In order to use it for firewood next winter you need to split it as soon as possible and store it in a place which gets exposure to sun and wind. Under your deck is probably not the right place. Most species of oak take a long time to season. I usually try to season mine for two years. It just has a lot of water in it. Splitting it into six pieces per section would help.

Good advice from nhyankee...I'll add my 2 cents...oak needs 2 years to season (dry out)to be really good. If you have room, split it as suggested and keep it in full sun, very loosly stacked. Cover it at the end of each day (dew) or when it's going to rain. The more sun and wind you let get to it, the better. If you do it now, you just might be able to use it in a fireplace this coming winter.

if you are going to split it by hand, you definitely want to do it now while it is still "green". oak gets hard when it dries and will give you a workout if you don't have the proper tools and knowledge to use them!

if you use a hydraulic splitter, you can split them later, but it will delay the drying. i have used oak after 1 year of seasoning, but it burns MUCH better the 2nd year.

Split it today, keep the air on sun on it and you can burn it late this year - If you dont believe this use a moisture meter on the splits and you will find your under %15 easy...even lower in the single digits. Of course this depends on your climate - times may vary

Invest in a wood splitting machine, I got mine off Ebay. It's so easy to use. Fun too!!

Buying a wood splitter for seven pieces of wood sounds rather disproportionate.

Pretty much any old axe ought to work for a small job.