ESPN PGA Championship 2007

TULSA, Okla. -- The heat will be on this week at the PGA Championship.

And on. And on. And on.

Tournament officials and local authorities have issued an excessive heat warning for the week, with air temperatures expected to top 100 degrees throughout the tournament.

The heat index, which combines air temperature and relative humidity, is expected to reach 110, at least for the first two rounds.

First-round play begins Thursday at 8:30 a.m. ET (7:30 a.m. local time). Tee times continue throughout the day, with half the field playing in the morning and half in the afternoon on Thursday. The groups reverse times for Friday's play.

"Dealing with the heat is going to be of the utmost importance," Masters champion Zack Johnson said in a news conference on Tuesday.

According to the Daily Oklahoman, Southern Hills has hosted three of the five hottest major championships, at least according to average temperatures. The 1970 PGA averaged 100.3 degrees, while the 1982 PGA is fourth at 97 degrees and the 1958 U.S. Open is fifth at 96.6 degrees.

The 1963 PGA Championship, at the Dallas Athletic Club, averaged 99.3 degrees, according to the paper. The 2005 PGA at Baltusrol, won by Phil Mickelson, averaged 98.5 degrees.

Johnson said he was curtailing some of his practice to avoid the heat.

"It's going to be really hot every day, so it's going to be not only a test of golf but also a physical test and a mental test," Johnson said.

Boo Weekley, playing in his first PGA Championship, had one suggestion for beating the heat.

"Walk in the shade, I guess," Weekley told the Daily Oklahoman.