Houston's weather has gotten hotter and wetter, according to the latest data from the National Oceanic and Atmospheric Administration. It mirrors a general trend across the country as the planet warms.
Every 10 years, NOAA updates what it considers "normal " weather across the country. The so-called "new climate normals" are based on rolling averages of temperature and precipitation from the past 30 years, with the latest update reflecting weather data from 1991-2020. The previous normals were based on data from 1981-2010.
These "climate normals" are what meteorologists use when they talk about typical weather in a city.
"It’s helpful in the sense that it lets us set the tone for what should be happening in an idealized world," said Matt Lanza, a meteorologist and managing editor for Space City Weather. "It puts perspective around what the weather is doing at any particular time of year, how uncommon or how common it is."
Houston's average monthly temperatures got warmer in both the winter and summer months, according to data taken at Bush Intercontinental Airport. The only exceptions were November and December, which showed a slight decrease in average temperatures.
But Lanza said the later winter months stood out to him as the most dramatic, with average highs and lows increasing by more than a degree in both February and March.
He said the number of days when the temperature exceeds 90 degrees also increased in Houston by about a week.
"When you think about how hot Houston is in the summer, any kind of increase is not really good," Lanza said. "When you’re talking about a half a degree to a degree warmer for your ‘normal,’ maybe that’s closer to reality, but it’s also maybe somewhat disconcerting."
Data from Galveston and Houston's Hobby airport also showed average temperatures increasing year round. In Galveston, the average high increased by more than 2 degrees in both February and April.
NOAA scientists say that nationwide the "new normals" reflect the impact of climate change.
"It’s tough to really argue that climate change is not playing a significant role in what’s happening here," Lanza said. "It's another arrow in the quiver to show that things are warming. And it's not just a one-day temperature, we’re looking at the whole climatology."
A climate assessment previously commissioned by the city of Houston found that the area will continue to see hotter days and nights, longer heatwaves and heavier rainfall if greenhouse gas emissions continue to rise.
The "new normals" also include rainfall data. In Houston, the average yearly rainfall increased by about 2 inches. August saw the biggest increase with average rainfall increasing by about an inch.
"It was a pretty substantial increase, and I think a lot of that is attributable to Harvey," Lanza said.
Galveston, on the other hand, saw a decrease in annual rainfall — by about 3.5 inches.
"Anecdotally speaking, we’ve seen that a lot in recent years, where the heaviest rains will be inland," Lanza said.