"И", as a particle, is usually placed before the verb and has multiple meanings.
One common translation is "that's/it's ..."
Это меня и удивляет. = That's what surprises me.
Я и есть причина всего происходящего. = It's me who's the cause of
what's happening.
Я не зна́ю, поэ́тому и спра́шиваю. = I don't know — that's why I'm
asking.
Похо́же, всё к э́тому и идёт. = Looks like that's where things are
headed.
вот и всё = That's all there is to it.
"так и" is a common combination meaning "that's how..."
Я так и сказал. = That's how I said it.
Он так и де́лает. = That's
exactly how he's doing it.
Yet another meaning is "This may come as a surprise to you, but..."
А он и не приходил. This may come as a surprise to you, but he never
came.
Я и не собирался это покупать. = This may come as a surprise to you,
but I wasn't going to buy that in the first place.
Finally, "и" is part of several other grammatical constructions. In your example: ну... и... = What a... !
Ну и погодка сегодня. = What [bad] weather we're having today.
But you should refrain from using "ну и" in that meaning because it's actually not a very flexible construction. Besides it can mean other things too.
Ну и плевать. = I don't care, then.