Smithville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smithville clear sky chart from 2005-11-06 to 2026-08-15.

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% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	143716
	Night	13% 8% 3 7% 5% 4 4 4 5% 7% 40%	138157
Transparency	Day	43% 7% 11% 21% 15% 3	147428
	Night	41% 6% 11% 21% 17% 4	142519
Seeing	Day	16% 9% 22% 22% 19% 11%	17181
	Night	17% 7% 23% 30% 19% 3	26900

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	17% 12% 5% 12% 5% 4 5% 3 4 5% 28%	5258
	11th to 20th	Day	14% 7% 5% 12% 3 3 3 2 3 4 42%	5280
	21st to end	Day	20% 9% 5% 7% 5% 5% 3 3 5% 6% 32%	6138
February	1st to 10th	Day	18% 13% 5% 7% 5% 4 3 3 4 4 34%	2100
	11th to 20th	Day	21% 10% 4 8% 5% 4 3 3 4 6% 31%	2048
	21st to end	Day	19% 9% 3 8% 4 4 4 3 5% 6% 35%	1730
March	1st to 10th	Day	16% 11% 4 7% 5% 5% 4 3 5% 6% 34%	4580
	11th to 20th	Day	12% 8% 3 7% 5% 4 4 3 4 6% 45%	4991
	21st to end	Day	12% 8% 2 7% 5% 4 4 4 6% 7% 42%	5690
April	1st to 10th	Day	12% 7% 2 7% 4 4 5% 4 6% 7% 43%	2520
	11th to 20th	Day	12% 7% 3 7% 4 5% 4 3 6% 7% 44%	2494
	21st to end	Day	11% 8% 3 7% 6% 4 5% 4 6% 7% 39%	2625
May	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 7% 9% 32%	7616
	11th to 20th	Day	11% 8% 4 9% 6% 5% 5% 4 6% 7% 35%	7626
	21st to end	Day	16% 11% 4 10% 6% 5% 5% 3 5% 6% 29%	8391
June	1st to 10th	Day	9% 7% 3 6% 4 6% 6% 4 7% 10% 39%	2730
	11th to 20th	Day	5% 5% 2 6% 5% 5% 6% 5% 7% 10% 43%	2730
	21st to end	Day	6% 5% 1 6% 6% 6% 6% 6% 8% 13% 38%	2880
July	1st to 10th	Day	6% 5% 2 7% 5% 6% 7% 6% 8% 12% 36%	7980
	11th to 20th	Day	8% 7% 3 9% 7% 7% 8% 7% 9% 11% 25%	7680
	21st to end	Day	10% 8% 3 9% 6% 6% 6% 5% 8% 12% 27%	8340
August	1st to 10th	Day	5% 4 2 6% 4 5% 6% 5% 8% 11% 44%	4303
	11th to 20th	Day	5% 5% 2 7% 5% 5% 6% 5% 9% 12% 38%	3897
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 6% 9% 49%	4312
September	1st to 10th	Day	12% 5% 3 7% 5% 5% 4 5% 6% 8% 40%	2316
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 3 5% 7% 43%	2200
	21st to end	Day	12% 6% 2 6% 4 4 4 4 5% 6% 47%	2200
October	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 5% 6% 53%	2200
	11th to 20th	Day	11% 5% 1 5% 3 4 3 2 4 7% 54%	2156
	21st to end	Day	15% 6% 2 5% 4 3 4 3 5% 6% 46%	2025
November	1st to 10th	Day	11% 6% 2 5% 4 2 3 3 4 7% 53%	1852
	11th to 20th	Day	14% 8% 2 5% 4 3 3 3 5% 7% 47%	1890
	21st to end	Day	14% 9% 3 6% 4 4 4 3 5% 5% 44%	1890
December	1st to 10th	Day	14% 9% 3 8% 5% 5% 4 3 4 5% 40%	3020
	11th to 20th	Day	18% 14% 5% 9% 6% 4 4 3 4 5% 29%	3463
	21st to end	Day	17% 13% 5% 9% 5% 4 4 4 5% 7% 27%	4565
January	1st to 10th	Night	15% 10% 4 9% 4 3 3 3 4 5% 39%	7635
	11th to 20th	Night	16% 8% 3 7% 5% 5% 3 3 3 5% 42%	7680
	21st to end	Night	17% 13% 4 8% 4 4 4 3 4 5% 35%	8025
February	1st to 10th	Night	19% 9% 4 9% 5% 4 4 3 5% 6% 32%	2520
	11th to 20th	Night	23% 10% 4 8% 4 4 4 3 4 5% 33%	2458
	21st to end	Night	22% 10% 3 8% 4 3 4 3 5% 7% 32%	2076
March	1st to 10th	Night	18% 12% 4 8% 4 4 4 3 5% 7% 33%	5493
	11th to 20th	Night	12% 6% 2 5% 3 3 4 4 6% 7% 48%	5188
	21st to end	Night	13% 7% 3 8% 5% 5% 4 3 5% 6% 40%	5524
April	1st to 10th	Night	12% 5% 2 5% 5% 5% 5% 4 6% 8% 45%	2100
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 5% 7% 49%	2075
	21st to end	Night	12% 6% 3 7% 5% 4 4 3 6% 8% 43%	1992
May	1st to 10th	Night	13% 9% 3 8% 6% 5% 5% 4 6% 9% 32%	5237
	11th to 20th	Night	12% 8% 3 9% 6% 5% 5% 4 6% 7% 36%	5234
	21st to end	Night	15% 9% 4 9% 6% 5% 5% 4 6% 8% 28%	5761
June	1st to 10th	Night	7% 6% 3 7% 5% 4 5% 4 6% 9% 45%	1890
	11th to 20th	Night	4 3 2 5% 4 5% 4 4 7% 12% 50%	1890
	21st to end	Night	5% 3 2 4 5% 4 6% 4 8% 12% 46%	1720
July	1st to 10th	Night	6% 5% 2 8% 5% 5% 5% 6% 9% 10% 39%	4953
	11th to 20th	Night	7% 7% 3 8% 5% 6% 7% 5% 9% 11% 32%	5277
	21st to end	Night	8% 7% 3 9% 6% 6% 6% 6% 8% 12% 29%	5736
August	1st to 10th	Night	3 5% 2 5% 5% 5% 4 4 6% 9% 51%	3061
	11th to 20th	Night	5% 4 2 6% 4 5% 5% 5% 8% 11% 45%	3240
	21st to end	Night	5% 3 1 5% 4 4 4 4 6% 9% 56%	3586
September	1st to 10th	Night	9% 6% 2 6% 4 4 5% 4 6% 7% 46%	2062
	11th to 20th	Night	9% 6% 2 7% 5% 3 5% 3 5% 7% 45%	2200
	21st to end	Night	11% 5% 2 6% 4 4 3 3 5% 8% 50%	2200
October	1st to 10th	Night	10% 4 1 4 3 3 3 3 4 6% 58%	2200
	11th to 20th	Night	14% 5% 2 6% 4 3 3 3 4 5% 52%	2242
	21st to end	Night	14% 8% 2 5% 3 3 3 3 5% 6% 48%	2811
November	1st to 10th	Night	12% 7% 2 5% 4 3 4 3 4 6% 52%	2666
	11th to 20th	Night	13% 8% 2 5% 4 3 3 3 5% 7% 49%	2730
	21st to end	Night	15% 9% 4 5% 3 3 4 3 5% 6% 43%	2730
December	1st to 10th	Night	16% 11% 4 9% 4 4 4 3 4 4 37%	4380
	11th to 20th	Night	21% 11% 3 7% 4 3 3 2 4 5% 36%	4952
	21st to end	Night	14% 12% 5% 9% 6% 5% 5% 4 5% 7% 28%	6633

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	57% 4 10% 18% 10% 1	5259
	11th to 20th	Day	46% 3 5% 18% 26% 2	5280
	21st to end	Day	52% 3 7% 22% 11% 4	6138
February	1st to 10th	Day	54% 4 7% 18% 16% 2	2100
	11th to 20th	Day	56% 4 7% 17% 14% 3	2058
	21st to end	Day	51% 3 7% 16% 17% 5%	1730
March	1st to 10th	Day	50% 5% 6% 14% 17% 8%	4580
	11th to 20th	Day	40% 4 7% 21% 19% 9%	4991
	21st to end	Day	41% 5% 10% 28% 15% 1	5692
April	1st to 10th	Day	38% 5% 12% 24% 17% 3	2520
	11th to 20th	Day	39% 4 7% 22% 23% 4	2494
	21st to end	Day	43% 5% 9% 26% 15% 2	2625
May	1st to 10th	Day	46% 8% 13% 22% 11% 1	7651
	11th to 20th	Day	47% 7% 12% 22% 12% 1	7630
	21st to end	Day	55% 7% 7% 16% 12% 2	8405
June	1st to 10th	Day	39% 7% 13% 23% 16% 2	2730
	11th to 20th	Day	34% 8% 17% 22% 17% 2	2730
	21st to end	Day	34% 9% 18% 21% 15% 4	2880
July	1st to 10th	Day	36% 11% 19% 23% 9% 1	7915
	11th to 20th	Day	44% 15% 18% 18% 4 1	7611
	21st to end	Day	45% 10% 20% 18% 7% 1	8156
August	1st to 10th	Day	29% 10% 16% 30% 14% 1	4290
	11th to 20th	Day	33% 9% 16% 26% 14% 1	3933
	21st to end	Day	29% 9% 11% 31% 19% 2	4311
September	1st to 10th	Day	40% 8% 11% 19% 17% 5%	2316
	11th to 20th	Day	40% 6% 11% 22% 19% 2	2200
	21st to end	Day	37% 6% 9% 22% 21% 5%	2200
October	1st to 10th	Day	24% 5% 7% 18% 35% 11%	3590
	11th to 20th	Day	23% 2 7% 25% 30% 14%	3487
	21st to end	Day	30% 3 8% 24% 25% 10%	3249
November	1st to 10th	Day	33% 3 9% 21% 29% 5%	1852
	11th to 20th	Day	37% 4 6% 24% 23% 6%	1890
	21st to end	Day	43% 3 7% 22% 20% 4	1890
December	1st to 10th	Day	45% 5% 5% 22% 21% 2	3020
	11th to 20th	Day	57% 4 7% 18% 12% 2	3460
	21st to end	Day	54% 6% 10% 21% 9% 1	4565
January	1st to 10th	Night	48% 3 15% 20% 13% 1	7636
	11th to 20th	Night	45% 3 6% 18% 23% 4	7680
	21st to end	Night	53% 3 7% 17% 15% 5%	8025
February	1st to 10th	Night	53% 4 8% 18% 16% 1	2520
	11th to 20th	Night	56% 3 6% 17% 14% 4	2459
	21st to end	Night	53% 4 6% 16% 17% 4	2076
March	1st to 10th	Night	51% 4 7% 15% 18% 4	5493
	11th to 20th	Night	34% 5% 7% 21% 20% 12%	5188
	21st to end	Night	45% 4 9% 26% 15% 2	5524
April	1st to 10th	Night	37% 4 11% 24% 20% 3	2100
	11th to 20th	Night	35% 4 8% 24% 23% 6%	2075
	21st to end	Night	39% 5% 10% 28% 17% 1	1992
May	1st to 10th	Night	46% 8% 13% 22% 11% 1	5264
	11th to 20th	Night	45% 8% 13% 17% 16% 1	5235
	21st to end	Night	51% 10% 11% 17% 11% 1	5771
June	1st to 10th	Night	35% 7% 13% 27% 15% 3	1890
	11th to 20th	Night	25% 7% 19% 30% 16% 2	1890
	21st to end	Night	28% 10% 16% 28% 14% 4	1720
July	1st to 10th	Night	35% 11% 21% 22% 10% 1	4911
	11th to 20th	Night	40% 14% 20% 20% 5% 1	5226
	21st to end	Night	43% 11% 23% 15% 7% 1	5606
August	1st to 10th	Night	26% 8% 13% 36% 16% 1	3050
	11th to 20th	Night	28% 9% 22% 27% 13% 1	3270
	21st to end	Night	23% 8% 13% 35% 19% 2	3586
September	1st to 10th	Night	36% 7% 13% 21% 18% 5%	2062
	11th to 20th	Night	36% 7% 11% 21% 24% 2	2200
	21st to end	Night	34% 5% 10% 22% 24% 5%	2200
October	1st to 10th	Night	23% 6% 7% 21% 32% 11%	3590
	11th to 20th	Night	22% 3 5% 24% 30% 16%	3650
	21st to end	Night	25% 3 7% 24% 31% 9%	4537
November	1st to 10th	Night	35% 3 7% 23% 24% 7%	2666
	11th to 20th	Night	36% 2 7% 22% 25% 7%	2730
	21st to end	Night	43% 3 6% 25% 19% 4	2730
December	1st to 10th	Night	50% 4 6% 16% 23% 1	4380
	11th to 20th	Night	51% 3 6% 21% 18% 2	4954
	21st to end	Night	54% 5% 9% 21% 10% 1	6633

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% 17% 34% 18% 5% 1	330
	11th to 20th	Day	28% 20% 34% 11% 6% 1	330
	21st to end	Day	22% 17% 42% 15% 4	363
February	1st to 10th	Day	27% 18% 33% 15% 7%	330
	11th to 20th	Day	35% 16% 36% 10% 3 1	330
	21st to end	Day	28% 20% 36% 13% 3	273
March	1st to 10th	Day	25% 17% 34% 17% 6% 1	330
	11th to 20th	Day	23% 17% 33% 19% 6% 1	493
	21st to end	Day	22% 17% 33% 19% 9% 1	594
April	1st to 10th	Day	17% 17% 29% 25% 10% 3	540
	11th to 20th	Day	15% 14% 28% 27% 14% 2	532
	21st to end	Day	16% 10% 31% 26% 13% 3	540
May	1st to 10th	Day	18% 12% 28% 24% 14% 4	543
	11th to 20th	Day	14% 8% 24% 25% 19% 10%	567
	21st to end	Day	14% 6% 19% 25% 20% 15%	617
June	1st to 10th	Day	11% 6% 18% 24% 24% 17%	570
	11th to 20th	Day	6% 4 15% 26% 29% 19%	570
	21st to end	Day	8% 2 15% 27% 28% 19%	720
July	1st to 10th	Day	10% 3 9% 26% 29% 24%	670
	11th to 20th	Day	11% 4 8% 21% 30% 26%	564
	21st to end	Day	11% 3 10% 19% 29% 27%	620
August	1st to 10th	Day	11% 3 10% 21% 31% 24%	566
	11th to 20th	Day	10% 1 13% 24% 36% 15%	535
	21st to end	Day	10% 1 9% 22% 31% 27%	583
September	1st to 10th	Day	13% 2 10% 21% 34% 20%	530
	11th to 20th	Day	13% 3 11% 19% 33% 21%	530
	21st to end	Day	16% 5% 15% 25% 28% 12%	530
October	1st to 10th	Day	12% 2 17% 27% 29% 12%	530
	11th to 20th	Day	12% 7% 26% 29% 20% 5%	530
	21st to end	Day	18% 11% 23% 28% 16% 4	408
November	1st to 10th	Day	17% 8% 26% 29% 15% 4	330
	11th to 20th	Day	13% 14% 35% 29% 9%	330
	21st to end	Day	19% 13% 36% 18% 12% 2	330
December	1st to 10th	Day	23% 16% 35% 19% 6% 1	330
	11th to 20th	Day	22% 15% 31% 20% 11% 1	330
	21st to end	Day	24% 21% 29% 18% 7% 1	363
January	1st to 10th	Night	23% 13% 34% 26% 5%	840
	11th to 20th	Night	25% 16% 33% 21% 4	840
	21st to end	Night	20% 12% 41% 25% 3	924
February	1st to 10th	Night	25% 12% 33% 26% 4	840
	11th to 20th	Night	29% 15% 34% 21% 2	823
	21st to end	Night	29% 14% 34% 22% 1	692
March	1st to 10th	Night	21% 13% 32% 30% 4	840
	11th to 20th	Night	22% 11% 35% 25% 6% 1	840
	21st to end	Night	19% 10% 33% 29% 9%	898
April	1st to 10th	Night	15% 10% 33% 33% 10%	630
	11th to 20th	Night	17% 7% 32% 33% 11% 1	623
	21st to end	Night	15% 7% 28% 36% 13% 1	630
May	1st to 10th	Night	13% 6% 31% 31% 18% 1	630
	11th to 20th	Night	13% 4 21% 36% 21% 5%	621
	21st to end	Night	10% 4 15% 35% 29% 7%	683
June	1st to 10th	Night	9% 3 15% 35% 34% 4	630
	11th to 20th	Night	6% 1 13% 37% 37% 8%	630
	21st to end	Night	6% 2 9% 37% 39% 8%	630
July	1st to 10th	Night	10% 2 7% 27% 40% 13%	615
	11th to 20th	Night	8% 2 7% 28% 44% 12%	612
	21st to end	Night	9% 3 7% 30% 42% 9%	690
August	1st to 10th	Night	7% 2 5% 29% 47% 9%	627
	11th to 20th	Night	8% 9% 31% 45% 7%	606
	21st to end	Night	9% 2 6% 28% 46% 9%	660
September	1st to 10th	Night	11% 3 8% 31% 39% 8%	662
	11th to 20th	Night	12% 2 11% 30% 39% 7%	800
	21st to end	Night	12% 2 17% 29% 34% 5%	800
October	1st to 10th	Night	12% 3 15% 33% 31% 6%	800
	11th to 20th	Night	16% 5% 21% 37% 19% 2	800
	21st to end	Night	18% 5% 24% 34% 16% 2	880
November	1st to 10th	Night	15% 7% 23% 34% 19% 2	820
	11th to 20th	Night	17% 9% 30% 33% 10% 1	840
	21st to end	Night	20% 10% 28% 30% 11% 1	840
December	1st to 10th	Night	26% 11% 29% 28% 7%	840
	11th to 20th	Night	23% 8% 31% 30% 7% 1	840
	21st to end	Night	25% 14% 28% 27% 6%	924

Page generated at 2026-08-12 02:37:18. Version ac07

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