PITTSFORD, N.Y. — Well before daybreak on Thursday, Stewart Williams joined an urgent discussion in a small second-floor room at Oak Hill Country Club, near the nation’s northern border. The night had brought cool temperatures, clear skies and gentle winds — and that was a problem.Frost was thickening on the golf course and, less than two hours before the P.G.A. Championship’s scheduled start, the tournament’s top official needed to know when it would melt. For the moment, one of the world’s most prestigious golf tournaments would be shaped not by the athletic genius of a Rahm or a Koepka or a McIlroy, but by the instincts and data of a meteorologist from High Point, N.C., who barely plays the game.By midmorning, with competition underway at last, Williams was thinking about the next hazard: a front that threatened to drench the course during Saturday’s third round.“Nobody,” he mused in the sunlight, “was focused on the rain until the frost moved on.”But there are few sports that focus on the weather like golf, and few that rely as much on meteorologists who travel to venues to assemble pinpoint forecasts. Local television stations and weather apps may offer forecasts for vast regions; specialists like Williams, who has spent the better part of three decades around golf courses, are building outlooks for areas of just a few square miles.At a popular event like the P.G.A. Championship, his predictions may not affect the tournament as much as the rule book, but they will influence course agronomy and pin placements, television broadcast preparations and emergency planning. A 350-acre property with relatively few shelters, organizers often note, takes much longer to evacuate than most places.“When you see a red line that spans about 400 miles north to south, it doesn’t take a rocket scientist to see that it’s coming,” said Sellers Shy, the lead golf producer for CBS, which will air weekend rounds and keeps a weather map in its bank of production monitors. “But their technology and their expertise literally gets it down to how far away it is, as well as when it will arrive and when the horn will blow to within five minutes, probably.”Shy uses the forecasts to plan for interruptions in play — there is still airtime to fill, whether or not someone is trying to escape Oak Hill’s rough — but Kerry Haigh, P.G.A. of America’s chief championships officer and the man who so desperately needed to know the timing of the frost melt, relies on them for course setup, shifting his thinking about tee and hole locations to accommodate conditions over a 72-hole tournament.“You almost can’t do without them in running any spectator championship, or really any golf event,” said Haigh, whose desk at Oak Hill is essentially a putt away from Williams’s, where the forecaster toggled his laptop screen among maps, models and charts.Outside, next to a wading pool, a battery-powered tower Williams had erected was aloft, detecting electrical charges that could give just a bit more warning before lightning, the greatest concern at a sprawling golf tournament, strikes. An anemometer spun at the top.Golf executives have yet to find a convenient locale with a guarantee of perpetually sublime conditions, and tournament histories are thick with disruptions that some experts believe will become more common as the climate changes. Last year’s Players Championship concluded a day late because of miserable weather in Florida, much like this year’s Pebble Beach Pro-Am in California. In Augusta, Ga., in April, the Masters Tournament dodged its first Monday finish since 1983 — but it had to squeeze the end of the third round and the entire fourth round into Sunday. And the 2018 P.G.A. Championship had Friday play upended when electrical storms pounded the St. Louis area. The next year, six people were injured after lightning strikes at a tournament in Atlanta, where fast-developing thunderstorms are a summertime trademark.Oak Hill Country Club, in a suburb of Rochester, is no place for an entirely predictable forecast, especially in May, when the region’s weather patterns are in transition. The nearby Great Lakes add to the puzzle since they can inject moisture and unusual winds. Williams covered the 2013 P.G.A. Championship at the club, an experience that was only so valuable this time around since that tournament unfolded in August.For this year’s event, he began closely studying the region’s weather tendencies about a month ago, noting which forecasting models seemed more accurate than others in the area. He also examined historical trends.“You’re always trying to stay in tune with how do the data sources behave at the site you’re at, so you can understand tendencies and bias that helps alter how you forecast,” said Renny Vandewege, a vice president at DTN, the weather company that employs Williams and works with the PGA Tour, the L.P.G.A. and the P.G.A. of America. (It is not always a private sector endeavor; Britain’s national meteorological service, which is under contract with the R&A, sends forecasters to the British Open.)The influx of data, Williams and Vandewege said, helps, especially with technology that has rapidly improved in recent decades and models that now yield projections every hour. The human element, they insist, matters, perhaps more than ever in an era of easily accessible weather data.“For us as meteorologists, I look at this model, and then maybe I look at a different one — it may have this further east, having everything arrive faster,” Williams said as he sat next to Vandewege and weighed the approaching storm system. “That’s when you start using your instincts.”Tournaments vary in the number of official forecasts they issue on a daily basis, but players and caddies pore over them once they hit inboxes and are posted at the first and 10th tees. Some routinely approach Williams seeking even more specific details for the days ahead, and the course superintendent is always looking for projected evapotranspiration rates, or how much moisture leaves the grass and soil. Davis Love III, Williams said, also liked to ask what to expect for his fishing trips.“You’re not going to not look at information that they’re giving you,” said Collin Morikawa, a two-time major champion, who figured nearly every player also had two or three weather apps close at hand.“We look at everything,” he said. “I think you have to take everything into account.”Others, like Haigh, try to avoid a torrent of forecasts. Whatever Williams predicts, they say, is what will principally guide their thinking.“They are the professionals — that’s what they do week in and week out, and they’re very good at it,” Haigh said. “They have better and more high-tech equipment than I certainly have on any apps.”The frost melt forecast was right on time.