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 2024-03-18.

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% 8% 3 5% 5% 3 4 4 5% 7% 38%	78336
	Night	20% 8% 3 6% 5% 3 4 4 5% 7% 36%	81442
Transparency	Day	46% 7% 13% 20% 12% 2	78044
	Night	48% 7% 13% 19% 12% 1	81269
Seeing	Day	23% 12% 29% 25% 9% 1	14975
	Night	25% 13% 28% 25% 9% 1	23426

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	19% 8% 3 6% 4 3 4 4 4 7% 38%	2495
	11th to 20th	Day	18% 8% 3 4 4 3 4 4 4 5% 44%	2520
	21st to end	Day	17% 10% 3 6% 5% 3 4 4 6% 7% 36%	2906
February	1st to 10th	Day	17% 12% 3 6% 5% 3 5% 5% 5% 7% 31%	1710
	11th to 20th	Day	15% 8% 4 7% 5% 4 5% 4 5% 7% 37%	1740
	21st to end	Day	14% 9% 4 6% 6% 3 5% 4 5% 7% 36%	1570
March	1st to 10th	Day	17% 10% 3 6% 5% 2 5% 4 5% 6% 36%	1934
	11th to 20th	Day	19% 6% 2 5% 4 3 4 5% 5% 7% 39%	2059
	21st to end	Day	19% 8% 3 6% 4 3 5% 4 4 5% 39%	2178
April	1st to 10th	Day	20% 10% 3 5% 5% 3 4 4 5% 6% 35%	2103
	11th to 20th	Day	19% 8% 3 5% 5% 2 3 4 5% 7% 39%	2312
	21st to end	Day	21% 9% 3 5% 5% 3 4 4 5% 6% 35%	2340
May	1st to 10th	Day	22% 9% 3 6% 5% 3 3 4 5% 6% 33%	2340
	11th to 20th	Day	20% 7% 2 5% 4 3 3 4 4 6% 41%	2301
	21st to end	Day	20% 9% 3 5% 4 3 5% 4 5% 7% 35%	2760
June	1st to 10th	Day	23% 7% 3 6% 6% 3 4 4 5% 8% 31%	2700
	11th to 20th	Day	20% 7% 3 5% 4 3 4 4 5% 7% 39%	2700
	21st to end	Day	26% 8% 2 6% 5% 2 4 4 5% 7% 30%	2700
July	1st to 10th	Day	19% 7% 3 4 4 2 4 4 5% 9% 38%	2636
	11th to 20th	Day	17% 7% 3 5% 4 2 5% 4 6% 8% 39%	2520
	21st to end	Day	15% 6% 2 5% 5% 3 5% 5% 7% 8% 39%	2659
August	1st to 10th	Day	15% 6% 2 5% 4 3 4 5% 6% 8% 41%	2327
	11th to 20th	Day	16% 7% 2 5% 7% 3 4 4 6% 9% 37%	2304
	21st to end	Day	13% 6% 2 4 4 2 4 4 6% 8% 47%	2574
September	1st to 10th	Day	12% 5% 2 5% 4 3 3 4 5% 8% 49%	2072
	11th to 20th	Day	14% 5% 2 3 4 2 4 4 4 6% 52%	1980
	21st to end	Day	18% 6% 2 4 5% 2 4 4 5% 6% 44%	1980
October	1st to 10th	Day	16% 8% 2 5% 4 2 4 5% 4 7% 42%	1908
	11th to 20th	Day	19% 6% 3 5% 5% 3 3 4 5% 7% 41%	1800
	21st to end	Day	22% 9% 2 4 4 3 3 4 4 5% 38%	1805
November	1st to 10th	Day	19% 6% 2 6% 4 3 4 4 5% 6% 42%	1671
	11th to 20th	Day	21% 5% 2 4 4 2 3 5% 5% 7% 41%	1640
	21st to end	Day	20% 9% 3 5% 4 2 4 4 4 6% 39%	1520
December	1st to 10th	Day	24% 9% 2 5% 4 3 6% 3 5% 6% 33%	1473
	11th to 20th	Day	25% 9% 3 5% 4 3 5% 3 5% 6% 31%	1668
	21st to end	Day	26% 7% 3 5% 4 2 3 4 4 6% 35%	2431
January	1st to 10th	Night	15% 9% 4 6% 5% 3 4 4 5% 7% 39%	4447
	11th to 20th	Night	14% 10% 4 8% 6% 3 4 4 5% 6% 36%	4440
	21st to end	Night	18% 11% 4 7% 5% 3 4 4 5% 7% 32%	4747
February	1st to 10th	Night	19% 9% 4 6% 5% 3 5% 4 6% 7% 32%	2470
	11th to 20th	Night	15% 11% 3 6% 5% 3 5% 3 5% 6% 38%	2323
	21st to end	Night	16% 9% 3 6% 5% 3 5% 3 5% 7% 37%	1884
March	1st to 10th	Night	17% 11% 4 6% 5% 4 3 3 5% 6% 37%	2233
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 5% 6% 6% 33%	2066
	21st to end	Night	19% 8% 3 6% 4 3 4 3 4 6% 40%	2178
April	1st to 10th	Night	22% 10% 3 6% 5% 3 4 4 4 7% 33%	1854
	11th to 20th	Night	22% 8% 4 6% 4 3 3 4 6% 7% 34%	1598
	21st to end	Night	25% 9% 3 6% 5% 2 4 4 4 6% 32%	1620
May	1st to 10th	Night	23% 8% 3 6% 5% 3 5% 4 5% 7% 31%	1620
	11th to 20th	Night	24% 8% 3 6% 5% 3 4 3 5% 7% 32%	1593
	21st to end	Night	22% 10% 3 6% 5% 3 4 4 5% 6% 33%	1526
June	1st to 10th	Night	27% 10% 3 5% 5% 2 5% 5% 4 7% 27%	1260
	11th to 20th	Night	21% 9% 3 4 4 3 5% 5% 5% 7% 35%	1260
	21st to end	Night	28% 9% 3 5% 5% 2 3 4 5% 6% 30%	1260
July	1st to 10th	Night	20% 9% 3 6% 4 3 5% 4 6% 7% 32%	1320
	11th to 20th	Night	21% 9% 3 4 5% 3 4 5% 5% 8% 33%	1440
	21st to end	Night	21% 8% 2 5% 6% 3 5% 5% 5% 8% 32%	1640
August	1st to 10th	Night	18% 8% 3 5% 4 3 5% 6% 6% 9% 36%	1612
	11th to 20th	Night	19% 9% 3 6% 5% 2 5% 6% 6% 9% 32%	1596
	21st to end	Night	15% 6% 2 5% 4 3 4 4 4 9% 43%	1782
September	1st to 10th	Night	15% 5% 2 4 4 2 4 5% 5% 7% 48%	1884
	11th to 20th	Night	17% 7% 2 4 3 2 3 4 4 6% 48%	1980
	21st to end	Night	18% 6% 2 4 4 2 3 4 6% 6% 45%	1980
October	1st to 10th	Night	20% 6% 3 5% 4 3 4 4 5% 6% 40%	2051
	11th to 20th	Night	19% 6% 2 5% 5% 3 4 4 4 6% 41%	2160
	21st to end	Night	25% 9% 2 5% 4 2 3 4 4 6% 37%	2546
November	1st to 10th	Night	19% 5% 3 5% 4 3 5% 4 5% 6% 41%	2407
	11th to 20th	Night	18% 7% 2 5% 5% 3 4 4 5% 6% 40%	2536
	21st to end	Night	18% 7% 3 5% 5% 3 4 5% 5% 7% 38%	2660
December	1st to 10th	Night	25% 9% 3 6% 5% 2 4 4 5% 7% 30%	2702
	11th to 20th	Night	25% 8% 2 5% 4 2 3 4 5% 6% 35%	3531
	21st to end	Night	25% 9% 3 5% 4 2 3 4 4 5% 35%	5236

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	48% 6% 17% 21% 7% 1	2496
	11th to 20th	Day	44% 7% 14% 22% 11% 2	2520
	21st to end	Day	48% 8% 16% 18% 9%	2906
February	1st to 10th	Day	54% 7% 13% 15% 10% 2	1710
	11th to 20th	Day	48% 8% 15% 16% 12% 1	1748
	21st to end	Day	48% 7% 11% 20% 10% 4	1570
March	1st to 10th	Day	48% 6% 13% 17% 13% 2	1938
	11th to 20th	Day	42% 7% 13% 20% 15% 3	2059
	21st to end	Day	46% 6% 10% 18% 15% 5%	2178
April	1st to 10th	Day	49% 5% 10% 17% 15% 3	2103
	11th to 20th	Day	44% 6% 11% 23% 14% 3	2312
	21st to end	Day	49% 6% 10% 17% 16% 3	2340
May	1st to 10th	Day	50% 7% 10% 19% 12% 2	2340
	11th to 20th	Day	43% 7% 11% 22% 15% 2	2305
	21st to end	Day	50% 8% 11% 20% 11% 1	2760
June	1st to 10th	Day	52% 7% 13% 19% 9%	2700
	11th to 20th	Day	47% 6% 11% 19% 15% 3	2700
	21st to end	Day	55% 7% 11% 15% 10% 2	2700
July	1st to 10th	Day	46% 8% 15% 19% 12%	2564
	11th to 20th	Day	45% 8% 15% 20% 11% 1	2445
	21st to end	Day	42% 9% 16% 23% 9% 1	2510
August	1st to 10th	Day	40% 9% 16% 25% 9%	2314
	11th to 20th	Day	44% 9% 14% 21% 12%	2304
	21st to end	Day	35% 7% 14% 25% 17% 1	2574
September	1st to 10th	Day	34% 7% 14% 26% 17% 2	2072
	11th to 20th	Day	34% 6% 13% 24% 20% 3	1980
	21st to end	Day	40% 7% 10% 26% 16% 1	1980
October	1st to 10th	Day	40% 8% 13% 23% 15% 2	1908
	11th to 20th	Day	42% 6% 14% 28% 10%	1800
	21st to end	Day	48% 6% 12% 21% 13% 1	1805
November	1st to 10th	Day	43% 6% 15% 22% 12% 1	1671
	11th to 20th	Day	42% 7% 10% 21% 16% 3	1640
	21st to end	Day	47% 6% 18% 21% 7% 1	1520
December	1st to 10th	Day	53% 8% 13% 18% 8% 1	1473
	11th to 20th	Day	54% 6% 13% 19% 8% 1	1668
	21st to end	Day	52% 9% 13% 17% 7% 2	2431
January	1st to 10th	Night	46% 7% 16% 23% 7% 1	4447
	11th to 20th	Night	49% 8% 16% 18% 8% 1	4440
	21st to end	Night	53% 7% 14% 18% 8%	4747
February	1st to 10th	Night	53% 7% 13% 15% 10% 1	2470
	11th to 20th	Night	47% 7% 11% 18% 13% 2	2326
	21st to end	Night	48% 5% 11% 20% 12% 4	1884
March	1st to 10th	Night	49% 6% 11% 17% 14% 3	2242
	11th to 20th	Night	49% 7% 13% 14% 14% 2	2067
	21st to end	Night	47% 5% 8% 20% 17% 3	2178
April	1st to 10th	Night	52% 6% 9% 14% 16% 4	1854
	11th to 20th	Night	49% 5% 9% 20% 15% 2	1598
	21st to end	Night	53% 5% 10% 16% 12% 3	1620
May	1st to 10th	Night	53% 6% 9% 18% 14% 1	1620
	11th to 20th	Night	52% 7% 10% 19% 11% 2	1594
	21st to end	Night	52% 6% 10% 18% 13% 1	1527
June	1st to 10th	Night	56% 8% 10% 18% 7% 1	1260
	11th to 20th	Night	48% 8% 11% 20% 11% 2	1260
	21st to end	Night	56% 5% 9% 19% 9% 2	1260
July	1st to 10th	Night	51% 8% 12% 18% 11%	1282
	11th to 20th	Night	49% 9% 13% 18% 11%	1392
	21st to end	Night	50% 8% 15% 18% 9% 2	1549
August	1st to 10th	Night	44% 10% 14% 23% 9%	1600
	11th to 20th	Night	49% 9% 15% 18% 9%	1596
	21st to end	Night	41% 6% 12% 21% 19% 1	1782
September	1st to 10th	Night	36% 7% 14% 26% 16% 1	1884
	11th to 20th	Night	38% 5% 12% 25% 18% 2	1980
	21st to end	Night	39% 5% 11% 26% 17% 1	1980
October	1st to 10th	Night	43% 6% 13% 22% 14% 2	2051
	11th to 20th	Night	42% 6% 13% 26% 12% 1	2160
	21st to end	Night	49% 5% 11% 21% 12% 1	2546
November	1st to 10th	Night	44% 6% 12% 24% 14% 1	2407
	11th to 20th	Night	46% 6% 13% 20% 14% 2	2536
	21st to end	Night	46% 7% 16% 19% 11% 2	2660
December	1st to 10th	Night	55% 7% 12% 17% 9%	2702
	11th to 20th	Night	50% 6% 14% 20% 11% 1	3532
	21st to end	Night	50% 8% 14% 15% 10% 2	5236

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% 28% 31% 13% 5%	180
	11th to 20th	Day	29% 24% 28% 16% 2 1	180
	21st to end	Day	20% 21% 34% 20% 5%	280
February	1st to 10th	Day	25% 22% 32% 17% 4	370
	11th to 20th	Day	21% 28% 36% 12% 2	403
	21st to end	Day	23% 20% 34% 21% 3	382
March	1st to 10th	Day	25% 20% 36% 17% 2	460
	11th to 20th	Day	22% 22% 31% 21% 4	449
	21st to end	Day	24% 18% 31% 19% 7% 1	462
April	1st to 10th	Day	29% 16% 34% 15% 4 1	420
	11th to 20th	Day	25% 14% 35% 19% 6%	412
	21st to end	Day	26% 9% 35% 23% 7% 1	420
May	1st to 10th	Day	23% 14% 35% 23% 4 1	423
	11th to 20th	Day	17% 8% 40% 26% 8% 1	447
	21st to end	Day	27% 6% 29% 26% 11% 1	600
June	1st to 10th	Day	25% 4 28% 30% 11% 2	630
	11th to 20th	Day	25% 5% 24% 30% 14% 2	630
	21st to end	Day	29% 5% 23% 30% 11% 2	630
July	1st to 10th	Day	24% 4 25% 32% 14% 2	559
	11th to 20th	Day	20% 4 21% 38% 15% 2	444
	21st to end	Day	17% 4 23% 40% 14% 2	488
August	1st to 10th	Day	14% 4 25% 36% 19% 1	446
	11th to 20th	Day	21% 5% 20% 35% 17% 3	439
	21st to end	Day	17% 6% 22% 33% 19% 3	495
September	1st to 10th	Day	17% 3 24% 38% 17% 1	450
	11th to 20th	Day	19% 10% 27% 27% 12% 4	450
	21st to end	Day	19% 5% 33% 27% 13% 3	450
October	1st to 10th	Day	19% 10% 25% 30% 14% 1	414
	11th to 20th	Day	19% 11% 33% 26% 9% 2	360
	21st to end	Day	30% 12% 30% 23% 5%	396
November	1st to 10th	Day	22% 19% 26% 25% 7% 1	365
	11th to 20th	Day	24% 23% 29% 19% 5% 1	370
	21st to end	Day	25% 22% 29% 19% 4	370
December	1st to 10th	Day	28% 17% 34% 17% 3	323
	11th to 20th	Day	35% 22% 30% 10% 3	180
	21st to end	Day	30% 21% 30% 14% 5%	198
January	1st to 10th	Night	24% 24% 31% 18% 3	763
	11th to 20th	Night	27% 23% 32% 15% 4	760
	21st to end	Night	19% 25% 35% 17% 4	836
February	1st to 10th	Night	25% 22% 34% 15% 4	760
	11th to 20th	Night	23% 27% 31% 16% 2 1	743
	21st to end	Night	23% 19% 35% 20% 4	628
March	1st to 10th	Night	25% 17% 36% 20% 2	760
	11th to 20th	Night	22% 18% 31% 22% 7%	752
	21st to end	Night	23% 15% 32% 23% 6% 1	792
April	1st to 10th	Night	29% 12% 33% 20% 5%	720
	11th to 20th	Night	26% 8% 32% 27% 5%	534
	21st to end	Night	31% 7% 26% 25% 9% 1	540
May	1st to 10th	Night	27% 4 29% 27% 10% 2	540
	11th to 20th	Night	26% 5% 30% 32% 8%	532
	21st to end	Night	26% 6% 22% 32% 12% 2	484
June	1st to 10th	Night	33% 5% 17% 32% 12% 1	360
	11th to 20th	Night	25% 4 21% 34% 15% 1	360
	21st to end	Night	34% 1 15% 36% 14% 1	360
July	1st to 10th	Night	26% 3 17% 39% 15% 1	350
	11th to 20th	Night	25% 4 14% 38% 18% 1	348
	21st to end	Night	25% 1 15% 38% 20% 2	460
August	1st to 10th	Night	23% 1 15% 41% 18% 1	538
	11th to 20th	Night	21% 5% 14% 39% 20% 1	532
	21st to end	Night	18% 3 18% 37% 22% 3	594
September	1st to 10th	Night	18% 2 22% 37% 19% 2	692
	11th to 20th	Night	21% 6% 23% 29% 17% 4	720
	21st to end	Night	20% 5% 25% 31% 15% 3	720
October	1st to 10th	Night	23% 7% 25% 28% 16% 2	720
	11th to 20th	Night	21% 11% 29% 24% 13% 1	720
	21st to end	Night	28% 15% 29% 21% 6% 1	792
November	1st to 10th	Night	23% 13% 27% 26% 9% 1	740
	11th to 20th	Night	21% 23% 28% 20% 6% 1	791
	21st to end	Night	24% 22% 32% 17% 6%	850
December	1st to 10th	Night	31% 17% 33% 15% 3	850
	11th to 20th	Night	27% 24% 31% 15% 2	850
	21st to end	Night	29% 22% 29% 18% 3	935

Page generated at 2024-03-15 14:01:38. Version ac07

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