Sainte-Julie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sainte-Julie 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 9% 5% 5% 5% 4 5% 7% 31%	131949
	Night	17% 12% 4 9% 5% 5% 4 3 5% 6% 29%	130898
Transparency	Day	51% 6% 12% 21% 10% 1	135393
	Night	55% 5% 10% 18% 10% 1	135541
Seeing	Day	22% 12% 28% 24% 11% 3	16446
	Night	23% 9% 29% 28% 9% 1	25488

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% 18% 6% 14% 6% 5% 4 2 3 4 22%	4661
	11th to 20th	Day	13% 15% 6% 15% 7% 6% 4 3 4 6% 21%	4650
	21st to end	Day	10% 14% 4 11% 8% 8% 6% 4 5% 5% 24%	5124
February	1st to 10th	Day	15% 16% 4 11% 6% 5% 4 3 5% 5% 26%	1821
	11th to 20th	Day	14% 13% 5% 12% 7% 5% 4 4 5% 5% 26%	1970
	21st to end	Day	17% 15% 4 9% 7% 4 4 4 4 5% 27%	1730
March	1st to 10th	Day	18% 13% 5% 11% 7% 5% 5% 3 4 5% 24%	4576
	11th to 20th	Day	14% 13% 4 9% 5% 5% 4 4 5% 7% 31%	4789
	21st to end	Day	18% 11% 4 10% 5% 4 4 3 4 5% 32%	6102
April	1st to 10th	Day	22% 12% 3 8% 5% 4 4 3 4 5% 30%	2520
	11th to 20th	Day	21% 9% 2 7% 4 4 3 3 4 6% 36%	2494
	21st to end	Day	21% 9% 3 7% 5% 5% 4 3 4 6% 33%	2709
May	1st to 10th	Day	26% 11% 4 9% 5% 4 4 4 5% 6% 23%	6342
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 8% 29%	6402
	21st to end	Day	21% 8% 2 7% 4 4 5% 4 6% 8% 31%	6949
June	1st to 10th	Day	21% 8% 3 7% 5% 5% 5% 4 6% 7% 31%	2800
	11th to 20th	Day	15% 6% 2 6% 4 5% 5% 4 6% 9% 39%	2800
	21st to end	Day	20% 8% 3 6% 5% 4 5% 4 6% 7% 31%	2800
July	1st to 10th	Day	13% 7% 3 8% 6% 6% 5% 5% 7% 9% 33%	6360
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 5% 7% 9% 40%	6360
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 10% 45%	6926
August	1st to 10th	Day	13% 6% 3 8% 5% 5% 5% 4 6% 10% 33%	4563
	11th to 20th	Day	14% 6% 3 7% 5% 4 5% 3 6% 9% 38%	4132
	21st to end	Day	16% 5% 3 7% 5% 4 5% 4 6% 8% 39%	4312
September	1st to 10th	Day	10% 6% 2 6% 4 4 5% 5% 6% 8% 43%	2400
	11th to 20th	Day	14% 6% 1 5% 3 4 3 3 5% 7% 49%	2300
	21st to end	Day	16% 6% 2 7% 4 4 4 4 6% 7% 40%	2200
October	1st to 10th	Day	18% 6% 2 7% 5% 4 5% 3 5% 7% 35%	2088
	11th to 20th	Day	18% 8% 3 8% 6% 5% 6% 4 6% 7% 30%	1937
	21st to end	Day	26% 9% 3 7% 4 4 4 3 5% 5% 30%	1980
November	1st to 10th	Day	17% 12% 4 8% 5% 5% 4 4 6% 6% 31%	1851
	11th to 20th	Day	17% 13% 3 8% 5% 6% 4 4 4 7% 29%	1827
	21st to end	Day	24% 12% 5% 8% 5% 5% 4 4 5% 6% 24%	1680
December	1st to 10th	Day	19% 20% 6% 12% 5% 4 4 3 4 4 18%	2680
	11th to 20th	Day	20% 14% 4 9% 5% 4 4 4 5% 5% 25%	3066
	21st to end	Day	23% 13% 5% 10% 6% 6% 5% 5% 6% 4 18%	4048
January	1st to 10th	Night	14% 19% 7% 14% 6% 4 4 3 3 4 21%	8234
	11th to 20th	Night	12% 17% 7% 17% 7% 6% 5% 4 4 5% 16%	8235
	21st to end	Night	11% 14% 5% 12% 9% 6% 5% 4 5% 5% 24%	9057
February	1st to 10th	Night	14% 16% 6% 12% 8% 5% 4 4 4 6% 22%	2798
	11th to 20th	Night	14% 13% 6% 11% 6% 5% 5% 3 4 4 29%	2535
	21st to end	Night	15% 15% 4 9% 6% 5% 3 4 5% 4 31%	2076
March	1st to 10th	Night	21% 12% 4 8% 5% 4 4 3 4 4 30%	5484
	11th to 20th	Night	15% 15% 4 7% 5% 5% 4 4 5% 7% 30%	5387
	21st to end	Night	17% 12% 4 10% 5% 5% 4 3 4 4 31%	5072
April	1st to 10th	Night	24% 11% 3 7% 4 4 4 3 4 6% 30%	2100
	11th to 20th	Night	22% 9% 3 8% 5% 4 4 3 4 6% 33%	2075
	21st to end	Night	21% 9% 3 6% 4 4 4 3 4 6% 35%	1909
May	1st to 10th	Night	24% 11% 3 9% 5% 4 4 3 5% 6% 24%	3862
	11th to 20th	Night	23% 9% 3 8% 5% 5% 4 3 4 6% 30%	3623
	21st to end	Night	18% 9% 3 9% 5% 5% 5% 3 5% 7% 31%	3926
June	1st to 10th	Night	21% 8% 3 7% 5% 4 5% 4 5% 7% 32%	1600
	11th to 20th	Night	16% 6% 3 6% 5% 4 5% 4 6% 7% 38%	1600
	21st to end	Night	17% 8% 3 8% 5% 4 6% 3 6% 8% 33%	1600
July	1st to 10th	Night	13% 7% 3 8% 6% 5% 5% 5% 7% 9% 33%	3600
	11th to 20th	Night	14% 7% 2 6% 4 5% 5% 4 7% 7% 40%	3600
	21st to end	Night	9% 5% 3 7% 5% 4 5% 4 6% 8% 43%	3926
August	1st to 10th	Night	17% 8% 3 7% 5% 4 5% 4 5% 6% 36%	2586
	11th to 20th	Night	15% 7% 2 8% 5% 5% 4 4 6% 6% 37%	2880
	21st to end	Night	17% 6% 2 7% 5% 4 5% 4 5% 7% 38%	3586
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 5% 8% 44%	2000
	11th to 20th	Night	14% 6% 1 5% 4 3 3 3 5% 6% 50%	2100
	21st to end	Night	16% 7% 2 6% 4 4 3 3 5% 8% 42%	2200
October	1st to 10th	Night	18% 6% 3 6% 4 4 4 3 4 7% 41%	2310
	11th to 20th	Night	20% 8% 3 8% 5% 4 5% 3 5% 5% 34%	2462
	21st to end	Night	23% 9% 3 8% 5% 5% 5% 3 4 5% 30%	2860
November	1st to 10th	Night	20% 10% 3 7% 5% 4 4 4 5% 5% 32%	2667
	11th to 20th	Night	20% 11% 3 8% 5% 4 4 4 5% 5% 32%	2790
	21st to end	Night	23% 13% 4 9% 5% 4 4 3 4 5% 26%	2940
December	1st to 10th	Night	19% 18% 6% 13% 7% 5% 4 3 4 4 17%	4720
	11th to 20th	Night	23% 14% 4 10% 5% 4 4 3 4 6% 24%	5348
	21st to end	Night	23% 16% 5% 9% 4 3 4 4 5% 6% 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	66% 4 10% 16% 3	4662
	11th to 20th	Day	64% 4 8% 13% 10% 1	4680
	21st to end	Day	61% 5% 9% 14% 11%	5124
February	1st to 10th	Day	61% 4 8% 18% 7% 2	1821
	11th to 20th	Day	59% 5% 11% 16% 9% 1	1979
	21st to end	Day	60% 3 9% 16% 10% 1	1730
March	1st to 10th	Day	61% 5% 7% 14% 10% 3	4579
	11th to 20th	Day	52% 5% 17% 14% 10% 2	4789
	21st to end	Day	55% 3 8% 17% 16% 1	6102
April	1st to 10th	Day	57% 4 8% 18% 11% 2	2520
	11th to 20th	Day	50% 4 8% 22% 14% 1	2494
	21st to end	Day	53% 5% 9% 19% 12% 3	2709
May	1st to 10th	Day	60% 6% 9% 18% 7% 1	6353
	11th to 20th	Day	51% 7% 15% 17% 9% 2	6406
	21st to end	Day	50% 6% 11% 20% 11% 1	6949
June	1st to 10th	Day	51% 6% 10% 19% 12% 2	2800
	11th to 20th	Day	41% 6% 12% 25% 13% 2	2800
	21st to end	Day	51% 7% 11% 21% 10% 1	2800
July	1st to 10th	Day	46% 7% 13% 26% 8%	6290
	11th to 20th	Day	38% 7% 14% 30% 10%	6285
	21st to end	Day	35% 6% 14% 37% 8%	6728
August	1st to 10th	Day	45% 7% 17% 23% 8%	4549
	11th to 20th	Day	43% 6% 18% 26% 7%	4173
	21st to end	Day	42% 6% 15% 22% 14%	4312
September	1st to 10th	Day	37% 7% 15% 30% 12%	2400
	11th to 20th	Day	35% 4 12% 34% 14% 1	2300
	21st to end	Day	43% 6% 13% 26% 12% 1	2200
October	1st to 10th	Day	44% 5% 15% 29% 8%	3400
	11th to 20th	Day	44% 6% 17% 26% 7%	3127
	21st to end	Day	46% 4 19% 22% 8%	3180
November	1st to 10th	Day	52% 6% 12% 20% 9% 1	1851
	11th to 20th	Day	54% 5% 12% 17% 11%	1827
	21st to end	Day	62% 7% 12% 14% 6%	1680
December	1st to 10th	Day	70% 4 8% 15% 3	2680
	11th to 20th	Day	60% 5% 9% 17% 9%	3066
	21st to end	Day	67% 6% 11% 10% 6%	4048
January	1st to 10th	Night	67% 4 10% 13% 5% 1	8234
	11th to 20th	Night	69% 5% 8% 11% 6%	8280
	21st to end	Night	62% 4 7% 14% 13%	9057
February	1st to 10th	Night	63% 4 9% 15% 7% 1	2798
	11th to 20th	Night	58% 4 9% 18% 9%	2537
	21st to end	Night	56% 5% 9% 18% 12% 1	2076
March	1st to 10th	Night	58% 4 7% 15% 11% 5%	5494
	11th to 20th	Night	54% 4 13% 15% 13% 1	5388
	21st to end	Night	56% 3 6% 21% 12% 2	5072
April	1st to 10th	Night	56% 4 8% 18% 13% 2	2100
	11th to 20th	Night	53% 4 8% 20% 14% 2	2075
	21st to end	Night	51% 4 7% 19% 15% 3	1909
May	1st to 10th	Night	60% 6% 9% 17% 6% 2	3868
	11th to 20th	Night	54% 6% 10% 19% 10% 2	3624
	21st to end	Night	52% 6% 9% 18% 14% 1	3927
June	1st to 10th	Night	51% 6% 8% 22% 13% 1	1600
	11th to 20th	Night	44% 6% 11% 21% 15% 3	1600
	21st to end	Night	49% 7% 10% 19% 14% 1	1600
July	1st to 10th	Night	45% 6% 18% 21% 9%	3560
	11th to 20th	Night	41% 6% 15% 27% 10%	3552
	21st to end	Night	38% 6% 16% 28% 11%	3809
August	1st to 10th	Night	48% 6% 12% 26% 8%	2576
	11th to 20th	Night	45% 7% 17% 22% 8%	2905
	21st to end	Night	45% 6% 12% 23% 14% 1	3586
September	1st to 10th	Night	38% 7% 12% 27% 16% 1	2000
	11th to 20th	Night	36% 4 14% 32% 14% 1	2100
	21st to end	Night	42% 7% 10% 25% 16% 1	2200
October	1st to 10th	Night	44% 5% 13% 27% 11% 1	3778
	11th to 20th	Night	46% 5% 10% 30% 9%	4011
	21st to end	Night	50% 4 14% 19% 12% 2	4610
November	1st to 10th	Night	54% 4 12% 22% 8% 1	2667
	11th to 20th	Night	54% 5% 11% 18% 10% 2	2790
	21st to end	Night	61% 5% 11% 17% 6%	2940
December	1st to 10th	Night	71% 5% 10% 11% 3	4720
	11th to 20th	Night	62% 5% 8% 14% 11%	5348
	21st to end	Night	65% 4 8% 14% 9%	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	29% 12% 33% 18% 9%	220
	11th to 20th	Day	28% 17% 32% 18% 5%	220
	21st to end	Day	20% 15% 34% 19% 10% 1	242
February	1st to 10th	Day	28% 17% 34% 18% 4	294
	11th to 20th	Day	22% 15% 33% 25% 3	458
	21st to end	Day	27% 14% 32% 24% 3	446
March	1st to 10th	Day	23% 15% 33% 22% 7%	540
	11th to 20th	Day	24% 15% 33% 20% 6% 1	540
	21st to end	Day	27% 14% 32% 19% 8% 1	594
April	1st to 10th	Day	30% 16% 28% 17% 6% 2	540
	11th to 20th	Day	30% 19% 24% 18% 8% 2	532
	21st to end	Day	27% 15% 31% 17% 9% 1	540
May	1st to 10th	Day	25% 12% 31% 20% 10% 2	543
	11th to 20th	Day	18% 10% 28% 28% 13% 3	551
	21st to end	Day	20% 14% 30% 24% 10% 2	573
June	1st to 10th	Day	23% 11% 27% 28% 9% 2	530
	11th to 20th	Day	17% 10% 27% 30% 15% 2	530
	21st to end	Day	24% 9% 28% 24% 12% 3	530
July	1st to 10th	Day	13% 8% 25% 31% 17% 5%	525
	11th to 20th	Day	13% 7% 30% 31% 14% 4	524
	21st to end	Day	14% 7% 28% 32% 18% 2	576
August	1st to 10th	Day	13% 5% 23% 32% 21% 6%	526
	11th to 20th	Day	12% 6% 21% 33% 21% 8%	519
	21st to end	Day	15% 8% 26% 23% 18% 9%	583
September	1st to 10th	Day	13% 7% 29% 29% 15% 8%	530
	11th to 20th	Day	15% 7% 19% 28% 20% 12%	530
	21st to end	Day	17% 9% 27% 22% 18% 6%	530
October	1st to 10th	Day	20% 11% 27% 23% 14% 4	530
	11th to 20th	Day	22% 12% 32% 21% 12% 1	494
	21st to end	Day	31% 13% 26% 23% 7%	462
November	1st to 10th	Day	28% 15% 28% 20% 8%	425
	11th to 20th	Day	26% 14% 31% 21% 7% 1	367
	21st to end	Day	35% 13% 28% 17% 5% 1	220
December	1st to 10th	Day	32% 10% 25% 21% 8% 3	220
	11th to 20th	Day	26% 20% 36% 14% 3	220
	21st to end	Day	28% 21% 27% 19% 5% 2	242
January	1st to 10th	Night	27% 12% 31% 25% 5%	840
	11th to 20th	Night	26% 12% 32% 23% 6%	840
	21st to end	Night	21% 11% 33% 28% 6% 1	924
February	1st to 10th	Night	21% 11% 35% 27% 5% 1	840
	11th to 20th	Night	21% 11% 39% 24% 5% 1	823
	21st to end	Night	23% 11% 32% 29% 4	692
March	1st to 10th	Night	25% 11% 32% 26% 6%	840
	11th to 20th	Night	27% 13% 30% 24% 7%	840
	21st to end	Night	24% 10% 31% 27% 7% 1	924
April	1st to 10th	Night	30% 12% 26% 26% 5%	840
	11th to 20th	Night	27% 13% 29% 24% 6% 1	831
	21st to end	Night	27% 11% 30% 24% 7% 1	649
May	1st to 10th	Night	26% 8% 31% 26% 7% 1	504
	11th to 20th	Night	23% 9% 30% 29% 9% 1	406
	21st to end	Night	19% 7% 35% 30% 9%	433
June	1st to 10th	Night	24% 6% 29% 32% 10% 1	400
	11th to 20th	Night	19% 4 30% 36% 12%	400
	21st to end	Night	19% 6% 27% 34% 13% 1	400
July	1st to 10th	Night	12% 5% 28% 39% 14% 1	390
	11th to 20th	Night	13% 1 24% 46% 13% 2	388
	21st to end	Night	13% 3 24% 43% 16%	438
August	1st to 10th	Night	14% 5% 18% 43% 19% 2	398
	11th to 20th	Night	14% 3 20% 37% 24% 2	584
	21st to end	Night	16% 5% 19% 38% 20% 2	880
September	1st to 10th	Night	16% 4 24% 39% 16% 1	800
	11th to 20th	Night	17% 4 20% 35% 21% 3	800
	21st to end	Night	20% 5% 26% 32% 15% 3	800
October	1st to 10th	Night	21% 7% 28% 30% 13% 1	800
	11th to 20th	Night	25% 9% 27% 29% 9%	800
	21st to end	Night	27% 10% 31% 26% 6%	880
November	1st to 10th	Night	26% 11% 32% 23% 7%	820
	11th to 20th	Night	27% 10% 32% 23% 8% 1	840
	21st to end	Night	28% 14% 31% 19% 7%	840
December	1st to 10th	Night	31% 11% 30% 23% 6%	840
	11th to 20th	Night	29% 13% 33% 18% 5% 1	840
	21st to end	Night	34% 12% 29% 18% 6%	924

Page generated at 2026-05-14 01:58:55. Version ac07

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