The Movistar Yahama rider appeared to be cruising after Marc Marquez crashed on the 22nd lap, with Lorenzo holding a 1.4 second lead over team-mate Valentino Rossi.
However, Lorenzo was forced to dig deep as Rossi reeled him in, with scorching temperatures causing the Spaniard to lose grip in his front typre.
The 2012 World Champion was able to fight off the challenge of Rossi though, and took the chequered flag 0.885s ahead of the Italian.
"That was one of my hardest races, especially the last ten laps," the 28-year-old told reporters. "I was keeping this distance to Valentino who has been riding so well in these hot temperatures.
"It's been very difficult for me to repeat the pace of yesterday morning so much slower and less grip with the front tyre. I was keeping this 2.0 [second lead] but I was risking a lot and going at the limit. Suddenly in one lap he recovered me six tenths.
"I think by myself, 'Jorge, you have to push even harder.' Risking more, risking the crash. Normally I don't do this but today I had to. Valentino was getting more motivated to catch me and he would do it.
"The next lap I improve just a little bit more on braking and opening the throttle. I improve one tenth and the distance keep. So finally 1.2s at the end of the race this time has been enough to win the race but [it was] really, really hard. Harder than ever."
Lorenzo, who became only the fifth rider to win four consecutive races, added that he was pleased to have cut Rossi's lead on the standings down to just one point.
"It's just the seventh race but the championship is very close between us," he said. "Valentino almost always improves something on Sunday. He's a Sunday rider. On Sunday he gets much more victories than pole positions. He's much more strong, more constant.
"Luckily for me I'm also constant and focused. Today I had to give this extra risk more to not lose the race. It has been important to get this victory because today the bike was not the same as on Saturday like in Mugello or Le Mans or these tracks."