Tyler
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tyler clear sky chart from 2005-11-06 to 2026-06-16.

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% 6% 2 6% 4 4 4 4 5% 7% 46%	137705
	Night	12% 6% 2 5% 3 3 3 3 5% 7% 51%	134646
Transparency	Day	36% 4 10% 23% 20% 7%	141343
	Night	33% 4 10% 21% 22% 10%	139075
Seeing	Day	13% 7% 21% 28% 23% 8%	17241
	Night	13% 7% 26% 33% 18% 2	27105

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	13% 8% 3 6% 3 3 3 3 5% 6% 48%	5289
	11th to 20th	Day	10% 4 2 4 3 2 3 3 5% 7% 57%	5310
	21st to end	Day	25% 9% 3 7% 4 2 2 2 3 4 40%	5812
February	1st to 10th	Day	20% 9% 3 7% 3 3 3 3 3 5% 42%	1895
	11th to 20th	Day	19% 9% 2 7% 4 4 2 3 3 5% 41%	2049
	21st to end	Day	20% 7% 2 5% 3 3 3 2 3 4 47%	1881
March	1st to 10th	Day	15% 10% 3 7% 4 4 3 3 4 6% 41%	5046
	11th to 20th	Day	13% 6% 2 4 4 3 3 3 5% 6% 52%	5090
	21st to end	Day	14% 8% 3 6% 4 3 4 3 5% 7% 43%	5583
April	1st to 10th	Day	14% 8% 2 5% 5% 4 4 4 5% 6% 43%	2310
	11th to 20th	Day	14% 8% 3 6% 5% 4 4 4 6% 7% 40%	2492
	21st to end	Day	11% 7% 2 6% 5% 4 5% 4 6% 9% 41%	2520
May	1st to 10th	Day	21% 9% 3 7% 4 4 4 3 5% 6% 35%	7488
	11th to 20th	Day	13% 7% 3 8% 5% 4 5% 4 5% 6% 39%	7627
	21st to end	Day	12% 7% 3 7% 5% 5% 6% 5% 7% 9% 34%	8392
June	1st to 10th	Day	7% 5% 2 7% 5% 6% 5% 4 7% 10% 42%	2730
	11th to 20th	Day	5% 4 1 5% 5% 5% 5% 5% 8% 10% 47%	2666
	21st to end	Day	5% 3 2 5% 5% 5% 6% 5% 7% 10% 47%	2600
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 6% 9% 13% 33%	5900
	11th to 20th	Day	4 3 1 4 4 4 4 4 7% 10% 56%	5900
	21st to end	Day	8% 7% 3 7% 5% 4 5% 4 6% 8% 44%	6422
August	1st to 10th	Day	2 1 1 3 2 3 3 3 6% 8% 69%	4234
	11th to 20th	Day	3 3 1 3 3 3 4 5% 7% 11% 56%	4087
	21st to end	Day	5% 5% 2 6% 5% 6% 7% 6% 9% 9% 41%	4312
September	1st to 10th	Day	7% 6% 3 5% 4 5% 5% 3 5% 7% 50%	2238
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 7% 8% 44%	2200
	21st to end	Day	7% 2 2 4 4 4 4 3 5% 8% 56%	2200
October	1st to 10th	Day	6% 3 2 4 3 4 3 3 5% 6% 63%	2055
	11th to 20th	Day	12% 4 2 4 3 3 3 3 4 5% 58%	2000
	21st to end	Day	14% 5% 2 4 3 2 3 2 3 3 58%	2200
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 5% 6% 53%	2058
	11th to 20th	Day	9% 5% 2 5% 4 3 3 3 5% 5% 55%	2100
	21st to end	Day	17% 8% 3 5% 3 3 3 2 4 5% 47%	1921
December	1st to 10th	Day	18% 6% 2 5% 3 2 2 3 4 6% 49%	3030
	11th to 20th	Day	16% 9% 3 6% 5% 3 4 4 5% 6% 40%	3481
	21st to end	Day	15% 10% 3 8% 3 3 3 2 3 5% 44%	4587
January	1st to 10th	Night	14% 6% 2 5% 4 3 3 2 4 5% 52%	7634
	11th to 20th	Night	9% 4 1 3 2 2 2 2 4 7% 63%	7680
	21st to end	Night	25% 10% 2 6% 3 3 3 2 3 4 38%	8402
February	1st to 10th	Night	17% 8% 2 5% 3 3 3 2 4 6% 48%	2730
	11th to 20th	Night	19% 8% 3 6% 3 3 3 2 4 5% 45%	2471
	21st to end	Night	18% 7% 1 5% 3 3 3 3 4 5% 49%	1924
March	1st to 10th	Night	20% 9% 2 6% 3 3 3 2 4 6% 42%	5029
	11th to 20th	Night	11% 6% 2 6% 3 3 3 3 4 6% 51%	5090
	21st to end	Night	13% 6% 2 6% 4 4 4 3 4 6% 47%	5588
April	1st to 10th	Night	12% 4 2 5% 3 4 4 4 5% 7% 49%	2310
	11th to 20th	Night	11% 7% 1 5% 4 4 4 4 6% 7% 46%	2075
	21st to end	Night	11% 6% 2 5% 4 3 3 3 6% 7% 50%	2100
May	1st to 10th	Night	18% 10% 3 7% 4 4 4 3 5% 7% 35%	5384
	11th to 20th	Night	11% 8% 3 8% 4 4 4 3 5% 7% 43%	5265
	21st to end	Night	11% 7% 2 6% 4 4 4 4 7% 9% 42%	5793
June	1st to 10th	Night	6% 3 2 4 3 3 4 4 9% 9% 54%	1890
	11th to 20th	Night	3 3 1 3 3 3 4 3 7% 8% 62%	1845
	21st to end	Night	4 4 2 4 4 3 4 4 6% 9% 57%	1800
July	1st to 10th	Night	5% 5% 2 6% 4 5% 6% 5% 9% 13% 40%	4078
	11th to 20th	Night	2 2 1 3 3 3 3 4 7% 12% 61%	4077
	21st to end	Night	5% 5% 2 5% 4 4 4 4 6% 10% 51%	4449
August	1st to 10th	Night	2 1 1 2 1 2 3 2 5% 8% 74%	2926
	11th to 20th	Night	3 2 1 3 2 2 4 3 7% 12% 61%	2967
	21st to end	Night	3 3 1 4 3 4 4 5% 8% 10% 54%	3586
September	1st to 10th	Night	7% 4 2 5% 3 4 4 3 6% 7% 54%	2156
	11th to 20th	Night	10% 4 2 5% 3 4 4 3 5% 8% 54%	2200
	21st to end	Night	6% 3 1 4 3 3 3 3 5% 8% 61%	2200
October	1st to 10th	Night	5% 3 1 3 2 2 3 3 4 6% 66%	2325
	11th to 20th	Night	10% 5% 1 3 2 2 3 2 3 5% 64%	2400
	21st to end	Night	14% 4 2 3 2 2 2 2 3 4 60%	2640
November	1st to 10th	Night	11% 5% 1 4 3 3 3 2 4 5% 59%	2460
	11th to 20th	Night	8% 5% 2 5% 4 3 3 3 4 6% 57%	2520
	21st to end	Night	14% 7% 3 5% 3 3 3 3 5% 5% 50%	2693
December	1st to 10th	Night	17% 8% 2 5% 3 3 3 2 3 5% 49%	4380
	11th to 20th	Night	15% 9% 3 6% 4 4 3 2 3 4 46%	4946
	21st to end	Night	13% 10% 2 5% 4 3 3 2 3 4 51%	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	38% 3 7% 26% 24% 3	5290
	11th to 20th	Day	28% 3 5% 25% 31% 8%	5310
	21st to end	Day	51% 2 3 13% 21% 11%	5812
February	1st to 10th	Day	47% 3 4 17% 19% 10%	1895
	11th to 20th	Day	48% 3 6% 18% 18% 7%	2059
	21st to end	Day	42% 3 7% 14% 23% 11%	1881
March	1st to 10th	Day	45% 4 5% 13% 21% 13%	5046
	11th to 20th	Day	35% 2 5% 18% 19% 21%	5090
	21st to end	Day	42% 3 9% 22% 19% 5%	5585
April	1st to 10th	Day	41% 4 9% 22% 17% 8%	2310
	11th to 20th	Day	43% 5% 10% 15% 20% 7%	2492
	21st to end	Day	39% 6% 9% 20% 22% 4	2520
May	1st to 10th	Day	50% 3 11% 22% 12% 2	7525
	11th to 20th	Day	44% 4 10% 18% 21% 3	7631
	21st to end	Day	45% 5% 15% 20% 13% 2	8405
June	1st to 10th	Day	34% 6% 16% 28% 14% 1	2730
	11th to 20th	Day	29% 6% 16% 29% 16% 4	2666
	21st to end	Day	29% 9% 13% 31% 16% 2	2600
July	1st to 10th	Day	38% 9% 23% 23% 6%	5836
	11th to 20th	Day	23% 6% 18% 38% 15% 1	5831
	21st to end	Day	36% 6% 13% 32% 12% 1	6240
August	1st to 10th	Day	14% 4 14% 34% 30% 4	4220
	11th to 20th	Day	20% 5% 17% 44% 13% 1	4126
	21st to end	Day	34% 9% 17% 25% 14% 1	4311
September	1st to 10th	Day	33% 5% 12% 21% 19% 10%	2238
	11th to 20th	Day	35% 8% 11% 20% 18% 8%	2200
	21st to end	Day	26% 4 9% 23% 25% 12%	2200
October	1st to 10th	Day	14% 2 6% 13% 26% 39%	3341
	11th to 20th	Day	19% 2 4 20% 31% 23%	3240
	21st to end	Day	26% 4 4 23% 34% 10%	3538
November	1st to 10th	Day	34% 3 8% 20% 27% 9%	2058
	11th to 20th	Day	32% 2 8% 20% 26% 12%	2100
	21st to end	Day	42% 3 5% 18% 24% 9%	1921
December	1st to 10th	Day	39% 2 7% 21% 25% 6%	3030
	11th to 20th	Day	44% 3 6% 13% 22% 11%	3479
	21st to end	Day	45% 2 5% 18% 25% 6%	4587
January	1st to 10th	Night	37% 3 6% 21% 28% 5%	7635
	11th to 20th	Night	24% 2 5% 19% 35% 15%	7680
	21st to end	Night	52% 2 4 13% 18% 11%	8402
February	1st to 10th	Night	39% 3 6% 19% 21% 12%	2730
	11th to 20th	Night	43% 3 6% 18% 22% 9%	2471
	21st to end	Night	39% 3 7% 15% 22% 14%	1924
March	1st to 10th	Night	45% 3 5% 12% 20% 15%	5029
	11th to 20th	Night	35% 3 8% 15% 18% 22%	5090
	21st to end	Night	40% 3 8% 21% 22% 7%	5588
April	1st to 10th	Night	34% 4 11% 21% 18% 12%	2310
	11th to 20th	Night	37% 5% 10% 18% 19% 11%	2075
	21st to end	Night	33% 4 10% 21% 26% 5%	2100
May	1st to 10th	Night	49% 4 11% 20% 13% 3	5412
	11th to 20th	Night	42% 4 13% 18% 21% 3	5266
	21st to end	Night	39% 5% 18% 23% 9% 5%	5805
June	1st to 10th	Night	23% 7% 17% 30% 21% 3	1890
	11th to 20th	Night	20% 6% 17% 33% 20% 5%	1845
	21st to end	Night	24% 5% 16% 28% 24% 3	1800
July	1st to 10th	Night	33% 6% 25% 30% 6%	4035
	11th to 20th	Night	17% 5% 24% 36% 17% 2	4026
	21st to end	Night	28% 7% 18% 33% 12% 2	4320
August	1st to 10th	Night	10% 3 14% 33% 33% 7%	2916
	11th to 20th	Night	16% 5% 17% 45% 14% 3	2994
	21st to end	Night	23% 7% 19% 29% 19% 3	3586
September	1st to 10th	Night	30% 6% 12% 23% 20% 10%	2156
	11th to 20th	Night	30% 5% 11% 25% 20% 9%	2200
	21st to end	Night	22% 4 9% 23% 29% 13%	2200
October	1st to 10th	Night	12% 2 6% 14% 21% 45%	3806
	11th to 20th	Night	16% 2 3 18% 34% 27%	3899
	21st to end	Night	24% 3 4 19% 33% 16%	4252
November	1st to 10th	Night	29% 3 8% 20% 26% 14%	2460
	11th to 20th	Night	30% 3 7% 20% 26% 15%	2520
	21st to end	Night	38% 3 7% 18% 24% 11%	2693
December	1st to 10th	Night	40% 2 6% 16% 29% 7%	4380
	11th to 20th	Night	44% 3 6% 12% 23% 12%	4947
	21st to end	Night	39% 3 5% 17% 27% 9%	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	22% 14% 37% 19% 7%	330
	11th to 20th	Day	19% 16% 41% 17% 8%	330
	21st to end	Day	24% 17% 37% 17% 5%	363
February	1st to 10th	Day	26% 11% 39% 18% 5% 1	330
	11th to 20th	Day	30% 18% 37% 12% 3	330
	21st to end	Day	26% 19% 39% 13% 3	273
March	1st to 10th	Day	23% 15% 35% 22% 5% 1	330
	11th to 20th	Day	19% 22% 37% 18% 3	330
	21st to end	Day	14% 16% 39% 24% 7%	363
April	1st to 10th	Day	20% 15% 37% 22% 5% 1	330
	11th to 20th	Day	22% 14% 30% 23% 9% 1	530
	21st to end	Day	18% 11% 33% 26% 10% 2	540
May	1st to 10th	Day	16% 9% 33% 33% 10%	701
	11th to 20th	Day	14% 7% 25% 33% 17% 4	775
	21st to end	Day	11% 5% 24% 36% 19% 5%	844
June	1st to 10th	Day	9% 3 13% 34% 33% 8%	780
	11th to 20th	Day	6% 2 14% 38% 31% 9%	756
	21st to end	Day	5% 2 9% 32% 35% 17%	730
July	1st to 10th	Day	7% 3 7% 30% 39% 14%	721
	11th to 20th	Day	3 1 5% 30% 43% 19%	718
	21st to end	Day	5% 1 4 28% 45% 17%	794
August	1st to 10th	Day	4 1 4 25% 47% 19%	726
	11th to 20th	Day	6% 1 3 29% 46% 15%	670
	21st to end	Day	10% 2 4 21% 37% 26%	583
September	1st to 10th	Day	7% 1 9% 24% 38% 21%	368
	11th to 20th	Day	5% 1 8% 28% 35% 23%	330
	21st to end	Day	8% 2 11% 32% 30% 17%	330
October	1st to 10th	Day	5% 2 14% 38% 34% 7%	330
	11th to 20th	Day	10% 5% 27% 32% 19% 6%	330
	21st to end	Day	23% 8% 25% 28% 13% 4	363
November	1st to 10th	Day	18% 10% 24% 30% 16% 2	330
	11th to 20th	Day	12% 9% 30% 36% 10% 3	330
	21st to end	Day	18% 13% 33% 25% 10% 1	330
December	1st to 10th	Day	19% 11% 35% 25% 8% 2	330
	11th to 20th	Day	23% 12% 34% 22% 7% 1	330
	21st to end	Day	22% 16% 33% 23% 5% 1	363
January	1st to 10th	Night	18% 11% 35% 29% 7%	1050
	11th to 20th	Night	20% 14% 33% 28% 5%	1050
	21st to end	Night	22% 10% 36% 28% 5%	1155
February	1st to 10th	Night	21% 12% 35% 28% 4	1050
	11th to 20th	Night	25% 14% 35% 23% 3	837
	21st to end	Night	22% 16% 39% 21% 3	540
March	1st to 10th	Night	19% 12% 36% 28% 6%	630
	11th to 20th	Night	16% 11% 39% 28% 6%	630
	21st to end	Night	14% 10% 39% 31% 6%	693
April	1st to 10th	Night	13% 12% 40% 30% 6%	630
	11th to 20th	Night	14% 13% 37% 26% 9% 1	623
	21st to end	Night	12% 10% 40% 26% 10% 1	630
May	1st to 10th	Night	12% 8% 38% 31% 9% 1	630
	11th to 20th	Night	11% 8% 28% 35% 16% 2	621
	21st to end	Night	9% 4 26% 40% 20% 1	683
June	1st to 10th	Night	7% 1 14% 43% 32% 3	630
	11th to 20th	Night	3 2 16% 48% 28% 2	615
	21st to end	Night	4 2 11% 37% 39% 8%	600
July	1st to 10th	Night	3 2 7% 39% 43% 6%	585
	11th to 20th	Night	2 1 5% 38% 49% 6%	582
	21st to end	Night	3 1 5% 37% 47% 7%	657
August	1st to 10th	Night	3 1 4 37% 50% 6%	597
	11th to 20th	Night	6% 4 38% 45% 8%	594
	21st to end	Night	5% 1 5% 33% 47% 8%	660
September	1st to 10th	Night	10% 1 7% 31% 44% 6%	600
	11th to 20th	Night	12% 2 7% 32% 42% 5%	600
	21st to end	Night	7% 2 11% 40% 38% 4	600
October	1st to 10th	Night	5% 2 13% 46% 29% 4	725
	11th to 20th	Night	12% 4 23% 41% 17% 3	800
	21st to end	Night	15% 7% 28% 30% 18% 1	880
November	1st to 10th	Night	13% 4 26% 40% 16% 1	820
	11th to 20th	Night	11% 8% 31% 39% 11%	840
	21st to end	Night	17% 11% 31% 28% 11% 1	1013
December	1st to 10th	Night	17% 10% 32% 33% 7%	1050
	11th to 20th	Night	20% 11% 30% 33% 5%	1050
	21st to end	Night	19% 11% 32% 32% 5%	1155

Page generated at 2026-06-13 01:31:39. Version ac07

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