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 2024-11-02.

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% 2 6% 4 4 4 3 5% 7% 37%	101221
	Night	20% 9% 3 6% 4 4 4 3 5% 7% 35%	97783
Transparency	Day	46% 7% 13% 20% 12% 1	100982
	Night	48% 7% 13% 19% 11% 1	97643
Seeing	Day	23% 12% 29% 26% 9% 1	15908
	Night	24% 13% 27% 25% 9% 1	24135

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	18% 9% 2 6% 3 4 4 3 4 7% 38%	2495
	11th to 20th	Day	18% 8% 2 4 4 3 4 3 4 5% 44%	2520
	21st to end	Day	17% 10% 3 7% 4 4 4 3 6% 7% 35%	2906
February	1st to 10th	Day	17% 12% 3 6% 5% 4 5% 5% 6% 6% 31%	1710
	11th to 20th	Day	15% 8% 3 8% 4 5% 5% 4 6% 6% 36%	1740
	21st to end	Day	13% 10% 4 7% 5% 5% 5% 3 6% 6% 35%	1570
March	1st to 10th	Day	25% 12% 3 7% 3 3 4 3 4 5% 31%	3179
	11th to 20th	Day	18% 8% 2 7% 5% 4 5% 4 5% 7% 34%	3480
	21st to end	Day	28% 9% 3 6% 4 3 4 3 5% 4 29%	3816
April	1st to 10th	Day	20% 11% 3 6% 5% 4 4 4 5% 6% 34%	2220
	11th to 20th	Day	20% 8% 2 6% 4 3 3 3 5% 7% 39%	2442
	21st to end	Day	20% 9% 2 5% 4 4 4 3 5% 6% 37%	2470
May	1st to 10th	Day	19% 9% 3 7% 5% 4 3 3 6% 7% 33%	4106
	11th to 20th	Day	18% 7% 2 7% 4 4 4 4 5% 7% 37%	4081
	21st to end	Day	18% 9% 3 6% 4 5% 4 4 6% 7% 35%	4914
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	19% 6% 2 7% 4 4 3 3 5% 6% 41%	1681
	11th to 20th	Day	21% 6% 1 5% 3 3 4 4 5% 7% 41%	1640
	21st to end	Day	20% 10% 3 6% 3 3 4 3 4 6% 39%	1520
December	1st to 10th	Day	24% 10% 2 6% 3 4 5% 3 5% 6% 32%	1473
	11th to 20th	Day	24% 10% 2 6% 4 4 4 3 5% 6% 31%	1668
	21st to end	Day	26% 8% 3 6% 4 3 3 3 5% 6% 34%	2431
January	1st to 10th	Night	14% 10% 3 7% 4 4 3 3 5% 7% 38%	4447
	11th to 20th	Night	14% 10% 4 9% 5% 4 4 3 5% 6% 35%	4440
	21st to end	Night	17% 12% 3 9% 4 4 4 3 6% 6% 32%	4747
February	1st to 10th	Night	19% 10% 3 7% 5% 4 5% 4 6% 7% 31%	2470
	11th to 20th	Night	14% 11% 3 7% 4 4 4 3 6% 6% 37%	2323
	21st to end	Night	16% 10% 3 7% 5% 4 4 3 5% 7% 37%	1884
March	1st to 10th	Night	28% 13% 3 6% 3 3 3 2 4 4 31%	3661
	11th to 20th	Night	14% 11% 3 8% 5% 6% 6% 5% 6% 8% 28%	3479
	21st to end	Night	29% 8% 2 6% 4 4 5% 4 5% 5% 28%	3816
April	1st to 10th	Night	22% 11% 2 7% 4 4 4 3 4 6% 33%	1957
	11th to 20th	Night	22% 9% 3 7% 5% 3 3 3 6% 7% 34%	1688
	21st to end	Night	24% 10% 3 6% 4 4 3 3 5% 5% 34%	1710
May	1st to 10th	Night	23% 8% 2 7% 4 3 4 3 5% 8% 34%	2834
	11th to 20th	Night	19% 7% 3 7% 5% 5% 5% 4 6% 9% 29%	2813
	21st to end	Night	16% 11% 3 8% 5% 4 4 3 5% 6% 34%	2693
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% 6% 2 5% 4 4 4 4 5% 6% 41%	2431
	11th to 20th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 40%	2536
	21st to end	Night	18% 8% 2 6% 4 4 4 4 5% 7% 38%	2660
December	1st to 10th	Night	25% 10% 3 6% 4 3 4 4 6% 6% 30%	2702
	11th to 20th	Night	25% 8% 2 5% 3 3 3 4 5% 6% 35%	3531
	21st to end	Night	25% 9% 2 6% 3 3 3 3 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	56% 6% 10% 13% 12% 2	3183
	11th to 20th	Day	44% 8% 15% 19% 12% 2	3480
	21st to end	Day	55% 5% 8% 14% 14% 4	3816
April	1st to 10th	Day	49% 5% 10% 17% 15% 3	2220
	11th to 20th	Day	43% 6% 12% 23% 13% 2	2442
	21st to end	Day	47% 6% 10% 18% 17% 3	2470
May	1st to 10th	Day	46% 10% 15% 19% 8% 1	4120
	11th to 20th	Day	43% 10% 16% 21% 9% 1	4085
	21st to end	Day	45% 10% 13% 18% 13% 1	4914
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	40% 8% 13% 23% 15% 1	2014
	11th to 20th	Day	40% 6% 14% 28% 11%	1900
	21st to end	Day	46% 6% 13% 21% 13% 1	1905
November	1st to 10th	Day	43% 6% 15% 22% 12% 1	1681
	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	57% 5% 10% 13% 11% 3	3670
	11th to 20th	Night	46% 12% 17% 14% 10% 1	3480
	21st to end	Night	58% 5% 7% 15% 13% 2	3816
April	1st to 10th	Night	51% 6% 9% 15% 16% 3	1957
	11th to 20th	Night	49% 5% 9% 21% 14% 2	1688
	21st to end	Night	51% 5% 10% 16% 14% 3	1710
May	1st to 10th	Night	49% 8% 17% 18% 8% 1	2840
	11th to 20th	Night	47% 12% 18% 16% 6% 1	2814
	21st to end	Night	47% 10% 15% 18% 9% 1	2694
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	43% 6% 13% 22% 14% 2	2165
	11th to 20th	Night	41% 6% 13% 26% 14% 1	2280
	21st to end	Night	48% 5% 11% 22% 13% 1	2688
November	1st to 10th	Night	44% 6% 12% 24% 14% 1	2431
	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	21% 23% 31% 21% 4	460
	21st to end	Day	26% 19% 30% 18% 7% 1	506
April	1st to 10th	Day	28% 17% 35% 15% 4 1	460
	11th to 20th	Day	25% 14% 34% 20% 6%	452
	21st to end	Day	24% 9% 38% 22% 6% 1	460
May	1st to 10th	Day	22% 15% 35% 23% 4 1	463
	11th to 20th	Day	16% 8% 38% 29% 9% 1	487
	21st to end	Day	26% 6% 31% 26% 10% 1	651
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% 30% 24% 5%	429
November	1st to 10th	Day	21% 20% 26% 25% 7% 1	369
	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%	760
	21st to end	Night	24% 16% 32% 21% 6% 1	836
April	1st to 10th	Night	29% 12% 32% 21% 5%	760
	11th to 20th	Night	26% 9% 33% 27% 6%	564
	21st to end	Night	30% 8% 26% 26% 8% 1	570
May	1st to 10th	Night	27% 4 29% 27% 10% 2	570
	11th to 20th	Night	25% 5% 28% 33% 9%	562
	21st to end	Night	25% 6% 23% 33% 12% 2	511
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	23% 14% 27% 26% 9% 1	748
	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 2024-10-30 13:19:24. Version ac07

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