The Big Latch On will start at 10.30am. Last year more than 1500 mums and their babies took part in New Zealand and Ms McKay hopes to surpass that number this year.
Chris Gower-Rudman of the La Leche League is hosting the Big Latch On at the Rotorua Public Library. "It's a good way to normalise breastfeeding. It's good for mums to be able to meet people who are doing the same thing as they are."
Mrs Gower-Rudman took part in the first Big Latch On in 2005.
The Rotorua Parents Centre is also organising a venue for the first time this year.
President Claire Armstrong said it seemed like a natural thing to do.
"It's about making breastfeeding normal. If people choose to breastfeed we want to create a supportive environment for them."
She said she had no idea how many people would turn up.
"If we had 10 people show up, I'd be happy."
Ms McKay said a key part of breastfeeding week was creating a supportive environment.
She said around 90 per cent of mums intended to breastfeed and initiation rates at hospitals were high, but once mums returned home they needed more help.
"Community and peer support are really important for mums continuing to breastfeed, so the Big Latch On creates that," she said.
Ms McKay said mums who wanted to take part could call the organiser to let them know, but registering was not necessary.
"It's not a hard and fast rule. Anyone who turns up will be welcome."
Rotorua mums can take part in the Big Latch On at the Linton Park Community Centre or the Rotorua Public Library.
World Breastfeeding Week finishes August 7.