Machias
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Machias clear sky chart from 2005-11-06 to 2025-03-12.

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	20% 9% 3 6% 4 4 4 3 5% 7% 36%	108401
	Night	20% 9% 3 6% 4 4 4 3 5% 6% 36%	110671
Transparency	Day	48% 7% 13% 20% 12% 2	111978
	Night	49% 6% 12% 20% 12% 2	115259
Seeing	Day	24% 19% 31% 19% 6% 1	16496
	Night	25% 15% 31% 22% 6% 1	24759

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% 10% 3 7% 4 4 4 4 5% 5% 37%	3394
	11th to 20th	Day	15% 9% 3 8% 4 4 4 3 4 4 42%	3570
	21st to end	Day	14% 9% 4 7% 5% 4 4 4 5% 6% 39%	4259
February	1st to 10th	Day	18% 12% 3 7% 4 4 4 4 5% 7% 33%	1800
	11th to 20th	Day	16% 10% 3 7% 5% 5% 5% 4 4 7% 35%	1784
	21st to end	Day	14% 10% 3 7% 5% 4 4 4 5% 6% 37%	1650
March	1st to 10th	Day	26% 12% 3 6% 4 3 4 3 4 5% 30%	3337
	11th to 20th	Day	19% 10% 3 8% 5% 5% 5% 4 5% 7% 29%	3491
	21st to end	Day	28% 12% 3 6% 5% 3 4 3 4 5% 28%	3816
April	1st to 10th	Day	21% 12% 3 7% 4 3 3 3 4 7% 31%	2213
	11th to 20th	Day	22% 9% 2 5% 3 3 4 3 5% 6% 37%	2442
	21st to end	Day	23% 8% 3 6% 4 4 3 2 5% 6% 36%	2470
May	1st to 10th	Day	19% 12% 3 7% 5% 4 4 3 6% 7% 31%	4106
	11th to 20th	Day	18% 8% 2 6% 4 4 4 3 6% 7% 36%	4099
	21st to end	Day	19% 7% 2 6% 5% 4 5% 4 6% 9% 32%	4986
June	1st to 10th	Day	24% 8% 3 7% 4 4 4 3 5% 8% 30%	2850
	11th to 20th	Day	21% 8% 3 6% 4 3 4 3 5% 7% 36%	2850
	21st to end	Day	27% 10% 3 6% 5% 4 4 3 5% 6% 27%	2850
July	1st to 10th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 9% 31%	4760
	11th to 20th	Day	19% 7% 2 5% 4 4 4 3 5% 10% 37%	4486
	21st to end	Day	22% 7% 2 5% 4 4 4 4 6% 7% 34%	4600
August	1st to 10th	Day	22% 8% 3 7% 4 4 5% 4 5% 8% 31%	4105
	11th to 20th	Day	20% 8% 2 6% 4 4 5% 3 6% 8% 34%	4045
	21st to end	Day	11% 5% 2 4 4 4 4 4 6% 8% 48%	4532
September	1st to 10th	Day	13% 5% 2 5% 3 3 4 3 6% 8% 48%	2213
	11th to 20th	Day	17% 5% 2 5% 3 3 3 3 4 6% 49%	2090
	21st to end	Day	19% 5% 2 6% 4 4 4 3 5% 6% 43%	2090
October	1st to 10th	Day	17% 7% 2 7% 4 4 4 4 5% 7% 40%	1981
	11th to 20th	Day	20% 5% 2 5% 3 4 5% 3 4 7% 41%	1900
	21st to end	Day	22% 7% 2 6% 3 4 3 3 5% 5% 38%	1941
November	1st to 10th	Day	20% 7% 2 7% 3 3 4 4 5% 6% 39%	1761
	11th to 20th	Day	20% 7% 2 5% 3 4 4 3 5% 7% 42%	1649
	21st to end	Day	22% 10% 3 5% 3 3 4 3 4 6% 39%	1600
December	1st to 10th	Day	21% 9% 2 4 3 2 4 3 5% 6% 42%	2587
	11th to 20th	Day	23% 8% 2 5% 4 4 3 2 4 5% 38%	2618
	21st to end	Day	22% 11% 3 5% 3 3 4 2 4 6% 38%	3476
January	1st to 10th	Night	14% 10% 3 7% 4 4 4 3 4 5% 40%	6557
	11th to 20th	Night	15% 10% 4 9% 5% 4 5% 3 5% 6% 34%	6315
	21st to end	Night	12% 9% 3 7% 4 4 4 3 6% 6% 40%	6694
February	1st to 10th	Night	19% 10% 3 6% 4 5% 4 3 5% 7% 34%	2600
	11th to 20th	Night	16% 10% 3 7% 5% 5% 4 3 5% 6% 37%	2498
	21st to end	Night	16% 11% 3 7% 4 3 4 4 4 6% 38%	1980
March	1st to 10th	Night	27% 12% 3 7% 4 3 3 2 3 5% 30%	3723
	11th to 20th	Night	16% 13% 4 9% 5% 5% 5% 4 5% 7% 27%	3497
	21st to end	Night	30% 9% 3 6% 4 4 4 4 4 4 27%	3816
April	1st to 10th	Night	25% 10% 2 6% 3 3 4 4 5% 5% 32%	1964
	11th to 20th	Night	23% 9% 3 6% 4 3 4 4 6% 6% 33%	1688
	21st to end	Night	26% 9% 3 6% 4 5% 3 3 5% 6% 32%	1710
May	1st to 10th	Night	23% 8% 3 6% 4 3 3 3 4 7% 35%	2834
	11th to 20th	Night	20% 7% 2 6% 5% 5% 5% 6% 6% 8% 30%	2793
	21st to end	Night	17% 11% 3 9% 4 4 4 3 7% 7% 31%	2627
June	1st to 10th	Night	26% 9% 3 7% 5% 4 4 3 6% 7% 27%	1330
	11th to 20th	Night	23% 8% 2 7% 3 4 4 3 5% 7% 35%	1330
	21st to end	Night	30% 10% 3 6% 5% 4 4 2 5% 5% 28%	1330
July	1st to 10th	Night	20% 12% 3 8% 6% 4 5% 4 7% 6% 24%	2210
	11th to 20th	Night	23% 7% 2 6% 5% 4 5% 3 5% 7% 33%	2471
	21st to end	Night	21% 10% 3 6% 4 4 4 4 5% 6% 33%	2919
August	1st to 10th	Night	25% 11% 3 6% 5% 4 4 4 5% 7% 26%	2825
	11th to 20th	Night	20% 10% 4 6% 4 5% 4 4 6% 8% 29%	2782
	21st to end	Night	12% 7% 3 6% 4 4 4 4 4 6% 47%	3124
September	1st to 10th	Night	17% 6% 2 6% 3 3 4 4 5% 6% 45%	1962
	11th to 20th	Night	17% 7% 2 4 3 3 3 3 4 6% 47%	2090
	21st to end	Night	19% 7% 1 6% 3 3 3 2 6% 7% 43%	2090
October	1st to 10th	Night	20% 6% 2 5% 4 3 4 4 5% 7% 40%	2198
	11th to 20th	Night	19% 6% 2 5% 4 3 3 3 4 6% 43%	2280
	21st to end	Night	24% 8% 2 5% 4 3 3 2 4 6% 39%	2655
November	1st to 10th	Night	19% 6% 2 6% 3 3 5% 3 5% 5% 41%	2537
	11th to 20th	Night	19% 7% 2 6% 4 4 4 3 5% 5% 41%	2750
	21st to end	Night	21% 8% 2 6% 4 3 4 4 6% 6% 36%	2800
December	1st to 10th	Night	19% 9% 3 6% 3 3 3 3 5% 6% 39%	4599
	11th to 20th	Night	24% 8% 2 4 3 3 3 3 3 5% 42%	5591
	21st to end	Night	22% 10% 2 6% 3 3 3 3 4 6% 38%	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% 24% 6% 1	3395
	11th to 20th	Day	47% 6% 13% 24% 9% 2	3600
	21st to end	Day	47% 7% 12% 16% 13% 5%	4259
February	1st to 10th	Day	53% 6% 13% 16% 10% 2	1800
	11th to 20th	Day	50% 7% 15% 18% 9% 2	1792
	21st to end	Day	46% 7% 13% 20% 10% 4	1650
March	1st to 10th	Day	56% 7% 9% 15% 10% 4	3341
	11th to 20th	Day	47% 11% 14% 16% 10% 2	3491
	21st to end	Day	58% 5% 7% 14% 13% 3	3816
April	1st to 10th	Day	50% 6% 11% 16% 14% 3	2213
	11th to 20th	Day	45% 6% 11% 23% 13% 2	2442
	21st to end	Day	47% 6% 11% 17% 17% 2	2470
May	1st to 10th	Day	48% 10% 15% 18% 7% 1	4120
	11th to 20th	Day	44% 9% 17% 21% 9% 1	4103
	21st to end	Day	46% 10% 13% 17% 12% 1	4986
June	1st to 10th	Day	53% 7% 12% 18% 9% 1	2850
	11th to 20th	Day	49% 6% 11% 17% 14% 2	2850
	21st to end	Day	58% 6% 10% 15% 10% 2	2850
July	1st to 10th	Day	59% 6% 9% 16% 10%	4685
	11th to 20th	Day	53% 7% 12% 19% 9%	4409
	21st to end	Day	53% 7% 12% 19% 9% 1	4453
August	1st to 10th	Day	57% 8% 10% 19% 7%	4092
	11th to 20th	Day	52% 7% 16% 17% 8%	4084
	21st to end	Day	35% 7% 11% 25% 20% 1	4532
September	1st to 10th	Day	37% 7% 13% 24% 18% 1	2213
	11th to 20th	Day	38% 6% 11% 26% 18% 3	2090
	21st to end	Day	42% 5% 10% 28% 14% 1	2090
October	1st to 10th	Day	42% 7% 15% 24% 11%	3293
	11th to 20th	Day	30% 5% 10% 36% 19%	3140
	21st to end	Day	34% 5% 19% 23% 16% 3	3178
November	1st to 10th	Day	45% 6% 13% 22% 12% 1	1761
	11th to 20th	Day	42% 6% 13% 22% 14% 3	1649
	21st to end	Day	48% 7% 15% 21% 7% 1	1600
December	1st to 10th	Day	44% 5% 17% 22% 12%	2587
	11th to 20th	Day	51% 4 14% 15% 12% 4	2618
	21st to end	Day	48% 8% 12% 18% 11% 3	3476
January	1st to 10th	Night	47% 5% 14% 26% 7% 1	6557
	11th to 20th	Night	51% 7% 13% 20% 7% 1	6360
	21st to end	Night	45% 6% 12% 19% 13% 4	6694
February	1st to 10th	Night	53% 7% 14% 15% 11% 2	2600
	11th to 20th	Night	49% 6% 12% 19% 11% 2	2501
	21st to end	Night	47% 6% 11% 20% 13% 3	1980
March	1st to 10th	Night	57% 5% 9% 14% 12% 3	3732
	11th to 20th	Night	51% 10% 14% 14% 9% 1	3498
	21st to end	Night	60% 4 6% 16% 12% 2	3816
April	1st to 10th	Night	53% 6% 8% 15% 15% 3	1964
	11th to 20th	Night	50% 5% 10% 20% 13% 1	1688
	21st to end	Night	53% 4 10% 16% 14% 2	1710
May	1st to 10th	Night	49% 7% 16% 20% 8% 1	2840
	11th to 20th	Night	48% 10% 17% 17% 7% 1	2794
	21st to end	Night	50% 9% 14% 19% 8% 1	2628
June	1st to 10th	Night	57% 6% 11% 18% 7% 1	1330
	11th to 20th	Night	52% 6% 9% 20% 10% 2	1330
	21st to end	Night	59% 5% 8% 18% 7% 3	1330
July	1st to 10th	Night	62% 6% 9% 13% 10%	2175
	11th to 20th	Night	55% 6% 11% 19% 9%	2425
	21st to end	Night	52% 7% 11% 17% 12% 1	2826
August	1st to 10th	Night	61% 6% 10% 17% 6%	2813
	11th to 20th	Night	53% 7% 14% 18% 7%	2809
	21st to end	Night	40% 6% 9% 25% 18% 2	3124
September	1st to 10th	Night	38% 6% 11% 26% 17% 1	1962
	11th to 20th	Night	40% 5% 11% 25% 18% 2	2090
	21st to end	Night	41% 5% 9% 27% 17% 1	2090
October	1st to 10th	Night	41% 6% 14% 25% 13% 1	3666
	11th to 20th	Night	32% 5% 12% 27% 23% 1	3779
	21st to end	Night	40% 5% 10% 28% 15% 2	4368
November	1st to 10th	Night	44% 6% 13% 23% 14% 1	2537
	11th to 20th	Night	45% 6% 12% 20% 15% 2	2750
	21st to end	Night	48% 7% 15% 20% 9% 1	2800
December	1st to 10th	Night	48% 5% 12% 26% 9%	4599
	11th to 20th	Night	47% 5% 14% 19% 13% 2	5592
	21st to end	Night	49% 7% 12% 16% 13% 2	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	28% 25% 33% 12% 3	200
	11th to 20th	Day	30% 21% 37% 8% 5%	200
	21st to end	Day	20% 25% 33% 19% 2	350
February	1st to 10th	Day	27% 27% 28% 15% 3	400
	11th to 20th	Day	25% 32% 31% 10% 2	412
	21st to end	Day	24% 26% 32% 15% 3	414
March	1st to 10th	Day	29% 26% 30% 13% 2	500
	11th to 20th	Day	25% 26% 30% 14% 4	464
	21st to end	Day	30% 24% 28% 12% 4 1	506
April	1st to 10th	Day	32% 25% 31% 8% 3 1	460
	11th to 20th	Day	28% 26% 30% 12% 4 1	452
	21st to end	Day	25% 23% 35% 13% 3 1	460
May	1st to 10th	Day	27% 23% 32% 16% 3	463
	11th to 20th	Day	22% 18% 34% 20% 5% 1	492
	21st to end	Day	26% 17% 30% 19% 7% 1	735
June	1st to 10th	Day	25% 16% 31% 21% 6%	680
	11th to 20th	Day	23% 14% 32% 22% 9% 1	680
	21st to end	Day	32% 10% 29% 21% 6% 1	680
July	1st to 10th	Day	23% 11% 34% 22% 9% 1	670
	11th to 20th	Day	22% 9% 35% 25% 8% 2	515
	21st to end	Day	17% 12% 36% 25% 8% 1	532
August	1st to 10th	Day	17% 9% 33% 30% 10% 1	486
	11th to 20th	Day	20% 10% 31% 28% 9% 1	479
	21st to end	Day	16% 13% 33% 26% 11% 2	539
September	1st to 10th	Day	15% 13% 34% 29% 9% 1	490
	11th to 20th	Day	21% 15% 28% 23% 10% 4	490
	21st to end	Day	20% 14% 32% 22% 10% 3	490
October	1st to 10th	Day	19% 17% 31% 21% 10% 2	433
	11th to 20th	Day	21% 18% 29% 22% 8% 1	390
	21st to end	Day	25% 18% 34% 18% 5%	429
November	1st to 10th	Day	24% 21% 28% 20% 6% 2	395
	11th to 20th	Day	26% 24% 32% 14% 4	400
	21st to end	Day	28% 25% 29% 15% 3	400
December	1st to 10th	Day	28% 21% 30% 17% 3	390
	11th to 20th	Day	36% 29% 24% 10% 2	200
	21st to end	Day	32% 26% 25% 15% 2	220
January	1st to 10th	Night	24% 22% 34% 17% 3	845
	11th to 20th	Night	26% 20% 34% 17% 3	800
	21st to end	Night	19% 26% 36% 15% 4	880
February	1st to 10th	Night	26% 22% 33% 15% 3	800
	11th to 20th	Night	24% 27% 32% 15% 2 1	783
	21st to end	Night	24% 19% 36% 17% 4	660
March	1st to 10th	Night	26% 20% 35% 17% 2	800
	11th to 20th	Night	25% 21% 30% 20% 5%	767
	21st to end	Night	24% 19% 35% 17% 5% 1	836
April	1st to 10th	Night	29% 19% 34% 15% 3	725
	11th to 20th	Night	28% 13% 36% 20% 3	564
	21st to end	Night	29% 14% 32% 18% 6%	570
May	1st to 10th	Night	26% 11% 32% 26% 5%	570
	11th to 20th	Night	29% 9% 34% 22% 5% 1	562
	21st to end	Night	24% 10% 35% 23% 7% 1	546
June	1st to 10th	Night	30% 7% 31% 25% 7% 1	380
	11th to 20th	Night	25% 7% 31% 30% 7% 1	380
	21st to end	Night	33% 4 22% 35% 6%	380
July	1st to 10th	Night	24% 6% 28% 35% 8%	370
	11th to 20th	Night	25% 4 24% 36% 9% 1	368
	21st to end	Night	25% 6% 27% 32% 10%	520
August	1st to 10th	Night	20% 6% 29% 35% 10%	568
	11th to 20th	Night	23% 5% 26% 34% 10% 1	562
	21st to end	Night	19% 5% 28% 34% 13% 1	627
September	1st to 10th	Night	19% 6% 35% 29% 11% 1	675
	11th to 20th	Night	19% 8% 28% 28% 14% 2	760
	21st to end	Night	22% 10% 31% 26% 11% 1	760
October	1st to 10th	Night	24% 8% 28% 28% 12% 1	760
	11th to 20th	Night	22% 14% 29% 23% 10% 1	760
	21st to end	Night	28% 17% 30% 20% 5%	836
November	1st to 10th	Night	24% 16% 30% 23% 6% 1	780
	11th to 20th	Night	25% 20% 30% 18% 7% 1	875
	21st to end	Night	27% 21% 29% 18% 5% 1	900
December	1st to 10th	Night	31% 17% 33% 16% 3	900
	11th to 20th	Night	29% 25% 29% 14% 3	900
	21st to end	Night	27% 24% 30% 15% 3	990

Page generated at 2025-03-09 08:08:43. Version ac07

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