What is the best way to deal with a 2.5 year old throwing tantrums, especially in public? Will this be a phase that will pass?

Give warning at home first. Than reward them if they did well.. If on the verge thier tantrums is coming, lightly remind them the promise they made at home. And if exploded in the public, bring them out of the scene and talk or scold them behind some where no one can see or hear In case being judge. Haha. Have to be firm and not give in because you think your face in public is at stack and give in to them. Don't give in. They will know. If they do, it will become a habit to them or they caught your weak spot.