The midday temperature on the Stadium Court at the National Tennis Center was approaching 120 degrees, and to 5-foot-6 Harold Solomon, Ivan Lendl looked like a Towering Inferno across the net.

Nothing quite like this had ever happened to Solomon, who has made a career of exhausting opponents.After winning the first game and having chances in the second, he was tired. His feet seemed planted in the asphalt court.

Lendl, the powerful, 6-foot-2 Czech who has risen to No. 9 in the computerized world rankings, was smoking the ball in the sweltering heat, missing nothing. He ran off 18 games in a row to devastate Solomon, 6-1, 6-0, 6-0, and reach a quarterfinal meeting with defending champ John McEnroe in the U.S. Open.

Solomon had beaten lendl, 6-1, 6-1, in their only previous encounter, on a hard court in Las Vegas in April.

"It was something like this match, only he was on top all the time, and I was down," remembered Lendl. "When I got on the top today, I just said, 'okay, let's go and go and kill the guy, because he is not playing that well.' I didn't let him to do anything."

Solomon, who came into the Open off, a tournament victory in Cincinnati, was asked if there were any extenuating circumstances to the worst dribbling of his pro carrer.

"no. After about the second game, I just didn't feel I could move my feet too well," he said. "He hit the ball very well, very deep. I just didn't feel like I had any get-up-and-go out there today. I got up and went.

"i usually don't mind playing in weather like this, but after awhile it seems to start taking a toll on me. It was hot in Cincinnati, too. I felt good when I hit yesterday, but I didn't have any energy today."

It should be an interesting match Thursday night when McEnroe, a 6-2, 6-4, 6-2 victor over Frenchman Pascal Portes today, plays Lendl, one of his rivals for international junior tennis supremacy three years ago, who has not lost a set in four matches.

"I want to win that because he's one of the few guys in the top 10 who's younger than me," said McEnroe, 21.

McEnroe's nose was sunburned to a bright scarlet, but he was pleased with his play. He was jumping into his serves and smashes off his left ankle, which was tightly wrapped to protect against aggravation of a recent sprain.

"i think I picked up definitely from my earlier matches. I concentrated better -- especially considering how hot it was," said McEnroe, who received one misconduct warning.

If he can get past Lendl, McEnroe seems destined for a return match of his acrimonious Wimbledon semifinal against Jimmy Conners, who turned 28 today.

Connors tonight struggled more than in his previous three matches, but defeated Bernie Mitton, 7-6, 6-4, in a match that was delayed 53 minutes in the second set by light rain squalls as a violent thunderstorm passed nearby.

In the third set, there was a momentary interruption as two bats swooped around the stadium, landed in the doubles alley, but were rousted by an intrepid ballboy and took off like -- well, like bats out of hell. Conners played that way when he was behind, coming from 1-3 down in the second set and from 2-4 down in the third to win them.

Connors will play Eliot Teltscher, 21, another junior rival of Lendl and McEnroe, in a quarterfinal on Thursday. A slender, 5-10, 140-pound Californian with a flyawary shirttail and more grit than grace in his game, Teltscher today ambushed Wimbledon semifinalist Brian Gottfried, 6-4, 6-2, 6-1.

Wednesday's men's quarterfinals will pit Bjorn Borg against Roscoe Tanner and Wojtek Fibak against Johan Kriek.

Andrea Jaeger, 15, and Argentinian Ivanna Madruga, 19, became the fourth and fifth teen-agers in the women's singles quarterfinals.

The spunky Jaeger -- flying around the court like a goldfinch in an outfit as yellow as her streaming, waist-length pigtails -- tired out Renata Tomanova of Czechoslovakia, 6-3, 6-0.

"I think the weather is an advantage to me because it takes a lot to out-hit me every point. I figure my opponent will get tired," said Jaeger, who covered practically every one of tomanova's frequent drop shots and moved the ball around superbly, seizing control of the rallies. "I'm a lot younger and more used to the heat than a lot of players."

Jaeger next will play Madruga, who wore down Candy Reynolds with her heavy top-spin ground strokes, 5-7, 6-3, 6-3. California net-rusher Barbara Hallquist-who is ranked No. 103 on the women's computer and got into the Open without qualifying only when Heidi Eisterlehner withdrew-beat Romainian Lucia Romanov, 6-3, 3-6, 6-3, and reached a quarterfinal meeting with 18-year-old Czech Hana Mandlikova.

The top half of the womens quarterfinals also will be played Wednesday: defending champion Tracy Austin, 17, against Pam Shriver, 18, and 1975-76-77-78 champion Chris Evert Lloyd against Mima Jausovec of Yugoslavia.

Shriver, the Great Whomping Crane from Lutherville, Md. who was the youngest finalist in the tournaments's history in 1978 and a discouraged first-round wipeout with an aching shoulder last year, practiced on the stadium court between the afternoon and evening sessions today.

Asked after beating Australian Dianne Fromholtz on Monday what she would do today in preparation for Austin, the junior rival against whom she is 0-10 but has not played in 19 months, Shriver said she would get up, have breakfast, practice, play her doubles, hit for another half hour, "then have a reasonalble evening, get to bed early -- and dream about beating Tracy."

Shriver also recalled, "I haven't played on the center court since I played Chris in the finals two years ago. so it will be nice to get out there again. I have a lot of nice memories out there."