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 2025-02-21.

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 7% 5% 4 4 4 5% 7% 33%	108255
	Night	19% 10% 3 7% 4 4 4 4 5% 6% 34%	110404
Transparency	Day	50% 5% 12% 21% 11% 1	111815
	Night	50% 5% 12% 22% 10% 1	115009
Seeing	Day	27% 17% 30% 18% 7% 1	16601
	Night	25% 14% 31% 23% 6%	24661

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	13% 18% 6% 12% 5% 5% 3 3 4 5% 25%	3157
	11th to 20th	Day	12% 13% 6% 13% 6% 5% 5% 4 4 5% 29%	3504
	21st to end	Day	10% 9% 3 7% 4 5% 6% 4 7% 7% 38%	4252
February	1st to 10th	Day	15% 11% 4 8% 6% 5% 5% 4 5% 5% 31%	1800
	11th to 20th	Day	16% 13% 3 9% 5% 5% 5% 4 5% 6% 29%	1753
	21st to end	Day	12% 12% 4 9% 6% 5% 4 4 5% 6% 34%	1532
March	1st to 10th	Day	24% 13% 3 7% 4 4 4 3 4 5% 30%	3270
	11th to 20th	Day	18% 16% 4 9% 6% 5% 5% 3 4 5% 24%	3480
	21st to end	Day	28% 13% 4 8% 5% 4 3 3 5% 6% 22%	3816
April	1st to 10th	Day	21% 15% 3 7% 4 4 4 4 4 6% 28%	2230
	11th to 20th	Day	21% 9% 2 7% 4 4 4 3 5% 6% 34%	2442
	21st to end	Day	26% 9% 3 6% 4 3 4 3 5% 5% 32%	2470
May	1st to 10th	Day	21% 12% 3 7% 6% 5% 4 3 5% 5% 29%	4106
	11th to 20th	Day	21% 8% 3 7% 5% 5% 5% 3 5% 7% 32%	4302
	21st to end	Day	19% 7% 3 7% 5% 5% 5% 4 6% 7% 32%	5018
June	1st to 10th	Day	25% 9% 3 7% 5% 4 5% 4 5% 7% 27%	2850
	11th to 20th	Day	22% 6% 2 6% 5% 4 4 4 5% 7% 35%	2850
	21st to end	Day	27% 7% 3 6% 5% 4 5% 4 5% 7% 27%	2850
July	1st to 10th	Day	16% 6% 2 7% 6% 6% 6% 5% 7% 9% 32%	4760
	11th to 20th	Day	19% 6% 2 7% 3 5% 4 4 7% 9% 34%	4744
	21st to end	Day	17% 7% 3 6% 5% 4 5% 4 6% 8% 36%	4611
August	1st to 10th	Day	21% 7% 3 8% 5% 5% 4 4 6% 7% 31%	4105
	11th to 20th	Day	15% 8% 3 8% 6% 5% 5% 4 6% 8% 32%	4045
	21st to end	Day	15% 6% 2 5% 4 4 5% 4 6% 8% 43%	4532
September	1st to 10th	Day	13% 5% 3 6% 4 4 5% 3 5% 7% 45%	2263
	11th to 20th	Day	18% 6% 2 4 3 4 4 3 4 5% 46%	2090
	21st to end	Day	20% 6% 2 6% 4 3 4 3 4 6% 43%	2090
October	1st to 10th	Day	19% 7% 2 6% 5% 4 4 3 5% 7% 39%	1940
	11th to 20th	Day	21% 7% 3 7% 4 4 4 3 6% 6% 37%	1900
	21st to end	Day	21% 8% 4 8% 5% 5% 4 2 5% 6% 31%	1957
November	1st to 10th	Day	21% 8% 3 7% 5% 4 4 3 4 6% 36%	1698
	11th to 20th	Day	22% 7% 2 6% 4 5% 3 4 6% 8% 34%	1600
	21st to end	Day	22% 12% 4 8% 4 3 4 3 4 5% 31%	1600
December	1st to 10th	Day	20% 11% 2 8% 4 3 4 3 6% 7% 32%	2544
	11th to 20th	Day	23% 10% 3 8% 4 4 3 2 4 5% 34%	2618
	21st to end	Day	19% 13% 4 7% 4 3 4 3 4 4 34%	3476
January	1st to 10th	Night	13% 14% 5% 10% 6% 4 5% 4 6% 6% 27%	6808
	11th to 20th	Night	16% 11% 4 12% 6% 5% 4 4 5% 6% 29%	6382
	21st to end	Night	10% 11% 3 7% 4 4 4 3 6% 8% 40%	6702
February	1st to 10th	Night	16% 13% 4 7% 4 4 4 4 6% 6% 33%	2600
	11th to 20th	Night	16% 12% 4 8% 6% 5% 5% 4 6% 7% 28%	2533
	21st to end	Night	15% 12% 3 8% 5% 5% 5% 4 5% 5% 33%	1922
March	1st to 10th	Night	23% 12% 4 7% 5% 6% 5% 3 4 4 28%	3569
	11th to 20th	Night	21% 14% 3 8% 5% 5% 4 5% 5% 7% 24%	3479
	21st to end	Night	31% 10% 4 6% 3 3 3 3 5% 5% 27%	3816
April	1st to 10th	Night	25% 12% 2 7% 4 3 4 3 4 5% 30%	1946
	11th to 20th	Night	23% 8% 2 6% 4 4 5% 3 5% 5% 36%	1688
	21st to end	Night	26% 9% 3 6% 3 4 3 3 5% 7% 32%	1710
May	1st to 10th	Night	21% 9% 3 8% 5% 4 4 4 5% 7% 31%	2834
	11th to 20th	Night	21% 7% 2 6% 4 4 5% 4 6% 6% 35%	2599
	21st to end	Night	16% 8% 3 7% 5% 4 5% 4 5% 8% 35%	2595
June	1st to 10th	Night	26% 8% 2 6% 5% 5% 4 4 5% 6% 29%	1330
	11th to 20th	Night	19% 6% 3 5% 5% 4 4 4 5% 8% 35%	1330
	21st to end	Night	29% 5% 3 6% 5% 3 3 3 5% 5% 32%	1330
July	1st to 10th	Night	16% 6% 2 6% 5% 5% 5% 5% 8% 8% 34%	2210
	11th to 20th	Night	20% 6% 3 6% 5% 4 4 4 6% 8% 34%	2210
	21st to end	Night	17% 7% 2 5% 4 4 5% 5% 7% 7% 37%	2897
August	1st to 10th	Night	20% 7% 3 8% 5% 5% 5% 4 6% 7% 30%	2825
	11th to 20th	Night	13% 8% 3 8% 5% 5% 5% 4 7% 8% 33%	2782
	21st to end	Night	15% 5% 2 5% 4 4 4 4 6% 7% 46%	3124
September	1st to 10th	Night	16% 6% 2 5% 4 3 3 3 6% 7% 45%	1913
	11th to 20th	Night	17% 6% 3 5% 4 4 3 2 4 6% 48%	2090
	21st to end	Night	21% 5% 2 5% 4 3 3 3 4 5% 46%	2090
October	1st to 10th	Night	20% 6% 2 6% 3 3 3 3 6% 6% 42%	2239
	11th to 20th	Night	20% 6% 3 6% 5% 4 4 4 5% 6% 38%	2280
	21st to end	Night	23% 8% 3 7% 5% 4 3 3 4 5% 35%	2639
November	1st to 10th	Night	21% 7% 3 7% 4 4 4 3 5% 6% 37%	2597
	11th to 20th	Night	21% 8% 3 6% 4 4 4 3 5% 6% 36%	2800
	21st to end	Night	23% 10% 3 7% 4 4 4 4 5% 6% 31%	2800
December	1st to 10th	Night	18% 10% 3 7% 4 3 4 3 5% 7% 35%	4642
	11th to 20th	Night	23% 10% 2 5% 3 3 4 3 4 5% 36%	5591
	21st to end	Night	21% 13% 4 8% 4 3 3 3 4 4 32%	7502

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	61% 4 13% 15% 6%	3158
	11th to 20th	Day	56% 6% 10% 20% 8% 1	3534
	21st to end	Day	43% 5% 10% 20% 19% 2	4252
February	1st to 10th	Day	54% 5% 10% 19% 10% 2	1800
	11th to 20th	Day	55% 5% 10% 18% 10% 1	1761
	21st to end	Day	49% 5% 11% 23% 10% 3	1532
March	1st to 10th	Day	58% 3 11% 16% 8% 4	3274
	11th to 20th	Day	62% 6% 9% 13% 8% 1	3480
	21st to end	Day	63% 3 6% 16% 9% 2	3816
April	1st to 10th	Day	58% 3 9% 15% 12% 3	2230
	11th to 20th	Day	50% 4 10% 22% 12% 1	2442
	21st to end	Day	53% 5% 8% 16% 13% 5%	2470
May	1st to 10th	Day	55% 6% 8% 22% 8% 1	4120
	11th to 20th	Day	50% 7% 13% 21% 8% 1	4306
	21st to end	Day	48% 8% 12% 18% 14%	5018
June	1st to 10th	Day	56% 7% 10% 17% 10% 1	2850
	11th to 20th	Day	49% 5% 12% 20% 13% 1	2850
	21st to end	Day	57% 6% 11% 16% 10% 1	2850
July	1st to 10th	Day	46% 7% 16% 19% 11%	4685
	11th to 20th	Day	46% 7% 14% 24% 9%	4663
	21st to end	Day	46% 7% 13% 26% 8%	4464
August	1st to 10th	Day	52% 5% 13% 24% 6%	4092
	11th to 20th	Day	49% 6% 15% 24% 7%	4084
	21st to end	Day	38% 5% 14% 26% 16%	4532
September	1st to 10th	Day	38% 6% 15% 27% 15%	2263
	11th to 20th	Day	40% 5% 10% 28% 16% 2	2090
	21st to end	Day	43% 5% 9% 27% 15% 1	2090
October	1st to 10th	Day	48% 5% 12% 27% 9%	3226
	11th to 20th	Day	44% 5% 11% 31% 8%	3140
	21st to end	Day	41% 4 15% 23% 17%	3207
November	1st to 10th	Day	50% 5% 12% 22% 11% 1	1698
	11th to 20th	Day	48% 5% 15% 17% 13% 1	1600
	21st to end	Day	56% 5% 14% 20% 6%	1600
December	1st to 10th	Day	52% 4 18% 18% 9%	2544
	11th to 20th	Day	55% 4 9% 19% 10% 4	2618
	21st to end	Day	54% 4 11% 16% 13% 3	3476
January	1st to 10th	Night	56% 5% 12% 20% 6% 1	6808
	11th to 20th	Night	55% 6% 10% 21% 7% 1	6427
	21st to end	Night	43% 4 9% 24% 18% 2	6702
February	1st to 10th	Night	51% 5% 12% 19% 12% 1	2600
	11th to 20th	Night	55% 5% 10% 18% 11% 2	2536
	21st to end	Night	52% 5% 9% 20% 11% 3	1922
March	1st to 10th	Night	61% 4 8% 18% 9% 1	3578
	11th to 20th	Night	59% 6% 12% 14% 8% 1	3480
	21st to end	Night	61% 3 7% 17% 11% 2	3816
April	1st to 10th	Night	56% 4 8% 16% 11% 4	1946
	11th to 20th	Night	49% 5% 8% 21% 15% 2	1688
	21st to end	Night	53% 5% 9% 18% 12% 3	1710
May	1st to 10th	Night	51% 6% 14% 19% 9% 1	2840
	11th to 20th	Night	47% 7% 14% 24% 7% 1	2600
	21st to end	Night	45% 8% 17% 20% 9% 1	2596
June	1st to 10th	Night	55% 6% 9% 19% 9% 1	1330
	11th to 20th	Night	47% 6% 13% 23% 10% 2	1330
	21st to end	Night	54% 6% 12% 19% 9% 1	1330
July	1st to 10th	Night	44% 6% 17% 22% 10%	2175
	11th to 20th	Night	47% 6% 15% 25% 6%	2168
	21st to end	Night	44% 7% 13% 27% 8%	2804
August	1st to 10th	Night	52% 8% 13% 20% 6%	2813
	11th to 20th	Night	46% 7% 18% 23% 6%	2809
	21st to end	Night	37% 5% 17% 23% 17% 2	3124
September	1st to 10th	Night	38% 5% 14% 28% 13% 1	1913
	11th to 20th	Night	39% 5% 12% 29% 15% 1	2090
	21st to end	Night	42% 5% 11% 27% 14% 1	2090
October	1st to 10th	Night	47% 4 12% 25% 12%	3733
	11th to 20th	Night	41% 5% 11% 30% 13%	3779
	21st to end	Night	44% 4 16% 23% 14%	4339
November	1st to 10th	Night	48% 5% 13% 22% 10% 1	2597
	11th to 20th	Night	50% 4 13% 21% 11% 1	2800
	21st to end	Night	55% 6% 14% 16% 9%	2800
December	1st to 10th	Night	50% 4 13% 25% 8%	4642
	11th to 20th	Night	51% 3 10% 21% 13% 1	5592
	21st to end	Night	56% 4 10% 19% 9% 3	7502

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% 36% 15% 2	200
	11th to 20th	Day	33% 21% 31% 11% 5% 1	200
	21st to end	Day	22% 21% 35% 17% 4 1	343
February	1st to 10th	Day	29% 18% 32% 16% 4 1	400
	11th to 20th	Day	29% 23% 30% 14% 3 1	396
	21st to end	Day	26% 23% 29% 19% 2	364
March	1st to 10th	Day	32% 20% 32% 13% 2 1	460
	11th to 20th	Day	28% 20% 31% 15% 5% 1	460
	21st to end	Day	32% 21% 27% 12% 6% 1	506
April	1st to 10th	Day	38% 25% 23% 10% 3	460
	11th to 20th	Day	32% 21% 29% 13% 4 1	452
	21st to end	Day	32% 20% 31% 12% 5% 1	460
May	1st to 10th	Day	34% 18% 28% 14% 5% 1	463
	11th to 20th	Day	28% 18% 28% 19% 7% 1	617
	21st to end	Day	25% 19% 34% 15% 7%	735
June	1st to 10th	Day	31% 18% 28% 16% 6% 1	680
	11th to 20th	Day	27% 14% 29% 20% 9% 1	680
	21st to end	Day	29% 12% 30% 21% 7% 1	680
July	1st to 10th	Day	24% 11% 35% 20% 10% 1	670
	11th to 20th	Day	21% 8% 34% 24% 11% 2	665
	21st to end	Day	18% 10% 36% 26% 9% 2	532
August	1st to 10th	Day	19% 10% 35% 25% 10% 2	486
	11th to 20th	Day	20% 10% 28% 28% 12% 2	479
	21st to end	Day	21% 12% 26% 26% 12% 3	539
September	1st to 10th	Day	14% 13% 34% 26% 9% 3	490
	11th to 20th	Day	22% 11% 30% 23% 10% 4	490
	21st to end	Day	20% 17% 29% 18% 11% 4	490
October	1st to 10th	Day	24% 15% 23% 24% 12% 3	410
	11th to 20th	Day	25% 19% 28% 16% 10% 2	390
	21st to end	Day	30% 18% 32% 14% 6%	429
November	1st to 10th	Day	31% 14% 30% 19% 6% 1	395
	11th to 20th	Day	34% 19% 27% 14% 6%	400
	21st to end	Day	32% 22% 28% 15% 3	400
December	1st to 10th	Day	32% 17% 30% 17% 4 1	360
	11th to 20th	Day	39% 26% 24% 10% 2	200
	21st to end	Day	30% 23% 27% 16% 4	220
January	1st to 10th	Night	26% 19% 31% 20% 3	900
	11th to 20th	Night	28% 16% 29% 22% 4	813
	21st to end	Night	19% 21% 35% 21% 4	880
February	1st to 10th	Night	24% 21% 31% 20% 4	800
	11th to 20th	Night	25% 22% 33% 15% 3	783
	21st to end	Night	23% 18% 31% 23% 4	629
March	1st to 10th	Night	26% 18% 34% 20% 3	760
	11th to 20th	Night	25% 16% 32% 21% 6%	760
	21st to end	Night	26% 16% 33% 20% 5%	836
April	1st to 10th	Night	33% 17% 31% 16% 3	678
	11th to 20th	Night	29% 16% 32% 17% 5%	564
	21st to end	Night	31% 14% 30% 20% 5%	570
May	1st to 10th	Night	28% 14% 30% 24% 4	570
	11th to 20th	Night	29% 14% 31% 21% 5%	562
	21st to end	Night	20% 16% 36% 25% 4	527
June	1st to 10th	Night	29% 6% 33% 24% 7%	380
	11th to 20th	Night	21% 10% 32% 30% 7% 1	380
	21st to end	Night	32% 4 26% 32% 5% 1	380
July	1st to 10th	Night	21% 5% 37% 31% 6%	370
	11th to 20th	Night	19% 6% 29% 33% 13% 1	368
	21st to end	Night	22% 6% 30% 33% 9%	511
August	1st to 10th	Night	18% 6% 29% 35% 13%	568
	11th to 20th	Night	20% 6% 28% 33% 13%	562
	21st to end	Night	17% 7% 29% 30% 16% 1	627
September	1st to 10th	Night	19% 8% 36% 26% 10%	607
	11th to 20th	Night	21% 8% 24% 31% 14% 1	760
	21st to end	Night	22% 12% 27% 27% 12%	760
October	1st to 10th	Night	22% 9% 28% 29% 10% 1	760
	11th to 20th	Night	21% 13% 31% 24% 10% 1	760
	21st to end	Night	28% 17% 30% 20% 5%	836
November	1st to 10th	Night	27% 13% 31% 23% 5% 1	810
	11th to 20th	Night	28% 17% 29% 19% 6% 1	900
	21st to end	Night	29% 19% 27% 20% 5%	900
December	1st to 10th	Night	33% 14% 28% 20% 4	900
	11th to 20th	Night	30% 20% 29% 17% 3	900
	21st to end	Night	31% 19% 28% 18% 4 1	990

Page generated at 2025-02-18 04:26:27. Version ac07

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