According to a spokesperson with the Contra Costa Fire Protection District, the fire was being mopped up as of 3 p.m.
The agency says it was started by a lawnmower and is asking residents to be more careful.
Temperatures in the area topped 100 degrees Sunday.
#BREAKING: A fire burning near Alhambra Way in #Martinez has left a plume of smoke over the city. Here's what it looked like a little while ago. Latest: https://t.co/DSzTbFl3QR pic.twitter.com/DOKAa962Vn— ABC7 News (@abc7newsbayarea) July 12, 2020
Structures were threatened because of the fire, but none were damaged, the department said.
No firefighters or residents were injured in the fire.
Smoke was seen from the Cummings Skyway.
The fire broke out near 4003 Alhambra Way in Martinez, which is about two miles from the Contra Costa County courthouse.
A protest is planned for Sunday afternoon not far from where the fire is burning.
Several thousand people are expected to peacefully protest in response to racist incidents in the city.