High temperatures and sloppy food preparation are being blamed for a surge in stomach bugs.
Scientists say January was the country's hottest month in 150 years, which can provide a breeding ground for bacteria.
Cooking food on the barbeque is as quintessentially summer as a day at the beach - but the combination could be making you sick.
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Dr Ngaire Kerse, Head of School for Population Health at Auckland University, said she's not surprised more people have been reporting tummy bugs than usual this summer.
"I've seen a few people with gastroenteritis in January," she told Newshub.
"I've been camping and it's been so hot. I totally agree with the reporting of the increase in gastroenteritis."
New data shows stomach bug cases have surged this summer.
In Auckland the number of cases in January is up by almost 50 percent compared with the same time last year. Northland is up a whopping 74 percent, while Hawke's Bay and Wellington have also seen big increases.
The figures include nine diseases which can cause gastro problems, such as campylobacter, salmonella and giardia, as well as gastroenteritis.
The bugs thrive in meat and chicken that has been lying in the sun, nutritionist Nikki Hart told Newshub.
"Bacteria like warm, wet, nutrient-rich conditions, that's how they love to grow. So it's important that you be careful of the environment that your food is in."
Taking care should include making sure the seal on your fridge is secure and using separate chopping boards for meat and vegetables.
The same rules still apply at the beach.
"I see people packing chilly bins, big ones, and their whole fridge has been dumped into that chilly bin. Either they don't have enough silica pads in it, or they haven't separated raw from cooked foods, and I think that can be really problematic at this time of year."
Gastro isn't always caused by food. It can also be spread through animals, infected people and untreated water.
Those feeling queasy should drink plenty of fluids. A simple rehydration method is to add half a teaspoon of sugar and a pinch of salt to a large glass of water.
Fruit juice should be diluted by half, and those in the recovery phase should avoid milk.
The most important rule is to stay away from others until symptoms pass.