Smithville Reservoir
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smithville Reservoir clear sky chart from 2005-11-06 to 2025-07-21.

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	11% 7% 3 6% 4 4 4 3 5% 7% 45%	120112
	Night	11% 7% 3 6% 4 3 4 3 5% 6% 47%	119219
Transparency	Day	39% 3 12% 26% 17% 3	123766
	Night	38% 3 11% 26% 19% 3	123708
Seeing	Day	14% 10% 30% 28% 15% 3	16671
	Night	14% 9% 32% 32% 12% 1	26511

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% 9% 4 11% 4 4 4 3 5% 7% 36%	4077
	11th to 20th	Day	7% 9% 4 9% 6% 7% 6% 3 3 5% 40%	4080
	21st to end	Day	13% 13% 5% 10% 5% 5% 4 3 4 4 35%	4488
February	1st to 10th	Day	13% 11% 4 8% 5% 5% 3 3 6% 6% 35%	1800
	11th to 20th	Day	12% 12% 3 7% 4 3 3 3 5% 6% 40%	1754
	21st to end	Day	11% 9% 3 7% 3 3 4 3 4 7% 45%	1685
March	1st to 10th	Day	15% 8% 2 5% 3 3 3 2 4 4 51%	4936
	11th to 20th	Day	9% 6% 2 5% 4 3 3 3 4 6% 54%	4980
	21st to end	Day	13% 11% 5% 8% 5% 4 4 4 5% 7% 34%	5462
April	1st to 10th	Day	15% 8% 2 7% 3 3 3 3 5% 6% 44%	2322
	11th to 20th	Day	14% 9% 3 6% 4 4 4 3 5% 7% 40%	2374
	21st to end	Day	19% 8% 3 7% 4 4 5% 4 6% 7% 35%	2542
May	1st to 10th	Day	14% 7% 2 6% 4 4 4 3 5% 7% 44%	5862
	11th to 20th	Day	14% 6% 2 5% 4 4 3 3 5% 7% 47%	5862
	21st to end	Day	18% 7% 2 6% 4 4 4 3 5% 6% 42%	6742
June	1st to 10th	Day	7% 4 2 5% 4 5% 5% 4 7% 9% 49%	2800
	11th to 20th	Day	7% 5% 2 5% 5% 4 5% 4 7% 9% 47%	2800
	21st to end	Day	7% 3 2 6% 4 4 5% 4 6% 9% 50%	2800
July	1st to 10th	Day	10% 7% 2 7% 4 4 5% 4 7% 8% 42%	4358
	11th to 20th	Day	6% 4 2 5% 3 4 4 4 6% 9% 54%	4250
	21st to end	Day	6% 4 2 5% 4 4 5% 5% 7% 10% 47%	4466
August	1st to 10th	Day	5% 4 2 5% 4 4 4 4 6% 9% 53%	4104
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 6% 8% 46%	4041
	21st to end	Day	6% 4 2 5% 3 4 5% 4 6% 7% 54%	4262
September	1st to 10th	Day	11% 5% 2 4 3 3 5% 3 5% 7% 53%	2280
	11th to 20th	Day	9% 5% 2 5% 5% 4 4 4 6% 7% 50%	2124
	21st to end	Day	9% 5% 1 5% 3 4 4 3 5% 6% 56%	2067
October	1st to 10th	Day	13% 5% 1 5% 3 3 3 3 4 7% 52%	1900
	11th to 20th	Day	13% 5% 2 5% 3 3 3 2 4 5% 55%	1900
	21st to end	Day	15% 7% 2 5% 4 3 3 3 5% 6% 47%	2090
November	1st to 10th	Day	9% 6% 2 5% 3 4 4 2 4 7% 53%	1953
	11th to 20th	Day	14% 6% 2 4 4 3 3 3 4 6% 51%	1680
	21st to end	Day	16% 9% 3 5% 3 2 4 2 3 6% 46%	1600
December	1st to 10th	Day	6% 5% 2 5% 5% 4 4 3 5% 6% 54%	2610
	11th to 20th	Day	10% 8% 4 8% 4 4 3 3 4 5% 48%	3008
	21st to end	Day	18% 16% 8% 13% 4 3 4 3 4 4 24%	4053
January	1st to 10th	Night	12% 9% 4 15% 5% 5% 3 3 5% 6% 33%	5888
	11th to 20th	Night	9% 9% 3 8% 4 6% 5% 4 5% 5% 42%	5900
	21st to end	Night	14% 10% 4 10% 5% 4 4 3 4 5% 38%	6490
February	1st to 10th	Night	11% 12% 4 7% 5% 4 5% 3 5% 5% 38%	2600
	11th to 20th	Night	12% 9% 3 8% 4 4 5% 4 4 6% 42%	2533
	21st to end	Night	11% 8% 3 6% 4 4 3 3 5% 6% 47%	1958
March	1st to 10th	Night	15% 8% 3 6% 3 2 3 3 4 5% 49%	4919
	11th to 20th	Night	9% 6% 2 4 3 3 3 3 5% 6% 56%	4980
	21st to end	Night	14% 9% 3 8% 5% 4 4 4 6% 7% 36%	5467
April	1st to 10th	Night	10% 7% 3 6% 4 4 4 3 4 7% 49%	2077
	11th to 20th	Night	13% 8% 3 6% 4 3 3 3 5% 5% 47%	1975
	21st to end	Night	17% 7% 2 7% 4 3 4 3 5% 7% 40%	1854
May	1st to 10th	Night	14% 7% 2 5% 4 4 3 3 5% 7% 45%	4053
	11th to 20th	Night	13% 5% 3 5% 3 3 3 3 4 7% 50%	4053
	21st to end	Night	15% 6% 2 6% 3 3 3 3 4 6% 49%	4133
June	1st to 10th	Night	5% 3 2 3 4 4 4 4 6% 8% 56%	1600
	11th to 20th	Night	5% 4 2 4 4 4 4 5% 8% 9% 51%	1600
	21st to end	Night	4 3 1 3 3 3 3 3 6% 9% 61%	1600
July	1st to 10th	Night	10% 6% 3 6% 5% 3 3 4 5% 7% 48%	2826
	11th to 20th	Night	3 3 1 4 3 3 4 4 6% 10% 61%	2940
	21st to end	Night	5% 3 2 5% 4 4 5% 4 8% 11% 48%	3098
August	1st to 10th	Night	2 2 1 3 3 4 5% 4 6% 11% 60%	2836
	11th to 20th	Night	11% 5% 2 6% 4 3 4 2 4 6% 53%	2798
	21st to end	Night	4 4 2 5% 4 4 4 3 5% 8% 58%	3383
September	1st to 10th	Night	10% 4 1 5% 4 3 4 3 4 6% 57%	1900
	11th to 20th	Night	9% 4 2 4 3 3 3 4 6% 7% 55%	2052
	21st to end	Night	7% 3 2 5% 4 3 4 3 4 6% 58%	2092
October	1st to 10th	Night	11% 5% 2 4 3 3 3 3 4 5% 58%	2280
	11th to 20th	Night	13% 5% 2 4 3 3 2 2 5% 6% 56%	2280
	21st to end	Night	16% 7% 2 5% 3 2 3 2 3 5% 51%	2508
November	1st to 10th	Night	8% 5% 1 3 3 3 3 2 5% 6% 61%	2343
	11th to 20th	Night	11% 7% 2 4 4 3 3 3 5% 6% 53%	2717
	21st to end	Night	14% 8% 2 5% 3 2 3 3 4 6% 50%	2800
December	1st to 10th	Night	7% 7% 2 4 4 3 4 3 5% 7% 54%	4580
	11th to 20th	Night	11% 8% 3 8% 4 3 4 3 6% 7% 44%	5199
	21st to end	Night	19% 16% 6% 10% 4 3 3 3 3 4 29%	6907

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	50% 2 11% 26% 10% 1	4078
	11th to 20th	Day	50% 1 10% 19% 14% 5%	4080
	21st to end	Day	54% 2 11% 16% 16% 2	4488
February	1st to 10th	Day	50% 3 12% 22% 11% 2	1800
	11th to 20th	Day	46% 4 12% 23% 14% 2	1763
	21st to end	Day	40% 3 11% 23% 19% 3	1685
March	1st to 10th	Day	39% 2 9% 22% 23% 5%	4936
	11th to 20th	Day	33% 2 8% 23% 28% 5%	4980
	21st to end	Day	51% 2 17% 24% 5% 1	5464
April	1st to 10th	Day	41% 4 13% 24% 17% 2	2322
	11th to 20th	Day	44% 4 12% 23% 15% 1	2374
	21st to end	Day	49% 4 11% 24% 10% 1	2542
May	1st to 10th	Day	42% 3 11% 27% 15% 1	5900
	11th to 20th	Day	39% 3 12% 25% 18% 3	5866
	21st to end	Day	44% 3 9% 29% 13% 1	6756
June	1st to 10th	Day	31% 5% 16% 31% 15% 2	2800
	11th to 20th	Day	32% 6% 15% 29% 18% 1	2800
	21st to end	Day	30% 6% 17% 29% 15% 4	2800
July	1st to 10th	Day	40% 4 14% 25% 14% 3	4294
	11th to 20th	Day	29% 4 11% 36% 18% 2	4181
	21st to end	Day	31% 3 16% 33% 14% 2	4326
August	1st to 10th	Day	28% 5% 15% 31% 20% 1	4090
	11th to 20th	Day	36% 4 16% 27% 16% 1	4080
	21st to end	Day	30% 3 16% 32% 14% 6%	4261
September	1st to 10th	Day	31% 5% 11% 26% 20% 6%	2280
	11th to 20th	Day	32% 6% 12% 26% 22% 3	2124
	21st to end	Day	30% 4 8% 32% 23% 3	2067
October	1st to 10th	Day	20% 2 7% 22% 43% 6%	3160
	11th to 20th	Day	22% 1 4 26% 37% 9%	3140
	21st to end	Day	34% 2 11% 26% 25% 3	3428
November	1st to 10th	Day	32% 3 13% 28% 19% 4	1953
	11th to 20th	Day	36% 3 10% 28% 20% 3	1680
	21st to end	Day	42% 2 10% 28% 18% 1	1600
December	1st to 10th	Day	32% 2 15% 34% 17% 1	2610
	11th to 20th	Day	41% 2 14% 32% 10% 1	3005
	21st to end	Day	65% 2 12% 14% 6% 1	4053
January	1st to 10th	Night	54% 2 11% 22% 10% 1	5888
	11th to 20th	Night	45% 2 10% 23% 15% 4	5900
	21st to end	Night	51% 2 11% 17% 16% 4	6490
February	1st to 10th	Night	48% 4 11% 21% 14% 3	2600
	11th to 20th	Night	44% 4 11% 22% 16% 3	2534
	21st to end	Night	39% 4 9% 23% 20% 6%	1958
March	1st to 10th	Night	39% 2 8% 23% 24% 4	4919
	11th to 20th	Night	30% 2 6% 25% 30% 7%	4980
	21st to end	Night	49% 2 15% 24% 8% 2	5467
April	1st to 10th	Night	36% 4 11% 25% 20% 4	2077
	11th to 20th	Night	39% 3 10% 28% 15% 4	1975
	21st to end	Night	44% 3 11% 24% 16% 1	1854
May	1st to 10th	Night	40% 3 12% 27% 16% 1	4080
	11th to 20th	Night	35% 3 11% 27% 19% 5%	4054
	21st to end	Night	39% 3 9% 28% 20% 1	4141
June	1st to 10th	Night	24% 5% 17% 33% 17% 3	1600
	11th to 20th	Night	27% 6% 15% 30% 20% 2	1600
	21st to end	Night	20% 4 16% 35% 21% 4	1600
July	1st to 10th	Night	36% 3 12% 24% 22% 4	2781
	11th to 20th	Night	21% 3 14% 37% 22% 2	2886
	21st to end	Night	29% 3 19% 34% 14% 1	2999
August	1st to 10th	Night	19% 3 21% 28% 25% 3	2826
	11th to 20th	Night	35% 2 12% 29% 22% 1	2825
	21st to end	Night	26% 3 14% 36% 17% 5%	3383
September	1st to 10th	Night	30% 4 8% 26% 23% 8%	1900
	11th to 20th	Night	28% 5% 10% 29% 24% 4	2052
	21st to end	Night	28% 4 7% 29% 28% 4	2092
October	1st to 10th	Night	19% 2 6% 20% 47% 6%	3800
	11th to 20th	Night	21% 2 5% 27% 32% 12%	3779
	21st to end	Night	36% 1 7% 29% 25% 2	4120
November	1st to 10th	Night	26% 3 13% 28% 23% 6%	2343
	11th to 20th	Night	33% 3 9% 29% 22% 5%	2717
	21st to end	Night	38% 2 11% 28% 18% 3	2800
December	1st to 10th	Night	32% 2 13% 36% 16% 1	4580
	11th to 20th	Night	41% 2 14% 28% 14% 1	5201
	21st to end	Night	61% 2 10% 19% 6% 1	6907

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	19% 18% 37% 21% 5%	300
	11th to 20th	Day	24% 16% 39% 18% 3	300
	21st to end	Day	15% 15% 44% 23% 2	330
February	1st to 10th	Day	21% 21% 42% 14% 2	300
	11th to 20th	Day	19% 20% 43% 10% 7%	300
	21st to end	Day	15% 22% 40% 20% 2	249
March	1st to 10th	Day	19% 16% 46% 16% 3	300
	11th to 20th	Day	29% 13% 34% 20% 4	300
	21st to end	Day	30% 22% 30% 15% 2 1	330
April	1st to 10th	Day	25% 16% 34% 20% 5%	422
	11th to 20th	Day	19% 17% 37% 20% 6%	492
	21st to end	Day	24% 16% 32% 19% 9% 1	642
May	1st to 10th	Day	18% 13% 36% 24% 8% 1	703
	11th to 20th	Day	18% 12% 29% 25% 13% 3	725
	21st to end	Day	18% 7% 31% 25% 15% 3	789
June	1st to 10th	Day	7% 5% 22% 34% 25% 7%	730
	11th to 20th	Day	7% 4 28% 35% 20% 5%	730
	21st to end	Day	5% 6% 35% 36% 15% 2	730
July	1st to 10th	Day	10% 3 15% 31% 31% 10%	721
	11th to 20th	Day	7% 2 22% 38% 25% 6%	718
	21st to end	Day	8% 2 18% 36% 30% 6%	740
August	1st to 10th	Day	6% 2 18% 41% 27% 6%	676
	11th to 20th	Day	8% 4 19% 38% 27% 5%	665
	21st to end	Day	9% 2 17% 32% 31% 9%	595
September	1st to 10th	Day	12% 4 17% 35% 26% 6%	490
	11th to 20th	Day	7% 3 21% 37% 26% 6%	334
	21st to end	Day	13% 6% 27% 36% 13% 6%	300
October	1st to 10th	Day	15% 5% 26% 31% 18% 5%	300
	11th to 20th	Day	11% 18% 39% 22% 8% 1	300
	21st to end	Day	18% 17% 35% 23% 6%	330
November	1st to 10th	Day	16% 9% 39% 26% 7% 3	300
	11th to 20th	Day	18% 16% 37% 20% 7% 2	300
	21st to end	Day	21% 15% 36% 21% 7%	300
December	1st to 10th	Day	7% 18% 42% 24% 7% 3	300
	11th to 20th	Day	21% 15% 36% 23% 4 1	300
	21st to end	Day	20% 20% 42% 17% 2	330
January	1st to 10th	Night	13% 14% 38% 29% 6%	1000
	11th to 20th	Night	17% 15% 37% 25% 6%	1000
	21st to end	Night	15% 12% 44% 27% 3	1100
February	1st to 10th	Night	17% 14% 42% 24% 3	1000
	11th to 20th	Night	17% 15% 37% 27% 3	979
	21st to end	Night	18% 13% 45% 18% 4 1	638
March	1st to 10th	Night	15% 14% 41% 25% 5%	600
	11th to 20th	Night	20% 10% 37% 26% 6% 1	600
	21st to end	Night	26% 11% 40% 21% 3	660
April	1st to 10th	Night	13% 14% 42% 27% 4	600
	11th to 20th	Night	18% 14% 36% 27% 5%	593
	21st to end	Night	19% 9% 39% 26% 6% 1	600
May	1st to 10th	Night	16% 9% 35% 33% 7% 1	600
	11th to 20th	Night	15% 7% 28% 36% 13% 1	591
	21st to end	Night	13% 5% 30% 37% 13% 2	650
June	1st to 10th	Night	5% 4 21% 46% 22% 2	600
	11th to 20th	Night	7% 2 26% 46% 19% 2	600
	21st to end	Night	5% 3 31% 46% 14%	600
July	1st to 10th	Night	6% 2 15% 43% 30% 4	585
	11th to 20th	Night	4 3 16% 47% 28% 2	582
	21st to end	Night	7% 1 15% 44% 32% 2	624
August	1st to 10th	Night	4 2 17% 47% 30% 1	567
	11th to 20th	Night	9% 2 14% 45% 29% 3	564
	21st to end	Night	7% 1 15% 41% 33% 3	627
September	1st to 10th	Night	10% 2 16% 42% 25% 4	570
	11th to 20th	Night	11% 2 19% 43% 23% 3	570
	21st to end	Night	7% 6% 23% 42% 20% 2	572
October	1st to 10th	Night	14% 5% 29% 32% 18% 2	760
	11th to 20th	Night	15% 8% 38% 30% 9%	760
	21st to end	Night	19% 12% 33% 28% 8%	836
November	1st to 10th	Night	11% 10% 35% 35% 9% 1	783
	11th to 20th	Night	14% 15% 36% 27% 8%	1000
	21st to end	Night	19% 11% 35% 28% 7%	1000
December	1st to 10th	Night	15% 13% 35% 30% 6% 1	1000
	11th to 20th	Night	19% 11% 38% 28% 6%	1000
	21st to end	Night	20% 16% 34% 26% 4	1100

Page generated at 2025-07-18 00:10:00. Version ac07

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