Scattered showers and thunderstorms pelted the Metroplex for much of May, forcing rain checks on countless outdoor gatherings and baseball practices. If climate trends hold up, North Texans can expect to see longer periods of rainfall and hotter temperatures in the decades to come.

That’s according to the new “climate normals” released this month by the National Oceanic and Atmospheric Administration, the federal scientific agency that houses the National Weather Service.

Using data from automated weather recorders and volunteer observers, the normals are updated every 10 years and offer a 30-year average of annual temperatures and precipitation along with the number of 100-degree days and freezes per year. The snapshot of the region’s climate influences decisions like when to plant crops or how much energy demand there will be during each season — an increasingly fraught prediction after widespread blackouts wracked Texas during the February winter storm.

In comparison to the 1981-2010 normals, the previous period released by the NOAA, the annual average temperature in Dallas-Fort Worth from 1991-2020 went up by .3 degrees while annual rainfall increased by .87 inches. The region’s average temperature is now 66.6 degrees, and precipitation comes in at 37.01 inches annually.

But, according to climate experts, those data points don’t tell the full story of what’s going on in North Texas or statewide.

Since the 1951-1980 normals were released, the average amount of rainfall has steadily increased by about 25%, according to Victor Murphy, the climate service program manager for the National Weather Service’s southern regional headquarters in Fort Worth.

The increase over the last 70 years translates to about eight more inches of rain per year, or a “pretty significant” uptick, Murphy said. Most of the U.S., ranging from central Texas to the southern plains in the eastern part of the country, has become wetter in the most recent climate normals, he added.

“That’s significant from a public policy perspective in making sure that our infrastructure can handle these rain events as they occur,” Murphy said. “Increasing temperatures can be a slow, steady thing, but I think the changes in rainfall patterns are something that’s going to be affecting us more day in, day out.”

Total rainfall may not appear to change year over year, and there will be fewer rainy days across the state. But when storms do arrive, North Texans can expect longer stretches of heavy rainfall, Murphy said.

“You get more days and more time in between the rain events, which puts you in that drought-flood pattern,” he said. “We’ve got extended dry periods, we get short bursts of heavy rainfall for a small period of time and then it turns dry again. The big picture of total rainfall is unchanged, but the way it’s occurring is changing.”

Intense storms mean more flooding, infrastructure issues

As extreme storms become more common across the state, policymakers have shifted focus to more extensive flood planning, especially in coastal areas more vulnerable to hurricanes in the southeast. Heavy rains can often lead to stress on existing infrastructure, such as several sewage overflows across Fort Worth last week.

Lawmakers passed a $1.7 billion flood control bill in 2019 that instructed the Texas Water Development Board to develop the state’s first-ever statewide flood plan. Fifteen regional groups have begun meeting to address concerns about urban flash flooding, particularly in the Trinity region that encompasses North Texas.

City planners have typically used a 100-year floodplain map, or the land that is predicted to flood during a once-every-hundred-year storm in any given year, to guide their development strategy, according to Arne Winguth, the chair of the department of earth and environmental sciences at UT-Arlington.

“In the future, one may need to use more extreme floodplains, like a 500-year floodplain, to show the more extreme possibilities of flooding,” Winguth said. “They could even use the “one in a thousand years” possibility, but the 500-year floodplain is probably a more reasonable assumption.”

In 2018, Winguth completed a study for the North Texas Council of Governments that documented how climate change, specifically hotter temperatures and flooding, will affect transportation infrastructure in DFW.

Winguth’s team predicted extreme temperatures of up to 125 degrees by the end of the century, which would bring with it a higher risk of cracks in infrastructure and larger risk of fires in wooded neighborhoods. Higher likelihoods of droughts could amplify the “urban heat island” effect and make it more than 10 degrees hotter in downtown Dallas and rural areas of the region.

While it’s no secret that extreme weather leads to more incidents on the road, Winguth’s group of researchers also showed how a higher risk of severe thunderstorms could lead to more accidents on interstates.

“In particular what we noticed in our study was that the feeder roads on the interstates are affected by flooding,” Winguth said. “Most interstates are high enough that they’re not affected, but flooding could be a cause of accidents on feeder roads.”

Impact on health, summer electricity outages

Beyond flooding, Winguth is concerned about how the rising temperatures, shown in the climate normals and other environmental studies, will affect public health. The highest number of weather-related fatalities are related to heat stress, and air quality also declines with increased heat and heightened ozone formation, according to Winguth.

The warming weather also leads to longer growing seasons, causing plants to increase the amount of pollen they produce and worsen allergy seasons in the spring and fall, according to the 2021 Allergy Capitals report from the Asthma and Allergy Foundation of America. Dallas came in at No. 19 on the foundation’s list of the most challenging cities in the U.S. to live with seasonal allergies.

More than 50 million Americans are living with nasal allergies, with about half of those experiencing seasonal pollen allergies, according to the foundation.

“Climate change continues to cause longer and more severe allergy seasons,” said Kenneth Mendez, the CEO and president of the foundation. “If we don’t slow down the cycle, pollen production will only intensify. This means symptoms could worsen as climate change continues to evolve.”

A report released by the North American Electric Reliability Corporation in late May also warned that Texas is expected to experience above-normal temperatures this summer as well as a higher risk of drought.

This could increase demand for energy and potentially lead to power outages, leaving residents without electricity and air conditioning during the hottest months of the year, the report warned. Estimates for the number of Texans who died during the winter storm outages have ranged from 194 to 700, though the state’s official count stands at 151.

The Electric Reliability Council of Texas, the manager of the grid known as ERCOT, is a “huge user” of climate normals to predict how much energy demand there will be on an average day, Murphy said. That will remain true this summer, as ERCOT works to keep the lights on amid an expected record-breaking demand for power in Texas.

But a string of extremely hot days could mix with low winds and warm nights to create a perfect storm for the grid to go overboard, according to NBC DFW. While ERCOT’s forecast shows a less than one percent chance of outages this summer, energy consultant Alison Silverstein told the station that Texas must do a better job of planning for extreme weather.

“Maybe we get lucky and none of those things happen, or maybe we get unlucky and all of that happens at the same time,” Silverstein said. “Let’s imagine everything that could possibly go wrong, make up a bunch of crazy scenarios and let’s actually start planning how we defend against those. We need to be much better at doing that here in Texas.”