Move over, Beyoncé, Houston has a new celebrity: Jeff Lindner, meteorologist for the Harris County Flood Control District.

As Tropical Storm Harvey inundated the greater Houston area with as much as 51 inches of rain over the past week, Mr. Lindner, 35 years old, has been a reassuring voice in a near-apocalyptic disaster, calmly updating millions via televised news conferences and Twitter posts about rising water levels in bayous and reservoirs.

To the multitudes worrying about whether floodwaters were inching closer to their homes, Mr. Lindner, with his blue button-down shirt, government lanyard around his neck and disheveled, close-cropped hair, has become a no-nonsense hero.

“What we’ve been thankful for in Jeff Lindner is that he’s giving us straight answers, whether we like them or not,” said Emma McGarity, a 50-year-old secretary.

She said she decided to evacuate her home in Charlestown Colony, just north of the overflowing Addicks Reservoir, Monday on Mr. Lindner’s advice, even though her home had never flooded before. She returned Thursday by boat to find 6 to 8 inches of water inside. “Lindner saved me from having to be evacuated by boat,” she said.

The devotion of some Houstonians to Mr. Lindner has reached unexpected proportions. Noticing that he hasn’t been able to break from his work, one started a GoFundMe account on Thursday to finance a vacation for Mr. Lindner. By early Saturday, it had smashed its $4,000 goal, garnering more than $17,000 in donations.

On social media, where Mr. Lindner has become a sudden star, answering questions on which streets and neighborhoods were flooding well into the wee hours, some went further.

Calling Mr. Lindner her “new crush,” one Twitter user wrote: “Love me a smart man who is steady in a crisis.”

Mr. Lindner, a married father of two, said he was taken aback by all the attention.

“I just feel like I was doing my job,” he said. “I’m going to keep doing it.”

As a government employee, Mr. Lindner can’t accept gifts over $100, so he said he would like the vacation-fund money to go to flood victims.

Mr. Lindner, who earned a degree in meteorology at Texas A&M University, started at the Harris County Flood Control District as an intern in 2003 before coming on full-time a year later.

As Harvey pummeled the Harris County region, which includes Houston, Mr. Lindner said he snatched short stretches of rest in an office chair tucked away in a backroom at Houston TranStar, the emergency operations hub from which numerous agencies have coordinated storm-response efforts.

But his personal experience with flooding—Mr. Lindner’s house took on 3 feet of water during Tropical Storm Allison in 2001—always pushed him back to the computer screens on his sticky-note-covered desk, from which he could hear 911 operators responding to emergency calls.

“I couldn’t go to sleep knowing there was information I could be providing,” he said. “I tried to get as much warning to people as I could.”

That dedication sent thousands to Mr. Lindner’s Twitter account, @JeffLindner1. Three weeks ago, he had 2,400 followers; as of early Saturday, he had more than 16,000, including an account with the handle @JLindnerFanClub.

Eric Berger, editor of the Space City Weather blog—another oasis of calm for Houstonians seeking hype-free forecasts—said he wasn’t surprised to see people take to Mr. Lindner as they rode out Harvey. Mr. Lindner’s willingness to crunch and share flood data, he said, had long ago earned Mr. Lindner the admiration of the local meteorological community.

“It comes down to trust; you trust him to give you an honest answer,” Mr. Berger said. “It’s clear he works very hard, and that’s something that’s easy to respect.”

Write to Erin Ailworth at Erin.Ailworth@wsj.com