Beijing Olympic gold medalist Dementieva, who has never made it past the fourth round at Melbourne Park before, outclassed the unseeded Carla Suarez Navarro 6-2, 6-2 in temperatures upwards of 39 degrees Celsius (102 Fahrenheit).
"It was very tough to play because of the weather conditions," the 27-year-old Muscovite was quoted on the tournament website as saying after the game. "Also, I mean, she is very strong physically, you know, a very fit player. Playing for the first time, I didn't know what to expect from her."
Dementieva questioned the heat policy at Melbourne Park with temperatures soaring to over 40 degrees Celsius (105 Fahrenheit) the roof over the center court was not used until the second quarterfinal match.
"I think when it's over 40 [Celsius] you have to close the roof. But saying that our match was like 39 and a half ... when you're on court it feels 45 inside," Dementieva said.
Many tennis commentators are tipping the fourth-seeded Russian, who will face second seed Serena Williams in the second semifinal, as the favorite to lift the trophy.
Williams, who is chasing her fourth Australian Open singles title, defeated eighth-seeded Svetlana Kuznetsova in a hard-fought match that saw the Russian serving on match point in the second set before the American broke back to take the set and then the match 5-7, 7-5, 6-1.
When asked about her upcoming semifinal match, Dementieva said "Well look, every time it's different, especially against Serena."
"All the last three matches were completely different games. She feels pretty comfortable playing, you know, on this surface," she said. "I think it's going to be a tough match."
Russian No. 3 and No. 7 seeds Dinara Safina and Vera Zvonareva will face each other in their semifinal match on Thursday. Zvonareva, who has yet to drop a set in the tournament, holds a head-to-head advantage, having won the last three encounters.
Dementieva has also come out on top in her last three matches against Serena Williams, including a win at the 2008 Olympics and another earlier this month.
Williams talked about Thursday semifinal match after her win, "I think she's [Dementieva] playing amazing. I think she's actually playing some of the best tennis on the tour. She's really stepped up the level of her game to an unbelievable level. I'm going to have to play really well to do well tomorrow."