Adam Geoffrey remembers the "flood" of people that showed up at his hardware store after the last series of El Nino storms.
"The parking lot was filled up and everyone wanted sandbags," said Geoffrey, "and they were too late."
Hammer & Nails Ace Hardware in Pacific Beach and other hardware stores ran out of bags before the rains ended. Even free bags offered by local cities and the county were gone.
Erica Roman works at the hardware store and was surprised by the heavy rains backing up in her backyard.
"It turned into a lake and came in through the living room door," said Roman.
Friday, hardware stores had plenty of bags, as do many fire stations and lifeguard stations. Some offer only bags, while others had bags filled with sand.
But you don't want to put too much sand into the bags. Road crew workers say you want to fill bags with sand or gravel a little more than half way so they can still settle and work together to block rising water.
But where can you get the sand? Some people fill their bags at the beach.
"I don't think you're allowed to," said Roman, "I'm pretty sure it is illegal."
Bags cost around 50¢ each when you buy them in bulk. At that price it's wise to stock up on a few before the rains come.