I am a disaster relief and evacuation worker, so if anyone has any specific questions, I can do my best to answer them from a somewhat educated point of view.
I'm surprised no one has mentioned MREs yet. MREs come in 4 vegetarian varieties that I know of, plus many more vegetarian side dishes and snacks in the meat entree packs. They aren't very good for vegans though there are some vegan snacks and side dishes, and one entree that might be vegan (I haven't read the ingredients). Humanitarian Daily Rations are entirely vegan, but they are much harder to find and purchase, and a lot more expensive.
Unless you just can't afford MREs, in my opinion there is no other food really worth having on hand for evacuating or waiting out a storm. MREs have a shelf life of a decade or more, contain toilet paper, plastic spoons, water resistant matches, and laxative gum, are inpenetrable by water, taste pretty good, contain 1200 to 1500 balanced calories in one meal, and are self-heating. You just need water to activate the heating pouch. *Remember, DO NOT use a propane stove in an enclosed space.* There's nothing like a hot meal when you're sitting in evacuation traffic and haven't slept in 30 hours.
I had cases and cases of MREs that were my rations when I worked for FEMA last year, and I had my husband come down in his truck to Opelousas, LA where I was stationed and pick them up and take them back to Dallas. But if you don't have a friend or family member with FEMA or the military, you can order them for $3 to $6 per complete meal and less for individual dishes and snacks. Just Google MRE.
Of course this should really go for all year round, but since it is now officially hurricane season, ALWAYS keep your gas tank full. Fill up once or twice a week, even if it's just topping off. Ice, water, and gas are the first three things to run out in an emergency situation and are the most difficult to replenish. The next tip I am going to put in all caps as I feel it is extremely important.
IF YOU ARE EVACUATING, ALWAYS CARRY EXTRA GAS WITH YOU.
I'll put it this way: if you're carrying gas, there is a very slight chance that your car could explode or you could pass out from fumes. However, in an evacuation situation, it is almost 100% certain that you WILL run out of gas and the gas stations will too, and you will be stranded in a potentially dangerous situation. Last year, two disabled people whom I was evacuating almost died because I did not bring gas with me and we were stranded for 13 hours. That's how I know.