The simple answer is that with a well maintained modern car, rain should not cause any problem. That said, you obviously do have a problem, so...
The two traditional paths to follow in this situation are spark and fuel.
Spark - are the sparkplugs firing? Best checked with a capacitive tool you clip around a plug wire but it sounds like you might not have something like this. You could also pull a plug wire and hold it off the plug a little with a dry rag (to avoid a nasty shock) and see if it sparks while someone else cranks the car. However, the design of the boxster engine is going to make this difficult to do as the plugs are way down between the cams, see
this diagram.
If the other end of the wire can be pulled at the distribution end, you may be able to check there.
Absent any of the above, you could simply check for loose wires and trapped water.
Fuel - you did check to be sure you have gas, yes? You may want to try a small amount of starting fluid (available at AutoZone, etc.) sprayed into the air cleaner inlet to see if that gets the engine to fire. If so, you problem is fuel related.
No matter what, I expect you will be late to NYC or have already left in someone else's ride. Hope it turns out to be a minor issue with your car.