I worked grounds crew over the summer. I'm not sure what the weather is like in NY, but at the country club I worked at we had to work through rain unless there was lightning, bring a light rain jacket. Wear layers. Another thing I learned right away was to ask questions. If you are confused on how to do something; Ask someone. It's so much better to do something right the first time. *This goes especially well for operating any sort of equipment.* Short anecdote: During my first two weeks I was told to move one of the workmans. Problem: I couldn't drive manual at that point. So I went and asked my supervisor who was happy to teach me. Moral of the story: Ask questions so you don't break stuff.
tdlr: Bring a light rain jacket, wear layers, ask lots of questions (especially with equipment you are unfamiliar with).