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 2025-04-11.

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% 7% 2 7% 5% 5% 5% 4 6% 8% 39%	113923
	Night	14% 7% 2 6% 4 3 4 3 5% 7% 45%	114556
Transparency	Day	40% 6% 11% 19% 16% 7%	117613
	Night	38% 5% 11% 20% 17% 9%	118995
Seeing	Day	14% 7% 20% 27% 22% 10%	15271
	Night	15% 6% 20% 33% 24% 3	25282

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	21% 11% 3 7% 3 3 3 2 4 4 39%	4077
	11th to 20th	Day	15% 7% 2 5% 3 3 3 3 4 7% 49%	4080
	21st to end	Day	28% 10% 2 6% 3 3 3 3 4 6% 32%	4488
February	1st to 10th	Day	20% 9% 3 7% 5% 4 5% 3 5% 5% 34%	1895
	11th to 20th	Day	22% 10% 3 6% 4 4 3 3 4 5% 36%	1986
	21st to end	Day	22% 8% 2 6% 4 4 3 3 4 5% 38%	1815
March	1st to 10th	Day	15% 8% 3 7% 5% 4 5% 4 5% 8% 37%	4936
	11th to 20th	Day	13% 6% 3 7% 5% 4 4 3 4 6% 45%	4980
	21st to end	Day	18% 7% 2 7% 5% 4 4 3 5% 6% 39%	5462
April	1st to 10th	Day	15% 8% 3 8% 5% 4 4 4 5% 6% 38%	2200
	11th to 20th	Day	17% 7% 3 7% 5% 5% 3 4 6% 7% 36%	2215
	21st to end	Day	11% 7% 2 7% 5% 5% 6% 4 6% 6% 41%	2280
May	1st to 10th	Day	16% 8% 3 8% 6% 5% 5% 4 6% 7% 31%	3787
	11th to 20th	Day	14% 6% 3 7% 6% 4 5% 4 5% 7% 40%	4082
	21st to end	Day	8% 6% 2 7% 5% 6% 7% 6% 8% 11% 35%	4477
June	1st to 10th	Day	6% 5% 2 6% 6% 6% 5% 5% 9% 10% 40%	2470
	11th to 20th	Day	5% 4 2 6% 5% 6% 8% 7% 9% 11% 37%	2470
	21st to end	Day	7% 6% 3 8% 8% 7% 8% 7% 10% 10% 27%	2470
July	1st to 10th	Day	8% 6% 2 7% 7% 6% 8% 7% 8% 11% 29%	4120
	11th to 20th	Day	7% 7% 3 12% 8% 7% 8% 6% 8% 10% 23%	4120
	21st to end	Day	14% 8% 4 7% 6% 6% 7% 5% 7% 9% 25%	4465
August	1st to 10th	Day	2 2 1 4 4 4 5% 5% 7% 11% 55%	4104
	11th to 20th	Day	3 2 1 5% 4 5% 6% 5% 10% 13% 45%	3850
	21st to end	Day	8% 5% 2 7% 6% 7% 7% 6% 8% 10% 35%	4117
September	1st to 10th	Day	8% 7% 3 9% 6% 7% 6% 6% 8% 9% 32%	2090
	11th to 20th	Day	14% 7% 2 7% 5% 5% 6% 6% 7% 9% 33%	2090
	21st to end	Day	9% 5% 2 7% 5% 4 5% 4 6% 8% 45%	2090
October	1st to 10th	Day	7% 5% 2 6% 4 3 4 4 6% 7% 53%	1970
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 6% 7% 50%	1900
	21st to end	Day	12% 5% 2 5% 4 3 4 3 4 6% 53%	2090
November	1st to 10th	Day	11% 6% 3 6% 4 5% 5% 3 6% 8% 44%	1958
	11th to 20th	Day	13% 6% 2 6% 3 4 4 4 6% 6% 45%	2000
	21st to end	Day	15% 7% 3 7% 5% 4 4 3 4 5% 42%	1970
December	1st to 10th	Day	25% 8% 3 5% 4 4 4 2 4 7% 34%	2940
	11th to 20th	Day	13% 7% 3 6% 4 4 5% 4 6% 7% 42%	3391
	21st to end	Day	15% 7% 2 6% 3 4 4 3 5% 6% 45%	4488
January	1st to 10th	Night	20% 7% 2 6% 4 4 3 3 4 6% 40%	5888
	11th to 20th	Night	16% 8% 2 6% 3 3 3 3 4 6% 47%	5900
	21st to end	Night	28% 9% 3 6% 3 3 3 3 4 6% 32%	6490
February	1st to 10th	Night	20% 9% 3 7% 4 4 3 3 4 6% 38%	2520
	11th to 20th	Night	21% 9% 3 6% 3 3 3 2 4 5% 42%	2298
	21st to end	Night	22% 8% 2 6% 4 3 3 3 3 6% 39%	1815
March	1st to 10th	Night	21% 10% 3 6% 3 3 4 3 4 6% 36%	4919
	11th to 20th	Night	17% 9% 2 6% 4 3 3 3 4 5% 44%	4980
	21st to end	Night	18% 10% 3 6% 4 3 4 3 3 6% 42%	5467
April	1st to 10th	Night	15% 7% 3 6% 4 4 4 4 5% 8% 39%	2200
	11th to 20th	Night	20% 6% 2 4 3 3 4 3 5% 6% 43%	1919
	21st to end	Night	13% 6% 3 6% 6% 4 4 3 6% 8% 42%	1900
May	1st to 10th	Night	25% 10% 2 7% 5% 3 4 3 5% 7% 29%	3103
	11th to 20th	Night	12% 8% 2 7% 5% 4 5% 4 5% 6% 42%	2823
	21st to end	Night	13% 7% 3 7% 4 5% 4 4 9% 11% 34%	3090
June	1st to 10th	Night	5% 3 1 3 3 3 4 3 7% 12% 55%	1710
	11th to 20th	Night	5% 3 1 4 3 3 4 4 7% 11% 55%	1710
	21st to end	Night	5% 4 1 5% 5% 5% 6% 5% 7% 11% 45%	1710
July	1st to 10th	Night	5% 5% 2 4 4 4 4 4 7% 12% 48%	2850
	11th to 20th	Night	3 4 2 6% 6% 6% 5% 5% 9% 11% 44%	2850
	21st to end	Night	8% 6% 3 8% 5% 4 5% 4 7% 11% 38%	3098
August	1st to 10th	Night	1 1 1 2 2 3 2 4 11% 73%	2836
	11th to 20th	Night	2 2 1 3 2 3 3 4 8% 14% 59%	2979
	21st to end	Night	5% 3 2 5% 4 4 5% 5% 8% 12% 49%	3532
September	1st to 10th	Night	5% 4 2 7% 5% 5% 5% 4 8% 10% 46%	2090
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 5% 8% 45%	2090
	21st to end	Night	8% 5% 2 5% 3 3 4 3 5% 8% 54%	2090
October	1st to 10th	Night	5% 4 2 3 4 3 4 3 5% 6% 61%	2190
	11th to 20th	Night	9% 4 1 3 3 3 3 3 5% 6% 61%	2280
	21st to end	Night	10% 5% 2 4 3 3 3 2 3 5% 60%	2508
November	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 5% 6% 53%	2340
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 5% 5% 53%	2400
	21st to end	Night	15% 6% 3 5% 4 4 4 3 5% 5% 46%	2425
December	1st to 10th	Night	23% 11% 3 7% 4 4 3 3 4 6% 32%	4250
	11th to 20th	Night	13% 8% 3 6% 5% 4 4 3 4 5% 45%	4816
	21st to end	Night	15% 6% 2 6% 4 4 3 2 4 5% 47%	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	50% 3 3 20% 17% 6%	4078
	11th to 20th	Day	37% 4 5% 22% 22% 11%	4080
	21st to end	Day	54% 2 3 13% 15% 12%	4488
February	1st to 10th	Day	52% 4 5% 13% 15% 11%	1895
	11th to 20th	Day	51% 4 6% 13% 17% 8%	1996
	21st to end	Day	50% 4 7% 16% 15% 9%	1815
March	1st to 10th	Day	44% 6% 9% 17% 12% 12%	4936
	11th to 20th	Day	40% 6% 7% 10% 21% 16%	4980
	21st to end	Day	45% 5% 8% 19% 20% 4	5464
April	1st to 10th	Day	46% 5% 8% 17% 15% 9%	2200
	11th to 20th	Day	46% 4 9% 16% 16% 9%	2215
	21st to end	Day	41% 6% 8% 19% 20% 6%	2280
May	1st to 10th	Day	50% 7% 10% 18% 10% 4	3822
	11th to 20th	Day	42% 6% 8% 18% 22% 4	4086
	21st to end	Day	37% 10% 12% 31% 9%	4489
June	1st to 10th	Day	34% 9% 16% 25% 16% 1	2470
	11th to 20th	Day	37% 8% 13% 26% 15% 2	2470
	21st to end	Day	43% 10% 17% 21% 8%	2470
July	1st to 10th	Day	40% 10% 27% 19% 3	4056
	11th to 20th	Day	50% 11% 19% 16% 5%	4051
	21st to end	Day	50% 10% 17% 21% 3	4325
August	1st to 10th	Day	19% 6% 16% 43% 15%	4090
	11th to 20th	Day	24% 9% 32% 30% 4 1	3889
	21st to end	Day	40% 11% 17% 20% 12% 1	4116
September	1st to 10th	Day	44% 9% 14% 17% 12% 4	2090
	11th to 20th	Day	45% 8% 11% 18% 14% 3	2090
	21st to end	Day	35% 6% 12% 19% 17% 11%	2090
October	1st to 10th	Day	21% 4 5% 16% 16% 38%	3269
	11th to 20th	Day	22% 5% 5% 18% 36% 13%	3140
	21st to end	Day	26% 4 5% 18% 34% 13%	3428
November	1st to 10th	Day	38% 5% 10% 19% 21% 8%	1958
	11th to 20th	Day	38% 5% 9% 15% 20% 13%	2000
	21st to end	Day	44% 4 7% 17% 17% 10%	1970
December	1st to 10th	Day	50% 4 6% 17% 19% 4	2940
	11th to 20th	Day	39% 5% 9% 17% 20% 10%	3389
	21st to end	Day	40% 4 7% 16% 21% 13%	4488
January	1st to 10th	Night	45% 4 6% 19% 17% 9%	5888
	11th to 20th	Night	41% 3 4 18% 23% 11%	5900
	21st to end	Night	55% 2 4 13% 15% 11%	6490
February	1st to 10th	Night	49% 3 6% 11% 17% 13%	2520
	11th to 20th	Night	47% 3 7% 14% 18% 12%	2298
	21st to end	Night	49% 4 5% 14% 18% 10%	1815
March	1st to 10th	Night	50% 4 7% 14% 15% 10%	4919
	11th to 20th	Night	43% 5% 7% 13% 17% 16%	4980
	21st to end	Night	44% 5% 8% 15% 20% 8%	5467
April	1st to 10th	Night	43% 6% 9% 17% 15% 10%	2200
	11th to 20th	Night	41% 5% 10% 16% 15% 13%	1919
	21st to end	Night	40% 5% 9% 22% 17% 7%	1900
May	1st to 10th	Night	54% 6% 9% 16% 9% 5%	3133
	11th to 20th	Night	40% 7% 9% 19% 17% 7%	2824
	21st to end	Night	40% 10% 18% 25% 7% 1	3099
June	1st to 10th	Night	22% 6% 21% 32% 19%	1710
	11th to 20th	Night	24% 5% 19% 32% 18% 3	1710
	21st to end	Night	31% 8% 23% 27% 11%	1710
July	1st to 10th	Night	29% 7% 35% 26% 3	2805
	11th to 20th	Night	32% 10% 29% 25% 5%	2796
	21st to end	Night	39% 11% 25% 22% 3	2999
August	1st to 10th	Night	10% 5% 20% 50% 15%	2826
	11th to 20th	Night	15% 7% 36% 36% 4 1	3006
	21st to end	Night	27% 14% 21% 27% 9% 1	3532
September	1st to 10th	Night	32% 9% 23% 20% 13% 4	2090
	11th to 20th	Night	37% 7% 14% 23% 17% 3	2090
	21st to end	Night	29% 5% 13% 23% 19% 10%	2090
October	1st to 10th	Night	18% 4 7% 18% 17% 35%	3658
	11th to 20th	Night	16% 4 6% 23% 34% 17%	3779
	21st to end	Night	21% 3 5% 17% 37% 18%	4120
November	1st to 10th	Night	32% 5% 11% 22% 21% 9%	2340
	11th to 20th	Night	33% 4 9% 21% 20% 12%	2400
	21st to end	Night	40% 4 9% 20% 18% 9%	2425
December	1st to 10th	Night	54% 4 5% 17% 15% 5%	4250
	11th to 20th	Night	41% 5% 9% 13% 18% 14%	4817
	21st to end	Night	40% 4 6% 14% 28% 8%	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	26% 13% 34% 17% 8% 1	300
	11th to 20th	Day	23% 13% 35% 23% 6% 1	300
	21st to end	Day	23% 15% 34% 21% 7%	330
February	1st to 10th	Day	21% 17% 34% 20% 7%	300
	11th to 20th	Day	28% 19% 29% 19% 5% 1	300
	21st to end	Day	29% 16% 37% 15% 2 1	249
March	1st to 10th	Day	22% 22% 34% 19% 4	300
	11th to 20th	Day	17% 19% 44% 15% 3 2	300
	21st to end	Day	24% 16% 34% 18% 8%	330
April	1st to 10th	Day	19% 19% 34% 22% 6%	300
	11th to 20th	Day	23% 16% 26% 22% 11% 1	413
	21st to end	Day	17% 10% 31% 26% 15% 1	460
May	1st to 10th	Day	18% 8% 33% 27% 14% 1	472
	11th to 20th	Day	14% 5% 29% 32% 16% 3	675
	21st to end	Day	11% 4 26% 38% 17% 3	734
June	1st to 10th	Day	8% 3 14% 35% 29% 11%	680
	11th to 20th	Day	8% 2 14% 37% 29% 11%	680
	21st to end	Day	11% 3 9% 30% 30% 18%	680
July	1st to 10th	Day	9% 2 7% 28% 32% 22%	671
	11th to 20th	Day	6% 2 3 28% 37% 24%	668
	21st to end	Day	6% 1 5% 29% 37% 22%	739
August	1st to 10th	Day	3 3 25% 43% 25%	676
	11th to 20th	Day	5% 1 3 19% 41% 31%	552
	21st to end	Day	12% 2 6% 16% 32% 31%	502
September	1st to 10th	Day	10% 2 8% 24% 35% 20%	300
	11th to 20th	Day	11% 2 7% 28% 36% 16%	300
	21st to end	Day	11% 1 5% 32% 39% 13%	300
October	1st to 10th	Day	8% 1 11% 43% 30% 7%	300
	11th to 20th	Day	12% 4 15% 40% 19% 10%	300
	21st to end	Day	17% 10% 25% 25% 18% 4	330
November	1st to 10th	Day	15% 5% 24% 35% 18% 4	300
	11th to 20th	Day	17% 4 28% 33% 14% 3	300
	21st to end	Day	17% 15% 34% 19% 11% 3	300
December	1st to 10th	Day	23% 5% 33% 23% 10% 5%	300
	11th to 20th	Day	20% 13% 33% 24% 8% 2	300
	21st to end	Day	19% 11% 36% 22% 11% 2	330
January	1st to 10th	Night	22% 9% 30% 30% 9%	1000
	11th to 20th	Night	22% 9% 27% 34% 8% 1	1000
	21st to end	Night	22% 9% 29% 34% 6%	1100
February	1st to 10th	Night	25% 9% 30% 31% 6%	920
	11th to 20th	Night	27% 10% 26% 30% 8%	744
	21st to end	Night	25% 12% 34% 25% 5%	495
March	1st to 10th	Night	26% 8% 30% 30% 7%	600
	11th to 20th	Night	19% 11% 32% 31% 7% 1	600
	21st to end	Night	19% 6% 31% 33% 10% 1	660
April	1st to 10th	Night	17% 10% 32% 35% 7%	600
	11th to 20th	Night	23% 7% 26% 32% 11%	565
	21st to end	Night	18% 8% 28% 34% 12% 1	570
May	1st to 10th	Night	17% 6% 27% 40% 10%	570
	11th to 20th	Night	13% 4 24% 42% 17% 1	561
	21st to end	Night	7% 4 22% 42% 23% 2	617
June	1st to 10th	Night	6% 2 7% 44% 38% 3	570
	11th to 20th	Night	6% 2 8% 46% 36% 3	570
	21st to end	Night	6% 1 9% 30% 46% 8%	570
July	1st to 10th	Night	6% 2 4 30% 48% 10%	555
	11th to 20th	Night	4 1 2 26% 57% 10%	552
	21st to end	Night	5% 1 2 26% 57% 9%	624
August	1st to 10th	Night	1 2 25% 62% 10%	567
	11th to 20th	Night	5% 1 1 21% 62% 10%	564
	21st to end	Night	7% 2 2 20% 56% 14%	627
September	1st to 10th	Night	6% 1 5% 22% 54% 12%	570
	11th to 20th	Night	12% 1 4 27% 48% 7%	570
	21st to end	Night	12% 1 6% 29% 45% 7%	570
October	1st to 10th	Night	6% 1 9% 36% 41% 6%	670
	11th to 20th	Night	9% 3 18% 41% 27% 3	760
	21st to end	Night	11% 6% 20% 35% 25% 2	836
November	1st to 10th	Night	12% 3 17% 42% 25% 2	780
	11th to 20th	Night	14% 4 22% 41% 19%	800
	21st to end	Night	18% 7% 27% 32% 15% 2	825
December	1st to 10th	Night	21% 7% 26% 30% 15% 1	1000
	11th to 20th	Night	21% 10% 25% 34% 11%	1000
	21st to end	Night	21% 8% 29% 33% 9% 1	1100

Page generated at 2025-04-08 08:17:27. Version ac07

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