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 2024-11-10.

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%	101138
	Night	8% 5% 2 4 3 3 3 3 5% 7% 58%	98114
Transparency	Day	28% 5% 10% 24% 25% 8%	104933
	Night	26% 4 9% 24% 27% 10%	102446
Seeing	Day	10% 10% 29% 31% 16% 3	15390
	Night	10% 10% 34% 34% 11% 1	25269

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	6% 7% 2 7% 5% 4 4 3 5% 6% 52%	2847
	11th to 20th	Day	6% 5% 1 3 3 4 3 2 4 5% 63%	2850
	21st to end	Day	13% 9% 4 6% 3 2 2 2 4 5% 51%	3135
February	1st to 10th	Day	9% 9% 3 5% 3 3 3 3 4 4 53%	1879
	11th to 20th	Day	9% 6% 2 5% 4 3 4 2 4 6% 55%	1849
	21st to end	Day	8% 9% 2 5% 3 3 3 3 3 5% 55%	1570
March	1st to 10th	Day	9% 5% 1 4 3 3 3 2 3 6% 60%	3254
	11th to 20th	Day	8% 6% 2 5% 3 3 3 3 5% 5% 57%	3480
	21st to end	Day	10% 9% 3 8% 5% 4 4 4 5% 7% 42%	3814
April	1st to 10th	Day	8% 5% 1 5% 4 2 3 3 5% 8% 56%	2099
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 5% 6% 49%	2282
	21st to end	Day	13% 4 2 4 3 4 4 3 4 7% 51%	2470
May	1st to 10th	Day	16% 7% 2 6% 4 4 4 3 4 5% 45%	4082
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 5% 7% 52%	4082
	21st to end	Day	11% 5% 2 5% 4 5% 4 4 5% 6% 49%	4477
June	1st to 10th	Day	6% 4 2 4 4 4 4 4 6% 10% 52%	2470
	11th to 20th	Day	6% 4 1 4 4 3 4 4 5% 8% 58%	2470
	21st to end	Day	5% 3 1 4 3 3 3 4 6% 9% 59%	2470
July	1st to 10th	Day	8% 5% 2 5% 4 5% 4 4 6% 8% 49%	4120
	11th to 20th	Day	4 3 1 4 4 4 4 3 7% 8% 58%	4120
	21st to end	Day	3 3 1 4 3 3 4 3 6% 9% 61%	4465
August	1st to 10th	Day	5% 3 2 5% 3 3 5% 4 7% 9% 55%	4104
	11th to 20th	Day	5% 3 2 4 4 4 4 4 6% 7% 58%	3982
	21st to end	Day	3 3 1 4 3 3 4 3 5% 7% 64%	4180
September	1st to 10th	Day	8% 5% 2 4 3 3 3 3 4 6% 59%	2101
	11th to 20th	Day	9% 5% 2 4 4 4 4 3 5% 7% 52%	2090
	21st to end	Day	7% 3 1 4 3 4 3 3 4 6% 61%	2090
October	1st to 10th	Day	9% 4 2 4 3 3 3 2 4 5% 62%	2090
	11th to 20th	Day	9% 3 2 4 2 2 2 2 2 4 69%	1932
	21st to end	Day	10% 4 2 4 3 2 2 2 4 5% 62%	2090
November	1st to 10th	Day	8% 3 1 4 2 3 2 3 4 5% 64%	1768
	11th to 20th	Day	6% 4 2 4 2 2 2 3 3 5% 66%	1710
	21st to end	Day	10% 4 2 4 2 3 3 2 5% 5% 60%	1710
December	1st to 10th	Day	6% 5% 2 6% 4 3 3 3 4 7% 57%	1710
	11th to 20th	Day	9% 8% 2 5% 3 3 3 3 4 5% 55%	2161
	21st to end	Day	7% 9% 4 9% 5% 4 5% 3 5% 5% 45%	3135
January	1st to 10th	Night	8% 6% 3 6% 4 3 4 3 5% 5% 53%	4108
	11th to 20th	Night	5% 4 1 3 3 3 4 4 5% 7% 61%	4120
	21st to end	Night	13% 9% 3 5% 3 2 3 2 4 4 52%	4532
February	1st to 10th	Night	11% 8% 3 6% 4 3 3 2 3 4 54%	2318
	11th to 20th	Night	10% 6% 2 5% 3 4 3 2 4 6% 55%	2218
	21st to end	Night	9% 6% 1 4 3 4 3 4 4 6% 54%	1884
March	1st to 10th	Night	5% 4 3 5% 4 3 4 3 4 5% 60%	3591
	11th to 20th	Night	9% 4 1 4 3 3 3 3 4 5% 62%	3480
	21st to end	Night	7% 7% 2 6% 4 4 4 4 6% 8% 49%	3817
April	1st to 10th	Night	8% 5% 1 3 3 3 3 4 5% 7% 59%	2076
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 5% 7% 52%	1848
	21st to end	Night	13% 5% 1 4 3 3 2 3 5% 7% 54%	1710
May	1st to 10th	Night	17% 8% 2 5% 3 3 3 2 3 5% 51%	2823
	11th to 20th	Night	10% 5% 2 5% 4 3 5% 4 6% 8% 48%	2823
	21st to end	Night	8% 5% 2 4 3 3 2 3 5% 7% 59%	3090
June	1st to 10th	Night	5% 2 1 5% 3 3 5% 4 6% 11% 56%	1710
	11th to 20th	Night	5% 3 1 3 3 3 4 2 7% 11% 58%	1710
	21st to end	Night	5% 3 1 3 2 2 4 3 7% 9% 63%	1710
July	1st to 10th	Night	5% 4 2 4 3 3 5% 4 6% 9% 54%	2850
	11th to 20th	Night	3 2 1 3 3 3 4 4 6% 11% 60%	2850
	21st to end	Night	2 3 1 3 3 3 4 3 7% 9% 62%	3098
August	1st to 10th	Night	2 2 1 3 3 4 4 4 6% 10% 62%	2836
	11th to 20th	Night	5% 3 1 4 3 4 4 4 7% 11% 54%	2852
	21st to end	Night	2 2 1 4 3 3 3 3 5% 9% 65%	3487
September	1st to 10th	Night	6% 4 2 3 3 3 3 3 4 7% 60%	2077
	11th to 20th	Night	10% 6% 2 5% 3 3 4 3 4 7% 53%	2090
	21st to end	Night	7% 4 1 4 2 3 3 3 4 7% 61%	2090
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 6% 7% 60%	2090
	11th to 20th	Night	8% 4 2 3 3 2 2 2 3 4 67%	2228
	21st to end	Night	9% 4 2 3 2 2 2 2 3 4 66%	2508
November	1st to 10th	Night	8% 4 1 3 2 3 2 3 3 6% 65%	2512
	11th to 20th	Night	5% 4 2 3 3 3 2 2 4 5% 67%	2470
	21st to end	Night	9% 5% 1 4 3 3 3 3 4 6% 59%	2470
December	1st to 10th	Night	8% 4 2 4 3 3 4 3 4 5% 60%	2470
	11th to 20th	Night	8% 6% 2 6% 4 4 3 2 4 5% 55%	3036
	21st to end	Night	11% 6% 2 5% 4 3 4 3 5% 5% 51%	4532

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	34% 4 10% 22% 26% 5%	2848
	11th to 20th	Day	25% 3 11% 25% 32% 5%	2850
	21st to end	Day	39% 3 5% 24% 25% 4	3135
February	1st to 10th	Day	35% 3 7% 25% 24% 6%	1879
	11th to 20th	Day	31% 4 8% 24% 25% 8%	1859
	21st to end	Day	33% 3 6% 20% 27% 11%	1570
March	1st to 10th	Day	27% 4 8% 17% 27% 18%	3254
	11th to 20th	Day	29% 4 10% 24% 27% 6%	3480
	21st to end	Day	41% 5% 10% 22% 17% 5%	3814
April	1st to 10th	Day	28% 4 11% 25% 22% 10%	2099
	11th to 20th	Day	36% 5% 7% 21% 20% 10%	2282
	21st to end	Day	33% 5% 11% 25% 23% 4	2470
May	1st to 10th	Day	41% 6% 9% 16% 20% 8%	4120
	11th to 20th	Day	32% 7% 11% 28% 17% 5%	4086
	21st to end	Day	35% 7% 10% 18% 19% 11%	4489
June	1st to 10th	Day	26% 9% 18% 27% 15% 6%	2470
	11th to 20th	Day	24% 6% 12% 28% 24% 7%	2470
	21st to end	Day	22% 7% 13% 25% 26% 8%	2470
July	1st to 10th	Day	32% 6% 11% 26% 20% 5%	4056
	11th to 20th	Day	22% 5% 10% 33% 25% 5%	4051
	21st to end	Day	19% 5% 12% 32% 28% 3	4325
August	1st to 10th	Day	25% 5% 10% 25% 28% 8%	4090
	11th to 20th	Day	24% 6% 11% 29% 24% 6%	4021
	21st to end	Day	19% 6% 13% 34% 23% 5%	4179
September	1st to 10th	Day	27% 5% 10% 22% 24% 12%	2101
	11th to 20th	Day	31% 6% 10% 22% 24% 6%	2090
	21st to end	Day	25% 5% 8% 23% 31% 9%	2090
October	1st to 10th	Day	16% 3 6% 14% 42% 18%	3480
	11th to 20th	Day	18% 3 8% 21% 30% 19%	3185
	21st to end	Day	22% 3 5% 26% 33% 10%	3428
November	1st to 10th	Day	23% 4 7% 25% 30% 12%	1768
	11th to 20th	Day	21% 3 6% 29% 31% 11%	1710
	21st to end	Day	28% 3 6% 25% 26% 12%	1710
December	1st to 10th	Day	28% 4 10% 28% 25% 5%	1710
	11th to 20th	Day	32% 3 9% 19% 30% 7%	2159
	21st to end	Day	40% 4 9% 21% 22% 5%	3135
January	1st to 10th	Night	32% 5% 7% 25% 26% 5%	4108
	11th to 20th	Night	22% 4 15% 22% 28% 8%	4120
	21st to end	Night	36% 3 6% 20% 27% 7%	4532
February	1st to 10th	Night	35% 3 8% 21% 25% 8%	2318
	11th to 20th	Night	32% 3 8% 22% 24% 11%	2218
	21st to end	Night	30% 3 5% 20% 26% 15%	1884
March	1st to 10th	Night	26% 4 6% 18% 23% 22%	3591
	11th to 20th	Night	24% 4 8% 29% 27% 8%	3480
	21st to end	Night	32% 5% 11% 26% 21% 5%	3817
April	1st to 10th	Night	24% 4 11% 21% 25% 14%	2076
	11th to 20th	Night	32% 5% 8% 25% 20% 10%	1848
	21st to end	Night	30% 6% 11% 26% 22% 6%	1710
May	1st to 10th	Night	38% 5% 8% 17% 22% 10%	2850
	11th to 20th	Night	32% 8% 14% 25% 17% 3	2824
	21st to end	Night	26% 6% 13% 20% 20% 16%	3099
June	1st to 10th	Night	22% 7% 18% 32% 17% 5%	1710
	11th to 20th	Night	21% 6% 14% 28% 25% 6%	1710
	21st to end	Night	17% 5% 12% 30% 24% 11%	1710
July	1st to 10th	Night	26% 5% 14% 32% 20% 3	2805
	11th to 20th	Night	18% 4 10% 34% 28% 6%	2796
	21st to end	Night	18% 5% 13% 31% 30% 3	2999
August	1st to 10th	Night	15% 5% 12% 27% 31% 9%	2826
	11th to 20th	Night	23% 5% 10% 31% 26% 5%	2879
	21st to end	Night	17% 5% 14% 35% 23% 5%	3487
September	1st to 10th	Night	24% 5% 9% 24% 25% 12%	2077
	11th to 20th	Night	33% 5% 9% 19% 26% 9%	2090
	21st to end	Night	23% 4 7% 23% 31% 11%	2090
October	1st to 10th	Night	17% 4 8% 14% 36% 21%	3480
	11th to 20th	Night	17% 4 6% 20% 35% 19%	3701
	21st to end	Night	18% 2 5% 27% 36% 12%	4120
November	1st to 10th	Night	22% 3 7% 24% 30% 14%	2512
	11th to 20th	Night	21% 3 6% 26% 31% 12%	2470
	21st to end	Night	27% 3 6% 22% 28% 14%	2470
December	1st to 10th	Night	25% 4 9% 27% 27% 8%	2470
	11th to 20th	Night	32% 2 6% 21% 31% 8%	3037
	21st to end	Night	34% 5% 8% 21% 25% 8%	4532

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	12% 19% 35% 25% 7% 1	270
	11th to 20th	Day	15% 19% 36% 25% 5%	270
	21st to end	Day	11% 17% 44% 21% 7%	297
February	1st to 10th	Day	15% 18% 42% 21% 4	270
	11th to 20th	Day	14% 22% 43% 17% 4	270
	21st to end	Day	19% 22% 39% 16% 3	225
March	1st to 10th	Day	14% 21% 39% 22% 3	270
	11th to 20th	Day	19% 23% 36% 19% 3 1	270
	21st to end	Day	15% 20% 44% 17% 4	297
April	1st to 10th	Day	17% 21% 37% 20% 4	279
	11th to 20th	Day	16% 25% 41% 15% 2	480
	21st to end	Day	16% 20% 35% 22% 6% 1	650
May	1st to 10th	Day	12% 14% 45% 21% 6% 1	653
	11th to 20th	Day	14% 10% 32% 31% 11% 1	675
	21st to end	Day	13% 10% 33% 29% 13% 3	734
June	1st to 10th	Day	6% 5% 27% 39% 18% 4	680
	11th to 20th	Day	7% 4 33% 40% 13% 2	680
	21st to end	Day	4 3 27% 42% 21% 4	680
July	1st to 10th	Day	7% 2 16% 35% 32% 8%	671
	11th to 20th	Day	4 2 15% 41% 32% 6%	668
	21st to end	Day	4 1 8% 41% 37% 9%	739
August	1st to 10th	Day	6% 2 13% 45% 29% 5%	676
	11th to 20th	Day	7% 2 14% 40% 32% 5%	632
	21st to end	Day	4 11% 43% 34% 8%	539
September	1st to 10th	Day	8% 1 11% 38% 35% 7%	311
	11th to 20th	Day	7% 2 21% 41% 24% 5%	300
	21st to end	Day	10% 5% 24% 33% 23% 6%	300
October	1st to 10th	Day	10% 6% 31% 30% 18% 5%	300
	11th to 20th	Day	10% 13% 34% 31% 11% 1	300
	21st to end	Day	18% 13% 31% 25% 9% 4	330
November	1st to 10th	Day	12% 10% 36% 34% 6% 2	297
	11th to 20th	Day	13% 13% 38% 24% 11% 1	270
	21st to end	Day	16% 17% 36% 22% 9% 1	270
December	1st to 10th	Day	9% 14% 45% 21% 10% 1	270
	11th to 20th	Day	13% 17% 38% 23% 9%	270
	21st to end	Day	16% 21% 39% 20% 4	297
January	1st to 10th	Night	9% 14% 37% 33% 7%	950
	11th to 20th	Night	11% 15% 35% 33% 6%	950
	21st to end	Night	10% 12% 38% 33% 6%	1045
February	1st to 10th	Night	17% 12% 39% 27% 5%	798
	11th to 20th	Night	14% 16% 39% 26% 5% 1	744
	21st to end	Night	15% 17% 42% 23% 3	628
March	1st to 10th	Night	7% 17% 41% 30% 5%	682
	11th to 20th	Night	16% 15% 39% 26% 5%	570
	21st to end	Night	11% 19% 43% 22% 5%	627
April	1st to 10th	Night	11% 16% 47% 21% 5%	570
	11th to 20th	Night	14% 18% 45% 21% 2	563
	21st to end	Night	17% 13% 40% 24% 5%	570
May	1st to 10th	Night	12% 14% 46% 23% 5%	570
	11th to 20th	Night	11% 8% 39% 32% 10% 1	561
	21st to end	Night	9% 8% 37% 32% 12% 1	617
June	1st to 10th	Night	6% 5% 32% 40% 15% 1	570
	11th to 20th	Night	5% 4 40% 42% 9%	570
	21st to end	Night	5% 2 32% 45% 16% 1	570
July	1st to 10th	Night	5% 1 19% 47% 25% 3	555
	11th to 20th	Night	4 1 18% 51% 24% 2	552
	21st to end	Night	4 1 11% 54% 30% 2	624
August	1st to 10th	Night	2 1 17% 51% 27% 1	567
	11th to 20th	Night	5% 2 18% 49% 25% 2	564
	21st to end	Night	3 1 14% 46% 33% 2	627
September	1st to 10th	Night	7% 1 20% 45% 24% 3	570
	11th to 20th	Night	12% 3 24% 38% 22% 2	570
	21st to end	Night	8% 4 27% 41% 18% 2	570
October	1st to 10th	Night	9% 5% 31% 38% 17% 1	570
	11th to 20th	Night	10% 8% 38% 35% 9%	708
	21st to end	Night	12% 10% 35% 30% 12%	836
November	1st to 10th	Night	11% 8% 38% 33% 10% 1	956
	11th to 20th	Night	8% 12% 39% 31% 8% 1	950
	21st to end	Night	13% 14% 32% 31% 10%	950
December	1st to 10th	Night	10% 12% 37% 33% 7% 1	950
	11th to 20th	Night	13% 12% 39% 29% 6%	950
	21st to end	Night	12% 13% 38% 31% 6%	1045

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