Patients were told to expect a longer wait than usual for an ambulance as workers went on strike on Wednesday.
The South Western Ambulance Service which covers Somerset issued the alert on Wednesday morning, the day after it declared a 'critical incident' due to demand.
A spokesperson said: "Our 999 services continue to be under pressure today. Patients may wait longer for an ambulance if your call wasn’t triaged as immediately life-threatening."
The warning comes as thousands of ambulance workers went on strike across the country in a dispute over pay, with a second strike by nurses scheduled for Thursday.
People in Somerset were advised to only dial 999 in a life-threatening emergency ahead of the national ambulance strike by three unions on Wednesday, December 21.
The industrial action by union members working for the South Western Ambulance Service will affect non life-threatening calls and involve paramedics, control room staff and support workers.
Picket lines were set up across the region on Wednesday, including in Bridgwater and Taunton, as members of the GMB and Unison unions walked out.
The GMB went on strike from 6am to midnight, and Unison from midday to midnight. GMB members are also due to strike again in the South West a week later, on Wednesday, December 28.
The unions say staff will leave picket lines in emergencies. The government says it has honoured the advice of an independent pay review body for NHS staff, and bigger rises are unaffordable.
The military and civil servants have been put on standby to provide cover during strikes over the Christmas period, but it is unclear whether that includes Somerset.