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 2025-03-12.

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	27% 13% 4 9% 6% 5% 4 3 5% 5% 19%	112247
	Night	30% 12% 4 8% 5% 5% 4 3 5% 5% 19%	115435
Transparency	Day	65% 7% 12% 11% 4	111988
	Night	66% 7% 12% 11% 3	115340
Seeing	Day	31% 8% 18% 22% 16% 5%	16417
	Night	35% 7% 15% 21% 16% 5%	24335

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	39% 17% 4 9% 6% 4 4 3 3 4 8%	3179
	11th to 20th	Day	29% 12% 4 8% 5% 5% 4 2 4 7% 20%	3159
	21st to end	Day	41% 13% 4 8% 4 4 3 2 3 4 14%	3908
February	1st to 10th	Day	33% 14% 4 9% 5% 5% 4 2 4 4 15%	1669
	11th to 20th	Day	30% 14% 5% 8% 5% 4 3 2 4 5% 21%	1755
	21st to end	Day	29% 17% 3 10% 6% 4 4 3 4 3 16%	1545
March	1st to 10th	Day	27% 17% 4 10% 7% 5% 5% 4 5% 4 13%	3282
	11th to 20th	Day	28% 16% 6% 11% 6% 5% 4 3 3 3 16%	3503
	21st to end	Day	23% 14% 4 10% 6% 5% 5% 3 4 5% 21%	3825
April	1st to 10th	Day	32% 17% 4 10% 6% 4 4 3 4 4 10%	2342
	11th to 20th	Day	25% 14% 4 10% 6% 5% 4 3 5% 4 20%	2438
	21st to end	Day	29% 14% 4 11% 6% 5% 5% 3 5% 5% 14%	2470
May	1st to 10th	Day	23% 12% 3 9% 6% 5% 5% 4 5% 6% 21%	4279
	11th to 20th	Day	21% 14% 5% 10% 6% 5% 5% 3 5% 6% 20%	4696
	21st to end	Day	30% 14% 5% 10% 6% 5% 4 3 4 4 15%	5161
June	1st to 10th	Day	29% 13% 4 10% 7% 5% 4 4 5% 5% 14%	2850
	11th to 20th	Day	29% 16% 4 9% 6% 6% 4 3 5% 6% 12%	2850
	21st to end	Day	29% 11% 3 9% 6% 5% 4 4 4 5% 19%	2850
July	1st to 10th	Day	12% 7% 2 6% 4 4 4 3 6% 8% 45%	4740
	11th to 20th	Day	12% 9% 3 9% 5% 6% 5% 4 7% 9% 32%	4740
	21st to end	Day	25% 13% 4 9% 6% 5% 6% 4 5% 6% 18%	5118
August	1st to 10th	Day	11% 8% 3 9% 6% 5% 4 4 5% 6% 40%	4328
	11th to 20th	Day	19% 15% 5% 14% 6% 5% 5% 3 5% 6% 18%	4026
	21st to end	Day	20% 10% 3 10% 5% 5% 6% 4 6% 7% 23%	4521
September	1st to 10th	Day	24% 12% 4 9% 5% 5% 4 3 5% 7% 24%	2369
	11th to 20th	Day	23% 11% 4 9% 6% 4 5% 4 5% 6% 23%	2090
	21st to end	Day	31% 10% 4 8% 5% 6% 5% 4 5% 5% 17%	2090
October	1st to 10th	Day	34% 10% 4 9% 5% 6% 5% 4 5% 4 13%	3277
	11th to 20th	Day	34% 11% 4 9% 6% 5% 5% 4 5% 6% 11%	3040
	21st to end	Day	25% 13% 5% 11% 6% 5% 5% 4 5% 5% 15%	3101
November	1st to 10th	Day	39% 13% 3 8% 5% 4 4 2 3 4 14%	1601
	11th to 20th	Day	37% 13% 3 9% 5% 5% 4 4 4 3 13%	1600
	21st to end	Day	40% 11% 3 9% 4 4 4 3 4 3 14%	1412
December	1st to 10th	Day	32% 14% 3 10% 6% 5% 4 4 4 6% 12%	2290
	11th to 20th	Day	47% 13% 4 8% 4 4 3 3 3 3 8%	2645
	21st to end	Day	47% 14% 4 9% 5% 3 3 2 3 3 6%	3498
January	1st to 10th	Night	39% 17% 4 10% 5% 4 4 3 3 3 8%	6766
	11th to 20th	Night	28% 12% 3 9% 5% 5% 5% 4 5% 6% 19%	6739
	21st to end	Night	45% 12% 3 6% 4 3 3 2 3 4 16%	7062
February	1st to 10th	Night	37% 13% 4 8% 5% 3 3 3 4 3 16%	2730
	11th to 20th	Night	28% 13% 3 9% 5% 4 3 2 4 5% 24%	2532
	21st to end	Night	27% 18% 4 8% 5% 5% 3 3 3 4 21%	2080
March	1st to 10th	Night	26% 14% 5% 9% 6% 5% 4 3 5% 5% 18%	3804
	11th to 20th	Night	23% 14% 5% 9% 6% 6% 6% 4 6% 4 16%	3504
	21st to end	Night	22% 14% 4 9% 5% 5% 4 3 5% 5% 23%	3828
April	1st to 10th	Night	27% 15% 4 9% 5% 5% 4 3 5% 5% 17%	1837
	11th to 20th	Night	24% 14% 4 8% 7% 4 5% 3 4 6% 21%	1691
	21st to end	Night	25% 12% 4 9% 7% 5% 4 3 5% 4 21%	1710
May	1st to 10th	Night	18% 8% 2 6% 5% 5% 5% 4 6% 9% 33%	2682
	11th to 20th	Night	17% 14% 5% 8% 6% 4 5% 4 7% 8% 21%	2199
	21st to end	Night	29% 10% 4 9% 5% 5% 4 4 5% 5% 20%	2414
June	1st to 10th	Night	23% 10% 2 8% 5% 5% 6% 4 5% 7% 23%	1330
	11th to 20th	Night	23% 12% 4 9% 7% 5% 5% 3 5% 7% 20%	1330
	21st to end	Night	21% 11% 4 8% 5% 5% 5% 4 6% 7% 24%	1330
July	1st to 10th	Night	10% 6% 2 6% 5% 5% 4 2 4 8% 47%	2220
	11th to 20th	Night	9% 6% 2 7% 6% 6% 5% 5% 7% 9% 38%	2220
	21st to end	Night	15% 11% 3 9% 6% 5% 6% 5% 8% 7% 24%	2431
August	1st to 10th	Night	8% 6% 2 7% 5% 5% 5% 4 5% 7% 46%	2611
	11th to 20th	Night	13% 11% 4 9% 5% 5% 6% 5% 6% 8% 28%	2812
	21st to end	Night	18% 7% 3 8% 5% 6% 5% 4 6% 7% 31%	3146
September	1st to 10th	Night	19% 10% 3 8% 6% 5% 4 4 5% 8% 28%	1806
	11th to 20th	Night	20% 8% 3 8% 5% 5% 4 3 4 6% 33%	2090
	21st to end	Night	32% 10% 2 7% 5% 5% 4 4 4 6% 20%	2090
October	1st to 10th	Night	40% 8% 3 6% 4 5% 4 4 5% 5% 17%	3702
	11th to 20th	Night	39% 8% 3 7% 5% 6% 5% 4 5% 5% 12%	3891
	21st to end	Night	29% 10% 3 10% 6% 5% 5% 3 5% 4 19%	4458
November	1st to 10th	Night	37% 12% 4 9% 6% 5% 4 3 4 3 13%	2697
	11th to 20th	Night	36% 13% 4 10% 6% 5% 4 3 4 4 14%	2800
	21st to end	Night	37% 12% 4 8% 5% 4 3 4 4 4 15%	2985
December	1st to 10th	Night	37% 13% 4 9% 6% 4 4 3 3 4 14%	4890
	11th to 20th	Night	42% 14% 4 8% 5% 4 3 2 3 3 11%	5560
	21st to end	Night	45% 14% 4 9% 5% 4 3 2 3 4 7%	7458

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	79% 4 8% 7% 1	3179
	11th to 20th	Day	63% 6% 11% 14% 5% 1	3180
	21st to end	Day	75% 4 11% 9% 2	3908
February	1st to 10th	Day	72% 5% 6% 7% 7% 2	1669
	11th to 20th	Day	66% 4 12% 11% 5% 2	1764
	21st to end	Day	71% 5% 8% 9% 5% 2	1545
March	1st to 10th	Day	72% 5% 10% 8% 5%	3282
	11th to 20th	Day	73% 5% 7% 10% 5% 1	3503
	21st to end	Day	62% 9% 14% 11% 3	3825
April	1st to 10th	Day	75% 6% 9% 7% 2	2342
	11th to 20th	Day	65% 5% 10% 11% 7% 1	2438
	21st to end	Day	69% 5% 12% 10% 3 1	2470
May	1st to 10th	Day	56% 11% 16% 14% 3	4279
	11th to 20th	Day	61% 9% 18% 10% 2	4699
	21st to end	Day	69% 6% 11% 10% 3	5162
June	1st to 10th	Day	70% 8% 12% 7% 2 1	2850
	11th to 20th	Day	71% 7% 14% 7% 1	2850
	21st to end	Day	64% 10% 13% 10% 2	2850
July	1st to 10th	Day	35% 9% 13% 27% 14% 2	4666
	11th to 20th	Day	46% 9% 27% 17% 1	4659
	21st to end	Day	60% 10% 15% 12% 2	4956
August	1st to 10th	Day	44% 10% 11% 28% 7%	4311
	11th to 20th	Day	63% 10% 16% 8% 3	4065
	21st to end	Day	57% 10% 20% 12% 2	4520
September	1st to 10th	Day	59% 9% 17% 10% 3 1	2369
	11th to 20th	Day	60% 9% 13% 13% 5%	2090
	21st to end	Day	66% 9% 11% 9% 5%	2090
October	1st to 10th	Day	68% 8% 11% 9% 2 1	3277
	11th to 20th	Day	70% 7% 9% 12% 2	3040
	21st to end	Day	67% 7% 9% 11% 6%	3101
November	1st to 10th	Day	75% 6% 9% 7% 3	1601
	11th to 20th	Day	74% 6% 7% 8% 4 1	1600
	21st to end	Day	75% 5% 8% 7% 5% 1	1412
December	1st to 10th	Day	72% 6% 10% 8% 3	2290
	11th to 20th	Day	79% 6% 6% 6% 2 1	2648
	21st to end	Day	84% 4 6% 5% 1 1	3498
January	1st to 10th	Night	82% 4 6% 6% 2	6766
	11th to 20th	Night	63% 7% 13% 14% 3 1	6780
	21st to end	Night	73% 3 10% 11% 2	7062
February	1st to 10th	Night	73% 5% 6% 8% 8% 1	2730
	11th to 20th	Night	64% 5% 12% 13% 6% 1	2534
	21st to end	Night	68% 5% 10% 11% 4 2	2080
March	1st to 10th	Night	66% 8% 9% 12% 5%	3804
	11th to 20th	Night	69% 7% 10% 11% 3 1	3505
	21st to end	Night	62% 8% 14% 11% 4	3828
April	1st to 10th	Night	68% 7% 13% 8% 4	1837
	11th to 20th	Night	65% 4 11% 12% 7% 1	1691
	21st to end	Night	65% 5% 12% 14% 2 1	1710
May	1st to 10th	Night	48% 11% 20% 18% 2	2682
	11th to 20th	Night	59% 11% 20% 8% 2	2199
	21st to end	Night	67% 8% 13% 9% 3	2414
June	1st to 10th	Night	61% 6% 18% 12% 3 1	1330
	11th to 20th	Night	64% 8% 18% 9% 2	1330
	21st to end	Night	57% 9% 20% 12% 3	1330
July	1st to 10th	Night	36% 8% 13% 24% 19%	2185
	11th to 20th	Night	39% 11% 33% 16% 2	2178
	21st to end	Night	53% 12% 19% 14% 3	2354
August	1st to 10th	Night	37% 8% 16% 31% 6%	2603
	11th to 20th	Night	52% 12% 23% 11% 1 1	2839
	21st to end	Night	51% 10% 23% 15% 2	3146
September	1st to 10th	Night	56% 8% 19% 13% 3 1	1806
	11th to 20th	Night	53% 10% 15% 17% 6%	2090
	21st to end	Night	65% 7% 12% 11% 3 1	2090
October	1st to 10th	Night	68% 7% 13% 10% 2	3702
	11th to 20th	Night	72% 7% 9% 11% 2	3891
	21st to end	Night	64% 8% 10% 12% 6%	4458
November	1st to 10th	Night	77% 5% 7% 7% 4	2697
	11th to 20th	Night	75% 6% 8% 6% 5% 1	2800
	21st to end	Night	74% 4 8% 8% 4 2	2985
December	1st to 10th	Night	75% 5% 9% 8% 3	4890
	11th to 20th	Night	78% 5% 7% 7% 2	5556
	21st to end	Night	81% 5% 7% 5% 1 1	7458

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	48% 10% 18% 16% 6% 4	200
	11th to 20th	Day	46% 12% 19% 16% 6% 2	200
	21st to end	Day	42% 9% 19% 16% 11% 3	396
February	1st to 10th	Day	41% 13% 20% 18% 7% 2	400
	11th to 20th	Day	37% 12% 20% 17% 12% 2	395
	21st to end	Day	36% 18% 21% 16% 7% 2	331
March	1st to 10th	Day	34% 11% 18% 18% 16% 3	416
	11th to 20th	Day	34% 13% 20% 17% 12% 3	465
	21st to end	Day	37% 8% 17% 22% 12% 5%	506
April	1st to 10th	Day	38% 9% 22% 20% 9% 3	460
	11th to 20th	Day	28% 11% 21% 19% 16% 5%	452
	21st to end	Day	33% 9% 17% 23% 13% 5%	460
May	1st to 10th	Day	29% 7% 16% 28% 16% 5%	464
	11th to 20th	Day	26% 6% 20% 28% 16% 4	675
	21st to end	Day	27% 9% 19% 28% 14% 2	735
June	1st to 10th	Day	35% 6% 18% 24% 14% 4	680
	11th to 20th	Day	31% 8% 20% 25% 13% 3	680
	21st to end	Day	28% 6% 15% 26% 20% 4	680
July	1st to 10th	Day	18% 6% 16% 27% 25% 8%	671
	11th to 20th	Day	18% 3 19% 31% 22% 6%	668
	21st to end	Day	20% 5% 14% 27% 24% 9%	739
August	1st to 10th	Day	18% 3 13% 27% 30% 10%	633
	11th to 20th	Day	21% 7% 12% 27% 26% 7%	477
	21st to end	Day	26% 6% 19% 22% 21% 5%	539
September	1st to 10th	Day	29% 4 13% 24% 21% 8%	490
	11th to 20th	Day	30% 8% 15% 20% 19% 9%	490
	21st to end	Day	36% 9% 16% 20% 14% 6%	490
October	1st to 10th	Day	36% 11% 14% 18% 15% 7%	490
	11th to 20th	Day	39% 8% 19% 19% 11% 4	453
	21st to end	Day	35% 10% 23% 16% 11% 4	429
November	1st to 10th	Day	42% 13% 15% 17% 11% 2	233
	11th to 20th	Day	37% 9% 21% 14% 13% 7%	200
	21st to end	Day	48% 11% 15% 10% 11% 7%	200
December	1st to 10th	Day	43% 7% 15% 21% 11% 4	200
	11th to 20th	Day	42% 10% 20% 17% 10% 3	200
	21st to end	Day	48% 9% 19% 18% 5% 1	220
January	1st to 10th	Night	47% 11% 19% 14% 7% 2	900
	11th to 20th	Night	44% 9% 14% 22% 10% 1	900
	21st to end	Night	45% 7% 15% 17% 13% 4	990
February	1st to 10th	Night	44% 9% 19% 19% 8% 1	865
	11th to 20th	Night	35% 8% 18% 21% 16% 2	784
	21st to end	Night	39% 13% 14% 19% 10% 4	660
March	1st to 10th	Night	32% 10% 20% 20% 15% 3	800
	11th to 20th	Night	36% 9% 19% 21% 14% 2	766
	21st to end	Night	35% 9% 15% 22% 15% 5%	836
April	1st to 10th	Night	33% 9% 14% 24% 14% 5%	607
	11th to 20th	Night	31% 5% 17% 25% 17% 4	563
	21st to end	Night	32% 5% 16% 28% 16% 4	570
May	1st to 10th	Night	27% 6% 10% 27% 26% 5%	475
	11th to 20th	Night	25% 5% 9% 27% 29% 4	374
	21st to end	Night	27% 7% 10% 30% 21% 5%	411
June	1st to 10th	Night	26% 6% 11% 26% 24% 6%	380
	11th to 20th	Night	26% 6% 13% 26% 24% 5%	380
	21st to end	Night	21% 7% 9% 28% 26% 8%	380
July	1st to 10th	Night	18% 5% 10% 25% 29% 12%	370
	11th to 20th	Night	17% 5% 9% 24% 33% 11%	368
	21st to end	Night	16% 6% 7% 25% 31% 15%	421
August	1st to 10th	Night	18% 5% 7% 18% 33% 20%	567
	11th to 20th	Night	17% 5% 9% 24% 33% 12%	564
	21st to end	Night	24% 7% 10% 27% 26% 5%	627
September	1st to 10th	Night	25% 6% 9% 24% 28% 9%	638
	11th to 20th	Night	23% 5% 11% 21% 23% 17%	760
	21st to end	Night	37% 5% 12% 23% 19% 5%	760
October	1st to 10th	Night	38% 6% 12% 20% 17% 7%	760
	11th to 20th	Night	41% 4 13% 21% 14% 6%	760
	21st to end	Night	39% 7% 18% 19% 13% 3	836
November	1st to 10th	Night	44% 9% 15% 21% 10% 1	780
	11th to 20th	Night	43% 8% 17% 20% 10% 3	800
	21st to end	Night	43% 8% 16% 18% 10% 4	893
December	1st to 10th	Night	39% 9% 16% 21% 12% 3	900
	11th to 20th	Night	44% 7% 19% 17% 10% 2	900
	21st to end	Night	44% 11% 20% 19% 5% 1	990

Page generated at 2025-03-09 05:08:42. Version ac07

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