Collierville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Collierville 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	12% 7% 2 6% 4 4 4 4 5% 7% 43%	131262
	Night	13% 6% 2 6% 4 3 4 3 5% 7% 47%	131386
Transparency	Day	25% 38% 7% 16% 12% 3	134925
	Night	24% 36% 6% 16% 13% 4	135801
Seeing	Day	15% 9% 22% 25% 20% 9%	17233
	Night	15% 8% 25% 31% 18% 3	27088

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	15% 12% 4 9% 3 3 3 2 3 5% 41%	4853
	11th to 20th	Day	14% 6% 2 7% 3 3 3 2 3 4 53%	5310
	21st to end	Day	19% 8% 3 7% 5% 3 3 2 3 4 43%	5812
February	1st to 10th	Day	20% 9% 4 7% 4 4 3 2 4 5% 39%	2073
	11th to 20th	Day	21% 9% 4 6% 4 3 3 3 5% 5% 39%	2048
	21st to end	Day	20% 9% 3 7% 4 3 3 3 4 5% 38%	1730
March	1st to 10th	Day	18% 12% 3 9% 5% 4 4 3 4 5% 34%	4580
	11th to 20th	Day	13% 7% 2 6% 4 4 3 3 4 6% 47%	5079
	21st to end	Day	12% 7% 3 8% 5% 5% 5% 3 4 7% 43%	5957
April	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 5% 45%	2520
	11th to 20th	Day	15% 6% 2 6% 4 4 3 3 5% 6% 46%	2494
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 6% 6% 41%	2520
May	1st to 10th	Day	17% 7% 2 7% 5% 5% 5% 5% 6% 8% 33%	5417
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 4 7% 9% 32%	5769
	21st to end	Day	17% 7% 2 7% 5% 4 5% 4 7% 8% 34%	6661
June	1st to 10th	Day	8% 5% 2 7% 5% 5% 5% 4 7% 10% 42%	2800
	11th to 20th	Day	5% 4 2 6% 5% 6% 6% 5% 7% 10% 46%	2800
	21st to end	Day	4 4 1 5% 5% 5% 6% 5% 8% 10% 46%	2800
July	1st to 10th	Day	6% 5% 2 7% 5% 6% 7% 5% 8% 10% 40%	6360
	11th to 20th	Day	6% 4 2 6% 5% 6% 6% 5% 8% 13% 39%	6144
	21st to end	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 12% 35%	6386
August	1st to 10th	Day	4 3 2 4 3 4 4 3 6% 10% 58%	3905
	11th to 20th	Day	6% 4 2 5% 4 4 5% 5% 8% 9% 48%	3849
	21st to end	Day	6% 4 2 5% 4 4 5% 4 6% 8% 53%	4312
September	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 5% 6% 8% 44%	2400
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 6% 8% 45%	2325
	21st to end	Day	10% 6% 2 5% 4 4 4 3 3 7% 53%	2200
October	1st to 10th	Day	7% 4 2 4 3 3 4 3 5% 5% 59%	2104
	11th to 20th	Day	11% 4 1 4 3 3 3 4 4 5% 58%	2000
	21st to end	Day	19% 6% 2 4 3 3 2 3 4 4 52%	2200
November	1st to 10th	Day	13% 6% 2 4 2 2 2 2 4 5% 57%	1884
	11th to 20th	Day	13% 5% 2 4 3 3 3 4 5% 6% 53%	1890
	21st to end	Day	19% 7% 2 5% 3 3 4 3 4 6% 44%	1890
December	1st to 10th	Day	17% 9% 2 7% 3 3 3 2 4 5% 45%	3020
	11th to 20th	Day	19% 9% 3 7% 4 3 3 2 4 4 42%	3100
	21st to end	Day	14% 10% 3 8% 4 5% 5% 4 5% 5% 36%	4070
January	1st to 10th	Night	18% 8% 3 7% 4 3 3 3 4 5% 43%	8052
	11th to 20th	Night	13% 7% 3 5% 3 3 3 2 3 4 54%	7680
	21st to end	Night	21% 8% 3 6% 4 3 3 2 4 5% 40%	8402
February	1st to 10th	Night	20% 8% 3 7% 4 3 3 2 4 5% 42%	2544
	11th to 20th	Night	20% 8% 3 6% 4 3 3 2 3 5% 41%	2458
	21st to end	Night	19% 8% 2 7% 4 4 3 3 3 5% 42%	2076
March	1st to 10th	Night	18% 9% 2 6% 4 4 3 3 4 5% 40%	5493
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 4 6% 51%	5142
	21st to end	Night	13% 6% 2 6% 5% 4 4 3 5% 7% 46%	5213
April	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 6% 7% 47%	2100
	11th to 20th	Night	14% 6% 2 4 3 3 3 4 5% 7% 51%	2075
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 6% 49%	2100
May	1st to 10th	Night	19% 9% 2 7% 4 3 4 3 5% 7% 37%	4500
	11th to 20th	Night	16% 9% 3 8% 4 4 4 3 5% 5% 38%	4106
	21st to end	Night	14% 8% 3 6% 5% 4 5% 4 6% 8% 37%	4185
June	1st to 10th	Night	8% 4 2 6% 5% 5% 4 4 6% 10% 47%	1600
	11th to 20th	Night	3 2 1 4 3 3 4 4 7% 10% 59%	1600
	21st to end	Night	3 3 1 3 4 4 4 5% 7% 12% 55%	1600
July	1st to 10th	Night	5% 4 2 5% 5% 5% 5% 4 7% 11% 47%	3618
	11th to 20th	Night	5% 3 1 4 3 4 5% 4 7% 14% 50%	3801
	21st to end	Night	8% 6% 2 7% 5% 4 5% 5% 7% 12% 40%	4482
August	1st to 10th	Night	2 2 1 2 2 3 4 3 5% 7% 69%	3244
	11th to 20th	Night	4 3 2 5% 3 3 5% 5% 7% 10% 55%	3200
	21st to end	Night	4 3 1 5% 3 4 4 4 7% 9% 57%	3586
September	1st to 10th	Night	7% 5% 1 6% 4 4 5% 4 5% 7% 52%	2000
	11th to 20th	Night	10% 6% 2 4 3 4 3 4 5% 8% 51%	2055
	21st to end	Night	9% 5% 1 5% 4 3 3 3 4 6% 57%	2200
October	1st to 10th	Night	7% 3 1 4 3 3 2 3 5% 7% 62%	2291
	11th to 20th	Night	11% 5% 1 4 3 2 3 2 4 6% 60%	2400
	21st to end	Night	17% 6% 2 4 3 2 3 3 3 4 52%	2640
November	1st to 10th	Night	11% 4 2 4 3 3 3 3 5% 5% 56%	2631
	11th to 20th	Night	10% 4 1 4 4 3 3 4 5% 6% 54%	2730
	21st to end	Night	14% 6% 2 5% 4 3 4 3 4 6% 49%	2730
December	1st to 10th	Night	18% 8% 2 5% 3 3 3 3 4 5% 48%	4380
	11th to 20th	Night	19% 7% 3 6% 4 3 3 3 4 5% 44%	5322
	21st to end	Night	17% 8% 3 6% 4 5% 5% 4 5% 5% 38%	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	41% 20% 6% 21% 10% 1	4854
	11th to 20th	Day	28% 21% 3 18% 26% 4	5310
	21st to end	Day	37% 23% 4 14% 17% 6%	5812
February	1st to 10th	Day	22% 58% 2 11% 5% 1	2073
	11th to 20th	Day	21% 58% 3 11% 6% 1	2058
	21st to end	Day	18% 58% 3 8% 9% 4	1730
March	1st to 10th	Day	42% 29% 3 11% 7% 7%	4580
	11th to 20th	Day	24% 29% 5% 15% 18% 8%	5079
	21st to end	Day	30% 29% 5% 18% 17% 1	5959
April	1st to 10th	Day	17% 59% 4 11% 8% 1	2520
	11th to 20th	Day	19% 60% 4 10% 6% 2	2494
	21st to end	Day	19% 59% 4 11% 6% 1	2520
May	1st to 10th	Day	34% 33% 9% 17% 7%	5452
	11th to 20th	Day	35% 33% 13% 13% 5%	5773
	21st to end	Day	35% 32% 7% 15% 9% 2	6675
June	1st to 10th	Day	15% 64% 5% 7% 8% 1	2800
	11th to 20th	Day	15% 63% 6% 9% 7%	2800
	21st to end	Day	14% 62% 7% 12% 5%	2800
July	1st to 10th	Day	26% 31% 12% 22% 10%	6291
	11th to 20th	Day	24% 31% 16% 26% 3	6069
	21st to end	Day	31% 29% 15% 21% 3	6204
August	1st to 10th	Day	10% 37% 11% 22% 18% 2	3893
	11th to 20th	Day	18% 39% 12% 19% 12% 1	3885
	21st to end	Day	17% 37% 7% 18% 20% 1	4311
September	1st to 10th	Day	13% 59% 4 15% 8% 1	2400
	11th to 20th	Day	13% 57% 6% 12% 10% 2	2325
	21st to end	Day	17% 57% 4 11% 8% 2	2200
October	1st to 10th	Day	8% 35% 3 7% 25% 21%	3429
	11th to 20th	Day	7% 35% 2 15% 28% 13%	3240
	21st to end	Day	16% 35% 2 18% 22% 7%	3538
November	1st to 10th	Day	20% 53% 3 8% 12% 3	1884
	11th to 20th	Day	14% 55% 4 11% 12% 4	1890
	21st to end	Day	21% 54% 3 10% 12% 1	1890
December	1st to 10th	Day	28% 34% 2 19% 15% 2	3020
	11th to 20th	Day	33% 30% 3 16% 14% 4	3097
	21st to end	Day	36% 29% 6% 19% 9% 1	4070
January	1st to 10th	Night	38% 21% 8% 20% 12% 2	8053
	11th to 20th	Night	26% 22% 4 15% 28% 6%	7680
	21st to end	Night	39% 23% 4 16% 14% 4	8402
February	1st to 10th	Night	20% 59% 3 9% 9% 1	2544
	11th to 20th	Night	22% 57% 3 10% 7% 1	2459
	21st to end	Night	19% 58% 3 7% 9% 5%	2076
March	1st to 10th	Night	37% 30% 5% 10% 13% 6%	5493
	11th to 20th	Night	23% 29% 4 17% 14% 14%	5142
	21st to end	Night	27% 30% 6% 17% 18% 3	5213
April	1st to 10th	Night	17% 59% 5% 10% 9% 1	2100
	11th to 20th	Night	17% 59% 4 11% 7% 1	2075
	21st to end	Night	15% 59% 5% 9% 9% 2	2100
May	1st to 10th	Night	36% 31% 9% 15% 8%	4530
	11th to 20th	Night	38% 31% 9% 18% 4	4107
	21st to end	Night	35% 32% 6% 15% 9% 2	4193
June	1st to 10th	Night	14% 62% 6% 8% 10% 1	1600
	11th to 20th	Night	10% 62% 8% 10% 9% 1	1600
	21st to end	Night	10% 62% 8% 14% 7%	1600
July	1st to 10th	Night	23% 30% 15% 20% 11% 1	3580
	11th to 20th	Night	17% 29% 18% 31% 5% 1	3756
	21st to end	Night	29% 29% 15% 21% 5%	4353
August	1st to 10th	Night	7% 36% 6% 30% 19% 2	3232
	11th to 20th	Night	12% 39% 18% 19% 12% 1	3230
	21st to end	Night	12% 37% 9% 18% 22% 2	3586
September	1st to 10th	Night	10% 58% 5% 14% 10% 3	2000
	11th to 20th	Night	11% 58% 5% 12% 11% 2	2055
	21st to end	Night	12% 57% 5% 14% 9% 2	2200
October	1st to 10th	Night	7% 36% 3 9% 23% 22%	3746
	11th to 20th	Night	7% 35% 2 10% 26% 20%	3899
	21st to end	Night	14% 36% 3 20% 15% 12%	4252
November	1st to 10th	Night	18% 54% 4 9% 13% 2	2631
	11th to 20th	Night	14% 55% 3 11% 13% 4	2730
	21st to end	Night	17% 54% 3 12% 12% 2	2730
December	1st to 10th	Night	27% 35% 4 19% 14% 1	4380
	11th to 20th	Night	31% 31% 4 16% 16% 2	5324
	21st to end	Night	34% 28% 8% 18% 10% 2	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	24% 19% 35% 15% 6% 1	330
	11th to 20th	Day	23% 21% 37% 14% 4 1	330
	21st to end	Day	21% 23% 37% 16% 2	363
February	1st to 10th	Day	26% 17% 37% 14% 5% 1	330
	11th to 20th	Day	33% 20% 32% 12% 2 1	330
	21st to end	Day	32% 21% 33% 9% 5%	273
March	1st to 10th	Day	22% 19% 37% 16% 4 1	330
	11th to 20th	Day	22% 22% 36% 19% 1	330
	21st to end	Day	19% 19% 34% 22% 6% 1	530
April	1st to 10th	Day	18% 19% 30% 24% 8% 1	540
	11th to 20th	Day	19% 15% 34% 22% 8% 2	532
	21st to end	Day	19% 11% 31% 23% 13% 3	540
May	1st to 10th	Day	19% 12% 27% 27% 12% 3	507
	11th to 20th	Day	15% 8% 24% 24% 21% 9%	527
	21st to end	Day	12% 6% 21% 29% 22% 11%	671
June	1st to 10th	Day	9% 5% 16% 28% 25% 16%	730
	11th to 20th	Day	5% 2 16% 33% 31% 13%	730
	21st to end	Day	5% 2 15% 30% 33% 14%	730
July	1st to 10th	Day	7% 2 9% 29% 34% 20%	721
	11th to 20th	Day	7% 2 10% 25% 36% 20%	718
	21st to end	Day	7% 2 9% 27% 37% 19%	783
August	1st to 10th	Day	6% 3 8% 30% 34% 19%	526
	11th to 20th	Day	11% 1 8% 30% 34% 15%	519
	21st to end	Day	11% 2 7% 23% 33% 24%	583
September	1st to 10th	Day	10% 2 11% 28% 35% 15%	530
	11th to 20th	Day	11% 2 12% 22% 35% 18%	530
	21st to end	Day	15% 4 14% 33% 21% 12%	530
October	1st to 10th	Day	9% 3 18% 32% 31% 7%	434
	11th to 20th	Day	9% 8% 34% 28% 16% 5%	330
	21st to end	Day	24% 10% 28% 28% 8% 2	363
November	1st to 10th	Day	18% 11% 24% 32% 11% 3	330
	11th to 20th	Day	9% 16% 37% 28% 9% 1	330
	21st to end	Day	23% 15% 30% 18% 12% 3	330
December	1st to 10th	Day	23% 19% 32% 17% 6% 2	330
	11th to 20th	Day	23% 18% 33% 17% 8% 1	330
	21st to end	Day	23% 19% 36% 16% 5% 1	363
January	1st to 10th	Night	24% 13% 34% 25% 4	1050
	11th to 20th	Night	23% 15% 35% 23% 4	1050
	21st to end	Night	22% 12% 40% 25% 2	1155
February	1st to 10th	Night	24% 13% 36% 25% 3	864
	11th to 20th	Night	25% 17% 33% 23% 2	823
	21st to end	Night	23% 17% 34% 23% 3	692
March	1st to 10th	Night	21% 13% 32% 29% 5%	840
	11th to 20th	Night	23% 10% 36% 27% 4 1	656
	21st to end	Night	17% 12% 34% 27% 10%	693
April	1st to 10th	Night	16% 11% 36% 28% 9%	630
	11th to 20th	Night	16% 9% 33% 30% 10%	623
	21st to end	Night	15% 8% 31% 33% 12% 1	630
May	1st to 10th	Night	15% 9% 26% 35% 13% 2	603
	11th to 20th	Night	13% 6% 23% 37% 18% 4	591
	21st to end	Night	8% 3 18% 40% 25% 5%	650
June	1st to 10th	Night	8% 2 15% 38% 31% 6%	600
	11th to 20th	Night	3 1 13% 36% 45% 3	600
	21st to end	Night	4 1 11% 37% 40% 6%	600
July	1st to 10th	Night	3 1 9% 32% 44% 10%	585
	11th to 20th	Night	6% 1 8% 29% 44% 13%	582
	21st to end	Night	6% 1 8% 30% 45% 11%	657
August	1st to 10th	Night	5% 1 5% 33% 48% 8%	597
	11th to 20th	Night	7% 1 7% 37% 41% 8%	594
	21st to end	Night	7% 1 9% 29% 45% 9%	660
September	1st to 10th	Night	8% 2 9% 38% 39% 5%	600
	11th to 20th	Night	11% 3 11% 30% 37% 8%	655
	21st to end	Night	10% 4 15% 36% 31% 4	800
October	1st to 10th	Night	8% 3 19% 36% 30% 4	800
	11th to 20th	Night	13% 5% 23% 38% 18% 2	800
	21st to end	Night	21% 6% 24% 33% 15% 1	880
November	1st to 10th	Night	13% 7% 25% 37% 17% 2	820
	11th to 20th	Night	12% 8% 36% 33% 11% 1	840
	21st to end	Night	18% 10% 31% 30% 10% 1	840
December	1st to 10th	Night	23% 10% 32% 29% 6%	840
	11th to 20th	Night	22% 11% 32% 29% 6%	1033
	21st to end	Night	25% 13% 30% 27% 5%	1155

Page generated at 2026-04-29 01:21:44. Version ac07

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