Saint-Sauveur
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint-Sauveur 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	17% 10% 4 7% 6% 3 5% 5% 5% 6% 31%	74781
	Night	16% 10% 4 7% 6% 3 4 4 5% 6% 34%	75021
Transparency	Day	52% 6% 12% 19% 10% 1	74486
	Night	51% 6% 12% 20% 10% 1	74850
Seeing	Day	24% 17% 31% 19% 7% 2	13415
	Night	22% 14% 31% 24% 8% 1	22526

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% 7% 11% 9% 3 4 4 4 4 22%	1517
	11th to 20th	Day	15% 17% 5% 10% 7% 4 3 4 4 5% 26%	1480
	21st to end	Day	10% 14% 7% 9% 7% 4 6% 5% 5% 5% 29%	1584
February	1st to 10th	Day	12% 18% 4 11% 8% 3 5% 4 4 6% 24%	1589
	11th to 20th	Day	11% 17% 6% 10% 7% 4 4 5% 5% 5% 27%	1641
	21st to end	Day	16% 14% 6% 10% 8% 4 5% 4 4 5% 26%	1480
March	1st to 10th	Day	14% 12% 6% 11% 8% 4 4 3 5% 5% 29%	1797
	11th to 20th	Day	15% 13% 4 9% 7% 4 4 5% 5% 5% 31%	1885
	21st to end	Day	18% 11% 4 7% 7% 2 4 3 4 6% 35%	2358
April	1st to 10th	Day	21% 11% 4 8% 6% 3 4 3 4 5% 31%	2160
	11th to 20th	Day	20% 8% 4 7% 5% 3 4 5% 5% 6% 35%	2134
	21st to end	Day	21% 11% 3 7% 6% 3 4 4 5% 5% 30%	2294
May	1st to 10th	Day	20% 9% 4 8% 6% 3 5% 4 5% 6% 32%	2520
	11th to 20th	Day	20% 8% 3 6% 6% 4 3 4 6% 7% 34%	2478
	21st to end	Day	19% 7% 3 7% 6% 3 5% 6% 4 7% 34%	2725
June	1st to 10th	Day	22% 7% 3 6% 6% 4 5% 6% 6% 7% 28%	2520
	11th to 20th	Day	16% 7% 3 7% 6% 4 5% 5% 6% 8% 34%	2520
	21st to end	Day	21% 8% 3 8% 6% 4 5% 6% 6% 6% 27%	2520
July	1st to 10th	Day	13% 5% 3 5% 6% 4 7% 6% 5% 8% 38%	2520
	11th to 20th	Day	14% 6% 3 6% 5% 4 5% 7% 7% 9% 33%	2520
	21st to end	Day	12% 7% 3 6% 6% 4 6% 7% 7% 8% 34%	2744
August	1st to 10th	Day	13% 6% 3 6% 7% 5% 5% 7% 7% 8% 34%	2506
	11th to 20th	Day	12% 6% 3 5% 7% 4 6% 6% 7% 9% 35%	2298
	21st to end	Day	14% 6% 3 6% 6% 3 5% 4 6% 7% 41%	2376
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 5% 7% 8% 40%	2160
	11th to 20th	Day	14% 5% 2 6% 5% 2 4 4 6% 6% 46%	2102
	21st to end	Day	17% 7% 3 5% 4 3 4 4 5% 6% 40%	1980
October	1st to 10th	Day	22% 7% 3 5% 5% 3 4 5% 4 6% 35%	1832
	11th to 20th	Day	22% 9% 4 7% 6% 4 4 5% 5% 6% 27%	1774
	21st to end	Day	25% 11% 3 6% 6% 3 5% 4 5% 6% 27%	1782
November	1st to 10th	Day	15% 10% 3 6% 6% 3 5% 4 6% 7% 34%	1671
	11th to 20th	Day	18% 12% 5% 8% 6% 3 5% 4 6% 6% 27%	1596
	21st to end	Day	20% 13% 4 7% 6% 4 6% 5% 5% 7% 24%	1520
December	1st to 10th	Day	21% 17% 6% 9% 6% 3 5% 4 3 5% 21%	1520
	11th to 20th	Day	19% 13% 6% 9% 6% 2 4 4 5% 5% 26%	1906
	21st to end	Day	23% 17% 6% 9% 6% 3 3 4 3 4 22%	2772
January	1st to 10th	Night	14% 15% 7% 11% 7% 4 5% 5% 4 6% 21%	2649
	11th to 20th	Night	14% 16% 6% 11% 8% 3 4 3 4 6% 25%	2602
	21st to end	Night	9% 12% 4 9% 7% 5% 5% 4 5% 7% 32%	2772
February	1st to 10th	Night	11% 13% 6% 11% 7% 5% 6% 5% 6% 5% 26%	2367
	11th to 20th	Night	11% 13% 5% 10% 7% 3 5% 5% 6% 6% 30%	2205
	21st to end	Night	13% 12% 6% 9% 7% 3 4 4 4 5% 31%	1776
March	1st to 10th	Night	14% 13% 5% 8% 7% 4 5% 5% 4 5% 29%	2150
	11th to 20th	Night	14% 13% 5% 7% 6% 3 4 4 6% 7% 31%	2069
	21st to end	Night	15% 9% 3 6% 6% 3 5% 4 3 5% 40%	1998
April	1st to 10th	Night	22% 9% 4 7% 5% 3 5% 3 5% 6% 32%	1800
	11th to 20th	Night	18% 7% 2 6% 6% 2 4 5% 5% 6% 38%	1775
	21st to end	Night	20% 8% 4 7% 5% 2 5% 4 4 6% 35%	1666
May	1st to 10th	Night	18% 8% 3 6% 7% 3 4 4 4 5% 36%	1454
	11th to 20th	Night	18% 8% 3 6% 5% 3 3 5% 6% 7% 38%	1415
	21st to end	Night	17% 7% 2 5% 5% 3 5% 4 5% 7% 40%	1550
June	1st to 10th	Night	20% 8% 3 5% 4 4 4 5% 6% 9% 33%	1440
	11th to 20th	Night	18% 7% 3 5% 5% 4 4 4 5% 7% 38%	1440
	21st to end	Night	18% 7% 2 5% 5% 3 4 4 7% 7% 37%	1440
July	1st to 10th	Night	10% 5% 2 5% 5% 3 4 5% 6% 8% 45%	1440
	11th to 20th	Night	11% 6% 3 5% 6% 3 5% 5% 5% 9% 42%	1440
	21st to end	Night	11% 6% 2 5% 6% 3 4 5% 6% 8% 43%	1574
August	1st to 10th	Night	11% 5% 2 5% 5% 4 5% 5% 6% 10% 42%	1432
	11th to 20th	Night	10% 6% 2 6% 4 3 5% 4 6% 7% 45%	1583
	21st to end	Night	13% 5% 2 5% 5% 3 4 4 6% 7% 46%	1980
September	1st to 10th	Night	10% 5% 2 5% 5% 3 6% 5% 5% 7% 47%	1800
	11th to 20th	Night	13% 5% 2 5% 5% 2 4 4 5% 9% 47%	1858
	21st to end	Night	17% 6% 2 4 3 3 4 4 5% 7% 46%	1980
October	1st to 10th	Night	17% 7% 4 6% 5% 3 5% 4 5% 5% 40%	2126
	11th to 20th	Night	21% 7% 3 6% 5% 2 4 5% 5% 6% 34%	2186
	21st to end	Night	22% 10% 3 6% 6% 3 4 5% 5% 6% 30%	2574
November	1st to 10th	Night	16% 9% 4 7% 6% 4 5% 4 5% 7% 32%	2407
	11th to 20th	Night	16% 10% 4 7% 6% 3 4 6% 5% 6% 33%	2581
	21st to end	Night	18% 14% 4 8% 6% 3 4 4 5% 7% 28%	2660
December	1st to 10th	Night	17% 14% 6% 9% 7% 4 6% 5% 5% 7% 21%	2660
	11th to 20th	Night	19% 14% 5% 8% 6% 3 5% 4 4 5% 26%	3288
	21st to end	Night	23% 19% 5% 8% 5% 3 3 3 4 4 23%	4884

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	65% 5% 8% 15% 5%	1518
	11th to 20th	Day	62% 3 10% 13% 10% 1	1480
	21st to end	Day	56% 5% 9% 17% 11% 1	1584
February	1st to 10th	Day	61% 5% 7% 17% 8% 2	1589
	11th to 20th	Day	59% 5% 11% 14% 9% 1	1650
	21st to end	Day	62% 3 8% 15% 9% 2	1480
March	1st to 10th	Day	58% 5% 8% 17% 10% 2	1800
	11th to 20th	Day	55% 3 12% 15% 12% 3	1885
	21st to end	Day	51% 5% 8% 18% 14% 4	2358
April	1st to 10th	Day	56% 4 9% 17% 12% 3	2160
	11th to 20th	Day	50% 4 9% 22% 13% 2	2134
	21st to end	Day	55% 5% 8% 16% 12% 4	2294
May	1st to 10th	Day	53% 4 7% 20% 13% 3	2520
	11th to 20th	Day	49% 5% 10% 17% 16% 3	2482
	21st to end	Day	49% 6% 10% 20% 14% 2	2725
June	1st to 10th	Day	53% 6% 11% 17% 11% 2	2520
	11th to 20th	Day	46% 7% 12% 20% 12% 3	2520
	21st to end	Day	56% 8% 11% 16% 9% 1	2520
July	1st to 10th	Day	41% 9% 14% 26% 10% 1	2450
	11th to 20th	Day	43% 8% 14% 24% 10%	2445
	21st to end	Day	45% 8% 16% 22% 9%	2591
August	1st to 10th	Day	45% 9% 16% 23% 7%	2492
	11th to 20th	Day	42% 10% 16% 23% 9% 1	2298
	21st to end	Day	42% 7% 15% 23% 13% 1	2376
September	1st to 10th	Day	41% 6% 14% 26% 13%	2160
	11th to 20th	Day	37% 6% 14% 29% 12% 1	2102
	21st to end	Day	43% 6% 15% 26% 11%	1980
October	1st to 10th	Day	49% 5% 12% 23% 11% 1	1832
	11th to 20th	Day	57% 7% 13% 17% 6% 1	1774
	21st to end	Day	59% 4 14% 14% 7% 1	1782
November	1st to 10th	Day	49% 7% 14% 20% 9% 1	1671
	11th to 20th	Day	56% 4 15% 15% 9%	1596
	21st to end	Day	60% 6% 15% 14% 4 1	1520
December	1st to 10th	Day	67% 6% 11% 11% 5%	1520
	11th to 20th	Day	61% 4 13% 15% 6%	1906
	21st to end	Day	68% 5% 8% 13% 6%	2772
January	1st to 10th	Night	65% 5% 10% 14% 5%	2649
	11th to 20th	Night	61% 5% 13% 11% 8% 2	2602
	21st to end	Night	53% 6% 10% 17% 12% 2	2772
February	1st to 10th	Night	59% 5% 10% 18% 7% 1	2367
	11th to 20th	Night	54% 6% 13% 18% 9% 1	2207
	21st to end	Night	56% 3 9% 17% 12% 2	1776
March	1st to 10th	Night	57% 4 9% 17% 10% 2	2160
	11th to 20th	Night	54% 5% 10% 16% 12% 3	2070
	21st to end	Night	48% 4 8% 20% 15% 5%	1998
April	1st to 10th	Night	53% 4 8% 19% 14% 2	1800
	11th to 20th	Night	47% 5% 9% 23% 15% 2	1775
	21st to end	Night	51% 5% 8% 20% 13% 3	1666
May	1st to 10th	Night	51% 4 7% 19% 14% 4	1454
	11th to 20th	Night	45% 6% 9% 18% 18% 4	1416
	21st to end	Night	43% 7% 11% 21% 16% 3	1551
June	1st to 10th	Night	48% 6% 13% 22% 11% 1	1440
	11th to 20th	Night	45% 6% 10% 23% 13% 3	1440
	21st to end	Night	46% 9% 12% 21% 13%	1440
July	1st to 10th	Night	35% 9% 15% 26% 14% 1	1400
	11th to 20th	Night	39% 7% 14% 29% 10%	1392
	21st to end	Night	38% 8% 17% 25% 12%	1486
August	1st to 10th	Night	36% 10% 18% 26% 10%	1422
	11th to 20th	Night	36% 9% 16% 27% 11%	1583
	21st to end	Night	37% 8% 16% 27% 12%	1980
September	1st to 10th	Night	36% 8% 14% 26% 15% 1	1800
	11th to 20th	Night	36% 6% 14% 33% 11% 1	1858
	21st to end	Night	39% 6% 12% 30% 13%	1980
October	1st to 10th	Night	46% 6% 11% 24% 13% 1	2126
	11th to 20th	Night	50% 6% 15% 21% 8%	2186
	21st to end	Night	55% 6% 14% 17% 8% 1	2574
November	1st to 10th	Night	51% 6% 15% 21% 7% 1	2407
	11th to 20th	Night	52% 5% 15% 18% 8% 2	2581
	21st to end	Night	57% 6% 13% 17% 6% 1	2660
December	1st to 10th	Night	64% 6% 12% 13% 4	2660
	11th to 20th	Night	60% 5% 10% 16% 7% 1	3288
	21st to end	Night	66% 5% 8% 15% 5%	4884

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	21% 20% 39% 17% 4	180
	11th to 20th	Day	28% 18% 37% 12% 5% 1	170
	21st to end	Day	21% 22% 37% 15% 5% 1	176
February	1st to 10th	Day	37% 28% 30% 5%	227
	11th to 20th	Day	24% 28% 37% 10% 1	308
	21st to end	Day	28% 23% 31% 15% 2	346
March	1st to 10th	Day	28% 20% 32% 17% 3	420
	11th to 20th	Day	24% 25% 32% 14% 4 1	420
	21st to end	Day	29% 21% 27% 15% 7% 1	462
April	1st to 10th	Day	32% 16% 30% 14% 7%	420
	11th to 20th	Day	32% 19% 25% 15% 7% 1	412
	21st to end	Day	30% 20% 30% 14% 4 1	420
May	1st to 10th	Day	26% 19% 34% 15% 5% 1	423
	11th to 20th	Day	24% 18% 32% 20% 4 1	447
	21st to end	Day	23% 21% 32% 19% 5%	485
June	1st to 10th	Day	26% 18% 34% 16% 6% 1	450
	11th to 20th	Day	19% 19% 33% 19% 9% 2	450
	21st to end	Day	27% 12% 32% 19% 8% 2	450
July	1st to 10th	Day	14% 10% 36% 27% 11% 2	445
	11th to 20th	Day	16% 11% 36% 27% 8% 2	444
	21st to end	Day	15% 9% 35% 29% 11% 1	488
August	1st to 10th	Day	15% 10% 31% 29% 13% 2	446
	11th to 20th	Day	13% 9% 30% 29% 13% 6%	439
	21st to end	Day	18% 14% 29% 20% 13% 6%	495
September	1st to 10th	Day	17% 10% 33% 24% 10% 5%	450
	11th to 20th	Day	13% 12% 29% 25% 15% 6%	450
	21st to end	Day	21% 14% 26% 23% 12% 4	450
October	1st to 10th	Day	25% 19% 24% 21% 10% 1	450
	11th to 20th	Day	25% 16% 32% 19% 7% 1	437
	21st to end	Day	33% 14% 30% 18% 5%	396
November	1st to 10th	Day	28% 18% 29% 19% 4 1	365
	11th to 20th	Day	25% 23% 32% 15% 4	256
	21st to end	Day	27% 24% 32% 15% 2	180
December	1st to 10th	Day	29% 17% 32% 18% 4 1	180
	11th to 20th	Day	29% 24% 33% 12% 1 1	180
	21st to end	Day	34% 25% 24% 12% 4 1	198
January	1st to 10th	Night	24% 17% 34% 22% 3	760
	11th to 20th	Night	23% 20% 32% 20% 4	744
	21st to end	Night	17% 16% 39% 22% 6% 1	792
February	1st to 10th	Night	20% 18% 38% 20% 4 1	720
	11th to 20th	Night	21% 18% 39% 17% 4 1	703
	21st to end	Night	22% 17% 34% 24% 3	592
March	1st to 10th	Night	23% 19% 35% 21% 3	720
	11th to 20th	Night	24% 17% 34% 19% 6%	720
	21st to end	Night	22% 16% 33% 23% 6% 1	792
April	1st to 10th	Night	27% 17% 28% 24% 4	720
	11th to 20th	Night	24% 14% 33% 23% 5%	711
	21st to end	Night	26% 15% 33% 19% 7% 1	586
May	1st to 10th	Night	24% 13% 34% 21% 6% 2	374
	11th to 20th	Night	21% 12% 32% 27% 7% 1	354
	21st to end	Night	20% 8% 40% 25% 7%	389
June	1st to 10th	Night	26% 8% 31% 28% 7%	360
	11th to 20th	Night	24% 7% 29% 29% 11% 1	360
	21st to end	Night	20% 7% 26% 32% 14% 1	360
July	1st to 10th	Night	11% 9% 31% 34% 14% 1	350
	11th to 20th	Night	11% 6% 27% 41% 14%	348
	21st to end	Night	14% 4 26% 42% 12% 2	394
August	1st to 10th	Night	14% 5% 21% 42% 16% 2	358
	11th to 20th	Night	11% 6% 27% 32% 23% 2	519
	21st to end	Night	15% 6% 29% 31% 17% 2	792
September	1st to 10th	Night	13% 8% 30% 35% 13% 1	720
	11th to 20th	Night	16% 8% 26% 30% 18% 2	720
	21st to end	Night	20% 9% 25% 28% 16% 2	720
October	1st to 10th	Night	23% 11% 29% 27% 10% 1	720
	11th to 20th	Night	25% 12% 29% 24% 8% 1	720
	21st to end	Night	27% 15% 31% 22% 5%	792
November	1st to 10th	Night	24% 17% 29% 23% 7% 1	740
	11th to 20th	Night	23% 16% 34% 19% 8% 1	760
	21st to end	Night	28% 19% 28% 19% 5% 1	760
December	1st to 10th	Night	27% 18% 33% 17% 5%	760
	11th to 20th	Night	28% 20% 29% 18% 4 1	760
	21st to end	Night	32% 18% 31% 16% 4	836

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