These public swimming pools are normally only open during the summer months. 

Veterans Home of California
100 California Dr, Yountville
(707) 944-4541

Calistoga Community Pool
1745 Washington St.
Calistoga, CA 94515
(707) 942-2846 or www.ci.calistoga.ca.us

Napa High School
2475 Jefferson Street, Napa
Season: June 25-August 16
Tuesday-Friday, 2:00-5:00PM
Saturday, 1:00-4:00 PM
Closed July 4!
Rates: 18 & Younger ($2), 19+ ($3.50), Seniors ($2), Spectators: Street Clothes ($1) 

St. Helena High School
(707) 967-2740
1401 Grayson Avenue
St. Helena, CA 94574
 
St. Helena Community Pool
St Helena, CA 94574
(707) 963-7946

Bothe Napa Valley State Park
3801 North Saint Helena Highway (Highway 29)
Calistoga CA 94515
(707) 942-4575

If you are looking for protected swimming areas in lakes or coves:

Lake Berryessa Visitors Center
5520 Berryessa-Knoxville Rd
Napa, CA 94558
707-966-2111
or 
Lake Berryessa Recreation Guide
www.berryessatrails.org
707-966-5211