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 2025-02-06.

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% 3 8% 5% 4 4 4 5% 6% 32%	108540
	Night	18% 12% 4 9% 5% 4 4 3 5% 5% 29%	109690
Transparency	Day	52% 6% 11% 21% 9% 1	112040
	Night	57% 5% 11% 18% 9% 1	114354
Seeing	Day	23% 16% 30% 20% 9% 2	14752
	Night	24% 14% 30% 24% 8% 1	23968

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	17% 21% 6% 13% 5% 5% 4 3 4 4 18%	3597
	11th to 20th	Day	13% 17% 8% 15% 7% 5% 4 4 4 5% 20%	3570
	21st to end	Day	13% 19% 7% 12% 6% 6% 5% 3 4 5% 19%	4098
February	1st to 10th	Day	17% 16% 5% 10% 7% 5% 4 3 5% 4 23%	1755
	11th to 20th	Day	16% 16% 6% 11% 6% 4 4 4 3 4 26%	1705
	21st to end	Day	20% 17% 4 10% 7% 4 3 4 4 4 23%	1570
March	1st to 10th	Day	21% 13% 4 8% 5% 4 4 3 4 5% 28%	3116
	11th to 20th	Day	14% 18% 5% 10% 5% 5% 4 3 4 4 28%	3432
	21st to end	Day	15% 8% 3 8% 5% 4 4 3 4 6% 41%	4065
April	1st to 10th	Day	22% 14% 3 7% 5% 4 3 3 4 4 32%	2280
	11th to 20th	Day	22% 10% 3 7% 4 4 3 2 3 5% 36%	2254
	21st to end	Day	23% 10% 3 7% 4 4 3 4 5% 5% 32%	2377
May	1st to 10th	Day	21% 8% 3 8% 5% 5% 4 4 5% 7% 31%	4426
	11th to 20th	Day	18% 9% 3 8% 5% 4 4 3 5% 7% 33%	4398
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 6% 8% 38%	4837
June	1st to 10th	Day	23% 8% 3 6% 5% 4 5% 4 6% 7% 30%	2660
	11th to 20th	Day	15% 7% 2 6% 5% 5% 4 4 6% 7% 38%	2660
	21st to end	Day	21% 7% 2 6% 5% 5% 5% 4 5% 6% 32%	2660
July	1st to 10th	Day	13% 6% 3 7% 5% 5% 5% 5% 6% 9% 37%	4440
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 4 7% 9% 39%	4440
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 7% 9% 42%	4814
August	1st to 10th	Day	17% 7% 3 7% 5% 5% 5% 4 5% 9% 34%	4395
	11th to 20th	Day	16% 7% 2 5% 4 4 4 4 6% 8% 39%	3926
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 6% 8% 39%	4180
September	1st to 10th	Day	15% 5% 2 5% 4 5% 4 4 5% 8% 42%	2280
	11th to 20th	Day	15% 4 2 5% 4 4 4 3 5% 7% 47%	2256
	21st to end	Day	18% 6% 3 6% 4 3 4 4 6% 7% 39%	2066
October	1st to 10th	Day	21% 7% 2 7% 4 4 4 4 5% 7% 34%	1900
	11th to 20th	Day	21% 10% 3 8% 5% 6% 5% 3 4 7% 29%	1900
	21st to end	Day	27% 10% 3 7% 4 5% 4 2 3 6% 27%	1916
November	1st to 10th	Day	17% 10% 3 7% 6% 4 4 4 5% 7% 32%	1761
	11th to 20th	Day	17% 13% 3 8% 5% 4 4 4 5% 6% 30%	1660
	21st to end	Day	21% 16% 4 9% 6% 4 5% 3 4 5% 21%	1600
December	1st to 10th	Day	22% 22% 5% 10% 5% 4 4 4 4 5% 14%	2600
	11th to 20th	Day	18% 18% 5% 11% 6% 4 4 3 4 4 23%	2986
	21st to end	Day	22% 16% 4 12% 6% 4 5% 4 3 4 21%	3960
January	1st to 10th	Night	16% 22% 7% 13% 6% 4 3 3 4 4 19%	6349
	11th to 20th	Night	11% 18% 8% 17% 7% 6% 6% 3 4 4 15%	6315
	21st to end	Night	17% 19% 7% 11% 7% 5% 4 3 4 5% 19%	6843
February	1st to 10th	Night	17% 16% 5% 13% 6% 6% 4 3 4 5% 20%	2536
	11th to 20th	Night	15% 15% 5% 11% 6% 4 4 3 5% 5% 26%	2361
	21st to end	Night	18% 14% 4 11% 6% 4 3 3 4 5% 29%	1884
March	1st to 10th	Night	22% 11% 3 7% 5% 4 3 3 4 4 33%	3724
	11th to 20th	Night	20% 18% 4 8% 5% 3 3 2 4 5% 27%	3525
	21st to end	Night	16% 12% 3 6% 5% 4 3 3 4 5% 39%	3567
April	1st to 10th	Night	22% 10% 4 8% 4 4 4 3 5% 4 32%	1900
	11th to 20th	Night	21% 10% 3 7% 5% 4 4 2 5% 7% 33%	1875
	21st to end	Night	23% 9% 2 8% 4 4 3 3 4 5% 35%	1817
May	1st to 10th	Night	23% 9% 3 7% 4 5% 5% 3 6% 7% 28%	2514
	11th to 20th	Night	22% 9% 3 7% 4 4 4 3 5% 5% 36%	2495
	21st to end	Night	15% 6% 2 6% 4 4 5% 3 6% 9% 40%	2738
June	1st to 10th	Night	18% 6% 3 7% 5% 6% 6% 4 7% 8% 30%	1520
	11th to 20th	Night	16% 6% 2 6% 5% 5% 4 4 6% 8% 39%	1520
	21st to end	Night	21% 8% 2 6% 4 4 4 4 6% 7% 34%	1520
July	1st to 10th	Night	15% 6% 2 8% 6% 4 4 4 6% 8% 36%	2520
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 7% 8% 41%	2520
	21st to end	Night	13% 6% 2 7% 5% 5% 5% 5% 6% 7% 41%	2739
August	1st to 10th	Night	15% 8% 3 6% 4 4 4 3 5% 8% 38%	2531
	11th to 20th	Night	17% 6% 3 7% 4 4 4 4 5% 7% 39%	2871
	21st to end	Night	13% 5% 2 7% 5% 5% 5% 4 6% 7% 41%	3476
September	1st to 10th	Night	15% 6% 2 6% 4 4 5% 4 5% 5% 45%	1900
	11th to 20th	Night	15% 5% 1 4 4 3 3 3 5% 8% 49%	1924
	21st to end	Night	16% 6% 3 6% 5% 4 4 4 5% 6% 42%	2109
October	1st to 10th	Night	19% 8% 3 6% 4 4 4 4 5% 7% 35%	2280
	11th to 20th	Night	21% 9% 3 7% 5% 4 4 3 5% 5% 34%	2280
	21st to end	Night	26% 9% 3 8% 5% 4 4 3 5% 6% 27%	2681
November	1st to 10th	Night	19% 11% 3 7% 4 4 4 4 4 5% 35%	2537
	11th to 20th	Night	18% 12% 4 8% 5% 4 4 3 4 6% 32%	2735
	21st to end	Night	23% 15% 4 9% 5% 4 4 3 4 5% 24%	2800
December	1st to 10th	Night	20% 19% 6% 12% 6% 5% 4 3 4 5% 15%	4580
	11th to 20th	Night	24% 16% 4 10% 5% 4 4 2 3 4 24%	5208
	21st to end	Night	26% 16% 4 11% 4 4 4 4 4 4 19%	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	70% 7% 8% 11% 3	3598
	11th to 20th	Day	71% 4 10% 8% 7% 1	3600
	21st to end	Day	69% 5% 9% 9% 7% 1	4098
February	1st to 10th	Day	66% 3 7% 18% 4 1	1755
	11th to 20th	Day	63% 5% 10% 14% 7% 1	1714
	21st to end	Day	64% 5% 9% 12% 8% 1	1570
March	1st to 10th	Day	59% 5% 9% 19% 7% 1	3119
	11th to 20th	Day	59% 5% 12% 13% 9% 2	3432
	21st to end	Day	47% 4 8% 21% 17% 3	4065
April	1st to 10th	Day	56% 3 7% 19% 12% 3	2280
	11th to 20th	Day	52% 4 7% 19% 15% 2	2254
	21st to end	Day	54% 4 9% 16% 14% 3	2377
May	1st to 10th	Day	53% 6% 9% 19% 10% 1	4440
	11th to 20th	Day	50% 8% 11% 20% 10% 1	4402
	21st to end	Day	42% 7% 11% 25% 13% 1	4837
June	1st to 10th	Day	51% 8% 10% 19% 12% 1	2660
	11th to 20th	Day	44% 6% 11% 25% 12% 2	2660
	21st to end	Day	50% 8% 11% 20% 11% 1	2660
July	1st to 10th	Day	40% 6% 13% 29% 11% 1	4370
	11th to 20th	Day	40% 7% 15% 30% 8%	4365
	21st to end	Day	38% 8% 13% 32% 9%	4661
August	1st to 10th	Day	48% 6% 15% 22% 9%	4381
	11th to 20th	Day	42% 7% 16% 27% 8%	3965
	21st to end	Day	42% 6% 16% 25% 11%	4180
September	1st to 10th	Day	40% 6% 14% 27% 13%	2280
	11th to 20th	Day	37% 5% 12% 32% 14% 1	2256
	21st to end	Day	44% 6% 14% 26% 10%	2066
October	1st to 10th	Day	47% 4 12% 28% 9%	3160
	11th to 20th	Day	49% 5% 15% 24% 6%	3140
	21st to end	Day	48% 4 17% 23% 7%	3128
November	1st to 10th	Day	52% 6% 12% 22% 7% 1	1761
	11th to 20th	Day	55% 6% 11% 16% 10% 2	1660
	21st to end	Day	67% 5% 11% 12% 4	1600
December	1st to 10th	Day	74% 6% 9% 10% 1	2600
	11th to 20th	Day	67% 5% 8% 14% 6%	2986
	21st to end	Day	68% 4 8% 16% 4	3960
January	1st to 10th	Night	71% 6% 10% 10% 3	6349
	11th to 20th	Night	75% 5% 8% 9% 4	6360
	21st to end	Night	71% 5% 7% 9% 8% 1	6843
February	1st to 10th	Night	69% 4 8% 13% 5%	2536
	11th to 20th	Night	61% 5% 8% 19% 7%	2363
	21st to end	Night	61% 4 8% 16% 9% 1	1884
March	1st to 10th	Night	55% 5% 9% 21% 9% 1	3734
	11th to 20th	Night	61% 5% 14% 11% 7% 1	3526
	21st to end	Night	51% 3 7% 22% 15% 3	3567
April	1st to 10th	Night	55% 5% 8% 19% 12% 1	1900
	11th to 20th	Night	52% 5% 8% 19% 14% 1	1875
	21st to end	Night	52% 4 10% 17% 14% 4	1817
May	1st to 10th	Night	54% 7% 10% 17% 10% 2	2520
	11th to 20th	Night	50% 6% 11% 20% 10% 1	2496
	21st to end	Night	41% 6% 13% 21% 17% 2	2739
June	1st to 10th	Night	50% 7% 12% 18% 11% 1	1520
	11th to 20th	Night	42% 6% 13% 20% 17% 2	1520
	21st to end	Night	49% 7% 12% 18% 13% 1	1520
July	1st to 10th	Night	45% 5% 13% 22% 14% 1	2480
	11th to 20th	Night	39% 6% 15% 32% 9%	2472
	21st to end	Night	41% 8% 13% 23% 14%	2651
August	1st to 10th	Night	45% 7% 14% 25% 9%	2521
	11th to 20th	Night	45% 6% 13% 27% 8% 1	2898
	21st to end	Night	40% 7% 14% 27% 12% 1	3476
September	1st to 10th	Night	41% 6% 11% 28% 14% 1	1900
	11th to 20th	Night	35% 5% 14% 32% 13% 1	1924
	21st to end	Night	43% 6% 11% 27% 13% 1	2109
October	1st to 10th	Night	45% 5% 13% 27% 9% 1	3800
	11th to 20th	Night	46% 4 15% 25% 10%	3779
	21st to end	Night	51% 5% 17% 20% 8%	4419
November	1st to 10th	Night	52% 4 12% 20% 10% 1	2537
	11th to 20th	Night	54% 6% 12% 17% 9% 2	2735
	21st to end	Night	63% 5% 13% 14% 5%	2800
December	1st to 10th	Night	75% 5% 10% 9% 2	4580
	11th to 20th	Night	66% 5% 7% 14% 7%	5208
	21st to end	Night	69% 4 7% 12% 7%	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	31% 18% 31% 17% 4	200
	11th to 20th	Day	29% 22% 32% 12% 5% 1	200
	21st to end	Day	24% 20% 35% 16% 4	250
February	1st to 10th	Day	31% 29% 29% 8% 2	285
	11th to 20th	Day	24% 29% 37% 10% 1	312
	21st to end	Day	31% 20% 33% 14% 2	382
March	1st to 10th	Day	26% 21% 32% 17% 5%	460
	11th to 20th	Day	25% 22% 35% 15% 3 1	460
	21st to end	Day	31% 20% 29% 14% 6% 1	506
April	1st to 10th	Day	31% 18% 29% 17% 4 1	460
	11th to 20th	Day	31% 23% 22% 17% 5% 2	452
	21st to end	Day	30% 18% 31% 12% 7% 1	460
May	1st to 10th	Day	24% 18% 32% 17% 8% 1	463
	11th to 20th	Day	17% 18% 34% 18% 9% 2	487
	21st to end	Day	17% 18% 31% 23% 10% 1	529
June	1st to 10th	Day	27% 13% 28% 24% 7% 2	490
	11th to 20th	Day	16% 14% 34% 25% 9% 3	490
	21st to end	Day	23% 14% 33% 17% 11% 1	490
July	1st to 10th	Day	13% 9% 33% 29% 14% 2	485
	11th to 20th	Day	14% 10% 31% 29% 12% 3	484
	21st to end	Day	15% 7% 32% 31% 13% 2	532
August	1st to 10th	Day	17% 11% 24% 33% 13% 3	486
	11th to 20th	Day	15% 7% 27% 27% 16% 7%	479
	21st to end	Day	14% 10% 32% 24% 13% 6%	539
September	1st to 10th	Day	14% 11% 28% 27% 12% 8%	490
	11th to 20th	Day	12% 9% 24% 25% 18% 12%	490
	21st to end	Day	19% 12% 30% 20% 14% 5%	490
October	1st to 10th	Day	23% 15% 27% 18% 12% 5%	490
	11th to 20th	Day	24% 19% 31% 17% 7% 1	490
	21st to end	Day	31% 19% 24% 21% 5%	446
November	1st to 10th	Day	25% 21% 28% 17% 8% 1	395
	11th to 20th	Day	26% 19% 33% 15% 5% 1	260
	21st to end	Day	30% 23% 32% 12% 4 1	200
December	1st to 10th	Day	30% 23% 26% 17% 5% 1	200
	11th to 20th	Day	32% 32% 24% 10% 3 1	200
	21st to end	Day	31% 22% 29% 13% 5%	220
January	1st to 10th	Night	29% 19% 31% 18% 3	800
	11th to 20th	Night	31% 17% 29% 19% 4	800
	21st to end	Night	21% 16% 34% 24% 4	880
February	1st to 10th	Night	25% 19% 34% 21% 2	781
	11th to 20th	Night	23% 19% 36% 19% 3	743
	21st to end	Night	26% 18% 31% 23% 2	628
March	1st to 10th	Night	26% 15% 33% 23% 4	760
	11th to 20th	Night	28% 19% 30% 19% 4	760
	21st to end	Night	24% 16% 28% 25% 7%	836
April	1st to 10th	Night	28% 14% 30% 23% 4	760
	11th to 20th	Night	26% 19% 29% 19% 7%	751
	21st to end	Night	28% 13% 30% 21% 8% 1	677
May	1st to 10th	Night	25% 10% 30% 26% 7% 2	380
	11th to 20th	Night	20% 11% 35% 27% 8%	374
	21st to end	Night	14% 9% 40% 25% 11%	411
June	1st to 10th	Night	20% 8% 30% 36% 6% 1	380
	11th to 20th	Night	17% 11% 28% 30% 13% 1	380
	21st to end	Night	22% 7% 28% 30% 12% 1	380
July	1st to 10th	Night	9% 6% 31% 40% 13% 1	370
	11th to 20th	Night	15% 5% 27% 36% 17% 1	368
	21st to end	Night	11% 5% 29% 44% 10% 1	416
August	1st to 10th	Night	17% 4 21% 42% 16% 1	390
	11th to 20th	Night	15% 5% 21% 38% 20% 1	611
	21st to end	Night	15% 5% 29% 32% 17% 2	836
September	1st to 10th	Night	16% 8% 28% 32% 16% 1	760
	11th to 20th	Night	17% 6% 21% 30% 21% 4	760
	21st to end	Night	17% 9% 28% 24% 20% 2	760
October	1st to 10th	Night	23% 10% 28% 23% 14% 1	760
	11th to 20th	Night	25% 13% 30% 23% 8%	760
	21st to end	Night	30% 14% 28% 22% 5%	836
November	1st to 10th	Night	27% 17% 28% 21% 7% 1	780
	11th to 20th	Night	24% 19% 30% 20% 8%	800
	21st to end	Night	29% 19% 28% 19% 5%	800
December	1st to 10th	Night	31% 19% 30% 18% 4	800
	11th to 20th	Night	29% 18% 33% 15% 4 1	800
	21st to end	Night	34% 16% 29% 18% 4	880

Page generated at 2025-02-03 03:05:55. Version ac07

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