Liverpool
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Liverpool clear sky chart from 2005-11-06 to 2024-01-22.

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	17% 10% 4 7% 7% 4 5% 5% 5% 7% 30%	74795
	Night	19% 11% 4 8% 6% 3 5% 4 5% 6% 28%	75133
Transparency	Day	53% 8% 12% 17% 9% 1	74500
	Night	56% 7% 11% 16% 8% 1	74962
Seeing	Day	24% 17% 29% 19% 8% 3	13537
	Night	25% 16% 26% 24% 8% 1	22885

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	14% 19% 9% 12% 7% 4 6% 5% 4 5% 15%	1517
	11th to 20th	Day	18% 19% 8% 14% 11% 5% 5% 4 4 3 10%	1520
	21st to end	Day	14% 14% 6% 13% 11% 6% 7% 5% 5% 5% 14%	1766
February	1st to 10th	Day	17% 15% 6% 13% 12% 4 6% 4 4 4 13%	1620
	11th to 20th	Day	17% 14% 6% 16% 10% 5% 5% 5% 3 5% 15%	1597
	21st to end	Day	20% 16% 5% 12% 10% 3 5% 4 4 4 16%	1480
March	1st to 10th	Day	15% 14% 8% 11% 9% 4 4 5% 4 5% 19%	1833
	11th to 20th	Day	17% 17% 5% 8% 7% 3 4 4 3 5% 27%	1980
	21st to end	Day	22% 10% 3 7% 6% 3 4 4 4 6% 32%	2272
April	1st to 10th	Day	19% 11% 5% 7% 6% 3 4 5% 4 6% 30%	2160
	11th to 20th	Day	19% 9% 3 6% 5% 2 4 5% 5% 6% 37%	2134
	21st to end	Day	22% 10% 3 5% 5% 3 3 4 5% 6% 33%	2191
May	1st to 10th	Day	20% 9% 3 7% 6% 3 5% 4 5% 6% 34%	2487
	11th to 20th	Day	16% 6% 3 5% 5% 3 5% 4 5% 8% 39%	2478
	21st to end	Day	15% 6% 3 5% 5% 3 3 6% 6% 9% 40%	2725
June	1st to 10th	Day	19% 6% 2 6% 6% 3 5% 5% 6% 7% 35%	2520
	11th to 20th	Day	17% 5% 2 5% 4 4 6% 5% 6% 9% 37%	2520
	21st to end	Day	15% 6% 3 6% 6% 3 5% 6% 6% 9% 35%	2520
July	1st to 10th	Day	11% 5% 3 6% 5% 3 6% 5% 6% 9% 42%	2520
	11th to 20th	Day	12% 5% 2 6% 6% 3 5% 6% 6% 9% 39%	2520
	21st to end	Day	12% 5% 2 5% 6% 4 6% 6% 7% 9% 36%	2744
August	1st to 10th	Day	13% 4 2 5% 6% 4 6% 6% 7% 10% 38%	2353
	11th to 20th	Day	14% 6% 3 6% 6% 4 6% 6% 7% 9% 33%	2249
	21st to end	Day	16% 5% 2 5% 5% 4 5% 5% 7% 9% 37%	2376
September	1st to 10th	Day	15% 6% 2 4 5% 3 4 5% 5% 8% 41%	2160
	11th to 20th	Day	15% 6% 2 5% 5% 3 4 5% 4 7% 43%	2160
	21st to end	Day	16% 6% 4 6% 7% 3 5% 5% 5% 6% 37%	1917
October	1st to 10th	Day	20% 7% 3 8% 6% 3 4 4 5% 6% 34%	1800
	11th to 20th	Day	22% 8% 3 7% 6% 3 4 5% 5% 7% 31%	1800
	21st to end	Day	26% 11% 3 8% 6% 3 5% 5% 5% 6% 22%	1900
November	1st to 10th	Day	15% 11% 4 8% 7% 4 5% 5% 4 7% 30%	1671
	11th to 20th	Day	17% 13% 5% 7% 6% 4 5% 5% 5% 7% 25%	1587
	21st to end	Day	22% 15% 5% 9% 7% 3 4 5% 3 6% 20%	1520
December	1st to 10th	Day	21% 18% 7% 11% 8% 3 5% 4 4 5% 13%	1520
	11th to 20th	Day	21% 16% 8% 9% 7% 4 5% 4 4 5% 17%	1906
	21st to end	Day	28% 19% 6% 9% 6% 3 4 4 3 4 13%	2772
January	1st to 10th	Night	18% 18% 8% 12% 9% 4 5% 4 4 5% 12%	2649
	11th to 20th	Night	18% 17% 7% 13% 10% 4 4 4 3 5% 14%	2660
	21st to end	Night	13% 15% 7% 13% 11% 6% 5% 5% 4 5% 15%	2622
February	1st to 10th	Night	17% 16% 7% 14% 8% 4 5% 4 4 5% 16%	2340
	11th to 20th	Night	16% 13% 7% 14% 10% 4 5% 6% 3 5% 16%	2247
	21st to end	Night	19% 12% 6% 13% 9% 4 5% 4 3 6% 19%	1776
March	1st to 10th	Night	18% 15% 6% 10% 8% 3 4 4 4 5% 23%	2110
	11th to 20th	Night	18% 13% 5% 9% 7% 4 4 4 4 5% 27%	1979
	21st to end	Night	20% 12% 4 8% 5% 3 4 5% 4 5% 31%	2084
April	1st to 10th	Night	21% 11% 4 7% 6% 3 5% 5% 5% 6% 28%	1800
	11th to 20th	Night	19% 9% 3 6% 6% 3 5% 4 5% 6% 34%	1775
	21st to end	Night	21% 10% 3 6% 4 3 5% 5% 4 6% 34%	1782
May	1st to 10th	Night	22% 8% 3 7% 5% 3 4 4 6% 6% 33%	1472
	11th to 20th	Night	13% 7% 2 5% 5% 2 5% 6% 6% 8% 41%	1415
	21st to end	Night	12% 5% 3 5% 4 3 4 6% 6% 9% 43%	1550
June	1st to 10th	Night	17% 6% 3 6% 5% 3 5% 5% 5% 7% 38%	1440
	11th to 20th	Night	15% 7% 2 6% 5% 3 5% 5% 5% 8% 40%	1440
	21st to end	Night	13% 5% 3 6% 5% 4 5% 5% 6% 9% 40%	1440
July	1st to 10th	Night	8% 4 3 5% 6% 4 6% 5% 7% 8% 45%	1440
	11th to 20th	Night	11% 4 2 5% 5% 3 5% 5% 6% 8% 46%	1440
	21st to end	Night	13% 5% 2 5% 5% 2 5% 6% 6% 7% 44%	1574
August	1st to 10th	Night	10% 4 2 4 5% 4 6% 5% 6% 9% 43%	1582
	11th to 20th	Night	11% 6% 3 6% 7% 4 6% 5% 6% 7% 38%	1634
	21st to end	Night	13% 6% 3 5% 4 2 4 5% 5% 8% 44%	1980
September	1st to 10th	Night	15% 6% 2 5% 5% 3 4 4 5% 7% 44%	1800
	11th to 20th	Night	17% 6% 3 4 5% 2 3 4 4 6% 47%	1800
	21st to end	Night	17% 6% 2 4 4 3 5% 5% 5% 8% 39%	2040
October	1st to 10th	Night	24% 7% 2 6% 6% 4 5% 5% 5% 5% 32%	2160
	11th to 20th	Night	24% 8% 3 6% 5% 3 5% 4 5% 7% 30%	2160
	21st to end	Night	30% 12% 4 7% 6% 3 3 4 4 6% 23%	2455
November	1st to 10th	Night	18% 12% 4 7% 6% 3 5% 4 5% 5% 32%	2407
	11th to 20th	Night	19% 14% 4 7% 6% 3 4 5% 5% 6% 27%	2588
	21st to end	Night	19% 17% 5% 8% 6% 3 5% 4 5% 7% 22%	2660
December	1st to 10th	Night	22% 19% 7% 11% 6% 4 5% 4 4 4 14%	2660
	11th to 20th	Night	22% 15% 8% 9% 7% 3 5% 5% 4 4 17%	3288
	21st to end	Night	31% 18% 5% 8% 6% 3 3 3 4 5% 14%	4884

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	70% 7% 10% 10% 3	1518
	11th to 20th	Day	77% 8% 6% 5% 3	1520
	21st to end	Day	71% 7% 10% 8% 4	1766
February	1st to 10th	Day	75% 6% 9% 8% 2	1620
	11th to 20th	Day	72% 7% 7% 11% 3	1606
	21st to end	Day	72% 5% 10% 10% 4	1480
March	1st to 10th	Day	66% 8% 11% 11% 3 1	1836
	11th to 20th	Day	60% 6% 10% 13% 10% 1	1980
	21st to end	Day	54% 6% 10% 16% 12% 2	2272
April	1st to 10th	Day	55% 6% 9% 18% 10% 2	2160
	11th to 20th	Day	47% 6% 12% 21% 12% 2	2134
	21st to end	Day	53% 6% 9% 18% 11% 2	2191
May	1st to 10th	Day	52% 6% 10% 18% 12% 2	2487
	11th to 20th	Day	43% 8% 12% 21% 14% 1	2482
	21st to end	Day	41% 9% 16% 20% 12% 1	2725
June	1st to 10th	Day	47% 8% 12% 19% 13% 1	2520
	11th to 20th	Day	43% 8% 14% 23% 12% 1	2520
	21st to end	Day	44% 9% 15% 20% 11% 1	2520
July	1st to 10th	Day	38% 9% 12% 25% 15% 1	2450
	11th to 20th	Day	39% 9% 17% 27% 8%	2445
	21st to end	Day	41% 10% 15% 21% 12% 1	2591
August	1st to 10th	Day	39% 10% 17% 22% 12% 1	2339
	11th to 20th	Day	46% 9% 15% 21% 8%	2249
	21st to end	Day	43% 8% 14% 23% 11% 1	2376
September	1st to 10th	Day	41% 8% 14% 27% 10% 1	2160
	11th to 20th	Day	41% 7% 11% 25% 15% 1	2160
	21st to end	Day	46% 8% 10% 25% 10% 1	1917
October	1st to 10th	Day	50% 6% 14% 18% 11% 1	1800
	11th to 20th	Day	51% 8% 15% 19% 7%	1800
	21st to end	Day	62% 7% 12% 12% 7% 1	1900
November	1st to 10th	Day	53% 8% 12% 16% 10% 1	1671
	11th to 20th	Day	59% 6% 12% 15% 6% 2	1587
	21st to end	Day	66% 7% 14% 11% 2	1520
December	1st to 10th	Day	73% 7% 10% 9% 1	1520
	11th to 20th	Day	69% 7% 13% 7% 3	1906
	21st to end	Day	74% 7% 8% 10% 1	2772
January	1st to 10th	Night	74% 6% 8% 9% 2	2649
	11th to 20th	Night	74% 7% 8% 8% 3	2660
	21st to end	Night	72% 6% 9% 9% 3 1	2622
February	1st to 10th	Night	71% 5% 9% 11% 4	2340
	11th to 20th	Night	71% 6% 9% 10% 4	2249
	21st to end	Night	68% 6% 11% 10% 6%	1776
March	1st to 10th	Night	64% 6% 12% 13% 4	2120
	11th to 20th	Night	60% 7% 10% 16% 8% 1	1980
	21st to end	Night	57% 5% 8% 18% 10% 2	2084
April	1st to 10th	Night	56% 8% 11% 17% 7% 2	1800
	11th to 20th	Night	51% 7% 10% 17% 14% 1	1775
	21st to end	Night	51% 6% 10% 17% 12% 3	1782
May	1st to 10th	Night	52% 6% 10% 15% 14% 3	1472
	11th to 20th	Night	40% 8% 13% 23% 15% 2	1416
	21st to end	Night	37% 10% 16% 22% 13% 3	1551
June	1st to 10th	Night	44% 8% 13% 21% 13% 1	1440
	11th to 20th	Night	43% 7% 13% 20% 16% 2	1440
	21st to end	Night	40% 8% 11% 26% 14% 1	1440
July	1st to 10th	Night	34% 11% 13% 24% 16% 2	1400
	11th to 20th	Night	36% 7% 14% 28% 14% 1	1392
	21st to end	Night	36% 9% 14% 25% 14% 2	1486
August	1st to 10th	Night	34% 10% 16% 28% 10% 1	1572
	11th to 20th	Night	43% 8% 17% 23% 9%	1634
	21st to end	Night	36% 8% 16% 26% 13% 1	1980
September	1st to 10th	Night	40% 8% 14% 25% 12% 2	1800
	11th to 20th	Night	39% 6% 12% 27% 16% 1	1800
	21st to end	Night	42% 9% 14% 24% 11% 1	2040
October	1st to 10th	Night	52% 7% 12% 17% 11%	2160
	11th to 20th	Night	52% 8% 14% 16% 8% 1	2160
	21st to end	Night	63% 6% 11% 12% 7% 1	2455
November	1st to 10th	Night	54% 7% 11% 17% 9% 2	2407
	11th to 20th	Night	57% 7% 12% 16% 6% 2	2588
	21st to end	Night	62% 8% 14% 12% 4	2660
December	1st to 10th	Night	72% 7% 12% 8% 1	2660
	11th to 20th	Night	69% 8% 10% 9% 4	3288
	21st to end	Night	74% 6% 9% 10% 1	4884

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	36% 22% 28% 10% 4	180
	11th to 20th	Day	35% 28% 27% 8% 1 1	180
	21st to end	Day	27% 26% 36% 8% 3	256
February	1st to 10th	Day	37% 30% 30% 3	240
	11th to 20th	Day	34% 30% 31% 5%	264
	21st to end	Day	37% 24% 27% 11% 1	346
March	1st to 10th	Day	31% 22% 31% 13% 3	420
	11th to 20th	Day	32% 21% 31% 12% 3	420
	21st to end	Day	35% 21% 26% 13% 5% 1	462
April	1st to 10th	Day	32% 21% 29% 12% 6%	420
	11th to 20th	Day	29% 24% 23% 12% 8% 4	412
	21st to end	Day	34% 17% 26% 16% 4 2	420
May	1st to 10th	Day	27% 16% 30% 16% 7% 3	423
	11th to 20th	Day	21% 16% 33% 22% 7% 2	447
	21st to end	Day	20% 13% 29% 23% 13% 4	485
June	1st to 10th	Day	21% 16% 29% 24% 9% 1	450
	11th to 20th	Day	17% 13% 32% 24% 11% 2	450
	21st to end	Day	16% 18% 33% 23% 8% 2	450
July	1st to 10th	Day	13% 9% 30% 28% 16% 4	445
	11th to 20th	Day	12% 7% 30% 33% 15% 3	444
	21st to end	Day	12% 10% 36% 27% 12% 3	488
August	1st to 10th	Day	12% 9% 29% 27% 15% 7%	446
	11th to 20th	Day	14% 11% 28% 26% 14% 7%	439
	21st to end	Day	13% 13% 32% 20% 14% 7%	495
September	1st to 10th	Day	17% 13% 24% 25% 14% 8%	450
	11th to 20th	Day	14% 12% 26% 22% 17% 9%	450
	21st to end	Day	16% 16% 26% 23% 14% 4	450
October	1st to 10th	Day	23% 12% 29% 19% 12% 4	450
	11th to 20th	Day	28% 20% 24% 18% 8% 1	450
	21st to end	Day	37% 16% 27% 16% 4	455
November	1st to 10th	Day	26% 21% 27% 18% 7% 1	365
	11th to 20th	Day	32% 25% 25% 16% 1 1	247
	21st to end	Day	39% 16% 36% 8% 1	180
December	1st to 10th	Day	36% 23% 28% 8% 4	180
	11th to 20th	Day	36% 26% 28% 10% 1	180
	21st to end	Day	35% 27% 26% 12% 1	198
January	1st to 10th	Night	31% 25% 29% 12% 2	760
	11th to 20th	Night	28% 24% 28% 16% 3	760
	21st to end	Night	22% 24% 33% 19% 3	800
February	1st to 10th	Night	31% 21% 32% 15% 1	720
	11th to 20th	Night	26% 26% 32% 14% 2	703
	21st to end	Night	29% 23% 31% 15% 3	592
March	1st to 10th	Night	28% 22% 29% 19% 2	720
	11th to 20th	Night	29% 20% 29% 19% 4	720
	21st to end	Night	28% 19% 27% 20% 7% 1	792
April	1st to 10th	Night	28% 18% 31% 22% 3	720
	11th to 20th	Night	26% 19% 26% 22% 7% 1	711
	21st to end	Night	27% 13% 26% 26% 7%	702
May	1st to 10th	Night	27% 9% 21% 32% 9% 1	392
	11th to 20th	Night	16% 10% 32% 35% 6%	354
	21st to end	Night	13% 10% 28% 35% 14%	389
June	1st to 10th	Night	20% 8% 20% 37% 13% 1	360
	11th to 20th	Night	17% 8% 21% 38% 15%	360
	21st to end	Night	14% 5% 28% 44% 9% 1	360
July	1st to 10th	Night	10% 4 21% 44% 19% 2	350
	11th to 20th	Night	13% 4 18% 46% 17% 2	348
	21st to end	Night	14% 5% 23% 43% 13% 1	394
August	1st to 10th	Night	12% 6% 23% 38% 20% 2	508
	11th to 20th	Night	13% 6% 20% 35% 24% 3	570
	21st to end	Night	15% 6% 23% 34% 21% 1	792
September	1st to 10th	Night	18% 6% 23% 32% 19% 2	720
	11th to 20th	Night	17% 8% 20% 30% 21% 4	720
	21st to end	Night	20% 12% 20% 30% 16% 3	720
October	1st to 10th	Night	28% 11% 23% 20% 16% 2	720
	11th to 20th	Night	28% 14% 28% 23% 7%	720
	21st to end	Night	38% 15% 25% 19% 3	792
November	1st to 10th	Night	27% 16% 28% 21% 8%	740
	11th to 20th	Night	29% 22% 25% 18% 6% 1	760
	21st to end	Night	29% 23% 28% 15% 4	760
December	1st to 10th	Night	35% 24% 26% 13% 2	760
	11th to 20th	Night	32% 21% 29% 14% 3	760
	21st to end	Night	33% 23% 28% 14% 2	836

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