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 2025-01-22.

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	18% 10% 3 8% 5% 4 4 4 5% 7% 32%	105259
	Night	19% 12% 4 9% 5% 4 4 3 5% 5% 30%	104124
Transparency	Day	50% 7% 13% 20% 8% 1	108720
	Night	54% 6% 11% 18% 9% 1	108752
Seeing	Day	22% 13% 28% 23% 10% 3	14780
	Night	24% 11% 28% 28% 9% 1	23821

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	20% 17% 6% 13% 5% 5% 3 2 3 4 22%	2597
	11th to 20th	Day	15% 15% 6% 10% 6% 4 4 3 4 6% 27%	2600
	21st to end	Day	14% 16% 6% 11% 6% 6% 5% 4 4 5% 23%	2780
February	1st to 10th	Day	17% 17% 4 10% 6% 5% 5% 3 5% 4 24%	1624
	11th to 20th	Day	14% 16% 5% 11% 6% 5% 4 3 5% 6% 25%	1796
	21st to end	Day	19% 15% 4 8% 6% 5% 3 3 5% 5% 27%	1570
March	1st to 10th	Day	20% 12% 4 9% 6% 5% 5% 4 3 5% 27%	3116
	11th to 20th	Day	16% 16% 5% 10% 5% 4 4 3 4 5% 27%	3262
	21st to end	Day	16% 11% 4 8% 5% 4 4 3 4 5% 37%	4166
April	1st to 10th	Day	23% 12% 3 8% 5% 4 4 3 4 5% 29%	2280
	11th to 20th	Day	21% 8% 2 6% 4 4 4 4 4 5% 37%	2254
	21st to end	Day	23% 9% 3 7% 4 3 4 4 4 6% 31%	2470
May	1st to 10th	Day	22% 8% 3 7% 5% 4 4 4 6% 6% 30%	4290
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	4398
	21st to end	Day	15% 6% 2 7% 5% 5% 5% 4 6% 9% 35%	4837
June	1st to 10th	Day	23% 7% 2 6% 4 4 5% 4 6% 7% 30%	2660
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 4 6% 7% 39%	2660
	21st to end	Day	21% 9% 3 7% 4 5% 4 4 6% 8% 30%	2660
July	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 4 7% 9% 36%	4440
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 4 8% 9% 36%	4440
	21st to end	Day	13% 6% 2 5% 5% 3 4 4 6% 8% 44%	4814
August	1st to 10th	Day	15% 7% 3 8% 6% 5% 5% 4 7% 9% 31%	4423
	11th to 20th	Day	16% 6% 3 7% 4 4 5% 4 7% 9% 36%	4024
	21st to end	Day	17% 6% 2 7% 4 4 5% 3 5% 7% 39%	4180
September	1st to 10th	Day	12% 6% 2 5% 4 4 5% 6% 6% 8% 42%	2280
	11th to 20th	Day	16% 6% 2 5% 3 2 3 3 5% 7% 48%	2169
	21st to end	Day	19% 5% 2 7% 4 4 4 3 6% 7% 40%	2090
October	1st to 10th	Day	20% 7% 2 8% 5% 3 5% 4 6% 7% 33%	2008
	11th to 20th	Day	20% 8% 2 8% 6% 5% 5% 4 6% 6% 30%	1822
	21st to end	Day	25% 10% 4 6% 5% 4 4 3 4 5% 30%	1881
November	1st to 10th	Day	18% 11% 3 7% 5% 4 4 4 5% 6% 33%	1761
	11th to 20th	Day	18% 12% 4 8% 5% 4 5% 4 4 7% 29%	1761
	21st to end	Day	24% 14% 4 8% 5% 5% 5% 4 5% 6% 24%	1600
December	1st to 10th	Day	20% 19% 5% 13% 6% 5% 4 2 4 5% 17%	2600
	11th to 20th	Day	20% 15% 5% 10% 5% 3 4 3 4 6% 25%	2986
	21st to end	Day	23% 14% 5% 9% 5% 6% 5% 5% 6% 4 17%	3960
January	1st to 10th	Night	18% 19% 6% 11% 5% 4 4 3 4 4 22%	4569
	11th to 20th	Night	13% 16% 6% 14% 7% 6% 5% 4 4 5% 21%	4580
	21st to end	Night	17% 18% 7% 11% 7% 4 4 3 3 4 23%	4899
February	1st to 10th	Night	16% 17% 5% 12% 6% 6% 4 3 5% 6% 20%	2554
	11th to 20th	Night	15% 14% 5% 11% 6% 6% 4 3 4 4 27%	2270
	21st to end	Night	16% 15% 5% 8% 6% 4 4 3 5% 5% 30%	1884
March	1st to 10th	Night	22% 11% 3 8% 4 4 4 3 4 4 33%	3724
	11th to 20th	Night	20% 18% 5% 8% 5% 4 3 2 4 4 27%	3695
	21st to end	Night	14% 13% 5% 11% 5% 4 4 3 4 4 35%	3466
April	1st to 10th	Night	25% 10% 4 7% 4 4 4 3 5% 5% 29%	1900
	11th to 20th	Night	23% 9% 3 6% 5% 4 4 3 5% 6% 33%	1873
	21st to end	Night	23% 10% 3 6% 4 4 3 3 4 5% 35%	1710
May	1st to 10th	Night	25% 9% 3 7% 4 5% 4 4 4 7% 29%	2679
	11th to 20th	Night	24% 8% 2 7% 5% 4 4 4 5% 6% 33%	2495
	21st to end	Night	17% 7% 3 7% 5% 4 5% 4 5% 8% 37%	2738
June	1st to 10th	Night	23% 8% 3 6% 4 4 4 4 6% 7% 31%	1520
	11th to 20th	Night	18% 5% 2 7% 4 3 5% 4 6% 8% 37%	1520
	21st to end	Night	18% 8% 3 7% 5% 4 4 5% 6% 7% 33%	1520
July	1st to 10th	Night	14% 7% 3 7% 5% 6% 5% 4 7% 8% 33%	2520
	11th to 20th	Night	15% 6% 2 5% 5% 5% 5% 4 6% 7% 40%	2520
	21st to end	Night	12% 6% 2 7% 5% 5% 5% 4 6% 7% 40%	2739
August	1st to 10th	Night	17% 9% 3 8% 4 4 5% 3 6% 7% 34%	2506
	11th to 20th	Night	16% 7% 3 8% 5% 5% 4 4 6% 6% 36%	2767
	21st to end	Night	18% 6% 2 7% 4 4 5% 4 5% 7% 39%	3476
September	1st to 10th	Night	15% 5% 2 7% 4 4 4 4 5% 7% 44%	1900
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 6% 7% 48%	2009
	21st to end	Night	17% 6% 2 6% 4 4 3 3 5% 8% 41%	2090
October	1st to 10th	Night	18% 7% 3 7% 4 4 3 4 5% 6% 39%	2171
	11th to 20th	Night	22% 8% 3 8% 4 5% 4 3 4 5% 33%	2357
	21st to end	Night	24% 9% 4 9% 5% 4 4 3 4 5% 29%	2717
November	1st to 10th	Night	19% 13% 3 6% 5% 4 5% 4 5% 5% 31%	2537
	11th to 20th	Night	20% 12% 3 7% 5% 4 4 3 4 5% 31%	2635
	21st to end	Night	23% 15% 4 9% 4 4 4 3 4 4 27%	2800
December	1st to 10th	Night	19% 20% 7% 13% 6% 5% 4 3 3 4 15%	4580
	11th to 20th	Night	24% 13% 4 9% 6% 4 3 3 4 5% 24%	5208
	21st to end	Night	23% 17% 5% 9% 4 4 4 4 6% 5% 20%	6996

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	67% 7% 11% 12% 3	2598
	11th to 20th	Day	60% 9% 11% 16% 5%	2600
	21st to end	Day	61% 10% 12% 13% 4	2780
February	1st to 10th	Day	63% 6% 9% 16% 5% 1	1624
	11th to 20th	Day	61% 6% 12% 14% 7% 1	1805
	21st to end	Day	59% 5% 11% 15% 8% 1	1570
March	1st to 10th	Day	59% 8% 8% 17% 7% 1	3119
	11th to 20th	Day	59% 7% 12% 11% 10% 2	3262
	21st to end	Day	48% 5% 10% 19% 15% 1	4166
April	1st to 10th	Day	58% 5% 8% 17% 9% 1	2280
	11th to 20th	Day	49% 6% 9% 22% 13% 1	2254
	21st to end	Day	54% 6% 10% 18% 10% 2	2470
May	1st to 10th	Day	51% 8% 11% 21% 8% 1	4304
	11th to 20th	Day	48% 10% 16% 16% 8% 1	4402
	21st to end	Day	43% 9% 12% 23% 12% 1	4837
June	1st to 10th	Day	51% 8% 11% 20% 9% 1	2660
	11th to 20th	Day	42% 7% 13% 23% 13% 2	2660
	21st to end	Day	52% 8% 11% 19% 9%	2660
July	1st to 10th	Day	42% 8% 15% 27% 8%	4370
	11th to 20th	Day	42% 8% 17% 28% 5%	4365
	21st to end	Day	38% 8% 15% 32% 8%	4661
August	1st to 10th	Day	47% 9% 17% 22% 6%	4409
	11th to 20th	Day	43% 8% 20% 23% 6%	4064
	21st to end	Day	43% 7% 15% 21% 14%	4180
September	1st to 10th	Day	37% 10% 15% 27% 10% 1	2280
	11th to 20th	Day	36% 7% 13% 31% 12%	2169
	21st to end	Day	43% 7% 14% 25% 11%	2090
October	1st to 10th	Day	44% 7% 15% 27% 6%	3333
	11th to 20th	Day	45% 8% 18% 24% 5%	2999
	21st to end	Day	46% 6% 19% 21% 7% 1	3081
November	1st to 10th	Day	51% 8% 12% 21% 8% 1	1761
	11th to 20th	Day	54% 8% 12% 16% 9%	1761
	21st to end	Day	62% 9% 12% 14% 5%	1600
December	1st to 10th	Day	71% 6% 8% 13% 2	2600
	11th to 20th	Day	61% 5% 8% 17% 8%	2986
	21st to end	Day	67% 7% 11% 10% 6%	3960
January	1st to 10th	Night	64% 8% 13% 10% 4	4569
	11th to 20th	Night	64% 10% 10% 12% 4	4580
	21st to end	Night	65% 7% 10% 12% 6%	4899
February	1st to 10th	Night	65% 6% 9% 14% 6% 1	2554
	11th to 20th	Night	60% 6% 9% 16% 8%	2272
	21st to end	Night	57% 6% 9% 15% 11% 1	1884
March	1st to 10th	Night	55% 5% 10% 18% 9% 3	3734
	11th to 20th	Night	60% 6% 9% 11% 12% 2	3696
	21st to end	Night	52% 6% 7% 20% 13% 2	3466
April	1st to 10th	Night	56% 5% 8% 18% 12% 1	1900
	11th to 20th	Night	52% 6% 8% 20% 13% 2	1873
	21st to end	Night	51% 5% 9% 18% 14% 3	1710
May	1st to 10th	Night	54% 8% 10% 18% 8% 2	2685
	11th to 20th	Night	48% 8% 12% 19% 10% 2	2496
	21st to end	Night	44% 7% 11% 20% 17% 2	2739
June	1st to 10th	Night	51% 6% 10% 21% 11% 1	1520
	11th to 20th	Night	44% 7% 11% 21% 13% 3	1520
	21st to end	Night	49% 8% 11% 18% 13% 1	1520
July	1st to 10th	Night	46% 7% 15% 20% 11%	2480
	11th to 20th	Night	40% 8% 16% 26% 9%	2472
	21st to end	Night	41% 7% 18% 22% 12%	2651
August	1st to 10th	Night	49% 7% 13% 24% 7%	2496
	11th to 20th	Night	47% 8% 17% 21% 7%	2793
	21st to end	Night	44% 7% 12% 22% 14% 1	3476
September	1st to 10th	Night	39% 8% 13% 24% 15% 1	1900
	11th to 20th	Night	35% 6% 15% 32% 12% 1	2009
	21st to end	Night	42% 7% 10% 25% 15% 1	2090
October	1st to 10th	Night	47% 6% 13% 24% 10%	3626
	11th to 20th	Night	47% 5% 11% 29% 7%	3919
	21st to end	Night	51% 4 14% 18% 11% 2	4467
November	1st to 10th	Night	54% 6% 12% 20% 7% 1	2537
	11th to 20th	Night	55% 6% 11% 17% 10% 2	2635
	21st to end	Night	61% 6% 12% 16% 5%	2800
December	1st to 10th	Night	74% 5% 10% 9% 3	4580
	11th to 20th	Night	63% 6% 8% 14% 9%	5208
	21st to end	Night	64% 5% 9% 14% 8%	6996

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	32% 15% 30% 17% 7%	200
	11th to 20th	Day	27% 21% 32% 17% 4	200
	21st to end	Day	22% 18% 27% 26% 6% 2	200
February	1st to 10th	Day	32% 20% 28% 17% 3	229
	11th to 20th	Day	25% 17% 33% 21% 3	404
	21st to end	Day	25% 19% 30% 24% 3	382
March	1st to 10th	Day	25% 14% 31% 25% 5%	460
	11th to 20th	Day	22% 18% 35% 19% 5% 1	460
	21st to end	Day	27% 16% 27% 23% 6% 1	506
April	1st to 10th	Day	30% 12% 30% 20% 7% 2	460
	11th to 20th	Day	30% 19% 24% 18% 7% 3	452
	21st to end	Day	28% 17% 30% 14% 8% 2	460
May	1st to 10th	Day	25% 13% 31% 19% 10% 2	463
	11th to 20th	Day	18% 13% 28% 26% 12% 3	487
	21st to end	Day	19% 15% 34% 22% 9% 2	529
June	1st to 10th	Day	25% 12% 27% 26% 8% 2	490
	11th to 20th	Day	17% 10% 29% 30% 12% 1	490
	21st to end	Day	23% 10% 30% 22% 12% 3	490
July	1st to 10th	Day	14% 6% 29% 30% 19% 2	485
	11th to 20th	Day	15% 8% 30% 33% 12% 3	484
	21st to end	Day	16% 8% 26% 33% 15% 2	532
August	1st to 10th	Day	16% 7% 26% 31% 17% 4	486
	11th to 20th	Day	14% 6% 23% 32% 19% 6%	479
	21st to end	Day	16% 11% 23% 25% 15% 9%	539
September	1st to 10th	Day	13% 9% 31% 28% 13% 6%	490
	11th to 20th	Day	16% 7% 22% 26% 19% 10%	490
	21st to end	Day	19% 10% 24% 24% 18% 6%	490
October	1st to 10th	Day	21% 12% 29% 22% 12% 4	490
	11th to 20th	Day	25% 15% 28% 20% 11% 2	448
	21st to end	Day	33% 11% 29% 21% 7%	429
November	1st to 10th	Day	26% 16% 30% 21% 7%	395
	11th to 20th	Day	26% 20% 26% 19% 8% 1	361
	21st to end	Day	31% 18% 31% 15% 6% 1	200
December	1st to 10th	Day	33% 13% 24% 22% 5% 4	200
	11th to 20th	Day	27% 23% 33% 14% 4 1	200
	21st to end	Day	30% 20% 26% 17% 5% 2	220
January	1st to 10th	Night	30% 12% 30% 23% 5%	800
	11th to 20th	Night	27% 14% 31% 21% 8%	800
	21st to end	Night	22% 10% 32% 28% 7%	841
February	1st to 10th	Night	26% 11% 34% 25% 4	760
	11th to 20th	Night	20% 15% 35% 25% 4 1	743
	21st to end	Night	24% 14% 31% 28% 4	628
March	1st to 10th	Night	25% 11% 30% 29% 5%	760
	11th to 20th	Night	26% 13% 29% 24% 7%	760
	21st to end	Night	24% 12% 28% 27% 8% 1	836
April	1st to 10th	Night	29% 11% 27% 28% 5%	760
	11th to 20th	Night	27% 13% 28% 25% 7%	749
	21st to end	Night	29% 12% 28% 24% 7% 1	570
May	1st to 10th	Night	27% 9% 33% 24% 8% 1	480
	11th to 20th	Night	24% 8% 28% 30% 9% 1	374
	21st to end	Night	20% 9% 32% 32% 7%	411
June	1st to 10th	Night	27% 7% 27% 31% 8% 1	380
	11th to 20th	Night	19% 6% 29% 33% 12%	380
	21st to end	Night	17% 7% 27% 37% 12% 1	380
July	1st to 10th	Night	14% 6% 26% 40% 12% 1	370
	11th to 20th	Night	13% 3 25% 44% 15% 1	368
	21st to end	Night	12% 7% 24% 44% 13%	416
August	1st to 10th	Night	17% 5% 17% 40% 20% 1	378
	11th to 20th	Night	14% 4 20% 36% 23% 2	545
	21st to end	Night	17% 5% 23% 35% 18% 2	836
September	1st to 10th	Night	16% 6% 26% 35% 16% 1	760
	11th to 20th	Night	17% 6% 20% 32% 21% 3	760
	21st to end	Night	20% 7% 25% 30% 16% 2	760
October	1st to 10th	Night	19% 10% 29% 29% 13% 1	760
	11th to 20th	Night	27% 10% 26% 28% 9% 1	760
	21st to end	Night	29% 12% 29% 24% 6%	836
November	1st to 10th	Night	27% 14% 31% 22% 6% 1	780
	11th to 20th	Night	25% 15% 30% 21% 8% 1	800
	21st to end	Night	31% 16% 26% 21% 6% 1	800
December	1st to 10th	Night	34% 14% 25% 22% 6%	800
	11th to 20th	Night	30% 14% 29% 20% 6% 1	800
	21st to end	Night	35% 13% 25% 21% 5%	880

Page generated at 2025-01-19 03:06:47. Version ac07

Copyright © 2025 Attilla Danko.