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 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% 7% 2 6% 4 4 4 4 5% 7% 43%	104563
	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	104480
Transparency	Day	21% 46% 5% 14% 11% 3	108265
	Night	20% 44% 5% 14% 12% 4	108919
Seeing	Day	15% 9% 22% 25% 21% 10%	15493
	Night	15% 8% 25% 31% 18% 3	25332

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	14% 15% 3 7% 3 3 2 2 3 4 43%	2653
	11th to 20th	Day	20% 8% 2 7% 4 4 3 3 3 4 43%	2850
	21st to end	Day	21% 10% 2 6% 4 4 3 2 4 5% 39%	3135
February	1st to 10th	Day	20% 9% 4 7% 4 4 3 2 4 5% 39%	1875
	11th to 20th	Day	20% 9% 3 5% 4 3 3 3 5% 5% 39%	1848
	21st to end	Day	22% 10% 3 7% 4 3 3 3 4 5% 36%	1570
March	1st to 10th	Day	19% 12% 3 9% 4 4 4 3 4 5% 33%	3120
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 4 6% 43%	3470
	21st to end	Day	13% 6% 3 8% 5% 5% 5% 3 4 6% 41%	4068
April	1st to 10th	Day	12% 7% 2 6% 4 4 5% 4 5% 5% 45%	2280
	11th to 20th	Day	16% 7% 2 6% 4 4 3 3 5% 6% 44%	2254
	21st to end	Day	13% 5% 2 7% 5% 4 4 4 6% 6% 43%	2280
May	1st to 10th	Day	14% 6% 2 6% 5% 4 5% 4 6% 8% 39%	3765
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 6% 9% 39%	4017
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 5% 7% 9% 36%	4634
June	1st to 10th	Day	8% 5% 2 7% 5% 5% 5% 4 7% 10% 42%	2660
	11th to 20th	Day	4 4 2 5% 4 5% 5% 5% 7% 10% 48%	2660
	21st to end	Day	4 4 1 5% 5% 5% 6% 5% 8% 10% 47%	2660
July	1st to 10th	Day	6% 5% 2 7% 5% 5% 7% 5% 8% 10% 40%	4440
	11th to 20th	Day	8% 5% 2 7% 5% 5% 5% 5% 8% 12% 39%	4294
	21st to end	Day	15% 8% 3 8% 6% 6% 6% 5% 5% 8% 30%	4443
August	1st to 10th	Day	4 3 2 4 3 4 4 3 6% 10% 58%	3785
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 8% 9% 48%	3729
	21st to end	Day	6% 4 2 5% 4 4 5% 4 6% 8% 53%	4180
September	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 6% 8% 44%	2280
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 5% 8% 45%	2209
	21st to end	Day	10% 6% 2 5% 4 3 3 3 3 7% 53%	2090
October	1st to 10th	Day	7% 4 2 4 4 3 4 3 5% 5% 59%	1999
	11th to 20th	Day	11% 5% 1 4 3 3 3 4 5% 5% 57%	1900
	21st to end	Day	18% 6% 1 4 3 3 2 3 4 4 53%	2090
November	1st to 10th	Day	13% 6% 2 4 2 3 2 2 4 5% 57%	1793
	11th to 20th	Day	13% 5% 2 4 3 3 3 4 5% 6% 53%	1800
	21st to end	Day	19% 7% 2 5% 3 3 4 3 4 6% 44%	1800
December	1st to 10th	Day	17% 9% 2 6% 3 3 3 3 4 5% 45%	2930
	11th to 20th	Day	20% 9% 3 7% 4 3 3 2 4 4 42%	3020
	21st to end	Day	14% 10% 3 8% 4 5% 4 4 5% 5% 36%	3982
January	1st to 10th	Night	19% 9% 3 5% 3 3 3 2 4 4 44%	4417
	11th to 20th	Night	18% 9% 2 6% 3 3 3 2 3 5% 45%	4120
	21st to end	Night	24% 9% 2 4 3 3 2 2 4 5% 44%	4532
February	1st to 10th	Night	20% 9% 3 7% 4 3 3 2 4 5% 41%	2302
	11th to 20th	Night	19% 9% 3 6% 5% 3 3 2 3 5% 43%	2218
	21st to end	Night	20% 8% 2 6% 4 4 3 3 3 6% 40%	1884
March	1st to 10th	Night	20% 10% 2 6% 4 4 3 3 4 6% 39%	3733
	11th to 20th	Night	15% 6% 2 5% 4 3 3 3 4 6% 49%	3517
	21st to end	Night	13% 6% 2 6% 5% 4 4 3 6% 7% 43%	3562
April	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 5% 8% 48%	1900
	11th to 20th	Night	15% 6% 2 4 3 3 3 4 5% 7% 50%	1875
	21st to end	Night	11% 6% 2 5% 4 4 4 3 5% 6% 49%	1900
May	1st to 10th	Night	19% 7% 2 6% 4 3 3 3 5% 7% 41%	3130
	11th to 20th	Night	12% 7% 3 6% 4 4 3 3 5% 6% 47%	2858
	21st to end	Night	10% 6% 2 5% 5% 4 5% 5% 7% 9% 40%	2908
June	1st to 10th	Night	8% 4 2 6% 5% 5% 4 4 6% 11% 46%	1520
	11th to 20th	Night	3 2 1 4 3 3 4 4 7% 10% 60%	1520
	21st to end	Night	3 3 1 3 4 4 4 5% 7% 12% 55%	1520
July	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 4 7% 11% 48%	2530
	11th to 20th	Night	6% 4 2 5% 3 3 4 4 6% 13% 50%	2658
	21st to end	Night	11% 8% 3 8% 5% 4 4 4 6% 8% 39%	3118
August	1st to 10th	Night	2 2 1 2 2 3 3 3 6% 7% 69%	3144
	11th to 20th	Night	4 3 2 5% 3 3 4 5% 7% 10% 55%	3100
	21st to end	Night	4 3 1 5% 3 4 4 4 7% 9% 57%	3476
September	1st to 10th	Night	7% 5% 1 6% 4 4 5% 4 5% 6% 53%	1900
	11th to 20th	Night	11% 6% 2 5% 3 4 3 3 5% 8% 51%	1952
	21st to end	Night	9% 5% 1 4 4 3 3 3 4 6% 57%	2090
October	1st to 10th	Night	7% 3 1 4 3 3 2 3 5% 7% 62%	2176
	11th to 20th	Night	11% 5% 1 4 3 2 3 2 4 6% 59%	2280
	21st to end	Night	17% 6% 3 4 3 2 3 3 4 4 53%	2508
November	1st to 10th	Night	11% 4 2 4 4 3 3 3 5% 6% 56%	2503
	11th to 20th	Night	11% 5% 1 4 4 3 4 4 5% 7% 53%	2600
	21st to end	Night	14% 5% 2 5% 4 3 4 3 4 6% 50%	2600
December	1st to 10th	Night	18% 8% 2 5% 3 3 2 2 4 5% 48%	4250
	11th to 20th	Night	19% 8% 3 6% 4 3 3 3 4 5% 44%	5183
	21st to end	Night	17% 8% 3 6% 4 5% 5% 4 5% 5% 38%	6996

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	32% 36% 2 13% 15% 1	2654
	11th to 20th	Day	30% 38% 4 13% 14% 1	2850
	21st to end	Day	31% 40% 4 11% 12% 2	3135
February	1st to 10th	Day	19% 64% 2 9% 5% 1	1875
	11th to 20th	Day	18% 64% 3 9% 5% 1	1858
	21st to end	Day	18% 64% 2 6% 6% 3	1570
March	1st to 10th	Day	37% 41% 3 5% 7% 7%	3120
	11th to 20th	Day	20% 41% 6% 17% 13% 3	3470
	21st to end	Day	25% 41% 4 13% 15% 1	4068
April	1st to 10th	Day	15% 65% 3 9% 7% 1	2280
	11th to 20th	Day	18% 66% 3 7% 5% 2	2254
	21st to end	Day	14% 65% 4 10% 6% 1	2280
May	1st to 10th	Day	23% 43% 7% 18% 9%	3800
	11th to 20th	Day	25% 42% 11% 15% 7%	4021
	21st to end	Day	27% 43% 7% 16% 6% 1	4647
June	1st to 10th	Day	15% 66% 5% 7% 7% 1	2660
	11th to 20th	Day	13% 65% 6% 9% 7%	2660
	21st to end	Day	13% 65% 6% 12% 4	2660
July	1st to 10th	Day	22% 40% 11% 21% 6%	4371
	11th to 20th	Day	23% 38% 9% 25% 4	4219
	21st to end	Day	38% 37% 6% 14% 4	4303
August	1st to 10th	Day	10% 38% 11% 21% 19% 2	3773
	11th to 20th	Day	18% 40% 12% 18% 12% 1	3765
	21st to end	Day	16% 38% 7% 18% 20% 1	4179
September	1st to 10th	Day	12% 61% 4 14% 7% 1	2280
	11th to 20th	Day	13% 60% 6% 9% 10% 2	2209
	21st to end	Day	16% 60% 4 12% 7% 2	2090
October	1st to 10th	Day	8% 36% 4 7% 24% 21%	3324
	11th to 20th	Day	7% 36% 2 14% 28% 13%	3140
	21st to end	Day	14% 36% 1 18% 22% 7%	3428
November	1st to 10th	Day	20% 56% 3 8% 11% 3	1793
	11th to 20th	Day	14% 58% 3 9% 13% 4	1800
	21st to end	Day	20% 57% 2 9% 11% 1	1800
December	1st to 10th	Day	27% 35% 2 19% 16% 2	2930
	11th to 20th	Day	33% 31% 2 16% 14% 3	3017
	21st to end	Day	36% 29% 6% 19% 9% 1	3982
January	1st to 10th	Night	31% 36% 3 12% 17% 1	4417
	11th to 20th	Night	26% 38% 4 13% 14% 4	4120
	21st to end	Night	28% 40% 4 15% 12% 2	4532
February	1st to 10th	Night	18% 65% 2 7% 7% 1	2302
	11th to 20th	Night	18% 63% 3 8% 6% 1	2219
	21st to end	Night	17% 64% 2 6% 6% 4	1884
March	1st to 10th	Night	33% 42% 5% 6% 8% 6%	3733
	11th to 20th	Night	19% 41% 4 16% 14% 6%	3517
	21st to end	Night	22% 43% 6% 11% 18% 1	3562
April	1st to 10th	Night	14% 65% 4 9% 8% 1	1900
	11th to 20th	Night	16% 65% 3 9% 6% 1	1875
	21st to end	Night	12% 65% 4 9% 8% 2	1900
May	1st to 10th	Night	28% 42% 6% 15% 9% 1	3160
	11th to 20th	Night	23% 43% 9% 20% 6%	2859
	21st to end	Night	25% 44% 7% 15% 7% 1	2916
June	1st to 10th	Night	13% 65% 5% 6% 9% 1	1520
	11th to 20th	Night	8% 65% 8% 10% 9% 1	1520
	21st to end	Night	9% 64% 7% 13% 6%	1520
July	1st to 10th	Night	20% 39% 16% 18% 7%	2490
	11th to 20th	Night	15% 38% 9% 30% 7% 1	2610
	21st to end	Night	35% 37% 7% 14% 7%	3019
August	1st to 10th	Night	7% 37% 6% 29% 19% 2	3132
	11th to 20th	Night	12% 40% 17% 18% 12% 1	3130
	21st to end	Night	11% 38% 9% 18% 22% 2	3476
September	1st to 10th	Night	9% 60% 5% 13% 9% 3	1900
	11th to 20th	Night	11% 61% 5% 10% 11% 2	1952
	21st to end	Night	10% 60% 5% 15% 8% 2	2090
October	1st to 10th	Night	7% 37% 3 8% 23% 22%	3631
	11th to 20th	Night	7% 36% 2 10% 25% 20%	3779
	21st to end	Night	13% 37% 3 21% 14% 12%	4120
November	1st to 10th	Night	18% 56% 3 8% 12% 2	2503
	11th to 20th	Night	14% 57% 2 10% 13% 5%	2600
	21st to end	Night	15% 56% 3 12% 12% 2	2600
December	1st to 10th	Night	26% 36% 4 19% 14% 1	4250
	11th to 20th	Night	31% 31% 3 16% 16% 2	5185
	21st to end	Night	34% 28% 8% 18% 10% 2	6996

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	25% 19% 35% 14% 6% 1	288
	11th to 20th	Day	26% 19% 36% 14% 4 1	270
	21st to end	Day	21% 22% 36% 18% 2	297
February	1st to 10th	Day	26% 17% 37% 14% 6% 1	270
	11th to 20th	Day	33% 18% 33% 13% 3 1	270
	21st to end	Day	36% 21% 30% 8% 4	225
March	1st to 10th	Day	21% 19% 35% 18% 5% 1	270
	11th to 20th	Day	21% 22% 33% 22% 1	270
	21st to end	Day	20% 18% 33% 21% 7% 1	448
April	1st to 10th	Day	17% 18% 31% 24% 8% 1	460
	11th to 20th	Day	20% 14% 33% 22% 8% 3	452
	21st to end	Day	19% 11% 31% 22% 13% 3	460
May	1st to 10th	Day	18% 11% 26% 28% 13% 3	463
	11th to 20th	Day	14% 6% 23% 25% 22% 10%	487
	21st to end	Day	10% 5% 21% 29% 23% 12%	622
June	1st to 10th	Day	10% 4 16% 27% 27% 17%	680
	11th to 20th	Day	5% 2 15% 33% 32% 14%	680
	21st to end	Day	5% 3 16% 30% 32% 13%	680
July	1st to 10th	Day	7% 1 10% 29% 33% 20%	671
	11th to 20th	Day	7% 2 10% 25% 36% 21%	668
	21st to end	Day	8% 2 10% 27% 35% 19%	729
August	1st to 10th	Day	7% 3 8% 30% 33% 19%	486
	11th to 20th	Day	12% 1 9% 31% 34% 13%	479
	21st to end	Day	12% 1 6% 21% 34% 26%	539
September	1st to 10th	Day	10% 2 10% 28% 35% 16%	490
	11th to 20th	Day	12% 2 13% 21% 34% 18%	490
	21st to end	Day	15% 4 14% 32% 21% 13%	490
October	1st to 10th	Day	9% 3 18% 32% 32% 8%	399
	11th to 20th	Day	10% 8% 35% 28% 14% 5%	300
	21st to end	Day	23% 10% 26% 30% 8% 2	330
November	1st to 10th	Day	19% 11% 22% 33% 11% 4	300
	11th to 20th	Day	10% 16% 36% 27% 10% 1	300
	21st to end	Day	24% 13% 31% 17% 12% 3	300
December	1st to 10th	Day	23% 19% 32% 18% 7% 2	300
	11th to 20th	Day	24% 17% 32% 17% 9% 1	300
	21st to end	Day	24% 19% 35% 16% 5% 1	330
January	1st to 10th	Night	24% 13% 34% 25% 5%	981
	11th to 20th	Night	24% 15% 33% 23% 4	950
	21st to end	Night	22% 11% 39% 26% 2	1045
February	1st to 10th	Night	24% 13% 35% 24% 4	782
	11th to 20th	Night	23% 17% 33% 24% 3	743
	21st to end	Night	25% 16% 34% 22% 2	628
March	1st to 10th	Night	21% 13% 31% 30% 5%	760
	11th to 20th	Night	23% 10% 35% 27% 4 1	594
	21st to end	Night	18% 12% 33% 27% 11%	627
April	1st to 10th	Night	15% 11% 37% 28% 8% 1	570
	11th to 20th	Night	18% 9% 31% 30% 11% 1	563
	21st to end	Night	14% 8% 33% 33% 11% 1	570
May	1st to 10th	Night	14% 8% 26% 35% 14% 2	570
	11th to 20th	Night	12% 5% 23% 37% 19% 4	561
	21st to end	Night	8% 3 17% 41% 26% 6%	617
June	1st to 10th	Night	9% 1 15% 37% 32% 6%	570
	11th to 20th	Night	3 1 12% 36% 46% 3	570
	21st to end	Night	4 1 11% 39% 39% 6%	570
July	1st to 10th	Night	3 1 10% 32% 44% 10%	555
	11th to 20th	Night	6% 1 8% 29% 42% 13%	552
	21st to end	Night	6% 1 8% 30% 43% 11%	624
August	1st to 10th	Night	5% 4 33% 49% 9%	567
	11th to 20th	Night	7% 1 7% 37% 41% 7%	564
	21st to end	Night	7% 1 10% 27% 47% 9%	627
September	1st to 10th	Night	8% 2 8% 38% 40% 5%	570
	11th to 20th	Night	12% 3 11% 30% 36% 8%	622
	21st to end	Night	10% 4 15% 35% 31% 4	760
October	1st to 10th	Night	8% 3 18% 35% 30% 4	760
	11th to 20th	Night	14% 5% 24% 38% 17% 2	760
	21st to end	Night	20% 6% 24% 33% 16% 1	836
November	1st to 10th	Night	13% 6% 25% 36% 17% 2	780
	11th to 20th	Night	12% 9% 35% 33% 11% 1	800
	21st to end	Night	17% 10% 32% 30% 10% 1	800
December	1st to 10th	Night	23% 11% 32% 29% 6%	800
	11th to 20th	Night	22% 10% 32% 29% 6%	984
	21st to end	Night	25% 13% 31% 27% 5%	1100

Page generated at 2025-01-04 02:24:01. Version ac07

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