Thousands of Palestinians stranded in Egypt rushed to the border on Tuesday which EU monitors said would be open for up to 11 hours.
Only “humanitarian cases” travelling in one direction, from Egypt to Gaza, are allowed to cross, the monitors said.
The Rafah crossing has been closed since Palestinian militants seized an Israeli soldier on 25 June.
Palestinian student Heba al-Qaysi, 21, was among an estimated 2,000 people waiting to cross.
She told the Associated Press she had gone to Egypt to renew a visa for Saudi Arabia, and had run out of money and been reduced to sleeping in the open after she was stranded.
Several people have been reported to have died from heat exhaustion during the wait for the border to re-open.
The Rafah crossing is Gaza’s only gateway to the outside world.
It was controlled – and often closed – by Israel until a 2005 agreement under which Palestinians control the crossing under surveillance by EU monitors.
But since the June raid by Palestinian militants, which sparked a major Israeli military operation, the terminal has been closed.
Israel has stopped it opening by preventing the EU monitors from getting to the terminal, citing security concerns, western diplomats told Reuters.
Palestinian official Hany Jabour told the Associated Press that Israel had imposed the one day time limit.
But the Israeli Defence Ministry told the news agency a decision would be taken on Tuesday evening on whether to keep the border open indefinitely.
On Friday Palestinian militants blew through the wall between Gaza and Egypt, allowing hundreds of Palestinians to return to their homes in Gaza.