Beaumont
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beaumont clear sky chart from 2005-11-06 to 2024-02-15.

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	13% 6% 3 6% 6% 4 6% 6% 6% 8% 38%	78827
	Night	13% 6% 2 5% 5% 3 4 4 5% 8% 46%	80306
Transparency	Day	42% 8% 12% 17% 15% 6%	78552
	Night	36% 7% 13% 19% 17% 8%	80101
Seeing	Day	13% 6% 17% 26% 24% 13%	13846
	Night	15% 5% 18% 32% 26% 4	23845

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	23% 8% 2 4 4 2 4 4 4 6% 39%	2847
	11th to 20th	Day	17% 6% 2 4 4 2 3 3 3 5% 51%	2850
	21st to end	Day	25% 7% 3 5% 4 2 4 4 5% 7% 33%	3135
February	1st to 10th	Day	23% 7% 3 6% 5% 3 3 4 5% 6% 35%	1710
	11th to 20th	Day	22% 9% 3 6% 4 2 4 4 5% 4 37%	1863
	21st to end	Day	23% 9% 4 5% 5% 3 3 4 3 5% 36%	1628
March	1st to 10th	Day	20% 8% 3 5% 5% 3 5% 4 4 7% 35%	1980
	11th to 20th	Day	17% 9% 3 7% 5% 3 4 4 5% 6% 37%	1980
	21st to end	Day	15% 6% 3 6% 6% 4 4 4 5% 6% 42%	2178
April	1st to 10th	Day	14% 8% 4 5% 6% 4 5% 5% 6% 7% 37%	2024
	11th to 20th	Day	17% 7% 3 6% 5% 4 4 4 6% 7% 37%	2134
	21st to end	Day	10% 6% 3 5% 7% 4 5% 6% 5% 7% 43%	2160
May	1st to 10th	Day	11% 6% 3 6% 6% 3 6% 6% 5% 9% 38%	2160
	11th to 20th	Day	10% 5% 2 5% 6% 4 5% 5% 7% 9% 41%	2203
	21st to end	Day	9% 6% 3 7% 8% 5% 8% 8% 7% 10% 31%	2531
June	1st to 10th	Day	6% 5% 3 7% 8% 5% 8% 7% 8% 9% 34%	2340
	11th to 20th	Day	5% 4 3 7% 7% 5% 8% 9% 9% 9% 35%	2340
	21st to end	Day	7% 5% 3 8% 9% 6% 9% 9% 10% 11% 24%	2340
July	1st to 10th	Day	9% 5% 3 7% 8% 6% 7% 8% 9% 12% 26%	2340
	11th to 20th	Day	8% 5% 3 6% 8% 5% 8% 8% 9% 11% 29%	2340
	21st to end	Day	6% 5% 3 6% 7% 5% 11% 9% 9% 11% 29%	2546
August	1st to 10th	Day	3 3 2 6% 7% 5% 8% 10% 10% 13% 34%	2324
	11th to 20th	Day	6% 4 2 6% 9% 5% 9% 7% 10% 10% 32%	2125
	21st to end	Day	10% 5% 3 7% 7% 5% 6% 8% 8% 9% 32%	2376
September	1st to 10th	Day	8% 6% 3 6% 8% 4 7% 7% 7% 10% 35%	2118
	11th to 20th	Day	14% 6% 2 7% 7% 4 7% 6% 5% 7% 34%	1980
	21st to end	Day	10% 5% 2 5% 6% 4 6% 5% 6% 8% 43%	1972
October	1st to 10th	Day	7% 4 2 5% 5% 2 6% 4 5% 8% 51%	1800
	11th to 20th	Day	10% 5% 3 4 5% 3 4 5% 5% 8% 49%	1800
	21st to end	Day	13% 5% 2 5% 4 2 4 2 5% 6% 52%	1980
November	1st to 10th	Day	11% 5% 2 4 5% 4 5% 5% 4 7% 47%	1858
	11th to 20th	Day	12% 5% 3 6% 5% 2 5% 4 4 6% 47%	1900
	21st to end	Day	17% 8% 3 5% 5% 3 3 4 4 6% 43%	1900
December	1st to 10th	Day	17% 6% 2 6% 5% 3 5% 4 5% 7% 40%	1769
	11th to 20th	Day	15% 8% 3 6% 6% 3 5% 4 4 5% 40%	2161
	21st to end	Day	18% 6% 3 4 5% 3 4 4 5% 6% 43%	3135
January	1st to 10th	Night	18% 8% 3 5% 4 2 3 4 4 6% 42%	4108
	11th to 20th	Night	19% 6% 2 5% 4 2 3 3 3 5% 49%	4120
	21st to end	Night	24% 8% 3 6% 5% 2 3 3 4 7% 34%	4532
February	1st to 10th	Night	18% 8% 3 6% 5% 3 4 4 4 6% 39%	2470
	11th to 20th	Night	22% 8% 3 4 4 2 3 3 3 6% 42%	2091
	21st to end	Night	23% 8% 3 6% 5% 3 3 3 5% 5% 36%	1628
March	1st to 10th	Night	19% 10% 2 5% 4 3 4 4 4 6% 40%	1980
	11th to 20th	Night	17% 8% 3 5% 6% 3 4 4 5% 7% 39%	1980
	21st to end	Night	16% 6% 3 4 4 2 3 4 5% 7% 47%	2178
April	1st to 10th	Night	15% 6% 3 5% 5% 3 4 5% 5% 8% 40%	1936
	11th to 20th	Night	17% 5% 2 4 3 3 3 4 6% 9% 43%	1775
	21st to end	Night	12% 6% 3 5% 5% 3 4 5% 4 7% 45%	1800
May	1st to 10th	Night	13% 6% 2 5% 5% 3 5% 5% 6% 9% 41%	1800
	11th to 20th	Night	9% 5% 3 3 5% 3 5% 4 6% 8% 49%	1686
	21st to end	Night	7% 4 2 5% 4 3 4 6% 8% 10% 48%	1745
June	1st to 10th	Night	5% 3 2 4 4 3 4 5% 7% 10% 54%	1620
	11th to 20th	Night	5% 3 2 3 4 2 4 5% 7% 13% 53%	1620
	21st to end	Night	7% 4 2 5% 5% 4 5% 7% 7% 11% 42%	1620
July	1st to 10th	Night	6% 4 3 5% 5% 4 4 5% 7% 12% 44%	1620
	11th to 20th	Night	4 3 2 4 4 3 4 5% 7% 12% 53%	1620
	21st to end	Night	4 3 2 4 5% 3 5% 6% 8% 12% 49%	1772
August	1st to 10th	Night	2 1 1 2 3 3 2 5% 7% 12% 62%	1614
	11th to 20th	Night	4 2 1 4 5% 3 5% 7% 7% 12% 49%	1776
	21st to end	Night	8% 4 2 5% 6% 3 6% 6% 7% 11% 44%	1980
September	1st to 10th	Night	6% 5% 2 5% 5% 3 4 5% 8% 11% 47%	1836
	11th to 20th	Night	11% 6% 2 6% 6% 3 5% 5% 6% 7% 43%	1980
	21st to end	Night	8% 4 2 5% 4 2 3 4 5% 6% 56%	1980
October	1st to 10th	Night	6% 3 1 4 4 3 3 4 5% 8% 58%	2148
	11th to 20th	Night	10% 4 1 3 4 3 3 4 5% 7% 56%	2160
	21st to end	Night	11% 5% 2 4 3 2 3 2 3 5% 61%	2376
November	1st to 10th	Night	9% 5% 2 4 4 2 4 4 4 7% 54%	2220
	11th to 20th	Night	12% 5% 2 4 4 2 3 3 5% 6% 53%	2280
	21st to end	Night	14% 6% 3 6% 6% 3 3 4 4 6% 46%	2280
December	1st to 10th	Night	18% 7% 3 5% 4 3 4 4 4 7% 43%	2407
	11th to 20th	Night	16% 9% 3 5% 5% 3 3 4 5% 5% 42%	3036
	21st to end	Night	18% 8% 2 5% 5% 3 3 4 5% 5% 42%	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	47% 4 5% 15% 19% 9%	2848
	11th to 20th	Day	36% 5% 6% 17% 26% 9%	2850
	21st to end	Day	51% 4 5% 15% 16% 9%	3135
February	1st to 10th	Day	51% 4 6% 13% 16% 9%	1710
	11th to 20th	Day	49% 5% 8% 12% 17% 9%	1873
	21st to end	Day	51% 5% 8% 13% 15% 8%	1628
March	1st to 10th	Day	49% 5% 9% 14% 17% 7%	1980
	11th to 20th	Day	46% 5% 9% 11% 20% 8%	1980
	21st to end	Day	42% 5% 9% 16% 22% 6%	2178
April	1st to 10th	Day	45% 7% 9% 15% 15% 8%	2024
	11th to 20th	Day	45% 7% 10% 15% 14% 10%	2134
	21st to end	Day	38% 8% 10% 16% 22% 6%	2160
May	1st to 10th	Day	42% 7% 12% 16% 16% 7%	2160
	11th to 20th	Day	37% 8% 10% 26% 16% 3	2207
	21st to end	Day	42% 11% 15% 20% 11% 1	2531
June	1st to 10th	Day	38% 13% 16% 20% 13% 1	2340
	11th to 20th	Day	38% 11% 14% 23% 12% 2	2340
	21st to end	Day	47% 12% 17% 16% 7%	2340
July	1st to 10th	Day	43% 13% 22% 18% 4	2276
	11th to 20th	Day	42% 13% 22% 18% 5%	2271
	21st to end	Day	38% 16% 22% 20% 4 1	2405
August	1st to 10th	Day	32% 15% 20% 25% 8%	2310
	11th to 20th	Day	39% 14% 18% 22% 5% 1	2125
	21st to end	Day	43% 12% 18% 17% 7% 2	2376
September	1st to 10th	Day	41% 12% 15% 16% 13% 3	2118
	11th to 20th	Day	46% 9% 13% 14% 14% 4	1980
	21st to end	Day	37% 8% 13% 19% 14% 8%	1972
October	1st to 10th	Day	30% 7% 10% 20% 21% 11%	1800
	11th to 20th	Day	32% 7% 8% 17% 24% 13%	1800
	21st to end	Day	33% 5% 6% 14% 26% 16%	1980
November	1st to 10th	Day	35% 6% 10% 19% 20% 10%	1858
	11th to 20th	Day	35% 6% 9% 17% 21% 12%	1900
	21st to end	Day	43% 5% 7% 18% 19% 9%	1900
December	1st to 10th	Day	42% 6% 10% 19% 15% 8%	1769
	11th to 20th	Day	45% 5% 6% 15% 19% 9%	2159
	21st to end	Day	41% 4 7% 15% 24% 9%	3135
January	1st to 10th	Night	42% 6% 7% 17% 19% 10%	4108
	11th to 20th	Night	39% 4 5% 17% 25% 10%	4120
	21st to end	Night	50% 4 6% 15% 17% 9%	4532
February	1st to 10th	Night	47% 4 8% 11% 19% 11%	2470
	11th to 20th	Night	44% 5% 7% 16% 19% 10%	2091
	21st to end	Night	49% 6% 7% 13% 13% 12%	1628
March	1st to 10th	Night	45% 5% 9% 15% 17% 10%	1980
	11th to 20th	Night	45% 7% 10% 11% 19% 7%	1980
	21st to end	Night	37% 5% 13% 16% 21% 7%	2178
April	1st to 10th	Night	42% 6% 10% 18% 15% 9%	1936
	11th to 20th	Night	37% 6% 11% 18% 15% 13%	1775
	21st to end	Night	37% 6% 9% 21% 21% 6%	1800
May	1st to 10th	Night	38% 8% 13% 17% 17% 8%	1800
	11th to 20th	Night	32% 7% 12% 25% 20% 4	1687
	21st to end	Night	29% 9% 18% 29% 14% 2	1746
June	1st to 10th	Night	22% 10% 21% 32% 14%	1620
	11th to 20th	Night	23% 8% 20% 32% 14% 2	1620
	21st to end	Night	33% 11% 23% 24% 9%	1620
July	1st to 10th	Night	32% 9% 29% 26% 4	1575
	11th to 20th	Night	23% 10% 35% 25% 6%	1566
	21st to end	Night	24% 12% 31% 27% 6%	1673
August	1st to 10th	Night	14% 9% 33% 35% 8%	1604
	11th to 20th	Night	24% 13% 30% 27% 6%	1776
	21st to end	Night	32% 11% 25% 21% 9% 2	1980
September	1st to 10th	Night	29% 9% 22% 23% 13% 4	1836
	11th to 20th	Night	39% 8% 17% 17% 14% 5%	1980
	21st to end	Night	29% 6% 14% 23% 18% 11%	1980
October	1st to 10th	Night	25% 5% 11% 25% 20% 13%	2148
	11th to 20th	Night	26% 6% 9% 21% 23% 14%	2160
	21st to end	Night	28% 4 8% 16% 26% 18%	2376
November	1st to 10th	Night	29% 5% 12% 19% 23% 11%	2220
	11th to 20th	Night	33% 4 9% 19% 24% 11%	2280
	21st to end	Night	40% 4 9% 18% 18% 10%	2280
December	1st to 10th	Night	42% 5% 9% 20% 14% 9%	2407
	11th to 20th	Night	44% 4 6% 12% 20% 14%	3037
	21st to end	Night	43% 6% 8% 12% 23% 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	24% 9% 36% 20% 10% 1	270
	11th to 20th	Day	19% 13% 34% 23% 10%	270
	21st to end	Day	22% 12% 36% 22% 8%	297
February	1st to 10th	Day	26% 14% 35% 19% 7%	270
	11th to 20th	Day	31% 13% 27% 25% 4	252
	21st to end	Day	27% 18% 37% 15% 4	198
March	1st to 10th	Day	24% 13% 35% 21% 6%	240
	11th to 20th	Day	16% 14% 44% 17% 8% 2	240
	21st to end	Day	22% 13% 33% 24% 8% 1	264
April	1st to 10th	Day	17% 13% 30% 29% 11% 1	284
	11th to 20th	Day	25% 10% 24% 22% 16% 2	412
	21st to end	Day	15% 7% 30% 29% 17% 2	420
May	1st to 10th	Day	17% 7% 23% 32% 19% 2	423
	11th to 20th	Day	11% 3 19% 40% 22% 5%	526
	21st to end	Day	9% 4 19% 37% 24% 7%	679
June	1st to 10th	Day	8% 2 9% 33% 31% 17%	630
	11th to 20th	Day	7% 3 10% 33% 31% 14%	630
	21st to end	Day	10% 3 9% 23% 34% 21%	630
July	1st to 10th	Day	9% 2 4 24% 38% 24%	621
	11th to 20th	Day	7% 2 5% 21% 35% 30%	618
	21st to end	Day	6% 2 4 22% 37% 30%	684
August	1st to 10th	Day	4 1 2 22% 40% 31%	622
	11th to 20th	Day	5% 2 1 10% 44% 38%	439
	21st to end	Day	12% 3 3 16% 32% 35%	495
September	1st to 10th	Day	8% 2 3 18% 39% 29%	408
	11th to 20th	Day	13% 3 7% 20% 34% 23%	270
	21st to end	Day	13% 1 6% 25% 39% 16%	270
October	1st to 10th	Day	8% 2 11% 40% 28% 11%	270
	11th to 20th	Day	11% 4 16% 34% 23% 12%	270
	21st to end	Day	19% 7% 24% 26% 19% 5%	297
November	1st to 10th	Day	14% 4 19% 36% 24% 3	270
	11th to 20th	Day	17% 8% 23% 36% 13% 3	270
	21st to end	Day	21% 12% 31% 22% 12% 2	270
December	1st to 10th	Day	19% 7% 29% 29% 11% 6%	270
	11th to 20th	Day	18% 9% 37% 28% 8% 1	270
	21st to end	Day	20% 12% 35% 23% 8% 3	297
January	1st to 10th	Night	22% 6% 30% 33% 9%	950
	11th to 20th	Night	22% 6% 29% 33% 9%	950
	21st to end	Night	23% 6% 27% 37% 6%	1045
February	1st to 10th	Night	24% 8% 28% 34% 6%	950
	11th to 20th	Night	27% 8% 25% 30% 8%	659
	21st to end	Night	26% 7% 33% 31% 4	444
March	1st to 10th	Night	23% 6% 29% 35% 6%	540
	11th to 20th	Night	21% 6% 29% 35% 9%	540
	21st to end	Night	18% 8% 27% 35% 12%	594
April	1st to 10th	Night	18% 6% 29% 38% 9%	540
	11th to 20th	Night	20% 8% 23% 34% 15%	533
	21st to end	Night	15% 6% 26% 39% 13% 1	540
May	1st to 10th	Night	14% 5% 25% 44% 12%	540
	11th to 20th	Night	12% 4 19% 42% 23% 1	531
	21st to end	Night	6% 3 14% 41% 32% 3	584
June	1st to 10th	Night	6% 2 4 34% 49% 5%	540
	11th to 20th	Night	4 2 6% 36% 44% 8%	540
	21st to end	Night	8% 2 7% 23% 49% 11%	540
July	1st to 10th	Night	7% 2 2 22% 54% 13%	525
	11th to 20th	Night	3 1 2 20% 54% 20%	522
	21st to end	Night	4 1 3 21% 52% 18%	591
August	1st to 10th	Night	2 1 1 17% 63% 16%	537
	11th to 20th	Night	5% 1 1 14% 59% 20%	534
	21st to end	Night	8% 2 3 16% 54% 18%	594
September	1st to 10th	Night	6% 1 3 22% 52% 15%	540
	11th to 20th	Night	11% 2 3 21% 54% 9%	540
	21st to end	Night	11% 1 4 27% 48% 9%	540
October	1st to 10th	Night	7% 2 7% 31% 46% 6%	708
	11th to 20th	Night	10% 3 16% 37% 30% 4	720
	21st to end	Night	13% 5% 17% 37% 25% 3	792
November	1st to 10th	Night	11% 3 16% 39% 29% 2	740
	11th to 20th	Night	13% 6% 21% 40% 19%	760
	21st to end	Night	19% 4 27% 33% 16% 1	760
December	1st to 10th	Night	21% 6% 23% 35% 14% 1	887
	11th to 20th	Night	23% 6% 26% 34% 11%	950
	21st to end	Night	22% 7% 27% 34% 10%	1045

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