Weatherford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Weatherford clear sky chart from 2005-11-06 to 2025-12-03.

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	8% 5% 2 5% 3 3 4 3 5% 7% 55%	126919
	Night	7% 5% 2 4 3 3 3 3 5% 7% 58%	124071
Transparency	Day	29% 4 9% 24% 25% 9%	130675
	Night	26% 4 9% 24% 26% 10%	128378
Seeing	Day	11% 10% 29% 31% 16% 3	16820
	Night	10% 10% 34% 34% 11% 1	26714

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	8% 7% 2 8% 4 4 4 3 5% 5% 50%	4077
	11th to 20th	Day	5% 5% 2 4 2 3 3 2 4 4 67%	4080
	21st to end	Day	11% 9% 3 6% 3 2 2 2 3 5% 54%	4488
February	1st to 10th	Day	9% 9% 3 5% 3 3 3 3 4 5% 53%	1978
	11th to 20th	Day	9% 6% 2 6% 4 3 4 2 4 6% 55%	1949
	21st to end	Day	8% 8% 2 5% 3 3 3 3 3 5% 57%	1650
March	1st to 10th	Day	10% 5% 1 5% 3 3 3 2 3 5% 60%	4676
	11th to 20th	Day	6% 6% 2 5% 3 3 3 3 5% 6% 57%	4980
	21st to end	Day	7% 7% 2 7% 4 4 4 3 5% 7% 49%	5462
April	1st to 10th	Day	9% 5% 1 5% 3 2 3 3 5% 8% 55%	2210
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 6% 49%	2404
	21st to end	Day	13% 5% 2 4 3 4 4 3 5% 7% 51%	2600
May	1st to 10th	Day	16% 7% 2 6% 4 4 4 4 5% 6% 43%	5862
	11th to 20th	Day	9% 4 2 5% 3 4 3 3 4 7% 57%	5862
	21st to end	Day	11% 6% 2 6% 4 4 4 3 5% 6% 49%	6434
June	1st to 10th	Day	6% 4 2 4 4 4 5% 4 6% 10% 51%	2600
	11th to 20th	Day	6% 5% 1 4 4 3 4 4 5% 8% 58%	2600
	21st to end	Day	5% 3 1 4 3 4 3 4 6% 9% 59%	2600
July	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 5% 6% 9% 42%	5900
	11th to 20th	Day	4 4 1 5% 3 4 4 3 6% 8% 56%	5900
	21st to end	Day	2 2 1 3 3 3 4 3 6% 9% 64%	6422
August	1st to 10th	Day	6% 3 2 5% 3 3 5% 4 7% 9% 55%	4234
	11th to 20th	Day	5% 3 2 4 4 4 4 4 6% 7% 58%	4110
	21st to end	Day	3 3 1 4 3 3 4 3 5% 7% 63%	4312
September	1st to 10th	Day	8% 5% 2 4 3 3 4 3 4 6% 58%	2211
	11th to 20th	Day	9% 5% 2 4 4 5% 4 3 6% 7% 51%	2200
	21st to end	Day	7% 3 1 4 3 4 4 3 4 7% 60%	2200
October	1st to 10th	Day	8% 4 2 4 3 3 3 2 4 5% 62%	2200
	11th to 20th	Day	9% 3 2 3 2 2 2 2 2 4 68%	2033
	21st to end	Day	10% 4 2 4 3 2 3 2 4 5% 61%	2200
November	1st to 10th	Day	7% 3 1 3 2 3 2 3 4 5% 66%	1868
	11th to 20th	Day	6% 4 2 4 2 2 2 3 4 6% 66%	1890
	21st to end	Day	10% 4 2 4 2 3 3 2 4 5% 60%	1890
December	1st to 10th	Day	4 4 2 5% 4 2 3 3 4 7% 62%	2958
	11th to 20th	Day	6% 5% 1 4 2 2 3 3 5% 6% 63%	3391
	21st to end	Day	11% 11% 4 8% 4 3 4 3 5% 4 45%	4488
January	1st to 10th	Night	9% 6% 2 6% 4 4 4 3 6% 6% 50%	5888
	11th to 20th	Night	3 3 1 3 3 3 4 3 5% 7% 65%	5900
	21st to end	Night	11% 9% 3 5% 3 3 3 2 4 4 53%	6490
February	1st to 10th	Night	10% 8% 3 6% 4 3 3 2 4 4 55%	2440
	11th to 20th	Night	10% 6% 2 5% 3 4 3 3 4 6% 53%	2338
	21st to end	Night	9% 6% 1 4 3 3 3 4 4 6% 55%	1980
March	1st to 10th	Night	5% 5% 2 5% 3 3 3 3 4 6% 61%	5175
	11th to 20th	Night	6% 3 1 3 2 3 3 2 4 5% 66%	4980
	21st to end	Night	6% 6% 2 6% 4 4 4 4 6% 9% 50%	5467
April	1st to 10th	Night	8% 5% 1 3 3 3 3 3 5% 7% 58%	2185
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 5% 7% 53%	1946
	21st to end	Night	13% 5% 1 4 3 4 2 3 5% 7% 53%	1800
May	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 4 5% 48%	4053
	11th to 20th	Night	7% 4 1 4 3 3 4 4 6% 8% 55%	4053
	21st to end	Night	10% 6% 2 4 3 3 3 3 5% 7% 55%	4443
June	1st to 10th	Night	5% 3 1 5% 3 4 5% 4 6% 11% 55%	1800
	11th to 20th	Night	5% 3 1 4 3 3 4 2 7% 11% 58%	1800
	21st to end	Night	4 2 1 3 2 3 4 3 7% 9% 63%	1800
July	1st to 10th	Night	5% 5% 2 6% 4 4 6% 5% 7% 9% 47%	4078
	11th to 20th	Night	4 2 1 3 3 3 4 4 7% 12% 57%	4077
	21st to end	Night	2 2 1 4 3 3 3 4 7% 9% 62%	4449
August	1st to 10th	Night	2 1 1 3 3 4 4 4 6% 10% 63%	2926
	11th to 20th	Night	5% 3 1 4 3 4 4 4 7% 11% 54%	2944
	21st to end	Night	3 2 1 4 3 3 3 3 5% 8% 64%	3597
September	1st to 10th	Night	6% 4 2 3 3 4 3 3 4 7% 60%	2187
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 5% 6% 53%	2200
	21st to end	Night	6% 5% 1 4 2 3 3 3 4 7% 60%	2200
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 6% 7% 61%	2200
	11th to 20th	Night	8% 4 2 3 3 2 2 2 3 4 67%	2345
	21st to end	Night	9% 4 2 4 2 2 2 2 3 4 65%	2640
November	1st to 10th	Night	8% 4 1 3 2 3 2 3 3 6% 66%	2647
	11th to 20th	Night	5% 4 2 3 3 3 2 2 4 5% 67%	2730
	21st to end	Night	9% 5% 1 4 3 2 3 3 4 6% 60%	2730
December	1st to 10th	Night	5% 3 2 4 3 2 3 3 3 6% 66%	4277
	11th to 20th	Night	5% 5% 2 5% 3 3 3 2 4 5% 63%	4816
	21st to end	Night	12% 9% 2 5% 3 3 3 2 4 5% 51%	6490

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	36% 3 9% 26% 22% 4	4078
	11th to 20th	Day	23% 2 8% 20% 37% 10%	4080
	21st to end	Day	37% 2 4 20% 29% 8%	4488
February	1st to 10th	Day	34% 3 7% 25% 24% 7%	1978
	11th to 20th	Day	32% 4 9% 24% 24% 7%	1959
	21st to end	Day	31% 3 6% 19% 28% 12%	1650
March	1st to 10th	Day	29% 3 6% 14% 24% 25%	4676
	11th to 20th	Day	28% 4 7% 17% 27% 17%	4980
	21st to end	Day	35% 4 10% 28% 20% 3	5464
April	1st to 10th	Day	29% 4 11% 25% 22% 10%	2210
	11th to 20th	Day	36% 5% 7% 21% 21% 10%	2404
	21st to end	Day	34% 5% 11% 25% 22% 4	2600
May	1st to 10th	Day	41% 6% 11% 18% 18% 6%	5900
	11th to 20th	Day	28% 5% 9% 24% 21% 12%	5866
	21st to end	Day	36% 6% 10% 21% 17% 10%	6447
June	1st to 10th	Day	27% 8% 17% 27% 15% 6%	2600
	11th to 20th	Day	24% 6% 12% 27% 24% 6%	2600
	21st to end	Day	22% 7% 14% 25% 26% 7%	2600
July	1st to 10th	Day	38% 7% 11% 21% 19% 5%	5836
	11th to 20th	Day	24% 5% 10% 31% 25% 5%	5831
	21st to end	Day	17% 5% 15% 36% 24% 3	6240
August	1st to 10th	Day	25% 5% 10% 25% 28% 8%	4220
	11th to 20th	Day	24% 6% 11% 30% 24% 5%	4149
	21st to end	Day	20% 6% 13% 34% 23% 5%	4311
September	1st to 10th	Day	27% 5% 10% 22% 24% 12%	2211
	11th to 20th	Day	31% 6% 10% 24% 24% 6%	2200
	21st to end	Day	25% 5% 8% 24% 30% 9%	2200
October	1st to 10th	Day	16% 3 6% 14% 43% 17%	3590
	11th to 20th	Day	18% 3 8% 22% 30% 19%	3286
	21st to end	Day	23% 3 5% 25% 33% 10%	3538
November	1st to 10th	Day	21% 4 7% 25% 31% 12%	1868
	11th to 20th	Day	21% 3 5% 28% 31% 11%	1890
	21st to end	Day	27% 3 6% 27% 26% 11%	1890
December	1st to 10th	Day	24% 3 7% 37% 25% 4	2958
	11th to 20th	Day	23% 3 7% 23% 34% 10%	3389
	21st to end	Day	42% 3 7% 24% 18% 6%	4488
January	1st to 10th	Night	34% 4 9% 29% 21% 3	5888
	11th to 20th	Night	19% 3 11% 21% 33% 13%	5900
	21st to end	Night	35% 2 5% 17% 31% 9%	6490
February	1st to 10th	Night	35% 3 7% 21% 26% 9%	2440
	11th to 20th	Night	33% 3 9% 22% 23% 10%	2338
	21st to end	Night	30% 3 5% 20% 26% 16%	1980
March	1st to 10th	Night	26% 3 5% 16% 25% 26%	5175
	11th to 20th	Night	20% 3 6% 20% 25% 25%	4980
	21st to end	Night	31% 4 12% 25% 24% 4	5467
April	1st to 10th	Night	25% 4 11% 21% 25% 13%	2185
	11th to 20th	Night	32% 4 8% 25% 20% 10%	1946
	21st to end	Night	30% 6% 12% 25% 22% 5%	1800
May	1st to 10th	Night	39% 5% 13% 16% 20% 7%	4080
	11th to 20th	Night	25% 6% 10% 21% 24% 13%	4054
	21st to end	Night	30% 6% 14% 19% 18% 14%	4452
June	1st to 10th	Night	23% 7% 17% 31% 18% 5%	1800
	11th to 20th	Night	21% 6% 14% 29% 25% 5%	1800
	21st to end	Night	17% 5% 13% 30% 24% 11%	1800
July	1st to 10th	Night	31% 7% 16% 27% 16% 3	4035
	11th to 20th	Night	19% 4 12% 34% 26% 6%	4026
	21st to end	Night	18% 5% 13% 34% 27% 3	4320
August	1st to 10th	Night	15% 5% 12% 28% 30% 8%	2916
	11th to 20th	Night	23% 5% 10% 31% 26% 5%	2971
	21st to end	Night	18% 5% 14% 35% 23% 5%	3597
September	1st to 10th	Night	25% 5% 10% 24% 25% 12%	2187
	11th to 20th	Night	32% 5% 8% 20% 25% 8%	2200
	21st to end	Night	23% 4 7% 24% 31% 11%	2200
October	1st to 10th	Night	17% 4 7% 15% 36% 21%	3590
	11th to 20th	Night	17% 4 6% 20% 35% 19%	3818
	21st to end	Night	18% 2 5% 27% 36% 12%	4252
November	1st to 10th	Night	22% 3 7% 23% 31% 14%	2647
	11th to 20th	Night	21% 3 6% 27% 32% 12%	2730
	21st to end	Night	26% 3 6% 24% 28% 12%	2730
December	1st to 10th	Night	21% 3 6% 38% 28% 5%	4277
	11th to 20th	Night	26% 2 5% 23% 34% 10%	4817
	21st to end	Night	36% 4 6% 24% 23% 7%	6490

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	13% 18% 36% 25% 7% 1	300
	11th to 20th	Day	14% 19% 36% 25% 5%	300
	21st to end	Day	11% 17% 43% 22% 7%	330
February	1st to 10th	Day	15% 17% 42% 21% 5%	300
	11th to 20th	Day	16% 23% 42% 16% 4	300
	21st to end	Day	18% 21% 37% 19% 5%	249
March	1st to 10th	Day	16% 22% 36% 23% 3	300
	11th to 20th	Day	20% 22% 37% 18% 2 1	300
	21st to end	Day	15% 18% 45% 18% 4	330
April	1st to 10th	Day	19% 21% 36% 20% 5%	310
	11th to 20th	Day	16% 25% 41% 15% 2	522
	21st to end	Day	16% 19% 35% 22% 6% 1	700
May	1st to 10th	Day	12% 13% 44% 23% 7% 1	703
	11th to 20th	Day	14% 10% 33% 30% 11% 2	725
	21st to end	Day	13% 10% 33% 29% 12% 2	789
June	1st to 10th	Day	7% 6% 27% 39% 18% 4	730
	11th to 20th	Day	7% 4 32% 40% 14% 2	730
	21st to end	Day	4 2 27% 42% 21% 4	730
July	1st to 10th	Day	7% 2 16% 35% 32% 9%	721
	11th to 20th	Day	3 2 15% 42% 32% 6%	718
	21st to end	Day	4 1 9% 40% 38% 8%	794
August	1st to 10th	Day	6% 2 13% 46% 28% 5%	726
	11th to 20th	Day	7% 2 14% 40% 33% 5%	680
	21st to end	Day	5% 1 11% 42% 34% 8%	583
September	1st to 10th	Day	8% 1 11% 40% 34% 6%	341
	11th to 20th	Day	6% 2 22% 42% 25% 4	330
	21st to end	Day	9% 5% 24% 34% 24% 5%	330
October	1st to 10th	Day	9% 5% 30% 32% 19% 5%	330
	11th to 20th	Day	10% 12% 35% 31% 12% 1	330
	21st to end	Day	19% 12% 31% 25% 9% 3	363
November	1st to 10th	Day	11% 12% 35% 34% 7% 2	330
	11th to 20th	Day	13% 12% 36% 27% 10% 2	330
	21st to end	Day	14% 17% 38% 22% 8% 2	330
December	1st to 10th	Day	8% 14% 45% 22% 9% 1	306
	11th to 20th	Day	12% 16% 40% 23% 8%	300
	21st to end	Day	18% 20% 38% 20% 4	330
January	1st to 10th	Night	10% 14% 38% 32% 7%	1000
	11th to 20th	Night	11% 15% 35% 33% 6%	1000
	21st to end	Night	10% 12% 40% 32% 6%	1100
February	1st to 10th	Night	16% 12% 40% 27% 5%	840
	11th to 20th	Night	15% 16% 39% 25% 5% 1	784
	21st to end	Night	15% 16% 42% 24% 3	660
March	1st to 10th	Night	8% 17% 41% 29% 5%	718
	11th to 20th	Night	16% 15% 40% 25% 4	600
	21st to end	Night	11% 18% 43% 22% 5%	660
April	1st to 10th	Night	11% 16% 46% 22% 5%	600
	11th to 20th	Night	14% 18% 45% 21% 2	593
	21st to end	Night	18% 13% 40% 24% 5%	600
May	1st to 10th	Night	13% 13% 45% 25% 5%	600
	11th to 20th	Night	11% 9% 38% 32% 10% 1	591
	21st to end	Night	10% 8% 38% 32% 12% 1	650
June	1st to 10th	Night	6% 6% 32% 40% 15% 1	600
	11th to 20th	Night	5% 4 40% 42% 9%	600
	21st to end	Night	5% 2 33% 45% 15% 1	600
July	1st to 10th	Night	6% 1 18% 47% 25% 2	585
	11th to 20th	Night	4 1 18% 52% 24% 2	582
	21st to end	Night	4 1 11% 54% 29% 2	657
August	1st to 10th	Night	3 1 18% 51% 25% 1	597
	11th to 20th	Night	5% 2 17% 48% 25% 2	594
	21st to end	Night	4 1 14% 46% 33% 2	660
September	1st to 10th	Night	7% 1 21% 45% 23% 3	600
	11th to 20th	Night	12% 3 24% 39% 22% 2	600
	21st to end	Night	8% 5% 27% 41% 18% 2	600
October	1st to 10th	Night	8% 5% 32% 39% 17% 1	600
	11th to 20th	Night	10% 8% 38% 34% 10%	745
	21st to end	Night	13% 11% 34% 30% 12%	880
November	1st to 10th	Night	10% 8% 39% 33% 9% 1	1007
	11th to 20th	Night	8% 12% 39% 33% 8% 1	1050
	21st to end	Night	12% 14% 32% 30% 10%	1050
December	1st to 10th	Night	9% 12% 37% 34% 7% 1	1011
	11th to 20th	Night	13% 12% 39% 29% 6%	1000
	21st to end	Night	13% 13% 37% 31% 6%	1100

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