MetService communications meteorologist Lisa Murray said tropical weather systems north of New Zealand had led to very muggy and humid conditions here.
"That's generally why we're having -- especially in northern areas -- this warm February.
"It's really the overnight temperatures that are contributing to that. We've had this really warm, humid air from these different systems in the tropics that have pushed this air down over [to us]."
Ms Murray said some places were seeing their long-term temperature average -- which includes both day and overnight temperatures -- on track to beat previous February records.
Places including Hamilton, Wellington and Dunedin were on track to beat their February long-term temperature records.
But she said with a few days left in the month, including the extra 29th day this year, things could change for other places as well.
"We can't talk about breaking records yet because we still have a few days to go."
High temps today:
• Auckland: 24.3C
• Napier: 29C
• Hastings: 31C
• Hamilton: 25.9C
• Tauranga: 25.1C
• Wellington: 23.9C
• Christchurch: 32.8C (hottest in the country)
• Whangarei: 26C
• Rotorua: 24C
• Masterton: 30C
• Dunedin: 24.C
• Blenheim, 31.1C. (second hottest)
• Coolest: Gore, 14.9C