Montmagny
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Montmagny clear sky chart from 2005-11-06 to 2024-09-29.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 32%	101115
	Night	17% 12% 4 9% 5% 5% 5% 4 5% 6% 29%	97117
Transparency	Day	50% 8% 13% 20% 8% 1	100871
	Night	55% 7% 12% 17% 8% 1	96983
Seeing	Day	24% 15% 30% 21% 8% 2	15320
	Night	25% 12% 31% 24% 7% 1	23615

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	11% 17% 6% 12% 6% 6% 5% 4 7% 6% 20%	2486
	11th to 20th	Day	11% 12% 5% 10% 6% 5% 5% 4 6% 7% 28%	2520
	21st to end	Day	9% 8% 4 11% 6% 6% 5% 4 5% 8% 32%	2772
February	1st to 10th	Day	11% 12% 5% 10% 6% 5% 6% 4 7% 7% 27%	1549
	11th to 20th	Day	13% 13% 5% 12% 6% 6% 4 4 5% 6% 28%	1796
	21st to end	Day	12% 12% 5% 9% 6% 6% 5% 4 5% 6% 31%	1570
March	1st to 10th	Day	17% 12% 4 9% 5% 5% 5% 4 5% 6% 28%	3116
	11th to 20th	Day	15% 17% 4 9% 6% 5% 4 3 5% 6% 26%	3370
	21st to end	Day	13% 15% 4 8% 5% 4 3 3 4 5% 36%	3992
April	1st to 10th	Day	20% 12% 4 9% 5% 4 3 3 5% 5% 30%	2280
	11th to 20th	Day	18% 9% 2 6% 4 3 4 3 4 5% 40%	2377
	21st to end	Day	22% 8% 3 7% 5% 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	17% 8% 3 7% 5% 4 4 3 4 7% 36%	4138
	11th to 20th	Day	17% 8% 2 7% 5% 5% 6% 4 6% 8% 33%	4398
	21st to end	Day	15% 7% 3 8% 6% 5% 6% 4 6% 8% 32%	5028
June	1st to 10th	Day	17% 7% 2 7% 5% 5% 5% 6% 7% 8% 30%	2850
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 4 7% 8% 36%	2850
	21st to end	Day	18% 9% 3 7% 6% 5% 4 4 7% 8% 29%	2850
July	1st to 10th	Day	13% 6% 3 8% 5% 6% 5% 5% 7% 8% 33%	4664
	11th to 20th	Day	13% 5% 3 7% 5% 5% 6% 4 7% 9% 37%	4440
	21st to end	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	4814
August	1st to 10th	Day	13% 6% 2 7% 5% 5% 6% 6% 8% 10% 32%	4343
	11th to 20th	Day	16% 7% 3 8% 6% 5% 5% 4 7% 9% 31%	4045
	21st to end	Day	17% 6% 2 6% 4 4 4 3 6% 7% 41%	4414
September	1st to 10th	Day	15% 5% 2 5% 5% 5% 5% 3 6% 9% 40%	2275
	11th to 20th	Day	16% 6% 2 6% 4 3 3 2 5% 6% 49%	2090
	21st to end	Day	19% 6% 3 6% 3 4 4 3 5% 7% 40%	2070
October	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 5% 8% 36%	1978
	11th to 20th	Day	21% 10% 3 8% 6% 5% 5% 4 6% 6% 26%	1652
	21st to end	Day	26% 11% 3 8% 5% 4 4 3 5% 6% 24%	1782
November	1st to 10th	Day	16% 11% 3 8% 5% 5% 5% 4 5% 7% 30%	1671
	11th to 20th	Day	18% 13% 4 10% 6% 5% 4 4 6% 5% 26%	1672
	21st to end	Day	19% 16% 5% 9% 6% 4 4 4 6% 5% 22%	1364
December	1st to 10th	Day	21% 16% 5% 11% 6% 5% 4 3 4 5% 19%	1330
	11th to 20th	Day	19% 13% 4 9% 6% 5% 5% 3 5% 6% 25%	1668
	21st to end	Day	21% 14% 4 9% 5% 4 5% 3 5% 6% 24%	2431
January	1st to 10th	Night	13% 17% 6% 14% 8% 5% 5% 3 4 5% 20%	4457
	11th to 20th	Night	12% 15% 5% 12% 7% 6% 5% 5% 5% 6% 23%	4440
	21st to end	Night	10% 12% 5% 11% 7% 5% 6% 5% 7% 7% 25%	4884
February	1st to 10th	Night	10% 14% 4 10% 6% 6% 5% 5% 5% 7% 26%	2629
	11th to 20th	Night	12% 15% 5% 11% 7% 5% 4 4 6% 5% 26%	2268
	21st to end	Night	14% 15% 5% 11% 5% 4 4 3 4 7% 28%	1884
March	1st to 10th	Night	20% 15% 4 8% 5% 4 6% 3 4 6% 26%	3724
	11th to 20th	Night	14% 18% 5% 11% 7% 6% 5% 4 4 5% 22%	3588
	21st to end	Night	17% 15% 5% 8% 5% 3 3 3 4 5% 30%	3636
April	1st to 10th	Night	22% 14% 4 8% 4 4 3 3 4 5% 29%	1900
	11th to 20th	Night	20% 7% 3 8% 4 5% 4 4 5% 8% 33%	1750
	21st to end	Night	23% 10% 3 6% 5% 4 3 3 3 5% 34%	1710
May	1st to 10th	Night	22% 8% 2 7% 4 4 5% 3 5% 6% 35%	2816
	11th to 20th	Night	20% 9% 3 7% 5% 6% 5% 4 5% 6% 30%	2495
	21st to end	Night	17% 6% 3 5% 5% 5% 6% 4 7% 8% 35%	2536
June	1st to 10th	Night	20% 9% 2 7% 5% 6% 6% 5% 5% 8% 27%	1330
	11th to 20th	Night	15% 8% 4 6% 4 4 4 4 6% 8% 39%	1330
	21st to end	Night	21% 9% 3 9% 5% 4 4 3 5% 6% 31%	1330
July	1st to 10th	Night	11% 7% 3 9% 5% 6% 6% 5% 7% 8% 33%	2298
	11th to 20th	Night	18% 6% 2 7% 5% 5% 4 4 7% 8% 33%	2520
	21st to end	Night	12% 6% 3 7% 5% 5% 4 3 5% 8% 41%	2739
August	1st to 10th	Night	17% 8% 3 7% 5% 4 4 3 5% 7% 35%	2555
	11th to 20th	Night	17% 7% 3 9% 6% 6% 5% 4 7% 8% 28%	2782
	21st to end	Night	15% 7% 3 8% 6% 5% 5% 4 5% 6% 37%	3240
September	1st to 10th	Night	17% 7% 2 7% 4 4 4 3 5% 8% 39%	1905
	11th to 20th	Night	17% 8% 2 5% 4 3 4 3 5% 6% 43%	2090
	21st to end	Night	19% 8% 3 7% 3 3 4 4 5% 6% 39%	2078
October	1st to 10th	Night	18% 9% 3 7% 4 3 4 4 5% 7% 38%	1981
	11th to 20th	Night	25% 9% 3 8% 4 4 4 3 5% 6% 29%	2304
	21st to end	Night	23% 10% 3 8% 5% 4 4 3 5% 7% 27%	2574
November	1st to 10th	Night	17% 12% 3 9% 5% 5% 4 4 5% 6% 29%	2407
	11th to 20th	Night	18% 11% 4 9% 5% 5% 5% 3 5% 6% 29%	2508
	21st to end	Night	19% 17% 4 9% 5% 4 4 4 5% 5% 25%	2812
December	1st to 10th	Night	20% 15% 6% 10% 7% 5% 5% 4 5% 5% 18%	2850
	11th to 20th	Night	18% 15% 4 10% 7% 5% 5% 3 5% 5% 23%	3531
	21st to end	Night	21% 17% 4 9% 5% 4 4 2 3 4 26%	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	60% 10% 12% 14% 4	2487
	11th to 20th	Day	54% 11% 9% 19% 5% 1	2520
	21st to end	Day	50% 8% 12% 22% 8%	2772
February	1st to 10th	Day	57% 7% 10% 16% 9% 1	1549
	11th to 20th	Day	59% 5% 10% 16% 9% 1	1805
	21st to end	Day	55% 6% 8% 19% 10% 2	1570
March	1st to 10th	Day	57% 6% 12% 15% 9% 2	3119
	11th to 20th	Day	58% 7% 13% 15% 6% 1	3370
	21st to end	Day	52% 4 9% 20% 12% 4	3992
April	1st to 10th	Day	57% 4 11% 15% 10% 2	2280
	11th to 20th	Day	47% 6% 9% 23% 13% 2	2377
	21st to end	Day	52% 6% 10% 17% 12% 3	2470
May	1st to 10th	Day	48% 7% 13% 18% 14% 1	4152
	11th to 20th	Day	48% 8% 16% 20% 7% 1	4402
	21st to end	Day	49% 9% 10% 21% 11%	5028
June	1st to 10th	Day	49% 9% 13% 21% 8% 1	2850
	11th to 20th	Day	46% 8% 13% 22% 10% 1	2850
	21st to end	Day	54% 8% 11% 19% 9%	2850
July	1st to 10th	Day	46% 9% 14% 23% 7%	4592
	11th to 20th	Day	42% 9% 19% 25% 5%	4365
	21st to end	Day	39% 9% 19% 24% 8%	4661
August	1st to 10th	Day	44% 11% 19% 21% 5%	4329
	11th to 20th	Day	48% 11% 20% 17% 5%	4084
	21st to end	Day	43% 9% 17% 19% 12%	4414
September	1st to 10th	Day	41% 7% 14% 26% 11% 1	2275
	11th to 20th	Day	39% 5% 15% 29% 12% 1	2090
	21st to end	Day	45% 6% 13% 25% 11%	2070
October	1st to 10th	Day	48% 6% 11% 27% 9%	1978
	11th to 20th	Day	59% 6% 16% 15% 3	1652
	21st to end	Day	63% 5% 11% 16% 5% 1	1782
November	1st to 10th	Day	55% 7% 13% 18% 8%	1671
	11th to 20th	Day	60% 6% 10% 18% 6%	1672
	21st to end	Day	63% 7% 13% 14% 3	1364
December	1st to 10th	Day	67% 6% 10% 13% 5%	1330
	11th to 20th	Day	61% 6% 9% 18% 7%	1668
	21st to end	Day	61% 7% 12% 11% 6% 2	2431
January	1st to 10th	Night	65% 8% 10% 11% 5%	4457
	11th to 20th	Night	61% 8% 10% 16% 5%	4440
	21st to end	Night	54% 10% 10% 15% 10% 1	4884
February	1st to 10th	Night	57% 6% 9% 16% 10% 1	2629
	11th to 20th	Night	60% 6% 10% 13% 10%	2270
	21st to end	Night	57% 5% 8% 17% 12% 1	1884
March	1st to 10th	Night	60% 6% 10% 15% 8% 1	3734
	11th to 20th	Night	63% 8% 10% 11% 6% 1	3589
	21st to end	Night	58% 4 7% 21% 9% 2	3636
April	1st to 10th	Night	59% 4 7% 14% 13% 3	1900
	11th to 20th	Night	50% 6% 9% 22% 12% 2	1750
	21st to end	Night	55% 5% 8% 18% 14% 2	1710
May	1st to 10th	Night	49% 6% 12% 20% 11% 1	2822
	11th to 20th	Night	52% 7% 12% 17% 11% 1	2496
	21st to end	Night	44% 8% 14% 19% 13% 1	2537
June	1st to 10th	Night	55% 8% 11% 19% 7% 1	1330
	11th to 20th	Night	44% 8% 12% 22% 11% 3	1330
	21st to end	Night	55% 8% 12% 16% 10%	1330
July	1st to 10th	Night	46% 9% 19% 21% 5%	2261
	11th to 20th	Night	46% 9% 20% 21% 4 1	2472
	21st to end	Night	40% 9% 23% 20% 8%	2651
August	1st to 10th	Night	49% 7% 16% 24% 4	2545
	11th to 20th	Night	51% 11% 17% 16% 5%	2809
	21st to end	Night	46% 8% 13% 21% 12%	3240
September	1st to 10th	Night	45% 7% 13% 22% 11% 1	1905
	11th to 20th	Night	43% 6% 17% 25% 9%	2090
	21st to end	Night	46% 6% 11% 25% 11%	2078
October	1st to 10th	Night	48% 6% 11% 25% 10% 1	1981
	11th to 20th	Night	57% 6% 13% 18% 5%	2304
	21st to end	Night	58% 6% 13% 16% 7%	2574
November	1st to 10th	Night	56% 7% 12% 18% 6%	2407
	11th to 20th	Night	57% 6% 12% 17% 8%	2508
	21st to end	Night	62% 6% 11% 14% 5% 1	2812
December	1st to 10th	Night	68% 6% 11% 11% 4	2850
	11th to 20th	Night	63% 5% 9% 13% 9%	3532
	21st to end	Night	64% 4 10% 14% 7% 1	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	26% 27% 28% 14% 5% 1	180
	11th to 20th	Day	33% 22% 29% 12% 3 1	180
	21st to end	Day	16% 27% 34% 17% 5% 1	198
February	1st to 10th	Day	25% 23% 36% 11% 4 1	209
	11th to 20th	Day	22% 27% 34% 15% 2	431
	21st to end	Day	25% 21% 30% 20% 3	382
March	1st to 10th	Day	27% 19% 28% 20% 4 1	460
	11th to 20th	Day	25% 17% 31% 20% 6% 1	460
	21st to end	Day	25% 17% 29% 19% 8% 3	506
April	1st to 10th	Day	31% 17% 30% 15% 7% 1	460
	11th to 20th	Day	29% 17% 27% 19% 6% 1	452
	21st to end	Day	25% 20% 31% 17% 5% 2	460
May	1st to 10th	Day	28% 13% 34% 18% 5% 2	463
	11th to 20th	Day	23% 12% 29% 26% 9% 1	487
	21st to end	Day	21% 18% 36% 18% 6%	642
June	1st to 10th	Day	22% 13% 31% 24% 9%	680
	11th to 20th	Day	20% 12% 30% 25% 13% 1	680
	21st to end	Day	23% 9% 30% 25% 11% 1	680
July	1st to 10th	Day	17% 13% 31% 28% 10% 1	616
	11th to 20th	Day	17% 13% 33% 26% 10% 2	484
	21st to end	Day	17% 10% 33% 29% 11% 1	532
August	1st to 10th	Day	16% 12% 32% 23% 14% 2	486
	11th to 20th	Day	17% 8% 27% 30% 15% 2	479
	21st to end	Day	20% 13% 24% 24% 13% 6%	539
September	1st to 10th	Day	20% 12% 29% 26% 10% 3	490
	11th to 20th	Day	21% 10% 30% 26% 11% 2	490
	21st to end	Day	22% 12% 27% 24% 10% 5%	483
October	1st to 10th	Day	23% 15% 31% 20% 10% 2	448
	11th to 20th	Day	30% 15% 27% 19% 9% 1	360
	21st to end	Day	35% 17% 30% 13% 5% 1	396
November	1st to 10th	Day	30% 17% 33% 17% 3 1	365
	11th to 20th	Day	27% 20% 27% 19% 7% 1	370
	21st to end	Day	29% 20% 32% 17% 1	214
December	1st to 10th	Day	31% 15% 29% 21% 4 1	180
	11th to 20th	Day	34% 22% 27% 11% 4 2	180
	21st to end	Day	40% 18% 27% 14% 1	198
January	1st to 10th	Night	27% 17% 33% 18% 4	767
	11th to 20th	Night	25% 19% 33% 19% 4	760
	21st to end	Night	18% 17% 35% 24% 5%	836
February	1st to 10th	Night	18% 17% 37% 22% 6%	760
	11th to 20th	Night	23% 18% 39% 14% 5% 1	743
	21st to end	Night	24% 15% 32% 25% 4	628
March	1st to 10th	Night	24% 12% 36% 23% 5%	760
	11th to 20th	Night	23% 13% 36% 22% 6% 1	760
	21st to end	Night	24% 12% 32% 25% 7% 1	836
April	1st to 10th	Night	31% 13% 27% 23% 6%	760
	11th to 20th	Night	27% 11% 32% 23% 7% 1	626
	21st to end	Night	30% 11% 27% 24% 8%	570
May	1st to 10th	Night	28% 10% 29% 25% 8%	565
	11th to 20th	Night	25% 6% 28% 30% 10% 1	374
	21st to end	Night	27% 7% 35% 25% 7%	411
June	1st to 10th	Night	25% 6% 29% 34% 7%	380
	11th to 20th	Night	17% 5% 27% 36% 15%	380
	21st to end	Night	25% 7% 29% 30% 9% 1	380
July	1st to 10th	Night	19% 6% 32% 32% 10%	370
	11th to 20th	Night	18% 5% 29% 33% 13% 1	368
	21st to end	Night	14% 5% 31% 38% 11% 1	416
August	1st to 10th	Night	16% 4 25% 39% 14% 1	401
	11th to 20th	Night	17% 7% 24% 36% 14% 1	562
	21st to end	Night	16% 7% 30% 31% 13% 2	691
September	1st to 10th	Night	22% 6% 29% 32% 10% 1	760
	11th to 20th	Night	21% 9% 30% 30% 10% 1	760
	21st to end	Night	22% 10% 27% 29% 12% 1	756
October	1st to 10th	Night	24% 12% 31% 25% 7% 1	720
	11th to 20th	Night	32% 10% 27% 22% 8%	720
	21st to end	Night	28% 15% 32% 19% 6%	792
November	1st to 10th	Night	28% 16% 28% 23% 5% 1	740
	11th to 20th	Night	28% 16% 28% 21% 6% 1	778
	21st to end	Night	28% 15% 33% 19% 4 1	850
December	1st to 10th	Night	31% 15% 31% 18% 5%	850
	11th to 20th	Night	28% 19% 32% 16% 5% 1	850
	21st to end	Night	33% 19% 27% 18% 3 1	935

Page generated at 2024-09-26 09:52:23. Version ac07

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