After you’ve prepped your food and water, the next most important thing to organize is your shelter, including sleeping arrangements.
Plastic tarpaulins will be invaluable here. Large, plastic sheets can be used in several different ways; tie them up to create tent-like shelters, or use them to create highly effective water collectors. If you want to use tarps to create a shelter, then remember to take a ground sheet as well as one to use as a cover; too many people forget a ground sheet and end up with cold, wet, dirty, bug-infested belongings! Don’t pack a tent: tents are so much heavier than plastic tarps, and they’re much less versatile.
In a similar way, pay close attention to what you pack in terms of bedding, as certain items can be used for more than one purpose. It’s true that sleeping bags are very warm, and you might even be able to find one that’s waterproof, but you should consider swapping your sleeping bag for blankets. If possible you should pack both, but if you’re hard pushed for space and weight, think about which will be more useful in a wide range of situations.