Saint-Sauveur
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint-Sauveur clear sky chart from 2005-11-06 to 2024-12-06.

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	16% 10% 3 8% 5% 5% 5% 4 6% 6% 32%	101824
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 33%	97901
Transparency	Day	50% 7% 13% 20% 10% 1	105274
	Night	50% 6% 13% 20% 10% 1	102540
Seeing	Day	23% 17% 31% 19% 7% 2	14595
	Night	22% 14% 31% 24% 8% 1	23603

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	14% 17% 6% 14% 7% 4 4 3 4 4 23%	2517
	11th to 20th	Day	12% 15% 7% 15% 9% 4 3 3 4 5% 23%	2520
	21st to end	Day	10% 16% 7% 12% 6% 5% 6% 5% 6% 5% 22%	2772
February	1st to 10th	Day	12% 19% 3 12% 7% 5% 5% 3 4 6% 25%	1677
	11th to 20th	Day	11% 18% 5% 11% 6% 5% 4 3 5% 5% 27%	1734
	21st to end	Day	15% 16% 5% 10% 7% 5% 4 3 4 5% 26%	1570
March	1st to 10th	Day	17% 16% 4 11% 5% 5% 4 3 5% 4 25%	3116
	11th to 20th	Day	11% 18% 5% 13% 5% 4 4 3 4 5% 27%	3315
	21st to end	Day	13% 11% 2 8% 5% 4 4 3 5% 6% 38%	4134
April	1st to 10th	Day	20% 13% 3 9% 5% 4 3 3 4 5% 31%	2280
	11th to 20th	Day	20% 9% 3 7% 4 3 4 4 5% 6% 34%	2254
	21st to end	Day	21% 11% 3 8% 5% 4 4 3 5% 5% 31%	2422
May	1st to 10th	Day	20% 10% 3 9% 5% 5% 5% 3 5% 6% 29%	4426
	11th to 20th	Day	18% 9% 3 8% 5% 5% 4 4 6% 8% 31%	4398
	21st to end	Day	17% 7% 2 7% 5% 5% 6% 5% 5% 7% 35%	4837
June	1st to 10th	Day	21% 7% 3 7% 5% 5% 5% 4 6% 7% 28%	2660
	11th to 20th	Day	15% 7% 3 7% 6% 5% 5% 4 7% 8% 33%	2660
	21st to end	Day	22% 9% 2 9% 5% 5% 5% 5% 6% 6% 27%	2660
July	1st to 10th	Day	12% 6% 3 8% 6% 6% 6% 5% 6% 9% 33%	4440
	11th to 20th	Day	14% 5% 2 6% 4 5% 6% 6% 8% 8% 34%	4440
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 6% 7% 44%	4814
August	1st to 10th	Day	14% 6% 3 7% 5% 6% 6% 6% 7% 8% 31%	4423
	11th to 20th	Day	14% 6% 3 7% 5% 4 5% 5% 7% 9% 35%	4022
	21st to end	Day	15% 5% 2 7% 5% 4 6% 3 6% 7% 38%	4180
September	1st to 10th	Day	15% 6% 2 6% 4 5% 4 4 7% 8% 41%	2280
	11th to 20th	Day	14% 6% 2 7% 4 3 4 3 6% 6% 47%	2218
	21st to end	Day	18% 8% 3 5% 4 4 4 3 6% 6% 40%	2090
October	1st to 10th	Day	21% 7% 2 6% 5% 4 5% 4 5% 6% 35%	1933
	11th to 20th	Day	21% 10% 3 8% 5% 5% 4 4 5% 6% 28%	1872
	21st to end	Day	24% 11% 3 7% 5% 4 4 3 5% 6% 28%	1881
November	1st to 10th	Day	14% 10% 3 8% 6% 4 5% 4 6% 6% 34%	1761
	11th to 20th	Day	17% 12% 4 9% 5% 5% 5% 3 6% 5% 29%	1680
	21st to end	Day	20% 14% 4 8% 5% 5% 5% 4 5% 6% 23%	1600
December	1st to 10th	Day	20% 18% 5% 11% 5% 5% 4 3 3 5% 20%	1560
	11th to 20th	Day	19% 14% 6% 9% 6% 4 4 3 5% 5% 26%	1906
	21st to end	Day	23% 18% 6% 10% 5% 4 3 3 3 4 22%	2772
January	1st to 10th	Night	13% 16% 6% 11% 6% 5% 4 4 4 6% 24%	4429
	11th to 20th	Night	9% 13% 6% 14% 8% 5% 4 3 5% 7% 25%	4440
	21st to end	Night	11% 15% 7% 12% 6% 6% 5% 4 5% 6% 24%	4884
February	1st to 10th	Night	11% 14% 5% 11% 7% 5% 5% 4 6% 5% 27%	2499
	11th to 20th	Night	10% 13% 5% 11% 6% 5% 5% 4 6% 6% 30%	2331
	21st to end	Night	13% 13% 5% 10% 6% 4 4 3 5% 6% 31%	1884
March	1st to 10th	Night	18% 14% 5% 7% 5% 4 4 3 4 5% 31%	3724
	11th to 20th	Night	12% 20% 5% 10% 5% 3 4 3 4 5% 28%	3639
	21st to end	Night	13% 9% 4 9% 6% 5% 4 3 4 5% 39%	3498
April	1st to 10th	Night	22% 10% 3 7% 5% 4 4 3 5% 6% 31%	1900
	11th to 20th	Night	18% 8% 2 7% 5% 4 4 4 5% 6% 37%	1875
	21st to end	Night	20% 8% 3 8% 5% 3 5% 3 4 6% 36%	1758
May	1st to 10th	Night	18% 10% 4 9% 6% 5% 5% 4 4 6% 31%	2528
	11th to 20th	Night	21% 8% 3 6% 3 3 3 3 5% 7% 37%	2495
	21st to end	Night	17% 8% 3 6% 6% 5% 5% 3 6% 7% 35%	2738
June	1st to 10th	Night	19% 8% 3 6% 4 5% 4 4 6% 9% 32%	1520
	11th to 20th	Night	18% 7% 2 5% 5% 4 4 4 5% 7% 38%	1520
	21st to end	Night	19% 8% 1 6% 5% 4 4 3 7% 6% 37%	1520
July	1st to 10th	Night	11% 6% 2 8% 6% 6% 5% 4 6% 7% 37%	2520
	11th to 20th	Night	14% 5% 2 5% 4 4 4 4 5% 8% 43%	2520
	21st to end	Night	11% 6% 2 5% 4 4 5% 4 6% 7% 46%	2739
August	1st to 10th	Night	12% 5% 3 7% 5% 5% 5% 4 6% 8% 40%	2506
	11th to 20th	Night	14% 7% 3 7% 4 4 4 3 6% 7% 43%	2773
	21st to end	Night	15% 6% 3 6% 4 4 4 3 5% 7% 43%	3476
September	1st to 10th	Night	10% 6% 2 6% 4 5% 5% 4 5% 7% 47%	1900
	11th to 20th	Night	13% 5% 2 6% 4 3 4 3 5% 8% 49%	1962
	21st to end	Night	17% 7% 2 5% 3 4 4 3 5% 6% 45%	2090
October	1st to 10th	Night	16% 8% 3 7% 4 5% 4 3 4 6% 40%	2245
	11th to 20th	Night	19% 8% 3 7% 4 3 5% 4 5% 7% 35%	2308
	21st to end	Night	21% 10% 3 7% 5% 4 4 4 5% 6% 31%	2717
November	1st to 10th	Night	16% 10% 4 8% 5% 5% 5% 4 6% 7% 31%	2537
	11th to 20th	Night	16% 10% 4 8% 5% 4 5% 5% 5% 6% 33%	2717
	21st to end	Night	18% 15% 3 9% 5% 4 4 4 5% 7% 27%	2800
December	1st to 10th	Night	17% 15% 6% 10% 7% 5% 5% 4 6% 7% 20%	2737
	11th to 20th	Night	19% 15% 4 9% 6% 5% 4 3 4 5% 26%	3288
	21st to end	Night	23% 19% 5% 9% 4 4 3 3 4 4 23%	4884

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	64% 8% 10% 13% 4 1	2518
	11th to 20th	Day	62% 7% 9% 15% 7% 1	2520
	21st to end	Day	62% 8% 11% 12% 7% 1	2772
February	1st to 10th	Day	60% 5% 8% 18% 7% 2	1677
	11th to 20th	Day	59% 5% 11% 15% 9% 1	1743
	21st to end	Day	61% 4 9% 15% 9% 3	1570
March	1st to 10th	Day	61% 6% 7% 16% 9% 1	3119
	11th to 20th	Day	58% 4 11% 13% 10% 3	3315
	21st to end	Day	46% 5% 7% 21% 18% 3	4134
April	1st to 10th	Day	56% 4 9% 17% 12% 3	2280
	11th to 20th	Day	50% 4 9% 22% 13% 2	2254
	21st to end	Day	55% 5% 8% 17% 12% 4	2422
May	1st to 10th	Day	54% 6% 8% 21% 9% 2	4440
	11th to 20th	Day	48% 10% 16% 15% 9% 2	4402
	21st to end	Day	46% 6% 11% 22% 14% 1	4837
June	1st to 10th	Day	53% 6% 10% 17% 11% 2	2660
	11th to 20th	Day	46% 7% 12% 19% 12% 3	2660
	21st to end	Day	56% 8% 10% 16% 9% 1	2660
July	1st to 10th	Day	44% 8% 15% 24% 9%	4370
	11th to 20th	Day	41% 9% 17% 26% 7%	4365
	21st to end	Day	37% 7% 15% 31% 10%	4661
August	1st to 10th	Day	46% 8% 17% 22% 7%	4409
	11th to 20th	Day	42% 8% 17% 26% 6%	4064
	21st to end	Day	42% 8% 15% 20% 13% 1	4180
September	1st to 10th	Day	40% 6% 14% 27% 13%	2280
	11th to 20th	Day	36% 6% 15% 29% 12% 1	2218
	21st to end	Day	43% 6% 14% 25% 12%	2090
October	1st to 10th	Day	43% 6% 16% 26% 8%	3206
	11th to 20th	Day	45% 7% 16% 24% 8%	3088
	21st to end	Day	45% 5% 23% 17% 9% 1	3081
November	1st to 10th	Day	49% 7% 14% 20% 9% 1	1761
	11th to 20th	Day	55% 4 14% 15% 10% 1	1680
	21st to end	Day	61% 6% 14% 14% 4 1	1600
December	1st to 10th	Day	68% 5% 11% 11% 5%	1560
	11th to 20th	Day	61% 4 13% 15% 6%	1906
	21st to end	Day	68% 5% 8% 13% 6%	2772
January	1st to 10th	Night	61% 7% 15% 12% 4	4429
	11th to 20th	Night	57% 7% 18% 13% 5% 1	4440
	21st to end	Night	61% 8% 11% 11% 7% 1	4884
February	1st to 10th	Night	58% 5% 10% 19% 7% 1	2499
	11th to 20th	Night	53% 6% 13% 19% 9% 1	2333
	21st to end	Night	56% 4 10% 17% 11% 2	1884
March	1st to 10th	Night	55% 5% 10% 17% 9% 3	3734
	11th to 20th	Night	57% 6% 9% 14% 12% 2	3640
	21st to end	Night	49% 4 7% 23% 13% 4	3498
April	1st to 10th	Night	53% 4 9% 19% 14% 2	1900
	11th to 20th	Night	48% 5% 8% 22% 15% 2	1875
	21st to end	Night	50% 5% 8% 20% 13% 3	1758
May	1st to 10th	Night	51% 8% 11% 20% 8% 3	2534
	11th to 20th	Night	44% 9% 14% 19% 12% 2	2496
	21st to end	Night	47% 6% 10% 19% 16% 2	2739
June	1st to 10th	Night	48% 6% 12% 21% 12% 1	1520
	11th to 20th	Night	44% 6% 11% 23% 14% 3	1520
	21st to end	Night	47% 8% 11% 20% 13% 1	1520
July	1st to 10th	Night	44% 8% 17% 20% 11% 1	2480
	11th to 20th	Night	38% 6% 19% 30% 7%	2472
	21st to end	Night	35% 7% 19% 27% 12%	2651
August	1st to 10th	Night	41% 8% 15% 28% 8%	2496
	11th to 20th	Night	40% 7% 19% 27% 7%	2797
	21st to end	Night	40% 7% 16% 23% 13% 2	3476
September	1st to 10th	Night	36% 8% 13% 27% 16% 1	1900
	11th to 20th	Night	35% 6% 14% 33% 12% 1	1962
	21st to end	Night	39% 6% 12% 29% 14%	2090
October	1st to 10th	Night	42% 6% 15% 25% 12% 1	3752
	11th to 20th	Night	41% 7% 14% 27% 11%	3831
	21st to end	Night	44% 6% 20% 17% 11% 2	4467
November	1st to 10th	Night	51% 6% 14% 21% 7% 1	2537
	11th to 20th	Night	51% 5% 14% 18% 9% 2	2717
	21st to end	Night	57% 6% 13% 17% 6% 1	2800
December	1st to 10th	Night	64% 6% 12% 13% 4	2737
	11th to 20th	Night	60% 5% 10% 16% 7% 1	3288
	21st to end	Night	66% 5% 8% 15% 5%	4884

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	21% 20% 39% 17% 4	180
	11th to 20th	Day	28% 17% 38% 12% 5% 1	180
	21st to end	Day	20% 23% 37% 15% 4 1	198
February	1st to 10th	Day	34% 26% 31% 8% 1	255
	11th to 20th	Day	22% 28% 38% 10% 1	341
	21st to end	Day	28% 24% 30% 16% 2	382
March	1st to 10th	Day	28% 20% 31% 17% 3	460
	11th to 20th	Day	23% 27% 32% 14% 4 1	460
	21st to end	Day	28% 23% 28% 14% 6% 1	506
April	1st to 10th	Day	32% 17% 30% 14% 6% 1	460
	11th to 20th	Day	33% 20% 26% 14% 7% 1	452
	21st to end	Day	30% 21% 29% 15% 4 2	460
May	1st to 10th	Day	25% 20% 34% 14% 5% 1	463
	11th to 20th	Day	23% 18% 31% 21% 5% 1	487
	21st to end	Day	23% 20% 31% 19% 6%	529
June	1st to 10th	Day	24% 17% 33% 17% 6% 1	490
	11th to 20th	Day	17% 20% 33% 19% 8% 1	490
	21st to end	Day	28% 13% 32% 18% 7% 2	490
July	1st to 10th	Day	14% 11% 38% 26% 10% 2	485
	11th to 20th	Day	17% 12% 36% 26% 8% 1	484
	21st to end	Day	15% 9% 36% 29% 11% 1	532
August	1st to 10th	Day	16% 9% 31% 29% 12% 2	486
	11th to 20th	Day	14% 9% 29% 30% 12% 6%	479
	21st to end	Day	17% 14% 29% 22% 12% 6%	539
September	1st to 10th	Day	18% 11% 33% 24% 10% 5%	490
	11th to 20th	Day	12% 11% 27% 26% 17% 7%	490
	21st to end	Day	21% 14% 26% 23% 12% 4	490
October	1st to 10th	Day	24% 19% 24% 21% 10% 1	490
	11th to 20th	Day	25% 17% 32% 19% 7% 1	475
	21st to end	Day	32% 15% 30% 18% 5%	429
November	1st to 10th	Day	29% 19% 29% 18% 4 1	395
	11th to 20th	Day	26% 23% 33% 15% 4	280
	21st to end	Day	29% 25% 32% 14% 2	200
December	1st to 10th	Day	28% 16% 33% 19% 4 1	190
	11th to 20th	Day	29% 24% 33% 12% 1 1	180
	21st to end	Day	34% 25% 24% 12% 4 1	198
January	1st to 10th	Night	24% 17% 34% 22% 3	760
	11th to 20th	Night	23% 20% 32% 21% 4	760
	21st to end	Night	16% 16% 39% 22% 6% 1	836
February	1st to 10th	Night	20% 18% 38% 20% 4 1	760
	11th to 20th	Night	20% 19% 40% 17% 3 1	743
	21st to end	Night	22% 17% 33% 25% 2	628
March	1st to 10th	Night	23% 18% 34% 22% 3	760
	11th to 20th	Night	24% 18% 34% 19% 5%	760
	21st to end	Night	22% 16% 33% 22% 6% 1	836
April	1st to 10th	Night	27% 17% 28% 23% 4	760
	11th to 20th	Night	24% 15% 33% 22% 5%	751
	21st to end	Night	25% 15% 33% 19% 7%	618
May	1st to 10th	Night	24% 13% 33% 22% 6% 2	394
	11th to 20th	Night	21% 12% 30% 29% 7% 1	374
	21st to end	Night	19% 9% 40% 24% 7%	411
June	1st to 10th	Night	25% 9% 31% 29% 7%	380
	11th to 20th	Night	24% 7% 28% 30% 10% 1	380
	21st to end	Night	21% 7% 27% 31% 13% 1	380
July	1st to 10th	Night	11% 9% 31% 35% 14% 1	370
	11th to 20th	Night	12% 6% 28% 41% 13%	368
	21st to end	Night	14% 4 26% 43% 12% 1	416
August	1st to 10th	Night	14% 5% 22% 42% 16% 2	378
	11th to 20th	Night	11% 6% 27% 32% 22% 2	549
	21st to end	Night	15% 7% 28% 32% 16% 2	836
September	1st to 10th	Night	13% 8% 31% 35% 12% 1	760
	11th to 20th	Night	16% 8% 24% 30% 20% 2	760
	21st to end	Night	20% 9% 25% 29% 16% 2	760
October	1st to 10th	Night	22% 11% 28% 27% 10% 1	760
	11th to 20th	Night	25% 13% 29% 24% 8% 1	760
	21st to end	Night	27% 15% 31% 22% 5%	836
November	1st to 10th	Night	24% 18% 29% 23% 6% 1	780
	11th to 20th	Night	23% 16% 33% 20% 7% 1	800
	21st to end	Night	28% 19% 28% 19% 5% 1	800
December	1st to 10th	Night	27% 17% 33% 17% 5%	783
	11th to 20th	Night	28% 20% 29% 18% 4 1	760
	21st to end	Night	32% 18% 31% 16% 4	836

Page generated at 2024-12-03 06:45:14. Version ac07

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