Depends what part. I live in the south. Summers are hot - 30+ degrees. Never known to rain June - August. Heavy rain sometimes November to January, but everything soon drys out. No frosts ever. North similar to S. of France - nice summers, frost and snow a possibility in Nov. - Jan.
It varies.
It can be freezing, very cold, cold, quite warm, very warm, hot, very hot or very very hot. It can rain too. And snow. Oh, and be foggy and even windy.
It depends whereabouts in the country you are and what time of year it is, just like in most countries !
never been there but hopefully going next year..id imagine it would be similar to spain...very hot july and august, good way to find out is to look up a travel brochure or simply type in portugal in your search..cheers, have a good holiday.