June weather.

It will be good. Might rain, though. Dunno.

use this site for any city that tracks weather and has historical averages:
http://www.accuweather.com/

We had mostly gloriously warm, sunny blue-sky weather in London and Paris the second week of June 2015. We were told the week before had been miserably hot, in the 90s. We had not a drop of rain, but when we day-tripped to Normandy in gorgeous weather, we saw puddles from the previous days torrential, can't-see-10-feet-in-front-of-you rain. The evening of our Seine River cruise, we were wearing practically every layer in our suitcase and were chilled to the bone.

Moral of story: It's weather. Who knows? think layers, layers, layers. Lots of light layers.

Assume warm -- prepare for rain and cold. I would have a rain jacket and a polartek or cashmere sweater to layer under it for a cold evening.

Look at a live weather forecast for Paris two days before you départ.
Good idea to have a lightweight windbreaker - you can add layers underneath if needed.

It's a good idea to check the weather before you depart, but certainly pack a waterproof jacket, just in case.
We were in Paris last June and experienced some cold & rainy days.

If you plan to go up the Eiffel Tower, do book your tickets now, otherwise you may have to wait in a possibly long queue!

Enjoy your time in Paris!