Leamington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leamington clear sky chart from 2005-11-06 to 2026-05-02.

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	13% 9% 3 8% 5% 5% 5% 4 6% 8% 34%	131380
	Night	14% 10% 4 8% 5% 5% 5% 4 5% 7% 34%	131140
Transparency	Day	46% 6% 13% 22% 12% 1	134977
	Night	49% 6% 11% 20% 12% 1	135613
Seeing	Day	16% 10% 29% 26% 14% 5%	17136
	Night	18% 8% 29% 29% 13% 2	26847

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	13% 14% 7% 14% 7% 5% 5% 4 6% 5% 20%	4691
	11th to 20th	Day	11% 16% 6% 16% 9% 9% 5% 3 3 5% 17%	5068
	21st to end	Day	17% 15% 5% 13% 7% 6% 6% 4 5% 5% 18%	5780
February	1st to 10th	Day	14% 16% 5% 11% 6% 5% 5% 4 5% 5% 25%	1890
	11th to 20th	Day	13% 13% 6% 13% 7% 5% 5% 3 5% 6% 25%	1952
	21st to end	Day	16% 12% 4 11% 6% 5% 4 4 6% 7% 27%	1730
March	1st to 10th	Day	15% 11% 5% 10% 6% 5% 4 3 5% 5% 30%	4800
	11th to 20th	Day	11% 9% 3 10% 6% 5% 5% 3 6% 7% 35%	5090
	21st to end	Day	16% 9% 4 10% 6% 5% 5% 3 6% 7% 29%	5586
April	1st to 10th	Day	14% 10% 4 8% 6% 5% 5% 5% 5% 7% 33%	2373
	11th to 20th	Day	15% 8% 4 7% 5% 5% 5% 4 6% 7% 35%	2699
	21st to end	Day	17% 7% 3 9% 5% 4 4 4 5% 7% 37%	2730
May	1st to 10th	Day	18% 10% 3 8% 5% 4 4 4 5% 7% 32%	5875
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 4 7% 9% 33%	5861
	21st to end	Day	14% 6% 2 7% 4 4 5% 4 6% 8% 41%	6433
June	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 7% 9% 41%	2801
	11th to 20th	Day	8% 5% 2 7% 4 5% 5% 5% 7% 9% 42%	3000
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 8% 10% 42%	2911
July	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 7% 9% 45%	6360
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 4 7% 10% 47%	6186
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 4 6% 9% 45%	6424
August	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 7% 9% 44%	4234
	11th to 20th	Day	8% 5% 3 7% 5% 5% 6% 5% 8% 10% 39%	4174
	21st to end	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 43%	4675
September	1st to 10th	Day	9% 7% 2 5% 4 4 5% 4 5% 9% 46%	2242
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	2200
	21st to end	Day	17% 7% 2 5% 4 5% 4 4 6% 7% 40%	2200
October	1st to 10th	Day	12% 5% 2 7% 5% 4 5% 4 6% 7% 44%	2110
	11th to 20th	Day	16% 7% 2 8% 5% 4 4 3 7% 7% 36%	2000
	21st to end	Day	19% 8% 2 6% 5% 5% 5% 5% 6% 7% 32%	2102
November	1st to 10th	Day	12% 9% 3 7% 4 4 5% 4 6% 7% 38%	1852
	11th to 20th	Day	15% 12% 4 8% 5% 5% 4 4 5% 7% 31%	1890
	21st to end	Day	17% 13% 6% 11% 5% 4 4 3 6% 6% 25%	1717
December	1st to 10th	Day	15% 12% 6% 13% 6% 5% 5% 4 7% 6% 19%	2680
	11th to 20th	Day	19% 18% 5% 10% 7% 4 4 4 5% 5% 19%	3070
	21st to end	Day	24% 18% 6% 12% 6% 5% 4 3 4 5% 13%	3994
January	1st to 10th	Night	14% 14% 5% 12% 6% 5% 5% 4 5% 5% 24%	8232
	11th to 20th	Night	9% 16% 6% 14% 7% 7% 7% 4 5% 5% 19%	7884
	21st to end	Night	17% 15% 6% 10% 4 4 4 3 5% 6% 27%	8401
February	1st to 10th	Night	16% 14% 5% 10% 6% 5% 5% 4 5% 6% 24%	2730
	11th to 20th	Night	15% 13% 4 10% 6% 5% 5% 4 6% 6% 26%	2552
	21st to end	Night	19% 12% 5% 8% 6% 4 4 4 5% 5% 29%	2076
March	1st to 10th	Night	16% 10% 3 8% 5% 4 4 3 5% 6% 34%	5272
	11th to 20th	Night	10% 7% 2 6% 5% 5% 5% 5% 6% 8% 42%	5090
	21st to end	Night	14% 9% 3 8% 5% 5% 4 4 5% 6% 37%	5588
April	1st to 10th	Night	16% 10% 4 7% 6% 4 4 3 5% 6% 35%	2263
	11th to 20th	Night	16% 8% 3 7% 4 4 5% 4 6% 7% 35%	1869
	21st to end	Night	16% 8% 2 7% 4 5% 4 4 5% 6% 39%	1890
May	1st to 10th	Night	21% 9% 3 8% 5% 5% 5% 4 5% 5% 30%	4042
	11th to 20th	Night	15% 8% 3 8% 5% 4 4 4 6% 7% 35%	4032
	21st to end	Night	13% 6% 2 6% 4 4 4 4 6% 8% 43%	4421
June	1st to 10th	Night	12% 5% 2 5% 5% 4 5% 5% 6% 8% 44%	1583
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 5% 6% 7% 44%	1400
	21st to end	Night	8% 5% 2 6% 5% 4 4 4 6% 9% 47%	1481
July	1st to 10th	Night	7% 4 2 6% 4 4 4 4 7% 11% 46%	3618
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 46%	3781
	21st to end	Night	7% 4 2 6% 4 4 5% 4 6% 9% 49%	4427
August	1st to 10th	Night	12% 6% 2 6% 3 4 4 4 6% 8% 44%	2915
	11th to 20th	Night	8% 5% 2 6% 4 4 5% 4 5% 8% 48%	2875
	21st to end	Night	6% 4 2 6% 5% 5% 5% 4 6% 8% 48%	3223
September	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 8% 48%	2132
	11th to 20th	Night	9% 4 1 5% 4 4 4 3 5% 7% 55%	2200
	21st to end	Night	15% 6% 3 7% 4 4 5% 3 5% 7% 42%	2200
October	1st to 10th	Night	13% 5% 2 5% 3 4 4 3 5% 8% 47%	2289
	11th to 20th	Night	17% 8% 3 8% 5% 4 4 2 6% 7% 36%	2400
	21st to end	Night	19% 8% 3 7% 5% 5% 4 3 5% 6% 35%	2735
November	1st to 10th	Night	13% 8% 2 7% 5% 4 4 3 6% 7% 41%	2666
	11th to 20th	Night	17% 11% 3 8% 5% 4 4 3 5% 7% 32%	2730
	21st to end	Night	20% 13% 5% 8% 5% 4 4 4 5% 6% 26%	2899
December	1st to 10th	Night	14% 15% 5% 10% 6% 5% 6% 5% 7% 6% 20%	4720
	11th to 20th	Night	16% 15% 6% 12% 6% 5% 5% 3 4 6% 20%	5345
	21st to end	Night	25% 20% 6% 10% 5% 4 4 2 4 5% 15%	7179

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	63% 7% 11% 13% 5% 1	4692
	11th to 20th	Day	70% 4 7% 8% 10%	5068
	21st to end	Day	65% 6% 11% 13% 5%	5780
February	1st to 10th	Day	60% 5% 10% 17% 7%	1890
	11th to 20th	Day	59% 5% 10% 17% 8% 1	1961
	21st to end	Day	55% 5% 14% 18% 7% 2	1730
March	1st to 10th	Day	53% 5% 12% 21% 8% 1	4800
	11th to 20th	Day	44% 5% 15% 24% 9% 1	5090
	21st to end	Day	51% 7% 13% 20% 10% 1	5586
April	1st to 10th	Day	46% 6% 14% 19% 13% 1	2373
	11th to 20th	Day	46% 5% 12% 22% 12% 2	2699
	21st to end	Day	46% 5% 13% 23% 11% 2	2730
May	1st to 10th	Day	50% 6% 10% 19% 13% 2	5910
	11th to 20th	Day	46% 8% 14% 19% 11% 2	5865
	21st to end	Day	38% 7% 13% 22% 14% 6%	6447
June	1st to 10th	Day	37% 6% 13% 29% 13% 2	2801
	11th to 20th	Day	35% 8% 16% 23% 16% 2	3000
	21st to end	Day	32% 9% 15% 26% 16% 3	2911
July	1st to 10th	Day	33% 6% 13% 29% 18% 2	6291
	11th to 20th	Day	29% 7% 16% 30% 17% 2	6111
	21st to end	Day	34% 7% 15% 22% 20% 3	6240
August	1st to 10th	Day	34% 6% 16% 30% 14% 1	4221
	11th to 20th	Day	35% 8% 14% 33% 9% 1	4213
	21st to end	Day	33% 7% 15% 30% 13% 1	4674
September	1st to 10th	Day	33% 6% 17% 26% 16% 2	2242
	11th to 20th	Day	31% 6% 14% 32% 17% 1	2200
	21st to end	Day	42% 6% 13% 24% 15% 1	2200
October	1st to 10th	Day	28% 5% 15% 31% 19% 1	3435
	11th to 20th	Day	38% 5% 13% 27% 17%	3240
	21st to end	Day	42% 5% 15% 23% 14% 1	3378
November	1st to 10th	Day	44% 7% 13% 23% 13% 1	1852
	11th to 20th	Day	53% 4 14% 18% 9% 1	1890
	21st to end	Day	59% 5% 14% 17% 4	1717
December	1st to 10th	Day	62% 11% 13% 10% 4	2680
	11th to 20th	Day	66% 6% 11% 13% 3	3066
	21st to end	Day	73% 5% 9% 8% 4	3994
January	1st to 10th	Night	61% 6% 10% 14% 7% 1	8233
	11th to 20th	Night	66% 5% 8% 12% 8% 1	7884
	21st to end	Night	58% 5% 12% 17% 9%	8401
February	1st to 10th	Night	60% 5% 11% 17% 6% 1	2730
	11th to 20th	Night	57% 5% 11% 18% 8% 1	2554
	21st to end	Night	57% 4 11% 18% 8% 1	2076
March	1st to 10th	Night	49% 4 15% 21% 10% 1	5272
	11th to 20th	Night	38% 6% 15% 26% 14% 1	5090
	21st to end	Night	48% 5% 10% 21% 15% 1	5588
April	1st to 10th	Night	51% 4 11% 19% 13% 2	2263
	11th to 20th	Night	46% 6% 11% 19% 16% 2	1869
	21st to end	Night	44% 4 10% 22% 15% 4	1890
May	1st to 10th	Night	55% 6% 8% 14% 14% 4	4069
	11th to 20th	Night	47% 7% 9% 25% 10% 3	4033
	21st to end	Night	38% 7% 12% 23% 16% 4	4429
June	1st to 10th	Night	37% 5% 11% 25% 18% 3	1583
	11th to 20th	Night	37% 7% 14% 24% 16% 3	1400
	21st to end	Night	34% 7% 12% 25% 21% 1	1481
July	1st to 10th	Night	30% 7% 15% 27% 17% 4	3580
	11th to 20th	Night	33% 7% 14% 27% 17% 2	3736
	21st to end	Night	31% 6% 14% 21% 25% 2	4297
August	1st to 10th	Night	37% 6% 13% 27% 15% 2	2904
	11th to 20th	Night	34% 7% 9% 34% 14% 1	2902
	21st to end	Night	32% 7% 12% 31% 16% 1	3223
September	1st to 10th	Night	33% 7% 13% 28% 16% 3	2132
	11th to 20th	Night	30% 5% 12% 31% 20% 2	2200
	21st to end	Night	43% 5% 12% 22% 17% 1	2200
October	1st to 10th	Night	26% 5% 10% 30% 28% 1	3744
	11th to 20th	Night	42% 5% 11% 24% 18% 1	3899
	21st to end	Night	40% 4 11% 29% 15% 1	4409
November	1st to 10th	Night	44% 4 13% 23% 15% 1	2666
	11th to 20th	Night	55% 4 13% 18% 10% 1	2730
	21st to end	Night	60% 5% 13% 18% 5%	2899
December	1st to 10th	Night	63% 10% 12% 12% 3	4720
	11th to 20th	Night	65% 6% 13% 12% 4	5348
	21st to end	Night	73% 4 9% 9% 4	7179

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% 14% 40% 18% 6% 1	330
	11th to 20th	Day	23% 18% 40% 14% 4 1	330
	21st to end	Day	26% 15% 31% 23% 5%	363
February	1st to 10th	Day	22% 15% 34% 22% 5% 1	330
	11th to 20th	Day	22% 16% 38% 20% 4	330
	21st to end	Day	21% 18% 43% 17% 1	273
March	1st to 10th	Day	24% 15% 38% 20% 4	420
	11th to 20th	Day	23% 16% 32% 22% 6% 1	540
	21st to end	Day	23% 16% 32% 24% 5%	594
April	1st to 10th	Day	19% 13% 37% 24% 6% 1	540
	11th to 20th	Day	20% 15% 33% 18% 9% 5%	532
	21st to end	Day	19% 12% 35% 21% 10% 3	540
May	1st to 10th	Day	23% 11% 30% 22% 11% 3	507
	11th to 20th	Day	17% 8% 30% 26% 14% 5%	527
	21st to end	Day	13% 7% 23% 31% 19% 6%	573
June	1st to 10th	Day	12% 6% 30% 33% 14% 4	581
	11th to 20th	Day	11% 6% 29% 35% 17% 2	730
	21st to end	Day	10% 5% 29% 35% 16% 5%	730
July	1st to 10th	Day	11% 4 22% 30% 24% 10%	721
	11th to 20th	Day	10% 4 22% 33% 21% 9%	648
	21st to end	Day	9% 4 18% 31% 29% 9%	576
August	1st to 10th	Day	8% 3 17% 30% 26% 15%	526
	11th to 20th	Day	9% 4 15% 32% 29% 11%	519
	21st to end	Day	8% 3 19% 28% 28% 14%	583
September	1st to 10th	Day	9% 5% 22% 28% 22% 13%	530
	11th to 20th	Day	7% 2 15% 28% 34% 15%	530
	21st to end	Day	20% 6% 21% 26% 19% 9%	530
October	1st to 10th	Day	12% 8% 24% 28% 21% 8%	530
	11th to 20th	Day	16% 11% 35% 27% 10% 2	530
	21st to end	Day	23% 16% 35% 20% 6% 1	485
November	1st to 10th	Day	17% 15% 34% 22% 11% 2	330
	11th to 20th	Day	16% 23% 32% 22% 6% 2	330
	21st to end	Day	21% 15% 40% 21% 3	239
December	1st to 10th	Day	22% 16% 36% 20% 5% 1	220
	11th to 20th	Day	25% 16% 36% 18% 5%	220
	21st to end	Day	24% 17% 39% 16% 4	319
January	1st to 10th	Night	23% 12% 39% 20% 6% 1	1050
	11th to 20th	Night	26% 15% 36% 20% 4	914
	21st to end	Night	21% 11% 37% 25% 6%	924
February	1st to 10th	Night	25% 10% 36% 26% 3	840
	11th to 20th	Night	22% 11% 36% 25% 6%	823
	21st to end	Night	24% 12% 41% 20% 2	692
March	1st to 10th	Night	21% 10% 37% 26% 7%	840
	11th to 20th	Night	18% 11% 39% 26% 5% 1	840
	21st to end	Night	21% 11% 33% 27% 9% 1	924
April	1st to 10th	Night	20% 11% 34% 29% 5%	793
	11th to 20th	Night	19% 9% 36% 27% 7% 1	623
	21st to end	Night	18% 7% 34% 30% 10%	630
May	1st to 10th	Night	20% 5% 30% 34% 10% 2	603
	11th to 20th	Night	20% 5% 24% 34% 16% 1	591
	21st to end	Night	12% 4 22% 35% 25% 3	650
June	1st to 10th	Night	13% 3 28% 39% 17% 1	440
	11th to 20th	Night	11% 3 21% 44% 21%	400
	21st to end	Night	10% 6% 20% 46% 17% 2	481
July	1st to 10th	Night	8% 2 13% 41% 30% 5%	585
	11th to 20th	Night	9% 2 16% 40% 27% 5%	582
	21st to end	Night	7% 2 14% 44% 30% 3	657
August	1st to 10th	Night	9% 1 12% 42% 29% 7%	597
	11th to 20th	Night	8% 2 14% 38% 33% 5%	594
	21st to end	Night	9% 3 12% 40% 30% 5%	660
September	1st to 10th	Night	11% 4 15% 33% 31% 6%	762
	11th to 20th	Night	10% 3 15% 32% 33% 7%	800
	21st to end	Night	17% 6% 19% 32% 22% 6%	800
October	1st to 10th	Night	15% 4 25% 30% 21% 5%	800
	11th to 20th	Night	19% 11% 31% 26% 12% 2	800
	21st to end	Night	21% 13% 31% 29% 6%	880
November	1st to 10th	Night	18% 10% 30% 28% 12% 2	820
	11th to 20th	Night	21% 14% 34% 22% 8% 1	840
	21st to end	Night	27% 12% 33% 21% 7%	840
December	1st to 10th	Night	24% 14% 34% 21% 7% 1	840
	11th to 20th	Night	24% 12% 38% 22% 4	840
	21st to end	Night	28% 12% 33% 24% 3	1092

Page generated at 2026-04-29 02:21:45. Version ac07

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