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 2025-01-07.

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%	104806
	Night	15% 10% 4 8% 5% 4 5% 4 5% 7% 33%	104173
Transparency	Day	45% 6% 13% 22% 12% 1	108447
	Night	49% 5% 12% 20% 12% 1	108671
Seeing	Day	16% 9% 28% 26% 15% 5%	15398
	Night	19% 8% 29% 30% 13% 2	25094

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	16% 17% 8% 13% 7% 5% 5% 3 5% 4 17%	2575
	11th to 20th	Day	15% 17% 7% 14% 8% 12% 5% 2 4 4 10%	2719
	21st to end	Day	26% 18% 6% 13% 6% 5% 4 2 4 4 13%	3124
February	1st to 10th	Day	15% 17% 4 11% 6% 5% 5% 4 5% 5% 24%	1710
	11th to 20th	Day	14% 13% 5% 12% 7% 5% 5% 3 5% 6% 25%	1761
	21st to end	Day	17% 12% 3 10% 5% 4 4 4 5% 6% 28%	1570
March	1st to 10th	Day	18% 12% 4 9% 6% 4 4 3 5% 6% 29%	3266
	11th to 20th	Day	12% 10% 4 10% 6% 5% 5% 3 5% 7% 33%	3480
	21st to end	Day	17% 9% 4 8% 6% 5% 4 3 6% 7% 31%	3815
April	1st to 10th	Day	12% 10% 4 7% 6% 5% 5% 5% 5% 7% 34%	2147
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 7% 35%	2439
	21st to end	Day	18% 8% 3 8% 5% 4 3 4 5% 7% 36%	2470
May	1st to 10th	Day	16% 8% 3 7% 5% 5% 4 4 6% 8% 35%	4082
	11th to 20th	Day	17% 7% 2 6% 4 5% 5% 4 7% 10% 33%	4081
	21st to end	Day	8% 5% 2 7% 4 4 5% 4 6% 8% 47%	4476
June	1st to 10th	Day	10% 6% 2 6% 5% 4 5% 5% 7% 10% 40%	2660
	11th to 20th	Day	8% 5% 2 7% 4 4 5% 5% 7% 9% 43%	2850
	21st to end	Day	9% 5% 2 6% 5% 4 5% 4 8% 10% 42%	2766
July	1st to 10th	Day	9% 6% 2 6% 4 5% 5% 4 6% 9% 44%	4440
	11th to 20th	Day	7% 4 2 4 4 4 5% 4 7% 10% 49%	4322
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 8% 45%	4466
August	1st to 10th	Day	12% 5% 2 5% 4 4 5% 3 7% 9% 44%	4104
	11th to 20th	Day	8% 5% 3 7% 5% 5% 6% 5% 8% 10% 38%	4044
	21st to end	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 43%	4532
September	1st to 10th	Day	9% 7% 2 5% 5% 4 5% 4 5% 8% 46%	2130
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 48%	2090
	21st to end	Day	17% 7% 2 5% 4 5% 3 4 6% 7% 40%	2090
October	1st to 10th	Day	12% 5% 2 7% 5% 4 5% 4 6% 7% 43%	2005
	11th to 20th	Day	17% 7% 2 8% 5% 4 4 3 7% 7% 35%	1900
	21st to end	Day	19% 8% 2 6% 5% 5% 6% 5% 6% 6% 31%	1997
November	1st to 10th	Day	11% 9% 3 7% 5% 5% 5% 4 6% 7% 39%	1762
	11th to 20th	Day	15% 12% 4 8% 5% 5% 5% 4 5% 7% 31%	1800
	21st to end	Day	18% 13% 6% 11% 5% 4 5% 3 6% 6% 25%	1635
December	1st to 10th	Day	15% 12% 6% 13% 6% 5% 5% 4 7% 6% 19%	2600
	11th to 20th	Day	20% 18% 5% 9% 7% 4 4 4 5% 5% 19%	2990
	21st to end	Day	24% 18% 6% 12% 6% 5% 4 3 4 5% 13%	3908
January	1st to 10th	Night	15% 16% 5% 11% 6% 5% 5% 4 5% 5% 24%	4513
	11th to 20th	Night	15% 20% 7% 13% 5% 7% 9% 3 4 3 13%	4240
	21st to end	Night	27% 17% 7% 10% 4 4 3 3 4 4 18%	4532
February	1st to 10th	Night	16% 15% 4 10% 6% 5% 5% 4 5% 6% 24%	2470
	11th to 20th	Night	15% 13% 4 10% 6% 5% 5% 4 6% 5% 27%	2304
	21st to end	Night	20% 11% 5% 8% 5% 4 5% 4 5% 4 29%	1884
March	1st to 10th	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 34%	3586
	11th to 20th	Night	10% 7% 2 6% 5% 5% 5% 5% 6% 8% 41%	3480
	21st to end	Night	15% 9% 3 8% 4 5% 4 4 5% 6% 37%	3817
April	1st to 10th	Night	15% 10% 4 7% 6% 4 4 3 5% 6% 36%	2047
	11th to 20th	Night	17% 8% 3 7% 4 4 5% 4 6% 8% 35%	1689
	21st to end	Night	16% 8% 2 7% 4 5% 4 4 6% 6% 39%	1710
May	1st to 10th	Night	19% 8% 3 7% 5% 5% 5% 4 5% 6% 33%	2813
	11th to 20th	Night	14% 8% 3 8% 5% 5% 5% 4 7% 8% 34%	2812
	21st to end	Night	9% 6% 2 5% 3 4 4 4 6% 8% 49%	3079
June	1st to 10th	Night	12% 5% 2 5% 5% 4 5% 5% 6% 8% 44%	1504
	11th to 20th	Night	10% 5% 2 6% 4 5% 5% 5% 6% 7% 44%	1330
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 6% 9% 46%	1407
July	1st to 10th	Night	9% 4 2 5% 4 4 4 3 6% 11% 49%	2530
	11th to 20th	Night	9% 4 1 5% 3 3 4 3 6% 9% 51%	2642
	21st to end	Night	5% 4 2 6% 5% 4 5% 5% 7% 11% 46%	3087
August	1st to 10th	Night	13% 7% 2 6% 3 4 4 4 5% 8% 44%	2825
	11th to 20th	Night	8% 5% 3 6% 4 4 5% 4 5% 8% 48%	2785
	21st to end	Night	6% 4 2 6% 5% 5% 5% 4 6% 8% 48%	3124
September	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 8% 48%	2025
	11th to 20th	Night	9% 4 1 6% 4 5% 4 3 5% 7% 53%	2090
	21st to end	Night	15% 6% 2 7% 4 4 5% 3 5% 7% 42%	2090
October	1st to 10th	Night	14% 5% 2 5% 3 4 4 3 5% 8% 46%	2174
	11th to 20th	Night	17% 8% 3 8% 5% 4 4 2 6% 7% 36%	2280
	21st to end	Night	20% 8% 3 7% 5% 5% 4 3 5% 6% 34%	2598
November	1st to 10th	Night	13% 8% 2 7% 5% 4 4 3 6% 7% 42%	2536
	11th to 20th	Night	17% 11% 3 9% 5% 4 4 3 5% 6% 31%	2600
	21st to end	Night	20% 13% 5% 7% 5% 4 4 4 6% 6% 27%	2761
December	1st to 10th	Night	14% 15% 5% 10% 6% 5% 6% 5% 7% 6% 20%	4580
	11th to 20th	Night	17% 16% 6% 12% 6% 5% 5% 3 4 6% 20%	5205
	21st to end	Night	26% 20% 6% 10% 5% 4 4 2 4 5% 15%	7024

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	68% 6% 11% 10% 5%	2576
	11th to 20th	Day	78% 4 9% 7% 2	2719
	21st to end	Day	73% 5% 10% 8% 3	3124
February	1st to 10th	Day	60% 5% 11% 16% 7% 1	1710
	11th to 20th	Day	58% 5% 10% 17% 8% 1	1770
	21st to end	Day	55% 5% 14% 18% 7% 2	1570
March	1st to 10th	Day	55% 6% 11% 22% 5% 1	3266
	11th to 20th	Day	47% 6% 15% 21% 9% 2	3480
	21st to end	Day	50% 6% 13% 20% 9% 1	3815
April	1st to 10th	Day	45% 6% 14% 19% 14% 1	2147
	11th to 20th	Day	46% 5% 13% 21% 13% 2	2439
	21st to end	Day	46% 4 13% 22% 11% 3	2470
May	1st to 10th	Day	46% 7% 11% 24% 11% 2	4120
	11th to 20th	Day	45% 9% 16% 21% 9% 1	4085
	21st to end	Day	33% 7% 13% 22% 18% 7%	4489
June	1st to 10th	Day	37% 6% 13% 29% 13% 2	2660
	11th to 20th	Day	34% 8% 16% 23% 17% 2	2850
	21st to end	Day	32% 9% 15% 26% 15% 3	2766
July	1st to 10th	Day	36% 6% 13% 24% 19% 2	4371
	11th to 20th	Day	27% 6% 14% 33% 18% 1	4247
	21st to end	Day	33% 8% 17% 19% 20% 3	4324
August	1st to 10th	Day	34% 6% 15% 30% 14% 1	4091
	11th to 20th	Day	35% 8% 14% 33% 9% 1	4083
	21st to end	Day	33% 7% 15% 29% 14% 1	4531
September	1st to 10th	Day	34% 7% 18% 25% 16% 2	2130
	11th to 20th	Day	32% 6% 14% 30% 17% 1	2090
	21st to end	Day	42% 7% 13% 24% 14% 1	2090
October	1st to 10th	Day	29% 5% 16% 31% 18% 1	3330
	11th to 20th	Day	38% 5% 13% 26% 17%	3140
	21st to end	Day	42% 5% 15% 23% 13%	3273
November	1st to 10th	Day	44% 7% 13% 23% 13% 1	1762
	11th to 20th	Day	54% 4 15% 17% 10% 1	1800
	21st to end	Day	59% 5% 14% 17% 5%	1635
December	1st to 10th	Day	62% 11% 13% 10% 4	2600
	11th to 20th	Day	67% 6% 11% 13% 3	2986
	21st to end	Day	73% 5% 9% 8% 4	3908
January	1st to 10th	Night	64% 4 12% 14% 6%	4513
	11th to 20th	Night	78% 3 8% 8% 3	4240
	21st to end	Night	71% 4 9% 11% 3	4532
February	1st to 10th	Night	61% 5% 11% 16% 6% 1	2470
	11th to 20th	Night	58% 5% 11% 19% 8%	2306
	21st to end	Night	57% 4 11% 19% 8% 1	1884
March	1st to 10th	Night	51% 4 14% 23% 8%	3586
	11th to 20th	Night	39% 6% 17% 21% 16% 2	3480
	21st to end	Night	48% 5% 11% 24% 11% 1	3817
April	1st to 10th	Night	49% 4 11% 20% 13% 2	2047
	11th to 20th	Night	46% 5% 11% 20% 16% 2	1689
	21st to end	Night	45% 4 10% 21% 16% 4	1710
May	1st to 10th	Night	50% 6% 9% 19% 13% 3	2840
	11th to 20th	Night	46% 8% 10% 24% 11% 2	2813
	21st to end	Night	32% 7% 12% 24% 19% 6%	3087
June	1st to 10th	Night	37% 6% 11% 26% 17% 3	1504
	11th to 20th	Night	37% 6% 14% 24% 16% 3	1330
	21st to end	Night	34% 7% 11% 26% 21% 1	1407
July	1st to 10th	Night	29% 6% 13% 29% 18% 6%	2490
	11th to 20th	Night	29% 6% 14% 30% 19% 2	2594
	21st to end	Night	29% 8% 18% 21% 22% 2	2988
August	1st to 10th	Night	37% 6% 12% 27% 14% 2	2814
	11th to 20th	Night	34% 7% 9% 34% 14% 2	2812
	21st to end	Night	32% 7% 12% 30% 16% 1	3124
September	1st to 10th	Night	34% 7% 13% 26% 17% 3	2025
	11th to 20th	Night	32% 5% 11% 29% 21% 2	2090
	21st to end	Night	43% 5% 12% 23% 16% 1	2090
October	1st to 10th	Night	26% 5% 10% 30% 28% 1	3629
	11th to 20th	Night	42% 5% 11% 24% 17% 1	3779
	21st to end	Night	40% 4 11% 29% 14% 1	4272
November	1st to 10th	Night	44% 4 13% 23% 15% 1	2536
	11th to 20th	Night	56% 4 12% 18% 9% 1	2600
	21st to end	Night	60% 4 13% 18% 4	2761
December	1st to 10th	Night	63% 10% 12% 12% 3	4580
	11th to 20th	Night	65% 6% 13% 12% 4	5208
	21st to end	Night	73% 5% 9% 9% 4	7024

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	22% 14% 39% 17% 7% 1	288
	11th to 20th	Day	23% 16% 41% 15% 5% 1	270
	21st to end	Day	29% 11% 31% 24% 5%	297
February	1st to 10th	Day	24% 16% 34% 21% 4 1	270
	11th to 20th	Day	22% 16% 39% 19% 4	270
	21st to end	Day	23% 18% 40% 17% 1	225
March	1st to 10th	Day	24% 15% 34% 22% 5%	351
	11th to 20th	Day	22% 14% 33% 23% 7% 2	460
	21st to end	Day	24% 13% 31% 25% 6%	506
April	1st to 10th	Day	16% 12% 38% 25% 7% 2	460
	11th to 20th	Day	23% 13% 31% 20% 9% 5%	452
	21st to end	Day	20% 12% 35% 20% 10% 3	460
May	1st to 10th	Day	23% 10% 30% 23% 12% 3	463
	11th to 20th	Day	17% 7% 29% 27% 14% 6%	487
	21st to end	Day	12% 6% 22% 32% 21% 7%	529
June	1st to 10th	Day	12% 6% 30% 34% 15% 4	538
	11th to 20th	Day	10% 6% 28% 36% 17% 2	680
	21st to end	Day	11% 5% 30% 34% 16% 5%	680
July	1st to 10th	Day	10% 3 21% 30% 25% 10%	671
	11th to 20th	Day	11% 4 22% 33% 21% 10%	602
	21st to end	Day	10% 4 18% 31% 29% 9%	532
August	1st to 10th	Day	9% 3 17% 29% 26% 15%	486
	11th to 20th	Day	10% 4 15% 31% 29% 11%	479
	21st to end	Day	9% 3 18% 28% 28% 14%	539
September	1st to 10th	Day	10% 4 22% 29% 23% 12%	490
	11th to 20th	Day	7% 3 16% 28% 33% 13%	490
	21st to end	Day	20% 6% 22% 25% 18% 8%	490
October	1st to 10th	Day	12% 8% 24% 28% 20% 8%	490
	11th to 20th	Day	17% 11% 33% 26% 10% 3	490
	21st to end	Day	24% 15% 35% 19% 6% 1	446
November	1st to 10th	Day	14% 15% 34% 23% 12% 2	300
	11th to 20th	Day	17% 21% 32% 22% 6% 2	300
	21st to end	Day	21% 13% 41% 22% 2	217
December	1st to 10th	Day	22% 16% 37% 19% 6% 1	200
	11th to 20th	Day	25% 16% 37% 19% 5%	200
	21st to end	Day	23% 18% 39% 17% 4	290
January	1st to 10th	Night	23% 11% 39% 19% 6% 1	981
	11th to 20th	Night	28% 12% 34% 21% 4	828
	21st to end	Night	22% 10% 36% 26% 6%	836
February	1st to 10th	Night	26% 9% 36% 26% 3	760
	11th to 20th	Night	22% 11% 34% 27% 6%	743
	21st to end	Night	25% 11% 40% 21% 2	628
March	1st to 10th	Night	21% 9% 36% 27% 7%	760
	11th to 20th	Night	17% 10% 39% 27% 6% 1	760
	21st to end	Night	22% 9% 32% 27% 10% 1	836
April	1st to 10th	Night	19% 10% 35% 30% 5%	717
	11th to 20th	Night	20% 8% 36% 28% 7% 1	563
	21st to end	Night	19% 6% 34% 30% 11%	570
May	1st to 10th	Night	19% 4 30% 34% 10% 2	570
	11th to 20th	Night	20% 4 24% 35% 16% 1	561
	21st to end	Night	11% 3 22% 35% 26% 3	617
June	1st to 10th	Night	13% 3 27% 39% 17% 1	418
	11th to 20th	Night	11% 3 21% 44% 21%	380
	21st to end	Night	10% 6% 20% 46% 16% 2	457
July	1st to 10th	Night	9% 3 13% 40% 31% 5%	555
	11th to 20th	Night	9% 2 16% 40% 27% 5%	552
	21st to end	Night	6% 2 14% 45% 29% 3	624
August	1st to 10th	Night	10% 1 13% 42% 28% 7%	567
	11th to 20th	Night	8% 1 14% 38% 33% 5%	564
	21st to end	Night	10% 2 12% 39% 31% 5%	627
September	1st to 10th	Night	11% 4 15% 34% 30% 6%	724
	11th to 20th	Night	10% 4 16% 32% 31% 7%	760
	21st to end	Night	17% 6% 19% 31% 21% 5%	760
October	1st to 10th	Night	15% 4 25% 30% 21% 4	760
	11th to 20th	Night	19% 11% 30% 25% 13% 2	760
	21st to end	Night	22% 13% 30% 29% 6%	836
November	1st to 10th	Night	18% 10% 29% 29% 12% 2	780
	11th to 20th	Night	22% 13% 34% 21% 8% 1	800
	21st to end	Night	27% 12% 33% 21% 8%	800
December	1st to 10th	Night	24% 14% 34% 20% 7% 1	800
	11th to 20th	Night	24% 12% 38% 22% 4	800
	21st to end	Night	28% 11% 33% 25% 3	1040

Page generated at 2025-01-04 03:23:59. Version ac07

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