Over the years of helping with several hurricane, tornado, spring floods disasters in Texas, Oklahoma, Louisiana, Mississippi, Arkansas, etc I've learned the very best thing a person could do is donate money.
As an example. A person might thing going to the store and buying $30 of bottled water to donate to a charity organization would be helpful. It is. The person might get six or seven cases of water.
However donating the same $30 to the Red Cross is going to get approx 18-20 cases of water for the relief efforts.
Major companies sell clothes, food and construction components to relief organizations at the cost of transportation. A company like Walmart can sell 20 truckloads of bottled water to the Red Cross - and 'make' more money for their yearly net-profit on the tax writeoff than they would on selling 20 truckloads to people to give to the Red Cross.
Gifts of not needed items like clothes are seldom useful for disaster victims. They need to be sorted, cleaned/washed, stored, transported, etc. Most such donations actually end up in local thrift stores near the donation point. Money from the sales of the items is used to buy new items from major companies like Target, etc.
You would be surprised how many people want to donate used underwear, and want the receiving organization to give a receipt for the full current new value of the clothes.
The issue with donating non-perishable food is (1) organizations have to spend a lot of manpower to hand sort the food and are required to discard any out of date items; (2) transportation is expensive, including costs to pack the food.
Please consider cash donations rather than left-overs.