Murdochville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Murdochville clear sky chart from 2005-11-06 to 2024-01-16.

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% 13% 5% 9% 8% 4 5% 5% 5% 6% 25%	74677
	Night	13% 12% 5% 10% 8% 5% 6% 5% 5% 6% 25%	75129
Transparency	Day	59% 5% 10% 17% 8% 1	74361
	Night	58% 5% 11% 18% 8% 1	74980
Seeing	Day	27% 21% 30% 15% 6% 1	15283
	Night	24% 20% 29% 19% 7% 1	23035

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	10% 15% 6% 13% 10% 6% 7% 6% 6% 5% 14%	1327
	11th to 20th	Day	9% 13% 6% 12% 10% 5% 6% 7% 6% 7% 18%	1295
	21st to end	Day	6% 10% 4 10% 9% 5% 7% 6% 7% 7% 27%	1582
February	1st to 10th	Day	6% 10% 5% 10% 9% 6% 10% 6% 7% 8% 23%	1620
	11th to 20th	Day	7% 16% 7% 11% 9% 4 6% 5% 5% 6% 23%	1573
	21st to end	Day	5% 12% 5% 11% 9% 6% 7% 7% 6% 7% 25%	1340
March	1st to 10th	Day	10% 14% 8% 12% 7% 4 6% 5% 5% 7% 24%	1900
	11th to 20th	Day	10% 15% 7% 11% 9% 5% 6% 4 5% 5% 22%	1980
	21st to end	Day	12% 18% 7% 8% 7% 3 6% 4 4 5% 26%	2178
April	1st to 10th	Day	13% 17% 7% 12% 9% 5% 5% 4 4 4 19%	2165
	11th to 20th	Day	13% 15% 5% 10% 6% 4 5% 4 4 5% 27%	2312
	21st to end	Day	17% 17% 5% 8% 6% 4 4 4 3 5% 27%	2340
May	1st to 10th	Day	21% 17% 5% 7% 5% 3 4 4 4 4 26%	2456
	11th to 20th	Day	20% 14% 4 7% 6% 3 4 4 4 5% 29%	2483
	21st to end	Day	20% 13% 4 6% 6% 4 4 4 6% 6% 27%	2919
June	1st to 10th	Day	23% 12% 4 7% 6% 3 4 5% 6% 6% 25%	2700
	11th to 20th	Day	21% 7% 3 7% 6% 3 5% 5% 5% 7% 31%	2700
	21st to end	Day	24% 9% 3 7% 7% 3 4 4 6% 6% 26%	2700
July	1st to 10th	Day	20% 8% 4 7% 6% 3 5% 5% 7% 8% 27%	2700
	11th to 20th	Day	14% 9% 3 6% 6% 4 6% 6% 7% 7% 32%	2700
	21st to end	Day	17% 8% 3 7% 8% 4 6% 6% 5% 7% 29%	2906
August	1st to 10th	Day	19% 8% 3 7% 7% 3 7% 6% 7% 7% 27%	2349
	11th to 20th	Day	19% 8% 3 7% 7% 3 5% 5% 5% 7% 31%	2304
	21st to end	Day	16% 10% 3 7% 6% 4 6% 5% 6% 7% 29%	2574
September	1st to 10th	Day	22% 8% 3 5% 5% 3 5% 5% 5% 5% 35%	2174
	11th to 20th	Day	20% 10% 3 5% 5% 3 4 3 4 6% 39%	2034
	21st to end	Day	16% 13% 4 8% 6% 4 4 3 5% 5% 33%	1963
October	1st to 10th	Day	14% 16% 3 7% 6% 3 5% 4 4 6% 33%	1800
	11th to 20th	Day	18% 22% 5% 8% 6% 3 3 4 4 6% 22%	1800
	21st to end	Day	20% 20% 8% 8% 5% 3 4 4 4 5% 18%	1822
November	1st to 10th	Day	15% 16% 10% 10% 8% 4 5% 5% 6% 4 19%	1485
	11th to 20th	Day	14% 13% 6% 17% 9% 4 5% 4 5% 5% 16%	1520
	21st to end	Day	13% 16% 7% 17% 11% 4 4 4 5% 5% 15%	1520
December	1st to 10th	Day	13% 12% 6% 18% 13% 5% 7% 5% 5% 6% 10%	1357
	11th to 20th	Day	7% 14% 5% 16% 15% 7% 6% 7% 6% 5% 11%	1668
	21st to end	Day	9% 12% 4 15% 15% 6% 7% 6% 5% 4 17%	2431
January	1st to 10th	Night	10% 15% 6% 13% 10% 6% 9% 7% 7% 5% 12%	2838
	11th to 20th	Night	9% 12% 6% 11% 10% 6% 8% 9% 6% 6% 17%	2787
	21st to end	Night	6% 9% 5% 10% 10% 7% 8% 6% 6% 9% 23%	2771
February	1st to 10th	Night	6% 11% 4 9% 9% 6% 11% 9% 7% 7% 21%	2340
	11th to 20th	Night	9% 16% 5% 9% 9% 5% 9% 8% 6% 6% 18%	2273
	21st to end	Night	5% 13% 5% 10% 9% 6% 8% 6% 6% 6% 25%	1911
March	1st to 10th	Night	10% 13% 9% 9% 9% 4 7% 5% 4 5% 26%	2046
	11th to 20th	Night	10% 13% 6% 13% 10% 4 7% 4 5% 4 25%	1979
	21st to end	Night	11% 15% 7% 10% 7% 4 5% 4 5% 6% 26%	2178
April	1st to 10th	Night	17% 14% 5% 11% 8% 5% 6% 5% 6% 5% 20%	1792
	11th to 20th	Night	15% 12% 4 6% 6% 4 5% 4 5% 7% 33%	1598
	21st to end	Night	19% 12% 5% 9% 5% 2 3 4 5% 6% 30%	1620
May	1st to 10th	Night	21% 12% 3 6% 6% 4 5% 4 4 5% 30%	1504
	11th to 20th	Night	18% 14% 2 6% 4 3 4 5% 5% 7% 32%	1416
	21st to end	Night	18% 9% 4 5% 8% 4 5% 5% 5% 7% 29%	1365
June	1st to 10th	Night	21% 9% 4 6% 6% 3 5% 5% 5% 8% 29%	1260
	11th to 20th	Night	20% 8% 4 6% 5% 3 4 3 5% 7% 35%	1260
	21st to end	Night	21% 7% 3 6% 4 4 6% 5% 7% 6% 31%	1260
July	1st to 10th	Night	15% 8% 3 4 5% 4 5% 5% 6% 9% 35%	1260
	11th to 20th	Night	12% 7% 3 6% 6% 3 6% 5% 6% 9% 38%	1260
	21st to end	Night	13% 8% 4 5% 5% 4 5% 5% 6% 8% 37%	1392
August	1st to 10th	Night	14% 6% 3 5% 5% 3 5% 6% 7% 8% 38%	1587
	11th to 20th	Night	15% 8% 3 4 6% 3 5% 5% 6% 7% 38%	1596
	21st to end	Night	12% 9% 3 5% 7% 3 5% 5% 5% 7% 39%	1782
September	1st to 10th	Night	17% 7% 3 5% 5% 3 5% 4 5% 6% 40%	1786
	11th to 20th	Night	17% 9% 3 6% 5% 3 4 4 4 6% 38%	1923
	21st to end	Night	17% 9% 2 5% 5% 2 4 4 4 6% 42%	1996
October	1st to 10th	Night	17% 9% 4 5% 6% 3 5% 5% 5% 7% 35%	2160
	11th to 20th	Night	18% 16% 5% 7% 7% 4 4 4 5% 6% 23%	2160
	21st to end	Night	18% 16% 5% 8% 7% 4 6% 4 5% 6% 22%	2528
November	1st to 10th	Night	16% 14% 8% 11% 6% 3 4 5% 5% 5% 22%	2593
	11th to 20th	Night	14% 14% 8% 15% 9% 4 5% 4 5% 5% 18%	2660
	21st to end	Night	14% 14% 8% 16% 11% 5% 6% 4 4 5% 13%	2660
December	1st to 10th	Night	13% 13% 6% 16% 14% 6% 7% 5% 5% 4 10%	2821
	11th to 20th	Night	9% 14% 7% 15% 14% 8% 6% 5% 5% 5% 13%	3531
	21st to end	Night	11% 12% 6% 15% 12% 9% 7% 5% 5% 5% 13%	5236

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	68% 4 10% 12% 6%	1328
	11th to 20th	Day	62% 5% 9% 13% 11%	1295
	21st to end	Day	51% 5% 6% 23% 13% 2	1582
February	1st to 10th	Day	56% 5% 9% 18% 10% 2	1620
	11th to 20th	Day	63% 4 7% 14% 11% 1	1581
	21st to end	Day	54% 6% 7% 22% 10% 2	1340
March	1st to 10th	Day	59% 4 7% 19% 11% 1	1904
	11th to 20th	Day	62% 5% 7% 13% 10% 2	1980
	21st to end	Day	60% 4 8% 14% 12% 2	2178
April	1st to 10th	Day	68% 4 5% 11% 10% 2	2165
	11th to 20th	Day	57% 5% 7% 17% 13% 1	2312
	21st to end	Day	62% 2 7% 16% 12% 1	2340
May	1st to 10th	Day	63% 3 6% 15% 11% 1	2456
	11th to 20th	Day	58% 4 8% 18% 10% 1	2487
	21st to end	Day	57% 6% 11% 16% 9% 1	2919
June	1st to 10th	Day	60% 4 10% 16% 10% 1	2700
	11th to 20th	Day	53% 5% 11% 19% 11% 1	2700
	21st to end	Day	60% 4 11% 17% 7%	2700
July	1st to 10th	Day	54% 5% 15% 19% 7%	2625
	11th to 20th	Day	49% 6% 12% 24% 9%	2619
	21st to end	Day	55% 5% 12% 21% 6%	2743
August	1st to 10th	Day	54% 6% 15% 19% 5% 1	2335
	11th to 20th	Day	54% 4 17% 19% 6%	2304
	21st to end	Day	53% 6% 15% 22% 5%	2574
September	1st to 10th	Day	51% 4 13% 22% 10%	2174
	11th to 20th	Day	48% 3 13% 25% 10%	2034
	21st to end	Day	54% 5% 10% 21% 9% 1	1963
October	1st to 10th	Day	52% 5% 13% 19% 9% 1	1800
	11th to 20th	Day	64% 4 12% 15% 4	1800
	21st to end	Day	69% 4 7% 14% 5% 1	1822
November	1st to 10th	Day	64% 6% 11% 13% 6%	1485
	11th to 20th	Day	68% 5% 10% 13% 4	1520
	21st to end	Day	71% 4 10% 11% 4	1520
December	1st to 10th	Day	73% 6% 9% 10% 2	1357
	11th to 20th	Day	70% 6% 9% 12% 4	1668
	21st to end	Day	67% 4 10% 13% 6%	2431
January	1st to 10th	Night	67% 5% 10% 15% 3	2838
	11th to 20th	Night	61% 6% 10% 14% 8%	2787
	21st to end	Night	53% 6% 7% 19% 13% 2	2771
February	1st to 10th	Night	54% 6% 9% 19% 10% 3	2340
	11th to 20th	Night	61% 6% 7% 17% 9% 1	2276
	21st to end	Night	54% 5% 7% 22% 10% 1	1911
March	1st to 10th	Night	60% 3 6% 19% 11% 1	2055
	11th to 20th	Night	60% 5% 6% 16% 11% 2	1980
	21st to end	Night	58% 4 9% 16% 11% 2	2178
April	1st to 10th	Night	63% 6% 6% 12% 12%	1792
	11th to 20th	Night	51% 5% 8% 20% 14% 2	1598
	21st to end	Night	54% 4 8% 20% 12% 2	1620
May	1st to 10th	Night	55% 4 8% 20% 10% 2	1504
	11th to 20th	Night	52% 3 10% 21% 12% 1	1417
	21st to end	Night	53% 6% 11% 20% 10% 1	1366
June	1st to 10th	Night	54% 3 12% 20% 10%	1260
	11th to 20th	Night	50% 3 14% 19% 13% 1	1260
	21st to end	Night	53% 6% 14% 18% 9% 1	1260
July	1st to 10th	Night	43% 7% 19% 25% 5% 1	1225
	11th to 20th	Night	42% 4 18% 27% 8% 1	1218
	21st to end	Night	45% 5% 17% 22% 10%	1315
August	1st to 10th	Night	42% 7% 23% 23% 5%	1576
	11th to 20th	Night	46% 6% 20% 21% 6%	1596
	21st to end	Night	44% 5% 15% 29% 7%	1782
September	1st to 10th	Night	45% 5% 14% 26% 9%	1786
	11th to 20th	Night	46% 5% 14% 24% 10%	1923
	21st to end	Night	43% 5% 13% 26% 12% 1	1996
October	1st to 10th	Night	49% 6% 12% 22% 9% 2	2160
	11th to 20th	Night	59% 6% 12% 17% 6%	2160
	21st to end	Night	62% 6% 10% 16% 6% 1	2528
November	1st to 10th	Night	61% 7% 11% 15% 6%	2593
	11th to 20th	Night	66% 5% 10% 13% 5%	2660
	21st to end	Night	70% 6% 10% 11% 2 1	2660
December	1st to 10th	Night	72% 6% 8% 11% 3	2821
	11th to 20th	Night	71% 4 6% 14% 5%	3532
	21st to end	Night	71% 3 10% 12% 4	5236

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	28% 22% 31% 14% 3 1	180
	11th to 20th	Day	30% 26% 24% 15% 5%	170
	21st to end	Day	16% 28% 38% 12% 6%	214
February	1st to 10th	Day	19% 31% 31% 13% 5% 1	340
	11th to 20th	Day	25% 30% 29% 11% 5% 1	336
	21st to end	Day	18% 27% 33% 14% 6% 1	284
March	1st to 10th	Day	27% 25% 33% 10% 4 1	420
	11th to 20th	Day	26% 24% 30% 12% 6% 1	420
	21st to end	Day	28% 24% 33% 9% 4 2	462
April	1st to 10th	Day	35% 25% 26% 10% 3 1	420
	11th to 20th	Day	29% 25% 29% 12% 4 1	412
	21st to end	Day	30% 20% 30% 15% 2 2	420
May	1st to 10th	Day	32% 21% 28% 12% 6% 1	539
	11th to 20th	Day	32% 19% 26% 15% 6% 1	624
	21st to end	Day	34% 21% 26% 13% 4 1	680
June	1st to 10th	Day	32% 16% 30% 17% 4 1	630
	11th to 20th	Day	29% 16% 27% 18% 9% 1	630
	21st to end	Day	28% 16% 27% 20% 6% 2	630
July	1st to 10th	Day	22% 14% 35% 18% 9% 1	620
	11th to 20th	Day	17% 16% 35% 24% 7% 1	618
	21st to end	Day	21% 10% 31% 26% 9% 2	685
August	1st to 10th	Day	21% 15% 34% 21% 8% 1	468
	11th to 20th	Day	21% 13% 33% 23% 8% 2	439
	21st to end	Day	20% 17% 35% 17% 9% 2	495
September	1st to 10th	Day	27% 17% 31% 17% 6% 2	450
	11th to 20th	Day	31% 18% 31% 14% 2 4	450
	21st to end	Day	28% 24% 29% 12% 5% 1	441
October	1st to 10th	Day	24% 25% 29% 11% 9% 2	360
	11th to 20th	Day	31% 24% 23% 12% 8% 1	360
	21st to end	Day	35% 23% 21% 14% 6% 1	396
November	1st to 10th	Day	31% 25% 28% 13% 3 1	365
	11th to 20th	Day	28% 24% 29% 14% 3 2	370
	21st to end	Day	31% 25% 29% 11% 3 2	370
December	1st to 10th	Day	27% 24% 31% 12% 4 2	207
	11th to 20th	Day	28% 31% 29% 11% 1	180
	21st to end	Day	31% 27% 28% 13% 2	198
January	1st to 10th	Night	22% 22% 35% 16% 4 1	850
	11th to 20th	Night	24% 24% 32% 16% 5%	829
	21st to end	Night	16% 28% 31% 18% 7% 1	809
February	1st to 10th	Night	17% 28% 33% 15% 6% 1	720
	11th to 20th	Night	24% 26% 29% 16% 5% 1	703
	21st to end	Night	17% 27% 32% 16% 6% 2	592
March	1st to 10th	Night	22% 23% 34% 14% 7% 1	720
	11th to 20th	Night	24% 24% 28% 16% 6% 1	720
	21st to end	Night	23% 21% 31% 18% 6% 1	792
April	1st to 10th	Night	30% 19% 31% 15% 5%	576
	11th to 20th	Night	25% 22% 28% 18% 7% 1	534
	21st to end	Night	29% 16% 27% 19% 8% 1	540
May	1st to 10th	Night	29% 13% 27% 22% 9% 1	540
	11th to 20th	Night	29% 14% 24% 22% 9% 2	532
	21st to end	Night	23% 18% 33% 20% 5% 1	398
June	1st to 10th	Night	24% 11% 27% 29% 8% 1	360
	11th to 20th	Night	26% 10% 27% 28% 10%	360
	21st to end	Night	28% 10% 23% 28% 10% 1	360
July	1st to 10th	Night	18% 8% 37% 22% 14% 1	350
	11th to 20th	Night	16% 7% 33% 35% 9%	348
	21st to end	Night	17% 9% 26% 36% 12%	409
August	1st to 10th	Night	18% 7% 30% 32% 12%	538
	11th to 20th	Night	19% 8% 27% 32% 13% 1	532
	21st to end	Night	18% 11% 30% 26% 14% 2	594
September	1st to 10th	Night	21% 16% 29% 25% 9%	540
	11th to 20th	Night	24% 14% 31% 21% 9% 1	663
	21st to end	Night	24% 18% 30% 21% 6%	720
October	1st to 10th	Night	25% 18% 30% 19% 7% 1	720
	11th to 20th	Night	29% 19% 26% 16% 9% 1	720
	21st to end	Night	30% 22% 24% 16% 7% 1	801
November	1st to 10th	Night	33% 21% 27% 15% 4	830
	11th to 20th	Night	28% 24% 27% 14% 5% 1	850
	21st to end	Night	28% 24% 29% 14% 5%	850
December	1st to 10th	Night	26% 26% 30% 12% 5% 1	850
	11th to 20th	Night	29% 26% 29% 13% 4 1	850
	21st to end	Night	27% 24% 26% 17% 4 2	935

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