To beat the cold while knocking on the door for candy, hitting the bar or celebrating at an outdoor party, costume designer Hester Michael of Hester’s Designs in the San Francisco Excelsior neighborhood warns people to choose a costume that “will keep you warm.” or find a base layer to wear under a strappy fit.

“A gorilla suit might keep you warm,” she said. “I remember my mom making us wear sweaters under our suits, and that was horrible.”

So far this year she has created a yellow motorcycle look similar to Kill Bill, a family of characters from the Hot Dog on a Stick store stalls and a Scream mask with kitten ears. She said people can get chilly on a cold night even when fully clothed, and recommends “fluffy lined tights that look like you’re wearing tights, or you can wear thermals as tops, leggings and bodysuits.”

Marty Van Der Vert, owner of the 38-year-old family-owned One Stop Party Shop in San Francisco’s Noe Valley neighborhood, doesn’t think “people worry about” the cold or the rain and will dress however they want.

“They could use cloaks or capes to cover themselves,” she said. “I also have every mask from every movie you’ve ever seen. I have (Michael Myers from) Halloween, but I think I only have a few of those guys left. You name it. I have it.”

Temperatures will peak in the 50s in most places over the next few days, according to Flynn.

“That’s pretty low for a high temperature, and by the time the trick-or-treaters come out, it will cool even further,” he said.

“Last week we were about five degrees above normal; this week it will be about ten degrees below normal,” Flynn said.