Morrisburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morrisburg clear sky chart from 2005-11-06 to 2026-06-16.

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	17% 11% 4 8% 5% 5% 4 4 5% 6% 31%	138018
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 29%	133986
Transparency	Day	53% 5% 11% 21% 9% 1	141472
	Night	57% 5% 10% 18% 9% 1	138621
Seeing	Day	23% 17% 30% 19% 8% 2	16525
	Night	24% 14% 30% 24% 8% 1	25635

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	16% 21% 6% 13% 6% 5% 4 3 4 5% 17%	4661
	11th to 20th	Day	12% 19% 8% 15% 7% 5% 4 4 4 4 18%	4650
	21st to end	Day	11% 17% 7% 14% 9% 8% 5% 3 4 4 18%	5304
February	1st to 10th	Day	17% 16% 5% 11% 7% 5% 4 3 5% 5% 23%	1890
	11th to 20th	Day	16% 16% 6% 11% 7% 4 4 4 4 5% 25%	1890
	21st to end	Day	19% 17% 5% 11% 7% 4 3 4 4 4 22%	1730
March	1st to 10th	Day	19% 14% 5% 10% 5% 4 5% 3 4 5% 26%	4576
	11th to 20th	Day	12% 14% 4 9% 5% 5% 5% 4 5% 6% 30%	5012
	21st to end	Day	20% 10% 3 8% 5% 4 3 3 3 4 36%	5956
April	1st to 10th	Day	22% 14% 3 7% 5% 4 3 3 4 4 31%	2520
	11th to 20th	Day	23% 11% 3 7% 4 4 3 2 3 4 36%	2494
	21st to end	Day	23% 10% 3 7% 4 4 4 4 5% 5% 33%	2628
May	1st to 10th	Day	24% 9% 3 9% 5% 5% 4 4 5% 7% 25%	8237
	11th to 20th	Day	18% 9% 3 9% 5% 4 4 3 5% 7% 33%	8221
	21st to end	Day	22% 9% 3 6% 3 4 4 3 5% 6% 34%	9060
June	1st to 10th	Day	22% 7% 3 6% 5% 4 5% 4 6% 7% 31%	2940
	11th to 20th	Day	15% 7% 2 6% 5% 5% 4 4 6% 8% 38%	2870
	21st to end	Day	21% 7% 2 6% 5% 5% 5% 4 6% 7% 32%	2800
July	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 5% 6% 9% 34%	6360
	11th to 20th	Day	11% 6% 2 6% 4 6% 5% 4 6% 8% 42%	6360
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 7% 9% 45%	6926
August	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 5% 8% 35%	4534
	11th to 20th	Day	16% 7% 2 6% 4 4 4 4 6% 8% 40%	4052
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 6% 9% 39%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 4 6% 8% 43%	2400
	11th to 20th	Day	14% 4 2 5% 4 4 4 3 5% 7% 48%	2375
	21st to end	Day	18% 6% 3 6% 4 3 4 4 6% 7% 38%	2175
October	1st to 10th	Day	20% 7% 2 6% 4 4 4 4 5% 7% 37%	2000
	11th to 20th	Day	20% 10% 3 8% 5% 6% 5% 3 4 7% 29%	2000
	21st to end	Day	26% 10% 3 7% 5% 4 4 2 4 6% 28%	2017
November	1st to 10th	Day	17% 11% 4 7% 6% 5% 4 4 5% 7% 31%	1851
	11th to 20th	Day	17% 14% 3 8% 5% 4 4 4 5% 6% 29%	1743
	21st to end	Day	22% 16% 4 9% 6% 4 5% 3 4 5% 20%	1680
December	1st to 10th	Day	21% 22% 5% 10% 5% 4 4 4 4 5% 14%	2680
	11th to 20th	Day	18% 18% 5% 12% 6% 4 4 3 4 4 23%	3066
	21st to end	Day	22% 16% 4 12% 6% 4 5% 3 3 4 21%	4048
January	1st to 10th	Night	15% 22% 7% 13% 6% 4 3 3 4 4 19%	8234
	11th to 20th	Night	13% 19% 8% 17% 7% 6% 5% 3 4 4 14%	8235
	21st to end	Night	14% 16% 6% 12% 8% 6% 5% 3 4 5% 21%	8862
February	1st to 10th	Night	16% 16% 5% 13% 7% 6% 4 3 4 5% 21%	2730
	11th to 20th	Night	15% 15% 5% 12% 6% 4 4 3 4 5% 26%	2615
	21st to end	Night	17% 15% 4 11% 6% 4 4 3 4 5% 27%	2076
March	1st to 10th	Night	22% 14% 4 9% 5% 4 3 3 4 4 29%	5484
	11th to 20th	Night	16% 14% 4 7% 4 4 5% 3 5% 7% 31%	5165
	21st to end	Night	19% 12% 3 8% 5% 4 3 3 4 5% 33%	5218
April	1st to 10th	Night	22% 10% 4 9% 4 4 5% 3 5% 4 31%	2100
	11th to 20th	Night	21% 10% 3 7% 5% 4 4 2 5% 6% 33%	2075
	21st to end	Night	22% 9% 2 7% 3 4 4 3 4 5% 36%	2007
May	1st to 10th	Night	23% 10% 4 9% 4 5% 5% 4 6% 7% 22%	4660
	11th to 20th	Night	19% 9% 3 8% 4 5% 4 3 5% 6% 34%	4639
	21st to end	Night	19% 8% 3 7% 4 5% 5% 4 6% 8% 33%	5114
June	1st to 10th	Night	18% 6% 3 7% 4 6% 6% 4 7% 8% 31%	1680
	11th to 20th	Night	16% 6% 2 7% 5% 4 4 4 5% 8% 39%	1640
	21st to end	Night	20% 7% 2 7% 4 4 4 4 6% 7% 34%	1600
July	1st to 10th	Night	14% 6% 2 7% 5% 4 5% 4 7% 10% 35%	3600
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 6% 7% 43%	3600
	21st to end	Night	10% 5% 2 6% 4 4 5% 5% 6% 7% 44%	3926
August	1st to 10th	Night	15% 8% 3 6% 4 4 4 3 6% 8% 39%	2612
	11th to 20th	Night	17% 6% 3 7% 4 4 4 3 5% 6% 40%	2964
	21st to end	Night	13% 5% 2 7% 5% 5% 5% 4 6% 8% 41%	3586
September	1st to 10th	Night	15% 6% 2 6% 4 4 4 4 5% 5% 45%	2000
	11th to 20th	Night	14% 4 1 4 4 3 3 3 5% 8% 50%	2025
	21st to end	Night	16% 6% 3 6% 5% 4 4 4 5% 6% 42%	2220
October	1st to 10th	Night	19% 8% 3 6% 4 4 4 4 5% 7% 37%	2400
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 35%	2400
	21st to end	Night	26% 9% 3 8% 4 4 4 3 5% 6% 28%	2822
November	1st to 10th	Night	20% 11% 3 7% 4 4 4 3 4 5% 34%	2667
	11th to 20th	Night	18% 12% 4 8% 4 4 4 4 4 6% 31%	2872
	21st to end	Night	22% 15% 4 9% 5% 4 4 3 4 5% 24%	2940
December	1st to 10th	Night	20% 19% 6% 12% 6% 5% 4 3 4 5% 15%	4720
	11th to 20th	Night	23% 16% 4 10% 5% 4 4 3 3 4 24%	5348
	21st to end	Night	26% 16% 4 11% 4 4 4 4 4 4 19%	7150

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	71% 6% 9% 11% 3	4662
	11th to 20th	Day	73% 4 8% 7% 8% 1	4680
	21st to end	Day	71% 5% 8% 8% 8%	5304
February	1st to 10th	Day	66% 3 7% 18% 5% 1	1890
	11th to 20th	Day	63% 5% 10% 14% 7% 1	1899
	21st to end	Day	66% 5% 9% 12% 7% 1	1730
March	1st to 10th	Day	62% 5% 9% 14% 8% 3	4579
	11th to 20th	Day	54% 5% 15% 14% 9% 1	5012
	21st to end	Day	54% 3 6% 18% 17% 2	5956
April	1st to 10th	Day	57% 3 7% 19% 11% 3	2520
	11th to 20th	Day	53% 4 7% 19% 15% 2	2494
	21st to end	Day	53% 4 8% 17% 14% 3	2628
May	1st to 10th	Day	58% 5% 9% 19% 9% 1	8249
	11th to 20th	Day	51% 7% 11% 21% 10% 1	8225
	21st to end	Day	51% 6% 9% 24% 10% 1	9061
June	1st to 10th	Day	50% 7% 10% 20% 13% 1	2940
	11th to 20th	Day	44% 6% 11% 25% 12% 2	2870
	21st to end	Day	49% 8% 10% 21% 11% 1	2800
July	1st to 10th	Day	43% 6% 13% 27% 10%	6290
	11th to 20th	Day	38% 7% 14% 28% 13%	6285
	21st to end	Day	35% 7% 13% 38% 8%	6728
August	1st to 10th	Day	47% 6% 15% 23% 9%	4520
	11th to 20th	Day	42% 7% 16% 28% 8%	4091
	21st to end	Day	42% 6% 16% 25% 11%	4312
September	1st to 10th	Day	39% 6% 13% 28% 13%	2400
	11th to 20th	Day	36% 5% 12% 33% 14% 1	2375
	21st to end	Day	44% 6% 13% 26% 11%	2175
October	1st to 10th	Day	46% 4 12% 29% 10%	3260
	11th to 20th	Day	49% 5% 15% 24% 7% 1	3240
	21st to end	Day	48% 5% 16% 23% 7%	3229
November	1st to 10th	Day	53% 6% 12% 21% 7% 1	1851
	11th to 20th	Day	57% 6% 11% 15% 9% 2	1743
	21st to end	Day	68% 5% 11% 12% 4	1680
December	1st to 10th	Day	73% 6% 9% 10% 1	2680
	11th to 20th	Day	67% 5% 8% 14% 6%	3066
	21st to end	Day	69% 4 8% 15% 4	4048
January	1st to 10th	Night	71% 5% 10% 10% 3	8234
	11th to 20th	Night	76% 4 6% 8% 5%	8280
	21st to end	Night	69% 5% 6% 11% 8%	8862
February	1st to 10th	Night	68% 4 8% 14% 5%	2730
	11th to 20th	Night	62% 5% 9% 19% 6%	2617
	21st to end	Night	62% 4 8% 16% 9% 1	2076
March	1st to 10th	Night	61% 4 7% 16% 10% 2	5494
	11th to 20th	Night	52% 5% 18% 14% 8% 3	5166
	21st to end	Night	57% 3 7% 20% 11% 2	5218
April	1st to 10th	Night	56% 4 8% 19% 11% 1	2100
	11th to 20th	Night	53% 5% 8% 18% 14% 1	2075
	21st to end	Night	51% 4 9% 18% 15% 3	2007
May	1st to 10th	Night	59% 6% 10% 17% 7% 1	4666
	11th to 20th	Night	51% 5% 11% 20% 11% 1	4640
	21st to end	Night	49% 5% 11% 19% 14% 1	5115
June	1st to 10th	Night	50% 7% 11% 19% 12% 1	1680
	11th to 20th	Night	43% 6% 13% 20% 17% 2	1640
	21st to end	Night	49% 7% 12% 18% 13% 1	1600
July	1st to 10th	Night	43% 5% 16% 22% 13% 1	3560
	11th to 20th	Night	40% 5% 14% 29% 12% 1	3552
	21st to end	Night	37% 7% 12% 30% 14%	3809
August	1st to 10th	Night	44% 7% 15% 25% 10%	2602
	11th to 20th	Night	45% 6% 13% 27% 9% 1	2991
	21st to end	Night	40% 7% 14% 27% 11% 1	3586
September	1st to 10th	Night	40% 6% 10% 29% 13% 1	2000
	11th to 20th	Night	34% 5% 14% 33% 13% 1	2025
	21st to end	Night	43% 6% 11% 26% 13% 1	2220
October	1st to 10th	Night	44% 5% 13% 27% 10% 1	3920
	11th to 20th	Night	46% 4 15% 25% 10%	3899
	21st to end	Night	51% 5% 16% 20% 8%	4560
November	1st to 10th	Night	53% 4 12% 20% 9% 1	2667
	11th to 20th	Night	55% 6% 12% 17% 9% 2	2872
	21st to end	Night	64% 5% 12% 14% 5%	2940
December	1st to 10th	Night	74% 5% 9% 9% 2	4720
	11th to 20th	Night	67% 5% 7% 14% 7%	5348
	21st to end	Night	69% 4 7% 12% 7%	7150

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	30% 18% 32% 16% 4	220
	11th to 20th	Day	32% 22% 31% 10% 5%	220
	21st to end	Day	23% 20% 36% 16% 5%	275
February	1st to 10th	Day	31% 26% 31% 10% 3	330
	11th to 20th	Day	25% 29% 36% 10% 1	377
	21st to end	Day	31% 21% 34% 13% 2	446
March	1st to 10th	Day	26% 23% 32% 15% 4	540
	11th to 20th	Day	27% 22% 33% 15% 3 1	540
	21st to end	Day	32% 21% 28% 13% 5% 1	594
April	1st to 10th	Day	33% 19% 29% 15% 3 1	540
	11th to 20th	Day	32% 23% 21% 17% 5% 2	532
	21st to end	Day	31% 19% 31% 12% 7% 1	540
May	1st to 10th	Day	25% 19% 32% 16% 6% 1	543
	11th to 20th	Day	18% 19% 34% 17% 9% 2	567
	21st to end	Day	20% 18% 30% 22% 9% 1	617
June	1st to 10th	Day	25% 14% 29% 23% 8% 2	570
	11th to 20th	Day	16% 15% 35% 23% 8% 2	550
	21st to end	Day	23% 14% 34% 17% 11% 1	530
July	1st to 10th	Day	13% 9% 34% 28% 13% 2	525
	11th to 20th	Day	14% 10% 33% 29% 11% 3	524
	21st to end	Day	15% 8% 32% 30% 13% 2	576
August	1st to 10th	Day	15% 10% 25% 33% 14% 3	526
	11th to 20th	Day	15% 7% 27% 28% 16% 7%	519
	21st to end	Day	14% 10% 31% 24% 13% 6%	583
September	1st to 10th	Day	14% 12% 27% 26% 13% 8%	530
	11th to 20th	Day	11% 8% 23% 28% 18% 12%	530
	21st to end	Day	19% 12% 31% 20% 14% 4	530
October	1st to 10th	Day	22% 14% 27% 19% 13% 5%	530
	11th to 20th	Day	23% 20% 32% 18% 7% 1	530
	21st to end	Day	31% 18% 25% 21% 6%	481
November	1st to 10th	Day	26% 22% 28% 16% 7% 1	425
	11th to 20th	Day	27% 19% 33% 15% 6% 1	283
	21st to end	Day	31% 21% 33% 10% 4	220
December	1st to 10th	Day	30% 21% 29% 16% 4	220
	11th to 20th	Day	30% 31% 27% 9% 3	220
	21st to end	Day	33% 21% 29% 12% 4	242
January	1st to 10th	Night	28% 18% 32% 19% 3	840
	11th to 20th	Night	32% 16% 28% 19% 4	840
	21st to end	Night	22% 16% 34% 24% 5%	924
February	1st to 10th	Night	23% 18% 33% 22% 3	840
	11th to 20th	Night	24% 19% 36% 18% 3	823
	21st to end	Night	26% 18% 31% 23% 2	692
March	1st to 10th	Night	26% 16% 32% 22% 4	840
	11th to 20th	Night	28% 19% 30% 19% 3	840
	21st to end	Night	26% 16% 28% 24% 6%	924
April	1st to 10th	Night	29% 14% 30% 23% 4	840
	11th to 20th	Night	27% 18% 29% 19% 6%	831
	21st to end	Night	27% 14% 30% 22% 7% 1	747
May	1st to 10th	Night	25% 11% 30% 26% 7% 1	420
	11th to 20th	Night	21% 11% 35% 26% 7%	414
	21st to end	Night	16% 9% 40% 25% 10%	455
June	1st to 10th	Night	20% 7% 31% 36% 6%	420
	11th to 20th	Night	18% 12% 29% 29% 12% 1	410
	21st to end	Night	21% 7% 30% 30% 12% 1	400
July	1st to 10th	Night	9% 6% 31% 40% 13% 1	390
	11th to 20th	Night	16% 5% 26% 37% 16% 1	388
	21st to end	Night	11% 5% 29% 45% 9% 1	438
August	1st to 10th	Night	16% 4 21% 43% 16% 1	411
	11th to 20th	Night	15% 5% 21% 37% 21% 1	644
	21st to end	Night	15% 5% 29% 31% 16% 2	880
September	1st to 10th	Night	15% 8% 28% 32% 16% 1	800
	11th to 20th	Night	16% 6% 21% 31% 22% 4	800
	21st to end	Night	18% 9% 28% 25% 20% 2	800
October	1st to 10th	Night	23% 10% 28% 23% 15% 1	800
	11th to 20th	Night	24% 13% 31% 24% 8%	800
	21st to end	Night	30% 14% 29% 23% 5%	880
November	1st to 10th	Night	28% 17% 27% 21% 6%	820
	11th to 20th	Night	24% 19% 30% 19% 8%	840
	21st to end	Night	29% 19% 28% 19% 5%	840
December	1st to 10th	Night	30% 18% 30% 18% 3	840
	11th to 20th	Night	29% 20% 32% 15% 4 1	840
	21st to end	Night	34% 16% 28% 18% 4	924

Page generated at 2026-06-13 02:31:44. Version ac07

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