France - Least expensive time to fly?

I'm in Washington, DC and would like to take a quick trip to Paris (first time), check out the old cemeteries (weird I know, but they're so beautiful!) and some other must do sights, chow down, and come home. Generally when is the cheapest time of year to fly?

Merci beaucoup!

Off-season winter Nov. or Jan. - Mar. but see if you can work it so you leave right at the end of low season and still get a lower price while getting decent weather.

Usually end of fall, most winter (except 12/15 to 1/5 or so), and January through early March.
It varies greatly and some weekends may be more expensive than others.
I think Paris is great any time of the year and actually cemeteries may be "kooler" during rainy stormy days.
Flying Tuesday or wed is usually cheaper than over the weekend.
If you are not "married" to a frequent flyer program then I would definitely shop around; if price is your main motivator then go with some of the websites like orbitz, travelocity, kayak or google flights
Also I would recommend to keep checking back since prices may drop at anytime.
I never know when is the best time to buy a ticket so I decide ahead of time how much I am willing to pay and then when I see that price I buy and NEVER check again. I don't want to know since the changing fee is $300 or so the price needs to drop a lot for it to be worthwhile to change the ticket.
I would also look at your local Sunday newspaper; they usually have little ads of wholesalers; the main problem is that many of those flights do not earn miles and cannot be upgraded to business or first class but if you are not obsessed with miles (like some people I know) then it does not matter to you.
Good luck and enjoy.
Let me know if you need any recommendations for Paris; it seems like you know the place.

Don't miss Pere Lachaise. It really is great. People look at you funny when you say you loved visiting a cemetery, but... Pere Lachaise is special. My favorites were Oscar Wilde and Edith Piaf.