Brief "explosions" of heavy rain showers across the upper North Island yesterday afternoon helped ease the worries of some drought-stricken farmers.

Across Northland, Auckland and parts of central Waikato afternoon cloud build-ups produced torrential downpours heavy enough to spill over gutters and saturate the ground, according to weatherwatch.co.nz.

Head weather analyst Philip Duncan said the thin band of showers also fell across western regions of the lower North Island and much of the West Coast, with very light drops also present in the east.

"We knew the rain wouldn't be widespread but it was great to see the afternoon cloud build-ups pushing into Auckland, Northland and Waikato," he said.

Despite the downpours across northern New Zealand, the first part of the nation to be declared a drought zone this year, many farms missed out.

"It's frustrating for those who missed out this time but week by week, region by region, these showers are now making inroads into the drought.

"The green is coming back, little by little, and right across the country.

Those who still only have brown will hopefully see some rain or showers in the coming 10 days as well."

According to the site, showers were expected to continue in Northland until Wednesday, with light showers likely in Auckland until Friday.

In the Bay of Plenty and Waikato showers were expected later in the week.

Mr Duncan said warm temperatures would enhance growing conditions for those receiving rain.

"Those lucky enough to receive rain will certainly see new and rapid grass growth in the coming week or two."

The rain also made driving hazardous. Police warned motorists travelling on SH1 between the Brynderwyns and Waipu to drive carefully as downpours made the road slippery.

Slippery conditions on the Rimutaka Hill Rd yesterday caused three car crashes.

Featherston police Senior Constable Nigel Nelson said the crashes had happened in quick succession about midday. No one was injured.

- APNZ