Saint-Calixte
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint-Calixte clear sky chart from 2005-11-06 to 2025-11-18.

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% 4 8% 5% 5% 5% 4 5% 6% 32%	127173
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 33%	123195
Transparency	Day	50% 6% 12% 21% 10% 1	130605
	Night	50% 5% 12% 20% 11% 1	127850
Seeing	Day	21% 16% 32% 20% 8% 2	15829
	Night	21% 12% 32% 26% 8% 1	24757

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	12% 20% 6% 13% 6% 5% 4 3 4 4 23%	3597
	11th to 20th	Day	11% 15% 6% 13% 7% 6% 5% 3 4 4 26%	3570
	21st to end	Day	8% 14% 7% 13% 7% 5% 5% 3 5% 5% 27%	3960
February	1st to 10th	Day	12% 17% 5% 11% 6% 6% 4 3 5% 5% 27%	1750
	11th to 20th	Day	11% 15% 5% 12% 6% 4 5% 4 5% 5% 27%	1841
	21st to end	Day	16% 15% 4 11% 6% 4 4 3 4 5% 28%	1650
March	1st to 10th	Day	19% 14% 5% 11% 7% 5% 4 3 4 4 24%	4476
	11th to 20th	Day	10% 13% 5% 11% 5% 5% 4 3 5% 7% 33%	4704
	21st to end	Day	17% 12% 3 8% 5% 4 4 3 4 5% 33%	5961
April	1st to 10th	Day	20% 13% 3 8% 4 4 4 3 4 5% 32%	2400
	11th to 20th	Day	22% 8% 3 7% 5% 4 5% 3 5% 5% 35%	2374
	21st to end	Day	21% 10% 3 8% 4 5% 4 3 4 5% 32%	2565
May	1st to 10th	Day	26% 10% 4 8% 5% 5% 4 3 5% 5% 24%	6318
	11th to 20th	Day	21% 9% 3 7% 4 5% 4 3 6% 8% 30%	6318
	21st to end	Day	22% 8% 3 7% 5% 5% 5% 4 5% 7% 29%	6949
June	1st to 10th	Day	21% 7% 3 7% 6% 4 5% 5% 6% 7% 29%	2800
	11th to 20th	Day	16% 6% 3 7% 5% 4 6% 5% 6% 8% 34%	2800
	21st to end	Day	21% 9% 3 7% 6% 5% 5% 5% 5% 6% 28%	2800
July	1st to 10th	Day	15% 6% 3 8% 6% 6% 6% 4 6% 8% 32%	6360
	11th to 20th	Day	13% 5% 2 6% 4 5% 6% 5% 7% 8% 38%	6360
	21st to end	Day	10% 5% 2 5% 4 4 5% 5% 6% 9% 45%	6926
August	1st to 10th	Day	14% 5% 2 7% 6% 6% 6% 5% 7% 9% 33%	4563
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 4 7% 8% 36%	4159
	21st to end	Day	16% 5% 2 7% 4 5% 5% 4 6% 8% 39%	4312
September	1st to 10th	Day	14% 6% 2 5% 4 4 4 4 6% 8% 43%	2400
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 7% 49%	2323
	21st to end	Day	18% 7% 3 6% 4 3 4 4 5% 6% 42%	2200
October	1st to 10th	Day	20% 6% 3 6% 4 4 4 3 5% 7% 37%	2051
	11th to 20th	Day	19% 10% 3 8% 5% 5% 5% 3 5% 7% 31%	1955
	21st to end	Day	23% 11% 4 7% 4 4 4 3 4 5% 31%	1980
November	1st to 10th	Day	15% 11% 3 8% 5% 5% 4 4 5% 6% 34%	1851
	11th to 20th	Day	17% 11% 4 8% 5% 4 5% 4 5% 7% 29%	1754
	21st to end	Day	21% 14% 3 8% 5% 4 5% 4 6% 6% 25%	1600
December	1st to 10th	Day	18% 17% 8% 12% 6% 4 4 3 3 5% 21%	2600
	11th to 20th	Day	17% 16% 6% 9% 4 4 3 3 4 4 29%	2986
	21st to end	Day	21% 15% 5% 9% 4 4 4 3 4 4 27%	3960
January	1st to 10th	Night	11% 20% 8% 13% 6% 4 4 3 4 4 23%	6349
	11th to 20th	Night	8% 14% 7% 18% 7% 5% 4 3 5% 5% 25%	6315
	21st to end	Night	9% 11% 6% 14% 8% 6% 6% 4 5% 5% 27%	6996
February	1st to 10th	Night	11% 13% 4 12% 7% 5% 5% 4 5% 6% 27%	2649
	11th to 20th	Night	11% 12% 5% 11% 6% 5% 5% 4 4 5% 32%	2444
	21st to end	Night	14% 12% 5% 9% 6% 5% 5% 3 5% 5% 32%	1980
March	1st to 10th	Night	20% 15% 4 10% 5% 4 3 2 4 4 29%	5364
	11th to 20th	Night	11% 14% 4 8% 5% 5% 5% 4 6% 7% 32%	5241
	21st to end	Night	15% 10% 4 9% 6% 5% 4 3 5% 5% 34%	4970
April	1st to 10th	Night	21% 12% 3 7% 5% 4 4 3 5% 5% 32%	2000
	11th to 20th	Night	19% 7% 2 6% 6% 4 4 4 5% 6% 37%	1975
	21st to end	Night	22% 8% 3 6% 3 3 5% 4 5% 6% 36%	1835
May	1st to 10th	Night	25% 9% 3 7% 5% 4 5% 3 5% 6% 26%	3650
	11th to 20th	Night	21% 8% 3 6% 4 4 5% 3 5% 7% 33%	3575
	21st to end	Night	22% 8% 3 7% 5% 5% 5% 4 5% 7% 30%	3926
June	1st to 10th	Night	18% 8% 2 7% 5% 4 4 3 6% 9% 34%	1600
	11th to 20th	Night	18% 8% 3 6% 4 4 5% 4 6% 6% 38%	1600
	21st to end	Night	20% 6% 3 5% 5% 4 5% 4 5% 7% 36%	1600
July	1st to 10th	Night	14% 6% 3 7% 5% 5% 6% 5% 7% 8% 36%	3600
	11th to 20th	Night	14% 6% 2 6% 4 4 4 4 6% 8% 44%	3600
	21st to end	Night	9% 5% 2 5% 4 5% 4 5% 6% 8% 48%	3926
August	1st to 10th	Night	13% 6% 3 7% 4 5% 5% 4 5% 8% 41%	2586
	11th to 20th	Night	16% 6% 2 6% 4 3 4 3 5% 7% 43%	2852
	21st to end	Night	17% 7% 2 6% 4 4 4 3 5% 6% 43%	3586
September	1st to 10th	Night	10% 4 2 5% 4 4 4 3 6% 7% 49%	2000
	11th to 20th	Night	13% 5% 2 4 4 3 3 3 5% 7% 51%	2076
	21st to end	Night	17% 6% 2 5% 4 4 3 3 5% 6% 46%	2200
October	1st to 10th	Night	17% 7% 3 6% 4 4 3 2 5% 5% 43%	2345
	11th to 20th	Night	18% 8% 3 6% 4 4 4 4 5% 7% 38%	2445
	21st to end	Night	21% 8% 3 7% 5% 4 4 3 5% 7% 33%	2860
November	1st to 10th	Night	17% 9% 3 7% 6% 4 4 3 5% 7% 33%	2667
	11th to 20th	Night	18% 9% 3 8% 5% 5% 4 4 5% 6% 34%	2799
	21st to end	Night	19% 14% 4 8% 5% 4 4 3 4 6% 30%	2800
December	1st to 10th	Night	16% 14% 5% 10% 6% 5% 5% 4 6% 7% 22%	4580
	11th to 20th	Night	22% 13% 5% 9% 5% 4 3 3 3 4 29%	5208
	21st to end	Night	21% 18% 4 8% 4 3 2 2 3 4 30%	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	62% 5% 9% 19% 5% 1	3598
	11th to 20th	Day	58% 7% 8% 17% 7% 3	3600
	21st to end	Day	55% 5% 8% 17% 12% 2	3960
February	1st to 10th	Day	59% 4 7% 17% 9% 2	1750
	11th to 20th	Day	58% 6% 10% 15% 11% 1	1850
	21st to end	Day	59% 5% 7% 16% 9% 3	1650
March	1st to 10th	Day	62% 5% 6% 12% 11% 4	4479
	11th to 20th	Day	49% 6% 16% 14% 11% 3	4704
	21st to end	Day	52% 5% 7% 15% 18% 3	5961
April	1st to 10th	Day	55% 4 8% 18% 13% 3	2400
	11th to 20th	Day	50% 5% 9% 21% 13% 2	2374
	21st to end	Day	53% 6% 8% 18% 12% 3	2565
May	1st to 10th	Day	60% 5% 8% 18% 8% 1	6329
	11th to 20th	Day	51% 7% 16% 16% 8% 2	6322
	21st to end	Day	51% 7% 11% 17% 12% 2	6949
June	1st to 10th	Day	51% 7% 10% 19% 12% 2	2800
	11th to 20th	Day	43% 8% 12% 23% 11% 3	2800
	21st to end	Day	54% 7% 11% 18% 9% 1	2800
July	1st to 10th	Day	46% 7% 14% 24% 8%	6290
	11th to 20th	Day	38% 8% 15% 28% 10%	6285
	21st to end	Day	33% 7% 16% 34% 10%	6728
August	1st to 10th	Day	44% 8% 17% 22% 9%	4549
	11th to 20th	Day	42% 8% 17% 26% 6%	4201
	21st to end	Day	41% 7% 16% 21% 13% 1	4312
September	1st to 10th	Day	36% 7% 15% 29% 12%	2400
	11th to 20th	Day	33% 7% 14% 32% 14% 1	2323
	21st to end	Day	42% 5% 14% 25% 13%	2200
October	1st to 10th	Day	42% 6% 15% 27% 10%	3337
	11th to 20th	Day	43% 5% 15% 28% 8%	3158
	21st to end	Day	42% 5% 21% 20% 10% 1	3180
November	1st to 10th	Day	48% 6% 13% 22% 10% 1	1851
	11th to 20th	Day	52% 6% 11% 19% 11% 1	1754
	21st to end	Day	57% 7% 13% 16% 6% 1	1600
December	1st to 10th	Day	67% 3 10% 15% 4	2600
	11th to 20th	Day	56% 5% 9% 18% 12%	2986
	21st to end	Day	61% 3 10% 15% 10%	3960
January	1st to 10th	Night	63% 5% 12% 15% 5%	6349
	11th to 20th	Night	61% 6% 11% 17% 5% 1	6360
	21st to end	Night	55% 7% 11% 12% 14% 1	6996
February	1st to 10th	Night	57% 5% 9% 19% 9% 1	2649
	11th to 20th	Night	53% 5% 10% 20% 10% 1	2446
	21st to end	Night	53% 4 9% 19% 12% 2	1980
March	1st to 10th	Night	59% 4 8% 13% 12% 4	5374
	11th to 20th	Night	49% 7% 13% 16% 12% 3	5242
	21st to end	Night	51% 4 7% 21% 13% 3	4970
April	1st to 10th	Night	53% 5% 7% 18% 15% 2	2000
	11th to 20th	Night	48% 4 9% 21% 15% 2	1975
	21st to end	Night	49% 4 9% 21% 14% 3	1835
May	1st to 10th	Night	57% 6% 10% 18% 7% 2	3656
	11th to 20th	Night	49% 7% 14% 18% 10% 2	3576
	21st to end	Night	52% 7% 11% 17% 12% 1	3927
June	1st to 10th	Night	48% 5% 12% 21% 13% 1	1600
	11th to 20th	Night	45% 6% 11% 21% 14% 3	1600
	21st to end	Night	47% 7% 12% 20% 14% 1	1600
July	1st to 10th	Night	42% 7% 20% 22% 8% 1	3560
	11th to 20th	Night	36% 6% 18% 31% 8%	3552
	21st to end	Night	33% 6% 17% 32% 12%	3809
August	1st to 10th	Night	42% 6% 15% 28% 9%	2576
	11th to 20th	Night	40% 5% 19% 27% 8%	2876
	21st to end	Night	42% 6% 15% 23% 13% 1	3586
September	1st to 10th	Night	34% 6% 18% 28% 15% 1	2000
	11th to 20th	Night	33% 4 16% 34% 12% 1	2076
	21st to end	Night	39% 6% 12% 29% 15%	2200
October	1st to 10th	Night	44% 5% 13% 25% 12% 1	3839
	11th to 20th	Night	40% 5% 13% 30% 12%	3981
	21st to end	Night	42% 5% 19% 19% 13% 2	4610
November	1st to 10th	Night	49% 5% 13% 23% 8% 1	2667
	11th to 20th	Night	51% 6% 11% 20% 11% 2	2799
	21st to end	Night	56% 5% 12% 19% 8% 1	2800
December	1st to 10th	Night	61% 5% 14% 16% 5%	4580
	11th to 20th	Night	58% 5% 8% 17% 12% 1	5208
	21st to end	Night	61% 3 7% 15% 14%	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	20% 20% 36% 22% 3	200
	11th to 20th	Day	26% 17% 39% 15% 4 1	200
	21st to end	Day	17% 20% 39% 20% 5%	220
February	1st to 10th	Day	25% 28% 39% 8%	275
	11th to 20th	Day	21% 23% 39% 14% 2	388
	21st to end	Day	26% 20% 35% 17% 3	414
March	1st to 10th	Day	26% 18% 34% 18% 4	500
	11th to 20th	Day	20% 24% 38% 15% 3 1	500
	21st to end	Day	28% 20% 31% 14% 6% 1	550
April	1st to 10th	Day	28% 20% 30% 16% 4 1	500
	11th to 20th	Day	32% 18% 29% 14% 7% 1	492
	21st to end	Day	30% 19% 31% 15% 4 1	500
May	1st to 10th	Day	26% 19% 34% 16% 4 1	503
	11th to 20th	Day	21% 18% 33% 20% 7% 1	527
	21st to end	Day	21% 19% 33% 20% 5% 1	573
June	1st to 10th	Day	23% 15% 34% 19% 7% 1	530
	11th to 20th	Day	18% 17% 33% 20% 11% 1	530
	21st to end	Day	25% 12% 32% 22% 8% 1	530
July	1st to 10th	Day	14% 12% 35% 26% 10% 3	525
	11th to 20th	Day	15% 10% 35% 28% 10% 2	524
	21st to end	Day	13% 10% 32% 31% 13% 2	576
August	1st to 10th	Day	12% 9% 28% 34% 15% 2	526
	11th to 20th	Day	12% 8% 26% 30% 15% 7%	519
	21st to end	Day	15% 13% 30% 23% 13% 6%	583
September	1st to 10th	Day	17% 9% 34% 23% 12% 5%	530
	11th to 20th	Day	12% 10% 24% 30% 17% 8%	530
	21st to end	Day	19% 13% 28% 22% 13% 5%	530
October	1st to 10th	Day	22% 14% 29% 21% 11% 2	530
	11th to 20th	Day	20% 19% 32% 21% 7% 1	505
	21st to end	Day	28% 15% 31% 21% 5%	462
November	1st to 10th	Day	27% 19% 30% 19% 5%	425
	11th to 20th	Day	23% 21% 32% 17% 6%	312
	21st to end	Day	29% 17% 37% 13% 5% 1	200
December	1st to 10th	Day	27% 18% 28% 21% 7% 1	200
	11th to 20th	Day	27% 23% 35% 14% 2 1	200
	21st to end	Day	30% 22% 28% 13% 7% 1	220
January	1st to 10th	Night	23% 15% 36% 22% 4	800
	11th to 20th	Night	21% 15% 34% 24% 6%	800
	21st to end	Night	14% 13% 40% 26% 6%	880
February	1st to 10th	Night	18% 15% 41% 22% 4 1	800
	11th to 20th	Night	19% 15% 42% 20% 4	783
	21st to end	Night	21% 15% 36% 25% 3	660
March	1st to 10th	Night	25% 15% 34% 22% 4	800
	11th to 20th	Night	23% 16% 34% 21% 6%	800
	21st to end	Night	21% 14% 35% 25% 5%	880
April	1st to 10th	Night	28% 14% 33% 21% 4	800
	11th to 20th	Night	25% 14% 31% 24% 5% 1	791
	21st to end	Night	28% 14% 33% 19% 6%	635
May	1st to 10th	Night	24% 11% 34% 24% 6% 1	430
	11th to 20th	Night	22% 11% 28% 30% 7% 1	394
	21st to end	Night	21% 9% 39% 24% 7%	433
June	1st to 10th	Night	23% 9% 32% 28% 7%	400
	11th to 20th	Night	21% 7% 30% 31% 11%	400
	21st to end	Night	22% 6% 28% 31% 13% 1	400
July	1st to 10th	Night	12% 7% 34% 33% 12% 2	390
	11th to 20th	Night	12% 5% 27% 43% 12% 1	388
	21st to end	Night	11% 6% 29% 42% 11% 1	438
August	1st to 10th	Night	14% 4 19% 44% 18% 1	398
	11th to 20th	Night	15% 4 24% 35% 20% 2	568
	21st to end	Night	16% 6% 27% 32% 17% 2	880
September	1st to 10th	Night	13% 5% 31% 36% 13% 1	800
	11th to 20th	Night	15% 6% 25% 33% 20% 2	800
	21st to end	Night	19% 8% 29% 29% 14% 2	800
October	1st to 10th	Night	20% 10% 31% 27% 12% 1	800
	11th to 20th	Night	23% 10% 33% 25% 10% 1	800
	21st to end	Night	26% 9% 35% 23% 6%	880
November	1st to 10th	Night	23% 13% 32% 24% 7% 1	820
	11th to 20th	Night	24% 14% 32% 22% 9% 1	829
	21st to end	Night	26% 17% 30% 20% 6% 1	800
December	1st to 10th	Night	26% 13% 33% 20% 7%	800
	11th to 20th	Night	26% 17% 30% 22% 5% 1	800
	21st to end	Night	31% 14% 30% 21% 4	880

Page generated at 2025-11-15 00:56:01. Version ac07

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