"Rainmaker", a short story by John Reese; originally published in the February 19, 1949 issue of The Saturday Evening Post, available at the Internet Archive; reprinted in the anthology Tomorrow, the Stars edited by Robert A. Heinlein et al.
The story is set in Southern California in the late 1960s. Bill Lawson is a licensed professional rainmaker:
Things had changed a lot since scientists first seeded clouds with pellets of dry ice, making them discharge their moisture in the form of artificial rain, twenty-odd years ago. Bill was a kid of eight when he watched a little cub plane make three passes at a cirro-cumulus formation over a grass fire in the Santa Monica Mountains, just about the time the Japanese surrendered—some time in the middle forties, anyway.
It didn't work, and the fire burned itself out, but the kid of eight knew what he wanted to be when he grew up. A rainmaker. Now, at twenty-eight, William Lawson had held California Precipitation Permit No. 1 for six years, ever since the state started granting them under the Supreme Court decision.
The permit meant he was a skilled airplane pilot. It meant he had two years of college meteorology. It meant he could tell you at any given time what crops were in what growing stages, and where. It meant he could tell you, without looking at the charts, each of the two dozen two-day to five-day periods during a hot, dry California summer when a rain would do a lot of good for everyone and harm to no one. Charts? He had written most of them himself.
After completing his deliveries to the area farmers, he buzzes his girl friend's house, where his rival, the obnoxious and rich Jerry Rudd, is visiting:
"Why did I bother to apologize?" he grumbled to himself. "A man only makes a fool of himself when he does that."
He was over Rosemead Airport, but his own rain was still raining there and it was an excuse for not going in. He crossed Los Angeles and Hollywood and Cahuenga Pass, and gave Sid his last observations. Not that he had to, but he liked to do his share in filling out Sid's maps. The fact that his sweep brought him over Patty Vernier's house was strictly coincidence.
A lot of good stuff had collected over the San Fernando Valley—not heavily, but in patches, thanks to those two disturbing cold barriers he had precipitated. Studio City, where Patty lived, was obscured. On impulse, he slanted down and crossed her house at three hundred feet, both engines running.
At this level, he could see clearly. There was Jerry Rudd's big red convertible, parked familiarly in the driveway. There was Mrs. Vernier, hanging out her washing, and Jerry was helping her. Jerry was very democratic at all times, of course. What fun a millionaire had, helping his inferiors with their chores! Bill gritted his teeth.
He gives Jerry a soaking:
He went back to Van Nuys, turned, and tripped the trigger of his last magazine as he crossed the valley toward Cahuenga Pass, slowly. He went up and stayed there awhile, chuckling and ignoring the frantic buzzing of his phone. Patty had a sense of humor. Patty would see the joke. Patty was on his side again! He felt good. He'd get some sleep and call her later in the day, and they'd laugh together over how it looked from down there.
From up here it looked good. He had hit it hard, and what moisture there was in the formation came down hard and sudden. It cleared up enough, in ten minutes, for him to see plainly through his binoculars.
There was Mrs. Vernier, in person, galloping toward the house with the last of her starched white linens, getting them in, of course, just as the rain stopped. She'd have to starch them again—perhaps even wash them again. He hoped.
There was Jerry Rudd, in sodden white flannels, letting Mrs. Vernier rescue her own wash, while he set a new record getting the top up on his convertible. He was quite a boy at hanging out laundry, but not so good at getting it in. Bill might have some explaining to do to Mrs. Vernier, but so would Jerry. After all, he ordered the precipitation.