An unusually high number of bees have been swarming neighborhoods near San Francisco, and experts say the abnormal weather is to blame.

"They're feeling the joy of spring like we all do," Mike Stephanos, vice president of community education for the Mt. Diablo Beekeepers Association, told ABC News. "That's just their natural instinct. They can't fly when it's raining, and they don't like flying when it's really, really cold."

Spring came early this year in Concord, like much of the United States, causing the bees to come out of the hives for the longer and warmer days.

In Concord, 30 miles east of San Francisco, thousands of bees swarmed a car until a young boy in a beekeeper suit gathered them. Just last weekend in another part of town, a local beekeeper pulled a whole hive out of a barbeque grill.

Concord resident Shelley Keho told ABC affiliate KGO, "I'm giving them their space, absolutely. I had three of them fly right into my face yesterday at the back of my car, so I said that's O.K. I got your message."

Experts say while the early swarming is from the arrival of warm weather, the size of the swarms were mostly caused by the on-and-off-again rain. During the cold months, the queen bee and the colony gather in the hive to lay eggs to expand the population. When warm weather arrives, the queen bee's natural instinct is to leave with half of the colony to find a new home.

"Sometimes they get so crowded in the hive-it's called honey-bound. There's not enough room for them to grow," Stephanos told ABC News.

However, the turbulent weather has made the colonies return to their hives more frequently before finding a new home, and as a result, the swarms have grown in size.

"Right after the rain there's an explosion of swarms because that's their opportunity," said Stephanos. "Sometimes they land on cars or any temporary location and send out scout bees for new locations. If there's a hole that's comfortable for them to grow, they'll go in there. You name it."

Even with the slight increase, Stephanos says there's no need to worry.

"If you don't bother them, they don't bother you."

Yet, some residents still say 40,000 bees in one swarm is enough to keep them on edge.

"I was painting on the side of a building, and I noticed a lot of bees around the building as I was painting. I don't like bees. I don't like anything that can fly and attack me at the same time," Concord painter Mike Tomasik told ABC affiliate KGO.

Experts say if there's an unwanted swarm, residents should call a local volunteer, which can be found on the Mt. Diablo Beekeepers Association's website.