Centre écologique de Port-au-Saumon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Centre écologique de Port-au-Saumon clear sky chart from 2005-11-06 to 2024-03-23.

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	16% 9% 4 7% 6% 4 5% 5% 5% 7% 33%	78239
	Night	16% 10% 4 7% 6% 4 5% 5% 5% 6% 32%	81648
Transparency	Day	49% 9% 15% 19% 8% 1	77934
	Night	54% 9% 13% 17% 8% 1	81488
Seeing	Day	21% 14% 31% 23% 9% 2	14691
	Night	22% 10% 31% 27% 8% 1	23092

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	13% 14% 5% 9% 8% 3 5% 4 5% 6% 27%	2314
	11th to 20th	Day	11% 11% 5% 9% 10% 5% 6% 6% 6% 6% 25%	2520
	21st to end	Day	7% 10% 4 8% 9% 5% 7% 7% 6% 6% 31%	2772
February	1st to 10th	Day	7% 13% 6% 7% 10% 6% 7% 7% 7% 6% 25%	1558
	11th to 20th	Day	10% 12% 5% 11% 9% 4 5% 6% 5% 5% 26%	1752
	21st to end	Day	11% 10% 3 9% 7% 5% 6% 6% 6% 7% 31%	1570
March	1st to 10th	Day	13% 11% 6% 8% 6% 4 7% 5% 5% 5% 30%	1897
	11th to 20th	Day	13% 13% 6% 8% 7% 3 5% 4 4 6% 31%	2040
	21st to end	Day	13% 13% 5% 8% 7% 3 5% 4 4 6% 33%	2268
April	1st to 10th	Day	19% 12% 4 8% 6% 3 5% 4 5% 5% 27%	2160
	11th to 20th	Day	18% 7% 2 6% 7% 3 4 4 4 6% 38%	2284
	21st to end	Day	21% 11% 3 6% 5% 3 4 4 4 5% 34%	2340
May	1st to 10th	Day	19% 8% 3 6% 6% 3 4 5% 5% 7% 34%	2358
	11th to 20th	Day	17% 7% 4 6% 5% 4 5% 5% 5% 6% 37%	2486
	21st to end	Day	18% 5% 3 6% 6% 4 5% 5% 5% 8% 36%	2919
June	1st to 10th	Day	19% 7% 3 6% 6% 4 5% 6% 6% 7% 31%	2700
	11th to 20th	Day	19% 5% 3 6% 5% 3 5% 4 6% 7% 36%	2700
	21st to end	Day	19% 8% 3 6% 6% 4 5% 5% 6% 8% 30%	2700
July	1st to 10th	Day	15% 6% 2 6% 6% 3 6% 7% 8% 11% 32%	2700
	11th to 20th	Day	12% 6% 3 6% 6% 4 7% 6% 7% 9% 33%	2580
	21st to end	Day	13% 5% 3 6% 6% 3 6% 6% 7% 9% 35%	2744
August	1st to 10th	Day	14% 5% 3 7% 7% 5% 7% 8% 7% 10% 29%	2463
	11th to 20th	Day	12% 7% 3 6% 5% 4 5% 4 7% 10% 38%	2304
	21st to end	Day	13% 5% 2 5% 5% 4 5% 5% 6% 9% 39%	2561
September	1st to 10th	Day	13% 7% 2 5% 6% 3 5% 4 6% 8% 40%	2138
	11th to 20th	Day	14% 6% 2 5% 5% 3 4 4 5% 7% 45%	1980
	21st to end	Day	17% 5% 3 5% 4 3 4 5% 6% 8% 41%	1980
October	1st to 10th	Day	17% 7% 2 6% 5% 4 4 4 6% 6% 38%	1948
	11th to 20th	Day	22% 7% 3 6% 5% 4 5% 5% 6% 7% 30%	1672
	21st to end	Day	24% 12% 4 6% 6% 3 5% 4 4 5% 27%	1782
November	1st to 10th	Day	16% 10% 4 8% 7% 5% 5% 5% 6% 6% 30%	1671
	11th to 20th	Day	17% 12% 5% 8% 6% 3 5% 5% 5% 7% 26%	1585
	21st to end	Day	18% 13% 5% 8% 7% 3 4 4 4 6% 27%	1364
December	1st to 10th	Day	19% 14% 5% 8% 7% 3 6% 5% 4 6% 23%	1330
	11th to 20th	Day	20% 12% 4 9% 7% 3 4 3 3 4 30%	1668
	21st to end	Day	20% 12% 4 7% 6% 3 4 3 3 4 35%	2431
January	1st to 10th	Night	11% 15% 6% 10% 9% 4 6% 5% 5% 5% 23%	4621
	11th to 20th	Night	11% 13% 5% 11% 8% 5% 6% 6% 5% 6% 24%	4440
	21st to end	Night	6% 11% 6% 9% 9% 6% 7% 6% 6% 8% 27%	4884
February	1st to 10th	Night	9% 12% 5% 8% 7% 4 6% 6% 6% 7% 30%	2622
	11th to 20th	Night	9% 15% 6% 12% 9% 4 5% 4 5% 5% 26%	2314
	21st to end	Night	12% 11% 5% 9% 6% 3 5% 4 5% 7% 32%	1884
March	1st to 10th	Night	12% 14% 6% 8% 5% 3 5% 5% 5% 6% 32%	2270
	11th to 20th	Night	14% 15% 4 8% 6% 4 4 5% 4 5% 30%	2138
	21st to end	Night	13% 14% 4 6% 4 4 4 5% 5% 6% 34%	2129
April	1st to 10th	Night	20% 12% 5% 8% 6% 3 4 4 4 4 29%	1800
	11th to 20th	Night	17% 9% 3 7% 6% 3 5% 4 5% 6% 35%	1625
	21st to end	Night	24% 10% 4 5% 4 3 3 4 5% 5% 33%	1620
May	1st to 10th	Night	23% 9% 3 6% 5% 2 4 5% 4 5% 32%	1619
	11th to 20th	Night	22% 7% 3 5% 4 3 4 5% 5% 5% 39%	1405
	21st to end	Night	20% 8% 3 5% 6% 3 4 5% 5% 6% 36%	1356
June	1st to 10th	Night	18% 7% 4 8% 6% 4 5% 5% 7% 7% 30%	1260
	11th to 20th	Night	16% 6% 3 6% 5% 3 4 6% 6% 7% 39%	1260
	21st to end	Night	22% 7% 3 6% 6% 3 5% 5% 5% 7% 31%	1260
July	1st to 10th	Night	16% 6% 3 6% 5% 4 5% 6% 5% 9% 36%	1260
	11th to 20th	Night	13% 5% 4 7% 6% 4 6% 5% 7% 8% 36%	1376
	21st to end	Night	13% 6% 3 6% 6% 4 6% 6% 6% 8% 37%	1574
August	1st to 10th	Night	13% 5% 2 6% 6% 4 6% 4 7% 7% 39%	1457
	11th to 20th	Night	16% 6% 3 5% 7% 4 6% 6% 7% 9% 32%	1596
	21st to end	Night	13% 5% 3 5% 5% 3 5% 5% 5% 9% 43%	1793
September	1st to 10th	Night	15% 5% 2 5% 5% 3 5% 5% 6% 7% 42%	1821
	11th to 20th	Night	18% 7% 3 5% 5% 3 5% 4 4 6% 41%	1980
	21st to end	Night	16% 7% 3 5% 4 3 3 4 6% 5% 45%	1980
October	1st to 10th	Night	16% 6% 3 6% 5% 3 4 4 5% 6% 43%	2011
	11th to 20th	Night	24% 7% 2 5% 5% 4 5% 4 5% 6% 33%	2286
	21st to end	Night	23% 9% 3 6% 5% 3 4 4 5% 7% 32%	2574
November	1st to 10th	Night	16% 10% 4 8% 4 3 5% 5% 5% 8% 33%	2407
	11th to 20th	Night	19% 9% 4 6% 5% 3 6% 4 6% 7% 31%	2593
	21st to end	Night	17% 13% 4 8% 6% 4 5% 4 5% 6% 28%	2816
December	1st to 10th	Night	18% 15% 6% 9% 6% 3 6% 5% 4 5% 25%	2850
	11th to 20th	Night	20% 11% 5% 7% 7% 4 6% 5% 5% 5% 26%	3531
	21st to end	Night	18% 14% 4 8% 6% 3 5% 4 4 5% 28%	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	58% 11% 17% 12% 2	2315
	11th to 20th	Day	56% 8% 12% 19% 4 1	2520
	21st to end	Day	48% 11% 14% 16% 11%	2772
February	1st to 10th	Day	56% 7% 13% 14% 8% 2	1558
	11th to 20th	Day	59% 7% 12% 14% 8% 1	1760
	21st to end	Day	52% 7% 11% 19% 9% 2	1570
March	1st to 10th	Day	53% 8% 12% 15% 11% 2	1900
	11th to 20th	Day	55% 8% 11% 15% 9% 1	2040
	21st to end	Day	52% 6% 11% 20% 8% 3	2268
April	1st to 10th	Day	56% 6% 12% 14% 9% 2	2160
	11th to 20th	Day	46% 6% 12% 24% 10% 2	2284
	21st to end	Day	52% 6% 9% 18% 13% 2	2340
May	1st to 10th	Day	48% 8% 13% 17% 13% 2	2358
	11th to 20th	Day	45% 8% 12% 23% 11% 1	2490
	21st to end	Day	45% 10% 12% 22% 10% 1	2919
June	1st to 10th	Day	49% 10% 11% 19% 11% 1	2700
	11th to 20th	Day	44% 9% 16% 20% 11% 1	2700
	21st to end	Day	50% 10% 15% 16% 8% 1	2700
July	1st to 10th	Day	42% 10% 21% 20% 7%	2625
	11th to 20th	Day	43% 9% 18% 22% 7% 1	2501
	21st to end	Day	42% 11% 20% 20% 7%	2591
August	1st to 10th	Day	43% 13% 22% 18% 4	2449
	11th to 20th	Day	38% 10% 22% 22% 7%	2304
	21st to end	Day	38% 10% 21% 23% 8%	2561
September	1st to 10th	Day	39% 9% 18% 24% 10%	2138
	11th to 20th	Day	38% 7% 18% 25% 10% 1	1980
	21st to end	Day	41% 8% 16% 25% 10%	1980
October	1st to 10th	Day	44% 8% 17% 21% 9%	1948
	11th to 20th	Day	52% 9% 17% 18% 3	1672
	21st to end	Day	59% 9% 12% 16% 5%	1782
November	1st to 10th	Day	52% 10% 15% 19% 4 1	1671
	11th to 20th	Day	56% 10% 12% 16% 5%	1585
	21st to end	Day	60% 9% 13% 13% 4	1364
December	1st to 10th	Day	65% 9% 12% 10% 4	1330
	11th to 20th	Day	62% 6% 10% 16% 6%	1668
	21st to end	Day	56% 8% 14% 15% 5% 2	2431
January	1st to 10th	Night	63% 11% 11% 11% 4	4621
	11th to 20th	Night	58% 9% 13% 13% 7%	4440
	21st to end	Night	52% 10% 12% 17% 8%	4884
February	1st to 10th	Night	54% 8% 11% 17% 9% 1	2622
	11th to 20th	Night	61% 7% 11% 14% 7% 1	2317
	21st to end	Night	55% 7% 10% 18% 9% 1	1884
March	1st to 10th	Night	56% 6% 11% 19% 8% 1	2280
	11th to 20th	Night	58% 6% 11% 16% 8% 1	2139
	21st to end	Night	51% 8% 10% 19% 9% 2	2129
April	1st to 10th	Night	60% 5% 7% 14% 11% 2	1800
	11th to 20th	Night	50% 7% 10% 19% 12% 1	1625
	21st to end	Night	53% 6% 8% 18% 12% 2	1620
May	1st to 10th	Night	54% 6% 10% 16% 12% 2	1619
	11th to 20th	Night	48% 6% 11% 21% 13% 1	1406
	21st to end	Night	51% 7% 9% 19% 12% 1	1357
June	1st to 10th	Night	52% 8% 14% 18% 7% 1	1260
	11th to 20th	Night	44% 7% 14% 19% 13% 3	1260
	21st to end	Night	53% 8% 14% 16% 9%	1260
July	1st to 10th	Night	44% 10% 18% 22% 6%	1225
	11th to 20th	Night	42% 12% 17% 21% 7%	1332
	21st to end	Night	44% 12% 18% 19% 7%	1486
August	1st to 10th	Night	40% 13% 18% 25% 4	1447
	11th to 20th	Night	45% 11% 20% 17% 7%	1596
	21st to end	Night	40% 10% 17% 25% 8%	1793
September	1st to 10th	Night	41% 11% 14% 23% 10% 1	1821
	11th to 20th	Night	45% 7% 16% 21% 9% 1	1980
	21st to end	Night	41% 8% 13% 25% 12%	1980
October	1st to 10th	Night	46% 6% 13% 25% 10% 1	2011
	11th to 20th	Night	53% 10% 14% 19% 4	2286
	21st to end	Night	54% 8% 14% 17% 6%	2574
November	1st to 10th	Night	53% 9% 15% 16% 6%	2407
	11th to 20th	Night	54% 10% 14% 15% 6%	2593
	21st to end	Night	61% 9% 12% 12% 5%	2816
December	1st to 10th	Night	66% 8% 10% 12% 4	2850
	11th to 20th	Night	61% 11% 11% 13% 4	3532
	21st to end	Night	59% 10% 12% 13% 5%	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	22% 16% 40% 18% 2 1	180
	11th to 20th	Day	20% 19% 42% 13% 6% 1	180
	21st to end	Day	15% 17% 36% 21% 9% 2	198
February	1st to 10th	Day	21% 22% 35% 15% 6% 1	218
	11th to 20th	Day	18% 17% 41% 20% 3	408
	21st to end	Day	19% 18% 39% 18% 5% 1	382
March	1st to 10th	Day	24% 15% 32% 22% 6% 1	460
	11th to 20th	Day	23% 16% 32% 19% 9% 2	460
	21st to end	Day	22% 18% 31% 19% 7% 2	470
April	1st to 10th	Day	28% 17% 29% 19% 5% 1	420
	11th to 20th	Day	26% 18% 28% 19% 7% 2	412
	21st to end	Day	25% 16% 32% 19% 6% 2	420
May	1st to 10th	Day	26% 15% 29% 21% 7% 2	423
	11th to 20th	Day	18% 15% 32% 25% 9% 1	455
	21st to end	Day	22% 16% 35% 19% 8% 1	680
June	1st to 10th	Day	24% 13% 32% 21% 9% 1	630
	11th to 20th	Day	22% 10% 30% 24% 13% 1	630
	21st to end	Day	21% 7% 30% 31% 11% 1	630
July	1st to 10th	Day	16% 11% 32% 26% 12% 2	620
	11th to 20th	Day	15% 9% 30% 31% 13% 3	500
	21st to end	Day	14% 10% 29% 33% 13% 1	488
August	1st to 10th	Day	15% 11% 28% 29% 14% 3	446
	11th to 20th	Day	17% 7% 31% 27% 16% 2	439
	21st to end	Day	15% 13% 28% 25% 13% 6%	495
September	1st to 10th	Day	17% 10% 29% 26% 12% 5%	450
	11th to 20th	Day	21% 13% 27% 25% 11% 3	450
	21st to end	Day	19% 13% 28% 24% 11% 4	450
October	1st to 10th	Day	18% 14% 30% 25% 11% 3	434
	11th to 20th	Day	28% 17% 25% 19% 9% 1	360
	21st to end	Day	32% 15% 31% 17% 6% 1	396
November	1st to 10th	Day	29% 15% 31% 21% 4 1	365
	11th to 20th	Day	24% 16% 29% 21% 9% 1	370
	21st to end	Day	30% 19% 33% 17%	214
December	1st to 10th	Day	24% 19% 31% 17% 9% 1	180
	11th to 20th	Day	27% 20% 36% 13% 4 1	180
	21st to end	Day	26% 20% 31% 19% 5%	198
January	1st to 10th	Night	22% 12% 38% 21% 6% 1	814
	11th to 20th	Night	21% 13% 36% 24% 6%	760
	21st to end	Night	15% 8% 35% 34% 8% 1	836
February	1st to 10th	Night	17% 11% 42% 23% 7% 1	760
	11th to 20th	Night	21% 12% 38% 22% 6% 1	743
	21st to end	Night	21% 12% 33% 27% 6% 1	628
March	1st to 10th	Night	20% 10% 37% 27% 6% 1	760
	11th to 20th	Night	24% 12% 34% 21% 8%	760
	21st to end	Night	22% 13% 31% 26% 7%	801
April	1st to 10th	Night	30% 10% 30% 24% 6% 1	720
	11th to 20th	Night	24% 11% 31% 26% 7%	561
	21st to end	Night	31% 10% 25% 27% 7% 1	540
May	1st to 10th	Night	27% 8% 28% 29% 7% 1	539
	11th to 20th	Night	25% 9% 25% 31% 10% 1	354
	21st to end	Night	25% 12% 32% 21% 10%	389
June	1st to 10th	Night	20% 8% 29% 35% 7% 1	360
	11th to 20th	Night	19% 4 26% 36% 13% 1	360
	21st to end	Night	23% 7% 28% 33% 9%	360
July	1st to 10th	Night	19% 4 32% 34% 11% 1	350
	11th to 20th	Night	14% 5% 23% 43% 14% 1	348
	21st to end	Night	16% 4 20% 44% 15% 1	394
August	1st to 10th	Night	14% 5% 19% 44% 17% 1	383
	11th to 20th	Night	16% 4 23% 39% 17% 1	532
	21st to end	Night	15% 7% 24% 37% 16% 1	605
September	1st to 10th	Night	17% 7% 29% 34% 13% 2	720
	11th to 20th	Night	22% 8% 27% 29% 11% 3	720
	21st to end	Night	20% 7% 28% 33% 11% 1	720
October	1st to 10th	Night	21% 12% 28% 29% 9% 1	720
	11th to 20th	Night	28% 10% 28% 23% 10% 1	720
	21st to end	Night	27% 11% 32% 22% 7%	792
November	1st to 10th	Night	25% 15% 30% 23% 5%	740
	11th to 20th	Night	24% 16% 32% 19% 7% 1	818
	21st to end	Night	24% 16% 32% 23% 5% 1	850
December	1st to 10th	Night	28% 12% 32% 22% 6% 1	850
	11th to 20th	Night	26% 13% 35% 21% 4	850
	21st to end	Night	27% 15% 30% 21% 7% 1	935

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