A 9-month-old baby and his stepbrother have been orphaned in a horror crash at Cambridge.

Baby Eli remains in hospital after surviving the crash that claimed the lives of his mother Brenda and his father Chris. The couple died in the crash on Cambridge Rd about 5.40pm on Saturday after their vehicle and a truck collided.

Brenda's cousin, Pam Tomkins, has created a Givealittle page to raise funds for Baby Eli and his half brother Riley, 11, who was not in the vehicle.

"Eli, 9 months, remains in Waikato hospital after a motor vehicle accident in Cambridge on Saturday evening which killed his Mum and Dad - Brenda and Chris," Tomkins wrote.

"Riley, 11 years [Brenda's son from a previous relationship] fortunately wasn't in the vehicle however he too has lost his much loved Mum and step Dad.

"All funds raised will go directly to a trust for the boys for their future support. Eli and Riley will be cared for by family."

The page had raised more than $6700 this morning.

The couple were two of eight people to die in five separate crashes around the country over the weekend.

On Saturday morning a woman died in a two-vehicle crash in Tahuna, 18km north of Morrinsville, then that night a person died when their vehicle hit a power pole on State Highway 25 near Pipiroa, 15km southwest of Thames.

A horror crash in Northland early on Sunday killed three people from the same family - Maurice Kareko, 35, Rhiannon Walters, 11, and Alec Walters, 5. A child was also critically hurt. The crash happened at 2.15am when a car smashed into a tree near Whananaki.

Waikato police acting area commander Andrew Mortimore said the weekend's rain after such a long period of dry weather, creating a "summer ice" phenomenon, was a contributing factor in the crashes, although he couldn't elaborate on which ones.

"One thing we can say is that we believe that the weather has been a factor. Statistically, looking back at last week, we had a 20 per cent increase in crashes in the Waikato compared to previous weeks.

"So we've obviously had quite a long stretch of fine weather, a lot of heat which does some funny things to the road particularly the composition of the tar.

"When you add a bit of water from the rain late last week it can turn into quite adverse conditions for people to drive in.

"It would appear, if we look at that 20 per cent increase in crashes, drivers have not adjusted to the change in conditions and we have had accidents which has potentially been a contributing factor to some of these fatalities as well."

Mortimore said the circumstances surrounding the four crashes in the Waikato were still being investigated by the serious crash unit.

Along with always wearing a seatbelt, not drinking and driving or speeding, he also urged drivers to be wary of the changing environment and adjust their driving, including speed, to the conditions.