Port-Cartier
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port-Cartier clear sky chart from 2005-11-06 to 2024-01-16.

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	20% 9% 3 6% 5% 3 5% 5% 5% 6% 33%	74655
	Night	19% 10% 4 7% 5% 3 4 4 5% 6% 33%	75159
Transparency	Day	52% 6% 12% 19% 10% 1	74338
	Night	53% 5% 10% 20% 11% 1	75011
Seeing	Day	26% 11% 28% 23% 10% 2	15027
	Night	24% 9% 27% 29% 10% 1	22875

By Month

Percentage Cloud Cover NE (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	14% 17% 6% 9% 5% 3 4 5% 5% 5% 27%	1327
	11th to 20th	Day	15% 12% 5% 8% 6% 3 3 2 4 4 36%	1295
	21st to end	Day	9% 12% 5% 8% 7% 3 4 4 5% 6% 35%	1562
February	1st to 10th	Day	7% 9% 5% 9% 9% 4 5% 5% 5% 6% 36%	1548
	11th to 20th	Day	11% 16% 5% 9% 6% 3 5% 5% 5% 6% 29%	1573
	21st to end	Day	8% 12% 5% 9% 7% 3 6% 5% 5% 7% 33%	1386
March	1st to 10th	Day	13% 13% 5% 7% 6% 2 4 5% 4 7% 32%	1845
	11th to 20th	Day	15% 13% 5% 7% 6% 3 4 4 4 4 34%	1980
	21st to end	Day	15% 15% 5% 7% 5% 3 4 4 4 6% 33%	2178
April	1st to 10th	Day	21% 11% 4 7% 7% 3 5% 4 5% 5% 27%	2208
	11th to 20th	Day	15% 11% 4 7% 5% 3 4 4 5% 7% 35%	2312
	21st to end	Day	24% 10% 3 5% 4 3 4 4 4 5% 34%	2340
May	1st to 10th	Day	25% 8% 3 6% 6% 3 6% 4 4 5% 31%	2430
	11th to 20th	Day	22% 8% 3 6% 4 3 5% 4 5% 7% 33%	2609
	21st to end	Day	23% 6% 3 5% 5% 3 5% 5% 5% 6% 34%	2919
June	1st to 10th	Day	26% 8% 3 5% 5% 4 5% 4 5% 6% 29%	2700
	11th to 20th	Day	21% 6% 3 5% 5% 4 5% 5% 6% 7% 33%	2700
	21st to end	Day	28% 7% 3 4 5% 3 5% 5% 5% 7% 28%	2700
July	1st to 10th	Day	22% 6% 3 5% 5% 3 5% 6% 6% 7% 32%	2700
	11th to 20th	Day	17% 6% 2 5% 5% 4 5% 7% 7% 9% 33%	2700
	21st to end	Day	20% 6% 3 5% 5% 4 6% 7% 7% 8% 30%	2937
August	1st to 10th	Day	21% 6% 2 6% 6% 4 6% 6% 6% 8% 28%	2399
	11th to 20th	Day	21% 6% 2 5% 5% 3 5% 5% 7% 7% 34%	2304
	21st to end	Day	17% 6% 2 7% 6% 5% 4 6% 7% 7% 33%	2574
September	1st to 10th	Day	21% 5% 2 6% 5% 3 5% 5% 6% 7% 35%	2228
	11th to 20th	Day	27% 5% 2 4 4 2 4 3 4 6% 38%	1980
	21st to end	Day	22% 6% 3 5% 5% 3 3 4 5% 7% 38%	1980
October	1st to 10th	Day	19% 7% 2 6% 4 3 5% 5% 5% 6% 37%	1827
	11th to 20th	Day	26% 8% 3 5% 5% 3 4 5% 5% 6% 28%	1777
	21st to end	Day	27% 8% 3 6% 7% 3 3 4 4 5% 28%	1782
November	1st to 10th	Day	20% 10% 3 5% 5% 3 5% 5% 6% 6% 31%	1495
	11th to 20th	Day	20% 13% 4 6% 5% 3 5% 5% 4 6% 29%	1520
	21st to end	Day	19% 15% 4 7% 6% 4 4 3 3 4 30%	1411
December	1st to 10th	Day	18% 12% 4 7% 5% 4 5% 5% 6% 5% 31%	1330
	11th to 20th	Day	17% 13% 4 8% 5% 3 2 2 3 5% 38%	1668
	21st to end	Day	14% 13% 5% 6% 5% 3 4 3 4 6% 36%	2431
January	1st to 10th	Night	14% 15% 4 9% 6% 3 4 4 5% 5% 30%	2838
	11th to 20th	Night	16% 13% 5% 8% 5% 3 3 4 4 5% 33%	2787
	21st to end	Night	9% 12% 6% 9% 6% 3 4 3 5% 6% 36%	2792
February	1st to 10th	Night	9% 11% 6% 10% 7% 3 5% 4 5% 5% 36%	2411
	11th to 20th	Night	12% 17% 5% 9% 5% 3 5% 4 5% 6% 30%	2273
	21st to end	Night	12% 11% 6% 8% 6% 4 5% 5% 5% 5% 32%	1866
March	1st to 10th	Night	12% 14% 5% 8% 7% 3 5% 4 4 6% 32%	2102
	11th to 20th	Night	15% 13% 5% 7% 6% 3 4 4 5% 6% 33%	1979
	21st to end	Night	14% 15% 4 7% 5% 3 4 4 4 5% 34%	2178
April	1st to 10th	Night	23% 10% 4 8% 5% 4 5% 4 4 4 29%	1747
	11th to 20th	Night	20% 9% 3 6% 5% 3 4 4 4 5% 38%	1598
	21st to end	Night	25% 9% 3 5% 4 3 4 3 3 5% 37%	1620
May	1st to 10th	Night	27% 8% 3 5% 5% 3 4 5% 4 6% 30%	1530
	11th to 20th	Night	22% 9% 3 7% 5% 3 5% 5% 5% 5% 32%	1300
	21st to end	Night	22% 8% 4 5% 5% 3 5% 4 5% 6% 32%	1356
June	1st to 10th	Night	26% 8% 2 5% 5% 3 5% 4 5% 6% 31%	1260
	11th to 20th	Night	22% 6% 2 4 4 3 6% 6% 5% 6% 35%	1260
	21st to end	Night	28% 7% 4 6% 4 2 4 4 5% 7% 29%	1260
July	1st to 10th	Night	22% 8% 3 5% 5% 2 5% 4 6% 9% 30%	1260
	11th to 20th	Night	20% 7% 2 4 5% 5% 5% 6% 5% 7% 33%	1260
	21st to end	Night	20% 5% 3 6% 6% 3 5% 5% 6% 7% 33%	1378
August	1st to 10th	Night	20% 8% 3 6% 5% 3 4 6% 6% 7% 32%	1520
	11th to 20th	Night	21% 8% 3 6% 6% 3 5% 6% 5% 7% 31%	1596
	21st to end	Night	18% 6% 3 5% 6% 3 5% 6% 6% 6% 35%	1782
September	1st to 10th	Night	22% 6% 2 5% 4 2 5% 4 6% 5% 38%	1730
	11th to 20th	Night	23% 6% 3 4 4 2 3 4 4 6% 41%	1980
	21st to end	Night	21% 5% 2 4 5% 2 4 4 5% 6% 42%	1980
October	1st to 10th	Night	22% 7% 3 6% 5% 3 3 4 5% 6% 38%	2132
	11th to 20th	Night	27% 8% 3 6% 5% 3 3 4 4 5% 30%	2182
	21st to end	Night	26% 8% 3 6% 5% 3 5% 4 4 5% 31%	2574
November	1st to 10th	Night	25% 9% 3 6% 5% 3 4 5% 5% 5% 31%	2583
	11th to 20th	Night	22% 11% 4 6% 5% 3 4 5% 4 5% 29%	2660
	21st to end	Night	19% 15% 5% 7% 6% 3 3 4 5% 5% 27%	2768
December	1st to 10th	Night	20% 13% 4 7% 5% 2 4 4 5% 6% 31%	2850
	11th to 20th	Night	23% 13% 5% 6% 4 2 3 3 3 5% 35%	3531
	21st to end	Night	13% 12% 5% 9% 7% 4 5% 5% 5% 5% 31%	5236

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	60% 3 9% 18% 9% 1	1328
	11th to 20th	Day	52% 5% 9% 22% 10% 2	1295
	21st to end	Day	50% 3 10% 22% 14% 2	1562
February	1st to 10th	Day	49% 4 12% 20% 12% 3	1548
	11th to 20th	Day	56% 5% 11% 19% 9% 1	1581
	21st to end	Day	50% 5% 6% 25% 11% 2	1386
March	1st to 10th	Day	53% 4 11% 19% 12% 2	1849
	11th to 20th	Day	54% 4 9% 16% 14% 3	1980
	21st to end	Day	55% 4 9% 14% 15% 4	2178
April	1st to 10th	Day	59% 5% 8% 13% 13% 2	2208
	11th to 20th	Day	49% 4 10% 22% 14% 2	2312
	21st to end	Day	53% 4 10% 18% 13% 2	2340
May	1st to 10th	Day	57% 3 10% 19% 9% 1	2430
	11th to 20th	Day	52% 5% 10% 20% 11% 1	2613
	21st to end	Day	51% 5% 9% 22% 11% 1	2919
June	1st to 10th	Day	56% 5% 9% 18% 10% 2	2700
	11th to 20th	Day	49% 8% 14% 18% 11% 1	2700
	21st to end	Day	55% 7% 11% 18% 8% 1	2700
July	1st to 10th	Day	50% 8% 15% 18% 8% 1	2625
	11th to 20th	Day	46% 8% 14% 21% 11%	2619
	21st to end	Day	50% 9% 17% 19% 5%	2773
August	1st to 10th	Day	53% 9% 20% 15% 4	2385
	11th to 20th	Day	49% 8% 17% 20% 5%	2304
	21st to end	Day	50% 7% 18% 21% 5%	2574
September	1st to 10th	Day	48% 6% 16% 22% 8%	2228
	11th to 20th	Day	48% 6% 14% 25% 7%	1980
	21st to end	Day	47% 6% 11% 26% 10%	1980
October	1st to 10th	Day	47% 6% 15% 20% 11% 1	1827
	11th to 20th	Day	57% 6% 14% 18% 5%	1777
	21st to end	Day	60% 4 10% 16% 9% 1	1782
November	1st to 10th	Day	53% 7% 14% 17% 9%	1495
	11th to 20th	Day	58% 6% 13% 17% 6%	1520
	21st to end	Day	58% 5% 11% 16% 9%	1411
December	1st to 10th	Day	54% 7% 13% 21% 5% 1	1330
	11th to 20th	Day	52% 4 8% 23% 12%	1668
	21st to end	Day	49% 5% 11% 20% 10% 5%	2431
January	1st to 10th	Night	57% 4 10% 19% 10% 1	2838
	11th to 20th	Night	54% 4 9% 21% 10% 2	2787
	21st to end	Night	50% 3 8% 21% 17% 1	2792
February	1st to 10th	Night	51% 4 8% 20% 14% 3	2411
	11th to 20th	Night	56% 4 9% 18% 12% 1	2276
	21st to end	Night	52% 4 6% 22% 14% 1	1866
March	1st to 10th	Night	55% 3 8% 19% 14% 1	2111
	11th to 20th	Night	52% 4 7% 21% 14% 2	1980
	21st to end	Night	53% 3 7% 17% 16% 3	2178
April	1st to 10th	Night	58% 5% 6% 13% 16% 3	1747
	11th to 20th	Night	48% 5% 9% 19% 15% 4	1598
	21st to end	Night	52% 5% 8% 16% 17% 2	1620
May	1st to 10th	Night	56% 5% 9% 19% 11% 1	1530
	11th to 20th	Night	53% 5% 10% 17% 14% 1	1301
	21st to end	Night	52% 7% 8% 20% 12% 2	1357
June	1st to 10th	Night	53% 5% 9% 18% 14% 2	1260
	11th to 20th	Night	48% 6% 13% 18% 12% 2	1260
	21st to end	Night	56% 6% 10% 18% 10%	1260
July	1st to 10th	Night	49% 8% 15% 20% 8%	1225
	11th to 20th	Night	48% 7% 11% 22% 11% 1	1218
	21st to end	Night	47% 10% 14% 21% 8%	1301
August	1st to 10th	Night	50% 9% 18% 17% 6%	1510
	11th to 20th	Night	51% 7% 17% 19% 6% 1	1596
	21st to end	Night	47% 7% 15% 24% 7%	1782
September	1st to 10th	Night	47% 6% 11% 28% 8% 1	1730
	11th to 20th	Night	46% 5% 14% 25% 8% 1	1980
	21st to end	Night	44% 5% 12% 28% 11%	1980
October	1st to 10th	Night	48% 6% 12% 23% 11% 1	2132
	11th to 20th	Night	56% 5% 12% 20% 7%	2182
	21st to end	Night	57% 4 11% 20% 6% 1	2574
November	1st to 10th	Night	54% 7% 12% 18% 9% 1	2583
	11th to 20th	Night	56% 5% 12% 19% 7%	2660
	21st to end	Night	61% 5% 10% 15% 9%	2768
December	1st to 10th	Night	55% 5% 12% 20% 8%	2850
	11th to 20th	Night	54% 4 7% 23% 12%	3532
	21st to end	Night	53% 6% 12% 15% 9% 4	5236

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	23% 9% 29% 22% 15% 2	180
	11th to 20th	Day	20% 12% 27% 24% 15% 2	170
	21st to end	Day	17% 14% 26% 28% 11% 3	176
February	1st to 10th	Day	14% 14% 36% 28% 6% 2	268
	11th to 20th	Day	16% 13% 39% 25% 7% 1	336
	21st to end	Day	16% 11% 37% 26% 9% 2	304
March	1st to 10th	Day	22% 14% 28% 26% 9% 2	420
	11th to 20th	Day	24% 9% 30% 25% 9% 2	420
	21st to end	Day	25% 16% 29% 22% 7% 2	462
April	1st to 10th	Day	27% 17% 27% 21% 6% 1	420
	11th to 20th	Day	25% 10% 33% 22% 8% 2	412
	21st to end	Day	31% 12% 28% 18% 9% 2	420
May	1st to 10th	Day	29% 9% 28% 25% 8% 2	513
	11th to 20th	Day	26% 10% 30% 20% 12% 2	624
	21st to end	Day	30% 14% 26% 22% 8% 1	680
June	1st to 10th	Day	32% 9% 30% 21% 9% 1	630
	11th to 20th	Day	28% 10% 25% 22% 11% 3	630
	21st to end	Day	31% 8% 26% 24% 8% 2	630
July	1st to 10th	Day	26% 10% 24% 26% 11% 3	620
	11th to 20th	Day	21% 8% 28% 29% 12% 2	618
	21st to end	Day	25% 5% 24% 29% 14% 2	681
August	1st to 10th	Day	26% 6% 26% 29% 10% 4	446
	11th to 20th	Day	23% 8% 27% 27% 11% 3	439
	21st to end	Day	21% 9% 29% 25% 13% 3	495
September	1st to 10th	Day	26% 13% 28% 20% 10% 2	450
	11th to 20th	Day	32% 8% 31% 20% 7% 3	450
	21st to end	Day	24% 15% 28% 21% 9% 3	450
October	1st to 10th	Day	21% 16% 30% 21% 10% 2	373
	11th to 20th	Day	33% 11% 25% 18% 11% 3	360
	21st to end	Day	35% 11% 22% 19% 11% 2	396
November	1st to 10th	Day	31% 14% 28% 20% 6% 1	365
	11th to 20th	Day	29% 10% 29% 21% 9% 2	370
	21st to end	Day	26% 18% 29% 19% 8%	261
December	1st to 10th	Day	21% 8% 23% 31% 13% 4	180
	11th to 20th	Day	18% 20% 31% 21% 8% 1	180
	21st to end	Day	24% 20% 25% 24% 6% 2	198
January	1st to 10th	Night	20% 7% 33% 29% 10%	850
	11th to 20th	Night	23% 10% 30% 30% 7%	829
	21st to end	Night	16% 10% 32% 33% 8% 1	800
February	1st to 10th	Night	14% 13% 36% 28% 9% 1	720
	11th to 20th	Night	21% 12% 32% 24% 9% 1	703
	21st to end	Night	18% 11% 32% 28% 9% 3	592
March	1st to 10th	Night	20% 11% 29% 30% 9% 1	720
	11th to 20th	Night	20% 12% 29% 30% 9%	720
	21st to end	Night	21% 11% 30% 27% 9% 1	792
April	1st to 10th	Night	28% 11% 28% 26% 7%	612
	11th to 20th	Night	23% 11% 28% 28% 9% 1	534
	21st to end	Night	30% 7% 24% 28% 9% 1	540
May	1st to 10th	Night	30% 5% 24% 32% 7% 1	540
	11th to 20th	Night	25% 8% 23% 33% 11% 1	416
	21st to end	Night	25% 9% 28% 31% 7%	389
June	1st to 10th	Night	28% 6% 22% 35% 9%	360
	11th to 20th	Night	26% 3 20% 34% 17% 1	360
	21st to end	Night	29% 4 21% 34% 9% 2	360
July	1st to 10th	Night	26% 5% 23% 30% 15% 1	350
	11th to 20th	Night	24% 4 15% 41% 16% 1	348
	21st to end	Night	21% 4 15% 41% 19% 1	394
August	1st to 10th	Night	25% 2 17% 34% 20% 2	446
	11th to 20th	Night	22% 4 17% 39% 17% 1	532
	21st to end	Night	21% 5% 20% 37% 16% 2	594
September	1st to 10th	Night	25% 5% 25% 33% 12% 1	542
	11th to 20th	Night	27% 5% 25% 30% 11% 2	720
	21st to end	Night	25% 8% 26% 31% 10% 1	720
October	1st to 10th	Night	27% 9% 29% 26% 9% 1	720
	11th to 20th	Night	31% 7% 25% 23% 14% 1	720
	21st to end	Night	31% 7% 25% 27% 9% 1	792
November	1st to 10th	Night	31% 10% 28% 24% 6%	825
	11th to 20th	Night	27% 11% 28% 25% 9% 1	850
	21st to end	Night	27% 9% 30% 26% 8%	850
December	1st to 10th	Night	26% 10% 26% 26% 10% 1	850
	11th to 20th	Night	24% 13% 32% 23% 6%	850
	21st to end	Night	23% 10% 33% 24% 8% 1	935

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