Southport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Southport clear sky chart from 2005-11-06 to 2024-01-12.

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	12% 5% 2 5% 5% 3 5% 5% 6% 8% 44%	74781
	Night	12% 5% 2 5% 5% 3 4 5% 6% 8% 44%	74913
Transparency	Day	24% 39% 10% 13% 11% 3	74503
	Night	25% 39% 9% 13% 12% 3	74710
Seeing	Day	13% 10% 25% 28% 18% 6%	14540
	Night	14% 9% 24% 31% 19% 3	24808

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	15% 5% 3 5% 5% 3 4 4 5% 6% 48%	1706
	11th to 20th	Day	13% 5% 3 6% 5% 3 4 5% 5% 6% 44%	1635
	21st to end	Day	16% 6% 2 5% 4 3 5% 4 4 5% 46%	1782
February	1st to 10th	Day	16% 5% 3 5% 5% 4 5% 4 6% 6% 42%	1620
	11th to 20th	Day	18% 6% 3 4 4 2 4 4 4 5% 46%	1674
	21st to end	Day	15% 6% 2 5% 4 3 5% 5% 5% 6% 44%	1588
March	1st to 10th	Day	12% 5% 2 5% 4 2 3 4 4 6% 53%	1980
	11th to 20th	Day	14% 5% 2 5% 5% 4 6% 5% 6% 7% 41%	1980
	21st to end	Day	13% 5% 2 5% 6% 3 5% 5% 6% 7% 43%	2178
April	1st to 10th	Day	10% 4 2 4 4 3 4 4 5% 8% 53%	2120
	11th to 20th	Day	9% 4 2 4 3 3 5% 4 6% 7% 52%	2134
	21st to end	Day	8% 3 2 4 4 2 4 4 6% 8% 55%	2160
May	1st to 10th	Day	7% 4 2 5% 5% 3 4 4 6% 7% 53%	2160
	11th to 20th	Day	11% 4 2 6% 5% 3 5% 5% 5% 8% 45%	2299
	21st to end	Day	10% 4 2 5% 5% 3 5% 6% 7% 10% 43%	2531
June	1st to 10th	Day	11% 7% 2 5% 7% 4 4 6% 7% 11% 36%	2340
	11th to 20th	Day	9% 4 2 5% 5% 3 4 7% 8% 12% 41%	2340
	21st to end	Day	8% 4 3 6% 5% 4 6% 7% 8% 12% 37%	2340
July	1st to 10th	Day	10% 5% 3 6% 5% 3 6% 6% 9% 13% 36%	2340
	11th to 20th	Day	8% 4 2 6% 5% 4 6% 6% 8% 13% 37%	2340
	21st to end	Day	7% 5% 3 6% 5% 4 6% 7% 8% 12% 37%	2547
August	1st to 10th	Day	10% 5% 2 6% 6% 4 6% 7% 8% 12% 33%	2327
	11th to 20th	Day	10% 5% 3 6% 5% 4 5% 7% 8% 11% 36%	2135
	21st to end	Day	10% 6% 3 6% 8% 4 6% 5% 8% 11% 32%	2376
September	1st to 10th	Day	10% 5% 2 4 6% 4 5% 6% 7% 9% 42%	2160
	11th to 20th	Day	14% 7% 3 5% 6% 3 5% 4 5% 9% 39%	2109
	21st to end	Day	16% 7% 3 6% 5% 4 4 4 5% 7% 38%	1903
October	1st to 10th	Day	14% 5% 3 6% 6% 3 4 4 5% 6% 45%	1800
	11th to 20th	Day	9% 4 2 5% 4 3 3 4 5% 6% 56%	1800
	21st to end	Day	10% 4 2 6% 3 3 3 4 4 6% 56%	1980
November	1st to 10th	Day	12% 5% 2 3 5% 2 3 3 3 7% 54%	1857
	11th to 20th	Day	13% 5% 2 4 5% 3 4 4 4 6% 50%	1900
	21st to end	Day	10% 5% 2 5% 5% 3 4 3 5% 6% 52%	1829
December	1st to 10th	Day	15% 5% 3 7% 5% 3 5% 5% 6% 7% 39%	1534
	11th to 20th	Day	15% 5% 2 4 3 2 3 3 4 5% 54%	2153
	21st to end	Day	15% 8% 2 5% 4 3 4 4 6% 7% 41%	3124
January	1st to 10th	Night	12% 6% 3 5% 5% 2 4 5% 5% 7% 45%	2459
	11th to 20th	Night	11% 6% 3 6% 4 3 4 5% 5% 7% 46%	2365
	21st to end	Night	15% 5% 3 5% 5% 2 4 5% 4 7% 46%	2574
February	1st to 10th	Night	17% 6% 2 4 4 3 4 4 5% 6% 43%	2340
	11th to 20th	Night	17% 7% 3 5% 4 3 3 4 5% 7% 43%	2169
	21st to end	Night	16% 6% 2 6% 6% 3 4 5% 5% 6% 41%	1664
March	1st to 10th	Night	13% 4 2 5% 4 3 5% 4 5% 7% 49%	1980
	11th to 20th	Night	12% 5% 3 7% 7% 4 5% 5% 6% 7% 39%	1980
	21st to end	Night	12% 5% 3 5% 4 2 4 4 5% 7% 47%	2178
April	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 6% 8% 49%	1838
	11th to 20th	Night	11% 4 2 5% 5% 3 5% 5% 5% 6% 49%	1775
	21st to end	Night	7% 4 2 4 4 3 4 4 6% 8% 56%	1800
May	1st to 10th	Night	8% 4 2 4 5% 2 5% 6% 6% 9% 49%	1800
	11th to 20th	Night	12% 6% 2 5% 5% 3 4 5% 6% 8% 44%	1608
	21st to end	Night	10% 4 3 4 6% 3 4 5% 6% 9% 46%	1744
June	1st to 10th	Night	10% 6% 3 6% 6% 3 5% 5% 7% 12% 35%	1620
	11th to 20th	Night	10% 4 2 4 4 3 5% 5% 9% 11% 42%	1620
	21st to end	Night	9% 4 2 6% 5% 4 6% 7% 9% 13% 35%	1620
July	1st to 10th	Night	6% 5% 3 6% 7% 5% 6% 8% 7% 11% 36%	1620
	11th to 20th	Night	7% 5% 2 5% 6% 4 5% 6% 9% 13% 38%	1620
	21st to end	Night	7% 5% 3 6% 6% 3 6% 8% 8% 11% 38%	1771
August	1st to 10th	Night	8% 6% 2 6% 5% 4 5% 8% 8% 10% 38%	1611
	11th to 20th	Night	9% 5% 3 6% 6% 5% 6% 7% 8% 12% 34%	1748
	21st to end	Night	11% 6% 3 5% 6% 4 6% 7% 8% 12% 33%	1980
September	1st to 10th	Night	10% 4 3 5% 5% 5% 6% 6% 6% 9% 40%	1800
	11th to 20th	Night	12% 6% 2 7% 6% 3 5% 6% 7% 10% 35%	1846
	21st to end	Night	17% 7% 2 6% 5% 3 5% 4 5% 7% 38%	2056
October	1st to 10th	Night	13% 6% 2 5% 5% 3 5% 4 4 7% 45%	2160
	11th to 20th	Night	9% 4 2 4 4 3 4 4 5% 9% 52%	2160
	21st to end	Night	10% 5% 2 4 4 3 4 4 5% 7% 54%	2376
November	1st to 10th	Night	12% 4 2 5% 4 3 4 4 4 5% 54%	2221
	11th to 20th	Night	12% 6% 2 5% 5% 3 4 3 5% 7% 47%	2280
	21st to end	Night	11% 5% 3 5% 4 3 4 4 7% 8% 48%	2329
December	1st to 10th	Night	15% 7% 2 6% 6% 4 4 4 5% 7% 41%	2627
	11th to 20th	Night	15% 6% 3 4 5% 2 3 4 4 5% 49%	3042
	21st to end	Night	16% 6% 2 5% 5% 2 3 4 5% 6% 45%	4532

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	22% 40% 9% 12% 14% 4	1707
	11th to 20th	Day	25% 42% 6% 11% 14% 2	1635
	21st to end	Day	28% 38% 5% 12% 13% 4	1782
February	1st to 10th	Day	28% 37% 5% 14% 12% 4	1620
	11th to 20th	Day	27% 38% 4 10% 15% 6%	1683
	21st to end	Day	25% 38% 7% 13% 11% 5%	1588
March	1st to 10th	Day	22% 36% 8% 12% 17% 5%	1980
	11th to 20th	Day	26% 38% 10% 14% 9% 3	1980
	21st to end	Day	27% 39% 8% 13% 10% 2	2178
April	1st to 10th	Day	17% 37% 10% 16% 16% 4	2120
	11th to 20th	Day	17% 36% 10% 15% 14% 7%	2134
	21st to end	Day	19% 39% 9% 14% 15% 3	2160
May	1st to 10th	Day	20% 40% 13% 18% 9% 1	2160
	11th to 20th	Day	26% 40% 13% 13% 8% 1	2303
	21st to end	Day	23% 43% 12% 15% 7%	2531
June	1st to 10th	Day	28% 41% 10% 15% 6%	2340
	11th to 20th	Day	25% 41% 13% 15% 6%	2340
	21st to end	Day	26% 41% 13% 13% 6%	2340
July	1st to 10th	Day	27% 42% 13% 11% 6% 1	2275
	11th to 20th	Day	23% 46% 16% 9% 6%	2271
	21st to end	Day	24% 44% 17% 13% 1	2405
August	1st to 10th	Day	24% 43% 17% 14% 2	2314
	11th to 20th	Day	28% 41% 14% 12% 4	2135
	21st to end	Day	33% 42% 12% 10% 3 1	2376
September	1st to 10th	Day	26% 42% 9% 12% 9% 2	2160
	11th to 20th	Day	25% 41% 10% 10% 11% 2	2109
	21st to end	Day	30% 38% 6% 11% 13% 3	1903
October	1st to 10th	Day	27% 37% 6% 10% 17% 3	1800
	11th to 20th	Day	21% 38% 7% 13% 17% 5%	1800
	21st to end	Day	22% 38% 5% 14% 17% 5%	1980
November	1st to 10th	Day	15% 41% 6% 13% 17% 8%	1857
	11th to 20th	Day	23% 39% 5% 13% 15% 5%	1900
	21st to end	Day	22% 41% 6% 12% 14% 5%	1829
December	1st to 10th	Day	23% 43% 7% 12% 9% 5%	1534
	11th to 20th	Day	24% 33% 5% 14% 17% 7%	2150
	21st to end	Day	30% 27% 9% 16% 16% 2	3124
January	1st to 10th	Night	21% 40% 8% 13% 14% 3	2459
	11th to 20th	Night	24% 42% 6% 11% 13% 3	2365
	21st to end	Night	27% 38% 5% 13% 13% 5%	2574
February	1st to 10th	Night	29% 36% 6% 10% 14% 5%	2340
	11th to 20th	Night	27% 38% 6% 9% 13% 6%	2171
	21st to end	Night	25% 37% 9% 14% 9% 6%	1664
March	1st to 10th	Night	21% 37% 6% 14% 15% 6%	1980
	11th to 20th	Night	28% 40% 9% 10% 11% 3	1980
	21st to end	Night	24% 38% 10% 15% 10% 3	2178
April	1st to 10th	Night	21% 37% 9% 12% 14% 6%	1838
	11th to 20th	Night	22% 36% 8% 13% 13% 7%	1775
	21st to end	Night	19% 38% 9% 17% 15% 2	1800
May	1st to 10th	Night	20% 39% 14% 15% 11% 2	1800
	11th to 20th	Night	26% 39% 12% 13% 10%	1609
	21st to end	Night	23% 41% 13% 17% 7%	1745
June	1st to 10th	Night	29% 39% 14% 13% 5%	1620
	11th to 20th	Night	25% 41% 13% 16% 5%	1620
	21st to end	Night	26% 43% 12% 14% 5%	1620
July	1st to 10th	Night	26% 43% 11% 12% 8% 1	1575
	11th to 20th	Night	23% 44% 19% 11% 4	1566
	21st to end	Night	22% 45% 17% 14% 1	1672
August	1st to 10th	Night	23% 40% 18% 16% 3	1600
	11th to 20th	Night	28% 42% 13% 13% 3	1748
	21st to end	Night	30% 42% 12% 12% 3 1	1980
September	1st to 10th	Night	25% 42% 11% 11% 9% 2	1800
	11th to 20th	Night	26% 41% 11% 12% 9% 1	1846
	21st to end	Night	30% 38% 6% 13% 10% 2	2056
October	1st to 10th	Night	24% 38% 6% 11% 16% 4	2160
	11th to 20th	Night	21% 38% 8% 13% 16% 5%	2160
	21st to end	Night	21% 38% 6% 11% 17% 7%	2376
November	1st to 10th	Night	16% 41% 6% 11% 17% 8%	2221
	11th to 20th	Night	25% 40% 6% 9% 15% 5%	2280
	21st to end	Night	24% 41% 5% 12% 14% 4	2329
December	1st to 10th	Night	24% 41% 8% 11% 11% 4	2627
	11th to 20th	Night	27% 33% 7% 12% 18% 3	3044
	21st to end	Night	28% 26% 6% 18% 19% 3	4532

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	18% 21% 41% 17% 3	270
	11th to 20th	Day	11% 20% 38% 26% 5%	245
	21st to end	Day	19% 21% 42% 15% 3	264
February	1st to 10th	Day	17% 21% 40% 20% 1	240
	11th to 20th	Day	25% 18% 35% 20% 2	342
	21st to end	Day	17% 18% 40% 19% 5% 1	346
March	1st to 10th	Day	13% 19% 37% 23% 8%	420
	11th to 20th	Day	18% 18% 38% 19% 6% 1	420
	21st to end	Day	15% 20% 34% 21% 8% 2	462
April	1st to 10th	Day	14% 21% 28% 26% 10% 2	420
	11th to 20th	Day	11% 14% 31% 24% 15% 5%	412
	21st to end	Day	10% 12% 30% 26% 17% 4	420
May	1st to 10th	Day	7% 15% 37% 26% 10% 5%	423
	11th to 20th	Day	14% 7% 21% 32% 20% 5%	447
	21st to end	Day	14% 4 16% 32% 23% 11%	485
June	1st to 10th	Day	14% 5% 21% 32% 22% 7%	450
	11th to 20th	Day	10% 4 18% 30% 25% 13%	450
	21st to end	Day	9% 2 17% 36% 28% 8%	450
July	1st to 10th	Day	9% 3 10% 33% 33% 12%	445
	11th to 20th	Day	10% 1 10% 33% 35% 11%	444
	21st to end	Day	6% 3 13% 36% 33% 8%	488
August	1st to 10th	Day	13% 4 13% 28% 30% 11%	446
	11th to 20th	Day	11% 2 9% 30% 32% 15%	439
	21st to end	Day	11% 4 9% 29% 31% 16%	495
September	1st to 10th	Day	8% 2 14% 33% 27% 16%	450
	11th to 20th	Day	18% 4 16% 33% 22% 8%	450
	21st to end	Day	19% 3 20% 26% 23% 10%	450
October	1st to 10th	Day	17% 6% 20% 29% 19% 8%	450
	11th to 20th	Day	10% 5% 24% 38% 20% 4	450
	21st to end	Day	10% 7% 28% 35% 16% 4	495
November	1st to 10th	Day	16% 9% 29% 27% 15% 4	455
	11th to 20th	Day	16% 13% 36% 25% 9% 1	460
	21st to end	Day	11% 11% 36% 28% 12% 2	404
December	1st to 10th	Day	19% 12% 37% 24% 7% 1	186
	11th to 20th	Day	18% 18% 32% 22% 9% 1	270
	21st to end	Day	19% 17% 36% 19% 7% 2	297
January	1st to 10th	Night	15% 18% 36% 25% 6%	760
	11th to 20th	Night	13% 16% 28% 34% 9%	728
	21st to end	Night	17% 15% 36% 28% 4	792
February	1st to 10th	Night	20% 11% 35% 27% 6%	720
	11th to 20th	Night	20% 16% 35% 26% 2	703
	21st to end	Night	19% 15% 31% 27% 8%	592
March	1st to 10th	Night	13% 14% 37% 27% 8%	720
	11th to 20th	Night	15% 13% 36% 27% 8% 1	720
	21st to end	Night	16% 11% 34% 28% 10% 1	792
April	1st to 10th	Night	14% 13% 34% 29% 8% 1	720
	11th to 20th	Night	14% 11% 28% 30% 15% 2	711
	21st to end	Night	9% 8% 33% 35% 14% 1	720
May	1st to 10th	Night	8% 10% 33% 34% 14% 1	720
	11th to 20th	Night	16% 5% 23% 32% 22% 2	547
	21st to end	Night	13% 3 11% 31% 33% 9%	584
June	1st to 10th	Night	11% 3 16% 39% 26% 4	540
	11th to 20th	Night	11% 3 12% 34% 31% 9%	540
	21st to end	Night	9% 3 12% 40% 30% 5%	540
July	1st to 10th	Night	6% 2 9% 36% 40% 6%	525
	11th to 20th	Night	7% 2 8% 33% 42% 8%	522
	21st to end	Night	7% 2 10% 38% 36% 6%	591
August	1st to 10th	Night	12% 2 8% 34% 35% 8%	537
	11th to 20th	Night	10% 1 10% 31% 40% 8%	684
	21st to end	Night	11% 3 8% 31% 37% 10%	792
September	1st to 10th	Night	13% 2 9% 30% 38% 9%	720
	11th to 20th	Night	14% 2 13% 36% 27% 8%	720
	21st to end	Night	21% 4 14% 28% 27% 6%	720
October	1st to 10th	Night	13% 4 21% 33% 23% 6%	720
	11th to 20th	Night	12% 7% 21% 35% 21% 4	720
	21st to end	Night	11% 9% 23% 31% 21% 4	792
November	1st to 10th	Night	13% 8% 26% 33% 17% 3	740
	11th to 20th	Night	16% 11% 29% 29% 14% 2	760
	21st to end	Night	11% 11% 30% 29% 17% 2	760
December	1st to 10th	Night	18% 12% 29% 30% 9% 1	760
	11th to 20th	Night	16% 12% 29% 30% 13% 1	760
	21st to end	Night	19% 13% 30% 28% 10%	836

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