The mystery surrounding unusual lights over Whangarei may have a logical explanation, says the Northland Astronomical Society.
Three people have come to the Northern Advocate since Monday with reports of strange lights seen in the sky over the last few days.
A society spokeswoman said Jupiter was rising in the northeast and reflected a lot of light, shining more brightly than stars. She said when Jupiter was rising the society received many calls relating to unusual lights in the sky.
Weather analyst Phillip Duncan said the heat in Northland in the last few days rose off Earth and created a haze, similar to that on a hot road, distorting the light.
"It is not unusual for this haze to make stars or planets flicker and twinkle as if they are moving or disappearing," he said.
As for the three blue lights builder Graham Jones saw, there wasn't a simple explanation for those.
"Helicopters are the most common explanation for lights seen on the horizon that can be mistaken for UFOs," Mr Duncan said.
He explained that on a clear day, helicopters could be seen from very far, so were virtually indistinguishable from a small light. They flew low and would be silent if far enough away.
"I, myself, have seen three lights fly across the Northland night sky while camping," he said.
"It turned out that on clear nights you can see planes taking off from Auckland, and when they are taking off they often leave three navigation lights on."
Suzanne Henson, director for Ufocus NZ, an organisation that collects data on New Zealand UFO reports, had not received any in Northland in the last three days.
Whangarei Airport confirmed it was not the source of the lights, with no unusual activity reported or on file.