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 2026-01-02.

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	14% 6% 2 6% 4 4 4 4 6% 8% 42%	127138
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	124221
Transparency	Day	25% 39% 8% 15% 11% 2	130698
	Night	25% 38% 7% 15% 12% 2	128731
Seeing	Day	18% 14% 28% 24% 12% 4	16577
	Night	18% 11% 28% 30% 12% 1	25987

By Month

Percentage Cloud Cover SE (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	13% 5% 2 4 3 3 3 3 4 6% 54%	3605
	11th to 20th	Day	14% 7% 3 7% 5% 3 3 3 3 4 48%	3853
	21st to end	Day	14% 8% 3 7% 5% 4 4 3 5% 5% 43%	4466
February	1st to 10th	Day	14% 7% 3 6% 4 4 5% 4 6% 7% 40%	1800
	11th to 20th	Day	18% 7% 3 4 3 3 4 3 5% 6% 43%	1933
	21st to end	Day	17% 9% 3 7% 4 3 4 4 5% 5% 41%	1650
March	1st to 10th	Day	20% 6% 2 4 3 3 3 3 5% 7% 45%	4520
	11th to 20th	Day	11% 8% 2 5% 3 3 4 3 5% 6% 50%	4980
	21st to end	Day	15% 8% 2 5% 4 4 4 3 5% 6% 43%	5778
April	1st to 10th	Day	14% 8% 2 4 4 3 4 3 6% 6% 45%	2400
	11th to 20th	Day	12% 7% 2 5% 4 4 5% 3 5% 7% 47%	2374
	21st to end	Day	14% 6% 2 6% 5% 4 3 3 6% 8% 43%	2400
May	1st to 10th	Day	18% 8% 3 7% 4 5% 5% 4 6% 9% 32%	5579
	11th to 20th	Day	24% 6% 2 5% 4 4 4 4 6% 8% 33%	6288
	21st to end	Day	17% 5% 2 6% 4 4 4 4 6% 8% 39%	6934
June	1st to 10th	Day	13% 6% 2 5% 4 5% 5% 4 7% 9% 41%	2800
	11th to 20th	Day	12% 5% 2 5% 4 5% 5% 4 6% 9% 43%	2800
	21st to end	Day	9% 4 2 5% 4 4 5% 5% 8% 10% 44%	2800
July	1st to 10th	Day	8% 4 2 6% 4 5% 6% 5% 8% 10% 42%	6360
	11th to 20th	Day	11% 6% 2 8% 5% 6% 6% 6% 9% 11% 31%	6360
	21st to end	Day	9% 4 2 6% 5% 6% 6% 5% 8% 11% 39%	6620
August	1st to 10th	Day	15% 6% 2 6% 4 5% 6% 4 9% 11% 32%	4178
	11th to 20th	Day	9% 4 3 7% 5% 6% 5% 5% 7% 8% 40%	3850
	21st to end	Day	10% 4 2 6% 4 4 4 5% 6% 8% 47%	4312
September	1st to 10th	Day	14% 5% 2 5% 4 4 5% 4 6% 8% 43%	2400
	11th to 20th	Day	12% 6% 2 7% 4 4 4 3 5% 7% 46%	2369
	21st to end	Day	20% 7% 2 6% 5% 4 4 3 5% 6% 37%	2200
October	1st to 10th	Day	16% 5% 2 5% 3 5% 4 3 6% 7% 44%	2006
	11th to 20th	Day	18% 5% 2 4 2 3 3 2 4 5% 51%	2000
	21st to end	Day	14% 6% 2 5% 4 3 4 3 5% 6% 49%	2168
November	1st to 10th	Day	13% 5% 2 4 4 3 3 3 5% 6% 53%	1851
	11th to 20th	Day	12% 7% 2 5% 4 3 4 3 4 6% 49%	1890
	21st to end	Day	14% 4 2 6% 4 4 3 3 4 7% 49%	1816
December	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 5% 7% 50%	2680
	11th to 20th	Day	18% 9% 3 6% 3 3 2 3 4 5% 46%	3070
	21st to end	Day	12% 7% 2 5% 4 3 4 4 6% 7% 46%	4048
January	1st to 10th	Night	12% 7% 2 5% 3 3 4 3 4 5% 51%	6364
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 4 5% 53%	6102
	21st to end	Night	15% 8% 2 5% 4 3 4 3 4 5% 46%	6490
February	1st to 10th	Night	18% 6% 2 6% 4 4 3 4 5% 6% 42%	2600
	11th to 20th	Night	18% 7% 2 6% 4 4 3 3 4 5% 43%	2352
	21st to end	Night	18% 6% 2 5% 4 3 4 3 3 6% 45%	1980
March	1st to 10th	Night	16% 8% 2 5% 3 3 3 3 4 5% 47%	5328
	11th to 20th	Night	13% 10% 3 4 3 4 3 3 5% 6% 46%	4980
	21st to end	Night	15% 9% 3 6% 4 4 3 3 4 5% 44%	5152
April	1st to 10th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 41%	2000
	11th to 20th	Night	12% 6% 2 7% 5% 4 4 3 5% 7% 46%	1975
	21st to end	Night	17% 5% 2 6% 4 5% 5% 3 5% 8% 42%	2000
May	1st to 10th	Night	15% 9% 3 8% 4 4 5% 4 6% 8% 32%	4315
	11th to 20th	Night	22% 9% 3 6% 4 4 4 4 5% 7% 31%	3634
	21st to end	Night	19% 7% 2 7% 4 4 4 3 6% 7% 37%	3920
June	1st to 10th	Night	13% 7% 2 5% 4 4 5% 4 5% 7% 43%	1600
	11th to 20th	Night	11% 6% 2 7% 4 4 5% 4 6% 9% 41%	1600
	21st to end	Night	8% 5% 2 6% 5% 5% 4 5% 7% 11% 41%	1600
July	1st to 10th	Night	9% 5% 2 7% 6% 5% 5% 5% 7% 11% 38%	3598
	11th to 20th	Night	11% 7% 3 7% 6% 5% 5% 5% 7% 10% 35%	3597
	21st to end	Night	10% 5% 2 7% 5% 5% 5% 4 6% 10% 38%	4213
August	1st to 10th	Night	17% 8% 3 7% 4 5% 4 4 6% 9% 34%	2938
	11th to 20th	Night	10% 5% 2 7% 5% 5% 5% 4 6% 9% 42%	3197
	21st to end	Night	8% 5% 2 5% 4 3 5% 3 5% 8% 52%	3586
September	1st to 10th	Night	14% 6% 3 6% 4 4 4 3 6% 7% 45%	2000
	11th to 20th	Night	12% 5% 2 6% 3 3 4 3 6% 8% 49%	2030
	21st to end	Night	21% 7% 3 6% 4 4 4 4 5% 7% 36%	2200
October	1st to 10th	Night	17% 6% 2 6% 3 3 3 3 4 6% 47%	2390
	11th to 20th	Night	18% 4 2 4 4 3 3 3 3 6% 51%	2400
	21st to end	Night	15% 6% 2 5% 3 2 3 3 5% 6% 49%	2670
November	1st to 10th	Night	12% 5% 2 5% 4 3 4 3 4 5% 53%	2667
	11th to 20th	Night	15% 6% 3 6% 4 3 4 3 4 5% 48%	2730
	21st to end	Night	12% 6% 2 5% 4 4 4 3 6% 6% 50%	2798
December	1st to 10th	Night	11% 7% 2 5% 3 3 3 3 5% 6% 53%	4720
	11th to 20th	Night	20% 7% 2 6% 4 4 4 3 4 6% 40%	5345
	21st to end	Night	14% 7% 3 6% 4 4 3 3 6% 7% 43%	7150

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	23% 26% 3 20% 24% 3	3606
	11th to 20th	Day	30% 27% 5% 16% 16% 7%	3853
	21st to end	Day	32% 31% 7% 21% 8% 2	4466
February	1st to 10th	Day	18% 64% 6% 8% 4 1	1800
	11th to 20th	Day	18% 61% 3 8% 7% 2	1942
	21st to end	Day	17% 62% 5% 7% 7% 1	1650
March	1st to 10th	Day	30% 29% 5% 15% 14% 7%	4520
	11th to 20th	Day	25% 29% 7% 20% 15% 5%	4980
	21st to end	Day	30% 29% 6% 12% 15% 7%	5778
April	1st to 10th	Day	17% 62% 5% 7% 7% 2	2400
	11th to 20th	Day	15% 63% 5% 9% 7% 1	2374
	21st to end	Day	15% 62% 5% 9% 8% 1	2400
May	1st to 10th	Day	38% 32% 11% 12% 5% 1	5611
	11th to 20th	Day	38% 30% 7% 18% 6%	6292
	21st to end	Day	32% 31% 9% 16% 12% 1	6949
June	1st to 10th	Day	16% 64% 5% 8% 7% 1	2800
	11th to 20th	Day	12% 64% 5% 10% 8% 1	2800
	21st to end	Day	11% 62% 7% 11% 9%	2800
July	1st to 10th	Day	27% 30% 17% 15% 10% 1	6290
	11th to 20th	Day	37% 30% 16% 13% 3	6285
	21st to end	Day	29% 28% 9% 17% 17%	6431
August	1st to 10th	Day	29% 38% 12% 17% 4	4165
	11th to 20th	Day	25% 39% 7% 23% 6%	3886
	21st to end	Day	19% 37% 8% 23% 13% 1	4312
September	1st to 10th	Day	16% 59% 7% 10% 7% 1	2400
	11th to 20th	Day	17% 58% 5% 10% 8% 2	2369
	21st to end	Day	24% 58% 4 9% 4 1	2200
October	1st to 10th	Day	18% 36% 5% 17% 19% 4	3266
	11th to 20th	Day	13% 35% 4 18% 22% 8%	3240
	21st to end	Day	11% 35% 7% 21% 18% 7%	3482
November	1st to 10th	Day	16% 53% 6% 13% 8% 3	1851
	11th to 20th	Day	16% 54% 4 11% 13% 2	1890
	21st to end	Day	16% 55% 3 16% 8% 1	1816
December	1st to 10th	Day	23% 34% 12% 17% 10% 4	2680
	11th to 20th	Day	30% 30% 9% 18% 9% 3	3066
	21st to end	Day	27% 28% 13% 17% 15%	4048
January	1st to 10th	Night	26% 26% 4 18% 21% 5%	6364
	11th to 20th	Night	25% 26% 5% 20% 18% 6%	6102
	21st to end	Night	32% 28% 6% 20% 12% 2	6490
February	1st to 10th	Night	17% 62% 6% 10% 4 1	2600
	11th to 20th	Night	19% 61% 2 7% 9% 1	2354
	21st to end	Night	16% 62% 4 9% 6% 3	1980
March	1st to 10th	Night	32% 29% 5% 15% 10% 8%	5328
	11th to 20th	Night	27% 29% 7% 18% 14% 5%	4980
	21st to end	Night	31% 29% 6% 12% 19% 3	5152
April	1st to 10th	Night	20% 62% 3 7% 7% 1	2000
	11th to 20th	Night	16% 63% 5% 7% 8% 2	1975
	21st to end	Night	17% 62% 5% 7% 8% 1	2000
May	1st to 10th	Night	37% 32% 10% 15% 5% 1	4345
	11th to 20th	Night	41% 30% 8% 15% 6%	3635
	21st to end	Night	36% 30% 9% 14% 10% 1	3927
June	1st to 10th	Night	16% 63% 4 8% 9% 1	1600
	11th to 20th	Night	14% 63% 4 11% 7%	1600
	21st to end	Night	13% 62% 6% 11% 8% 1	1600
July	1st to 10th	Night	33% 30% 14% 13% 10% 1	3560
	11th to 20th	Night	38% 29% 16% 14% 2	3552
	21st to end	Night	32% 28% 12% 15% 13%	4089
August	1st to 10th	Night	35% 37% 11% 13% 5%	2927
	11th to 20th	Night	25% 37% 9% 21% 7%	3227
	21st to end	Night	16% 36% 6% 21% 19% 1	3586
September	1st to 10th	Night	16% 58% 7% 12% 5% 2	2000
	11th to 20th	Night	15% 58% 5% 11% 9% 1	2030
	21st to end	Night	25% 58% 4 8% 5%	2200
October	1st to 10th	Night	22% 36% 7% 16% 16% 2	3910
	11th to 20th	Night	11% 36% 8% 13% 26% 5%	3899
	21st to end	Night	11% 35% 8% 21% 20% 6%	4306
November	1st to 10th	Night	18% 54% 4 12% 9% 3	2667
	11th to 20th	Night	18% 54% 3 10% 12% 3	2730
	21st to end	Night	15% 54% 5% 14% 11% 1	2798
December	1st to 10th	Night	21% 34% 9% 19% 13% 3	4720
	11th to 20th	Night	33% 31% 9% 14% 10% 4	5348
	21st to end	Night	31% 27% 11% 15% 14% 1	7150

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	22% 27% 35% 12% 3	202
	11th to 20th	Day	23% 33% 28% 14% 2	255
	21st to end	Day	22% 26% 35% 13% 3	330
February	1st to 10th	Day	21% 28% 38% 11% 2	300
	11th to 20th	Day	30% 25% 33% 9% 2	481
	21st to end	Day	26% 21% 36% 13% 3	414
March	1st to 10th	Day	23% 26% 30% 17% 4	500
	11th to 20th	Day	22% 25% 33% 15% 3 2	500
	21st to end	Day	23% 20% 38% 15% 4 1	550
April	1st to 10th	Day	23% 23% 35% 13% 4 1	500
	11th to 20th	Day	20% 16% 36% 22% 5% 1	492
	21st to end	Day	21% 16% 36% 20% 6% 2	500
May	1st to 10th	Day	24% 16% 32% 20% 6% 2	503
	11th to 20th	Day	22% 13% 32% 23% 9% 1	527
	21st to end	Day	18% 10% 22% 30% 14% 5%	573
June	1st to 10th	Day	17% 7% 27% 30% 16% 3	530
	11th to 20th	Day	13% 6% 28% 31% 15% 5%	530
	21st to end	Day	12% 6% 22% 35% 20% 5%	530
July	1st to 10th	Day	12% 4 19% 34% 24% 7%	525
	11th to 20th	Day	4 3 18% 40% 25% 9%	524
	21st to end	Day	9% 3 21% 36% 24% 7%	576
August	1st to 10th	Day	12% 3 24% 31% 21% 8%	526
	11th to 20th	Day	9% 4 17% 37% 25% 8%	519
	21st to end	Day	11% 4 21% 32% 21% 11%	583
September	1st to 10th	Day	16% 6% 22% 30% 14% 13%	530
	11th to 20th	Day	15% 4 23% 30% 19% 9%	530
	21st to end	Day	25% 9% 25% 26% 10% 4	530
October	1st to 10th	Day	20% 7% 26% 24% 14% 9%	530
	11th to 20th	Day	19% 12% 26% 24% 16% 2	530
	21st to end	Day	18% 12% 34% 24% 10% 3	564
November	1st to 10th	Day	15% 15% 31% 22% 14% 3	425
	11th to 20th	Day	17% 22% 32% 21% 8% 1	430
	21st to end	Day	17% 21% 31% 20% 9% 2	356
December	1st to 10th	Day	20% 21% 40% 14% 5%	220
	11th to 20th	Day	24% 25% 32% 15% 5%	220
	21st to end	Day	24% 21% 31% 19% 5%	242
January	1st to 10th	Night	19% 23% 34% 21% 4	805
	11th to 20th	Night	20% 18% 35% 23% 4	800
	21st to end	Night	19% 18% 38% 22% 3	880
February	1st to 10th	Night	21% 14% 38% 24% 3	800
	11th to 20th	Night	25% 23% 32% 19% 1	783
	21st to end	Night	22% 19% 36% 20% 3	660
March	1st to 10th	Night	20% 19% 35% 22% 5%	800
	11th to 20th	Night	22% 18% 34% 19% 6% 1	800
	21st to end	Night	22% 13% 38% 22% 5% 1	880
April	1st to 10th	Night	22% 15% 38% 19% 5%	800
	11th to 20th	Night	15% 13% 35% 31% 5%	791
	21st to end	Night	19% 10% 35% 28% 8%	800
May	1st to 10th	Night	19% 10% 34% 29% 7%	729
	11th to 20th	Night	20% 7% 32% 32% 9%	427
	21st to end	Night	16% 4 22% 41% 15% 2	433
June	1st to 10th	Night	16% 3 24% 43% 13% 1	400
	11th to 20th	Night	11% 3 22% 44% 20% 1	400
	21st to end	Night	9% 4 19% 52% 16% 1	400
July	1st to 10th	Night	10% 3 17% 47% 23% 1	390
	11th to 20th	Night	6% 4 12% 45% 32% 2	388
	21st to end	Night	6% 2 18% 46% 26% 3	560
August	1st to 10th	Night	11% 2 12% 45% 28% 2	607
	11th to 20th	Night	11% 3 15% 42% 26% 3	790
	21st to end	Night	10% 3 15% 39% 29% 4	880
September	1st to 10th	Night	18% 2 17% 35% 25% 4	800
	11th to 20th	Night	14% 4 15% 37% 27% 4	800
	21st to end	Night	24% 5% 20% 33% 16% 1	800
October	1st to 10th	Night	20% 6% 19% 32% 19% 5%	800
	11th to 20th	Night	20% 9% 25% 30% 15% 1	800
	21st to end	Night	18% 8% 33% 28% 12% 2	880
November	1st to 10th	Night	13% 12% 32% 27% 13% 2	820
	11th to 20th	Night	18% 16% 30% 28% 8%	840
	21st to end	Night	14% 17% 31% 28% 10% 1	840
December	1st to 10th	Night	23% 14% 33% 20% 8% 1	840
	11th to 20th	Night	20% 17% 33% 26% 5%	840
	21st to end	Night	19% 14% 33% 30% 3	924

Page generated at 2025-12-30 01:14:05. Version ac07

Copyright © 2025 Attilla Danko.