Don't let the "poetic" part of Hardy's style scare you. This novel is, at times, funny, clever, and very real to life. However, Hardy does enjoy a bit of heightened language. It fits perfectly with the emotional temperaments of Jude and Sue. They are characters who can get on a roll when expressing their love for each other or when debating a lofty subject.
Things get pretty poetic (though not in the literal sense) pretty early on. When Jude starts to feel as though he has no place in the world at a young age, this is how Hardy lays it down:
Jude went out, and, feeling more than ever his existence to be an undemanded one, he lay down on a heap of litter near the pig-sty. (1.2.39)
See, that's both poetic and funny: Jude feels like there's no reason for his existence. So, as he mopes around, he decides to lie down in the trash near the pig-sty—a plan that's sure to help him feel even more miserable.
The fiery side of things really gets going when Sue shows up. This is a character who loves to rip apart subjects and try to get to the core of them. She doesn't tolerate conventional explanations for how things are; she questions them. Questioning, for Sue, often leads to a bit of rage or at least fire in her speech:
'I hate such humbug as could attempt to plaster over with ecclesiastical abstractions such ecstatic, natural, human love as lies in the great and passionate song!' (3.3.79)
This is just a small taste of how Sue can light into a subject that is important to her: she speaks in italics in a book whose narrator avoids that kind of obvious emphasis. It's not that she has a bad temper. It's just that she feels a lot of passion for a lot of things. Her speech comes to dominate the style of the book in those scenes in which she has a major part, because whether she is with Jude or Phillotson, she spends much of the time leading the conversation and the action.