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 2026-05-17.

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% 11% 4 9% 6% 5% 5% 4 5% 6% 29%	132270
	Night	18% 13% 5% 11% 6% 5% 4 3 5% 6% 26%	130543
Transparency	Day	54% 6% 12% 18% 9% 1	135787
	Night	59% 6% 11% 16% 8% 1	135113
Seeing	Day	24% 17% 29% 19% 8% 3	16523
	Night	25% 16% 26% 24% 8% 1	25829

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	15% 18% 8% 22% 7% 4 4 2 3 4 13%	4661
	11th to 20th	Day	11% 20% 8% 16% 10% 8% 6% 3 4 4 10%	4650
	21st to end	Day	14% 15% 5% 16% 10% 10% 6% 4 5% 4 12%	5700
February	1st to 10th	Day	16% 15% 6% 15% 10% 6% 6% 3 4 4 13%	1890
	11th to 20th	Day	16% 16% 5% 17% 9% 6% 5% 4 4 4 15%	1872
	21st to end	Day	18% 18% 4 13% 9% 4 4 3 4 5% 17%	1730
March	1st to 10th	Day	20% 13% 5% 12% 8% 5% 4 3 3 4 23%	4684
	11th to 20th	Day	12% 19% 5% 8% 5% 4 3 3 5% 6% 30%	5090
	21st to end	Day	18% 12% 4 11% 5% 4 4 3 4 5% 30%	5838
April	1st to 10th	Day	20% 12% 4 8% 5% 5% 4 4 4 5% 29%	2520
	11th to 20th	Day	19% 11% 2 6% 5% 4 4 4 6% 6% 35%	2494
	21st to end	Day	22% 10% 3 6% 4 4 3 3 5% 6% 32%	2557
May	1st to 10th	Day	31% 9% 3 7% 4 4 4 3 4 5% 26%	6409
	11th to 20th	Day	18% 8% 3 8% 5% 4 5% 3 4 7% 34%	6402
	21st to end	Day	22% 8% 3 6% 4 4 4 4 6% 8% 32%	6949
June	1st to 10th	Day	19% 6% 2 7% 6% 4 5% 4 6% 7% 34%	2800
	11th to 20th	Day	17% 6% 2 6% 4 5% 5% 4 7% 9% 36%	2800
	21st to end	Day	15% 6% 3 7% 6% 5% 5% 4 6% 9% 35%	2800
July	1st to 10th	Day	10% 5% 2 7% 5% 5% 5% 4 7% 10% 39%	6360
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 8% 11% 37%	6360
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 6% 8% 43%	6926
August	1st to 10th	Day	17% 5% 2 6% 4 5% 5% 4 5% 8% 38%	4275
	11th to 20th	Day	16% 7% 3 7% 4 5% 5% 4 6% 8% 35%	4075
	21st to end	Day	17% 6% 2 6% 4 4 4 3 5% 7% 41%	4312
September	1st to 10th	Day	14% 6% 2 5% 4 4 4 4 5% 8% 43%	2400
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 5% 7% 44%	2400
	21st to end	Day	17% 7% 3 7% 5% 4 5% 4 5% 6% 35%	2128
October	1st to 10th	Day	18% 7% 3 8% 5% 5% 4 3 5% 6% 36%	2000
	11th to 20th	Day	21% 8% 3 8% 4 4 4 4 5% 7% 32%	2000
	21st to end	Day	24% 12% 3 9% 5% 5% 4 4 5% 7% 24%	2110
November	1st to 10th	Day	15% 12% 4 9% 6% 5% 5% 4 4 7% 30%	1851
	11th to 20th	Day	16% 15% 4 9% 5% 6% 5% 3 5% 7% 25%	1753
	21st to end	Day	22% 16% 5% 10% 6% 4 4 4 4 6% 19%	1680
December	1st to 10th	Day	20% 20% 8% 16% 7% 6% 4 3 4 4 9%	2680
	11th to 20th	Day	19% 16% 7% 12% 7% 5% 5% 3 4 5% 17%	3066
	21st to end	Day	22% 16% 6% 12% 6% 5% 4 4 4 5% 15%	4048
January	1st to 10th	Night	16% 20% 9% 22% 6% 5% 4 3 4 4 8%	8234
	11th to 20th	Night	11% 20% 10% 17% 8% 6% 5% 3 4 4 12%	8235
	21st to end	Night	14% 14% 6% 15% 10% 8% 6% 4 4 5% 15%	8479
February	1st to 10th	Night	16% 16% 6% 15% 7% 5% 5% 3 4 5% 18%	2730
	11th to 20th	Night	15% 15% 7% 16% 8% 6% 5% 4 4 5% 16%	2632
	21st to end	Night	18% 14% 6% 15% 7% 5% 4 4 3 5% 18%	2076
March	1st to 10th	Night	19% 12% 6% 13% 7% 4 3 3 5% 5% 21%	5372
	11th to 20th	Night	17% 16% 4 7% 5% 4 4 3 5% 5% 30%	5089
	21st to end	Night	22% 11% 4 11% 5% 4 4 3 4 5% 28%	5336
April	1st to 10th	Night	21% 12% 3 9% 6% 4 4 4 5% 6% 26%	2100
	11th to 20th	Night	20% 11% 3 8% 5% 4 4 3 4 6% 33%	2075
	21st to end	Night	21% 10% 3 7% 3 4 4 4 5% 5% 35%	2079
May	1st to 10th	Night	32% 10% 4 8% 4 3 3 3 4 5% 23%	3750
	11th to 20th	Night	18% 8% 3 6% 4 4 5% 4 6% 7% 35%	3623
	21st to end	Night	23% 8% 3 6% 4 4 4 4 5% 7% 33%	3926
June	1st to 10th	Night	17% 7% 3 8% 4 4 5% 3 5% 7% 37%	1600
	11th to 20th	Night	15% 7% 3 7% 4 4 4 4 6% 8% 38%	1600
	21st to end	Night	14% 6% 2 7% 4 5% 4 5% 6% 8% 39%	1600
July	1st to 10th	Night	11% 6% 3 8% 6% 5% 5% 4 7% 9% 37%	3600
	11th to 20th	Night	12% 5% 3 7% 4 4 5% 4 6% 8% 43%	3600
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 7% 47%	3926
August	1st to 10th	Night	15% 7% 3 6% 4 4 4 4 6% 8% 40%	2871
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 3 6% 7% 40%	2941
	21st to end	Night	12% 6% 3 6% 4 4 5% 4 6% 8% 44%	3586
September	1st to 10th	Night	14% 6% 2 7% 4 3 4 3 5% 7% 45%	2000
	11th to 20th	Night	16% 6% 2 5% 4 3 4 3 4 6% 48%	2000
	21st to end	Night	18% 7% 2 5% 4 5% 5% 4 6% 7% 37%	2268
October	1st to 10th	Night	22% 7% 2 7% 4 5% 5% 3 5% 5% 34%	2400
	11th to 20th	Night	23% 8% 3 7% 4 4 5% 3 5% 7% 31%	2400
	21st to end	Night	27% 12% 3 8% 5% 4 4 3 4 6% 24%	2729
November	1st to 10th	Night	19% 13% 3 8% 5% 4 4 3 5% 5% 31%	2667
	11th to 20th	Night	18% 16% 4 8% 5% 4 5% 4 5% 6% 27%	2861
	21st to end	Night	19% 18% 4 9% 5% 5% 4 3 5% 6% 21%	2940
December	1st to 10th	Night	20% 21% 7% 12% 7% 6% 6% 3 4 4 10%	4720
	11th to 20th	Night	23% 16% 7% 10% 5% 4 4 4 4 4 19%	5348
	21st to end	Night	26% 18% 5% 11% 6% 4 3 2 4 5% 16%	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	76% 4 10% 8% 2	4662
	11th to 20th	Day	76% 5% 7% 6% 5% 1	4680
	21st to end	Day	74% 5% 10% 8% 4	5700
February	1st to 10th	Day	74% 6% 9% 10% 2	1890
	11th to 20th	Day	73% 7% 8% 10% 2	1881
	21st to end	Day	70% 5% 10% 11% 4	1730
March	1st to 10th	Day	65% 5% 10% 14% 6% 1	4687
	11th to 20th	Day	54% 6% 19% 11% 9% 1	5090
	21st to end	Day	57% 5% 8% 18% 12% 1	5838
April	1st to 10th	Day	57% 6% 9% 18% 9% 2	2520
	11th to 20th	Day	50% 6% 11% 20% 12% 1	2494
	21st to end	Day	52% 6% 9% 19% 11% 2	2557
May	1st to 10th	Day	61% 5% 9% 15% 10% 1	6420
	11th to 20th	Day	50% 7% 11% 21% 11% 1	6406
	21st to end	Day	50% 7% 12% 20% 10% 1	6949
June	1st to 10th	Day	48% 8% 12% 19% 13% 1	2800
	11th to 20th	Day	44% 8% 14% 22% 11% 1	2800
	21st to end	Day	44% 9% 15% 20% 11% 1	2800
July	1st to 10th	Day	39% 5% 14% 27% 14% 1	6290
	11th to 20th	Day	39% 7% 16% 25% 12% 1	6285
	21st to end	Day	38% 6% 13% 31% 13%	6728
August	1st to 10th	Day	44% 6% 15% 20% 14% 1	4261
	11th to 20th	Day	45% 7% 17% 24% 7% 1	4114
	21st to end	Day	42% 6% 12% 32% 8% 1	4312
September	1st to 10th	Day	39% 7% 13% 29% 11% 1	2400
	11th to 20th	Day	39% 7% 11% 28% 15% 1	2400
	21st to end	Day	47% 7% 11% 23% 10% 1	2128
October	1st to 10th	Day	43% 5% 13% 28% 10%	3260
	11th to 20th	Day	47% 5% 15% 21% 12%	3240
	21st to end	Day	48% 6% 15% 21% 9% 1	3387
November	1st to 10th	Day	54% 7% 12% 16% 10% 1	1851
	11th to 20th	Day	59% 5% 12% 15% 7% 2	1753
	21st to end	Day	67% 6% 14% 11% 2	1680
December	1st to 10th	Day	79% 5% 9% 6% 1	2680
	11th to 20th	Day	69% 6% 11% 9% 5%	3066
	21st to end	Day	69% 6% 11% 11% 3	4048
January	1st to 10th	Night	81% 4 8% 6% 1	8234
	11th to 20th	Night	76% 5% 6% 8% 5%	8280
	21st to end	Night	72% 3 8% 9% 7% 1	8479
February	1st to 10th	Night	69% 5% 9% 12% 4	2730
	11th to 20th	Night	71% 6% 10% 10% 4	2634
	21st to end	Night	67% 6% 11% 10% 6%	2076
March	1st to 10th	Night	64% 5% 12% 13% 6%	5382
	11th to 20th	Night	56% 5% 17% 14% 6% 3	5090
	21st to end	Night	59% 5% 6% 20% 9% 1	5336
April	1st to 10th	Night	58% 7% 10% 16% 7% 2	2100
	11th to 20th	Night	53% 6% 9% 17% 13% 1	2075
	21st to end	Night	50% 6% 9% 19% 13% 3	2079
May	1st to 10th	Night	64% 5% 8% 11% 9% 2	3756
	11th to 20th	Night	46% 7% 15% 20% 11% 1	3624
	21st to end	Night	49% 8% 12% 17% 12% 1	3927
June	1st to 10th	Night	45% 8% 12% 20% 13% 1	1600
	11th to 20th	Night	44% 7% 13% 21% 15% 1	1600
	21st to end	Night	42% 8% 11% 25% 14% 1	1600
July	1st to 10th	Night	43% 6% 13% 23% 14% 1	3560
	11th to 20th	Night	40% 5% 14% 24% 16%	3552
	21st to end	Night	36% 5% 11% 30% 17% 1	3809
August	1st to 10th	Night	42% 7% 15% 25% 10% 1	2861
	11th to 20th	Night	42% 6% 18% 24% 10%	2968
	21st to end	Night	37% 6% 13% 33% 10% 1	3586
September	1st to 10th	Night	39% 7% 13% 26% 13% 2	2000
	11th to 20th	Night	37% 6% 12% 29% 15% 1	2000
	21st to end	Night	44% 8% 13% 23% 11% 1	2268
October	1st to 10th	Night	51% 5% 9% 23% 10%	3920
	11th to 20th	Night	51% 5% 12% 18% 13% 1	3899
	21st to end	Night	51% 5% 12% 24% 7% 1	4402
November	1st to 10th	Night	54% 7% 11% 18% 9% 2	2667
	11th to 20th	Night	58% 7% 11% 16% 6% 2	2861
	21st to end	Night	63% 7% 13% 12% 4	2940
December	1st to 10th	Night	77% 5% 10% 7% 1	4720
	11th to 20th	Night	68% 6% 8% 11% 8%	5348
	21st to end	Night	71% 6% 7% 11% 4	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	35% 25% 26% 10% 4	220
	11th to 20th	Day	32% 28% 28% 10% 1	220
	21st to end	Day	28% 24% 36% 9% 3	349
February	1st to 10th	Day	31% 28% 31% 8% 2	330
	11th to 20th	Day	37% 27% 29% 7% 1	359
	21st to end	Day	35% 21% 32% 11% 1	446
March	1st to 10th	Day	31% 20% 30% 16% 2	540
	11th to 20th	Day	34% 21% 31% 12% 3	540
	21st to end	Day	34% 22% 27% 12% 4 1	594
April	1st to 10th	Day	34% 21% 27% 11% 6%	540
	11th to 20th	Day	30% 25% 23% 12% 6% 3	532
	21st to end	Day	32% 17% 27% 17% 5% 2	540
May	1st to 10th	Day	30% 17% 30% 15% 6% 2	543
	11th to 20th	Day	22% 14% 33% 21% 8% 2	551
	21st to end	Day	22% 13% 29% 23% 12% 3	573
June	1st to 10th	Day	21% 16% 28% 23% 10% 1	530
	11th to 20th	Day	17% 14% 31% 25% 11% 2	530
	21st to end	Day	18% 17% 32% 24% 7% 2	530
July	1st to 10th	Day	12% 9% 33% 28% 15% 3	525
	11th to 20th	Day	11% 8% 30% 31% 17% 3	524
	21st to end	Day	12% 9% 35% 28% 12% 3	576
August	1st to 10th	Day	12% 9% 28% 28% 17% 6%	526
	11th to 20th	Day	15% 10% 27% 26% 14% 7%	519
	21st to end	Day	13% 13% 32% 21% 14% 7%	583
September	1st to 10th	Day	16% 13% 22% 25% 16% 8%	530
	11th to 20th	Day	12% 11% 24% 23% 19% 12%	530
	21st to end	Day	18% 14% 27% 23% 14% 4	530
October	1st to 10th	Day	21% 12% 28% 20% 13% 6%	530
	11th to 20th	Day	28% 20% 25% 18% 8% 2	530
	21st to end	Day	34% 16% 28% 18% 5%	533
November	1st to 10th	Day	29% 20% 27% 17% 7% 1	425
	11th to 20th	Day	31% 24% 25% 16% 1 2	293
	21st to end	Day	42% 15% 35% 8%	220
December	1st to 10th	Day	34% 23% 29% 10% 4	220
	11th to 20th	Day	33% 26% 28% 10% 2	220
	21st to end	Day	32% 25% 27% 13% 2	242
January	1st to 10th	Night	31% 25% 29% 12% 2	840
	11th to 20th	Night	29% 24% 29% 15% 3	840
	21st to end	Night	23% 24% 32% 18% 3	924
February	1st to 10th	Night	29% 21% 30% 19% 1	840
	11th to 20th	Night	27% 25% 31% 15% 2	823
	21st to end	Night	28% 23% 31% 16% 2	692
March	1st to 10th	Night	28% 21% 29% 20% 2	840
	11th to 20th	Night	29% 21% 28% 19% 3	840
	21st to end	Night	28% 19% 28% 19% 6% 1	924
April	1st to 10th	Night	29% 18% 30% 21% 2	840
	11th to 20th	Night	26% 19% 26% 22% 6% 1	831
	21st to end	Night	27% 13% 27% 26% 7%	819
May	1st to 10th	Night	29% 9% 23% 31% 8% 1	457
	11th to 20th	Night	17% 10% 31% 34% 7%	406
	21st to end	Night	14% 10% 27% 35% 13%	433
June	1st to 10th	Night	21% 9% 21% 36% 13% 1	400
	11th to 20th	Night	17% 8% 21% 39% 15%	400
	21st to end	Night	14% 6% 29% 42% 8% 1	400
July	1st to 10th	Night	11% 4 21% 44% 18% 2	390
	11th to 20th	Night	12% 4 17% 47% 17% 2	388
	21st to end	Night	15% 5% 22% 44% 13% 1	438
August	1st to 10th	Night	12% 5% 22% 38% 21% 1	566
	11th to 20th	Night	13% 6% 20% 34% 24% 3	634
	21st to end	Night	16% 6% 23% 34% 21% 1	880
September	1st to 10th	Night	18% 6% 23% 31% 20% 2	800
	11th to 20th	Night	16% 7% 18% 30% 25% 4	800
	21st to end	Night	20% 11% 19% 31% 16% 3	800
October	1st to 10th	Night	26% 11% 23% 21% 17% 2	800
	11th to 20th	Night	28% 14% 27% 24% 7% 1	800
	21st to end	Night	36% 15% 25% 21% 3	880
November	1st to 10th	Night	28% 15% 28% 20% 7%	820
	11th to 20th	Night	28% 21% 26% 18% 6% 1	840
	21st to end	Night	30% 23% 27% 16% 4	840
December	1st to 10th	Night	34% 23% 26% 14% 3	840
	11th to 20th	Night	32% 22% 28% 15% 3	840
	21st to end	Night	33% 23% 27% 14% 3	924

Page generated at 2026-05-14 01:59:01. Version ac07

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