St-Valérien-de-Milton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the St-Valérien-de-Milton clear sky chart from 2005-11-06 to 2026-06-16.

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	18% 11% 4 9% 5% 5% 4 4 5% 7% 29%	137729
	Night	18% 13% 4 10% 5% 4 4 3 5% 6% 27%	134314
Transparency	Day	54% 6% 12% 20% 8% 1	141187
	Night	58% 5% 10% 17% 9% 1	138945
Seeing	Day	26% 16% 29% 20% 8% 2	16605
	Night	26% 13% 28% 24% 8% 1	25545

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	18% 21% 6% 15% 5% 5% 3 3 3 4 17%	4661
	11th to 20th	Day	12% 17% 7% 17% 9% 6% 5% 3 4 5% 15%	4650
	21st to end	Day	9% 15% 6% 13% 10% 8% 6% 4 5% 5% 19%	5124
February	1st to 10th	Day	15% 17% 5% 11% 6% 5% 5% 4 4 4 23%	1781
	11th to 20th	Day	15% 17% 6% 12% 6% 5% 4 2 5% 6% 21%	2005
	21st to end	Day	15% 17% 5% 9% 7% 6% 4 3 5% 6% 23%	1730
March	1st to 10th	Day	19% 14% 6% 12% 6% 5% 5% 2 4 5% 21%	4576
	11th to 20th	Day	14% 15% 4 9% 5% 5% 4 3 5% 7% 29%	4761
	21st to end	Day	20% 13% 5% 9% 5% 4 4 3 4 5% 29%	6102
April	1st to 10th	Day	22% 14% 3 9% 5% 4 4 3 4 5% 27%	2520
	11th to 20th	Day	22% 10% 2 7% 4 4 4 3 5% 5% 34%	2508
	21st to end	Day	24% 11% 3 6% 4 4 4 3 4 5% 31%	2730
May	1st to 10th	Day	27% 10% 4 8% 4 5% 5% 4 5% 6% 22%	7932
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 8% 29%	8221
	21st to end	Day	21% 9% 3 7% 4 5% 4 4 5% 7% 32%	9060
June	1st to 10th	Day	23% 8% 3 6% 4 4 5% 4 5% 7% 31%	2940
	11th to 20th	Day	16% 6% 3 6% 4 4 5% 4 6% 9% 36%	2870
	21st to end	Day	22% 9% 3 7% 5% 4 5% 4 6% 7% 29%	2800
July	1st to 10th	Day	15% 8% 3 8% 6% 6% 5% 5% 7% 10% 29%	6360
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 5% 7% 9% 38%	6360
	21st to end	Day	13% 6% 2 5% 4 4 4 4 6% 10% 43%	6926
August	1st to 10th	Day	17% 7% 2 8% 5% 5% 5% 5% 7% 9% 31%	4563
	11th to 20th	Day	18% 6% 3 7% 5% 4 5% 4 6% 9% 34%	4157
	21st to end	Day	19% 6% 2 7% 4 4 4 3 6% 7% 39%	4312
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 5% 8% 42%	2400
	11th to 20th	Day	16% 6% 2 4 3 3 3 3 5% 7% 46%	2271
	21st to end	Day	19% 7% 2 6% 3 4 4 3 6% 7% 39%	2200
October	1st to 10th	Day	20% 8% 3 7% 5% 4 5% 4 5% 7% 33%	2130
	11th to 20th	Day	21% 9% 3 9% 5% 5% 4 4 6% 6% 29%	1906
	21st to end	Day	27% 12% 3 7% 4 4 4 3 4 5% 27%	1980
November	1st to 10th	Day	20% 14% 3 7% 5% 4 3 4 5% 5% 30%	1851
	11th to 20th	Day	18% 16% 5% 9% 5% 5% 4 2 5% 5% 25%	1868
	21st to end	Day	24% 16% 5% 8% 4 4 5% 3 5% 6% 20%	1680
December	1st to 10th	Day	20% 21% 6% 13% 6% 3 4 3 4 3 15%	2680
	11th to 20th	Day	21% 17% 5% 10% 5% 4 3 3 4 5% 23%	3066
	21st to end	Day	22% 16% 5% 11% 6% 4 4 3 6% 5% 17%	4048
January	1st to 10th	Night	15% 22% 8% 14% 5% 4 4 3 3 4 19%	8234
	11th to 20th	Night	13% 20% 7% 18% 8% 6% 5% 3 4 4 13%	8235
	21st to end	Night	10% 15% 6% 14% 10% 6% 4 3 5% 5% 22%	9057
February	1st to 10th	Night	14% 16% 6% 13% 7% 5% 4 4 4 5% 21%	2835
	11th to 20th	Night	14% 16% 5% 13% 7% 5% 4 3 4 5% 25%	2500
	21st to end	Night	15% 17% 5% 10% 5% 4 4 3 4 4 28%	2076
March	1st to 10th	Night	21% 14% 5% 9% 6% 4 4 2 4 4 28%	5484
	11th to 20th	Night	16% 16% 5% 9% 5% 4 5% 3 5% 6% 27%	5414
	21st to end	Night	17% 16% 5% 10% 5% 4 4 3 4 4 28%	5072
April	1st to 10th	Night	24% 13% 2 8% 5% 3 4 3 5% 5% 28%	2100
	11th to 20th	Night	24% 10% 2 7% 5% 4 3 3 5% 5% 32%	2060
	21st to end	Night	22% 11% 3 7% 3 4 4 3 4 6% 34%	1890
May	1st to 10th	Night	26% 10% 4 8% 5% 5% 4 3 5% 6% 24%	5022
	11th to 20th	Night	23% 7% 3 8% 5% 5% 5% 4 5% 6% 29%	4639
	21st to end	Night	19% 10% 3 7% 4 4 5% 3 5% 7% 32%	5114
June	1st to 10th	Night	24% 8% 2 5% 4 4 5% 4 6% 7% 32%	1680
	11th to 20th	Night	19% 6% 2 5% 5% 5% 4 4 6% 6% 37%	1640
	21st to end	Night	19% 8% 2 8% 4 5% 4 5% 5% 7% 33%	1600
July	1st to 10th	Night	15% 8% 2 9% 6% 5% 6% 5% 7% 8% 30%	3600
	11th to 20th	Night	17% 6% 2 6% 5% 4 4 4 5% 7% 39%	3600
	21st to end	Night	12% 6% 2 7% 5% 4 5% 4 7% 9% 40%	3926
August	1st to 10th	Night	19% 8% 4 7% 4 4 4 4 6% 6% 34%	2586
	11th to 20th	Night	16% 7% 3 7% 5% 5% 5% 4 5% 6% 36%	2840
	21st to end	Night	18% 7% 3 6% 4 4 4 4 4 8% 39%	3586
September	1st to 10th	Night	16% 6% 2 7% 4 4 3 3 5% 6% 44%	2000
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 8% 49%	2128
	21st to end	Night	18% 6% 3 6% 4 4 4 3 4 8% 41%	2200
October	1st to 10th	Night	19% 7% 2 7% 4 5% 4 3 5% 6% 39%	2268
	11th to 20th	Night	21% 10% 3 7% 5% 5% 4 3 4 5% 33%	2492
	21st to end	Night	25% 11% 3 8% 4 4 4 3 4 5% 28%	2860
November	1st to 10th	Night	22% 13% 3 8% 4 4 4 3 4 5% 29%	2667
	11th to 20th	Night	21% 14% 4 8% 5% 4 4 3 4 5% 29%	2751
	21st to end	Night	23% 17% 5% 8% 5% 4 3 2 3 5% 24%	2940
December	1st to 10th	Night	18% 24% 8% 13% 6% 5% 3 3 3 4 13%	4720
	11th to 20th	Night	23% 16% 5% 11% 6% 5% 4 3 3 3 22%	5348
	21st to end	Night	22% 18% 4 9% 4 4 4 3 5% 7% 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	73% 4 8% 13% 2	4662
	11th to 20th	Day	71% 6% 7% 11% 5%	4680
	21st to end	Day	66% 6% 8% 11% 9%	5124
February	1st to 10th	Day	66% 5% 8% 15% 5% 1	1781
	11th to 20th	Day	65% 4 11% 14% 5% 1	2014
	21st to end	Day	63% 4 10% 15% 7% 1	1730
March	1st to 10th	Day	66% 5% 7% 13% 7% 2	4579
	11th to 20th	Day	54% 6% 15% 13% 11% 1	4761
	21st to end	Day	58% 4 8% 16% 13% 1	6102
April	1st to 10th	Day	61% 5% 8% 18% 8% 1	2520
	11th to 20th	Day	52% 5% 8% 20% 13% 1	2508
	21st to end	Day	55% 5% 9% 18% 11% 2	2730
May	1st to 10th	Day	61% 6% 8% 18% 7%	7944
	11th to 20th	Day	51% 7% 14% 19% 7% 1	8225
	21st to end	Day	51% 6% 10% 23% 9% 1	9061
June	1st to 10th	Day	52% 7% 10% 20% 10% 1	2940
	11th to 20th	Day	44% 7% 14% 23% 12% 2	2870
	21st to end	Day	54% 7% 10% 19% 9%	2800
July	1st to 10th	Day	49% 7% 14% 24% 6%	6290
	11th to 20th	Day	41% 8% 14% 29% 8%	6285
	21st to end	Day	37% 6% 15% 35% 7%	6728
August	1st to 10th	Day	48% 8% 16% 22% 6%	4549
	11th to 20th	Day	45% 8% 20% 22% 6%	4197
	21st to end	Day	44% 6% 15% 21% 13% 1	4312
September	1st to 10th	Day	39% 7% 15% 29% 9% 1	2400
	11th to 20th	Day	37% 6% 13% 31% 12%	2271
	21st to end	Day	44% 6% 14% 25% 11%	2200
October	1st to 10th	Day	45% 5% 14% 28% 7%	3468
	11th to 20th	Day	48% 7% 15% 26% 4	3083
	21st to end	Day	51% 5% 17% 20% 7% 1	3180
November	1st to 10th	Day	55% 6% 12% 20% 7%	1851
	11th to 20th	Day	61% 5% 10% 15% 8%	1868
	21st to end	Day	66% 6% 12% 13% 3	1680
December	1st to 10th	Day	74% 6% 7% 11% 2	2680
	11th to 20th	Day	65% 4 8% 16% 6%	3066
	21st to end	Day	68% 5% 11% 11% 6%	4048
January	1st to 10th	Night	70% 4 10% 11% 3 1	8234
	11th to 20th	Night	75% 5% 8% 9% 4	8280
	21st to end	Night	65% 4 7% 12% 11%	9057
February	1st to 10th	Night	66% 5% 8% 15% 6% 1	2835
	11th to 20th	Night	63% 4 9% 16% 7%	2502
	21st to end	Night	60% 4 9% 15% 11% 1	2076
March	1st to 10th	Night	61% 3 8% 15% 10% 3	5494
	11th to 20th	Night	57% 5% 12% 14% 10% 1	5415
	21st to end	Night	60% 3 6% 20% 9% 1	5072
April	1st to 10th	Night	58% 4 8% 17% 11% 1	2100
	11th to 20th	Night	55% 5% 8% 19% 12% 1	2060
	21st to end	Night	52% 5% 8% 19% 14% 2	1890
May	1st to 10th	Night	59% 6% 11% 16% 7% 1	5028
	11th to 20th	Night	53% 7% 10% 21% 8% 1	4640
	21st to end	Night	51% 6% 8% 20% 15% 1	5115
June	1st to 10th	Night	50% 6% 10% 22% 11% 1	1680
	11th to 20th	Night	45% 7% 11% 22% 13% 3	1640
	21st to end	Night	49% 7% 13% 19% 12% 1	1600
July	1st to 10th	Night	48% 8% 17% 19% 8%	3560
	11th to 20th	Night	44% 6% 15% 26% 9%	3552
	21st to end	Night	40% 7% 17% 26% 10%	3809
August	1st to 10th	Night	49% 7% 13% 25% 6%	2576
	11th to 20th	Night	47% 7% 17% 21% 7%	2866
	21st to end	Night	43% 6% 12% 24% 14% 1	3586
September	1st to 10th	Night	41% 6% 13% 27% 14% 1	2000
	11th to 20th	Night	36% 4 14% 32% 12% 1	2128
	21st to end	Night	43% 6% 10% 26% 14% 1	2200
October	1st to 10th	Night	49% 6% 11% 24% 10%	3710
	11th to 20th	Night	49% 5% 10% 29% 7%	4054
	21st to end	Night	52% 4 14% 18% 10% 2	4610
November	1st to 10th	Night	57% 5% 11% 20% 6% 1	2667
	11th to 20th	Night	58% 6% 10% 16% 8% 2	2751
	21st to end	Night	63% 5% 12% 16% 5%	2940
December	1st to 10th	Night	76% 4 9% 9% 2	4720
	11th to 20th	Night	69% 4 6% 14% 7%	5348
	21st to end	Night	65% 4 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	37% 14% 30% 15% 4	220
	11th to 20th	Day	33% 23% 31% 10% 3	220
	21st to end	Day	29% 18% 32% 16% 5% 1	242
February	1st to 10th	Day	32% 24% 27% 14% 3 1	273
	11th to 20th	Day	29% 21% 34% 13% 2	493
	21st to end	Day	28% 21% 32% 17% 2	446
March	1st to 10th	Day	29% 21% 26% 19% 4	540
	11th to 20th	Day	30% 21% 30% 15% 3 1	540
	21st to end	Day	32% 21% 25% 17% 4 1	594
April	1st to 10th	Day	35% 15% 29% 14% 6% 1	540
	11th to 20th	Day	36% 17% 25% 15% 5% 2	532
	21st to end	Day	32% 17% 32% 11% 6% 2	540
May	1st to 10th	Day	32% 16% 28% 17% 5% 1	543
	11th to 20th	Day	23% 15% 27% 24% 9% 1	567
	21st to end	Day	23% 19% 32% 18% 7% 1	617
June	1st to 10th	Day	26% 12% 35% 19% 6% 1	570
	11th to 20th	Day	19% 15% 33% 22% 10%	550
	21st to end	Day	26% 12% 33% 19% 8% 2	530
July	1st to 10th	Day	17% 12% 31% 26% 13% 2	525
	11th to 20th	Day	17% 11% 35% 27% 8% 2	524
	21st to end	Day	18% 10% 33% 30% 9% 1	576
August	1st to 10th	Day	17% 9% 29% 27% 15% 3	526
	11th to 20th	Day	17% 8% 28% 27% 17% 4	519
	21st to end	Day	19% 13% 25% 23% 14% 7%	583
September	1st to 10th	Day	15% 14% 31% 24% 11% 5%	530
	11th to 20th	Day	17% 10% 22% 26% 17% 8%	530
	21st to end	Day	21% 12% 27% 22% 14% 5%	530
October	1st to 10th	Day	22% 14% 28% 21% 10% 3	530
	11th to 20th	Day	28% 17% 24% 21% 9% 1	478
	21st to end	Day	38% 14% 27% 16% 5%	462
November	1st to 10th	Day	34% 17% 26% 17% 4	425
	11th to 20th	Day	31% 20% 24% 16% 7% 1	408
	21st to end	Day	33% 21% 30% 11% 5%	220
December	1st to 10th	Day	33% 19% 25% 18% 4 2	220
	11th to 20th	Day	34% 23% 28% 11% 3 1	220
	21st to end	Day	34% 20% 27% 14% 5% 1	242
January	1st to 10th	Night	31% 13% 33% 18% 4	840
	11th to 20th	Night	28% 18% 29% 20% 5%	840
	21st to end	Night	24% 14% 32% 24% 5%	924
February	1st to 10th	Night	25% 15% 35% 20% 5%	840
	11th to 20th	Night	24% 19% 33% 20% 4	823
	21st to end	Night	25% 15% 35% 22% 3	692
March	1st to 10th	Night	27% 16% 31% 22% 4	840
	11th to 20th	Night	28% 17% 28% 22% 5%	840
	21st to end	Night	28% 14% 29% 23% 5% 1	924
April	1st to 10th	Night	32% 13% 28% 23% 4	840
	11th to 20th	Night	29% 15% 26% 23% 6%	816
	21st to end	Night	30% 16% 27% 19% 8% 1	630
May	1st to 10th	Night	29% 9% 34% 20% 7% 1	548
	11th to 20th	Night	23% 12% 29% 27% 8%	414
	21st to end	Night	22% 8% 35% 28% 7%	455
June	1st to 10th	Night	28% 8% 29% 27% 8%	420
	11th to 20th	Night	21% 7% 31% 30% 12%	410
	21st to end	Night	20% 7% 29% 33% 11% 1	400
July	1st to 10th	Night	15% 7% 29% 36% 12% 1	390
	11th to 20th	Night	14% 6% 23% 39% 16% 1	388
	21st to end	Night	15% 6% 26% 41% 11%	438
August	1st to 10th	Night	18% 3 22% 38% 19% 1	398
	11th to 20th	Night	16% 4 24% 33% 22% 1	571
	21st to end	Night	19% 5% 25% 34% 15% 2	880
September	1st to 10th	Night	18% 7% 27% 33% 14% 1	800
	11th to 20th	Night	19% 6% 21% 30% 22% 2	800
	21st to end	Night	22% 6% 30% 26% 15% 2	800
October	1st to 10th	Night	22% 10% 29% 26% 12% 1	800
	11th to 20th	Night	28% 11% 26% 27% 8% 1	800
	21st to end	Night	31% 14% 29% 21% 5%	880
November	1st to 10th	Night	31% 16% 29% 18% 6%	820
	11th to 20th	Night	28% 18% 27% 18% 8% 1	840
	21st to end	Night	32% 21% 23% 19% 5%	840
December	1st to 10th	Night	35% 17% 27% 17% 4	840
	11th to 20th	Night	31% 18% 27% 17% 5% 1	840
	21st to end	Night	35% 17% 25% 18% 5%	924

Page generated at 2026-06-13 02:31:40. Version ac07

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