We recommend flying into SFO and renting a car at the airport. Uber/Lyft/Taxis are also available if preferred.
Renting a car to drive from San Francisco to Napa, as well as around Napa, would be best. Uber/Lyft are options as well.
San Francisco tends to be foggy during summer with a cool breeze, so remember to bring layers and even a puffer coat! Napa, despite being just an hour's drive away, has a very different climate with hot summer days and cool evenings. Pack accordingly!
Despite what travel websites might say, we do NOT recommend going to downtown San Francisco, Union Square, Fisherman's Wharf, etc! We've put the best places to go on our "Things To Do" tab. We love staying in Northern San Francisco the most (Marina, Presidio, Pacific Heights, Cow Hollow), and avoid staying downtown.
Napa is approximate 1-1.5 hours north of San Francisco.