Grand Manan Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grand Manan Island clear sky chart from 2005-11-06 to 2026-03-03.

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% 10% 3 7% 4 4 4 3 5% 6% 33%	130688
	Night	20% 12% 4 8% 5% 4 4 3 5% 6% 31%	130573
Transparency	Day	52% 5% 11% 19% 11% 1	134221
	Night	54% 5% 10% 18% 10% 1	135128
Seeing	Day	24% 7% 22% 30% 15% 2	17985
	Night	26% 10% 25% 26% 11% 1	26120

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% 12% 5% 10% 6% 5% 5% 4 5% 5% 27%	4247
	11th to 20th	Day	19% 15% 4 11% 4 4 3 2 3 3 31%	4650
	21st to end	Day	13% 10% 4 9% 8% 7% 7% 4 5% 6% 27%	5698
February	1st to 10th	Day	19% 13% 5% 8% 6% 5% 5% 3 6% 7% 24%	1890
	11th to 20th	Day	17% 10% 4 8% 5% 7% 5% 4 5% 6% 30%	1843
	21st to end	Day	14% 12% 3 7% 5% 5% 5% 4 6% 6% 34%	1725
March	1st to 10th	Day	25% 10% 3 8% 6% 5% 4 3 4 5% 27%	4725
	11th to 20th	Day	21% 12% 3 6% 4 4 4 3 5% 7% 31%	4980
	21st to end	Day	28% 10% 3 6% 4 4 4 3 4 5% 28%	5466
April	1st to 10th	Day	22% 10% 3 7% 4 3 4 4 5% 6% 32%	2316
	11th to 20th	Day	20% 10% 2 6% 3 3 3 2 5% 7% 40%	2572
	21st to end	Day	21% 9% 2 5% 4 3 3 3 5% 6% 38%	2600
May	1st to 10th	Day	27% 13% 4 8% 4 4 3 3 4 5% 25%	5886
	11th to 20th	Day	21% 9% 3 7% 4 4 4 3 5% 6% 34%	5996
	21st to end	Day	19% 10% 3 8% 4 4 4 3 5% 7% 31%	7030
June	1st to 10th	Day	22% 8% 3 7% 4 4 3 4 5% 7% 32%	3000
	11th to 20th	Day	20% 9% 3 5% 4 3 4 4 5% 7% 37%	3000
	21st to end	Day	26% 10% 3 6% 3 4 4 3 5% 6% 30%	3000
July	1st to 10th	Day	18% 13% 5% 9% 4 4 4 3 6% 7% 26%	6820
	11th to 20th	Day	17% 14% 4 8% 4 4 4 3 5% 8% 29%	6557
	21st to end	Day	14% 10% 2 6% 4 4 4 4 6% 8% 37%	6497
August	1st to 10th	Day	20% 12% 4 7% 4 4 4 4 4 6% 31%	4235
	11th to 20th	Day	15% 10% 3 7% 4 4 5% 3 5% 7% 36%	4175
	21st to end	Day	11% 6% 2 5% 3 3 4 3 5% 7% 51%	4675
September	1st to 10th	Day	12% 7% 2 6% 4 3 3 3 5% 7% 48%	2345
	11th to 20th	Day	15% 6% 2 4 3 3 3 2 4 6% 49%	2200
	21st to end	Day	17% 7% 2 5% 4 3 3 2 5% 6% 46%	2200
October	1st to 10th	Day	16% 7% 3 5% 4 3 4 3 5% 7% 43%	2057
	11th to 20th	Day	18% 7% 2 6% 4 3 4 4 5% 6% 41%	2000
	21st to end	Day	21% 8% 2 6% 3 4 5% 3 4 6% 37%	2081
November	1st to 10th	Day	20% 8% 3 7% 4 4 3 4 4 6% 37%	1851
	11th to 20th	Day	20% 8% 3 6% 3 3 4 4 5% 6% 38%	1682
	21st to end	Day	21% 12% 4 7% 5% 3 3 3 5% 6% 31%	1680
December	1st to 10th	Day	23% 9% 3 8% 4 4 4 4 5% 7% 29%	2690
	11th to 20th	Day	25% 10% 3 9% 5% 4 3 3 4 4 31%	2766
	21st to end	Day	22% 13% 4 8% 5% 4 4 3 4 4 28%	3553
January	1st to 10th	Night	16% 14% 4 9% 6% 5% 4 3 4 5% 29%	8651
	11th to 20th	Night	20% 16% 5% 10% 5% 4 4 3 4 5% 24%	8235
	21st to end	Night	13% 12% 4 8% 6% 5% 5% 4 6% 6% 31%	8480
February	1st to 10th	Night	20% 11% 4 9% 6% 5% 4 3 5% 6% 27%	2730
	11th to 20th	Night	17% 12% 4 8% 5% 6% 4 4 6% 5% 29%	2663
	21st to end	Night	16% 10% 3 8% 6% 4 4 4 5% 5% 33%	2078
March	1st to 10th	Night	27% 12% 3 8% 5% 4 3 2 4 5% 27%	5160
	11th to 20th	Night	18% 13% 4 7% 4 4 5% 3 5% 8% 28%	4979
	21st to end	Night	31% 9% 3 6% 3 4 4 3 4 5% 28%	5466
April	1st to 10th	Night	24% 12% 2 6% 4 3 4 3 5% 5% 31%	2079
	11th to 20th	Night	23% 9% 2 6% 4 4 4 3 6% 7% 32%	1778
	21st to end	Night	27% 9% 3 6% 4 4 3 3 5% 6% 30%	1800
May	1st to 10th	Night	28% 12% 4 8% 4 3 3 2 4 5% 27%	4054
	11th to 20th	Night	22% 10% 3 6% 4 4 4 3 5% 6% 32%	3902
	21st to end	Night	18% 13% 4 8% 5% 4 4 3 6% 7% 30%	3907
June	1st to 10th	Night	26% 10% 3 7% 5% 4 3 4 5% 7% 27%	1400
	11th to 20th	Night	21% 10% 3 7% 5% 3 4 3 5% 4 35%	1400
	21st to end	Night	28% 11% 3 7% 5% 3 3 3 5% 6% 26%	1400
July	1st to 10th	Night	19% 15% 5% 10% 6% 5% 5% 4 6% 6% 19%	3160
	11th to 20th	Night	20% 18% 5% 7% 4 4 4 4 5% 6% 24%	3395
	21st to end	Night	14% 12% 5% 8% 4 4 4 3 5% 8% 34%	4309
August	1st to 10th	Night	21% 15% 4 8% 4 3 4 3 5% 7% 25%	2915
	11th to 20th	Night	15% 13% 5% 7% 5% 5% 5% 3 5% 8% 29%	2872
	21st to end	Night	11% 10% 4 8% 4 4 4 2 5% 6% 44%	3223
September	1st to 10th	Night	15% 9% 2 5% 3 4 3 3 5% 8% 43%	2053
	11th to 20th	Night	16% 7% 2 5% 4 4 4 3 4 6% 46%	2200
	21st to end	Night	19% 7% 2 6% 4 3 3 3 4 7% 43%	2200
October	1st to 10th	Night	18% 6% 2 6% 4 3 5% 3 4 7% 42%	2342
	11th to 20th	Night	17% 8% 2 6% 4 4 4 3 5% 8% 40%	2400
	21st to end	Night	22% 10% 3 6% 4 4 3 3 4 5% 35%	2755
November	1st to 10th	Night	21% 8% 2 5% 5% 4 4 3 5% 6% 38%	2667
	11th to 20th	Night	19% 10% 3 6% 5% 4 4 4 4 7% 34%	2936
	21st to end	Night	20% 11% 4 7% 5% 4 5% 4 5% 6% 30%	2940
December	1st to 10th	Night	19% 11% 4 8% 5% 4 4 3 6% 7% 28%	4720
	11th to 20th	Night	23% 11% 3 7% 4 4 4 3 5% 5% 31%	5657
	21st to end	Night	23% 13% 4 8% 6% 4 4 3 4 5% 28%	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% 5% 13% 17% 4 1	4248
	11th to 20th	Day	61% 3 8% 18% 9% 1	4680
	21st to end	Day	62% 5% 10% 11% 9% 2	5698
February	1st to 10th	Day	61% 6% 11% 14% 7% 1	1890
	11th to 20th	Day	57% 6% 12% 17% 7% 1	1851
	21st to end	Day	50% 6% 13% 20% 9% 2	1725
March	1st to 10th	Day	60% 4 10% 12% 10% 4	4729
	11th to 20th	Day	51% 7% 15% 17% 9% 1	4980
	21st to end	Day	58% 4 7% 16% 14% 1	5466
April	1st to 10th	Day	52% 4 9% 16% 16% 3	2316
	11th to 20th	Day	45% 4 11% 24% 14% 2	2572
	21st to end	Day	46% 4 9% 23% 15% 2	2600
May	1st to 10th	Day	61% 5% 11% 16% 6% 1	5897
	11th to 20th	Day	51% 6% 12% 21% 7% 2	6000
	21st to end	Day	52% 6% 12% 17% 11% 1	7030
June	1st to 10th	Day	52% 5% 11% 21% 10% 1	3000
	11th to 20th	Day	48% 5% 11% 20% 14% 2	3000
	21st to end	Day	56% 6% 9% 17% 10% 1	3000
July	1st to 10th	Day	57% 7% 11% 15% 9%	6745
	11th to 20th	Day	54% 7% 12% 18% 8% 1	6477
	21st to end	Day	44% 7% 14% 22% 12%	6312
August	1st to 10th	Day	55% 7% 9% 20% 9%	4222
	11th to 20th	Day	48% 6% 17% 20% 9%	4214
	21st to end	Day	33% 6% 12% 27% 21% 1	4675
September	1st to 10th	Day	38% 5% 12% 26% 18% 1	2345
	11th to 20th	Day	37% 5% 11% 27% 19% 2	2200
	21st to end	Day	40% 4 10% 29% 17% 1	2200
October	1st to 10th	Day	44% 6% 11% 27% 11% 1	3343
	11th to 20th	Day	33% 3 11% 36% 17%	3240
	21st to end	Day	38% 4 17% 24% 15% 2	3344
November	1st to 10th	Day	50% 5% 12% 21% 11% 1	1851
	11th to 20th	Day	48% 6% 13% 22% 10% 1	1682
	21st to end	Day	56% 5% 15% 19% 5%	1680
December	1st to 10th	Day	56% 7% 11% 19% 7%	2690
	11th to 20th	Day	59% 5% 11% 12% 10% 3	2766
	21st to end	Day	61% 6% 11% 13% 8% 1	3553
January	1st to 10th	Night	60% 7% 10% 18% 5%	8651
	11th to 20th	Night	64% 5% 8% 14% 8% 1	8280
	21st to end	Night	57% 5% 8% 15% 11% 3	8480
February	1st to 10th	Night	61% 6% 11% 14% 8% 1	2730
	11th to 20th	Night	58% 6% 9% 17% 8% 1	2666
	21st to end	Night	54% 5% 10% 19% 10% 2	2078
March	1st to 10th	Night	61% 3 8% 12% 12% 4	5169
	11th to 20th	Night	53% 7% 17% 15% 7% 1	4980
	21st to end	Night	60% 3 6% 18% 12% 1	5466
April	1st to 10th	Night	56% 5% 8% 15% 14% 3	2079
	11th to 20th	Night	51% 5% 10% 20% 13% 1	1778
	21st to end	Night	55% 4 8% 17% 14% 2	1800
May	1st to 10th	Night	60% 4 11% 15% 8% 1	4060
	11th to 20th	Night	52% 6% 12% 19% 8% 2	3903
	21st to end	Night	53% 6% 12% 20% 8% 1	3908
June	1st to 10th	Night	57% 6% 9% 20% 7% 1	1400
	11th to 20th	Night	51% 5% 9% 22% 11% 2	1400
	21st to end	Night	59% 5% 7% 18% 8% 3	1400
July	1st to 10th	Night	63% 7% 9% 13% 8%	3125
	11th to 20th	Night	59% 7% 10% 14% 10% 1	3352
	21st to end	Night	49% 5% 11% 21% 12% 2	4180
August	1st to 10th	Night	59% 5% 9% 19% 7%	2903
	11th to 20th	Night	53% 6% 15% 20% 7%	2899
	21st to end	Night	41% 5% 8% 27% 17% 2	3223
September	1st to 10th	Night	40% 6% 9% 26% 18% 1	2053
	11th to 20th	Night	40% 4 10% 26% 19% 2	2200
	21st to end	Night	42% 4 9% 26% 18% 1	2200
October	1st to 10th	Night	42% 4 13% 26% 13% 1	3836
	11th to 20th	Night	35% 4 12% 27% 21%	3899
	21st to end	Night	44% 4 10% 26% 14% 2	4442
November	1st to 10th	Night	48% 5% 13% 20% 13% 1	2667
	11th to 20th	Night	51% 7% 12% 18% 11% 1	2936
	21st to end	Night	56% 6% 14% 16% 6% 1	2940
December	1st to 10th	Night	57% 6% 8% 22% 7%	4720
	11th to 20th	Night	56% 5% 12% 16% 9% 2	5658
	21st to end	Night	60% 6% 12% 14% 8% 1	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	30% 14% 34% 15% 7%	220
	11th to 20th	Day	29% 15% 32% 18% 6%	220
	21st to end	Day	22% 13% 38% 22% 4	442
February	1st to 10th	Day	25% 14% 33% 20% 7%	430
	11th to 20th	Day	24% 15% 35% 22% 4 1	426
	21st to end	Day	19% 14% 32% 27% 7%	443
March	1st to 10th	Day	22% 14% 34% 24% 6%	508
	11th to 20th	Day	21% 14% 29% 25% 9% 1	500
	21st to end	Day	26% 9% 31% 25% 8% 1	550
April	1st to 10th	Day	28% 11% 27% 27% 5% 1	500
	11th to 20th	Day	24% 7% 29% 28% 11% 1	492
	21st to end	Day	24% 5% 26% 32% 11% 2	500
May	1st to 10th	Day	27% 4 25% 33% 10% 2	503
	11th to 20th	Day	23% 3 18% 36% 18% 1	584
	21st to end	Day	29% 3 18% 35% 13% 2	790
June	1st to 10th	Day	24% 3 17% 36% 16% 3	730
	11th to 20th	Day	22% 4 15% 34% 21% 3	730
	21st to end	Day	33% 2 12% 33% 15% 5%	730
July	1st to 10th	Day	26% 3 11% 37% 21% 2	720
	11th to 20th	Day	24% 4 7% 35% 26% 4	612
	21st to end	Day	19% 3 12% 38% 24% 3	576
August	1st to 10th	Day	17% 4 9% 37% 28% 6%	526
	11th to 20th	Day	22% 3 8% 34% 27% 6%	519
	21st to end	Day	17% 3 13% 36% 27% 5%	583
September	1st to 10th	Day	17% 2 12% 41% 24% 3	530
	11th to 20th	Day	20% 3 18% 29% 24% 6%	530
	21st to end	Day	18% 2 19% 36% 19% 6%	530
October	1st to 10th	Day	17% 7% 20% 33% 19% 4	450
	11th to 20th	Day	19% 6% 26% 30% 16% 3	420
	21st to end	Day	23% 10% 26% 28% 10% 2	462
November	1st to 10th	Day	24% 12% 26% 27% 9% 2	425
	11th to 20th	Day	25% 14% 31% 20% 8%	430
	21st to end	Day	28% 15% 32% 20% 5% 1	430
December	1st to 10th	Day	31% 10% 32% 21% 5%	430
	11th to 20th	Day	33% 14% 32% 18% 3	272
	21st to end	Day	24% 14% 36% 19% 5% 2	242
January	1st to 10th	Night	29% 17% 30% 19% 4	917
	11th to 20th	Night	29% 17% 31% 18% 5%	840
	21st to end	Night	22% 18% 36% 19% 4	924
February	1st to 10th	Night	26% 19% 32% 19% 5%	840
	11th to 20th	Night	24% 20% 33% 18% 4 1	823
	21st to end	Night	20% 17% 33% 24% 5%	692
March	1st to 10th	Night	25% 14% 34% 23% 2	809
	11th to 20th	Night	23% 13% 31% 26% 8%	800
	21st to end	Night	25% 11% 30% 25% 8% 1	880
April	1st to 10th	Night	29% 11% 30% 23% 6%	734
	11th to 20th	Night	26% 6% 29% 31% 9% 1	594
	21st to end	Night	30% 4 26% 28% 11% 2	600
May	1st to 10th	Night	28% 3 24% 32% 11% 2	600
	11th to 20th	Night	30% 4 20% 33% 12% 1	592
	21st to end	Night	25% 3 20% 37% 13% 2	634
June	1st to 10th	Night	30% 4 17% 33% 16% 1	400
	11th to 20th	Night	26% 3 14% 37% 19% 1	400
	21st to end	Night	32% 2 10% 37% 17% 3	400
July	1st to 10th	Night	28% 3 9% 35% 24% 1	390
	11th to 20th	Night	29% 2 9% 36% 22% 3	388
	21st to end	Night	27% 2 9% 38% 23% 2	602
August	1st to 10th	Night	19% 3 8% 40% 27% 2	598
	11th to 20th	Night	25% 3 10% 33% 27% 3	592
	21st to end	Night	18% 2 11% 40% 25% 5%	660
September	1st to 10th	Night	20% 3 14% 40% 21% 3	668
	11th to 20th	Night	20% 4 17% 29% 25% 5%	800
	21st to end	Night	23% 3 19% 32% 19% 5%	800
October	1st to 10th	Night	22% 5% 20% 32% 18% 3	800
	11th to 20th	Night	20% 9% 27% 27% 15% 3	800
	21st to end	Night	29% 11% 28% 23% 9%	880
November	1st to 10th	Night	25% 11% 30% 24% 9% 1	820
	11th to 20th	Night	24% 15% 32% 20% 8% 1	948
	21st to end	Night	27% 16% 30% 18% 7% 1	950
December	1st to 10th	Night	34% 13% 29% 19% 4	950
	11th to 20th	Night	30% 20% 32% 15% 3	950
	21st to end	Night	29% 19% 29% 18% 5% 1	1045

Page generated at 2026-02-28 02:40:20. Version ac07

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