At about 11pm Tuesday, they checked the fires and decided it was safe to go to bed.
But by midnight, a sudden wind shift had pushed the blaze down towards the Governors Bay village.
At 2am yesterday, 32-year-old Jessica went into labour.
Luke walked to the nearby local fire station where he could see "tall flames on the hillside".
"They were about to start evacuations a little bit further up the hill and said that if we wanted to get out then now was a pretty good time to do it," the 28-year-old IT consultant said.
That night more than 100 Governors Bay locals were evacuated, with many sheltering at the primary school which had been turned into a makeshift welfare centre.
Luke ran home and within minutes he was bundling his wife, who was having contractions, into the car, along with three cats and a dog in the backseat.
As they drove away, the threat became even clearer.
"It was crazy. As we drove around the hill, you could see this huge, glowing orange in the night sky right behind our house. It was pretty upsetting," Luke said.
They drove to a friend's house in Christchurch to drop the pets off.
A midwife met them there who, after a quick check, told them to get to Christchurch Women's Hospital immediately.
At 6.47am yesterday, weighing 7lb 1oz baby Thea was born.
"Mum and baby are doing great and the labour went perfectly. It was very quick, especially for a first birth," Luke said.
"I'm sure it was sped up by the situation, of getting out."
Last night, as the fires raged on and hundreds more Cantabrians were evacuated from hillside areas, the Thomas family was reflecting on the day's events.
"We're stoked. There's a lot going on, and a lot of the people in Governors Bay are part of the volunteer fire brigade as well, and those guys are doing amazing work," Luke said.
"We will always remember the day Thea was born."