Annual Rainfall in Houston, Texas

Annual Rainfall in Houston, Texas

In a recent survey, one topic you said you wanted to learn more about was climate change.  In this post, we look at one aspect of climate, rainfall.

What, Where, and When

If you wanted to look at data about climate, the amount of data and the ways you could examine it could almost seem endless.  To narrow things a bit, we thought we’d focus on one topic (rainfall), one type of data (annual rainfall), one set time period (the last forty years), and one place (Houston, Texas).

We thought rainfall would be a good topic to look at because it is part of climate, something we all experience, and it has a strong influence on trees.  We thought we’d look at annual rainfall (as opposed to monthly or some other measure) because it seemed simpler, and it gave an amount that people might associate with the climate of an area.  We picked forty years because data was available for it and it seemed a long enough time without being too long.  Lastly, we picked Houston, Texas because it is the fourth largest city in the U.S., and because it happens to be the largest big city near ArborTrue.

The raw data we used came from the National Weather Service.  We used this data to come up with the ideas and information below.

The Raw Data

First, here’s the raw data:

Here it is in graphical form:

Some Simple Statistics

From this data, we calculated some simple statistics:

  Average annual rainfall: 50.04625 inches

  Median annual rainfall: 48.665 inches

  Minimum annual rainfall: 22.93 inches

  Maximum annual rainfall: 79.69 inches

  Percent of years with annual rainfall of at least 30 inches: 92.5%

  Percent of years with annual rainfall of at least 40 inches: 90%

  Percent of years with annual rainfall of at least 50 inches: 47.5%

  Percent of years with annual rainfall of at least 60 inches: 20%

  Percent of years with annual rainfall of at least 70 inches: 7.5%

  Average annual rainfall 1983 to 1992: 46.554 inches

  Average annual rainfall 1993 to 2002: 51.015 inches

  Average annual rainfall 2003 to 2012: 48.503 inches

  Average annual rainfall 2013 to 2022: 54.113 inches

Some Inferences from the Data

Looking at this data, there are some things you can tell.

First, the average annual rainfall in Houston, Texas over the last forty years has been at least 40 inches in 90% of the years.

Second, in the last forty years, there have been three years of markedly lower annual rainfall: 1988 with 22.93 inches, 1999 with 28.04 inches, and 2011 with 24.57 inches.  These were the only years in the last forty with total annual rainfall of less than 30 inches.  They occurred between 10 and 11 years apart.

Third, in the last forty years, there have been eight years with total annual rainfall of at least 60 inches.  These were: 1991 (61.09 in), 1997 (60.02 in), 2001 (71.18 in), 2004 (65.06 in), 2007 (65.52 in), 2015 (70.03 in), 2016 (60.96 in), and 2017 (79.69 in).  Half of these occurred in the last 20 years, and half before.

Fourth, although not specifically shown in this data, the average annual rainfall amounts in Houston, Texas over the last 40 years were influenced by tropical systems.  Here is a list of named systems (and one unnamed) that impacted the southeast Texas coast from 1983 – 2019, along with the total annual rainfall for Houston, Texas for those years (the data in the set went to 2019, rather than 2022).  The information for the list is also from the National Weather Service.

Here are some insights from this:

  11 of the 15 years noted had total yearly rainfall above the average 50.04625 inches annual rainfall for the 40-year period.

  Three of the last 40 years had rainfall of 70 or more inches.  These years are 2001, 2015, and 2017.  These coincide with years with systems noted.

  The years with the lowest total annual rainfall (those with less than 30 inches) 1988 (22.93 inches), 1999 (28.04 inches), and 2011 (24.57 inches), coincide with years without systems noted.

It seems from this, that tropical systems have an influence on the annual rainfall rates in Houston, Texas.

What Does This Mean for You?

Whether you live in Houston, Texas or somewhere else, knowing something about your area’s climate and information about the annual rainfall can help you when it comes to your landscape trees and other plants.

Selecting Trees and Plants

One thing you might think about is which trees and other plants you want for your landscape.  Although you might normally think about a plant’s hardiness to an area, knowing the plant’s optimal rainfall can also be useful information when you think about what you might want in your landscape.  For those in Houston, knowing that the average annual rainfall over the last forty years has been around 50 inches per year, that rainfall has ranged from around 23 inches to around 80 inches for a total for each year, and that 90% of the years over the last forty years have had annual rainfalls of 40 inches or more, can all be useful pieces of information when thinking about plants for your landscape.  For example, if you find a plant that might do best with 10 inches of rain per year, you might decide to look for something else.

Selecting the right trees for your landscape can be a difficult decision.  There are a number of factors, one of which are the water requirements of the tree.  An arborist can tell you more about what trees might be suitable for your landscape and can help you choose ones you might want to choose from.

Waiting for Dry Ground Before Planting

Another thing about rainfall that we’ve mentioned before is the idea of waiting for the ground to dry out before planting trees.  In a climate like Houston’s, where there can be a substantial amount of rain, some of which can fall in short periods, this can be important to keep in mind when thinking about having trees planted in your landscape.

Generalities of Annual Rainfall

One thing to keep in mind about the averages and other information above, is that they are generalities.  Although an average can tell you useful information about an area’s climate, it doesn’t tell you information about what might happen during any specific period of time.  It also doesn’t tell you information about your specific area.  Although Houston can generally have a wet climate, it can also have periods of extended drought.  Additionally, a place like Houston is very large, and one side of town can experience different conditions than another.  Also, as referenced above, in an area like Houston with hurricanes, a substantial amount of rain can fall in a short period of time, increasing the annual total for a year.

Weather and Climate

Although the climate in your area is important, you should also keep in mind the weather.  The day-to-day rainfall, and rainfall month to month, can be very important for the trees in your landscape.  You might consider checking the weather regularly and maybe even having a home rain gauge to help you better understand your local weather conditions.  You can use this information to help you adjust how you water the trees in your landscape.

Climate is a very important topic.  The long-term conditions in an area can have a significant impact on people and plants.  Knowing a little more about the climate of an area, and in this case rainfall, can help you understand more about the area and can give you information that can help you as you care for the trees and plants in your landscape.