Despite the conditions looking okay from shore, around 200 to 300m out the group hit a strong westerly and realised they wouldn't be able to get themselves back. One person then fell from their kayak and were unable to get back in.
The four were wearing life jackets and carried a cellphone with them. Coastguard Rotorua were contacted by someone on shore who had seen the man fall into the water.
Mr Grouby said the weather conditions were "really rough", with the lake very choppy. He said there were 1.5 to 2m swells and it was 35 knot wind.
Once the Coastguard team located the group it was an "full on" rescue. One boat and three Coastguard volunteers were involved.
"People don't realise how bad the lake can get. It can change quickly."
"People have to be prepared. Check weather conditions, wear a life jacket and carry a cellphone."
This is the second weekend in a row Coastguard Rotorua have had to perform a rescue on Lake Rotorua.
A man was also rescued last weekend.
A St John Ambulance spokeswoman said three patients were taken to Rotorua Hospital Emergency Department at 10.50am.