Port Hardy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Hardy clear sky chart from 2005-11-06 to 2026-07-16.

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	26% 12% 4 10% 6% 5% 5% 3 5% 5% 19%	142232
	Night	29% 12% 4 8% 5% 5% 4 3 5% 5% 20%	139195
Transparency	Day	64% 7% 13% 12% 4	141929
	Night	65% 7% 12% 12% 4	139080
Seeing	Day	31% 9% 18% 22% 15% 5%	18311
	Night	35% 8% 15% 22% 16% 5%	25956

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	40% 16% 4 10% 6% 4 4 3 3 3 6%	4125
	11th to 20th	Day	29% 10% 3 8% 5% 4 4 3 5% 7% 23%	4119
	21st to end	Day	41% 13% 4 7% 4 4 3 3 3 4 14%	5061
February	1st to 10th	Day	34% 14% 4 9% 5% 5% 4 2 4 4 15%	1753
	11th to 20th	Day	30% 14% 5% 8% 5% 4 3 2 4 4 21%	1845
	21st to end	Day	29% 17% 3 10% 6% 4 4 3 4 3 16%	1620
March	1st to 10th	Day	31% 16% 4 9% 6% 5% 5% 4 4 4 13%	4679
	11th to 20th	Day	27% 16% 6% 12% 6% 6% 4 4 4 3 12%	5110
	21st to end	Day	26% 15% 4 11% 7% 6% 5% 3 4 4 15%	5607
April	1st to 10th	Day	30% 17% 5% 11% 6% 5% 5% 3 4 4 11%	2588
	11th to 20th	Day	24% 14% 4 10% 6% 5% 4 3 5% 4 20%	2698
	21st to end	Day	27% 13% 4 10% 5% 5% 5% 3 5% 5% 17%	2730
May	1st to 10th	Day	21% 12% 4 9% 6% 5% 4 4 5% 6% 23%	7924
	11th to 20th	Day	21% 13% 5% 12% 6% 5% 5% 4 5% 7% 16%	8757
	21st to end	Day	29% 12% 4 9% 6% 5% 5% 3 5% 5% 17%	9649
June	1st to 10th	Day	28% 13% 4 10% 6% 5% 4 4 5% 5% 16%	3150
	11th to 20th	Day	27% 15% 4 9% 6% 6% 5% 4 5% 6% 14%	3150
	21st to end	Day	29% 11% 3 9% 6% 5% 4 4 4 5% 19%	3150
July	1st to 10th	Day	13% 9% 3 9% 6% 5% 5% 4 6% 7% 34%	6930
	11th to 20th	Day	11% 10% 3 9% 6% 5% 6% 4 6% 8% 31%	6856
	21st to end	Day	18% 11% 4 9% 6% 6% 6% 4 6% 7% 24%	7342
August	1st to 10th	Day	11% 9% 4 9% 6% 5% 4 4 5% 6% 40%	4465
	11th to 20th	Day	19% 15% 5% 13% 6% 5% 4 3 5% 6% 19%	4156
	21st to end	Day	19% 11% 3 10% 5% 5% 6% 4 6% 7% 24%	4664
September	1st to 10th	Day	23% 12% 4 9% 4 5% 4 3 4 7% 24%	2493
	11th to 20th	Day	23% 10% 4 9% 6% 4 5% 4 5% 6% 24%	2200
	21st to end	Day	32% 10% 4 8% 5% 6% 5% 4 5% 5% 16%	2200
October	1st to 10th	Day	33% 10% 4 9% 5% 6% 5% 4 5% 5% 14%	3380
	11th to 20th	Day	34% 10% 3 9% 6% 5% 5% 4 5% 6% 12%	3136
	21st to end	Day	26% 12% 5% 10% 6% 5% 5% 5% 5% 5% 15%	3200
November	1st to 10th	Day	39% 12% 4 8% 5% 4 4 2 4 4 14%	1683
	11th to 20th	Day	37% 13% 3 8% 5% 5% 4 4 4 3 13%	1680
	21st to end	Day	39% 11% 3 10% 4 5% 4 3 4 3 13%	1482
December	1st to 10th	Day	32% 14% 3 10% 6% 5% 4 4 4 5% 11%	2360
	11th to 20th	Day	47% 13% 4 8% 4 4 3 3 3 3 8%	2715
	21st to end	Day	47% 14% 4 9% 5% 3 3 2 3 3 6%	3575
January	1st to 10th	Night	43% 15% 4 9% 5% 4 4 3 3 3 7%	8770
	11th to 20th	Night	28% 10% 3 8% 5% 4 5% 3 4 6% 24%	8779
	21st to end	Night	42% 12% 3 7% 4 3 3 2 3 4 16%	9142
February	1st to 10th	Night	38% 13% 4 8% 5% 3 3 3 4 3 16%	2866
	11th to 20th	Night	27% 13% 3 9% 5% 4 3 3 4 5% 24%	2662
	21st to end	Night	27% 18% 4 8% 5% 5% 4 2 3 4 20%	2181
March	1st to 10th	Night	27% 14% 5% 10% 6% 5% 4 3 4 4 17%	5419
	11th to 20th	Night	21% 14% 5% 10% 6% 5% 6% 4 6% 5% 17%	5109
	21st to end	Night	26% 14% 4 10% 5% 5% 4 3 5% 5% 18%	5610
April	1st to 10th	Night	26% 14% 4 9% 5% 5% 4 3 5% 6% 18%	2030
	11th to 20th	Night	23% 13% 4 8% 6% 4 5% 3 5% 6% 22%	1871
	21st to end	Night	23% 12% 4 9% 7% 5% 4 3 5% 5% 23%	1890
May	1st to 10th	Night	15% 9% 3 8% 5% 5% 4 3 5% 7% 34%	5006
	11th to 20th	Night	18% 13% 5% 10% 6% 5% 5% 4 7% 7% 21%	4105
	21st to end	Night	30% 9% 3 9% 5% 5% 4 3 4 5% 22%	4522
June	1st to 10th	Night	22% 10% 2 8% 5% 5% 6% 4 6% 7% 24%	1470
	11th to 20th	Night	22% 12% 4 9% 7% 5% 5% 3 5% 7% 21%	1470
	21st to end	Night	21% 11% 4 8% 5% 6% 5% 4 5% 6% 25%	1470
July	1st to 10th	Night	10% 8% 3 8% 6% 5% 4 3 5% 8% 39%	3250
	11th to 20th	Night	8% 9% 4 8% 6% 6% 5% 5% 7% 7% 37%	3215
	21st to end	Night	11% 9% 3 9% 6% 6% 6% 5% 8% 8% 28%	3499
August	1st to 10th	Night	8% 7% 2 7% 6% 5% 5% 4 5% 7% 45%	2693
	11th to 20th	Night	14% 11% 4 9% 5% 5% 6% 5% 6% 8% 28%	2902
	21st to end	Night	18% 7% 3 8% 5% 6% 5% 4 6% 7% 32%	3245
September	1st to 10th	Night	19% 11% 3 8% 6% 6% 4 4 5% 8% 27%	1902
	11th to 20th	Night	20% 8% 3 8% 5% 5% 4 3 4 7% 33%	2200
	21st to end	Night	32% 10% 3 7% 5% 5% 4 4 4 6% 20%	2200
October	1st to 10th	Night	40% 8% 3 6% 4 5% 4 4 5% 5% 17%	3819
	11th to 20th	Night	39% 8% 3 7% 5% 6% 5% 4 5% 5% 13%	4015
	21st to end	Night	29% 10% 4 10% 6% 5% 5% 3 5% 4 18%	4601
November	1st to 10th	Night	36% 12% 4 9% 6% 5% 4 3 4 4 13%	2835
	11th to 20th	Night	36% 13% 4 10% 6% 4 4 3 4 4 13%	2940
	21st to end	Night	37% 13% 4 8% 5% 4 3 4 4 4 15%	3134
December	1st to 10th	Night	38% 13% 4 9% 6% 4 4 3 3 3 13%	5040
	11th to 20th	Night	42% 14% 4 8% 5% 4 3 2 3 3 10%	5710
	21st to end	Night	45% 13% 4 9% 5% 4 3 2 3 4 7%	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	81% 4 7% 6% 1	4125
	11th to 20th	Day	59% 5% 9% 14% 11% 1	4140
	21st to end	Day	74% 3 9% 11% 2	5062
February	1st to 10th	Day	72% 6% 6% 7% 7% 2	1753
	11th to 20th	Day	67% 4 11% 11% 5% 1	1854
	21st to end	Day	71% 5% 8% 9% 5% 2	1620
March	1st to 10th	Day	72% 5% 10% 7% 6%	4679
	11th to 20th	Day	75% 5% 5% 9% 6% 1	5110
	21st to end	Day	70% 8% 11% 9% 2	5607
April	1st to 10th	Day	74% 6% 10% 8% 2	2588
	11th to 20th	Day	64% 5% 11% 11% 7% 1	2698
	21st to end	Day	65% 5% 14% 11% 3 1	2730
May	1st to 10th	Day	56% 9% 14% 18% 2	7924
	11th to 20th	Day	63% 9% 17% 10% 1	8760
	21st to end	Day	64% 7% 13% 12% 3	9650
June	1st to 10th	Day	68% 7% 13% 8% 3 1	3150
	11th to 20th	Day	68% 7% 14% 9% 1	3150
	21st to end	Day	64% 10% 14% 11% 2	3150
July	1st to 10th	Day	44% 11% 14% 20% 10% 1	6856
	11th to 20th	Day	47% 9% 25% 18% 1	6775
	21st to end	Day	54% 10% 22% 12% 1	7135
August	1st to 10th	Day	44% 10% 12% 27% 7%	4448
	11th to 20th	Day	62% 10% 16% 9% 3	4195
	21st to end	Day	56% 10% 19% 13% 2	4663
September	1st to 10th	Day	59% 9% 18% 11% 3 1	2493
	11th to 20th	Day	59% 9% 14% 13% 5%	2200
	21st to end	Day	67% 9% 11% 9% 5%	2200
October	1st to 10th	Day	68% 8% 12% 9% 3 1	3380
	11th to 20th	Day	69% 7% 8% 13% 3	3136
	21st to end	Day	67% 7% 9% 11% 6%	3200
November	1st to 10th	Day	74% 6% 9% 7% 3	1683
	11th to 20th	Day	74% 6% 7% 8% 4 1	1680
	21st to end	Day	75% 5% 7% 7% 5% 1	1482
December	1st to 10th	Day	72% 6% 11% 8% 3	2360
	11th to 20th	Day	80% 5% 6% 6% 2 1	2718
	21st to end	Day	84% 4 6% 5% 1 1	3575
January	1st to 10th	Night	82% 4 5% 6% 2	8770
	11th to 20th	Night	59% 6% 10% 16% 8% 1	8820
	21st to end	Night	72% 3 10% 13% 2	9142
February	1st to 10th	Night	73% 5% 5% 8% 7% 1	2866
	11th to 20th	Night	64% 5% 11% 13% 6% 1	2664
	21st to end	Night	68% 5% 10% 11% 4 2	2181
March	1st to 10th	Night	68% 7% 8% 13% 4	5419
	11th to 20th	Night	66% 7% 9% 12% 6%	5110
	21st to end	Night	67% 7% 11% 11% 3	5610
April	1st to 10th	Night	67% 7% 13% 9% 4	2030
	11th to 20th	Night	63% 5% 13% 13% 6%	1871
	21st to end	Night	62% 5% 15% 14% 2 1	1890
May	1st to 10th	Night	49% 8% 15% 24% 3	5003
	11th to 20th	Night	59% 9% 18% 12% 1	4105
	21st to end	Night	64% 6% 16% 12% 2	4526
June	1st to 10th	Night	60% 6% 17% 13% 3 1	1470
	11th to 20th	Night	62% 8% 17% 11% 1	1470
	21st to end	Night	57% 8% 19% 13% 3	1470
July	1st to 10th	Night	42% 8% 17% 20% 13%	3215
	11th to 20th	Night	42% 10% 27% 19% 1	3173
	21st to end	Night	45% 15% 26% 12% 2	3401
August	1st to 10th	Night	38% 9% 16% 30% 6%	2685
	11th to 20th	Night	52% 12% 22% 12% 1 1	2929
	21st to end	Night	50% 10% 22% 16% 2	3245
September	1st to 10th	Night	57% 8% 19% 13% 3 1	1902
	11th to 20th	Night	53% 9% 16% 17% 6%	2200
	21st to end	Night	66% 7% 12% 11% 3 1	2200
October	1st to 10th	Night	67% 7% 13% 10% 3	3819
	11th to 20th	Night	71% 7% 9% 11% 2	4015
	21st to end	Night	64% 8% 10% 12% 6%	4601
November	1st to 10th	Night	77% 5% 7% 7% 4	2835
	11th to 20th	Night	76% 5% 8% 6% 5% 1	2940
	21st to end	Night	74% 5% 8% 8% 4 2	3134
December	1st to 10th	Night	75% 5% 9% 8% 3	5040
	11th to 20th	Night	78% 5% 7% 7% 3	5706
	21st to end	Night	81% 5% 7% 6% 1 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% 10% 18% 16% 5% 3	220
	11th to 20th	Day	45% 11% 18% 15% 7% 3	220
	21st to end	Day	43% 9% 18% 16% 11% 3	427
February	1st to 10th	Day	43% 12% 20% 17% 6% 2	430
	11th to 20th	Day	36% 11% 20% 19% 12% 2	425
	21st to end	Day	37% 19% 21% 15% 7% 2	355
March	1st to 10th	Day	35% 11% 19% 16% 16% 3	447
	11th to 20th	Day	37% 14% 20% 16% 11% 3	540
	21st to end	Day	39% 9% 18% 20% 11% 4	594
April	1st to 10th	Day	37% 10% 22% 20% 9% 3	540
	11th to 20th	Day	28% 11% 21% 19% 16% 5%	532
	21st to end	Day	29% 11% 21% 21% 13% 5%	540
May	1st to 10th	Day	29% 8% 18% 27% 14% 5%	544
	11th to 20th	Day	27% 8% 21% 27% 14% 3	775
	21st to end	Day	29% 10% 20% 26% 13% 2	845
June	1st to 10th	Day	33% 8% 19% 23% 13% 3	780
	11th to 20th	Day	30% 9% 22% 24% 13% 3	780
	21st to end	Day	28% 7% 17% 25% 19% 4	780
July	1st to 10th	Day	19% 8% 17% 27% 23% 7%	771
	11th to 20th	Day	19% 4 21% 30% 20% 6%	744
	21st to end	Day	19% 5% 14% 29% 24% 9%	794
August	1st to 10th	Day	18% 4 13% 27% 28% 10%	680
	11th to 20th	Day	22% 8% 14% 25% 24% 7%	517
	21st to end	Day	26% 6% 18% 23% 22% 6%	583
September	1st to 10th	Day	29% 5% 13% 25% 20% 7%	530
	11th to 20th	Day	30% 8% 15% 20% 19% 8%	530
	21st to end	Day	38% 9% 16% 19% 13% 5%	530
October	1st to 10th	Day	36% 11% 15% 18% 14% 7%	530
	11th to 20th	Day	37% 9% 19% 19% 11% 4	489
	21st to end	Day	36% 11% 23% 16% 11% 4	462
November	1st to 10th	Day	41% 13% 18% 16% 10% 2	255
	11th to 20th	Day	40% 9% 20% 14% 11% 6%	220
	21st to end	Day	46% 11% 15% 12% 10% 6%	220
December	1st to 10th	Day	45% 8% 14% 19% 10% 4	220
	11th to 20th	Day	43% 11% 19% 15% 9% 3	220
	21st to end	Day	47% 10% 20% 18% 5% 1	242
January	1st to 10th	Night	48% 10% 19% 14% 7% 2	950
	11th to 20th	Night	44% 9% 13% 22% 11% 1	950
	21st to end	Night	45% 7% 14% 17% 13% 3	1045
February	1st to 10th	Night	45% 9% 18% 19% 7% 1	911
	11th to 20th	Night	34% 8% 19% 22% 16% 2	824
	21st to end	Night	39% 13% 14% 19% 10% 4	692
March	1st to 10th	Night	33% 10% 20% 20% 15% 3	840
	11th to 20th	Night	36% 9% 18% 21% 14% 2	840
	21st to end	Night	35% 10% 16% 22% 14% 4	924
April	1st to 10th	Night	32% 9% 14% 25% 14% 5%	671
	11th to 20th	Night	30% 6% 16% 25% 17% 5%	623
	21st to end	Night	30% 5% 16% 30% 15% 3	630
May	1st to 10th	Night	25% 7% 10% 27% 25% 5%	525
	11th to 20th	Night	25% 7% 10% 28% 27% 4	414
	21st to end	Night	27% 7% 11% 30% 20% 4	455
June	1st to 10th	Night	25% 8% 13% 25% 23% 6%	420
	11th to 20th	Night	26% 6% 14% 27% 22% 5%	420
	21st to end	Night	21% 7% 10% 29% 26% 7%	420
July	1st to 10th	Night	18% 7% 11% 26% 28% 11%	410
	11th to 20th	Night	17% 5% 10% 26% 32% 11%	398
	21st to end	Night	15% 6% 7% 25% 32% 15%	444
August	1st to 10th	Night	19% 5% 6% 18% 32% 19%	597
	11th to 20th	Night	18% 5% 9% 24% 32% 11%	594
	21st to end	Night	24% 7% 10% 26% 27% 7%	660
September	1st to 10th	Night	26% 6% 9% 23% 27% 9%	672
	11th to 20th	Night	23% 5% 11% 22% 23% 17%	800
	21st to end	Night	37% 5% 13% 23% 18% 5%	800
October	1st to 10th	Night	38% 6% 12% 21% 17% 7%	800
	11th to 20th	Night	40% 5% 14% 21% 14% 6%	800
	21st to end	Night	39% 7% 18% 20% 13% 3	880
November	1st to 10th	Night	44% 10% 15% 20% 9% 1	820
	11th to 20th	Night	43% 8% 17% 19% 9% 3	840
	21st to end	Night	43% 8% 16% 19% 9% 4	942
December	1st to 10th	Night	41% 9% 15% 19% 12% 3	950
	11th to 20th	Night	45% 8% 19% 16% 10% 2	950
	21st to end	Night	44% 11% 20% 19% 5% 1	1045

Page generated at 2026-07-13 00:14:49. Version ac07

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