Warwick
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Warwick clear sky chart from 2005-11-06 to 2026-08-30.

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% 7% 2 6% 4 4 4 4 5% 7% 40%	143530
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 41%	138696
Transparency	Day	42% 6% 13% 21% 15% 3	147078
	Night	43% 6% 11% 21% 16% 3	143237
Seeing	Day	19% 16% 33% 22% 8% 2	17454
	Night	20% 14% 33% 25% 7% 1	26301

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	10% 8% 3 7% 4 4 5% 3 6% 6% 45%	4661
	11th to 20th	Day	15% 8% 3 6% 4 3 4 3 3 4 47%	4650
	21st to end	Day	15% 8% 3 5% 3 3 3 3 4 5% 47%	5124
February	1st to 10th	Day	17% 8% 2 5% 4 5% 5% 3 6% 7% 38%	2011
	11th to 20th	Day	14% 7% 2 5% 5% 4 4 4 5% 6% 43%	2048
	21st to end	Day	19% 8% 2 6% 3 4 4 4 4 6% 40%	1730
March	1st to 10th	Day	20% 11% 2 6% 3 3 3 2 4 6% 39%	4576
	11th to 20th	Day	15% 9% 2 5% 4 4 4 3 5% 6% 43%	4873
	21st to end	Day	22% 9% 3 7% 4 4 4 4 5% 5% 33%	5907
April	1st to 10th	Day	19% 8% 3 5% 4 3 3 3 6% 7% 38%	2520
	11th to 20th	Day	18% 7% 2 5% 3 3 4 3 6% 7% 41%	2494
	21st to end	Day	20% 7% 2 6% 4 4 4 3 5% 6% 39%	2725
May	1st to 10th	Day	26% 9% 3 6% 4 4 4 3 5% 6% 31%	7639
	11th to 20th	Day	20% 8% 3 7% 4 4 3 3 4 6% 37%	7658
	21st to end	Day	22% 7% 2 6% 4 4 5% 4 6% 7% 32%	9060
June	1st to 10th	Day	17% 6% 2 5% 5% 5% 5% 4 7% 8% 36%	2940
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 4 7% 8% 38%	2940
	21st to end	Day	14% 6% 2 5% 4 5% 5% 4 6% 9% 39%	2940
July	1st to 10th	Day	17% 6% 2 6% 4 4 5% 4 6% 10% 35%	8280
	11th to 20th	Day	9% 6% 2 6% 4 4 5% 5% 7% 10% 41%	8280
	21st to end	Day	16% 6% 2 5% 4 4 4 4 6% 7% 42%	8993
August	1st to 10th	Day	16% 6% 3 8% 5% 5% 5% 4 6% 9% 32%	4373
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 4 6% 8% 40%	4203
	21st to end	Day	8% 4 2 5% 4 5% 6% 5% 7% 8% 45%	4420
September	1st to 10th	Day	15% 5% 3 6% 4 4 4 3 5% 6% 45%	2395
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 5% 6% 52%	2200
	21st to end	Day	19% 6% 2 6% 4 4 4 3 4 5% 43%	2200
October	1st to 10th	Day	22% 6% 2 4 3 3 3 2 4 5% 45%	2200
	11th to 20th	Day	16% 6% 2 5% 3 3 3 3 5% 7% 47%	1973
	21st to end	Day	19% 5% 2 5% 4 4 4 3 5% 4 45%	1980
November	1st to 10th	Day	16% 6% 2 5% 4 4 4 3 5% 5% 47%	1851
	11th to 20th	Day	16% 6% 2 4 4 3 4 3 5% 6% 48%	1890
	21st to end	Day	18% 6% 2 6% 4 3 4 3 4 5% 45%	1890
December	1st to 10th	Day	14% 8% 3 5% 3 3 3 3 5% 6% 48%	2792
	11th to 20th	Day	19% 6% 2 5% 4 2 3 2 3 5% 50%	3066
	21st to end	Day	19% 10% 3 7% 4 4 3 2 4 5% 39%	4048
January	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 4 5% 50%	8234
	11th to 20th	Night	16% 10% 3 7% 4 4 4 3 4 5% 41%	8235
	21st to end	Night	15% 9% 3 7% 4 5% 4 3 4 5% 41%	9057
February	1st to 10th	Night	16% 9% 3 5% 5% 4 4 3 4 5% 42%	2601
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 5% 6% 41%	2458
	21st to end	Night	17% 9% 2 6% 4 4 4 3 5% 4 41%	2076
March	1st to 10th	Night	23% 9% 2 4 3 4 3 3 4 6% 39%	5484
	11th to 20th	Night	17% 10% 3 6% 4 4 3 3 4 6% 41%	5306
	21st to end	Night	24% 10% 2 6% 4 4 4 3 5% 5% 34%	5264
April	1st to 10th	Night	19% 9% 3 6% 4 4 4 3 5% 6% 38%	2100
	11th to 20th	Night	19% 8% 2 6% 4 4 4 3 5% 6% 39%	2075
	21st to end	Night	20% 8% 3 7% 4 4 3 3 4 5% 41%	1894
May	1st to 10th	Night	26% 8% 3 6% 4 3 4 3 4 6% 31%	5259
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 8% 34%	5235
	21st to end	Night	22% 8% 3 8% 5% 5% 4 4 5% 7% 30%	5123
June	1st to 10th	Night	16% 7% 2 7% 5% 4 4 4 6% 7% 39%	1680
	11th to 20th	Night	17% 7% 2 6% 4 4 4 3 6% 8% 38%	1680
	21st to end	Night	15% 8% 2 5% 4 3 4 4 6% 9% 40%	1680
July	1st to 10th	Night	18% 7% 3 7% 4 4 5% 4 6% 9% 33%	4680
	11th to 20th	Night	12% 8% 2 6% 4 4 5% 5% 6% 8% 40%	4680
	21st to end	Night	15% 6% 2 6% 4 4 4 3 6% 7% 42%	5084
August	1st to 10th	Night	20% 7% 2 7% 5% 4 6% 4 7% 9% 31%	2961
	11th to 20th	Night	9% 7% 3 6% 6% 6% 7% 6% 7% 8% 36%	3061
	21st to end	Night	9% 4 2 5% 3 4 3 3 5% 8% 55%	3677
September	1st to 10th	Night	13% 6% 3 7% 4 4 4 4 6% 6% 44%	2005
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 7% 51%	2200
	21st to end	Night	19% 8% 3 5% 4 3 4 3 4 5% 41%	2200
October	1st to 10th	Night	19% 6% 2 6% 3 3 4 3 4 6% 44%	2200
	11th to 20th	Night	16% 4 2 4 4 4 4 3 5% 7% 48%	2420
	21st to end	Night	20% 6% 2 5% 4 4 3 2 5% 6% 42%	2860
November	1st to 10th	Night	14% 6% 2 5% 3 4 4 3 4 6% 49%	2667
	11th to 20th	Night	17% 7% 2 5% 3 3 4 3 4 5% 47%	2730
	21st to end	Night	15% 6% 2 5% 3 3 4 3 5% 7% 46%	2730
December	1st to 10th	Night	16% 9% 2 5% 4 3 3 2 4 4 49%	4602
	11th to 20th	Night	22% 8% 2 5% 3 3 3 2 4 4 43%	5348
	21st to end	Night	16% 10% 4 7% 4 3 3 2 4 6% 42%	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	38% 5% 10% 24% 19% 3	4662
	11th to 20th	Day	41% 5% 9% 20% 17% 9%	4680
	21st to end	Day	40% 4 10% 24% 21% 2	5124
February	1st to 10th	Day	45% 5% 14% 18% 15% 2	2011
	11th to 20th	Day	42% 6% 11% 23% 15% 3	2057
	21st to end	Day	45% 6% 12% 19% 14% 3	1730
March	1st to 10th	Day	46% 5% 12% 14% 12% 11%	4579
	11th to 20th	Day	38% 7% 15% 27% 11% 2	4873
	21st to end	Day	52% 5% 8% 14% 16% 6%	5907
April	1st to 10th	Day	43% 7% 12% 18% 16% 3	2520
	11th to 20th	Day	43% 6% 10% 20% 18% 3	2494
	21st to end	Day	44% 7% 9% 20% 16% 4	2725
May	1st to 10th	Day	54% 7% 14% 14% 9% 1	7651
	11th to 20th	Day	47% 7% 14% 20% 11% 1	7662
	21st to end	Day	49% 8% 13% 18% 11% 1	9061
June	1st to 10th	Day	42% 9% 14% 21% 13% 1	2940
	11th to 20th	Day	41% 9% 15% 21% 13% 2	2940
	21st to end	Day	39% 9% 16% 21% 14% 1	2940
July	1st to 10th	Day	45% 8% 15% 19% 12% 1	8210
	11th to 20th	Day	35% 7% 16% 29% 12% 1	8205
	21st to end	Day	40% 6% 11% 24% 18% 1	8795
August	1st to 10th	Day	48% 8% 17% 19% 8%	4359
	11th to 20th	Day	39% 8% 15% 27% 9% 1	4242
	21st to end	Day	32% 8% 16% 25% 17% 2	4420
September	1st to 10th	Day	38% 8% 11% 22% 19% 1	2395
	11th to 20th	Day	32% 6% 12% 25% 23% 3	2200
	21st to end	Day	45% 6% 9% 20% 20% 2	2200
October	1st to 10th	Day	37% 4 10% 23% 20% 5%	3590
	11th to 20th	Day	30% 4 9% 25% 28% 4	3189
	21st to end	Day	31% 4 14% 29% 19% 3	3180
November	1st to 10th	Day	39% 6% 13% 20% 20% 2	1851
	11th to 20th	Day	37% 5% 11% 21% 21% 4	1890
	21st to end	Day	42% 5% 10% 27% 13% 3	1890
December	1st to 10th	Day	39% 4 13% 27% 16% 1	2792
	11th to 20th	Day	40% 3 14% 18% 19% 6%	3066
	21st to end	Day	48% 6% 8% 20% 14% 4	4048
January	1st to 10th	Night	37% 4 11% 28% 18% 2	8234
	11th to 20th	Night	46% 3 10% 19% 16% 6%	8280
	21st to end	Night	46% 5% 8% 19% 18% 4	9057
February	1st to 10th	Night	45% 4 12% 23% 14% 2	2601
	11th to 20th	Night	44% 5% 10% 21% 17% 4	2460
	21st to end	Night	46% 5% 9% 22% 14% 4	2076
March	1st to 10th	Night	47% 4 10% 17% 15% 7%	5494
	11th to 20th	Night	44% 7% 16% 19% 11% 3	5307
	21st to end	Night	51% 5% 7% 11% 21% 6%	5264
April	1st to 10th	Night	47% 5% 10% 18% 15% 4	2100
	11th to 20th	Night	45% 6% 11% 17% 18% 2	2075
	21st to end	Night	46% 5% 10% 19% 15% 4	1894
May	1st to 10th	Night	54% 7% 14% 13% 11% 1	5265
	11th to 20th	Night	48% 8% 14% 19% 9% 2	5236
	21st to end	Night	54% 8% 12% 18% 8%	5124
June	1st to 10th	Night	44% 8% 12% 21% 15% 1	1680
	11th to 20th	Night	44% 6% 13% 23% 13% 1	1680
	21st to end	Night	41% 8% 14% 24% 11% 1	1680
July	1st to 10th	Night	50% 6% 12% 19% 12%	4640
	11th to 20th	Night	42% 7% 13% 24% 13% 1	4632
	21st to end	Night	41% 6% 12% 24% 16% 1	4967
August	1st to 10th	Night	50% 10% 13% 17% 9% 1	2951
	11th to 20th	Night	40% 10% 15% 26% 8%	3088
	21st to end	Night	28% 6% 16% 28% 21% 1	3677
September	1st to 10th	Night	40% 7% 10% 24% 17% 1	2005
	11th to 20th	Night	34% 6% 12% 23% 24% 2	2200
	21st to end	Night	47% 7% 8% 17% 18% 3	2200
October	1st to 10th	Night	39% 5% 11% 24% 17% 3	3590
	11th to 20th	Night	26% 4 9% 26% 32% 4	3943
	21st to end	Night	33% 4 12% 28% 21% 3	4610
November	1st to 10th	Night	37% 6% 13% 22% 19% 3	2667
	11th to 20th	Night	40% 5% 9% 23% 19% 4	2730
	21st to end	Night	38% 5% 14% 27% 13% 2	2730
December	1st to 10th	Night	41% 4 12% 27% 16% 1	4602
	11th to 20th	Night	46% 4 12% 16% 19% 2	5348
	21st to end	Night	45% 5% 10% 20% 18% 3	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	20% 25% 34% 17% 3	220
	11th to 20th	Day	21% 30% 37% 9% 3	220
	21st to end	Day	19% 27% 38% 12% 3	242
February	1st to 10th	Day	22% 23% 37% 16% 2	476
	11th to 20th	Day	25% 24% 39% 10% 1	536
	21st to end	Day	22% 23% 38% 14% 3	446
March	1st to 10th	Day	25% 21% 33% 17% 3	540
	11th to 20th	Day	21% 23% 37% 16% 2 1	540
	21st to end	Day	25% 21% 37% 11% 4 1	594
April	1st to 10th	Day	25% 23% 32% 14% 5% 1	540
	11th to 20th	Day	24% 21% 38% 13% 3	532
	21st to end	Day	24% 18% 35% 18% 4 2	540
May	1st to 10th	Day	28% 18% 35% 14% 4	543
	11th to 20th	Day	21% 16% 41% 17% 5% 1	567
	21st to end	Day	18% 11% 35% 27% 7% 1	617
June	1st to 10th	Day	16% 11% 36% 25% 10% 2	570
	11th to 20th	Day	14% 14% 37% 26% 8% 1	570
	21st to end	Day	15% 10% 35% 28% 10% 1	570
July	1st to 10th	Day	16% 7% 26% 36% 13% 2	565
	11th to 20th	Day	12% 7% 28% 37% 15% 2	564
	21st to end	Day	14% 7% 35% 33% 9% 2	620
August	1st to 10th	Day	11% 8% 31% 35% 12% 4	566
	11th to 20th	Day	14% 6% 26% 35% 14% 4	559
	21st to end	Day	12% 5% 34% 29% 14% 6%	619
September	1st to 10th	Day	17% 9% 28% 26% 15% 4	530
	11th to 20th	Day	14% 9% 26% 27% 17% 7%	530
	21st to end	Day	22% 8% 32% 25% 10% 3	530
October	1st to 10th	Day	22% 12% 26% 22% 12% 5%	530
	11th to 20th	Day	18% 17% 31% 21% 11% 2	476
	21st to end	Day	22% 17% 30% 21% 9% 2	462
November	1st to 10th	Day	15% 18% 36% 22% 8% 2	425
	11th to 20th	Day	20% 24% 33% 18% 4	430
	21st to end	Day	23% 21% 32% 18% 6% 1	430
December	1st to 10th	Day	21% 21% 36% 17% 5%	293
	11th to 20th	Day	27% 27% 31% 11% 3	220
	21st to end	Day	21% 21% 37% 13% 5% 2	242
January	1st to 10th	Night	20% 22% 40% 16% 3	840
	11th to 20th	Night	27% 23% 33% 15% 2	840
	21st to end	Night	18% 26% 35% 18% 2	924
February	1st to 10th	Night	21% 19% 39% 20% 1	840
	11th to 20th	Night	24% 22% 40% 14% 1	823
	21st to end	Night	23% 21% 37% 17% 2	692
March	1st to 10th	Night	23% 20% 34% 19% 4	840
	11th to 20th	Night	21% 16% 39% 21% 3	840
	21st to end	Night	25% 16% 38% 18% 3	924
April	1st to 10th	Night	24% 17% 35% 20% 4	840
	11th to 20th	Night	20% 16% 39% 21% 4	831
	21st to end	Night	23% 14% 36% 21% 5%	634
May	1st to 10th	Night	26% 11% 33% 24% 6%	630
	11th to 20th	Night	20% 12% 41% 22% 4	622
	21st to end	Night	23% 6% 27% 36% 7% 1	464
June	1st to 10th	Night	19% 7% 28% 36% 9% 1	420
	11th to 20th	Night	19% 7% 29% 37% 8%	420
	21st to end	Night	18% 5% 26% 39% 11%	420
July	1st to 10th	Night	17% 5% 26% 38% 14%	410
	11th to 20th	Night	15% 4 23% 41% 15% 2	408
	21st to end	Night	15% 2 26% 43% 13% 1	460
August	1st to 10th	Night	13% 3 27% 43% 13% 1	596
	11th to 20th	Night	12% 3 27% 40% 17% 1	682
	21st to end	Night	15% 4 23% 37% 18% 3	917
September	1st to 10th	Night	15% 5% 29% 34% 16% 2	800
	11th to 20th	Night	16% 5% 26% 32% 18% 4	800
	21st to end	Night	24% 7% 26% 29% 14% 2	800
October	1st to 10th	Night	22% 10% 28% 25% 13% 2	800
	11th to 20th	Night	18% 12% 33% 24% 11% 2	800
	21st to end	Night	21% 14% 37% 21% 7%	880
November	1st to 10th	Night	18% 14% 34% 24% 10% 1	820
	11th to 20th	Night	20% 20% 34% 19% 6%	840
	21st to end	Night	19% 21% 32% 23% 5% 1	840
December	1st to 10th	Night	24% 19% 33% 20% 4 1	840
	11th to 20th	Night	23% 22% 36% 16% 3	840
	21st to end	Night	23% 20% 36% 17% 3	924

Page generated at 2026-08-27 04:07:10. Version ac07

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