Shannon to San Francisco (SNN–SFO) — Airlines, Schedules & Connections

Irish passport holders enter the United States visa-free under the Visa Waiver Program (VWP) for stays up to 90 days. An approved ESTA (Electronic System for Travel Authorization) is required before boarding. The ESTA costs $21, is valid for 2 years or until the passport expires (whichever comes first), and covers multiple entries. Apply at esta.cbp.dhs.gov at least 72 hours before departure, though most approvals come within minutes.

Passport must be an ePassport (biometric chip, all current Irish passports qualify). No supporting documents are formally required for ESTA approval, but CBP officers at the port of entry may ask for proof of onward travel, accommodation details, and sufficient funds. The 90-day VWP stay cannot be extended and does not allow a change of immigration status. If you need more than 90 days, apply for a B-1/B-2 visa at the US Embassy in Dublin (MRV fee $185, interview wait times vary from 1 to 6 weeks).

Direct flights from Dublin to the US serve New York (JFK/EWR), Boston, Chicago, Washington Dulles, Los Angeles, San Francisco, and several others, running 7 to 10 hours. Shannon also has direct US routes. US Customs and Border Protection preclearance operates at Dublin and Shannon, meaning you clear US immigration before boarding and arrive as a domestic passenger. The US dollar is the only currency. No vaccination requirements for Irish arrivals.

BART from SFO station (free AirTrain from any terminal to the station) to downtown San Francisco takes 30–40 minutes ($10.45 to Embarcadero). Traffic on 101 can make taxis and ride-hails much slower during peak hours; BART skips all of that. BART also reaches Oakland, Berkeley, and Millbrae for Caltrain connections.Ride-hails from SFO use a dedicated garage pickup area; follow signs. Taxis are metered; downtown SF costs $40–60. Caltrain to the Peninsula (Mountain View, Palo Alto, San Jose) requires taking BART to Millbrae station for the transfer. Rental cars are at a consolidated facility accessible by AirTrain.

Coastal fog dominates the climate pattern. The thick marine layer ("Karl the Fog") rolls into SFO from the Pacific regularly in summer (June–September), causing significant low-visibility delays even on days that appear sunny inland. Morning fog burns off by afternoon most days, but persistent IFR conditions can last all day. This is the primary flight disruption risk at SFO.

Temperatures are mild year-round (10–20°C) with little seasonal variation. Winters bring rain (December–March) and occasional atmospheric river events that cause brief but intense flooding on the 101. Summers are cool. Pack a light jacket year-round. Wind off the bay affects small aircraft approach paths.