Fredericton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fredericton 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	19% 9% 3 8% 5% 4 4 4 5% 7% 32%	137517
	Night	19% 10% 3 7% 4 4 4 3 5% 6% 33%	134667
Transparency	Day	51% 5% 11% 21% 11% 1	141033
	Night	51% 5% 11% 21% 11% 1	139241
Seeing	Day	27% 17% 30% 18% 7% 1	18429
	Night	26% 14% 30% 23% 6%	26338

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	12% 17% 6% 12% 5% 5% 4 3 5% 5% 26%	4093
	11th to 20th	Day	15% 14% 6% 14% 6% 5% 4 3 4 4 26%	4571
	21st to end	Day	8% 9% 3 7% 4 5% 6% 5% 7% 8% 38%	5498
February	1st to 10th	Day	14% 11% 4 9% 6% 5% 5% 4 5% 6% 31%	1890
	11th to 20th	Day	15% 12% 3 9% 5% 5% 5% 4 5% 6% 30%	1843
	21st to end	Day	11% 11% 4 9% 6% 5% 4 4 5% 6% 34%	1688
March	1st to 10th	Day	24% 12% 4 10% 5% 4 3 3 4 5% 27%	4805
	11th to 20th	Day	20% 14% 4 8% 5% 5% 4 3 5% 6% 26%	5090
	21st to end	Day	26% 13% 4 8% 5% 4 4 3 5% 6% 22%	5587
April	1st to 10th	Day	21% 15% 3 7% 4 4 4 4 4 6% 28%	2465
	11th to 20th	Day	22% 10% 2 7% 4 4 4 3 5% 6% 32%	2702
	21st to end	Day	25% 9% 3 6% 4 4 4 3 5% 5% 32%	2730
May	1st to 10th	Day	27% 12% 3 7% 5% 4 4 3 5% 6% 25%	7639
	11th to 20th	Day	22% 7% 2 7% 5% 5% 5% 4 5% 7% 31%	8042
	21st to end	Day	22% 9% 3 8% 5% 4 4 3 5% 6% 30%	9409
June	1st to 10th	Day	24% 9% 3 7% 5% 4 5% 4 5% 7% 28%	3150
	11th to 20th	Day	23% 7% 2 6% 5% 4 4 4 5% 7% 34%	3075
	21st to end	Day	27% 7% 3 6% 5% 4 5% 4 5% 7% 27%	3000
July	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 5% 7% 9% 29%	6820
	11th to 20th	Day	17% 6% 2 7% 4 5% 4 4 6% 8% 38%	6804
	21st to end	Day	14% 6% 2 6% 4 4 5% 4 6% 9% 39%	6639
August	1st to 10th	Day	20% 7% 3 7% 5% 5% 4 4 6% 7% 33%	4235
	11th to 20th	Day	14% 8% 3 8% 6% 5% 6% 4 6% 8% 32%	4175
	21st to end	Day	15% 6% 2 5% 3 4 5% 4 6% 8% 43%	4675
September	1st to 10th	Day	13% 5% 2 6% 3 4 5% 3 5% 8% 46%	2382
	11th to 20th	Day	17% 6% 2 5% 3 4 4 3 4 5% 47%	2200
	21st to end	Day	19% 6% 2 6% 4 3 4 3 4 6% 44%	2200
October	1st to 10th	Day	18% 6% 2 6% 4 3 4 3 5% 7% 41%	2042
	11th to 20th	Day	20% 7% 3 7% 4 4 4 3 6% 6% 36%	2000
	21st to end	Day	21% 9% 4 8% 5% 5% 4 2 5% 6% 31%	2060
November	1st to 10th	Day	21% 8% 3 7% 4 4 4 3 4 6% 36%	1785
	11th to 20th	Day	22% 7% 2 6% 4 5% 3 4 5% 8% 34%	1680
	21st to end	Day	22% 11% 4 8% 5% 4 4 3 4 5% 30%	1680
December	1st to 10th	Day	20% 11% 2 8% 4 3 4 3 6% 7% 32%	2622
	11th to 20th	Day	22% 10% 3 8% 5% 4 3 2 4 5% 34%	2688
	21st to end	Day	19% 13% 4 7% 4 3 4 3 4 4 35%	3553
January	1st to 10th	Night	14% 15% 5% 9% 5% 4 5% 4 6% 6% 29%	8831
	11th to 20th	Night	18% 13% 4 11% 6% 5% 4 3 5% 6% 25%	8316
	21st to end	Night	8% 12% 4 7% 5% 5% 5% 4 6% 8% 38%	8681
February	1st to 10th	Night	15% 12% 4 7% 4 4 4 4 6% 6% 33%	2730
	11th to 20th	Night	16% 12% 4 8% 6% 4 5% 4 6% 7% 29%	2663
	21st to end	Night	15% 13% 3 7% 6% 4 4 4 5% 5% 35%	2116
March	1st to 10th	Night	25% 12% 4 8% 5% 5% 4 2 4 4 26%	5254
	11th to 20th	Night	21% 12% 3 7% 4 4 4 4 5% 7% 27%	5089
	21st to end	Night	31% 10% 3 6% 3 3 3 3 5% 5% 28%	5587
April	1st to 10th	Night	25% 12% 2 7% 4 4 4 3 5% 5% 30%	2151
	11th to 20th	Night	24% 8% 2 6% 4 3 4 3 5% 5% 35%	1868
	21st to end	Night	25% 9% 3 6% 3 4 4 2 5% 7% 32%	1890
May	1st to 10th	Night	27% 10% 3 7% 4 4 4 3 5% 6% 26%	5259
	11th to 20th	Night	22% 8% 2 6% 4 4 5% 4 5% 6% 34%	4839
	21st to end	Night	19% 9% 3 8% 4 4 4 3 5% 6% 35%	4853
June	1st to 10th	Night	25% 8% 2 6% 5% 5% 4 3 5% 6% 30%	1470
	11th to 20th	Night	20% 6% 3 5% 5% 4 4 5% 5% 7% 35%	1435
	21st to end	Night	29% 5% 3 6% 5% 3 4 3 5% 6% 32%	1400
July	1st to 10th	Night	17% 7% 3 7% 6% 5% 5% 5% 7% 7% 31%	3160
	11th to 20th	Night	18% 5% 3 7% 5% 5% 4 4 6% 9% 35%	3160
	21st to end	Night	13% 6% 2 6% 4 5% 5% 5% 7% 7% 40%	4154
August	1st to 10th	Night	19% 6% 3 8% 5% 5% 5% 4 6% 8% 32%	2915
	11th to 20th	Night	13% 8% 3 8% 5% 5% 5% 4 7% 8% 34%	2872
	21st to end	Night	15% 5% 2 5% 4 4 4 4 6% 7% 46%	3223
September	1st to 10th	Night	16% 6% 2 5% 4 3 3 3 6% 7% 46%	2014
	11th to 20th	Night	16% 5% 3 5% 4 4 3 3 4 6% 49%	2200
	21st to end	Night	20% 5% 2 5% 4 3 3 3 4 5% 46%	2200
October	1st to 10th	Night	19% 6% 2 6% 3 3 3 3 6% 6% 44%	2357
	11th to 20th	Night	20% 6% 3 6% 5% 4 4 3 5% 7% 37%	2400
	21st to end	Night	23% 8% 3 7% 5% 4 4 3 4 6% 34%	2778
November	1st to 10th	Night	22% 7% 3 7% 4 4 4 3 5% 6% 36%	2730
	11th to 20th	Night	20% 8% 3 6% 4 4 4 3 6% 6% 35%	2940
	21st to end	Night	23% 10% 3 7% 4 4 4 4 5% 6% 31%	2940
December	1st to 10th	Night	18% 10% 3 7% 4 3 4 3 5% 6% 35%	4784
	11th to 20th	Night	23% 10% 2 6% 3 3 4 3 4 5% 35%	5741
	21st to end	Night	21% 13% 4 8% 4 3 3 3 4 4 32%	7667

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% 4 11% 16% 9%	4094
	11th to 20th	Day	61% 5% 9% 16% 8% 1	4601
	21st to end	Day	42% 5% 10% 24% 18% 1	5498
February	1st to 10th	Day	53% 5% 10% 20% 9% 2	1890
	11th to 20th	Day	54% 5% 10% 20% 10% 1	1851
	21st to end	Day	49% 5% 11% 23% 11% 2	1688
March	1st to 10th	Day	61% 3 9% 12% 12% 3	4809
	11th to 20th	Day	59% 6% 12% 14% 7% 2	5090
	21st to end	Day	63% 3 5% 18% 9% 2	5587
April	1st to 10th	Day	57% 3 9% 15% 13% 2	2465
	11th to 20th	Day	51% 4 10% 21% 12% 1	2702
	21st to end	Day	53% 5% 8% 17% 13% 5%	2730
May	1st to 10th	Day	60% 5% 8% 17% 9% 1	7651
	11th to 20th	Day	51% 6% 12% 21% 8% 2	8046
	21st to end	Day	54% 5% 9% 16% 15% 1	9410
June	1st to 10th	Day	55% 6% 10% 18% 10% 1	3150
	11th to 20th	Day	49% 5% 12% 21% 12% 1	3075
	21st to end	Day	57% 6% 10% 17% 10% 1	3000
July	1st to 10th	Day	50% 6% 16% 19% 9%	6745
	11th to 20th	Day	42% 6% 15% 27% 9%	6723
	21st to end	Day	41% 6% 14% 30% 9%	6449
August	1st to 10th	Day	50% 5% 13% 25% 7%	4222
	11th to 20th	Day	48% 6% 15% 24% 7%	4214
	21st to end	Day	38% 5% 14% 26% 16%	4675
September	1st to 10th	Day	37% 6% 15% 27% 15%	2382
	11th to 20th	Day	39% 4 10% 29% 16% 2	2200
	21st to end	Day	42% 5% 9% 27% 16% 1	2200
October	1st to 10th	Day	47% 5% 12% 27% 9%	3328
	11th to 20th	Day	44% 5% 12% 31% 8%	3240
	21st to end	Day	42% 4 15% 23% 16%	3310
November	1st to 10th	Day	50% 5% 12% 22% 11% 1	1785
	11th to 20th	Day	48% 5% 15% 18% 13% 1	1680
	21st to end	Day	56% 5% 13% 20% 6%	1680
December	1st to 10th	Day	51% 4 17% 18% 9%	2622
	11th to 20th	Day	55% 4 8% 19% 10% 4	2688
	21st to end	Day	53% 3 11% 17% 13% 3	3553
January	1st to 10th	Night	55% 5% 11% 21% 8%	8831
	11th to 20th	Night	60% 5% 9% 19% 7% 1	8361
	21st to end	Night	44% 5% 8% 24% 17% 2	8681
February	1st to 10th	Night	51% 5% 12% 20% 12% 1	2730
	11th to 20th	Night	53% 5% 10% 19% 11% 1	2666
	21st to end	Night	52% 4 9% 21% 12% 3	2116
March	1st to 10th	Night	63% 3 6% 13% 12% 3	5263
	11th to 20th	Night	56% 5% 16% 14% 8% 1	5090
	21st to end	Night	60% 3 6% 18% 13% 1	5587
April	1st to 10th	Night	56% 4 8% 17% 11% 4	2151
	11th to 20th	Night	51% 5% 9% 21% 14% 1	1868
	21st to end	Night	53% 5% 9% 18% 13% 2	1890
May	1st to 10th	Night	59% 4 11% 16% 9% 1	5265
	11th to 20th	Night	51% 5% 10% 25% 8% 2	4840
	21st to end	Night	49% 5% 13% 19% 11% 2	4854
June	1st to 10th	Night	54% 6% 10% 20% 9% 1	1470
	11th to 20th	Night	48% 6% 13% 23% 10% 2	1435
	21st to end	Night	53% 6% 12% 19% 9% 1	1400
July	1st to 10th	Night	49% 5% 15% 22% 9%	3125
	11th to 20th	Night	46% 6% 15% 28% 5%	3118
	21st to end	Night	41% 7% 15% 28% 10%	4030
August	1st to 10th	Night	51% 8% 13% 21% 7%	2903
	11th to 20th	Night	45% 7% 19% 23% 6%	2899
	21st to end	Night	37% 5% 17% 23% 16% 2	3223
September	1st to 10th	Night	37% 5% 14% 29% 14% 1	2014
	11th to 20th	Night	38% 5% 12% 29% 15% 1	2200
	21st to end	Night	41% 5% 11% 28% 15% 1	2200
October	1st to 10th	Night	46% 4 12% 25% 12%	3851
	11th to 20th	Night	41% 5% 11% 30% 13%	3899
	21st to end	Night	44% 4 15% 23% 13%	4478
November	1st to 10th	Night	49% 5% 13% 22% 10% 1	2730
	11th to 20th	Night	50% 4 13% 21% 11% 1	2940
	21st to end	Night	54% 6% 14% 17% 9%	2940
December	1st to 10th	Night	50% 4 13% 25% 8%	4784
	11th to 20th	Night	51% 3 10% 21% 13% 1	5742
	21st to end	Night	56% 4 9% 19% 10% 3	7667

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% 35% 14% 2	220
	11th to 20th	Day	35% 21% 30% 10% 4	220
	21st to end	Day	22% 21% 35% 17% 4 1	371
February	1st to 10th	Day	27% 17% 32% 18% 4 1	430
	11th to 20th	Day	28% 22% 31% 15% 3 1	426
	21st to end	Day	26% 24% 29% 18% 3	424
March	1st to 10th	Day	33% 21% 31% 13% 2 1	540
	11th to 20th	Day	31% 21% 29% 14% 4 1	540
	21st to end	Day	34% 21% 27% 12% 5% 1	594
April	1st to 10th	Day	39% 25% 24% 9% 3	540
	11th to 20th	Day	35% 21% 28% 12% 3 1	532
	21st to end	Day	30% 20% 32% 12% 5% 1	540
May	1st to 10th	Day	36% 18% 28% 13% 4 1	543
	11th to 20th	Day	29% 19% 28% 17% 6% 1	711
	21st to end	Day	28% 17% 34% 15% 7%	845
June	1st to 10th	Day	30% 17% 29% 17% 7% 1	780
	11th to 20th	Day	29% 14% 29% 19% 8% 1	755
	21st to end	Day	29% 12% 30% 21% 7% 1	730
July	1st to 10th	Day	23% 11% 35% 20% 9% 1	720
	11th to 20th	Day	21% 8% 34% 25% 11% 2	715
	21st to end	Day	18% 11% 37% 25% 8% 2	576
August	1st to 10th	Day	18% 9% 35% 26% 10% 2	526
	11th to 20th	Day	20% 9% 27% 29% 13% 3	519
	21st to end	Day	21% 13% 26% 26% 11% 3	583
September	1st to 10th	Day	14% 14% 33% 26% 10% 3	530
	11th to 20th	Day	22% 11% 29% 24% 11% 4	530
	21st to end	Day	19% 18% 30% 18% 11% 4	530
October	1st to 10th	Day	23% 15% 23% 25% 12% 3	442
	11th to 20th	Day	25% 18% 29% 16% 10% 2	420
	21st to end	Day	30% 18% 32% 13% 6%	462
November	1st to 10th	Day	32% 15% 29% 18% 5%	425
	11th to 20th	Day	34% 18% 27% 14% 6%	430
	21st to end	Day	31% 21% 28% 15% 4	430
December	1st to 10th	Day	32% 17% 30% 17% 4 1	388
	11th to 20th	Day	37% 26% 25% 9% 2	220
	21st to end	Day	30% 23% 26% 17% 3	242
January	1st to 10th	Night	26% 19% 31% 20% 3	950
	11th to 20th	Night	29% 16% 29% 21% 4	854
	21st to end	Night	19% 21% 35% 21% 4	924
February	1st to 10th	Night	23% 20% 31% 20% 5%	840
	11th to 20th	Night	25% 22% 33% 17% 4	823
	21st to end	Night	23% 18% 32% 22% 4	692
March	1st to 10th	Night	26% 18% 33% 20% 2	840
	11th to 20th	Night	26% 16% 32% 21% 5%	840
	21st to end	Night	27% 16% 33% 19% 5%	924
April	1st to 10th	Night	34% 17% 31% 15% 2	749
	11th to 20th	Night	31% 16% 31% 17% 5%	624
	21st to end	Night	30% 13% 31% 21% 5%	630
May	1st to 10th	Night	29% 15% 29% 22% 4	630
	11th to 20th	Night	29% 14% 32% 21% 5%	622
	21st to end	Night	21% 16% 34% 24% 4	583
June	1st to 10th	Night	29% 7% 33% 25% 6%	420
	11th to 20th	Night	21% 10% 32% 30% 6%	410
	21st to end	Night	31% 5% 27% 32% 5% 1	400
July	1st to 10th	Night	20% 5% 37% 32% 6%	390
	11th to 20th	Night	19% 6% 29% 34% 12% 1	388
	21st to end	Night	21% 6% 31% 33% 9%	538
August	1st to 10th	Night	17% 6% 28% 35% 14%	598
	11th to 20th	Night	19% 6% 28% 33% 14%	592
	21st to end	Night	17% 7% 29% 31% 15% 1	660
September	1st to 10th	Night	19% 8% 36% 27% 10% 1	639
	11th to 20th	Night	20% 9% 24% 32% 14% 1	800
	21st to end	Night	21% 12% 27% 28% 12%	800
October	1st to 10th	Night	21% 11% 28% 29% 10% 1	800
	11th to 20th	Night	22% 13% 30% 25% 10% 1	800
	21st to end	Night	28% 16% 29% 21% 5%	880
November	1st to 10th	Night	28% 14% 30% 22% 5% 1	853
	11th to 20th	Night	28% 16% 30% 19% 6% 1	950
	21st to end	Night	29% 19% 27% 20% 5% 1	950
December	1st to 10th	Night	33% 14% 28% 21% 4	950
	11th to 20th	Night	30% 21% 30% 17% 3	950
	21st to end	Night	30% 19% 28% 18% 3 1	1045

Page generated at 2026-06-13 03:31:45. Version ac07

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