Sainte-Anne-des-Plaines
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sainte-Anne-des-Plaines 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% 8% 3 6% 6% 3 5% 5% 5% 7% 34%	74783
	Night	18% 9% 4 7% 5% 3 4 4 5% 6% 34%	75017
Transparency	Day	49% 6% 12% 20% 11% 1	74488
	Night	51% 6% 11% 20% 11% 1	74846
Seeing	Day	20% 11% 28% 25% 12% 3	13444
	Night	22% 8% 29% 30% 10% 1	22540

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	16% 15% 5% 11% 8% 4 4 4 4 6% 24%	1517
	11th to 20th	Day	18% 15% 5% 8% 5% 3 5% 3 4 5% 29%	1480
	21st to end	Day	11% 13% 4 8% 7% 3 6% 6% 6% 5% 30%	1584
February	1st to 10th	Day	13% 16% 4 8% 7% 3 6% 4 5% 6% 27%	1579
	11th to 20th	Day	13% 13% 5% 9% 6% 4 6% 5% 5% 5% 28%	1658
	21st to end	Day	18% 14% 5% 10% 6% 2 5% 4 4 5% 27%	1480
March	1st to 10th	Day	15% 12% 4 8% 8% 4 6% 5% 4 6% 29%	1797
	11th to 20th	Day	16% 11% 4 6% 7% 3 5% 4 4 5% 34%	1867
	21st to end	Day	19% 9% 4 7% 5% 3 4 4 4 5% 36%	2370
April	1st to 10th	Day	21% 9% 5% 7% 6% 3 5% 4 4 4 33%	2160
	11th to 20th	Day	21% 7% 3 5% 5% 3 4 4 4 6% 37%	2134
	21st to end	Day	22% 10% 3 6% 6% 3 4 4 4 6% 32%	2305
May	1st to 10th	Day	19% 7% 3 6% 5% 4 5% 4 4 7% 34%	2496
	11th to 20th	Day	20% 6% 3 5% 6% 3 4 4 6% 7% 36%	2478
	21st to end	Day	18% 6% 3 6% 5% 4 6% 5% 6% 8% 36%	2725
June	1st to 10th	Day	22% 7% 2 5% 6% 4 5% 6% 5% 9% 30%	2520
	11th to 20th	Day	15% 6% 2 6% 6% 3 5% 5% 6% 8% 37%	2520
	21st to end	Day	19% 7% 3 6% 7% 4 6% 5% 6% 7% 29%	2520
July	1st to 10th	Day	12% 5% 2 5% 5% 4 6% 6% 7% 8% 40%	2520
	11th to 20th	Day	13% 5% 2 4 6% 4 6% 6% 8% 9% 37%	2520
	21st to end	Day	11% 5% 3 6% 6% 4 5% 6% 8% 9% 38%	2744
August	1st to 10th	Day	12% 6% 3 6% 6% 4 6% 6% 6% 9% 37%	2506
	11th to 20th	Day	10% 4 3 6% 6% 4 6% 6% 7% 8% 39%	2296
	21st to end	Day	12% 5% 2 5% 5% 3 5% 5% 5% 8% 44%	2376
September	1st to 10th	Day	13% 5% 3 4 5% 3 5% 6% 6% 8% 42%	2160
	11th to 20th	Day	14% 4 2 4 4 3 4 4 5% 7% 49%	2088
	21st to end	Day	16% 5% 2 6% 5% 3 4 4 5% 7% 43%	1980
October	1st to 10th	Day	21% 6% 2 5% 5% 3 5% 4 5% 7% 37%	1851
	11th to 20th	Day	20% 8% 3 7% 6% 4 6% 5% 5% 6% 29%	1761
	21st to end	Day	24% 9% 4 5% 5% 3 4 4 5% 5% 31%	1782
November	1st to 10th	Day	15% 10% 3 6% 5% 3 5% 5% 5% 7% 36%	1671
	11th to 20th	Day	18% 10% 4 6% 5% 3 5% 4 5% 6% 31%	1620
	21st to end	Day	22% 9% 3 6% 7% 4 5% 5% 5% 7% 28%	1520
December	1st to 10th	Day	24% 12% 5% 10% 6% 3 6% 4 4 5% 22%	1520
	11th to 20th	Day	21% 13% 6% 7% 4 3 4 4 5% 5% 28%	1906
	21st to end	Day	27% 16% 6% 8% 5% 3 3 4 3 4 22%	2772
January	1st to 10th	Night	16% 16% 6% 10% 7% 4 4 5% 5% 6% 22%	2649
	11th to 20th	Night	16% 15% 6% 9% 6% 3 5% 4 5% 5% 27%	2602
	21st to end	Night	11% 11% 5% 9% 7% 5% 5% 4 5% 7% 32%	2772
February	1st to 10th	Night	13% 13% 6% 10% 7% 4 5% 5% 5% 6% 25%	2380
	11th to 20th	Night	14% 10% 4 9% 7% 3 5% 5% 5% 5% 32%	2188
	21st to end	Night	15% 12% 5% 8% 6% 3 4 4 5% 5% 32%	1776
March	1st to 10th	Night	17% 12% 5% 8% 6% 3 5% 5% 5% 5% 30%	2150
	11th to 20th	Night	17% 12% 3 7% 6% 4 5% 3 4 6% 33%	2087
	21st to end	Night	17% 9% 3 6% 6% 3 4 4 4 4 40%	1985
April	1st to 10th	Night	24% 8% 5% 5% 5% 3 4 4 5% 7% 31%	1800
	11th to 20th	Night	21% 7% 3 5% 5% 3 4 4 5% 6% 38%	1775
	21st to end	Night	21% 9% 3 5% 5% 3 3 5% 4 6% 36%	1654
May	1st to 10th	Night	22% 7% 3 7% 5% 3 5% 4 4 5% 36%	1479
	11th to 20th	Night	20% 7% 2 5% 4 4 4 4 4 7% 38%	1415
	21st to end	Night	17% 6% 2 6% 5% 3 5% 4 5% 7% 41%	1550
June	1st to 10th	Night	21% 6% 3 5% 5% 3 5% 4 7% 8% 33%	1440
	11th to 20th	Night	17% 6% 3 7% 4 2 4 5% 6% 7% 39%	1440
	21st to end	Night	19% 5% 3 6% 5% 3 5% 5% 6% 7% 36%	1440
July	1st to 10th	Night	10% 4 2 6% 4 3 5% 6% 8% 9% 44%	1440
	11th to 20th	Night	11% 6% 2 5% 6% 3 7% 5% 6% 8% 41%	1440
	21st to end	Night	12% 5% 3 5% 5% 3 5% 5% 7% 9% 42%	1574
August	1st to 10th	Night	12% 4 3 6% 5% 3 5% 5% 5% 9% 43%	1432
	11th to 20th	Night	12% 4 3 5% 5% 3 5% 5% 5% 7% 44%	1584
	21st to end	Night	14% 5% 2 5% 4 3 4 4 7% 8% 44%	1980
September	1st to 10th	Night	11% 5% 3 5% 6% 4 5% 5% 5% 7% 45%	1800
	11th to 20th	Night	14% 5% 2 5% 4 2 3 4 4 7% 50%	1872
	21st to end	Night	17% 4 2 5% 5% 2 3 4 5% 6% 47%	1980
October	1st to 10th	Night	19% 6% 2 5% 5% 3 5% 4 4 5% 41%	2106
	11th to 20th	Night	20% 7% 3 6% 5% 3 4 4 5% 6% 36%	2198
	21st to end	Night	22% 8% 3 7% 6% 3 4 4 4 6% 32%	2574
November	1st to 10th	Night	18% 9% 3 6% 5% 4 5% 4 4 8% 34%	2407
	11th to 20th	Night	19% 9% 3 7% 6% 3 4 5% 4 6% 34%	2556
	21st to end	Night	21% 13% 4 7% 5% 3 4 4 4 5% 30%	2660
December	1st to 10th	Night	21% 14% 5% 8% 7% 3 5% 4 4 6% 23%	2660
	11th to 20th	Night	22% 14% 5% 7% 5% 3 4 4 3 5% 28%	3288
	21st to end	Night	27% 16% 5% 8% 5% 2 3 3 3 3 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	64% 6% 9% 15% 6%	1518
	11th to 20th	Day	60% 5% 9% 14% 11% 1	1480
	21st to end	Day	53% 7% 11% 17% 11% 1	1584
February	1st to 10th	Day	58% 5% 10% 18% 7% 2	1579
	11th to 20th	Day	57% 6% 12% 15% 9% 1	1667
	21st to end	Day	59% 4 9% 17% 9% 2	1480
March	1st to 10th	Day	56% 5% 10% 17% 11% 2	1800
	11th to 20th	Day	52% 4 13% 15% 14% 2	1867
	21st to end	Day	51% 4 10% 18% 13% 4	2370
April	1st to 10th	Day	55% 4 8% 18% 11% 2	2160
	11th to 20th	Day	49% 4 8% 23% 14% 2	2134
	21st to end	Day	54% 6% 8% 17% 12% 3	2305
May	1st to 10th	Day	50% 5% 8% 21% 14% 2	2496
	11th to 20th	Day	46% 6% 11% 19% 15% 3	2482
	21st to end	Day	45% 7% 13% 18% 14% 2	2725
June	1st to 10th	Day	51% 6% 11% 18% 11% 2	2520
	11th to 20th	Day	43% 7% 11% 23% 13% 3	2520
	21st to end	Day	52% 7% 13% 17% 10% 1	2520
July	1st to 10th	Day	38% 8% 14% 26% 12% 1	2450
	11th to 20th	Day	40% 7% 17% 25% 10%	2445
	21st to end	Day	40% 8% 18% 24% 9%	2591
August	1st to 10th	Day	42% 8% 17% 24% 8%	2492
	11th to 20th	Day	38% 8% 19% 25% 10%	2296
	21st to end	Day	36% 7% 17% 25% 14% 1	2376
September	1st to 10th	Day	38% 8% 14% 27% 13% 1	2160
	11th to 20th	Day	35% 6% 13% 32% 14% 1	2088
	21st to end	Day	42% 6% 14% 26% 11% 1	1980
October	1st to 10th	Day	48% 6% 13% 22% 12%	1851
	11th to 20th	Day	54% 8% 13% 19% 6%	1761
	21st to end	Day	55% 5% 13% 18% 8% 1	1782
November	1st to 10th	Day	46% 7% 15% 22% 9% 1	1671
	11th to 20th	Day	52% 7% 11% 19% 11%	1620
	21st to end	Day	57% 7% 14% 16% 6% 1	1520
December	1st to 10th	Day	66% 4 11% 13% 5%	1520
	11th to 20th	Day	58% 5% 11% 18% 7%	1906
	21st to end	Day	67% 5% 11% 11% 5%	2772
January	1st to 10th	Night	64% 5% 10% 15% 5%	2649
	11th to 20th	Night	61% 7% 10% 13% 8% 2	2602
	21st to end	Night	53% 6% 11% 17% 12% 1	2772
February	1st to 10th	Night	61% 6% 9% 16% 8% 1	2380
	11th to 20th	Night	54% 5% 11% 20% 9% 1	2190
	21st to end	Night	55% 5% 9% 16% 14% 1	1776
March	1st to 10th	Night	55% 5% 10% 17% 11% 2	2160
	11th to 20th	Night	54% 4 10% 16% 13% 3	2088
	21st to end	Night	50% 4 8% 19% 15% 4	1985
April	1st to 10th	Night	53% 5% 8% 18% 14% 2	1800
	11th to 20th	Night	49% 5% 7% 21% 15% 2	1775
	21st to end	Night	50% 5% 8% 19% 13% 4	1654
May	1st to 10th	Night	50% 4 7% 19% 15% 5%	1479
	11th to 20th	Night	47% 5% 9% 18% 17% 4	1416
	21st to end	Night	44% 6% 11% 20% 17% 2	1551
June	1st to 10th	Night	50% 6% 10% 21% 13% 1	1440
	11th to 20th	Night	43% 6% 12% 22% 13% 3	1440
	21st to end	Night	46% 9% 12% 18% 14%	1440
July	1st to 10th	Night	35% 9% 13% 26% 16% 1	1400
	11th to 20th	Night	38% 7% 17% 27% 11%	1392
	21st to end	Night	36% 9% 17% 25% 12%	1486
August	1st to 10th	Night	39% 7% 17% 26% 11%	1422
	11th to 20th	Night	37% 8% 17% 25% 12%	1584
	21st to end	Night	38% 8% 15% 26% 12% 1	1980
September	1st to 10th	Night	37% 7% 14% 26% 15% 1	1800
	11th to 20th	Night	36% 6% 13% 33% 11% 1	1872
	21st to end	Night	39% 7% 11% 29% 14%	1980
October	1st to 10th	Night	45% 6% 10% 25% 13% 1	2106
	11th to 20th	Night	50% 5% 12% 25% 8%	2198
	21st to end	Night	55% 5% 13% 18% 9% 1	2574
November	1st to 10th	Night	50% 6% 13% 21% 9% 1	2407
	11th to 20th	Night	51% 6% 13% 19% 10% 1	2556
	21st to end	Night	58% 6% 11% 18% 7%	2660
December	1st to 10th	Night	62% 7% 11% 16% 4	2660
	11th to 20th	Night	60% 5% 9% 18% 7% 1	3288
	21st to end	Night	66% 5% 9% 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% 17% 26% 27% 9%	180
	11th to 20th	Day	26% 13% 34% 21% 4 2	170
	21st to end	Day	17% 14% 35% 26% 6% 2	176
February	1st to 10th	Day	33% 21% 32% 13%	222
	11th to 20th	Day	22% 13% 38% 22% 4	325
	21st to end	Day	28% 14% 31% 23% 4	346
March	1st to 10th	Day	24% 11% 34% 24% 8%	420
	11th to 20th	Day	22% 14% 33% 26% 5% 1	420
	21st to end	Day	26% 12% 30% 21% 10% 1	462
April	1st to 10th	Day	25% 15% 27% 22% 9% 2	420
	11th to 20th	Day	27% 16% 23% 22% 11% 2	412
	21st to end	Day	26% 15% 29% 20% 8% 2	420
May	1st to 10th	Day	23% 11% 32% 24% 9% 2	423
	11th to 20th	Day	21% 8% 31% 25% 13% 2	447
	21st to end	Day	16% 12% 35% 23% 12% 2	485
June	1st to 10th	Day	23% 12% 25% 27% 11% 2	450
	11th to 20th	Day	16% 12% 24% 31% 14% 3	450
	21st to end	Day	20% 9% 25% 28% 14% 4	450
July	1st to 10th	Day	13% 7% 22% 33% 20% 6%	445
	11th to 20th	Day	14% 5% 27% 32% 18% 5%	444
	21st to end	Day	13% 5% 26% 34% 17% 5%	488
August	1st to 10th	Day	14% 5% 23% 32% 21% 6%	446
	11th to 20th	Day	11% 5% 20% 34% 19% 12%	439
	21st to end	Day	14% 8% 25% 24% 20% 9%	495
September	1st to 10th	Day	12% 6% 27% 29% 18% 8%	450
	11th to 20th	Day	14% 8% 23% 26% 18% 11%	450
	21st to end	Day	18% 9% 26% 23% 18% 7%	450
October	1st to 10th	Day	22% 12% 24% 22% 15% 4	450
	11th to 20th	Day	19% 13% 33% 22% 11% 2	430
	21st to end	Day	31% 13% 24% 24% 8%	396
November	1st to 10th	Day	24% 15% 25% 24% 10% 1	365
	11th to 20th	Day	24% 15% 33% 17% 10% 1	280
	21st to end	Day	26% 15% 28% 22% 8% 1	180
December	1st to 10th	Day	27% 12% 26% 25% 8% 2	180
	11th to 20th	Day	24% 14% 38% 21% 2 1	180
	21st to end	Day	33% 17% 27% 16% 7% 1	198
January	1st to 10th	Night	25% 11% 32% 26% 6%	760
	11th to 20th	Night	25% 10% 33% 25% 7%	744
	21st to end	Night	17% 8% 36% 30% 8% 1	792
February	1st to 10th	Night	21% 9% 37% 27% 5% 1	720
	11th to 20th	Night	20% 11% 36% 27% 6%	703
	21st to end	Night	23% 9% 33% 31% 4	592
March	1st to 10th	Night	24% 9% 33% 29% 5%	720
	11th to 20th	Night	25% 10% 32% 26% 8%	720
	21st to end	Night	22% 8% 31% 31% 7% 1	792
April	1st to 10th	Night	27% 9% 27% 30% 6%	720
	11th to 20th	Night	24% 11% 30% 28% 6% 1	711
	21st to end	Night	28% 8% 32% 24% 8%	574
May	1st to 10th	Night	23% 6% 34% 28% 8% 1	399
	11th to 20th	Night	23% 6% 31% 33% 7% 1	354
	21st to end	Night	19% 5% 38% 30% 8%	389
June	1st to 10th	Night	25% 5% 26% 34% 9%	360
	11th to 20th	Night	18% 6% 30% 33% 13%	360
	21st to end	Night	20% 4 26% 33% 16%	360
July	1st to 10th	Night	9% 6% 28% 41% 16% 1	350
	11th to 20th	Night	12% 3 23% 46% 16%	348
	21st to end	Night	12% 4 20% 47% 16% 1	394
August	1st to 10th	Night	15% 4 13% 46% 22% 1	358
	11th to 20th	Night	14% 2 21% 35% 25% 2	520
	21st to end	Night	15% 3 23% 35% 22% 2	792
September	1st to 10th	Night	15% 3 23% 42% 16% 1	720
	11th to 20th	Night	16% 6% 20% 37% 20% 2	720
	21st to end	Night	18% 5% 26% 33% 17% 2	720
October	1st to 10th	Night	22% 6% 26% 34% 12% 1	720
	11th to 20th	Night	23% 8% 27% 29% 11% 1	720
	21st to end	Night	27% 8% 30% 27% 7%	792
November	1st to 10th	Night	23% 11% 29% 28% 8%	740
	11th to 20th	Night	23% 9% 33% 24% 10% 1	760
	21st to end	Night	28% 11% 31% 22% 8% 1	760
December	1st to 10th	Night	29% 10% 32% 23% 7%	760
	11th to 20th	Night	28% 12% 32% 23% 5% 1	760
	21st to end	Night	32% 12% 30% 20% 6%	836

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