Pearland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pearland clear sky chart from 2005-11-06 to 2026-08-15.

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	12% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	143202
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 45%	139009
Transparency	Day	40% 7% 13% 20% 14% 6%	146851
	Night	38% 5% 13% 20% 16% 8%	143427
Seeing	Day	14% 7% 20% 27% 22% 10%	17201
	Night	15% 6% 20% 33% 24% 3	26958

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	19% 11% 2 7% 3 3 3 2 3 4 42%	5289
	11th to 20th	Day	13% 6% 2 6% 4 3 3 3 4 6% 51%	5310
	21st to end	Day	27% 9% 3 9% 3 3 3 3 4 6% 32%	5812
February	1st to 10th	Day	19% 8% 3 7% 5% 4 5% 3 5% 5% 35%	1990
	11th to 20th	Day	21% 9% 3 6% 4 4 4 3 5% 5% 35%	2088
	21st to end	Day	21% 8% 2 6% 4 4 3 3 4 5% 40%	1903
March	1st to 10th	Day	15% 8% 3 7% 5% 4 5% 4 5% 8% 36%	5046
	11th to 20th	Day	12% 6% 3 7% 5% 4 4 3 4 6% 46%	5090
	21st to end	Day	18% 7% 2 7% 4 4 4 3 5% 6% 40%	5583
April	1st to 10th	Day	15% 8% 4 9% 4 4 4 4 5% 6% 37%	2310
	11th to 20th	Day	17% 7% 3 7% 5% 5% 3 4 6% 8% 36%	2451
	21st to end	Day	11% 7% 3 8% 5% 5% 6% 4 6% 6% 39%	2520
May	1st to 10th	Day	19% 8% 3 8% 6% 6% 5% 4 6% 7% 29%	7070
	11th to 20th	Day	10% 6% 2 7% 6% 5% 5% 4 6% 7% 42%	7627
	21st to end	Day	10% 7% 2 8% 5% 6% 7% 5% 8% 10% 32%	8392
June	1st to 10th	Day	6% 6% 2 6% 6% 6% 6% 5% 9% 10% 39%	2730
	11th to 20th	Day	6% 5% 2 7% 5% 6% 8% 7% 9% 11% 36%	2730
	21st to end	Day	7% 6% 2 8% 7% 7% 8% 7% 9% 10% 30%	2730
July	1st to 10th	Day	6% 4 2 7% 6% 6% 8% 6% 9% 12% 34%	7680
	11th to 20th	Day	8% 7% 3 10% 7% 6% 7% 6% 8% 11% 28%	7680
	21st to end	Day	8% 5% 3 6% 5% 5% 5% 4 6% 11% 42%	8337
August	1st to 10th	Day	2 2 1 4 4 4 5% 5% 8% 11% 54%	4364
	11th to 20th	Day	3 3 1 5% 4 5% 6% 5% 10% 13% 45%	4026
	21st to end	Day	8% 5% 2 7% 6% 7% 7% 6% 8% 10% 34%	4247
September	1st to 10th	Day	7% 7% 3 9% 6% 7% 6% 6% 8% 9% 34%	2200
	11th to 20th	Day	13% 6% 2 7% 5% 5% 6% 6% 7% 9% 34%	2200
	21st to end	Day	9% 5% 2 7% 5% 4 5% 4 6% 8% 45%	2200
October	1st to 10th	Day	6% 4 2 6% 4 3 4 4 5% 7% 54%	2073
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 6% 6% 52%	2000
	21st to end	Day	12% 5% 2 5% 4 4 4 3 4 6% 53%	2200
November	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 3 6% 7% 46%	2058
	11th to 20th	Day	13% 6% 2 6% 3 4 4 4 6% 6% 46%	2100
	21st to end	Day	15% 7% 3 7% 5% 4 5% 3 5% 6% 41%	2068
December	1st to 10th	Day	25% 8% 3 6% 4 4 4 2 4 7% 34%	3030
	11th to 20th	Day	13% 7% 3 6% 4 4 5% 4 6% 7% 42%	3481
	21st to end	Day	14% 7% 2 6% 3 4 4 3 5% 6% 45%	4587
January	1st to 10th	Night	17% 6% 2 6% 4 4 3 3 4 6% 44%	7634
	11th to 20th	Night	13% 7% 2 6% 4 3 4 3 4 5% 48%	7680
	21st to end	Night	28% 9% 3 8% 3 3 3 2 4 5% 32%	8402
February	1st to 10th	Night	19% 8% 3 7% 4 4 3 2 4 6% 40%	2646
	11th to 20th	Night	21% 9% 3 5% 3 3 3 2 4 5% 42%	2416
	21st to end	Night	21% 8% 2 6% 4 3 3 3 3 7% 40%	1903
March	1st to 10th	Night	22% 10% 3 6% 3 3 4 3 4 6% 36%	5029
	11th to 20th	Night	17% 8% 2 6% 4 3 3 3 4 5% 45%	5090
	21st to end	Night	17% 10% 2 6% 4 3 4 3 3 5% 42%	5588
April	1st to 10th	Night	16% 8% 3 6% 4 4 4 4 5% 8% 39%	2310
	11th to 20th	Night	19% 6% 2 5% 3 3 3 4 5% 7% 44%	2117
	21st to end	Night	13% 7% 2 6% 6% 4 4 3 6% 8% 41%	2100
May	1st to 10th	Night	25% 11% 3 7% 5% 4 5% 3 5% 7% 26%	5780
	11th to 20th	Night	15% 9% 3 7% 4 4 4 4 5% 7% 39%	5265
	21st to end	Night	15% 8% 3 7% 5% 5% 5% 4 8% 10% 30%	5793
June	1st to 10th	Night	5% 3 1 4 3 3 4 3 7% 12% 53%	1890
	11th to 20th	Night	6% 3 2 4 3 3 4 4 7% 10% 54%	1890
	21st to end	Night	6% 4 2 5% 4 5% 6% 5% 7% 10% 46%	1890
July	1st to 10th	Night	4 4 2 4 3 4 4 4 7% 13% 51%	5308
	11th to 20th	Night	5% 5% 2 7% 5% 5% 5% 4 8% 10% 43%	5307
	21st to end	Night	5% 4 2 6% 4 4 4 4 6% 11% 50%	5770
August	1st to 10th	Night	1 1 2 2 2 3 2 5% 10% 72%	3016
	11th to 20th	Night	2 2 1 3 2 3 3 4 8% 14% 60%	3111
	21st to end	Night	5% 3 2 5% 4 4 5% 5% 8% 12% 48%	3644
September	1st to 10th	Night	5% 4 2 7% 5% 5% 5% 4 8% 10% 46%	2200
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 5% 8% 46%	2200
	21st to end	Night	8% 5% 2 5% 3 3 4 3 5% 8% 54%	2200
October	1st to 10th	Night	5% 4 1 3 3 3 4 2 5% 7% 62%	2305
	11th to 20th	Night	8% 4 1 3 3 3 3 3 5% 6% 61%	2400
	21st to end	Night	10% 5% 2 4 3 3 3 3 3 5% 60%	2640
November	1st to 10th	Night	10% 5% 2 5% 3 4 3 3 5% 6% 55%	2460
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 5% 54%	2520
	21st to end	Night	15% 6% 3 5% 4 4 4 3 5% 5% 46%	2546
December	1st to 10th	Night	24% 11% 3 7% 4 4 3 2 4 5% 32%	4380
	11th to 20th	Night	13% 8% 3 6% 5% 4 4 3 4 5% 45%	4946
	21st to end	Night	15% 7% 3 6% 4 4 3 3 4 6% 47%	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	47% 3 5% 21% 17% 7%	5290
	11th to 20th	Day	36% 3 5% 22% 21% 13%	5310
	21st to end	Day	55% 2 4 13% 15% 10%	5812
February	1st to 10th	Day	51% 4 6% 13% 16% 11%	1990
	11th to 20th	Day	51% 5% 7% 14% 16% 8%	2098
	21st to end	Day	48% 4 7% 16% 16% 9%	1903
March	1st to 10th	Day	45% 6% 9% 18% 12% 11%	5046
	11th to 20th	Day	40% 6% 7% 11% 21% 16%	5090
	21st to end	Day	44% 5% 8% 19% 20% 4	5585
April	1st to 10th	Day	46% 5% 8% 17% 15% 9%	2310
	11th to 20th	Day	46% 5% 9% 17% 15% 9%	2451
	21st to end	Day	42% 6% 9% 19% 18% 6%	2520
May	1st to 10th	Day	52% 7% 9% 18% 11% 2	7105
	11th to 20th	Day	40% 6% 12% 22% 18% 3	7631
	21st to end	Day	41% 10% 15% 27% 7% 1	8405
June	1st to 10th	Day	35% 9% 16% 24% 15% 1	2730
	11th to 20th	Day	37% 9% 13% 25% 14% 2	2730
	21st to end	Day	41% 10% 18% 23% 8%	2730
July	1st to 10th	Day	35% 11% 34% 19% 2	7616
	11th to 20th	Day	45% 10% 26% 16% 4	7611
	21st to end	Day	34% 8% 19% 33% 6%	8155
August	1st to 10th	Day	20% 7% 16% 42% 14%	4350
	11th to 20th	Day	24% 9% 32% 30% 3 1	4065
	21st to end	Day	40% 11% 17% 20% 11% 1	4246
September	1st to 10th	Day	43% 9% 14% 17% 13% 4	2200
	11th to 20th	Day	43% 8% 12% 21% 14% 3	2200
	21st to end	Day	34% 7% 12% 20% 16% 11%	2200
October	1st to 10th	Day	21% 4 5% 16% 17% 37%	3372
	11th to 20th	Day	22% 5% 5% 18% 37% 13%	3240
	21st to end	Day	26% 4 5% 18% 34% 13%	3538
November	1st to 10th	Day	36% 5% 9% 19% 22% 8%	2058
	11th to 20th	Day	37% 5% 9% 15% 21% 13%	2100
	21st to end	Day	43% 4 8% 18% 17% 10%	2068
December	1st to 10th	Day	50% 4 6% 17% 19% 4	3030
	11th to 20th	Day	39% 5% 9% 17% 20% 10%	3479
	21st to end	Day	40% 4 7% 17% 20% 13%	4587
January	1st to 10th	Night	42% 4 10% 18% 18% 9%	7635
	11th to 20th	Night	39% 3 4 17% 23% 14%	7680
	21st to end	Night	56% 2 4 13% 16% 8%	8402
February	1st to 10th	Night	48% 3 7% 11% 18% 13%	2646
	11th to 20th	Night	46% 3 7% 15% 17% 11%	2416
	21st to end	Night	48% 4 5% 14% 19% 10%	1903
March	1st to 10th	Night	50% 4 7% 15% 14% 10%	5029
	11th to 20th	Night	42% 5% 7% 13% 17% 16%	5090
	21st to end	Night	44% 5% 8% 15% 20% 8%	5588
April	1st to 10th	Night	44% 6% 9% 17% 15% 9%	2310
	11th to 20th	Night	40% 5% 10% 18% 14% 12%	2117
	21st to end	Night	41% 5% 11% 21% 16% 7%	2100
May	1st to 10th	Night	58% 6% 9% 16% 10% 3	5810
	11th to 20th	Night	43% 6% 10% 22% 15% 4	5266
	21st to end	Night	46% 9% 19% 21% 5%	5805
June	1st to 10th	Night	24% 6% 21% 31% 17%	1890
	11th to 20th	Night	25% 5% 19% 32% 17% 2	1890
	21st to end	Night	31% 8% 23% 27% 11%	1890
July	1st to 10th	Night	24% 6% 41% 26% 2	5265
	11th to 20th	Night	36% 8% 30% 22% 4	5256
	21st to end	Night	28% 8% 21% 35% 7%	5641
August	1st to 10th	Night	10% 5% 21% 49% 15%	3006
	11th to 20th	Night	15% 7% 36% 37% 4 1	3138
	21st to end	Night	28% 14% 21% 27% 9% 1	3644
September	1st to 10th	Night	32% 9% 22% 20% 13% 4	2200
	11th to 20th	Night	36% 7% 14% 24% 17% 3	2200
	21st to end	Night	30% 5% 14% 24% 19% 10%	2200
October	1st to 10th	Night	18% 4 7% 19% 18% 34%	3773
	11th to 20th	Night	16% 4 5% 24% 33% 17%	3899
	21st to end	Night	21% 3 5% 17% 36% 18%	4252
November	1st to 10th	Night	31% 5% 11% 22% 22% 10%	2460
	11th to 20th	Night	32% 4 9% 22% 21% 12%	2520
	21st to end	Night	40% 4 9% 20% 18% 9%	2546
December	1st to 10th	Night	54% 4 5% 16% 15% 6%	4380
	11th to 20th	Night	41% 5% 9% 13% 19% 14%	4947
	21st to end	Night	40% 4 6% 14% 27% 8%	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	25% 13% 34% 18% 8% 2	330
	11th to 20th	Day	22% 14% 34% 24% 7% 1	330
	21st to end	Day	23% 16% 33% 21% 7%	363
February	1st to 10th	Day	19% 16% 36% 21% 7%	330
	11th to 20th	Day	26% 20% 30% 19% 5% 1	330
	21st to end	Day	26% 16% 39% 15% 3 1	273
March	1st to 10th	Day	22% 21% 34% 20% 4	330
	11th to 20th	Day	17% 18% 42% 16% 5% 2	330
	21st to end	Day	21% 15% 31% 21% 9% 2	363
April	1st to 10th	Day	19% 19% 35% 22% 5%	330
	11th to 20th	Day	22% 17% 26% 23% 11% 1	489
	21st to end	Day	18% 12% 32% 24% 13% 1	540
May	1st to 10th	Day	19% 9% 34% 25% 12% 1	554
	11th to 20th	Day	14% 7% 31% 30% 15% 3	775
	21st to end	Day	12% 4 26% 38% 17% 3	844
June	1st to 10th	Day	8% 4 16% 34% 28% 10%	780
	11th to 20th	Day	8% 3 14% 37% 28% 10%	780
	21st to end	Day	10% 2 9% 33% 29% 17%	780
July	1st to 10th	Day	9% 2 8% 28% 32% 22%	771
	11th to 20th	Day	7% 2 4 28% 37% 23%	768
	21st to end	Day	6% 1 5% 29% 37% 22%	849
August	1st to 10th	Day	3 1 3 26% 43% 25%	776
	11th to 20th	Day	5% 1 3 20% 41% 30%	616
	21st to end	Day	13% 2 5% 16% 33% 30%	544
September	1st to 10th	Day	9% 2 8% 28% 34% 18%	330
	11th to 20th	Day	11% 2 7% 29% 36% 15%	330
	21st to end	Day	10% 1 6% 33% 38% 12%	330
October	1st to 10th	Day	7% 1 10% 44% 30% 8%	330
	11th to 20th	Day	12% 4 15% 38% 21% 9%	330
	21st to end	Day	16% 9% 26% 27% 18% 4	363
November	1st to 10th	Day	14% 5% 24% 34% 19% 4	330
	11th to 20th	Day	16% 4 28% 34% 15% 3	330
	21st to end	Day	17% 15% 35% 19% 11% 3	330
December	1st to 10th	Day	24% 5% 34% 22% 10% 4	330
	11th to 20th	Day	20% 13% 32% 25% 9% 2	330
	21st to end	Day	18% 10% 35% 23% 13% 1	363
January	1st to 10th	Night	21% 9% 31% 29% 9%	1050
	11th to 20th	Night	22% 9% 27% 34% 8% 1	1050
	21st to end	Night	22% 10% 29% 33% 6%	1155
February	1st to 10th	Night	24% 9% 30% 31% 6%	966
	11th to 20th	Night	26% 10% 26% 30% 8%	782
	21st to end	Night	24% 12% 34% 25% 6%	519
March	1st to 10th	Night	27% 7% 29% 30% 7%	630
	11th to 20th	Night	19% 10% 31% 31% 8%	630
	21st to end	Night	18% 6% 30% 34% 11% 1	693
April	1st to 10th	Night	18% 10% 31% 35% 7%	630
	11th to 20th	Night	22% 8% 27% 33% 10%	623
	21st to end	Night	18% 8% 28% 34% 11%	630
May	1st to 10th	Night	19% 7% 26% 39% 9%	630
	11th to 20th	Night	14% 5% 25% 40% 15% 1	621
	21st to end	Night	8% 4 22% 41% 23% 2	683
June	1st to 10th	Night	6% 2 8% 43% 37% 3	630
	11th to 20th	Night	7% 2 9% 45% 35% 3	630
	21st to end	Night	6% 1 9% 31% 46% 7%	630
July	1st to 10th	Night	5% 2 4 31% 49% 10%	615
	11th to 20th	Night	4 2 2 26% 57% 10%	612
	21st to end	Night	5% 1 3 27% 56% 8%	690
August	1st to 10th	Night	1 2 25% 63% 10%	627
	11th to 20th	Night	5% 1 21% 63% 10%	606
	21st to end	Night	7% 2 2 19% 55% 15%	660
September	1st to 10th	Night	6% 1 5% 23% 53% 12%	600
	11th to 20th	Night	12% 1 4 27% 49% 8%	600
	21st to end	Night	12% 1 6% 30% 45% 7%	600
October	1st to 10th	Night	6% 1 9% 36% 41% 7%	705
	11th to 20th	Night	8% 3 18% 41% 27% 4	800
	21st to end	Night	11% 7% 20% 35% 25% 2	880
November	1st to 10th	Night	11% 3 17% 41% 26% 2	820
	11th to 20th	Night	13% 4 22% 41% 19%	840
	21st to end	Night	18% 7% 27% 32% 14% 2	866
December	1st to 10th	Night	22% 7% 25% 30% 15% 1	1050
	11th to 20th	Night	20% 9% 25% 34% 11%	1050
	21st to end	Night	21% 8% 28% 33% 9% 1	1155

Page generated at 2026-08-12 02:37:13. Version ac07

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