Saint-Hyacinthe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint-Hyacinthe clear sky chart from 2005-11-06 to 2026-05-17.

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% 3 8% 5% 5% 5% 4 5% 7% 31%	131924
	Night	18% 12% 4 9% 5% 5% 4 3 5% 6% 29%	130918
Transparency	Day	52% 7% 12% 20% 9% 1	135367
	Night	56% 6% 11% 17% 9% 1	135562
Seeing	Day	22% 13% 29% 23% 10% 3	16466
	Night	24% 11% 28% 28% 9% 1	25483

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	17% 19% 6% 14% 5% 5% 3 3 3 4 21%	4661
	11th to 20th	Day	13% 17% 6% 14% 8% 6% 5% 3 4 5% 20%	4650
	21st to end	Day	10% 13% 5% 12% 8% 8% 6% 4 5% 6% 23%	5124
February	1st to 10th	Day	16% 16% 4 10% 6% 5% 5% 3 5% 4 26%	1796
	11th to 20th	Day	14% 16% 5% 11% 7% 5% 4 3 5% 6% 25%	1991
	21st to end	Day	17% 15% 4 9% 6% 5% 3 3 5% 5% 26%	1730
March	1st to 10th	Day	19% 13% 4 10% 6% 5% 5% 4 4 5% 24%	4576
	11th to 20th	Day	14% 12% 4 9% 5% 5% 4 4 6% 7% 32%	4766
	21st to end	Day	18% 12% 4 9% 5% 4 4 3 4 5% 32%	6102
April	1st to 10th	Day	22% 12% 3 8% 5% 4 4 3 4 6% 28%	2520
	11th to 20th	Day	22% 8% 3 7% 4 4 4 4 4 5% 36%	2494
	21st to end	Day	23% 9% 3 7% 5% 3 4 4 4 6% 32%	2730
May	1st to 10th	Day	27% 10% 3 9% 5% 5% 4 4 5% 5% 23%	6290
	11th to 20th	Day	20% 8% 3 8% 5% 5% 5% 4 6% 7% 30%	6402
	21st to end	Day	20% 8% 3 7% 5% 4 5% 4 5% 7% 31%	6949
June	1st to 10th	Day	23% 7% 2 7% 4 5% 5% 4 6% 7% 31%	2800
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 4 6% 7% 39%	2800
	21st to end	Day	21% 8% 3 7% 4 5% 4 4 6% 8% 31%	2800
July	1st to 10th	Day	13% 7% 3 8% 6% 6% 6% 4 7% 9% 31%	6360
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 4 7% 9% 40%	6360
	21st to end	Day	12% 6% 2 5% 4 3 5% 4 6% 10% 44%	6926
August	1st to 10th	Day	14% 7% 3 8% 5% 5% 5% 4 7% 9% 32%	4563
	11th to 20th	Day	15% 6% 3 7% 4 4 5% 4 7% 9% 37%	4154
	21st to end	Day	17% 6% 2 7% 4 4 5% 3 6% 7% 39%	4312
September	1st to 10th	Day	12% 6% 2 5% 4 4 5% 6% 6% 8% 43%	2400
	11th to 20th	Day	15% 6% 2 5% 4 2 3 3 5% 7% 49%	2283
	21st to end	Day	19% 5% 2 6% 4 4 4 3 6% 7% 40%	2200
October	1st to 10th	Day	19% 6% 2 7% 4 3 5% 4 6% 7% 35%	2113
	11th to 20th	Day	19% 8% 2 8% 6% 5% 5% 4 6% 6% 30%	1918
	21st to end	Day	25% 10% 4 6% 5% 4 4 3 5% 6% 29%	1980
November	1st to 10th	Day	18% 12% 3 7% 5% 4 4 4 5% 6% 31%	1851
	11th to 20th	Day	18% 13% 4 8% 5% 5% 5% 4 4 7% 28%	1849
	21st to end	Day	24% 14% 4 8% 5% 5% 4 3 4 5% 24%	1680
December	1st to 10th	Day	20% 19% 5% 13% 6% 5% 4 2 4 5% 17%	2680
	11th to 20th	Day	20% 15% 5% 10% 5% 4 4 3 4 6% 25%	3066
	21st to end	Day	23% 14% 5% 10% 5% 6% 5% 5% 6% 4 17%	4048
January	1st to 10th	Night	15% 21% 8% 13% 6% 4 4 3 3 4 21%	8234
	11th to 20th	Night	13% 18% 7% 17% 8% 6% 4 3 4 4 16%	8235
	21st to end	Night	11% 14% 5% 13% 9% 6% 5% 4 5% 5% 23%	9057
February	1st to 10th	Night	15% 16% 6% 12% 6% 6% 4 3 5% 6% 22%	2822
	11th to 20th	Night	14% 14% 6% 11% 6% 5% 4 3 4 4 27%	2515
	21st to end	Night	15% 15% 5% 8% 6% 4 4 3 5% 5% 30%	2076
March	1st to 10th	Night	21% 13% 4 9% 5% 4 4 3 4 4 29%	5484
	11th to 20th	Night	16% 14% 4 8% 5% 5% 4 3 5% 7% 29%	5410
	21st to end	Night	17% 13% 5% 11% 5% 5% 4 3 4 4 29%	5072
April	1st to 10th	Night	25% 10% 4 7% 4 4 4 3 4 6% 29%	2100
	11th to 20th	Night	23% 10% 3 7% 5% 4 4 3 5% 6% 32%	2073
	21st to end	Night	22% 10% 3 7% 4 4 3 3 5% 5% 35%	1890
May	1st to 10th	Night	27% 10% 4 8% 5% 5% 4 4 4 6% 24%	3914
	11th to 20th	Night	25% 8% 2 8% 5% 4 4 4 5% 6% 30%	3623
	21st to end	Night	18% 10% 3 8% 5% 4 5% 3 5% 7% 32%	3926
June	1st to 10th	Night	23% 8% 3 6% 4 4 4 4 6% 7% 32%	1600
	11th to 20th	Night	17% 5% 2 7% 4 4 5% 4 7% 8% 37%	1600
	21st to end	Night	17% 8% 3 7% 5% 4 4 5% 6% 7% 34%	1600
July	1st to 10th	Night	14% 7% 3 7% 6% 6% 6% 4 7% 9% 31%	3600
	11th to 20th	Night	15% 6% 2 6% 4 4 5% 4 6% 7% 40%	3600
	21st to end	Night	10% 5% 2 7% 5% 5% 6% 4 7% 8% 40%	3926
August	1st to 10th	Night	17% 9% 3 8% 4 4 5% 3 6% 7% 35%	2586
	11th to 20th	Night	16% 7% 3 8% 5% 5% 4 4 6% 6% 37%	2856
	21st to end	Night	18% 6% 2 7% 4 4 5% 4 5% 7% 39%	3586
September	1st to 10th	Night	14% 5% 2 7% 4 4 4 3 5% 7% 45%	2000
	11th to 20th	Night	15% 5% 2 5% 4 3 3 3 6% 7% 49%	2115
	21st to end	Night	17% 6% 2 6% 4 4 3 3 5% 8% 41%	2200
October	1st to 10th	Night	18% 6% 3 7% 3 4 3 4 5% 6% 41%	2285
	11th to 20th	Night	22% 8% 3 7% 4 5% 4 3 4 5% 34%	2481
	21st to end	Night	24% 9% 3 9% 5% 4 4 3 4 5% 29%	2860
November	1st to 10th	Night	20% 13% 3 6% 5% 4 4 4 4 5% 31%	2667
	11th to 20th	Night	20% 13% 4 7% 5% 4 4 3 5% 5% 31%	2767
	21st to end	Night	23% 15% 4 9% 4 4 4 3 4 4 26%	2940
December	1st to 10th	Night	18% 20% 7% 13% 6% 5% 4 3 4 4 15%	4720
	11th to 20th	Night	24% 13% 5% 10% 6% 5% 3 3 3 5% 24%	5348
	21st to end	Night	23% 17% 5% 9% 4 3 4 4 6% 5% 20%	7150

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	68% 5% 9% 14% 3	4662
	11th to 20th	Day	66% 7% 7% 12% 7%	4680
	21st to end	Day	60% 7% 9% 13% 10%	5124
February	1st to 10th	Day	61% 6% 9% 16% 6% 1	1796
	11th to 20th	Day	60% 6% 11% 15% 7% 1	2000
	21st to end	Day	60% 5% 11% 15% 8% 1	1730
March	1st to 10th	Day	61% 6% 7% 13% 9% 2	4579
	11th to 20th	Day	52% 7% 16% 14% 11% 1	4766
	21st to end	Day	55% 5% 9% 17% 14% 1	6102
April	1st to 10th	Day	58% 5% 8% 18% 10% 1	2520
	11th to 20th	Day	50% 6% 9% 21% 13% 1	2494
	21st to end	Day	53% 5% 10% 18% 11% 2	2730
May	1st to 10th	Day	60% 6% 9% 18% 6% 1	6301
	11th to 20th	Day	50% 9% 15% 16% 8% 1	6406
	21st to end	Day	50% 7% 11% 19% 11% 1	6949
June	1st to 10th	Day	51% 8% 10% 19% 10% 1	2800
	11th to 20th	Day	42% 7% 13% 24% 12% 2	2800
	21st to end	Day	51% 8% 11% 20% 9% 1	2800
July	1st to 10th	Day	46% 8% 15% 24% 7%	6290
	11th to 20th	Day	38% 8% 15% 30% 9%	6285
	21st to end	Day	35% 7% 15% 35% 8%	6728
August	1st to 10th	Day	46% 8% 17% 22% 6%	4549
	11th to 20th	Day	42% 8% 20% 23% 6%	4194
	21st to end	Day	43% 7% 15% 21% 13%	4312
September	1st to 10th	Day	36% 9% 15% 29% 10% 1	2400
	11th to 20th	Day	35% 6% 13% 32% 13%	2283
	21st to end	Day	43% 7% 14% 25% 11%	2200
October	1st to 10th	Day	43% 7% 15% 28% 7%	3438
	11th to 20th	Day	44% 8% 18% 25% 6%	3095
	21st to end	Day	47% 6% 19% 21% 7% 1	3180
November	1st to 10th	Day	52% 7% 12% 20% 8% 1	1851
	11th to 20th	Day	54% 8% 12% 16% 9%	1849
	21st to end	Day	62% 8% 11% 13% 5%	1680
December	1st to 10th	Day	71% 6% 7% 13% 3	2680
	11th to 20th	Day	61% 5% 8% 17% 8%	3066
	21st to end	Day	66% 7% 11% 10% 6%	4048
January	1st to 10th	Night	68% 6% 10% 11% 4 1	8234
	11th to 20th	Night	71% 7% 8% 9% 5%	8280
	21st to end	Night	62% 5% 8% 12% 12%	9057
February	1st to 10th	Night	64% 6% 9% 15% 7% 1	2822
	11th to 20th	Night	60% 6% 9% 16% 8%	2517
	21st to end	Night	57% 6% 9% 16% 11% 1	2076
March	1st to 10th	Night	59% 4 8% 14% 11% 4	5494
	11th to 20th	Night	54% 6% 13% 14% 11% 1	5411
	21st to end	Night	58% 5% 6% 19% 11% 2	5072
April	1st to 10th	Night	56% 5% 8% 18% 12% 1	2100
	11th to 20th	Night	53% 6% 7% 19% 13% 2	2073
	21st to end	Night	50% 5% 9% 19% 15% 3	1890
May	1st to 10th	Night	60% 7% 9% 16% 6% 2	3920
	11th to 20th	Night	53% 8% 10% 19% 9% 1	3624
	21st to end	Night	52% 6% 10% 17% 14% 1	3927
June	1st to 10th	Night	51% 7% 9% 21% 11% 1	1600
	11th to 20th	Night	45% 7% 11% 21% 13% 3	1600
	21st to end	Night	49% 8% 11% 18% 13% 1	1600
July	1st to 10th	Night	46% 7% 18% 20% 8%	3560
	11th to 20th	Night	41% 7% 15% 26% 10%	3552
	21st to end	Night	39% 7% 17% 26% 11%	3809
August	1st to 10th	Night	47% 7% 13% 25% 7%	2576
	11th to 20th	Night	46% 8% 17% 22% 8%	2882
	21st to end	Night	43% 7% 12% 23% 14% 1	3586
September	1st to 10th	Night	38% 8% 13% 26% 15% 1	2000
	11th to 20th	Night	35% 6% 14% 32% 12% 1	2115
	21st to end	Night	43% 7% 10% 25% 15% 1	2200
October	1st to 10th	Night	46% 6% 13% 24% 11%	3740
	11th to 20th	Night	46% 5% 11% 29% 8%	4043
	21st to end	Night	51% 4 14% 18% 11% 2	4610
November	1st to 10th	Night	54% 6% 12% 21% 6% 1	2667
	11th to 20th	Night	55% 6% 11% 17% 9% 2	2767
	21st to end	Night	62% 6% 12% 15% 6%	2940
December	1st to 10th	Night	74% 5% 10% 9% 3	4720
	11th to 20th	Night	63% 6% 8% 14% 9%	5348
	21st to end	Night	64% 5% 9% 14% 8%	7150

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	30% 15% 30% 19% 6%	220
	11th to 20th	Day	28% 22% 31% 15% 4	220
	21st to end	Day	20% 20% 29% 23% 6% 2	242
February	1st to 10th	Day	28% 17% 31% 19% 5%	281
	11th to 20th	Day	24% 17% 32% 23% 4	479
	21st to end	Day	23% 18% 33% 23% 3	446
March	1st to 10th	Day	23% 16% 33% 23% 5%	540
	11th to 20th	Day	24% 16% 34% 21% 5% 1	540
	21st to end	Day	28% 16% 29% 22% 6% 1	594
April	1st to 10th	Day	30% 13% 30% 19% 6% 1	540
	11th to 20th	Day	29% 20% 23% 18% 7% 2	532
	21st to end	Day	28% 16% 31% 14% 8% 2	540
May	1st to 10th	Day	27% 13% 31% 19% 9% 1	543
	11th to 20th	Day	19% 12% 28% 26% 12% 3	551
	21st to end	Day	20% 15% 33% 22% 9% 2	573
June	1st to 10th	Day	25% 12% 28% 26% 8% 2	530
	11th to 20th	Day	17% 10% 29% 30% 12% 1	530
	21st to end	Day	23% 10% 30% 23% 11% 2	530
July	1st to 10th	Day	14% 7% 30% 29% 19% 2	525
	11th to 20th	Day	14% 8% 31% 33% 12% 3	524
	21st to end	Day	15% 8% 28% 32% 15% 2	576
August	1st to 10th	Day	14% 6% 25% 33% 17% 5%	526
	11th to 20th	Day	14% 6% 22% 32% 19% 6%	519
	21st to end	Day	16% 11% 24% 24% 16% 9%	583
September	1st to 10th	Day	13% 9% 31% 28% 14% 6%	530
	11th to 20th	Day	15% 7% 21% 26% 20% 11%	530
	21st to end	Day	19% 10% 25% 24% 17% 6%	530
October	1st to 10th	Day	19% 12% 28% 24% 12% 5%	530
	11th to 20th	Day	24% 14% 29% 20% 12% 2	484
	21st to end	Day	33% 10% 29% 21% 7%	462
November	1st to 10th	Day	27% 17% 30% 20% 6%	425
	11th to 20th	Day	27% 19% 25% 20% 8% 2	389
	21st to end	Day	31% 17% 31% 14% 6%	220
December	1st to 10th	Day	30% 13% 26% 22% 5% 3	220
	11th to 20th	Day	26% 22% 34% 15% 3 1	220
	21st to end	Day	29% 20% 28% 17% 5% 2	242
January	1st to 10th	Night	29% 12% 30% 24% 5%	840
	11th to 20th	Night	27% 15% 30% 21% 7%	840
	21st to end	Night	21% 11% 32% 27% 7%	924
February	1st to 10th	Night	24% 11% 33% 26% 5%	840
	11th to 20th	Night	21% 15% 35% 24% 4	823
	21st to end	Night	23% 14% 31% 28% 4	692
March	1st to 10th	Night	24% 12% 31% 27% 5%	840
	11th to 20th	Night	25% 13% 31% 24% 7%	840
	21st to end	Night	24% 13% 28% 27% 7% 1	924
April	1st to 10th	Night	29% 12% 28% 26% 5%	840
	11th to 20th	Night	27% 13% 28% 25% 6%	829
	21st to end	Night	28% 12% 30% 23% 7% 1	630
May	1st to 10th	Night	27% 9% 32% 24% 7% 1	530
	11th to 20th	Night	24% 8% 28% 30% 9% 1	406
	21st to end	Night	21% 8% 31% 33% 7%	433
June	1st to 10th	Night	27% 7% 28% 31% 7% 1	400
	11th to 20th	Night	19% 6% 30% 34% 12%	400
	21st to end	Night	17% 7% 28% 37% 11% 1	400
July	1st to 10th	Night	14% 6% 26% 41% 12% 1	390
	11th to 20th	Night	13% 3 24% 44% 15% 1	388
	21st to end	Night	12% 6% 24% 44% 13%	438
August	1st to 10th	Night	16% 5% 17% 40% 20% 1	398
	11th to 20th	Night	14% 4 20% 36% 24% 2	574
	21st to end	Night	17% 5% 23% 35% 18% 2	880
September	1st to 10th	Night	15% 6% 26% 35% 16% 1	800
	11th to 20th	Night	16% 6% 20% 33% 22% 3	800
	21st to end	Night	20% 7% 26% 30% 16% 2	800
October	1st to 10th	Night	19% 9% 28% 30% 14% 1	800
	11th to 20th	Night	26% 10% 27% 29% 9% 1	800
	21st to end	Night	28% 13% 29% 24% 6%	880
November	1st to 10th	Night	28% 14% 30% 22% 6%	820
	11th to 20th	Night	25% 15% 30% 22% 8% 1	840
	21st to end	Night	30% 16% 27% 21% 5%	840
December	1st to 10th	Night	33% 14% 26% 22% 6%	840
	11th to 20th	Night	29% 15% 29% 20% 6% 1	840
	21st to end	Night	35% 13% 26% 21% 5%	924

Page generated at 2026-05-14 01:58:57. Version ac07

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