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 2026-07-31.

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 7% 5% 5% 5% 4 6% 8% 38%	137751
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 43%	135538
Transparency	Day	41% 7% 12% 18% 15% 6%	141358
	Night	38% 6% 12% 19% 17% 8%	140011
Seeing	Day	14% 7% 19% 26% 23% 12%	17206
	Night	15% 5% 19% 32% 25% 4	26949

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	18% 9% 3 6% 4 4 3 3 4 5% 41%	5289
	11th to 20th	Day	12% 5% 2 6% 4 4 4 3 4 5% 51%	5310
	21st to end	Day	27% 8% 3 8% 4 3 3 2 4 6% 32%	5812
February	1st to 10th	Day	21% 7% 3 6% 4 4 4 3 5% 6% 37%	1890
	11th to 20th	Day	21% 9% 2 7% 4 4 3 3 5% 5% 36%	2140
	21st to end	Day	21% 10% 3 6% 4 4 3 3 3 5% 38%	1903
March	1st to 10th	Day	21% 8% 3 7% 4 5% 5% 4 5% 6% 33%	5046
	11th to 20th	Day	14% 7% 2 7% 4 4 4 3 5% 6% 44%	5090
	21st to end	Day	18% 7% 3 6% 5% 4 4 3 4 6% 38%	5583
April	1st to 10th	Day	14% 9% 3 7% 5% 5% 5% 4 6% 7% 36%	2362
	11th to 20th	Day	16% 7% 3 7% 5% 5% 4 4 6% 7% 37%	2494
	21st to end	Day	10% 7% 2 6% 6% 5% 6% 5% 5% 7% 40%	2520
May	1st to 10th	Day	20% 8% 3 8% 6% 6% 5% 4 6% 7% 27%	7021
	11th to 20th	Day	10% 6% 3 8% 5% 5% 5% 3 6% 8% 40%	7320
	21st to end	Day	9% 6% 3 9% 6% 7% 7% 6% 9% 10% 29%	8392
June	1st to 10th	Day	6% 6% 3 9% 7% 7% 8% 5% 8% 9% 33%	2730
	11th to 20th	Day	5% 5% 2 7% 7% 6% 8% 7% 8% 10% 33%	2730
	21st to end	Day	7% 5% 2 8% 7% 7% 8% 7% 10% 10% 28%	2730
July	1st to 10th	Day	7% 5% 3 8% 7% 7% 8% 7% 9% 12% 27%	6030
	11th to 20th	Day	7% 7% 3 10% 7% 7% 7% 6% 9% 12% 27%	6030
	21st to end	Day	10% 7% 3 7% 6% 6% 6% 5% 8% 10% 32%	6553
August	1st to 10th	Day	2 2 1 4 4 5% 6% 5% 8% 10% 53%	4216
	11th to 20th	Day	3 3 1 5% 5% 5% 6% 5% 10% 13% 44%	3849
	21st to end	Day	9% 6% 3 8% 7% 6% 7% 5% 7% 8% 34%	4312
September	1st to 10th	Day	9% 7% 2 7% 6% 6% 6% 5% 7% 9% 35%	2352
	11th to 20th	Day	13% 6% 2 8% 5% 5% 7% 5% 6% 8% 36%	2200
	21st to end	Day	9% 5% 2 5% 5% 5% 5% 4 6% 8% 45%	2190
October	1st to 10th	Day	7% 4 2 5% 4 4 5% 3 5% 7% 54%	2000
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 5% 8% 53%	2000
	21st to end	Day	12% 5% 2 6% 3 3 3 2 5% 6% 53%	2200
November	1st to 10th	Day	12% 6% 2 5% 4 5% 5% 4 4 7% 47%	2058
	11th to 20th	Day	11% 5% 3 6% 4 4 4 3 5% 6% 48%	2100
	21st to end	Day	16% 8% 2 6% 4 4 3 3 4 6% 43%	2100
December	1st to 10th	Day	22% 8% 2 6% 3 3 3 3 4 6% 38%	3131
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 3 5% 6% 41%	3481
	21st to end	Day	17% 7% 2 5% 3 3 4 3 5% 5% 46%	4587
January	1st to 10th	Night	16% 7% 3 5% 3 3 4 3 4 6% 46%	7634
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 5% 48%	7680
	21st to end	Night	28% 9% 2 7% 4 3 3 3 4 6% 32%	8402
February	1st to 10th	Night	18% 9% 3 7% 4 4 3 3 4 5% 41%	2730
	11th to 20th	Night	22% 8% 3 5% 3 3 3 2 3 6% 41%	2382
	21st to end	Night	22% 9% 2 7% 4 3 3 3 4 5% 39%	1903
March	1st to 10th	Night	22% 11% 3 6% 4 3 4 3 3 5% 36%	5029
	11th to 20th	Night	21% 7% 3 6% 4 3 3 2 3 5% 42%	5090
	21st to end	Night	19% 9% 3 6% 4 4 3 3 4 5% 42%	5588
April	1st to 10th	Night	17% 7% 3 6% 5% 4 4 4 5% 7% 38%	2257
	11th to 20th	Night	17% 6% 2 4 3 4 3 3 6% 9% 43%	2075
	21st to end	Night	14% 7% 2 6% 5% 4 4 4 4 7% 43%	2100
May	1st to 10th	Night	26% 10% 3 8% 5% 4 4 4 5% 7% 25%	5832
	11th to 20th	Night	16% 7% 3 7% 4 4 4 4 5% 7% 39%	5551
	21st to end	Night	15% 8% 3 8% 5% 5% 5% 4 8% 10% 30%	5793
June	1st to 10th	Night	6% 4 2 4 4 3 4 4 7% 10% 52%	1890
	11th to 20th	Night	5% 4 2 4 4 3 4 4 7% 12% 51%	1890
	21st to end	Night	6% 4 2 6% 5% 4 5% 5% 7% 11% 44%	1890
July	1st to 10th	Night	5% 5% 2 6% 4 4 5% 4 7% 14% 44%	4168
	11th to 20th	Night	3 4 2 6% 5% 5% 5% 5% 7% 11% 45%	4167
	21st to end	Night	6% 5% 3 7% 6% 5% 5% 4 7% 9% 44%	4539
August	1st to 10th	Night	2 2 1 3 3 3 3 3 6% 10% 65%	2942
	11th to 20th	Night	2 1 1 3 2 3 4 5% 7% 12% 61%	3200
	21st to end	Night	6% 4 2 6% 5% 5% 6% 5% 9% 10% 43%	3586
September	1st to 10th	Night	6% 5% 1 5% 4 4 5% 4 8% 11% 45%	2041
	11th to 20th	Night	11% 6% 2 7% 5% 4 5% 4 6% 7% 44%	2200
	21st to end	Night	7% 4 2 6% 4 3 3 3 5% 6% 57%	2200
October	1st to 10th	Night	6% 3 1 5% 3 4 3 3 5% 7% 60%	2388
	11th to 20th	Night	8% 4 1 4 3 3 3 3 5% 7% 60%	2400
	21st to end	Night	11% 5% 2 4 3 2 3 1 3 5% 62%	2640
November	1st to 10th	Night	10% 6% 2 6% 3 3 4 4 4 7% 53%	2460
	11th to 20th	Night	11% 5% 2 4 3 3 3 2 5% 6% 55%	2520
	21st to end	Night	14% 6% 2 7% 5% 4 3 3 4 6% 46%	2520
December	1st to 10th	Night	22% 9% 4 7% 5% 4 3 3 4 5% 35%	4272
	11th to 20th	Night	14% 10% 3 7% 4 3 3 3 5% 5% 43%	4946
	21st to end	Night	16% 8% 2 6% 4 3 3 3 4 5% 45%	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	45% 4 6% 21% 17% 7%	5290
	11th to 20th	Day	35% 4 6% 16% 25% 13%	5310
	21st to end	Day	54% 3 5% 12% 15% 10%	5812
February	1st to 10th	Day	49% 4 7% 13% 17% 9%	1890
	11th to 20th	Day	49% 5% 8% 14% 16% 9%	2150
	21st to end	Day	50% 5% 8% 13% 17% 8%	1903
March	1st to 10th	Day	50% 5% 8% 10% 16% 10%	5046
	11th to 20th	Day	40% 6% 8% 11% 20% 15%	5090
	21st to end	Day	46% 6% 8% 19% 18% 3	5585
April	1st to 10th	Day	46% 7% 9% 14% 15% 9%	2362
	11th to 20th	Day	44% 7% 10% 15% 14% 9%	2494
	21st to end	Day	40% 8% 11% 16% 20% 5%	2520
May	1st to 10th	Day	53% 7% 9% 18% 11% 2	7056
	11th to 20th	Day	40% 6% 12% 22% 17% 2	7324
	21st to end	Day	42% 10% 18% 22% 7% 1	8405
June	1st to 10th	Day	39% 13% 15% 19% 13% 1	2730
	11th to 20th	Day	38% 11% 14% 23% 12% 2	2730
	21st to end	Day	43% 11% 18% 20% 8%	2730
July	1st to 10th	Day	41% 12% 27% 18% 2	5966
	11th to 20th	Day	45% 11% 25% 16% 2	5961
	21st to end	Day	43% 11% 18% 24% 4	6371
August	1st to 10th	Day	21% 10% 14% 36% 18%	4202
	11th to 20th	Day	26% 11% 31% 28% 3	3885
	21st to end	Day	44% 10% 14% 17% 14% 1	4311
September	1st to 10th	Day	41% 11% 15% 15% 14% 3	2352
	11th to 20th	Day	44% 9% 13% 16% 14% 4	2200
	21st to end	Day	35% 8% 13% 20% 14% 10%	2190
October	1st to 10th	Day	22% 5% 6% 13% 18% 36%	3260
	11th to 20th	Day	20% 4 5% 18% 35% 18%	3240
	21st to end	Day	26% 4 5% 12% 42% 12%	3538
November	1st to 10th	Day	36% 6% 10% 19% 19% 11%	2058
	11th to 20th	Day	34% 6% 9% 17% 21% 13%	2100
	21st to end	Day	42% 5% 7% 19% 19% 8%	2100
December	1st to 10th	Day	47% 4 6% 16% 21% 5%	3131
	11th to 20th	Day	43% 5% 7% 14% 20% 11%	3479
	21st to end	Day	40% 4 6% 16% 24% 10%	4587
January	1st to 10th	Night	39% 5% 11% 19% 20% 7%	7635
	11th to 20th	Night	39% 3 4 17% 24% 13%	7680
	21st to end	Night	55% 4 5% 12% 16% 8%	8402
February	1st to 10th	Night	45% 4 8% 11% 20% 12%	2730
	11th to 20th	Night	45% 5% 7% 15% 18% 9%	2382
	21st to end	Night	47% 6% 8% 14% 15% 12%	1903
March	1st to 10th	Night	50% 5% 6% 13% 16% 10%	5029
	11th to 20th	Night	46% 6% 6% 12% 14% 16%	5090
	21st to end	Night	45% 5% 9% 15% 20% 7%	5588
April	1st to 10th	Night	44% 6% 9% 16% 15% 9%	2257
	11th to 20th	Night	37% 5% 12% 19% 15% 12%	2075
	21st to end	Night	39% 6% 10% 20% 19% 5%	2100
May	1st to 10th	Night	56% 7% 11% 14% 10% 2	5862
	11th to 20th	Night	42% 7% 11% 19% 17% 3	5552
	21st to end	Night	45% 10% 19% 19% 6% 1	5805
June	1st to 10th	Night	24% 10% 21% 31% 14%	1890
	11th to 20th	Night	25% 8% 21% 31% 13% 2	1890
	21st to end	Night	31% 10% 24% 26% 9%	1890
July	1st to 10th	Night	31% 7% 39% 21% 2	4125
	11th to 20th	Night	31% 9% 34% 23% 3	4116
	21st to end	Night	36% 10% 19% 29% 6%	4410
August	1st to 10th	Night	14% 6% 20% 42% 18%	2932
	11th to 20th	Night	15% 8% 38% 34% 5%	3230
	21st to end	Night	33% 13% 20% 20% 12% 1	3586
September	1st to 10th	Night	31% 9% 21% 21% 14% 4	2041
	11th to 20th	Night	37% 8% 17% 20% 15% 5%	2200
	21st to end	Night	28% 6% 14% 23% 18% 12%	2200
October	1st to 10th	Night	18% 4 7% 16% 18% 36%	3908
	11th to 20th	Night	15% 4 6% 25% 29% 21%	3899
	21st to end	Night	21% 3 5% 13% 40% 17%	4252
November	1st to 10th	Night	31% 5% 11% 19% 23% 11%	2460
	11th to 20th	Night	31% 4 9% 19% 24% 13%	2520
	21st to end	Night	40% 4 9% 18% 18% 10%	2520
December	1st to 10th	Night	52% 4 6% 16% 16% 6%	4272
	11th to 20th	Night	44% 4 7% 12% 20% 12%	4947
	21st to end	Night	41% 5% 6% 15% 24% 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	23% 10% 38% 18% 9% 1	330
	11th to 20th	Day	19% 14% 35% 22% 9% 1	330
	21st to end	Day	24% 15% 33% 21% 7%	363
February	1st to 10th	Day	23% 14% 37% 21% 6%	330
	11th to 20th	Day	30% 15% 27% 24% 4	330
	21st to end	Day	25% 21% 37% 13% 3 1	273
March	1st to 10th	Day	25% 14% 32% 23% 6%	330
	11th to 20th	Day	16% 17% 44% 15% 7% 1	330
	21st to end	Day	21% 12% 33% 24% 9% 1	363
April	1st to 10th	Day	19% 14% 30% 27% 9% 1	382
	11th to 20th	Day	22% 13% 27% 23% 14% 1	532
	21st to end	Day	16% 9% 31% 27% 15% 2	540
May	1st to 10th	Day	20% 8% 26% 28% 16% 2	543
	11th to 20th	Day	14% 6% 21% 35% 19% 5%	661
	21st to end	Day	9% 5% 24% 35% 21% 6%	844
June	1st to 10th	Day	8% 2 13% 33% 28% 15%	780
	11th to 20th	Day	8% 4 12% 34% 30% 13%	780
	21st to end	Day	9% 3 9% 26% 33% 20%	780
July	1st to 10th	Day	9% 3 4 23% 38% 24%	771
	11th to 20th	Day	9% 2 5% 23% 33% 28%	768
	21st to end	Day	7% 2 4 23% 37% 27%	845
August	1st to 10th	Day	3 1 2 21% 42% 30%	721
	11th to 20th	Day	4 2 1 11% 43% 39%	519
	21st to end	Day	12% 4 3 17% 33% 31%	583
September	1st to 10th	Day	11% 3 5% 21% 36% 25%	482
	11th to 20th	Day	12% 3 6% 21% 35% 23%	330
	21st to end	Day	11% 2 8% 27% 37% 15%	330
October	1st to 10th	Day	7% 2 12% 43% 27% 10%	330
	11th to 20th	Day	9% 4 17% 37% 22% 11%	330
	21st to end	Day	17% 7% 24% 28% 19% 5%	363
November	1st to 10th	Day	15% 6% 21% 32% 21% 4	330
	11th to 20th	Day	15% 7% 24% 38% 14% 2	330
	21st to end	Day	19% 13% 32% 23% 12% 2	330
December	1st to 10th	Day	22% 7% 32% 24% 10% 5%	330
	11th to 20th	Day	18% 8% 35% 29% 9% 1	330
	21st to end	Day	19% 11% 34% 25% 9% 2	363
January	1st to 10th	Night	22% 6% 32% 32% 8%	1050
	11th to 20th	Night	22% 7% 29% 33% 9%	1050
	21st to end	Night	24% 7% 28% 36% 6%	1155
February	1st to 10th	Night	24% 8% 28% 34% 6%	1050
	11th to 20th	Night	27% 9% 26% 30% 8%	746
	21st to end	Night	24% 8% 32% 31% 4	519
March	1st to 10th	Night	25% 7% 28% 34% 6%	630
	11th to 20th	Night	21% 7% 29% 34% 9%	630
	21st to end	Night	18% 7% 28% 34% 13%	693
April	1st to 10th	Night	20% 7% 28% 37% 8%	630
	11th to 20th	Night	20% 9% 23% 34% 13%	623
	21st to end	Night	17% 7% 26% 36% 13%	630
May	1st to 10th	Night	17% 6% 24% 42% 11%	630
	11th to 20th	Night	13% 5% 20% 40% 21% 1	621
	21st to end	Night	8% 4 17% 39% 29% 3	683
June	1st to 10th	Night	7% 2 6% 35% 45% 4	630
	11th to 20th	Night	6% 2 7% 36% 43% 7%	630
	21st to end	Night	7% 2 6% 25% 49% 10%	630
July	1st to 10th	Night	7% 2 2 22% 53% 14%	615
	11th to 20th	Night	5% 1 2 19% 53% 19%	612
	21st to end	Night	4 2 4 22% 53% 16%	687
August	1st to 10th	Night	2 1 2 17% 64% 15%	597
	11th to 20th	Night	5% 1 1 13% 61% 20%	594
	21st to end	Night	8% 2 3 17% 53% 17%	660
September	1st to 10th	Night	7% 2 6% 22% 50% 14%	600
	11th to 20th	Night	11% 2 3 22% 54% 8%	600
	21st to end	Night	10% 2 4 29% 48% 8%	600
October	1st to 10th	Night	7% 2 7% 34% 44% 6%	788
	11th to 20th	Night	10% 3 16% 39% 29% 4	800
	21st to end	Night	13% 5% 17% 38% 25% 3	880
November	1st to 10th	Night	11% 5% 16% 38% 28% 2	820
	11th to 20th	Night	12% 5% 22% 41% 19%	840
	21st to end	Night	18% 5% 28% 33% 15% 1	840
December	1st to 10th	Night	23% 6% 23% 34% 13% 1	981
	11th to 20th	Night	22% 7% 25% 34% 12%	1050
	21st to end	Night	21% 7% 27% 34% 10%	1155

Page generated at 2026-07-28 02:25:19. Version ac07

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