Bangor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bangor clear sky chart from 2005-11-06 to 2026-10-29.

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% 8% 3 7% 4 4 4 4 5% 7% 36%	149150
	Night	18% 9% 3 7% 4 4 4 4 5% 6% 36%	142953
Transparency	Day	46% 6% 12% 21% 13% 2	152671
	Night	47% 6% 12% 21% 13% 2	147522
Seeing	Day	25% 17% 32% 18% 7% 1	18367
	Night	23% 14% 32% 24% 6%	26601

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	14% 11% 4 9% 5% 5% 5% 3 5% 5% 35%	4661
	11th to 20th	Day	16% 11% 4 8% 5% 5% 4 2 4 5% 37%	4650
	21st to end	Day	10% 9% 3 6% 4 5% 5% 4 5% 6% 44%	5200
February	1st to 10th	Day	16% 10% 3 7% 5% 4 4 4 5% 7% 35%	1890
	11th to 20th	Day	13% 11% 3 8% 6% 5% 5% 3 5% 6% 36%	1952
	21st to end	Day	13% 11% 2 8% 6% 5% 4 4 4 6% 36%	1730
March	1st to 10th	Day	24% 12% 3 10% 5% 4 4 2 4 4 28%	4614
	11th to 20th	Day	19% 12% 3 9% 4 4 4 3 4 6% 31%	5090
	21st to end	Day	27% 10% 3 7% 3 4 4 3 5% 6% 29%	5587
April	1st to 10th	Day	22% 11% 3 8% 5% 4 3 3 4 6% 31%	2499
	11th to 20th	Day	20% 9% 2 6% 4 4 4 3 5% 6% 37%	2680
	21st to end	Day	24% 9% 2 6% 4 4 3 3 4 5% 35%	2730
May	1st to 10th	Day	28% 10% 3 7% 4 4 4 3 5% 6% 26%	7639
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 7% 32%	7625
	21st to end	Day	17% 8% 3 7% 5% 5% 5% 4 5% 7% 34%	9349
June	1st to 10th	Day	23% 8% 3 7% 5% 4 4 4 5% 7% 31%	3150
	11th to 20th	Day	18% 7% 2 6% 5% 4 4 4 6% 8% 35%	3150
	21st to end	Day	24% 8% 2 6% 4 4 4 5% 6% 6% 30%	3150
July	1st to 10th	Day	11% 7% 3 7% 5% 5% 6% 5% 7% 10% 34%	8585
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	8280
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 9% 43%	8880
August	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 4 6% 8% 34%	6015
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 8% 32%	5953
	21st to end	Day	12% 5% 2 7% 4 4 4 3 7% 8% 44%	6577
September	1st to 10th	Day	12% 5% 2 5% 5% 4 4 4 5% 8% 48%	2417
	11th to 20th	Day	14% 5% 2 5% 4 4 3 2 4 5% 52%	2310
	21st to end	Day	16% 7% 3 5% 4 4 4 3 6% 7% 43%	2310
October	1st to 10th	Day	17% 6% 2 6% 4 4 4 3 5% 6% 42%	2249
	11th to 20th	Day	20% 6% 2 6% 4 4 4 3 4 6% 41%	2080
	21st to end	Day	21% 9% 3 7% 4 4 3 3 5% 6% 36%	2052
November	1st to 10th	Day	17% 7% 2 6% 5% 4 5% 4 6% 6% 38%	1851
	11th to 20th	Day	19% 7% 2 6% 3 4 5% 4 4 7% 39%	1837
	21st to end	Day	22% 8% 3 5% 4 3 3 3 5% 5% 38%	1680
December	1st to 10th	Day	17% 11% 2 5% 4 3 4 3 5% 7% 38%	2468
	11th to 20th	Day	19% 8% 2 5% 4 4 3 3 4 5% 43%	2688
	21st to end	Day	21% 11% 4 6% 4 3 4 3 5% 5% 35%	3572
January	1st to 10th	Night	12% 12% 4 10% 5% 4 4 3 4 6% 35%	8234
	11th to 20th	Night	16% 13% 5% 9% 5% 5% 5% 4 5% 6% 28%	8235
	21st to end	Night	10% 11% 3 8% 4 4 5% 4 6% 7% 38%	8979
February	1st to 10th	Night	14% 11% 4 8% 5% 5% 5% 4 6% 6% 33%	2730
	11th to 20th	Night	12% 11% 3 8% 5% 5% 4 3 5% 5% 39%	2551
	21st to end	Night	15% 12% 2 7% 6% 4 4 3 5% 5% 37%	2076
March	1st to 10th	Night	27% 12% 3 7% 4 4 3 3 4 4 29%	5445
	11th to 20th	Night	18% 11% 3 7% 5% 5% 5% 5% 5% 7% 30%	5089
	21st to end	Night	26% 10% 3 7% 4 4 4 3 6% 6% 27%	5587
April	1st to 10th	Night	23% 11% 3 7% 3 3 3 3 4 5% 34%	2119
	11th to 20th	Night	21% 8% 2 7% 5% 4 4 5% 5% 7% 33%	1888
	21st to end	Night	25% 8% 3 5% 4 3 4 3 6% 5% 34%	1890
May	1st to 10th	Night	28% 9% 3 6% 3 3 3 3 5% 7% 29%	5259
	11th to 20th	Night	21% 7% 2 7% 5% 4 5% 4 6% 8% 31%	5235
	21st to end	Night	15% 8% 3 7% 4 5% 5% 4 6% 7% 36%	4881
June	1st to 10th	Night	21% 9% 3 7% 4 4 5% 4 6% 8% 30%	1470
	11th to 20th	Night	16% 7% 2 6% 4 4 4 5% 7% 10% 35%	1470
	21st to end	Night	22% 9% 2 7% 4 3 4 4 7% 7% 30%	1470
July	1st to 10th	Night	11% 7% 3 8% 6% 6% 6% 5% 7% 9% 34%	4385
	11th to 20th	Night	12% 7% 3 7% 4 5% 5% 4 6% 8% 38%	4680
	21st to end	Night	13% 6% 2 5% 4 4 5% 4 6% 8% 44%	5135
August	1st to 10th	Night	15% 8% 3 9% 5% 5% 5% 4 6% 7% 33%	4135
	11th to 20th	Night	15% 8% 3 7% 4 4 5% 4 6% 8% 35%	4092
	21st to end	Night	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	4531
September	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 5% 7% 49%	2202
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 5% 6% 52%	2310
	21st to end	Night	18% 6% 2 5% 4 3 4 3 5% 7% 43%	2310
October	1st to 10th	Night	17% 5% 2 5% 4 4 4 4 5% 6% 43%	2370
	11th to 20th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 41%	2536
	21st to end	Night	23% 8% 3 6% 3 4 4 3 4 6% 36%	2965
November	1st to 10th	Night	18% 7% 2 6% 4 4 3 3 5% 5% 41%	2667
	11th to 20th	Night	18% 8% 2 5% 4 5% 4 4 5% 7% 39%	2779
	21st to end	Night	19% 9% 3 5% 4 3 4 4 5% 6% 37%	2940
December	1st to 10th	Night	17% 9% 3 7% 4 4 5% 4 6% 6% 35%	4924
	11th to 20th	Night	22% 8% 2 5% 3 3 4 3 4 5% 41%	5741
	21st to end	Night	22% 10% 3 7% 4 4 4 3 5% 5% 34%	7643

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	50% 4 12% 22% 10% 1	4662
	11th to 20th	Day	49% 4 11% 23% 11% 2	4680
	21st to end	Day	41% 5% 10% 21% 19% 4	5200
February	1st to 10th	Day	48% 6% 12% 19% 13% 3	1890
	11th to 20th	Day	49% 5% 11% 21% 12% 2	1960
	21st to end	Day	48% 5% 11% 19% 11% 5%	1730
March	1st to 10th	Day	60% 4 8% 9% 14% 5%	4617
	11th to 20th	Day	51% 6% 15% 16% 10% 2	5090
	21st to end	Day	56% 4 7% 16% 15% 3	5587
April	1st to 10th	Day	53% 5% 9% 15% 13% 4	2499
	11th to 20th	Day	48% 6% 10% 22% 13% 2	2680
	21st to end	Day	51% 4 8% 18% 15% 4	2730
May	1st to 10th	Day	57% 7% 12% 16% 8% 1	7651
	11th to 20th	Day	48% 8% 14% 19% 8% 2	7629
	21st to end	Day	47% 8% 12% 18% 13% 1	9350
June	1st to 10th	Day	52% 7% 12% 19% 10% 1	3150
	11th to 20th	Day	45% 7% 12% 19% 15% 2	3150
	21st to end	Day	52% 8% 11% 18% 9% 2	3150
July	1st to 10th	Day	43% 6% 15% 25% 10%	8514
	11th to 20th	Day	37% 6% 15% 24% 16% 1	8205
	21st to end	Day	39% 5% 12% 29% 14% 1	8683
August	1st to 10th	Day	46% 7% 17% 22% 7% 1	6002
	11th to 20th	Day	47% 8% 15% 21% 9%	5992
	21st to end	Day	36% 6% 15% 26% 17% 1	6577
September	1st to 10th	Day	33% 6% 15% 27% 17% 1	2417
	11th to 20th	Day	35% 4 10% 26% 22% 3	2310
	21st to end	Day	40% 5% 11% 26% 16% 2	2310
October	1st to 10th	Day	51% 6% 9% 21% 12% 1	3600
	11th to 20th	Day	37% 4 11% 31% 17% 1	3308
	21st to end	Day	36% 5% 15% 23% 19% 2	3252
November	1st to 10th	Day	44% 6% 14% 21% 13% 1	1851
	11th to 20th	Day	44% 5% 12% 21% 15% 3	1837
	21st to end	Day	47% 5% 16% 23% 8% 1	1680
December	1st to 10th	Day	45% 4 18% 19% 13% 1	2468
	11th to 20th	Day	45% 4 13% 17% 15% 7%	2688
	21st to end	Day	51% 5% 10% 19% 12% 3	3572
January	1st to 10th	Night	48% 5% 12% 22% 12% 1	8234
	11th to 20th	Night	55% 5% 12% 16% 10% 2	8280
	21st to end	Night	43% 4 9% 22% 16% 5%	8979
February	1st to 10th	Night	49% 6% 11% 19% 13% 2	2730
	11th to 20th	Night	47% 5% 10% 21% 15% 2	2554
	21st to end	Night	47% 6% 9% 20% 14% 4	2076
March	1st to 10th	Night	59% 3 7% 13% 13% 5%	5455
	11th to 20th	Night	49% 9% 19% 15% 7% 1	5090
	21st to end	Night	55% 5% 7% 16% 15% 2	5587
April	1st to 10th	Night	54% 3 10% 14% 16% 3	2119
	11th to 20th	Night	49% 6% 11% 20% 13% 2	1888
	21st to end	Night	50% 6% 10% 17% 14% 3	1890
May	1st to 10th	Night	54% 6% 15% 14% 11% 1	5265
	11th to 20th	Night	48% 8% 14% 21% 8% 1	5236
	21st to end	Night	44% 8% 14% 21% 13%	4882
June	1st to 10th	Night	50% 9% 12% 20% 9%	1470
	11th to 20th	Night	42% 9% 17% 20% 11% 2	1470
	21st to end	Night	51% 10% 12% 17% 8% 2	1470
July	1st to 10th	Night	46% 6% 14% 24% 9%	4346
	11th to 20th	Night	42% 6% 14% 27% 11%	4632
	21st to end	Night	37% 6% 16% 29% 11% 1	5018
August	1st to 10th	Night	49% 8% 15% 20% 8%	4123
	11th to 20th	Night	45% 7% 18% 21% 9%	4119
	21st to end	Night	38% 8% 16% 23% 14% 1	4531
September	1st to 10th	Night	34% 7% 14% 30% 14% 1	2202
	11th to 20th	Night	32% 6% 12% 29% 20% 2	2310
	21st to end	Night	40% 7% 10% 27% 15% 2	2310
October	1st to 10th	Night	42% 6% 14% 23% 14% 1	3799
	11th to 20th	Night	36% 4 11% 29% 18% 1	4047
	21st to end	Night	40% 4 12% 27% 14% 3	4715
November	1st to 10th	Night	44% 5% 13% 22% 14% 1	2667
	11th to 20th	Night	45% 5% 11% 22% 16% 2	2779
	21st to end	Night	45% 6% 16% 19% 12% 1	2940
December	1st to 10th	Night	47% 5% 11% 26% 11%	4924
	11th to 20th	Night	46% 4 11% 20% 17% 2	5742
	21st to end	Night	51% 5% 10% 17% 15% 1	7643

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% 17% 34% 16% 2	220
	11th to 20th	Day	31% 21% 35% 10% 2 1	220
	21st to end	Day	21% 24% 37% 15% 3	266
February	1st to 10th	Day	28% 19% 29% 20% 4	430
	11th to 20th	Day	27% 24% 36% 10% 2	484
	21st to end	Day	26% 24% 32% 17% 2	446
March	1st to 10th	Day	31% 23% 31% 13% 2	540
	11th to 20th	Day	28% 25% 30% 13% 4 1	540
	21st to end	Day	35% 22% 26% 11% 4 2	594
April	1st to 10th	Day	37% 22% 26% 10% 4 1	540
	11th to 20th	Day	35% 24% 27% 10% 5% 1	532
	21st to end	Day	29% 22% 29% 14% 4 1	540
May	1st to 10th	Day	33% 20% 31% 13% 3 1	543
	11th to 20th	Day	25% 19% 35% 16% 5% 1	567
	21st to end	Day	24% 19% 34% 17% 5%	729
June	1st to 10th	Day	25% 15% 31% 20% 8% 1	780
	11th to 20th	Day	23% 15% 30% 21% 10% 1	780
	21st to end	Day	28% 12% 30% 21% 8% 1	780
July	1st to 10th	Day	19% 12% 38% 21% 10% 1	674
	11th to 20th	Day	18% 12% 40% 21% 8% 2	564
	21st to end	Day	16% 13% 37% 24% 8% 3	620
August	1st to 10th	Day	14% 11% 35% 29% 9% 2	566
	11th to 20th	Day	17% 10% 33% 26% 11% 3	559
	21st to end	Day	16% 13% 34% 24% 10% 3	627
September	1st to 10th	Day	15% 14% 36% 23% 10% 2	570
	11th to 20th	Day	21% 11% 29% 20% 13% 6%	570
	21st to end	Day	18% 15% 33% 19% 10% 5%	570
October	1st to 10th	Day	21% 17% 26% 20% 12% 3	534
	11th to 20th	Day	25% 17% 28% 20% 8% 2	450
	21st to end	Day	29% 17% 28% 19% 6% 1	486
November	1st to 10th	Day	27% 18% 26% 22% 6% 2	425
	11th to 20th	Day	29% 17% 33% 13% 7%	430
	21st to end	Day	30% 20% 27% 19% 4	430
December	1st to 10th	Day	28% 19% 35% 14% 4	299
	11th to 20th	Day	35% 25% 28% 10% 1	220
	21st to end	Day	34% 23% 27% 12% 4 1	242
January	1st to 10th	Night	23% 20% 34% 20% 3	840
	11th to 20th	Night	26% 19% 32% 20% 3	840
	21st to end	Night	19% 20% 37% 20% 4	924
February	1st to 10th	Night	23% 19% 34% 20% 3	840
	11th to 20th	Night	21% 22% 37% 17% 2	823
	21st to end	Night	24% 16% 37% 20% 3	692
March	1st to 10th	Night	27% 17% 35% 20% 1	840
	11th to 20th	Night	25% 20% 32% 19% 4	840
	21st to end	Night	26% 18% 31% 20% 5%	924
April	1st to 10th	Night	30% 19% 32% 17% 2	840
	11th to 20th	Night	24% 17% 37% 18% 4	644
	21st to end	Night	30% 13% 32% 20% 5%	630
May	1st to 10th	Night	26% 14% 33% 23% 3	630
	11th to 20th	Night	26% 12% 36% 23% 4	622
	21st to end	Night	19% 11% 36% 28% 6%	489
June	1st to 10th	Night	24% 8% 33% 30% 6%	420
	11th to 20th	Night	19% 7% 34% 32% 8%	420
	21st to end	Night	27% 6% 25% 36% 5%	420
July	1st to 10th	Night	16% 5% 37% 34% 8%	410
	11th to 20th	Night	17% 3 30% 39% 10%	408
	21st to end	Night	18% 4 30% 37% 10% 1	473
August	1st to 10th	Night	16% 5% 31% 39% 9%	628
	11th to 20th	Night	15% 6% 32% 36% 10% 1	622
	21st to end	Night	16% 7% 28% 37% 11% 1	693
September	1st to 10th	Night	17% 5% 33% 33% 11% 1	840
	11th to 20th	Night	17% 10% 27% 28% 16% 3	840
	21st to end	Night	19% 9% 31% 30% 11% 1	840
October	1st to 10th	Night	20% 11% 28% 27% 13%	840
	11th to 20th	Night	22% 13% 30% 25% 9% 1	840
	21st to end	Night	28% 15% 30% 22% 5%	913
November	1st to 10th	Night	25% 14% 31% 23% 6% 1	820
	11th to 20th	Night	24% 16% 32% 20% 7% 1	867
	21st to end	Night	27% 18% 30% 20% 4 1	950
December	1st to 10th	Night	28% 13% 34% 20% 5%	950
	11th to 20th	Night	25% 22% 32% 18% 3	950
	21st to end	Night	28% 19% 32% 18% 3	1039

Page generated at 2026-10-26 04:37:53. Version ac07

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