The power ender "よ"

When you want to impress upon your listener the importance or truth of what you are saying stick a よ at the end of the sentence.

本当ですよ。　hontou desu yo. It's the truth, I tell ya! (Perhaps the speaker suspects the listener doesn't believe what he just said)

フロリダの１２月は暑いですか？　fururida no 12 gatsu wa atsui desu ka? Is December in Florida is pretty hot?

結構 寒いですよ。　kekkou samui desu yo. Actually, it is pretty cold.

It is very useful for rumors or explaining a truth you know someone may not swallow at first:

鈴木さんは宇宙人ですよ。　suzuki san wa uchuujin desu yo. Suzuki is an alien, you know.