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 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	17% 10% 3 8% 5% 5% 5% 4 5% 7% 32%	105257
	Night	18% 11% 4 9% 5% 4 4 3 5% 6% 30%	104130
Transparency	Day	50% 6% 13% 21% 9% 1	108719
	Night	54% 5% 11% 19% 10% 1	108757
Seeing	Day	22% 11% 28% 24% 12% 3	14760
	Night	24% 9% 29% 28% 9% 1	23826

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% 17% 6% 13% 5% 5% 4 3 3 4 23%	2597
	11th to 20th	Day	15% 14% 5% 12% 6% 5% 4 3 5% 7% 26%	2600
	21st to end	Day	15% 16% 4 10% 6% 5% 5% 4 5% 6% 24%	2780
February	1st to 10th	Day	17% 17% 4 10% 5% 5% 4 4 5% 6% 25%	1647
	11th to 20th	Day	14% 13% 5% 12% 7% 5% 4 4 5% 5% 26%	1777
	21st to end	Day	18% 15% 4 9% 6% 4 3 4 4 5% 28%	1570
March	1st to 10th	Day	19% 12% 4 11% 7% 5% 5% 3 4 5% 26%	3116
	11th to 20th	Day	15% 16% 5% 11% 5% 5% 4 3 5% 5% 26%	3270
	21st to end	Day	15% 10% 4 9% 5% 4 4 3 4 5% 36%	4166
April	1st to 10th	Day	22% 12% 4 8% 5% 4 4 3 4 5% 30%	2280
	11th to 20th	Day	21% 9% 2 7% 4 4 4 3 5% 6% 36%	2254
	21st to end	Day	22% 9% 3 7% 5% 4 4 3 4 6% 32%	2451
May	1st to 10th	Day	20% 10% 3 8% 5% 4 4 4 6% 7% 30%	4327
	11th to 20th	Day	17% 9% 3 8% 5% 5% 5% 4 6% 8% 30%	4398
	21st to end	Day	15% 7% 2 7% 5% 4 6% 5% 7% 9% 35%	4837
June	1st to 10th	Day	21% 8% 3 7% 5% 5% 5% 4 6% 7% 30%	2660
	11th to 20th	Day	15% 6% 2 6% 4 5% 4 4 6% 9% 39%	2660
	21st to end	Day	21% 9% 2 6% 5% 4 5% 4 6% 7% 30%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 9% 36%	4440
	11th to 20th	Day	13% 6% 2 6% 5% 5% 6% 5% 7% 9% 36%	4440
	21st to end	Day	12% 6% 2 5% 5% 4 5% 4 6% 8% 44%	4814
August	1st to 10th	Day	14% 6% 3 8% 5% 5% 5% 4 6% 10% 32%	4423
	11th to 20th	Day	14% 6% 3 7% 5% 4 5% 3 6% 9% 37%	4003
	21st to end	Day	16% 5% 3 7% 5% 4 5% 4 6% 8% 39%	4180
September	1st to 10th	Day	10% 6% 2 6% 4 4 5% 5% 6% 8% 42%	2280
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 5% 7% 48%	2185
	21st to end	Day	16% 6% 2 7% 4 4 4 4 6% 7% 40%	2090
October	1st to 10th	Day	19% 7% 3 7% 5% 5% 5% 4 5% 7% 33%	1984
	11th to 20th	Day	18% 9% 3 8% 6% 6% 6% 4 6% 6% 29%	1840
	21st to end	Day	25% 9% 3 7% 4 4 4 3 5% 5% 31%	1881
November	1st to 10th	Day	17% 11% 4 7% 5% 5% 4 4 6% 6% 32%	1761
	11th to 20th	Day	17% 12% 3 8% 5% 5% 4 4 4 7% 30%	1740
	21st to end	Day	24% 11% 5% 8% 5% 5% 4 4 5% 6% 24%	1600
December	1st to 10th	Day	20% 20% 6% 12% 5% 4 4 3 4 4 18%	2600
	11th to 20th	Day	20% 15% 4 9% 5% 4 4 3 5% 5% 25%	2986
	21st to end	Day	23% 13% 5% 10% 6% 6% 5% 5% 6% 4 18%	3960
January	1st to 10th	Night	17% 17% 6% 11% 6% 4 4 3 4 5% 23%	4569
	11th to 20th	Night	12% 14% 6% 13% 7% 6% 6% 4 5% 6% 21%	4580
	21st to end	Night	17% 18% 5% 10% 6% 4 4 3 4 4 24%	4899
February	1st to 10th	Night	15% 16% 6% 12% 8% 5% 4 3 4 6% 21%	2532
	11th to 20th	Night	14% 13% 5% 10% 6% 5% 6% 3 5% 4 29%	2288
	21st to end	Night	16% 15% 4 9% 5% 5% 3 4 5% 4 30%	1884
March	1st to 10th	Night	21% 10% 3 8% 5% 4 4 3 4 5% 33%	3724
	11th to 20th	Night	18% 19% 5% 8% 4 4 3 3 3 4 28%	3686
	21st to end	Night	14% 11% 4 10% 5% 5% 4 3 4 4 37%	3466
April	1st to 10th	Night	24% 10% 3 7% 4 4 4 3 4 6% 30%	1900
	11th to 20th	Night	22% 9% 3 7% 4 4 5% 3 4 6% 33%	1875
	21st to end	Night	21% 10% 3 6% 4 4 4 3 4 6% 34%	1727
May	1st to 10th	Night	21% 10% 3 7% 5% 5% 4 4 5% 7% 30%	2642
	11th to 20th	Night	22% 8% 3 7% 4 4 4 3 5% 6% 33%	2495
	21st to end	Night	15% 7% 3 7% 4 4 4 4 5% 8% 37%	2738
June	1st to 10th	Night	21% 8% 3 7% 5% 4 5% 4 6% 7% 32%	1520
	11th to 20th	Night	16% 6% 3 6% 5% 4 5% 4 6% 7% 38%	1520
	21st to end	Night	17% 8% 3 8% 5% 4 6% 3 5% 8% 32%	1520
July	1st to 10th	Night	14% 7% 3 8% 6% 5% 5% 4 7% 8% 34%	2520
	11th to 20th	Night	13% 7% 2 6% 5% 5% 5% 4 7% 8% 40%	2520
	21st to end	Night	11% 5% 3 7% 6% 4 5% 4 6% 7% 42%	2739
August	1st to 10th	Night	17% 8% 3 8% 5% 5% 5% 4 5% 6% 35%	2506
	11th to 20th	Night	16% 7% 2 8% 4 5% 5% 4 6% 6% 36%	2791
	21st to end	Night	17% 6% 2 7% 5% 4 5% 4 5% 7% 38%	3476
September	1st to 10th	Night	13% 6% 2 6% 5% 4 4 4 5% 7% 43%	1900
	11th to 20th	Night	15% 6% 2 5% 4 3 3 3 5% 6% 49%	1995
	21st to end	Night	16% 7% 2 6% 4 4 3 3 5% 8% 42%	2090
October	1st to 10th	Night	18% 6% 3 6% 4 4 4 3 4 7% 39%	2194
	11th to 20th	Night	21% 8% 3 8% 5% 4 5% 3 5% 5% 33%	2339
	21st to end	Night	23% 9% 4 8% 5% 5% 5% 3 4 4 30%	2717
November	1st to 10th	Night	20% 10% 3 7% 5% 5% 4 4 5% 6% 32%	2537
	11th to 20th	Night	20% 10% 3 8% 5% 4 4 4 5% 5% 32%	2657
	21st to end	Night	23% 13% 4 9% 5% 4 4 3 4 5% 26%	2800
December	1st to 10th	Night	19% 18% 6% 13% 7% 5% 4 3 4 4 17%	4580
	11th to 20th	Night	23% 14% 4 10% 5% 4 4 3 4 6% 24%	5208
	21st to end	Night	24% 16% 4 9% 4 3 4 4 5% 6% 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	65% 6% 12% 14% 3	2598
	11th to 20th	Day	58% 5% 13% 16% 7%	2600
	21st to end	Day	60% 6% 13% 15% 5%	2780
February	1st to 10th	Day	62% 4 9% 18% 6% 2	1647
	11th to 20th	Day	59% 5% 11% 15% 9% 1	1786
	21st to end	Day	60% 3 10% 16% 10% 2	1570
March	1st to 10th	Day	59% 6% 8% 18% 7% 1	3119
	11th to 20th	Day	58% 6% 12% 11% 10% 3	3270
	21st to end	Day	48% 4 10% 20% 16% 2	4166
April	1st to 10th	Day	57% 4 8% 18% 11% 2	2280
	11th to 20th	Day	49% 5% 8% 22% 14% 2	2254
	21st to end	Day	53% 5% 9% 18% 12% 3	2451
May	1st to 10th	Day	51% 7% 10% 22% 9% 1	4341
	11th to 20th	Day	49% 8% 16% 17% 9% 1	4402
	21st to end	Day	43% 7% 12% 23% 13% 2	4837
June	1st to 10th	Day	51% 7% 10% 19% 11% 2	2660
	11th to 20th	Day	42% 6% 12% 24% 13% 2	2660
	21st to end	Day	51% 7% 11% 20% 10% 1	2660
July	1st to 10th	Day	42% 7% 13% 28% 9%	4370
	11th to 20th	Day	41% 7% 16% 29% 7%	4365
	21st to end	Day	37% 7% 14% 33% 9%	4661
August	1st to 10th	Day	46% 7% 16% 23% 7%	4409
	11th to 20th	Day	43% 6% 19% 25% 7%	4044
	21st to end	Day	42% 6% 15% 21% 15%	4180
September	1st to 10th	Day	38% 7% 14% 28% 12%	2280
	11th to 20th	Day	36% 4 12% 33% 14% 1	2185
	21st to end	Day	43% 7% 13% 26% 11% 1	2090
October	1st to 10th	Day	45% 5% 15% 28% 7%	3296
	11th to 20th	Day	44% 6% 17% 25% 7%	3030
	21st to end	Day	46% 4 19% 22% 9%	3081
November	1st to 10th	Day	50% 6% 13% 20% 9% 1	1761
	11th to 20th	Day	53% 5% 12% 17% 12%	1740
	21st to end	Day	61% 7% 12% 14% 6%	1600
December	1st to 10th	Day	70% 4 8% 15% 3	2600
	11th to 20th	Day	60% 5% 8% 17% 9%	2986
	21st to end	Day	67% 6% 11% 10% 6%	3960
January	1st to 10th	Night	63% 6% 14% 12% 5%	4569
	11th to 20th	Night	62% 7% 12% 14% 5% 1	4580
	21st to end	Night	64% 5% 10% 13% 7%	4899
February	1st to 10th	Night	65% 4 9% 15% 6% 1	2532
	11th to 20th	Night	58% 4 9% 18% 9% 1	2290
	21st to end	Night	56% 5% 9% 16% 13% 2	1884
March	1st to 10th	Night	54% 5% 10% 19% 9% 4	3734
	11th to 20th	Night	61% 4 9% 12% 13% 2	3687
	21st to end	Night	50% 4 7% 23% 14% 3	3466
April	1st to 10th	Night	55% 4 9% 17% 13% 2	1900
	11th to 20th	Night	52% 4 8% 20% 14% 2	1875
	21st to end	Night	52% 4 8% 19% 14% 3	1727
May	1st to 10th	Night	53% 8% 10% 19% 8% 3	2648
	11th to 20th	Night	49% 7% 11% 19% 11% 2	2496
	21st to end	Night	45% 6% 9% 20% 17% 2	2739
June	1st to 10th	Night	51% 6% 8% 22% 12% 1	1520
	11th to 20th	Night	44% 7% 11% 21% 14% 3	1520
	21st to end	Night	50% 7% 9% 19% 14% 1	1520
July	1st to 10th	Night	47% 6% 14% 20% 12% 1	2480
	11th to 20th	Night	40% 7% 16% 27% 9%	2472
	21st to end	Night	40% 7% 17% 24% 12%	2651
August	1st to 10th	Night	49% 6% 11% 25% 8%	2496
	11th to 20th	Night	46% 7% 17% 22% 8%	2816
	21st to end	Night	45% 6% 11% 22% 14% 1	3476
September	1st to 10th	Night	39% 7% 12% 26% 16% 1	1900
	11th to 20th	Night	36% 4 14% 31% 14% 1	1995
	21st to end	Night	42% 7% 10% 26% 15% 1	2090
October	1st to 10th	Night	45% 5% 13% 27% 10%	3662
	11th to 20th	Night	47% 5% 10% 30% 8%	3888
	21st to end	Night	50% 4 14% 18% 12% 2	4467
November	1st to 10th	Night	53% 4 12% 21% 8% 1	2537
	11th to 20th	Night	53% 5% 11% 18% 11% 2	2657
	21st to end	Night	61% 5% 11% 17% 6%	2800
December	1st to 10th	Night	71% 5% 10% 10% 3	4580
	11th to 20th	Night	62% 5% 8% 14% 11%	5208
	21st to end	Night	65% 4 8% 14% 9%	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	30% 12% 32% 17% 9%	200
	11th to 20th	Day	27% 16% 33% 20% 6%	200
	21st to end	Day	21% 12% 34% 22% 11% 1	200
February	1st to 10th	Day	32% 17% 33% 16% 3	240
	11th to 20th	Day	22% 15% 35% 24% 3 1	385
	21st to end	Day	28% 12% 30% 26% 4	382
March	1st to 10th	Day	23% 12% 31% 25% 8%	460
	11th to 20th	Day	22% 15% 34% 21% 8% 1	460
	21st to end	Day	26% 12% 32% 20% 9% 1	506
April	1st to 10th	Day	30% 13% 28% 20% 7% 2	460
	11th to 20th	Day	28% 19% 24% 18% 8% 3	452
	21st to end	Day	28% 13% 30% 17% 10% 2	460
May	1st to 10th	Day	24% 12% 31% 20% 11% 2	463
	11th to 20th	Day	17% 10% 29% 27% 14% 3	487
	21st to end	Day	19% 14% 30% 24% 10% 2	529
June	1st to 10th	Day	23% 10% 27% 28% 9% 2	490
	11th to 20th	Day	16% 10% 26% 31% 15% 2	490
	21st to end	Day	24% 9% 26% 24% 13% 3	490
July	1st to 10th	Day	13% 8% 25% 32% 18% 5%	485
	11th to 20th	Day	14% 7% 29% 32% 14% 4	484
	21st to end	Day	14% 6% 27% 32% 18% 2	532
August	1st to 10th	Day	14% 6% 23% 31% 21% 5%	486
	11th to 20th	Day	12% 6% 21% 32% 21% 8%	479
	21st to end	Day	15% 8% 25% 24% 18% 10%	539
September	1st to 10th	Day	13% 7% 29% 29% 15% 7%	490
	11th to 20th	Day	16% 7% 19% 27% 18% 12%	490
	21st to end	Day	17% 8% 27% 23% 19% 6%	490
October	1st to 10th	Day	22% 12% 26% 23% 14% 3	490
	11th to 20th	Day	23% 12% 31% 21% 12% 1	457
	21st to end	Day	31% 13% 26% 23% 7%	429
November	1st to 10th	Day	28% 13% 28% 22% 9%	395
	11th to 20th	Day	25% 14% 31% 21% 7% 1	340
	21st to end	Day	35% 12% 29% 18% 6% 1	200
December	1st to 10th	Day	34% 10% 23% 23% 8% 3	200
	11th to 20th	Day	27% 21% 34% 15% 4	200
	21st to end	Day	29% 20% 25% 19% 5% 2	220
January	1st to 10th	Night	28% 12% 31% 25% 5%	800
	11th to 20th	Night	25% 12% 32% 24% 7%	800
	21st to end	Night	22% 10% 33% 28% 6% 1	841
February	1st to 10th	Night	23% 10% 36% 26% 4 1	760
	11th to 20th	Night	20% 11% 38% 25% 4 1	743
	21st to end	Night	24% 11% 32% 29% 4	628
March	1st to 10th	Night	25% 10% 31% 28% 6%	760
	11th to 20th	Night	28% 11% 30% 24% 7%	760
	21st to end	Night	23% 8% 32% 29% 7% 1	836
April	1st to 10th	Night	30% 11% 26% 27% 6%	760
	11th to 20th	Night	26% 14% 28% 24% 7% 1	751
	21st to end	Night	27% 11% 29% 25% 7% 1	587
May	1st to 10th	Night	26% 8% 31% 26% 7% 2	456
	11th to 20th	Night	23% 9% 29% 29% 9% 1	374
	21st to end	Night	18% 7% 36% 30% 8%	411
June	1st to 10th	Night	24% 5% 28% 32% 10% 1	380
	11th to 20th	Night	19% 3 30% 35% 12%	380
	21st to end	Night	20% 5% 27% 35% 13% 1	380
July	1st to 10th	Night	13% 5% 28% 39% 15% 1	370
	11th to 20th	Night	13% 1 25% 46% 14% 2	368
	21st to end	Night	14% 3 24% 43% 17%	416
August	1st to 10th	Night	14% 5% 17% 43% 19% 2	378
	11th to 20th	Night	14% 3 20% 37% 23% 2	555
	21st to end	Night	16% 5% 20% 37% 20% 2	836
September	1st to 10th	Night	16% 4 24% 39% 16% 1	760
	11th to 20th	Night	17% 4 20% 35% 21% 3	760
	21st to end	Night	20% 5% 26% 32% 15% 3	760
October	1st to 10th	Night	21% 8% 28% 29% 13% 1	760
	11th to 20th	Night	27% 9% 26% 28% 9%	760
	21st to end	Night	28% 10% 31% 25% 6%	836
November	1st to 10th	Night	25% 12% 32% 23% 8% 1	780
	11th to 20th	Night	27% 10% 32% 22% 8% 1	800
	21st to end	Night	29% 14% 30% 20% 8%	800
December	1st to 10th	Night	31% 11% 29% 23% 6%	800
	11th to 20th	Night	29% 12% 33% 19% 6% 1	800
	21st to end	Night	34% 12% 29% 19% 6%	880

Page generated at 2025-01-19 03:06:45. Version ac07

Copyright © 2025 Attilla Danko.