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 2024-10-25.

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% 39%	101089
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 40%	97728
Transparency	Day	43% 7% 13% 20% 14% 2	100847
	Night	45% 7% 12% 20% 14% 2	97590
Seeing	Day	19% 16% 33% 22% 8% 2	15093
	Night	20% 14% 33% 25% 8% 1	23993

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% 7% 2 6% 3 4 4 3 5% 5% 46%	2517
	11th to 20th	Day	17% 7% 3 7% 5% 4 5% 3 4 5% 40%	2520
	21st to end	Day	22% 11% 4 6% 4 3 3 3 4 4 35%	2772
February	1st to 10th	Day	18% 8% 2 5% 3 5% 5% 3 6% 6% 38%	1818
	11th to 20th	Day	14% 7% 2 5% 5% 4 5% 4 5% 7% 43%	1848
	21st to end	Day	20% 7% 3 6% 3 4 4 4 4 6% 38%	1570
March	1st to 10th	Day	25% 12% 3 6% 4 4 3 2 4 5% 32%	3116
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 6% 7% 47%	3338
	21st to end	Day	22% 9% 2 6% 4 4 4 4 5% 5% 36%	4031
April	1st to 10th	Day	18% 8% 3 5% 4 3 4 3 6% 7% 38%	2280
	11th to 20th	Day	18% 7% 2 5% 3 4 4 3 6% 7% 41%	2254
	21st to end	Day	21% 7% 2 6% 4 4 4 3 5% 6% 38%	2465
May	1st to 10th	Day	27% 11% 3 7% 3 3 3 3 4 6% 30%	4106
	11th to 20th	Day	24% 8% 3 8% 5% 5% 3 3 5% 6% 33%	4100
	21st to end	Day	15% 5% 1 5% 4 4 4 4 5% 8% 45%	4837
June	1st to 10th	Day	18% 6% 2 5% 5% 5% 5% 4 7% 8% 35%	2660
	11th to 20th	Day	14% 6% 2 5% 5% 5% 5% 4 7% 8% 37%	2660
	21st to end	Day	14% 6% 2 6% 4 5% 4 4 6% 10% 39%	2660
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 6% 5% 7% 9% 35%	4440
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 4 7% 10% 38%	4440
	21st to end	Day	19% 7% 3 6% 5% 4 5% 4 6% 8% 32%	4814
August	1st to 10th	Day	17% 7% 3 8% 5% 5% 5% 4 6% 9% 31%	4113
	11th to 20th	Day	12% 6% 3 7% 5% 4 6% 4 6% 8% 39%	3949
	21st to end	Day	7% 4 2 5% 4 5% 6% 5% 7% 8% 45%	4180
September	1st to 10th	Day	14% 6% 3 5% 4 4 4 4 5% 6% 45%	2275
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 5% 6% 51%	2090
	21st to end	Day	19% 6% 2 6% 4 4 4 3 4 5% 43%	2090
October	1st to 10th	Day	23% 6% 2 5% 3 4 3 2 4 5% 42%	2090
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 5% 7% 48%	1875
	21st to end	Day	19% 5% 2 5% 4 4 4 3 5% 4 44%	1825
November	1st to 10th	Day	16% 7% 2 5% 4 3 4 3 4 5% 47%	1671
	11th to 20th	Day	17% 6% 2 4 3 3 4 4 5% 7% 45%	1710
	21st to end	Day	17% 6% 2 6% 4 3 4 3 4 5% 45%	1710
December	1st to 10th	Day	18% 8% 3 6% 4 3 5% 3 6% 6% 39%	1587
	11th to 20th	Day	21% 6% 2 4 4 3 3 2 3 5% 46%	1906
	21st to end	Day	19% 10% 3 7% 5% 5% 4 3 4 5% 36%	2772
January	1st to 10th	Night	17% 7% 2 4 3 3 3 3 4 5% 49%	4429
	11th to 20th	Night	17% 10% 4 7% 4 4 3 3 4 4 41%	4440
	21st to end	Night	22% 12% 4 8% 4 4 4 3 4 4 31%	4884
February	1st to 10th	Night	16% 9% 3 5% 5% 4 4 3 4 5% 41%	2355
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 5% 6% 41%	2218
	21st to end	Night	18% 9% 2 5% 4 4 4 3 4 4 42%	1884
March	1st to 10th	Night	28% 11% 2 4 3 4 3 3 4 6% 34%	3724
	11th to 20th	Night	10% 8% 2 6% 5% 4 4 3 5% 7% 44%	3621
	21st to end	Night	25% 8% 2 6% 4 4 4 3 5% 5% 34%	3598
April	1st to 10th	Night	18% 9% 3 6% 4 4 5% 3 5% 6% 38%	1900
	11th to 20th	Night	19% 8% 2 6% 4 4 4 4 5% 6% 39%	1875
	21st to end	Night	20% 7% 3 7% 4 4 3 3 4 5% 41%	1714
May	1st to 10th	Night	26% 9% 3 7% 5% 3 4 3 5% 6% 28%	2834
	11th to 20th	Night	25% 9% 3 8% 5% 5% 4 3 5% 6% 26%	2813
	21st to end	Night	17% 7% 2 6% 4 4 4 4 6% 8% 39%	2747
June	1st to 10th	Night	17% 7% 3 7% 5% 4 4 4 6% 7% 38%	1520
	11th to 20th	Night	17% 7% 2 5% 5% 4 4 3 6% 8% 39%	1520
	21st to end	Night	15% 8% 2 5% 4 3 4 4 6% 10% 39%	1520
July	1st to 10th	Night	14% 8% 3 7% 5% 5% 6% 5% 6% 10% 32%	2520
	11th to 20th	Night	14% 7% 2 6% 4 4 5% 5% 7% 9% 37%	2520
	21st to end	Night	18% 8% 3 7% 5% 4 5% 4 6% 8% 31%	2739
August	1st to 10th	Night	21% 7% 2 7% 5% 4 6% 4 7% 9% 29%	2784
	11th to 20th	Night	9% 7% 3 7% 6% 6% 7% 6% 7% 8% 36%	2875
	21st to end	Night	8% 4 1 5% 3 4 3 3 5% 7% 56%	3476
September	1st to 10th	Night	13% 6% 3 7% 5% 4 4 4 5% 6% 44%	1905
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 4 7% 51%	2090
	21st to end	Night	19% 8% 3 6% 4 3 4 3 4 5% 41%	2090
October	1st to 10th	Night	20% 6% 2 6% 4 3 4 3 4 6% 42%	2090
	11th to 20th	Night	15% 4 2 4 4 4 4 3 5% 7% 49%	2299
	21st to end	Night	20% 6% 3 5% 4 4 3 2 5% 6% 41%	2637
November	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 4 5% 48%	2407
	11th to 20th	Night	18% 7% 2 5% 3 3 4 3 3 6% 46%	2470
	21st to end	Night	15% 6% 2 4 3 4 4 3 5% 7% 47%	2470
December	1st to 10th	Night	19% 8% 2 6% 4 4 3 3 5% 5% 41%	2588
	11th to 20th	Night	19% 7% 1 6% 4 3 4 3 5% 6% 43%	3288
	21st to end	Night	20% 11% 3 7% 4 3 3 2 4 5% 37%	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	39% 6% 9% 28% 14% 2	2518
	11th to 20th	Day	45% 8% 10% 24% 12% 2	2520
	21st to end	Day	52% 5% 8% 21% 12% 1	2772
February	1st to 10th	Day	45% 6% 14% 19% 14% 3	1818
	11th to 20th	Day	41% 6% 11% 23% 15% 3	1857
	21st to end	Day	46% 6% 12% 19% 13% 3	1570
March	1st to 10th	Day	52% 6% 13% 15% 11% 3	3119
	11th to 20th	Day	30% 9% 16% 29% 14% 2	3338
	21st to end	Day	50% 5% 8% 16% 16% 5%	4031
April	1st to 10th	Day	43% 8% 12% 19% 16% 3	2280
	11th to 20th	Day	42% 7% 9% 21% 18% 3	2254
	21st to end	Day	45% 8% 10% 19% 15% 4	2465
May	1st to 10th	Day	54% 9% 14% 12% 9% 1	4120
	11th to 20th	Day	50% 9% 15% 15% 9% 2	4104
	21st to end	Day	36% 10% 15% 21% 18% 2	4837
June	1st to 10th	Day	43% 10% 15% 20% 11% 1	2660
	11th to 20th	Day	41% 9% 15% 21% 13% 1	2660
	21st to end	Day	40% 10% 15% 22% 13% 1	2660
July	1st to 10th	Day	44% 9% 13% 18% 14% 1	4370
	11th to 20th	Day	40% 8% 17% 23% 11% 1	4365
	21st to end	Day	47% 8% 14% 17% 13% 2	4661
August	1st to 10th	Day	49% 8% 17% 19% 7%	4099
	11th to 20th	Day	40% 8% 15% 27% 9% 1	3988
	21st to end	Day	32% 8% 17% 25% 17% 2	4180
September	1st to 10th	Day	38% 8% 11% 22% 20% 1	2275
	11th to 20th	Day	32% 6% 12% 24% 22% 3	2090
	21st to end	Day	44% 6% 8% 19% 20% 2	2090
October	1st to 10th	Day	44% 6% 10% 20% 16% 4	2090
	11th to 20th	Day	35% 6% 12% 27% 18% 2	1875
	21st to end	Day	42% 5% 13% 22% 15% 4	1825
November	1st to 10th	Day	39% 7% 13% 20% 19% 2	1671
	11th to 20th	Day	39% 5% 12% 21% 20% 3	1710
	21st to end	Day	41% 5% 11% 27% 12% 3	1710
December	1st to 10th	Day	46% 6% 13% 16% 17% 2	1587
	11th to 20th	Day	43% 4 14% 17% 17% 6%	1906
	21st to end	Day	49% 8% 12% 20% 10% 1	2772
January	1st to 10th	Night	37% 5% 12% 31% 12% 3	4429
	11th to 20th	Night	46% 5% 12% 22% 12% 3	4440
	21st to end	Night	55% 7% 9% 17% 11% 2	4884
February	1st to 10th	Night	46% 5% 13% 22% 13% 2	2355
	11th to 20th	Night	45% 5% 10% 19% 17% 4	2220
	21st to end	Night	46% 5% 9% 22% 15% 4	1884
March	1st to 10th	Night	53% 5% 10% 18% 12% 2	3734
	11th to 20th	Night	37% 9% 17% 20% 15% 2	3622
	21st to end	Night	51% 5% 7% 12% 19% 6%	3598
April	1st to 10th	Night	46% 6% 11% 19% 15% 3	1900
	11th to 20th	Night	45% 6% 10% 18% 18% 2	1875
	21st to end	Night	47% 5% 10% 20% 14% 5%	1714
May	1st to 10th	Night	56% 10% 13% 13% 8% 1	2840
	11th to 20th	Night	56% 10% 13% 13% 7% 2	2814
	21st to end	Night	43% 12% 15% 18% 11% 1	2748
June	1st to 10th	Night	45% 8% 13% 19% 13% 1	1520
	11th to 20th	Night	43% 7% 13% 24% 13% 1	1520
	21st to end	Night	42% 8% 15% 24% 11% 1	1520
July	1st to 10th	Night	49% 8% 12% 18% 12% 1	2480
	11th to 20th	Night	42% 10% 16% 23% 9% 1	2472
	21st to end	Night	50% 7% 14% 15% 12% 2	2651
August	1st to 10th	Night	51% 10% 13% 16% 8% 1	2774
	11th to 20th	Night	41% 11% 15% 25% 8%	2902
	21st to end	Night	27% 6% 17% 28% 21% 1	3476
September	1st to 10th	Night	41% 7% 10% 23% 17% 2	1905
	11th to 20th	Night	34% 6% 12% 22% 23% 2	2090
	21st to end	Night	46% 7% 8% 17% 19% 3	2090
October	1st to 10th	Night	45% 6% 11% 20% 14% 4	2090
	11th to 20th	Night	36% 6% 13% 27% 17% 1	2299
	21st to end	Night	44% 5% 13% 21% 14% 2	2637
November	1st to 10th	Night	39% 6% 13% 21% 18% 4	2407
	11th to 20th	Night	42% 5% 10% 23% 18% 3	2470
	21st to end	Night	38% 5% 14% 27% 13% 2	2470
December	1st to 10th	Night	46% 6% 13% 20% 15% 1	2588
	11th to 20th	Night	42% 6% 13% 19% 17% 2	3288
	21st to end	Night	49% 6% 11% 22% 12% 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	21% 25% 33% 17% 4	180
	11th to 20th	Day	21% 31% 34% 11% 4	180
	21st to end	Day	19% 26% 37% 13% 4 1	198
February	1st to 10th	Day	25% 23% 35% 15% 1	403
	11th to 20th	Day	25% 25% 39% 10% 2	456
	21st to end	Day	23% 24% 35% 15% 3	382
March	1st to 10th	Day	24% 22% 34% 18% 2	460
	11th to 20th	Day	21% 24% 36% 15% 2 1	460
	21st to end	Day	26% 19% 37% 11% 5% 1	506
April	1st to 10th	Day	24% 24% 32% 15% 5%	460
	11th to 20th	Day	23% 22% 36% 14% 4	452
	21st to end	Day	25% 18% 34% 15% 5% 2	460
May	1st to 10th	Day	29% 18% 33% 15% 4	463
	11th to 20th	Day	20% 17% 40% 17% 5% 1	487
	21st to end	Day	16% 11% 35% 28% 8% 2	529
June	1st to 10th	Day	17% 11% 37% 25% 9% 2	490
	11th to 20th	Day	13% 13% 37% 27% 8% 1	490
	21st to end	Day	15% 11% 36% 29% 7% 1	490
July	1st to 10th	Day	15% 8% 28% 34% 14% 2	485
	11th to 20th	Day	12% 7% 27% 37% 15% 2	484
	21st to end	Day	14% 8% 35% 33% 9% 1	532
August	1st to 10th	Day	12% 8% 32% 35% 11% 3	486
	11th to 20th	Day	16% 6% 27% 34% 14% 4	479
	21st to end	Day	11% 6% 32% 30% 14% 7%	539
September	1st to 10th	Day	17% 9% 27% 27% 15% 4	490
	11th to 20th	Day	14% 9% 28% 26% 16% 7%	490
	21st to end	Day	22% 9% 32% 25% 9% 3	490
October	1st to 10th	Day	24% 11% 27% 22% 11% 5%	490
	11th to 20th	Day	16% 17% 31% 22% 11% 2	441
	21st to end	Day	22% 16% 30% 20% 10% 1	411
November	1st to 10th	Day	15% 17% 35% 22% 8% 2	365
	11th to 20th	Day	22% 24% 30% 18% 5%	370
	21st to end	Day	21% 21% 31% 19% 7% 1	370
December	1st to 10th	Day	23% 21% 35% 17% 4	247
	11th to 20th	Day	28% 25% 33% 11% 3	180
	21st to end	Day	21% 21% 39% 13% 6% 2	198
January	1st to 10th	Night	20% 21% 39% 17% 3	760
	11th to 20th	Night	27% 22% 34% 15% 3	760
	21st to end	Night	19% 24% 36% 18% 3	836
February	1st to 10th	Night	21% 19% 38% 20% 1	760
	11th to 20th	Night	23% 22% 41% 12% 1	743
	21st to end	Night	24% 21% 36% 17% 2	628
March	1st to 10th	Night	23% 19% 35% 19% 4	760
	11th to 20th	Night	20% 16% 40% 20% 3	760
	21st to end	Night	25% 16% 37% 18% 4	836
April	1st to 10th	Night	23% 17% 36% 21% 3	760
	11th to 20th	Night	20% 16% 38% 22% 4	751
	21st to end	Night	24% 14% 36% 21% 6%	574
May	1st to 10th	Night	26% 11% 31% 25% 6%	570
	11th to 20th	Night	21% 12% 40% 22% 4 1	562
	21st to end	Night	22% 5% 28% 36% 8% 1	420
June	1st to 10th	Night	19% 7% 28% 36% 9% 1	380
	11th to 20th	Night	19% 6% 28% 38% 9%	380
	21st to end	Night	19% 6% 26% 39% 10%	380
July	1st to 10th	Night	16% 5% 27% 38% 14% 1	370
	11th to 20th	Night	15% 4 22% 43% 14% 1	368
	21st to end	Night	15% 2 27% 42% 14%	416
August	1st to 10th	Night	13% 4 28% 43% 12%	539
	11th to 20th	Night	12% 3 27% 39% 18%	616
	21st to end	Night	14% 4 21% 38% 19% 3	836
September	1st to 10th	Night	15% 4 29% 34% 16% 2	760
	11th to 20th	Night	16% 6% 26% 30% 18% 4	760
	21st to end	Night	23% 7% 26% 29% 13% 2	760
October	1st to 10th	Night	23% 10% 27% 25% 13% 2	760
	11th to 20th	Night	18% 12% 34% 24% 11% 2	760
	21st to end	Night	22% 13% 37% 20% 8%	812
November	1st to 10th	Night	17% 13% 34% 24% 11% 1	740
	11th to 20th	Night	21% 19% 34% 18% 6%	760
	21st to end	Night	19% 21% 33% 21% 6% 1	760
December	1st to 10th	Night	25% 18% 33% 20% 4 1	760
	11th to 20th	Night	21% 22% 36% 17% 3 1	760
	21st to end	Night	23% 20% 37% 17% 3	836

Page generated at 2024-10-22 20:21:02. Version ac07

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