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 2024-01-12.

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% 9% 4 7% 6% 3 5% 5% 5% 6% 33%	74760
	Night	17% 10% 4 7% 6% 3 4 4 5% 6% 35%	74963
Transparency	Day	50% 6% 11% 20% 11% 1	74465
	Night	50% 5% 12% 21% 11% 1	74792
Seeing	Day	21% 16% 32% 21% 8% 2	13420
	Night	21% 11% 33% 26% 8% 1	22499

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	15% 16% 5% 9% 8% 5% 5% 5% 4 4 24%	1517
	11th to 20th	Day	16% 17% 5% 8% 6% 4 5% 4 3 4 28%	1454
	21st to end	Day	11% 12% 6% 9% 8% 4 5% 5% 5% 6% 30%	1584
February	1st to 10th	Day	13% 16% 6% 9% 7% 3 6% 3 5% 6% 26%	1575
	11th to 20th	Day	12% 15% 5% 11% 6% 4 5% 5% 5% 5% 28%	1652
	21st to end	Day	16% 14% 6% 10% 7% 3 4 4 4 5% 27%	1480
March	1st to 10th	Day	15% 11% 6% 9% 8% 5% 4 3 5% 5% 29%	1797
	11th to 20th	Day	15% 11% 6% 8% 7% 4 4 4 5% 5% 32%	1872
	21st to end	Day	19% 10% 3 6% 6% 3 4 4 5% 6% 35%	2367
April	1st to 10th	Day	21% 11% 4 7% 5% 4 4 4 4 5% 31%	2160
	11th to 20th	Day	22% 6% 3 6% 6% 3 5% 4 5% 5% 36%	2134
	21st to end	Day	22% 10% 3 7% 5% 4 4 4 4 5% 32%	2308
May	1st to 10th	Day	21% 9% 3 6% 6% 3 4 4 4 6% 34%	2506
	11th to 20th	Day	21% 7% 2 6% 5% 4 4 4 5% 6% 35%	2478
	21st to end	Day	19% 6% 3 6% 6% 4 5% 5% 5% 7% 34%	2725
June	1st to 10th	Day	23% 7% 3 5% 7% 3 4 6% 6% 8% 29%	2520
	11th to 20th	Day	17% 6% 3 6% 6% 3 6% 6% 6% 8% 34%	2520
	21st to end	Day	21% 8% 4 6% 7% 4 5% 6% 5% 6% 28%	2520
July	1st to 10th	Day	13% 5% 2 6% 6% 5% 6% 6% 6% 8% 39%	2520
	11th to 20th	Day	14% 5% 3 5% 6% 4 7% 6% 8% 9% 33%	2520
	21st to end	Day	13% 6% 3 5% 6% 4 6% 7% 7% 8% 35%	2744
August	1st to 10th	Day	13% 6% 3 6% 7% 4 7% 7% 6% 8% 35%	2506
	11th to 20th	Day	12% 5% 2 6% 7% 5% 6% 6% 7% 8% 36%	2306
	21st to end	Day	14% 5% 3 6% 5% 3 5% 5% 5% 8% 42%	2376
September	1st to 10th	Day	15% 5% 2 4 5% 3 5% 5% 6% 8% 42%	2160
	11th to 20th	Day	14% 5% 2 5% 4 2 4 4 5% 7% 47%	2091
	21st to end	Day	18% 6% 3 5% 4 2 4 4 5% 6% 42%	1980
October	1st to 10th	Day	22% 6% 3 5% 4 3 5% 4 5% 7% 36%	1847
	11th to 20th	Day	21% 9% 3 7% 7% 4 5% 5% 5% 6% 28%	1760
	21st to end	Day	24% 11% 4 6% 5% 4 3 4 4 5% 30%	1782
November	1st to 10th	Day	15% 10% 3 6% 6% 3 4 4 6% 7% 36%	1671
	11th to 20th	Day	18% 10% 5% 8% 6% 3 5% 5% 5% 7% 29%	1610
	21st to end	Day	21% 13% 3 6% 6% 3 4 5% 6% 6% 27%	1520
December	1st to 10th	Day	22% 16% 5% 8% 6% 3 4 4 4 5% 23%	1520
	11th to 20th	Day	20% 14% 6% 8% 5% 3 3 4 4 5% 28%	1906
	21st to end	Day	25% 16% 5% 9% 5% 3 3 3 3 4 24%	2772
January	1st to 10th	Night	14% 16% 5% 10% 7% 4 5% 4 5% 4 24%	2649
	11th to 20th	Night	15% 15% 6% 10% 7% 3 5% 4 5% 5% 27%	2546
	21st to end	Night	10% 10% 5% 8% 8% 4 5% 5% 5% 6% 34%	2772
February	1st to 10th	Night	12% 11% 5% 10% 9% 4 6% 5% 5% 6% 27%	2384
	11th to 20th	Night	12% 11% 5% 9% 7% 4 6% 5% 4 5% 33%	2193
	21st to end	Night	15% 11% 5% 8% 6% 3 5% 4 5% 4 33%	1776
March	1st to 10th	Night	16% 12% 6% 8% 6% 4 4 5% 4 5% 31%	2150
	11th to 20th	Night	15% 13% 5% 6% 5% 3 4 5% 4 6% 32%	2087
	21st to end	Night	16% 8% 3 6% 6% 3 4 4 4 5% 40%	1988
April	1st to 10th	Night	21% 11% 3 7% 6% 3 3 4 5% 5% 32%	1800
	11th to 20th	Night	19% 6% 2 5% 6% 3 5% 5% 5% 6% 39%	1775
	21st to end	Night	22% 8% 3 6% 4 2 5% 4 4 6% 36%	1652
May	1st to 10th	Night	21% 7% 3 6% 5% 4 4 4 4 6% 37%	1468
	11th to 20th	Night	20% 7% 3 4 5% 3 4 4 5% 7% 38%	1415
	21st to end	Night	18% 5% 3 5% 5% 3 5% 5% 4 7% 40%	1550
June	1st to 10th	Night	19% 7% 3 6% 5% 3 4 4 6% 8% 34%	1440
	11th to 20th	Night	19% 7% 3 6% 4 3 4 5% 5% 6% 38%	1440
	21st to end	Night	19% 6% 3 4 5% 3 5% 6% 5% 8% 37%	1440
July	1st to 10th	Night	11% 5% 2 4 5% 3 5% 5% 6% 8% 45%	1440
	11th to 20th	Night	12% 5% 2 6% 5% 3 5% 5% 6% 8% 42%	1440
	21st to end	Night	12% 5% 3 5% 4 3 5% 5% 6% 8% 44%	1574
August	1st to 10th	Night	11% 5% 2 5% 5% 3 4 6% 6% 10% 42%	1432
	11th to 20th	Night	13% 5% 2 5% 6% 2 5% 4 5% 8% 45%	1572
	21st to end	Night	15% 6% 2 4 5% 3 4 4 5% 7% 46%	1980
September	1st to 10th	Night	11% 4 2 5% 5% 3 5% 4 6% 8% 47%	1800
	11th to 20th	Night	14% 4 2 4 5% 3 3 4 5% 7% 49%	1868
	21st to end	Night	18% 5% 2 4 3 3 4 3 5% 7% 46%	1980
October	1st to 10th	Night	18% 7% 3 6% 5% 3 4 3 5% 5% 42%	2110
	11th to 20th	Night	20% 8% 3 6% 4 3 4 5% 5% 7% 36%	2200
	21st to end	Night	22% 9% 3 6% 6% 3 4 4 5% 6% 32%	2574
November	1st to 10th	Night	17% 9% 3 6% 6% 3 4 4 5% 8% 34%	2407
	11th to 20th	Night	18% 8% 3 7% 6% 3 5% 5% 5% 6% 34%	2569
	21st to end	Night	19% 13% 4 7% 5% 3 4 4 4 6% 30%	2660
December	1st to 10th	Night	19% 14% 5% 9% 6% 3 5% 5% 6% 6% 23%	2660
	11th to 20th	Night	21% 13% 5% 7% 6% 3 3 4 4 5% 29%	3288
	21st to end	Night	24% 18% 5% 7% 5% 2 3 3 4 4 25%	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	62% 5% 9% 16% 8%	1518
	11th to 20th	Day	60% 5% 8% 14% 12% 2	1454
	21st to end	Day	53% 5% 8% 19% 12% 2	1584
February	1st to 10th	Day	60% 5% 7% 17% 9% 2	1575
	11th to 20th	Day	58% 5% 10% 15% 11% 1	1661
	21st to end	Day	60% 4 7% 17% 9% 3	1480
March	1st to 10th	Day	57% 5% 7% 17% 11% 2	1800
	11th to 20th	Day	52% 5% 11% 15% 13% 3	1872
	21st to end	Day	51% 5% 10% 17% 13% 4	2367
April	1st to 10th	Day	56% 4 8% 18% 12% 3	2160
	11th to 20th	Day	49% 5% 9% 22% 13% 2	2134
	21st to end	Day	54% 6% 7% 18% 12% 4	2308
May	1st to 10th	Day	51% 4 8% 21% 13% 3	2506
	11th to 20th	Day	48% 6% 9% 18% 17% 3	2482
	21st to end	Day	47% 7% 11% 19% 15% 2	2725
June	1st to 10th	Day	51% 7% 10% 18% 11% 2	2520
	11th to 20th	Day	44% 8% 11% 23% 12% 3	2520
	21st to end	Day	54% 7% 11% 17% 9% 1	2520
July	1st to 10th	Day	40% 9% 14% 25% 11% 1	2450
	11th to 20th	Day	41% 9% 15% 24% 10%	2445
	21st to end	Day	42% 9% 15% 24% 9%	2591
August	1st to 10th	Day	44% 10% 16% 23% 7%	2492
	11th to 20th	Day	41% 10% 17% 23% 9%	2306
	21st to end	Day	38% 7% 16% 24% 13% 1	2376
September	1st to 10th	Day	37% 8% 15% 27% 13%	2160
	11th to 20th	Day	35% 7% 13% 31% 13% 1	2091
	21st to end	Day	43% 6% 14% 25% 12%	1980
October	1st to 10th	Day	48% 6% 12% 22% 12% 1	1847
	11th to 20th	Day	54% 8% 12% 19% 6%	1760
	21st to end	Day	57% 5% 12% 16% 9% 1	1782
November	1st to 10th	Day	46% 7% 14% 21% 10% 1	1671
	11th to 20th	Day	53% 6% 12% 18% 11% 1	1610
	21st to end	Day	56% 8% 13% 16% 7% 1	1520
December	1st to 10th	Day	64% 4 11% 14% 6%	1520
	11th to 20th	Day	58% 5% 10% 19% 8%	1906
	21st to end	Day	66% 3 11% 13% 7%	2772
January	1st to 10th	Night	61% 5% 10% 17% 6% 1	2649
	11th to 20th	Night	60% 4 12% 13% 8% 2	2546
	21st to end	Night	51% 4 12% 18% 13% 2	2772
February	1st to 10th	Night	58% 6% 8% 19% 8% 1	2384
	11th to 20th	Night	53% 6% 9% 21% 10% 1	2195
	21st to end	Night	54% 4 9% 18% 13% 2	1776
March	1st to 10th	Night	55% 5% 9% 18% 11% 2	2160
	11th to 20th	Night	53% 5% 9% 16% 14% 3	2088
	21st to end	Night	48% 4 9% 20% 15% 4	1988
April	1st to 10th	Night	53% 6% 7% 18% 14% 2	1800
	11th to 20th	Night	46% 4 10% 22% 15% 2	1775
	21st to end	Night	50% 4 9% 20% 14% 3	1652
May	1st to 10th	Night	49% 4 8% 20% 14% 5%	1468
	11th to 20th	Night	45% 5% 10% 20% 16% 4	1416
	21st to end	Night	43% 7% 11% 21% 15% 3	1551
June	1st to 10th	Night	48% 5% 12% 22% 12% 1	1440
	11th to 20th	Night	45% 7% 10% 22% 14% 3	1440
	21st to end	Night	46% 8% 12% 20% 13%	1440
July	1st to 10th	Night	34% 8% 15% 28% 14% 1	1400
	11th to 20th	Night	37% 8% 15% 28% 11%	1392
	21st to end	Night	37% 8% 18% 25% 12%	1486
August	1st to 10th	Night	38% 8% 18% 26% 10%	1422
	11th to 20th	Night	36% 7% 18% 27% 11%	1572
	21st to end	Night	37% 6% 17% 28% 12%	1980
September	1st to 10th	Night	35% 6% 18% 26% 14% 1	1800
	11th to 20th	Night	34% 5% 16% 33% 11% 1	1868
	21st to end	Night	38% 6% 12% 30% 14%	1980
October	1st to 10th	Night	46% 5% 9% 25% 14% 1	2110
	11th to 20th	Night	48% 6% 14% 23% 9%	2200
	21st to end	Night	53% 6% 13% 18% 10% 1	2574
November	1st to 10th	Night	48% 6% 14% 22% 9% 1	2407
	11th to 20th	Night	50% 6% 12% 20% 10% 2	2569
	21st to end	Night	56% 5% 12% 19% 9% 1	2660
December	1st to 10th	Night	61% 6% 12% 16% 5%	2660
	11th to 20th	Night	58% 5% 9% 19% 8% 1	3288
	21st to end	Night	64% 4 9% 17% 6% 1	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	19% 18% 36% 23% 3	180
	11th to 20th	Day	26% 15% 38% 16% 4 1	164
	21st to end	Day	17% 19% 39% 20% 5%	176
February	1st to 10th	Day	28% 26% 38% 7%	220
	11th to 20th	Day	22% 21% 40% 14% 2	319
	21st to end	Day	27% 21% 33% 17% 3	346
March	1st to 10th	Day	24% 18% 35% 18% 5%	420
	11th to 20th	Day	21% 24% 36% 15% 3 1	420
	21st to end	Day	28% 19% 30% 15% 7% 1	462
April	1st to 10th	Day	27% 18% 31% 18% 5% 1	420
	11th to 20th	Day	29% 19% 29% 15% 7% 2	412
	21st to end	Day	30% 17% 31% 16% 4 1	420
May	1st to 10th	Day	25% 19% 34% 17% 4 1	423
	11th to 20th	Day	21% 18% 34% 19% 7% 1	447
	21st to end	Day	19% 21% 34% 20% 5% 1	485
June	1st to 10th	Day	23% 15% 34% 19% 8% 1	450
	11th to 20th	Day	18% 16% 32% 21% 12% 1	450
	21st to end	Day	23% 11% 31% 24% 9% 1	450
July	1st to 10th	Day	13% 11% 33% 28% 12% 3	445
	11th to 20th	Day	15% 8% 35% 28% 11% 3	444
	21st to end	Day	14% 9% 30% 32% 13% 2	488
August	1st to 10th	Day	13% 10% 27% 33% 16% 2	446
	11th to 20th	Day	12% 8% 26% 32% 14% 8%	439
	21st to end	Day	14% 14% 30% 23% 12% 7%	495
September	1st to 10th	Day	17% 8% 36% 23% 11% 6%	450
	11th to 20th	Day	14% 12% 26% 28% 14% 7%	450
	21st to end	Day	19% 13% 28% 21% 14% 5%	450
October	1st to 10th	Day	24% 15% 29% 18% 11% 2	450
	11th to 20th	Day	21% 19% 30% 20% 7% 2	430
	21st to end	Day	29% 16% 29% 21% 4 1	396
November	1st to 10th	Day	25% 18% 32% 19% 6%	365
	11th to 20th	Day	23% 20% 34% 16% 7%	270
	21st to end	Day	27% 17% 36% 14% 5% 1	180
December	1st to 10th	Day	28% 16% 28% 21% 7%	180
	11th to 20th	Day	25% 23% 37% 13% 2 1	180
	21st to end	Day	31% 24% 28% 10% 7% 1	198
January	1st to 10th	Night	23% 15% 35% 23% 4	760
	11th to 20th	Night	22% 14% 35% 24% 6%	728
	21st to end	Night	14% 13% 40% 26% 6% 1	792
February	1st to 10th	Night	18% 15% 40% 21% 4 1	720
	11th to 20th	Night	19% 14% 43% 20% 5%	703
	21st to end	Night	21% 16% 36% 24% 3 1	592
March	1st to 10th	Night	23% 16% 35% 22% 4	720
	11th to 20th	Night	23% 16% 33% 21% 7%	720
	21st to end	Night	21% 13% 34% 26% 5%	792
April	1st to 10th	Night	28% 14% 32% 22% 5%	720
	11th to 20th	Night	24% 14% 31% 25% 5% 1	711
	21st to end	Night	28% 13% 32% 20% 6%	572
May	1st to 10th	Night	22% 11% 35% 24% 6% 1	388
	11th to 20th	Night	23% 12% 29% 29% 7% 1	354
	21st to end	Night	21% 7% 39% 25% 8%	389
June	1st to 10th	Night	24% 9% 33% 27% 8%	360
	11th to 20th	Night	23% 7% 29% 29% 13%	360
	21st to end	Night	21% 6% 28% 31% 14% 1	360
July	1st to 10th	Night	12% 7% 35% 31% 13% 2	350
	11th to 20th	Night	11% 5% 29% 42% 12% 1	348
	21st to end	Night	11% 5% 30% 41% 12% 1	394
August	1st to 10th	Night	15% 4 19% 43% 18% 1	358
	11th to 20th	Night	15% 4 25% 34% 20% 3	508
	21st to end	Night	15% 6% 28% 31% 17% 2	792
September	1st to 10th	Night	14% 5% 32% 36% 12% 1	720
	11th to 20th	Night	16% 7% 26% 32% 18% 2	720
	21st to end	Night	19% 8% 29% 28% 14% 2	720
October	1st to 10th	Night	20% 10% 31% 27% 11% 1	720
	11th to 20th	Night	23% 9% 32% 24% 10% 1	720
	21st to end	Night	27% 9% 34% 23% 6%	792
November	1st to 10th	Night	22% 13% 33% 24% 7% 1	740
	11th to 20th	Night	23% 13% 32% 22% 9% 1	760
	21st to end	Night	25% 16% 31% 21% 6% 1	760
December	1st to 10th	Night	26% 13% 33% 20% 7%	760
	11th to 20th	Night	25% 17% 30% 22% 5% 1	760
	21st to end	Night	32% 14% 31% 19% 3	836

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