	840
December	1st to 10th	Night	37% 8% 26% 22% 6%	876
	11th to 20th	Night	51% 9% 23% 14% 2	950
	21st to end	Night	46% 12% 27% 13% 1	1045

Page generated at 2026-03-29 23:18:41. Version ac07

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