I don't think anybody knows what the weather will throw up.
I know that many people think that Hamilton will win this and I will probably go along with that, but surely, in unpredictable weather conditions, Button has to be in with a decent shout.
Remember, if Hamilton needs to make a strategic decision, he will leave it up to the McLaren team. Historically, we have seen that McLaren are abysmal when it comes to making decisions, which could cost Hamilton the race. Conversely, Button has shown in the past that when conditions are unpredictable, he tends to profit, rather than lose, from the situation. Of course if it dry, then Button is unlikely to get a look in.
[I remember, when F1 was on ITV1, James Allen used to say that McLaren employ some very intelligent people to make these strategic decisions, who have access to all sorts of computers and gizmos. If this is true, then seriously, McLaren need to sack the whole bunch of them and use coin tosses to make their decisions (for free), as this will be a cheaper method to make decisions and is likely to yield better results].