Bar Harbor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bar Harbor clear sky chart from 2005-11-06 to 2025-05-26.

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 6% 4 4 4 3 5% 7% 38%	113405
	Night	19% 9% 3 6% 4 4 4 3 5% 7% 36%	115914
Transparency	Day	45% 7% 13% 20% 12% 2	116986
	Night	47% 6% 13% 20% 13% 2	120498
Seeing	Day	23% 12% 29% 25% 9% 1	16572
	Night	24% 14% 28% 25% 9% 1	24953

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% 9% 3 7% 5% 5% 5% 4 5% 7% 35%	3575
	11th to 20th	Day	14% 9% 3 6% 4 4 5% 3 4 6% 42%	3570
	21st to end	Day	13% 11% 3 7% 3 4 3 3 5% 6% 41%	4164
February	1st to 10th	Day	16% 13% 3 6% 5% 4 5% 5% 6% 6% 31%	1800
	11th to 20th	Day	15% 8% 3 8% 4 5% 5% 4 6% 7% 36%	1835
	21st to end	Day	13% 10% 4 7% 5% 5% 5% 3 6% 6% 36%	1650
March	1st to 10th	Day	24% 12% 3 6% 4 4 4 4 5% 5% 31%	4567
	11th to 20th	Day	21% 11% 2 6% 4 4 4 3 5% 6% 35%	4980
	21st to end	Day	29% 9% 3 6% 4 3 4 3 5% 5% 30%	5466
April	1st to 10th	Day	20% 11% 3 6% 5% 4 4 4 4 6% 34%	2337
	11th to 20th	Day	20% 8% 2 6% 4 3 3 3 5% 6% 38%	2572
	21st to end	Day	20% 9% 2 5% 4 4 4 3 5% 6% 38%	2600
May	1st to 10th	Day	20% 9% 3 7% 5% 4 3 3 6% 7% 32%	4236
	11th to 20th	Day	18% 7% 2 7% 4 4 4 4 5% 7% 37%	4211
	21st to end	Day	18% 9% 3 6% 4 5% 4 4 6% 7% 34%	4981
June	1st to 10th	Day	23% 8% 2 7% 5% 3 4 3 5% 7% 32%	2850
	11th to 20th	Day	19% 8% 2 5% 4 4 3 4 5% 7% 39%	2850
	21st to end	Day	26% 9% 2 7% 4 3 3 4 5% 6% 30%	2850
July	1st to 10th	Day	18% 8% 3 6% 4 4 5% 4 5% 9% 34%	4640
	11th to 20th	Day	17% 7% 2 5% 3 4 4 3 5% 9% 41%	4440
	21st to end	Day	20% 8% 2 6% 3 4 4 3 6% 7% 37%	4662
August	1st to 10th	Day	19% 9% 2 7% 4 4 4 4 5% 7% 35%	4105
	11th to 20th	Day	17% 9% 3 6% 5% 4 4 3 6% 7% 35%	4045
	21st to end	Day	10% 5% 2 5% 4 3 3 3 6% 8% 51%	4532
September	1st to 10th	Day	12% 5% 2 5% 3 4 3 4 5% 7% 49%	2186
	11th to 20th	Day	13% 6% 2 4 3 3 4 3 4 6% 52%	2090
	21st to end	Day	18% 6% 2 5% 4 3 4 3 5% 6% 43%	2090
October	1st to 10th	Day	16% 9% 2 6% 3 3 4 4 5% 7% 41%	2014
	11th to 20th	Day	18% 6% 2 5% 4 3 3 3 5% 7% 43%	1900
	21st to end	Day	22% 9% 2 4 4 4 3 2 5% 5% 39%	1905
November	1st to 10th	Day	18% 6% 2 7% 4 4 3 3 5% 6% 42%	1761
	11th to 20th	Day	20% 6% 1 5% 3 3 4 4 5% 7% 41%	1726
	21st to end	Day	20% 10% 3 6% 3 3 4 3 4 6% 39%	1600
December	1st to 10th	Day	19% 10% 2 5% 2 3 4 3 5% 6% 42%	2521
	11th to 20th	Day	21% 8% 2 5% 3 3 4 3 4 5% 40%	2618
	21st to end	Day	21% 13% 4 6% 3 2 3 2 4 5% 38%	3476
January	1st to 10th	Night	12% 11% 3 8% 5% 4 4 3 5% 7% 39%	6367
	11th to 20th	Night	14% 11% 4 9% 5% 4 5% 3 5% 6% 33%	6315
	21st to end	Night	12% 10% 3 8% 4 4 4 3 6% 7% 39%	6789
February	1st to 10th	Night	18% 10% 4 7% 5% 4 5% 3 5% 7% 32%	2600
	11th to 20th	Night	14% 11% 3 7% 4 4 4 3 6% 6% 38%	2448
	21st to end	Night	15% 10% 3 7% 5% 4 4 3 5% 7% 38%	1980
March	1st to 10th	Night	26% 11% 3 6% 5% 4 3 2 4 4 31%	5273
	11th to 20th	Night	17% 12% 3 7% 4 5% 5% 4 6% 7% 31%	4979
	21st to end	Night	28% 9% 2 6% 4 4 4 3 5% 6% 30%	5466
April	1st to 10th	Night	22% 12% 2 7% 4 4 3 3 5% 6% 33%	2060
	11th to 20th	Night	22% 9% 3 6% 5% 3 3 3 6% 7% 34%	1778
	21st to end	Night	24% 10% 3 6% 4 4 3 3 4 5% 34%	1800
May	1st to 10th	Night	24% 8% 3 7% 4 3 4 3 5% 8% 33%	2924
	11th to 20th	Night	19% 7% 3 7% 5% 5% 5% 4 6% 9% 30%	2903
	21st to end	Night	16% 11% 3 8% 5% 4 4 3 5% 6% 33%	2743
June	1st to 10th	Night	26% 11% 2 5% 4 4 4 5% 4 8% 27%	1330
	11th to 20th	Night	20% 10% 3 5% 3 4 3 4 5% 7% 36%	1330
	21st to end	Night	28% 10% 2 6% 5% 3 4 3 5% 6% 28%	1330
July	1st to 10th	Night	19% 12% 3 7% 4 5% 6% 4 7% 7% 26%	2322
	11th to 20th	Night	20% 8% 2 6% 4 4 4 5% 5% 8% 34%	2520
	21st to end	Night	18% 8% 2 6% 5% 5% 5% 5% 6% 8% 34%	2859
August	1st to 10th	Night	23% 11% 3 7% 4 4 5% 4 5% 7% 28%	2825
	11th to 20th	Night	19% 10% 3 7% 4 4 4 5% 7% 8% 30%	2782
	21st to end	Night	10% 7% 2 6% 4 4 5% 3 5% 8% 45%	3124
September	1st to 10th	Night	15% 6% 2 5% 3 3 4 3 5% 6% 48%	1990
	11th to 20th	Night	17% 7% 2 4 3 3 3 3 4 6% 49%	2090
	21st to end	Night	19% 7% 2 5% 3 3 3 4 5% 6% 44%	2090
October	1st to 10th	Night	20% 6% 3 5% 3 4 4 3 5% 6% 40%	2165
	11th to 20th	Night	19% 6% 2 6% 4 4 4 4 4 6% 43%	2280
	21st to end	Night	23% 9% 2 6% 3 3 3 3 4 6% 38%	2688
November	1st to 10th	Night	18% 5% 2 5% 4 4 4 4 5% 7% 42%	2537
	11th to 20th	Night	17% 7% 2 6% 4 4 4 4 5% 6% 41%	2670
	21st to end	Night	19% 8% 2 6% 4 3 4 4 5% 7% 38%	2800
December	1st to 10th	Night	19% 9% 2 5% 4 3 4 4 6% 7% 36%	4664
	11th to 20th	Night	23% 8% 2 5% 3 3 3 3 4 5% 42%	5591
	21st to end	Night	22% 11% 3 6% 3 3 3 3 4 5% 37%	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	49% 6% 14% 25% 7%	3576
	11th to 20th	Day	43% 7% 15% 23% 11% 2	3600
	21st to end	Day	44% 7% 12% 18% 14% 5%	4164
February	1st to 10th	Day	53% 7% 12% 15% 10% 2	1800
	11th to 20th	Day	47% 7% 16% 16% 12% 2	1843
	21st to end	Day	47% 7% 11% 20% 11% 4	1650
March	1st to 10th	Day	54% 5% 10% 11% 15% 5%	4571
	11th to 20th	Day	48% 6% 16% 19% 10% 1	4980
	21st to end	Day	54% 5% 8% 16% 15% 3	5466
April	1st to 10th	Day	50% 5% 10% 17% 15% 3	2337
	11th to 20th	Day	44% 6% 11% 23% 13% 3	2572
	21st to end	Day	46% 6% 10% 19% 16% 3	2600
May	1st to 10th	Day	48% 10% 15% 19% 7% 1	4250
	11th to 20th	Day	43% 10% 16% 21% 9% 1	4215
	21st to end	Day	45% 10% 13% 18% 13% 1	4981
June	1st to 10th	Day	51% 7% 13% 19% 9%	2850
	11th to 20th	Day	46% 7% 12% 19% 14% 2	2850
	21st to end	Day	55% 7% 11% 16% 10% 2	2850
July	1st to 10th	Day	51% 8% 12% 18% 11%	4568
	11th to 20th	Day	42% 8% 17% 22% 11%	4365
	21st to end	Day	46% 8% 14% 21% 11% 1	4513
August	1st to 10th	Day	50% 7% 13% 22% 7%	4092
	11th to 20th	Day	47% 8% 17% 19% 9%	4084
	21st to end	Day	30% 7% 13% 27% 21% 1	4532
September	1st to 10th	Day	34% 7% 13% 26% 18% 2	2186
	11th to 20th	Day	34% 6% 13% 25% 19% 3	2090
	21st to end	Day	40% 7% 10% 26% 15% 1	2090
October	1st to 10th	Day	43% 8% 14% 22% 12% 1	3352
	11th to 20th	Day	30% 5% 10% 34% 21%	3140
	21st to end	Day	34% 5% 18% 23% 17% 3	3117
November	1st to 10th	Day	43% 6% 14% 23% 12% 1	1761
	11th to 20th	Day	42% 7% 10% 22% 16% 3	1726
	21st to end	Day	48% 6% 18% 21% 7% 1	1600
December	1st to 10th	Day	43% 7% 15% 22% 12% 1	2521
	11th to 20th	Day	47% 5% 14% 16% 12% 6%	2618
	21st to end	Day	50% 7% 12% 18% 11% 3	3476
January	1st to 10th	Night	45% 6% 15% 24% 9% 1	6367
	11th to 20th	Night	50% 8% 14% 19% 8% 1	6360
	21st to end	Night	45% 6% 12% 19% 15% 4	6789
February	1st to 10th	Night	53% 7% 13% 15% 11% 2	2600
	11th to 20th	Night	47% 7% 12% 18% 14% 2	2451
	21st to end	Night	48% 5% 11% 21% 12% 3	1980
March	1st to 10th	Night	56% 5% 8% 11% 13% 8%	5282
	11th to 20th	Night	47% 10% 21% 14% 7% 1	4980
	21st to end	Night	55% 4 7% 17% 16% 2	5466
April	1st to 10th	Night	52% 6% 9% 15% 16% 3	2060
	11th to 20th	Night	49% 5% 10% 20% 14% 2	1778
	21st to end	Night	52% 5% 10% 17% 13% 3	1800
May	1st to 10th	Night	50% 8% 16% 18% 8% 1	2930
	11th to 20th	Night	47% 12% 17% 16% 7% 1	2904
	21st to end	Night	48% 10% 15% 18% 9% 1	2744
June	1st to 10th	Night	54% 8% 11% 19% 7% 1	1330
	11th to 20th	Night	47% 8% 12% 20% 11% 2	1330
	21st to end	Night	57% 5% 9% 18% 9% 2	1330
July	1st to 10th	Night	55% 9% 11% 15% 9% 1	2284
	11th to 20th	Night	47% 8% 14% 21% 10%	2472
	21st to end	Night	47% 8% 13% 18% 13% 1	2768
August	1st to 10th	Night	57% 8% 11% 18% 7%	2813
	11th to 20th	Night	50% 8% 14% 20% 8%	2809
	21st to end	Night	37% 7% 12% 24% 21% 1	3124
September	1st to 10th	Night	35% 7% 14% 27% 17% 1	1990
	11th to 20th	Night	37% 5% 12% 26% 18% 2	2090
	21st to end	Night	39% 6% 11% 26% 17% 1	2090
October	1st to 10th	Night	40% 6% 15% 24% 14% 1	3607
	11th to 20th	Night	32% 5% 11% 28% 24% 1	3779
	21st to end	Night	39% 4 10% 29% 15% 3	4426
November	1st to 10th	Night	43% 6% 12% 25% 14% 1	2537
	11th to 20th	Night	45% 5% 12% 21% 14% 2	2670
	21st to end	Night	46% 7% 15% 19% 11% 1	2800
December	1st to 10th	Night	46% 6% 12% 25% 10%	4664
	11th to 20th	Night	46% 4 13% 20% 14% 2	5592
	21st to end	Night	49% 7% 12% 17% 14% 1	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	24% 29% 31% 12% 5%	200
	11th to 20th	Day	28% 24% 28% 17% 4 1	200
	21st to end	Day	20% 23% 33% 19% 5%	307
February	1st to 10th	Day	24% 24% 32% 17% 4	400
	11th to 20th	Day	23% 27% 37% 12% 2	438
	21st to end	Day	21% 20% 35% 21% 3	414
March	1st to 10th	Day	25% 21% 35% 17% 2	500
	11th to 20th	Day	22% 22% 31% 21% 4	500
	21st to end	Day	27% 18% 31% 17% 6% 1	550
April	1st to 10th	Day	28% 17% 35% 14% 3 1	500
	11th to 20th	Day	26% 14% 35% 18% 5%	492
	21st to end	Day	24% 9% 37% 23% 6% 1	500
May	1st to 10th	Day	24% 14% 33% 23% 4 1	503
	11th to 20th	Day	17% 8% 36% 29% 9% 1	527
	21st to end	Day	26% 6% 30% 26% 10% 1	672
June	1st to 10th	Day	25% 5% 28% 29% 11% 2	680
	11th to 20th	Day	24% 5% 24% 30% 15% 2	680
	21st to end	Day	29% 5% 25% 29% 11% 2	680
July	1st to 10th	Day	24% 4 25% 32% 15% 1	605
	11th to 20th	Day	19% 4 22% 38% 15% 2	484
	21st to end	Day	18% 5% 23% 39% 13% 2	532
August	1st to 10th	Day	15% 5% 25% 35% 18% 1	486
	11th to 20th	Day	20% 5% 20% 35% 16% 3	479
	21st to end	Day	16% 6% 22% 34% 19% 3	539
September	1st to 10th	Day	17% 3 25% 36% 17% 1	490
	11th to 20th	Day	18% 9% 26% 28% 13% 6%	490
	21st to end	Day	19% 5% 31% 28% 14% 3	490
October	1st to 10th	Day	18% 10% 25% 31% 15% 1	450
	11th to 20th	Day	19% 11% 33% 25% 10% 2	390
	21st to end	Day	28% 12% 31% 24% 5%	429
November	1st to 10th	Day	21% 20% 26% 25% 7% 1	395
	11th to 20th	Day	23% 22% 32% 18% 4 1	400
	21st to end	Day	26% 22% 29% 19% 4	400
December	1st to 10th	Day	28% 16% 34% 18% 4	350
	11th to 20th	Day	33% 23% 30% 12% 3	200
	21st to end	Day	29% 19% 30% 16% 5%	220
January	1st to 10th	Night	24% 24% 32% 17% 3	803
	11th to 20th	Night	27% 22% 32% 16% 4	800
	21st to end	Night	18% 26% 35% 17% 4	880
February	1st to 10th	Night	26% 23% 33% 15% 3	800
	11th to 20th	Night	23% 28% 32% 15% 2 1	783
	21st to end	Night	23% 18% 36% 20% 4	660
March	1st to 10th	Night	26% 17% 35% 20% 2	800
	11th to 20th	Night	22% 18% 31% 22% 7%	800
	21st to end	Night	24% 16% 32% 22% 6% 1	880
April	1st to 10th	Night	30% 14% 32% 20% 5%	800
	11th to 20th	Night	26% 9% 33% 26% 6%	594
	21st to end	Night	30% 9% 26% 26% 8% 1	600
May	1st to 10th	Night	28% 5% 30% 27% 9% 2	600
	11th to 20th	Night	26% 5% 28% 32% 9%	592
	21st to end	Night	25% 6% 23% 32% 12% 2	528
June	1st to 10th	Night	32% 5% 17% 33% 12% 1	380
	11th to 20th	Night	24% 4 20% 36% 15% 1	380
	21st to end	Night	34% 2 14% 36% 13% 1	380
July	1st to 10th	Night	25% 3 16% 39% 16% 1	370
	11th to 20th	Night	25% 4 14% 38% 18% 1	368
	21st to end	Night	24% 1 15% 38% 20% 1	486
August	1st to 10th	Night	23% 1 15% 41% 18% 1	568
	11th to 20th	Night	21% 4 15% 39% 20% 1	562
	21st to end	Night	17% 3 18% 36% 23% 3	627
September	1st to 10th	Night	18% 3 22% 37% 19% 2	731
	11th to 20th	Night	21% 5% 22% 29% 18% 5%	760
	21st to end	Night	20% 5% 24% 32% 15% 3	760
October	1st to 10th	Night	22% 7% 24% 28% 17% 2	760
	11th to 20th	Night	20% 11% 30% 24% 13% 2	760
	21st to end	Night	27% 16% 29% 21% 6%	836
November	1st to 10th	Night	22% 14% 29% 26% 9% 1	780
	11th to 20th	Night	21% 22% 30% 20% 6% 1	835
	21st to end	Night	25% 21% 32% 16% 6%	900
December	1st to 10th	Night	30% 17% 33% 16% 4	900
	11th to 20th	Night	27% 25% 30% 15% 2	900
	21st to end	Night	28% 21% 29% 18% 3	990

Page generated at 2025-05-23 09:20:58. Version ac07

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