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 2024-11-04.

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	15% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	101618
	Night	15% 11% 4 8% 5% 5% 5% 4 5% 6% 32%	97432
Transparency	Day	48% 9% 16% 19% 8% 1	105068
	Night	53% 9% 14% 17% 7% 1	102059
Seeing	Day	21% 14% 31% 23% 10% 2	15624
	Night	22% 10% 31% 27% 9% 1	23766

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	12% 15% 5% 10% 6% 4 6% 3 5% 6% 27%	2314
	11th to 20th	Day	11% 11% 5% 10% 9% 6% 6% 4 6% 6% 25%	2520
	21st to end	Day	7% 10% 4 10% 7% 6% 7% 6% 6% 6% 31%	2772
February	1st to 10th	Day	7% 14% 5% 8% 9% 7% 6% 6% 7% 6% 25%	1558
	11th to 20th	Day	10% 13% 5% 13% 8% 6% 5% 4 5% 5% 26%	1752
	21st to end	Day	11% 10% 4 9% 7% 7% 5% 5% 6% 7% 30%	1570
March	1st to 10th	Day	14% 11% 4 10% 6% 6% 5% 4 5% 6% 30%	3116
	11th to 20th	Day	14% 16% 5% 11% 6% 5% 5% 3 5% 6% 24%	3404
	21st to end	Day	13% 15% 4 9% 5% 4 3 3 4 5% 35%	3938
April	1st to 10th	Day	18% 13% 4 9% 5% 4 4 3 5% 5% 28%	2280
	11th to 20th	Day	17% 8% 3 8% 5% 5% 4 3 4 6% 37%	2413
	21st to end	Day	20% 11% 3 7% 4 4 4 3 4 6% 34%	2470
May	1st to 10th	Day	15% 8% 3 8% 6% 5% 4 4 5% 6% 35%	4138
	11th to 20th	Day	16% 8% 3 7% 5% 4 5% 4 5% 7% 37%	4420
	21st to end	Day	16% 7% 3 8% 6% 5% 5% 4 6% 8% 31%	5185
June	1st to 10th	Day	18% 8% 3 7% 5% 5% 4 5% 6% 7% 31%	2850
	11th to 20th	Day	18% 6% 3 7% 5% 4 5% 3 7% 7% 36%	2850
	21st to end	Day	20% 8% 2 7% 5% 5% 4 4 6% 7% 29%	2850
July	1st to 10th	Day	13% 5% 2 7% 5% 5% 5% 5% 8% 10% 35%	4760
	11th to 20th	Day	12% 6% 2 7% 5% 6% 6% 5% 7% 9% 35%	4542
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 8% 41%	4814
August	1st to 10th	Day	12% 5% 2 7% 5% 6% 7% 6% 8% 10% 31%	4339
	11th to 20th	Day	14% 7% 3 8% 5% 5% 5% 5% 7% 9% 33%	4045
	21st to end	Day	15% 5% 2 6% 4 4 5% 4 5% 8% 42%	4505
September	1st to 10th	Day	13% 7% 2 6% 5% 4 5% 3 6% 8% 41%	2256
	11th to 20th	Day	13% 5% 2 6% 4 4 4 3 6% 7% 47%	2090
	21st to end	Day	16% 6% 3 6% 4 4 4 3 6% 8% 40%	2090
October	1st to 10th	Day	18% 7% 2 7% 4 5% 4 4 6% 7% 37%	2056
	11th to 20th	Day	22% 8% 3 6% 4 5% 5% 4 7% 7% 31%	1764
	21st to end	Day	23% 12% 3 7% 5% 5% 5% 3 4 5% 28%	1881
November	1st to 10th	Day	16% 11% 3 9% 5% 6% 4 4 6% 6% 30%	1698
	11th to 20th	Day	17% 12% 4 9% 5% 5% 4 5% 6% 6% 26%	1585
	21st to end	Day	18% 15% 4 8% 6% 5% 4 3 5% 6% 27%	1364
December	1st to 10th	Day	18% 15% 5% 9% 6% 5% 5% 4 4 6% 23%	1330
	11th to 20th	Day	19% 13% 4 9% 7% 4 4 2 3 4 30%	1668
	21st to end	Day	20% 13% 4 9% 4 4 3 3 3 4 35%	2431
January	1st to 10th	Night	11% 16% 5% 12% 8% 6% 5% 4 5% 5% 23%	4621
	11th to 20th	Night	10% 14% 5% 13% 7% 6% 6% 4 5% 6% 24%	4440
	21st to end	Night	6% 11% 6% 11% 7% 7% 7% 4 6% 7% 27%	4884
February	1st to 10th	Night	8% 14% 4 9% 6% 5% 5% 5% 6% 6% 30%	2622
	11th to 20th	Night	9% 15% 5% 13% 8% 6% 4 4 5% 5% 25%	2314
	21st to end	Night	12% 12% 5% 10% 6% 4 5% 3 5% 7% 32%	1884
March	1st to 10th	Night	16% 14% 4 9% 5% 4 6% 4 5% 6% 27%	3724
	11th to 20th	Night	12% 19% 5% 11% 6% 5% 5% 4 4 5% 22%	3554
	21st to end	Night	17% 16% 5% 8% 3 4 3 3 5% 5% 31%	3690
April	1st to 10th	Night	19% 13% 5% 9% 5% 4 4 2 4 4 30%	1900
	11th to 20th	Night	17% 10% 3 8% 4 4 4 3 5% 6% 34%	1716
	21st to end	Night	23% 10% 3 6% 4 4 2 4 5% 5% 34%	1710
May	1st to 10th	Night	18% 8% 2 6% 5% 4 5% 4 5% 6% 35%	2819
	11th to 20th	Night	18% 9% 3 7% 5% 5% 5% 4 6% 6% 33%	2472
	21st to end	Night	17% 6% 3 6% 5% 4 5% 5% 7% 8% 34%	2401
June	1st to 10th	Night	18% 8% 3 8% 6% 5% 5% 4 7% 7% 30%	1330
	11th to 20th	Night	15% 6% 2 6% 5% 4 4 5% 6% 7% 39%	1330
	21st to end	Night	22% 8% 3 7% 5% 4 4 5% 5% 7% 30%	1330
July	1st to 10th	Night	12% 7% 2 8% 5% 5% 5% 5% 6% 8% 38%	2210
	11th to 20th	Night	14% 6% 3 7% 4 5% 5% 4 7% 8% 38%	2417
	21st to end	Night	11% 5% 2 6% 5% 5% 5% 4 6% 9% 44%	2739
August	1st to 10th	Night	17% 5% 2 8% 5% 6% 5% 4 6% 7% 35%	2559
	11th to 20th	Night	15% 5% 2 10% 7% 6% 7% 5% 7% 8% 28%	2782
	21st to end	Night	15% 6% 3 7% 5% 4 4 3 4 7% 43%	3149
September	1st to 10th	Night	15% 5% 2 6% 5% 4 4 4 6% 7% 43%	1923
	11th to 20th	Night	17% 7% 2 5% 4 4 5% 3 4 6% 42%	2090
	21st to end	Night	15% 7% 3 7% 4 4 3 3 6% 5% 44%	2090
October	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 5% 5% 42%	2123
	11th to 20th	Night	23% 7% 2 5% 4 5% 4 4 5% 6% 34%	2413
	21st to end	Night	22% 9% 3 6% 4 4 4 4 5% 7% 33%	2717
November	1st to 10th	Night	16% 11% 3 8% 4 4 4 4 5% 8% 33%	2453
	11th to 20th	Night	18% 10% 3 7% 5% 4 5% 4 6% 6% 31%	2593
	21st to end	Night	17% 14% 4 8% 5% 5% 5% 3 5% 5% 28%	2816
December	1st to 10th	Night	18% 16% 5% 10% 5% 4 5% 4 4 5% 24%	2850
	11th to 20th	Night	19% 12% 4 8% 6% 5% 5% 4 5% 5% 26%	3531
	21st to end	Night	18% 15% 4 9% 5% 4 5% 3 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	52% 11% 14% 12% 8% 3	3119
	11th to 20th	Day	59% 10% 13% 11% 6% 1	3404
	21st to end	Day	52% 6% 9% 19% 10% 4	3938
April	1st to 10th	Day	55% 6% 12% 15% 9% 3	2280
	11th to 20th	Day	46% 7% 12% 23% 9% 2	2413
	21st to end	Day	51% 7% 9% 18% 13% 2	2470
May	1st to 10th	Day	45% 10% 16% 18% 11% 1	4152
	11th to 20th	Day	43% 11% 17% 21% 7%	4424
	21st to end	Day	44% 11% 14% 20% 9% 1	5185
June	1st to 10th	Day	49% 9% 11% 20% 10% 1	2850
	11th to 20th	Day	44% 8% 17% 20% 11% 1	2850
	21st to end	Day	50% 9% 15% 17% 8% 1	2850
July	1st to 10th	Day	43% 8% 20% 23% 7%	4685
	11th to 20th	Day	44% 7% 24% 21% 4	4463
	21st to end	Day	38% 9% 23% 22% 8%	4661
August	1st to 10th	Day	44% 11% 20% 18% 7%	4325
	11th to 20th	Day	46% 8% 22% 20% 4	4084
	21st to end	Day	41% 7% 21% 19% 12%	4505
September	1st to 10th	Day	38% 8% 18% 25% 11%	2256
	11th to 20th	Day	37% 7% 18% 27% 10% 1	2090
	21st to end	Day	41% 8% 16% 25% 9%	2090
October	1st to 10th	Day	52% 7% 16% 19% 5%	3420
	11th to 20th	Day	49% 7% 19% 22% 2	2902
	21st to end	Day	48% 7% 18% 20% 7%	3081
November	1st to 10th	Day	51% 10% 16% 19% 4 1	1698
	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	58% 7% 11% 16% 6% 1	3734
	11th to 20th	Night	63% 10% 11% 11% 5%	3555
	21st to end	Night	55% 7% 10% 19% 8% 1	3690
April	1st to 10th	Night	59% 5% 7% 15% 12% 3	1900
	11th to 20th	Night	51% 7% 10% 19% 12% 1	1716
	21st to end	Night	52% 7% 8% 18% 12% 2	1710
May	1st to 10th	Night	47% 10% 14% 16% 11% 1	2825
	11th to 20th	Night	47% 12% 14% 17% 9% 1	2473
	21st to end	Night	43% 13% 13% 20% 10% 1	2402
June	1st to 10th	Night	51% 8% 14% 18% 7% 1	1330
	11th to 20th	Night	43% 7% 16% 19% 13% 2	1330
	21st to end	Night	54% 8% 14% 16% 9%	1330
July	1st to 10th	Night	45% 7% 20% 24% 4	2175
	11th to 20th	Night	44% 8% 23% 21% 4	2373
	21st to end	Night	38% 9% 26% 19% 8%	2651
August	1st to 10th	Night	48% 9% 17% 22% 5%	2549
	11th to 20th	Night	53% 10% 19% 11% 6%	2809
	21st to end	Night	44% 7% 14% 24% 10%	3149
September	1st to 10th	Night	41% 11% 14% 23% 10% 1	1923
	11th to 20th	Night	44% 7% 17% 22% 9% 1	2090
	21st to end	Night	42% 8% 13% 25% 11%	2090
October	1st to 10th	Night	50% 5% 13% 25% 6%	3539
	11th to 20th	Night	48% 7% 17% 24% 4	4001
	21st to end	Night	47% 8% 19% 19% 7%	4467
November	1st to 10th	Night	52% 9% 16% 17% 6%	2453
	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% 15% 33% 19% 9% 2	460
	21st to end	Day	24% 18% 31% 19% 7% 2	506
April	1st to 10th	Day	28% 17% 30% 19% 5% 1	460
	11th to 20th	Day	25% 19% 29% 19% 6% 2	452
	21st to end	Day	25% 17% 32% 18% 5% 2	460
May	1st to 10th	Day	24% 17% 29% 20% 8% 2	463
	11th to 20th	Day	18% 15% 32% 25% 9% 1	496
	21st to end	Day	21% 16% 35% 19% 7% 1	735
June	1st to 10th	Day	24% 13% 32% 21% 9% 1	680
	11th to 20th	Day	20% 10% 29% 25% 14% 2	680
	21st to end	Day	22% 7% 29% 31% 11% 1	680
July	1st to 10th	Day	16% 11% 30% 27% 14% 1	670
	11th to 20th	Day	15% 9% 28% 32% 13% 3	543
	21st to end	Day	14% 9% 27% 33% 15% 2	532
August	1st to 10th	Day	15% 10% 27% 30% 15% 3	486
	11th to 20th	Day	17% 6% 30% 26% 18% 3	479
	21st to end	Day	15% 12% 27% 25% 15% 7%	539
September	1st to 10th	Day	16% 10% 28% 27% 14% 5%	490
	11th to 20th	Day	20% 12% 25% 25% 15% 4	490
	21st to end	Day	19% 12% 26% 25% 13% 5%	490
October	1st to 10th	Day	18% 13% 29% 25% 11% 3	472
	11th to 20th	Day	28% 17% 25% 20% 9% 1	390
	21st to end	Day	30% 14% 31% 18% 6% 1	429
November	1st to 10th	Day	29% 14% 30% 22% 4 1	374
	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% 35% 21% 8%	760
	21st to end	Night	23% 13% 31% 25% 7%	836
April	1st to 10th	Night	29% 10% 30% 24% 6% 1	760
	11th to 20th	Night	24% 11% 31% 26% 7%	592
	21st to end	Night	31% 11% 25% 26% 6% 1	570
May	1st to 10th	Night	26% 8% 29% 29% 7% 1	568
	11th to 20th	Night	25% 9% 25% 30% 11% 1	374
	21st to end	Night	25% 12% 33% 22% 9%	411
June	1st to 10th	Night	20% 8% 29% 34% 8% 1	380
	11th to 20th	Night	18% 4 26% 36% 14% 1	380
	21st to end	Night	23% 7% 27% 33% 9%	380
July	1st to 10th	Night	18% 4 31% 35% 11% 1	370
	11th to 20th	Night	15% 5% 22% 43% 14% 1	368
	21st to end	Night	16% 4 19% 44% 16% 1	416
August	1st to 10th	Night	15% 5% 18% 44% 17% 1	405
	11th to 20th	Night	16% 4 22% 39% 18% 1	562
	21st to end	Night	15% 7% 23% 37% 16% 2	639
September	1st to 10th	Night	17% 7% 28% 34% 13% 1	760
	11th to 20th	Night	21% 8% 26% 28% 14% 3	760
	21st to end	Night	20% 7% 27% 32% 12% 2	760
October	1st to 10th	Night	22% 11% 27% 28% 10% 2	760
	11th to 20th	Night	28% 9% 28% 25% 9% 1	760
	21st to end	Night	26% 11% 32% 23% 7%	836
November	1st to 10th	Night	26% 15% 30% 24% 5%	755
	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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