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 2024-02-10.

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	30% 12% 4 8% 7% 4 5% 4 4 5% 17%	77721
	Night	32% 11% 4 7% 6% 3 4 4 4 5% 19%	81205
Transparency	Day	68% 7% 12% 9% 3 1	77423
	Night	69% 6% 11% 9% 4 1	81083
Seeing	Day	31% 7% 17% 23% 16% 5%	14996
	Night	35% 7% 15% 21% 17% 5%	22917

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% 17% 4 7% 6% 2 4 4 2 3 10%	2219
	11th to 20th	Day	33% 12% 4 6% 5% 4 4 3 3 6% 19%	2199
	21st to end	Day	51% 12% 4 6% 5% 3 4 3 3 3 6%	2726
February	1st to 10th	Day	34% 14% 5% 8% 6% 4 4 3 4 4 13%	1577
	11th to 20th	Day	31% 13% 6% 7% 6% 3 4 3 4 4 20%	1575
	21st to end	Day	29% 16% 4 9% 6% 3 4 4 4 3 18%	1386
March	1st to 10th	Day	28% 17% 5% 8% 7% 4 4 5% 5% 4 15%	1826
	11th to 20th	Day	31% 15% 6% 9% 7% 4 5% 4 4 3 11%	1980
	21st to end	Day	30% 16% 6% 9% 7% 3 4 3 3 4 14%	2178
April	1st to 10th	Day	32% 16% 5% 10% 7% 4 5% 4 4 4 10%	2218
	11th to 20th	Day	27% 13% 5% 9% 8% 4 4 4 5% 4 18%	2308
	21st to end	Day	30% 13% 5% 9% 7% 4 5% 4 5% 4 15%	2340
May	1st to 10th	Day	28% 12% 4 7% 7% 4 5% 4 5% 5% 19%	2430
	11th to 20th	Day	23% 13% 4 8% 8% 4 6% 4 4 5% 20%	2656
	21st to end	Day	27% 12% 6% 9% 7% 4 5% 4 4 5% 18%	2917
June	1st to 10th	Day	30% 12% 5% 9% 8% 4 4 5% 5% 5% 14%	2700
	11th to 20th	Day	31% 14% 5% 8% 7% 4 5% 4 5% 5% 12%	2700
	21st to end	Day	29% 9% 4 8% 7% 4 5% 5% 4 5% 20%	2700
July	1st to 10th	Day	21% 10% 4 7% 7% 4 6% 4 6% 7% 23%	2700
	11th to 20th	Day	21% 11% 5% 9% 7% 5% 5% 5% 6% 7% 21%	2700
	21st to end	Day	21% 11% 4 8% 7% 3 4 4 4 6% 27%	2930
August	1st to 10th	Day	17% 9% 3 8% 8% 5% 5% 5% 6% 7% 27%	2467
	11th to 20th	Day	19% 11% 4 10% 7% 4 5% 5% 5% 6% 24%	2298
	21st to end	Day	24% 12% 4 10% 7% 4 6% 5% 6% 5% 16%	2574
September	1st to 10th	Day	25% 11% 4 7% 6% 4 4 4 5% 7% 22%	2245
	11th to 20th	Day	23% 11% 4 9% 7% 3 5% 5% 5% 6% 23%	1980
	21st to end	Day	31% 9% 4 7% 6% 4 5% 5% 5% 5% 17%	1980
October	1st to 10th	Day	30% 12% 5% 7% 6% 4 4 4 5% 4 18%	1858
	11th to 20th	Day	34% 12% 6% 8% 7% 4 5% 4 4 5% 12%	1733
	21st to end	Day	33% 11% 4 8% 6% 4 5% 5% 4 5% 15%	1782
November	1st to 10th	Day	39% 11% 5% 8% 5% 3 4 3 4 4 14%	1520
	11th to 20th	Day	37% 13% 3 7% 6% 4 4 5% 4 3 14%	1520
	21st to end	Day	40% 9% 4 8% 5% 4 4 4 5% 3 14%	1342
December	1st to 10th	Day	29% 13% 3 7% 8% 4 7% 4 4 6% 15%	1330
	11th to 20th	Day	44% 12% 4 8% 5% 3 3 4 4 4 10%	1685
	21st to end	Day	48% 11% 4 7% 5% 3 4 3 4 3 7%	2442
January	1st to 10th	Night	39% 17% 5% 8% 7% 3 4 3 3 2 9%	4726
	11th to 20th	Night	33% 13% 4 7% 6% 4 4 4 4 5% 17%	4699
	21st to end	Night	55% 12% 3 6% 4 2 3 2 2 3 8%	4935
February	1st to 10th	Night	39% 13% 5% 7% 6% 2 4 3 3 4 15%	2586
	11th to 20th	Night	29% 12% 4 8% 5% 3 4 3 4 5% 22%	2272
	21st to end	Night	27% 17% 4 7% 5% 3 4 3 4 4 22%	1866
March	1st to 10th	Night	25% 14% 5% 8% 7% 4 5% 4 4 6% 19%	2134
	11th to 20th	Night	29% 14% 5% 8% 7% 4 5% 5% 5% 4 16%	1979
	21st to end	Night	29% 14% 5% 8% 6% 4 4 3 4 4 17%	2178
April	1st to 10th	Night	28% 14% 4 8% 6% 4 5% 3 5% 6% 17%	1742
	11th to 20th	Night	25% 13% 5% 8% 8% 3 6% 4 4 6% 19%	1601
	21st to end	Night	25% 11% 4 8% 7% 4 4 4 5% 5% 22%	1620
May	1st to 10th	Night	26% 9% 3 5% 6% 3 5% 5% 6% 7% 26%	1526
	11th to 20th	Night	19% 10% 5% 7% 7% 3 6% 6% 5% 8% 26%	1239
	21st to end	Night	22% 9% 4 9% 7% 5% 6% 5% 6% 6% 22%	1358
June	1st to 10th	Night	23% 9% 3 7% 6% 3 7% 5% 5% 8% 23%	1260
	11th to 20th	Night	24% 11% 5% 7% 8% 3 6% 5% 5% 7% 20%	1260
	21st to end	Night	21% 9% 5% 7% 5% 4 5% 5% 6% 7% 25%	1260
July	1st to 10th	Night	16% 8% 3 6% 7% 5% 5% 5% 5% 7% 33%	1260
	11th to 20th	Night	16% 8% 3 7% 6% 4 6% 5% 7% 7% 31%	1260
	21st to end	Night	14% 8% 4 7% 6% 3 4 5% 7% 8% 34%	1383
August	1st to 10th	Night	13% 9% 3 6% 8% 5% 6% 6% 6% 8% 31%	1471
	11th to 20th	Night	11% 8% 3 7% 6% 3 6% 7% 6% 8% 34%	1602
	21st to end	Night	21% 9% 4 8% 8% 4 5% 6% 5% 6% 24%	1782
September	1st to 10th	Night	20% 9% 3 6% 7% 4 5% 5% 5% 8% 27%	1710
	11th to 20th	Night	20% 8% 3 7% 6% 3 5% 4 4 6% 33%	1980
	21st to end	Night	31% 10% 3 6% 5% 3 5% 5% 5% 6% 21%	1980
October	1st to 10th	Night	31% 10% 3 6% 4 3 5% 4 4 5% 25%	2101
	11th to 20th	Night	37% 8% 4 6% 5% 4 5% 6% 5% 5% 16%	2224
	21st to end	Night	34% 11% 4 8% 6% 3 4 4 4 4 18%	2574
November	1st to 10th	Night	37% 11% 5% 8% 7% 4 5% 4 4 4 14%	2558
	11th to 20th	Night	36% 11% 5% 8% 7% 3 4 3 4 4 14%	2660
	21st to end	Night	38% 11% 4 7% 5% 3 4 4 4 4 15%	2835
December	1st to 10th	Night	32% 12% 3 6% 7% 3 4 4 4 4 20%	2850
	11th to 20th	Night	44% 12% 5% 7% 5% 3 3 3 3 3 12%	3520
	21st to end	Night	48% 11% 3 7% 5% 3 4 3 3 4 9%	5214

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% 6% 2 1	2219
	11th to 20th	Day	66% 5% 11% 9% 7% 2	2220
	21st to end	Day	85% 3 5% 5% 1	2726
February	1st to 10th	Day	75% 5% 6% 6% 6% 1	1577
	11th to 20th	Day	68% 4 11% 11% 4 1	1584
	21st to end	Day	69% 5% 8% 10% 5% 2	1386
March	1st to 10th	Day	72% 4 11% 10% 3	1826
	11th to 20th	Day	77% 4 9% 5% 4 1	1980
	21st to end	Day	72% 7% 11% 7% 3	2178
April	1st to 10th	Day	75% 6% 9% 7% 2	2218
	11th to 20th	Day	67% 5% 11% 11% 6%	2308
	21st to end	Day	69% 5% 11% 10% 3 1	2340
May	1st to 10th	Day	64% 8% 14% 11% 3	2430
	11th to 20th	Day	64% 9% 13% 11% 3	2659
	21st to end	Day	66% 7% 13% 11% 2	2918
June	1st to 10th	Day	71% 8% 13% 6% 2 1	2700
	11th to 20th	Day	72% 7% 14% 6% 1	2700
	21st to end	Day	62% 10% 14% 11% 2	2700
July	1st to 10th	Day	57% 12% 15% 13% 4	2626
	11th to 20th	Day	61% 11% 16% 11% 1	2619
	21st to end	Day	55% 11% 18% 13% 3 1	2767
August	1st to 10th	Day	53% 14% 16% 14% 4	2450
	11th to 20th	Day	58% 11% 14% 12% 5%	2298
	21st to end	Day	64% 11% 14% 9% 1	2574
September	1st to 10th	Day	60% 9% 18% 10% 2 1	2245
	11th to 20th	Day	60% 9% 12% 13% 5%	1980
	21st to end	Day	65% 9% 11% 9% 5%	1980
October	1st to 10th	Day	68% 8% 10% 9% 4 1	1858
	11th to 20th	Day	75% 6% 9% 8% 2	1733
	21st to end	Day	71% 7% 8% 8% 6%	1782
November	1st to 10th	Day	74% 6% 9% 7% 3 1	1520
	11th to 20th	Day	75% 6% 7% 7% 4 1	1520
	21st to end	Day	74% 5% 8% 6% 5% 1	1342
December	1st to 10th	Day	69% 6% 9% 9% 6% 1	1330
	11th to 20th	Day	78% 5% 7% 5% 3 1	1688
	21st to end	Day	83% 4 6% 5% 2 1	2442
January	1st to 10th	Night	82% 3 6% 5% 2	4726
	11th to 20th	Night	69% 6% 11% 8% 4 1	4740
	21st to end	Night	85% 3 5% 6% 2	4935
February	1st to 10th	Night	75% 5% 6% 7% 6% 1	2586
	11th to 20th	Night	66% 4 11% 13% 6%	2274
	21st to end	Night	67% 5% 10% 11% 5% 2	1866
March	1st to 10th	Night	67% 5% 11% 12% 4	2134
	11th to 20th	Night	71% 5% 10% 8% 4 1	1980
	21st to end	Night	69% 6% 12% 9% 3	2178
April	1st to 10th	Night	69% 7% 13% 8% 3	1742
	11th to 20th	Night	67% 4 11% 12% 6%	1601
	21st to end	Night	65% 5% 12% 14% 2 1	1620
May	1st to 10th	Night	56% 10% 17% 14% 3	1526
	11th to 20th	Night	58% 10% 17% 12% 3	1239
	21st to end	Night	62% 9% 18% 8% 3	1358
June	1st to 10th	Night	61% 7% 18% 11% 3 1	1260
	11th to 20th	Night	65% 8% 17% 8% 2	1260
	21st to end	Night	55% 9% 20% 12% 3	1260
July	1st to 10th	Night	51% 11% 18% 16% 4	1225
	11th to 20th	Night	50% 13% 22% 13% 3	1218
	21st to end	Night	44% 14% 23% 14% 5%	1306
August	1st to 10th	Night	52% 12% 18% 15% 3	1463
	11th to 20th	Night	46% 13% 20% 17% 3 1	1602
	21st to end	Night	59% 11% 18% 10% 2	1782
September	1st to 10th	Night	57% 9% 19% 12% 2 1	1710
	11th to 20th	Night	53% 10% 14% 17% 7%	1980
	21st to end	Night	65% 7% 13% 11% 3 1	1980
October	1st to 10th	Night	63% 6% 14% 14% 3 1	2101
	11th to 20th	Night	69% 8% 12% 8% 3	2224
	21st to end	Night	70% 5% 10% 10% 5%	2574
November	1st to 10th	Night	77% 5% 7% 7% 4	2558
	11th to 20th	Night	75% 6% 8% 6% 5% 1	2660
	21st to end	Night	74% 4 8% 8% 4 2	2835
December	1st to 10th	Night	68% 4 11% 11% 5% 1	2850
	11th to 20th	Night	78% 5% 6% 7% 4 1	3516
	21st to end	Night	81% 5% 7% 5% 2 1	5214

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% 15% 6% 4	180
	11th to 20th	Day	48% 12% 18% 14% 6% 2	180
	21st to end	Day	43% 9% 19% 16% 10% 3	365
February	1st to 10th	Day	45% 10% 19% 18% 7% 1	368
	11th to 20th	Day	38% 12% 20% 18% 10% 2	335
	21st to end	Day	33% 17% 24% 17% 8% 2	280
March	1st to 10th	Day	33% 10% 20% 17% 18% 3	352
	11th to 20th	Day	34% 13% 20% 18% 11% 3	420
	21st to end	Day	40% 8% 16% 20% 11% 5%	462
April	1st to 10th	Day	36% 10% 22% 20% 10% 3	420
	11th to 20th	Day	30% 9% 21% 17% 17% 6%	412
	21st to end	Day	33% 9% 17% 22% 12% 6%	420
May	1st to 10th	Day	31% 7% 17% 26% 15% 5%	423
	11th to 20th	Day	28% 4 20% 28% 16% 4	625
	21st to end	Day	26% 7% 20% 29% 15% 3	680
June	1st to 10th	Day	35% 5% 18% 25% 13% 4	630
	11th to 20th	Day	32% 8% 19% 25% 14% 3	630
	21st to end	Day	26% 5% 15% 28% 21% 5%	630
July	1st to 10th	Day	19% 4 15% 27% 27% 8%	621
	11th to 20th	Day	20% 3 17% 31% 22% 6%	618
	21st to end	Day	19% 4 14% 29% 26% 10%	684
August	1st to 10th	Day	18% 3 13% 26% 30% 11%	586
	11th to 20th	Day	20% 7% 13% 27% 27% 7%	437
	21st to end	Day	25% 6% 18% 23% 22% 5%	495
September	1st to 10th	Day	30% 4 13% 25% 21% 7%	450
	11th to 20th	Day	30% 7% 14% 20% 20% 10%	450
	21st to end	Day	34% 8% 15% 21% 15% 6%	450
October	1st to 10th	Day	34% 9% 15% 18% 16% 7%	450
	11th to 20th	Day	39% 7% 19% 19% 12% 5%	417
	21st to end	Day	36% 9% 23% 16% 11% 5%	396
November	1st to 10th	Day	40% 13% 17% 17% 11% 2	212
	11th to 20th	Day	37% 9% 22% 13% 12% 7%	180
	21st to end	Day	46% 11% 14% 11% 11% 7%	180
December	1st to 10th	Day	43% 5% 15% 22% 11% 4	180
	11th to 20th	Day	39% 9% 19% 18% 11% 3	180
	21st to end	Day	46% 9% 19% 19% 5% 2	198
January	1st to 10th	Night	47% 10% 19% 14% 8% 2	850
	11th to 20th	Night	46% 9% 14% 20% 10% 1	850
	21st to end	Night	46% 6% 15% 16% 13% 4	935
February	1st to 10th	Night	47% 10% 18% 18% 7% 1	817
	11th to 20th	Night	36% 8% 18% 21% 15% 2	704
	21st to end	Night	39% 12% 15% 19% 11% 4	592
March	1st to 10th	Night	32% 10% 20% 19% 15% 3	720
	11th to 20th	Night	37% 8% 19% 21% 13% 2	720
	21st to end	Night	35% 9% 15% 21% 15% 5%	792
April	1st to 10th	Night	33% 9% 14% 24% 14% 6%	576
	11th to 20th	Night	33% 5% 16% 24% 18% 5%	533
	21st to end	Night	32% 5% 16% 28% 16% 4	540
May	1st to 10th	Night	28% 6% 11% 26% 25% 5%	450
	11th to 20th	Night	26% 5% 9% 26% 31% 5%	354
	21st to end	Night	26% 7% 10% 31% 22% 5%	389
June	1st to 10th	Night	26% 6% 11% 26% 25% 7%	360
	11th to 20th	Night	27% 6% 13% 25% 24% 5%	360
	21st to end	Night	21% 5% 10% 29% 27% 8%	360
July	1st to 10th	Night	19% 5% 9% 25% 30% 13%	350
	11th to 20th	Night	18% 5% 9% 23% 33% 12%	348
	21st to end	Night	16% 5% 6% 26% 32% 16%	398
August	1st to 10th	Night	18% 5% 7% 18% 32% 20%	537
	11th to 20th	Night	16% 5% 9% 24% 34% 12%	534
	21st to end	Night	25% 6% 10% 26% 28% 6%	594
September	1st to 10th	Night	25% 5% 9% 24% 27% 9%	604
	11th to 20th	Night	23% 5% 10% 21% 23% 18%	720
	21st to end	Night	36% 4 12% 23% 20% 6%	720
October	1st to 10th	Night	37% 6% 12% 20% 17% 8%	720
	11th to 20th	Night	41% 3 13% 21% 15% 7%	720
	21st to end	Night	40% 7% 18% 19% 14% 4	792
November	1st to 10th	Night	43% 10% 14% 22% 10% 1	740
	11th to 20th	Night	43% 8% 18% 19% 10% 3	760
	21st to end	Night	43% 8% 16% 19% 10% 5%	843
December	1st to 10th	Night	39% 9% 16% 20% 12% 4	850
	11th to 20th	Night	44% 6% 20% 17% 11% 2	850
	21st to end	Night	43% 11% 21% 20% 5% 1	935

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