Milton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Milton clear sky chart from 2005-11-06 to 2025-08-05.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	126203
	Night	14% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	121789
Transparency	Day	47% 7% 14% 20% 11% 1	129799
	Night	46% 7% 13% 20% 12% 1	126280
Seeing	Day	17% 12% 29% 25% 12% 5%	15600
	Night	17% 11% 30% 28% 12% 1	24783

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	11% 14% 5% 13% 6% 6% 4 4 5% 6% 27%	3597
	11th to 20th	Day	9% 18% 7% 17% 9% 6% 5% 5% 4 5% 15%	4003
	21st to end	Day	18% 15% 5% 14% 7% 5% 5% 3 5% 5% 19%	4466
February	1st to 10th	Day	13% 16% 5% 11% 8% 6% 6% 4 5% 6% 21%	1800
	11th to 20th	Day	12% 14% 5% 11% 7% 5% 5% 3 5% 7% 24%	1753
	21st to end	Day	18% 12% 4 10% 6% 4 5% 5% 4 5% 26%	1557
March	1st to 10th	Day	17% 9% 4 10% 6% 5% 4 3 4 5% 31%	4932
	11th to 20th	Day	11% 10% 5% 9% 5% 5% 5% 4 6% 8% 32%	4980
	21st to end	Day	16% 10% 3 7% 5% 5% 5% 4 6% 5% 33%	5465
April	1st to 10th	Day	15% 12% 4 8% 6% 6% 4 4 5% 6% 31%	2340
	11th to 20th	Day	17% 10% 3 7% 4 5% 4 3 5% 6% 36%	2472
	21st to end	Day	18% 10% 3 7% 5% 4 5% 3 5% 5% 34%	2600
May	1st to 10th	Day	20% 8% 3 7% 4 5% 4 4 5% 7% 34%	5888
	11th to 20th	Day	17% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	6180
	21st to end	Day	17% 5% 2 7% 4 4 5% 4 6% 7% 39%	6949
June	1st to 10th	Day	14% 6% 2 6% 5% 4 5% 5% 6% 7% 40%	2800
	11th to 20th	Day	11% 6% 2 7% 5% 4 6% 4 7% 8% 40%	2800
	21st to end	Day	13% 5% 2 6% 4 5% 5% 5% 6% 9% 39%	2987
July	1st to 10th	Day	9% 4 2 5% 5% 5% 5% 5% 7% 10% 42%	6497
	11th to 20th	Day	8% 4 2 5% 5% 4 6% 5% 7% 9% 46%	6298
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 7% 9% 48%	6424
August	1st to 10th	Day	17% 6% 2 6% 3 4 4 5% 6% 8% 39%	4156
	11th to 20th	Day	9% 6% 3 8% 5% 6% 5% 4 7% 10% 36%	4044
	21st to end	Day	10% 5% 2 6% 4 5% 5% 4 6% 9% 43%	4382
September	1st to 10th	Day	13% 5% 2 5% 5% 5% 5% 5% 5% 8% 42%	2280
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 5% 8% 46%	2138
	21st to end	Day	15% 5% 2 6% 5% 6% 6% 5% 7% 7% 35%	2069
October	1st to 10th	Day	19% 8% 2 7% 4 5% 5% 3 5% 8% 36%	1900
	11th to 20th	Day	19% 7% 3 9% 5% 5% 5% 3 6% 6% 31%	1900
	21st to end	Day	21% 12% 3 7% 6% 7% 5% 4 5% 6% 24%	2090
November	1st to 10th	Day	12% 11% 3 8% 5% 6% 5% 5% 7% 6% 33%	1710
	11th to 20th	Day	13% 13% 4 9% 7% 5% 6% 4 6% 8% 27%	1600
	21st to end	Day	16% 14% 5% 8% 6% 6% 5% 4 6% 7% 23%	1600
December	1st to 10th	Day	16% 17% 5% 10% 7% 6% 6% 5% 7% 6% 16%	2600
	11th to 20th	Day	21% 16% 4 8% 5% 5% 4 3 6% 6% 22%	2986
	21st to end	Day	26% 17% 7% 11% 6% 5% 4 3 4 4 13%	3960
January	1st to 10th	Night	13% 12% 4 11% 5% 5% 5% 4 6% 6% 29%	6349
	11th to 20th	Night	10% 13% 6% 13% 9% 6% 6% 4 6% 7% 20%	5877
	21st to end	Night	16% 11% 6% 10% 6% 5% 5% 4 6% 7% 25%	6490
February	1st to 10th	Night	14% 12% 4 11% 7% 5% 6% 4 6% 7% 25%	2600
	11th to 20th	Night	12% 12% 5% 10% 6% 7% 5% 4 5% 6% 28%	2533
	21st to end	Night	13% 11% 3 10% 6% 5% 5% 5% 6% 7% 29%	2071
March	1st to 10th	Night	16% 7% 3 8% 5% 5% 5% 4 6% 7% 33%	4908
	11th to 20th	Night	9% 8% 4 6% 4 5% 5% 4 7% 9% 40%	4979
	21st to end	Night	18% 9% 2 6% 4 4 4 3 4 5% 40%	5467
April	1st to 10th	Night	17% 10% 4 6% 5% 5% 5% 4 5% 6% 33%	2058
	11th to 20th	Night	16% 7% 3 7% 6% 4 4 3 5% 7% 38%	1893
	21st to end	Night	16% 9% 2 7% 5% 4 4 4 5% 7% 38%	1800
May	1st to 10th	Night	20% 7% 3 7% 4 4 4 3 5% 6% 36%	4053
	11th to 20th	Night	15% 7% 3 7% 5% 4 5% 3 5% 8% 38%	3698
	21st to end	Night	16% 4 2 5% 4 4 4 4 5% 7% 45%	3926
June	1st to 10th	Night	11% 4 2 6% 5% 4 5% 4 6% 9% 44%	1600
	11th to 20th	Night	11% 4 2 6% 4 5% 4 5% 7% 8% 44%	1600
	21st to end	Night	10% 5% 2 6% 5% 4 4 4 6% 7% 48%	1401
July	1st to 10th	Night	6% 4 2 6% 5% 4 4 4 5% 9% 50%	3441
	11th to 20th	Night	9% 4 1 5% 4 3 4 3 6% 8% 51%	3645
	21st to end	Night	8% 4 2 5% 4 4 4 4 5% 8% 53%	4428
August	1st to 10th	Night	11% 5% 2 6% 4 4 5% 3 5% 7% 47%	2861
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 5% 7% 50%	2785
	21st to end	Night	10% 5% 2 6% 3 4 5% 4 6% 6% 48%	3242
September	1st to 10th	Night	10% 5% 2 6% 4 5% 4 4 6% 7% 48%	1900
	11th to 20th	Night	11% 3 2 5% 3 3 4 3 5% 8% 55%	2039
	21st to end	Night	15% 7% 3 6% 5% 4 5% 3 6% 6% 41%	2110
October	1st to 10th	Night	17% 7% 2 7% 4 3 4 3 5% 6% 42%	2280
	11th to 20th	Night	17% 8% 3 6% 5% 6% 4 4 5% 6% 37%	2280
	21st to end	Night	20% 9% 3 7% 5% 4 5% 3 5% 7% 31%	2508
November	1st to 10th	Night	15% 7% 3 7% 5% 5% 4 4 6% 7% 39%	2583
	11th to 20th	Night	14% 11% 4 7% 5% 5% 6% 5% 7% 7% 30%	2800
	21st to end	Night	18% 10% 4 8% 5% 5% 5% 4 7% 8% 27%	2800
December	1st to 10th	Night	13% 15% 6% 10% 6% 6% 6% 5% 8% 7% 19%	4580
	11th to 20th	Night	16% 17% 5% 9% 5% 5% 5% 4 6% 6% 23%	5208
	21st to end	Night	24% 17% 6% 11% 5% 4 4 3 4 6% 15%	6996

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	55% 9% 14% 12% 10% 2	3598
	11th to 20th	Day	69% 5% 12% 9% 4	4037
	21st to end	Day	67% 5% 12% 9% 7%	4466
February	1st to 10th	Day	62% 7% 13% 14% 3 1	1800
	11th to 20th	Day	59% 7% 11% 14% 7% 1	1762
	21st to end	Day	58% 6% 13% 14% 7% 1	1557
March	1st to 10th	Day	54% 6% 14% 14% 11% 1	4935
	11th to 20th	Day	48% 6% 18% 19% 7% 2	4980
	21st to end	Day	50% 5% 12% 21% 11% 1	5465
April	1st to 10th	Day	53% 5% 12% 17% 11% 1	2340
	11th to 20th	Day	48% 5% 11% 21% 13% 1	2472
	21st to end	Day	50% 6% 11% 18% 13% 3	2600
May	1st to 10th	Day	48% 7% 14% 16% 10% 5%	5897
	11th to 20th	Day	48% 10% 11% 17% 13% 2	6184
	21st to end	Day	42% 6% 13% 21% 15% 3	6949
June	1st to 10th	Day	41% 8% 12% 22% 16% 2	2800
	11th to 20th	Day	39% 8% 14% 24% 15% 1	2800
	21st to end	Day	38% 7% 14% 24% 15% 1	2987
July	1st to 10th	Day	33% 8% 15% 26% 16% 2	6428
	11th to 20th	Day	31% 7% 14% 31% 15% 2	6223
	21st to end	Day	30% 8% 15% 28% 18% 1	6240
August	1st to 10th	Day	41% 7% 15% 23% 14% 1	4143
	11th to 20th	Day	40% 7% 18% 25% 10%	4083
	21st to end	Day	35% 7% 14% 33% 11% 1	4382
September	1st to 10th	Day	39% 8% 15% 27% 11% 1	2280
	11th to 20th	Day	34% 7% 14% 30% 15%	2138
	21st to end	Day	44% 8% 15% 24% 8% 1	2069
October	1st to 10th	Day	37% 7% 16% 26% 13% 1	3160
	11th to 20th	Day	40% 6% 15% 23% 16%	3140
	21st to end	Day	51% 7% 15% 20% 7%	3428
November	1st to 10th	Day	47% 9% 14% 21% 8% 1	1710
	11th to 20th	Day	53% 8% 16% 16% 7%	1600
	21st to end	Day	58% 8% 16% 14% 4	1600
December	1st to 10th	Day	64% 8% 16% 8% 3	2600
	11th to 20th	Day	61% 7% 13% 10% 9%	2986
	21st to end	Day	73% 7% 7% 7% 5%	3960
January	1st to 10th	Night	53% 8% 12% 19% 7%	6349
	11th to 20th	Night	61% 8% 15% 12% 4	5918
	21st to end	Night	57% 6% 13% 13% 10% 1	6490
February	1st to 10th	Night	58% 7% 13% 17% 4 1	2600
	11th to 20th	Night	56% 6% 13% 16% 9% 1	2535
	21st to end	Night	53% 6% 16% 18% 8%	2071
March	1st to 10th	Night	46% 7% 16% 17% 12% 2	4918
	11th to 20th	Night	39% 6% 20% 22% 11% 1	4980
	21st to end	Night	46% 5% 10% 20% 18% 2	5467
April	1st to 10th	Night	51% 6% 10% 18% 13% 2	2058
	11th to 20th	Night	47% 5% 10% 20% 16% 2	1893
	21st to end	Night	45% 7% 10% 20% 15% 3	1800
May	1st to 10th	Night	48% 7% 11% 14% 13% 7%	4060
	11th to 20th	Night	44% 10% 12% 19% 12% 2	3699
	21st to end	Night	38% 6% 14% 23% 17% 2	3927
June	1st to 10th	Night	37% 7% 12% 24% 17% 2	1600
	11th to 20th	Night	35% 7% 14% 25% 17% 2	1600
	21st to end	Night	35% 7% 14% 25% 17% 1	1401
July	1st to 10th	Night	31% 6% 14% 24% 21% 3	3401
	11th to 20th	Night	30% 6% 13% 28% 20% 2	3597
	21st to end	Night	29% 7% 13% 27% 23% 2	4297
August	1st to 10th	Night	36% 7% 12% 27% 16% 3	2850
	11th to 20th	Night	33% 6% 16% 31% 12% 1	2812
	21st to end	Night	33% 7% 14% 30% 15% 1	3242
September	1st to 10th	Night	34% 8% 14% 28% 15% 2	1900
	11th to 20th	Night	28% 7% 12% 33% 19%	2039
	21st to end	Night	42% 7% 12% 27% 11%	2110
October	1st to 10th	Night	32% 5% 11% 26% 25% 1	3800
	11th to 20th	Night	42% 6% 12% 25% 15%	3779
	21st to end	Night	40% 6% 16% 26% 12% 1	4120
November	1st to 10th	Night	42% 8% 13% 23% 13% 1	2583
	11th to 20th	Night	49% 8% 16% 19% 8% 1	2800
	21st to end	Night	53% 7% 20% 16% 4	2800
December	1st to 10th	Night	57% 10% 17% 13% 4	4580
	11th to 20th	Night	58% 7% 12% 13% 9% 1	5208
	21st to end	Night	70% 7% 10% 9% 4	6996

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	17% 20% 37% 19% 7% 2	200
	11th to 20th	Day	21% 22% 40% 12% 5% 1	295
	21st to end	Day	24% 20% 33% 20% 3	330
February	1st to 10th	Day	22% 20% 42% 12% 3	300
	11th to 20th	Day	23% 22% 36% 17% 1	300
	21st to end	Day	28% 23% 34% 14%	251
March	1st to 10th	Day	21% 13% 36% 23% 6%	500
	11th to 20th	Day	20% 18% 35% 19% 6% 1	500
	21st to end	Day	26% 13% 33% 20% 7% 1	550
April	1st to 10th	Day	20% 17% 31% 25% 6% 1	500
	11th to 20th	Day	23% 19% 27% 21% 7% 3	492
	21st to end	Day	23% 13% 34% 21% 7% 2	500
May	1st to 10th	Day	19% 12% 31% 24% 10% 4	503
	11th to 20th	Day	17% 7% 28% 28% 14% 5%	527
	21st to end	Day	13% 7% 29% 28% 17% 7%	573
June	1st to 10th	Day	13% 10% 33% 30% 12% 2	530
	11th to 20th	Day	12% 9% 26% 32% 18% 4	530
	21st to end	Day	14% 8% 30% 30% 14% 4	717
July	1st to 10th	Day	8% 4 23% 36% 21% 9%	585
	11th to 20th	Day	12% 6% 22% 29% 21% 10%	524
	21st to end	Day	8% 4 23% 39% 18% 7%	576
August	1st to 10th	Day	9% 6% 21% 31% 23% 11%	502
	11th to 20th	Day	8% 6% 20% 32% 22% 13%	479
	21st to end	Day	10% 7% 22% 30% 23% 8%	539
September	1st to 10th	Day	12% 6% 21% 30% 20% 11%	490
	11th to 20th	Day	10% 3 18% 28% 26% 15%	490
	21st to end	Day	15% 10% 27% 24% 17% 7%	490
October	1st to 10th	Day	20% 13% 22% 24% 14% 6%	490
	11th to 20th	Day	20% 14% 31% 23% 10% 2	490
	21st to end	Day	27% 14% 30% 21% 8% 1	539
November	1st to 10th	Day	16% 24% 28% 21% 9% 1	288
	11th to 20th	Day	22% 22% 32% 18% 6% 2	200
	21st to end	Day	23% 18% 38% 17% 4	200
December	1st to 10th	Day	23% 24% 31% 20% 4	200
	11th to 20th	Day	26% 25% 29% 19% 2	200
	21st to end	Day	25% 19% 39% 13% 3 1	220
January	1st to 10th	Night	19% 18% 38% 19% 6%	800
	11th to 20th	Night	23% 19% 35% 19% 4	800
	21st to end	Night	17% 15% 40% 23% 6%	880
February	1st to 10th	Night	20% 17% 41% 20% 3	800
	11th to 20th	Night	19% 18% 37% 23% 3	783
	21st to end	Night	18% 19% 37% 23% 3	660
March	1st to 10th	Night	18% 14% 37% 26% 6%	800
	11th to 20th	Night	19% 15% 37% 23% 6%	800
	21st to end	Night	20% 13% 30% 27% 8% 1	880
April	1st to 10th	Night	21% 11% 35% 28% 5%	800
	11th to 20th	Night	19% 12% 33% 26% 9% 1	709
	21st to end	Night	19% 8% 30% 33% 10%	600
May	1st to 10th	Night	16% 7% 28% 32% 15% 2	600
	11th to 20th	Night	15% 4 27% 38% 13% 1	452
	21st to end	Night	12% 3 25% 35% 24% 1	433
June	1st to 10th	Night	13% 4 28% 40% 15% 1	400
	11th to 20th	Night	12% 4 30% 38% 16% 1	400
	21st to end	Night	10% 7% 22% 43% 19%	400
July	1st to 10th	Night	6% 2 23% 45% 24% 1	390
	11th to 20th	Night	9% 3 23% 41% 22% 2	407
	21st to end	Night	8% 2 19% 45% 24% 2	657
August	1st to 10th	Night	9% 3 16% 42% 27% 3	579
	11th to 20th	Night	7% 3 16% 38% 32% 3	564
	21st to end	Night	10% 3 21% 35% 27% 3	693
September	1st to 10th	Night	11% 6% 21% 33% 24% 5%	760
	11th to 20th	Night	11% 5% 19% 32% 29% 6%	760
	21st to end	Night	16% 8% 21% 30% 21% 4	760
October	1st to 10th	Night	18% 8% 26% 26% 19% 3	760
	11th to 20th	Night	18% 13% 30% 28% 9% 1	760
	21st to end	Night	24% 13% 30% 28% 5%	836
November	1st to 10th	Night	20% 12% 28% 29% 10% 1	780
	11th to 20th	Night	18% 15% 35% 23% 7% 2	800
	21st to end	Night	22% 15% 35% 23% 5%	800
December	1st to 10th	Night	24% 18% 34% 18% 6% 1	800
	11th to 20th	Night	23% 18% 37% 17% 5%	800
	21st to end	Night	27% 15% 35% 20% 3	880

Page generated at 2025-08-02 01:32:22. Version ac07

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