Australia Weather News

Widespread rainfall across New South Wales over the weekend created ideal conditions for rainbows and lightning bolts to occur at the same time.

Some parts of the state had more than 50 millimetres of rain on Saturday, but it was the 11mm in Wagga Wagga that caused the double rainbow to appear, alongside lightning shooting across the sky.

Australian National University climatologist Janette Lindesay says while seeing a double rainbow is not rare, it is unusual to see one accompanied by lightning.

"To have that instantaneous current of a flash of lightning happening at the same time … that's the part that really grabbed me," Professor Lindesay says.

"Both are short-lived phenomena.

"To see them together like that, you have to be really fortunate."

Professor Lindesay says rainbows are formed when sunlight reflects off suspended water droplets in the atmosphere.

She says seeing a rainbow depends on "the angle between where the water droplets are, the sun and its elevation in the sky and its position in relation to the observer".

"All of that has to line up just right to be able to see the rainbows."

Lightning across the sky

Professor Lindesay says the lightning that occurred over the weekend, which streaked across the sky instead of towards the ground, is the most common form.

"Lightning is a discharge of electrical energy between two points which have an opposite charge, either positive or negative," she said.

"Twenty-five per cent of lightning overall is between a cloud and the ground.

"The rest of it is between clouds or within clouds."

The Bureau of Meteorology has forecasted more severe thunderstorms for NSW for Tuesday.