The region's air quality is set to "nosedive" this weekend if there are more fires, made worse by high-pressure systems, according to a local scientist.
Hawke's Bay Regional Council principal scientist air, Kathleen Kozyniak, who issued the warning, said the scenario was "hazardous" for the community's collective health.
"Highs bring inversion conditions where a layer of cold air sits underneath a layer of warm air that, combined with smoky fires, are terrible for our air quality," she said.
"Over the last three days, PM10 (Particulate Matter smaller than 10 microns) levels in Hastings have shot up sharply, and it could get worse if skies clear over the weekend.
Kozyniak added: "I can't emphasise enough that these fine particulates are hazardous to health."
A Hawke's Bay Regional Council spokeswoman said: "In recent days, we've just avoided exceeding the PM10 limit of 50 µg/m3 for the 24 hour average and we really don't want to see it go over that limit."
Regional councillor and orchardist Jerf van Beek said cold weather makes air quality worse and air should be safe for everyone to breathe all year round.
"Before people burn anything outdoors we want them to think about their neighbours and community – fires shouldn't be a nuisance to people around you," he said.
Outdoor burning isn't permitted between May and August if your property falls within the Napier or Hastings airsheds.
Maungaharuru-Tangitū Trust appointee to the Regional Planning Committee Tania Hopmans said she is disappointed that illegal burning has increased in the past couple of weeks.
"It not only puts the community's health at risk but can be harmful to whānau with respiratory problems," she said.
Only dry vegetation, untreated timber, paper and cardboard can be burnt during the burning season outside of the airsheds. It is prohibited to burn plastic, rubber, treated wood and others at any time.
There are exemptions for orchard or vineyard redevelopment, replacing production trees and disease control, although smoke, ash or odour can't cause a problem past property boundaries.
"We check people are sticking to the rules with our Pollution Response team. If people are found flouting the rules they can be fined up to $1000, or prosecuted for more serious offences," van Beek added.
Concerned Havelock North resident Warwick Thomson, who alerted HBRC to a large plume of smoke near Havelock on Thursday, said he is concerned about the health of the community.
"At this time of year plumes of smoke go up pretty much every day and add to the already smoggy mornings," he said.
"It is appalling, uncomfortable, it stinks and makes my eyes itch, and it certainly won't be healthy. It is not what 'clean green' Hawkes Bay is trying to portray."
Thomson added: "If the law allows for it, then change the law now."
Peter Snelling, who took the photo of the large-scale burn offs on Tuesday, said it was "another glorious day ruined by thick smoke across the Bay".
"I realise this is an annual chestnut, but when, oh when, is the Hawke's Bay Regional Council going to put a stop to the pollution of our environment caused by fire burn-offs," he said.
The HBRC spokeswoman said they have made a lot of effort to educate horticulturalists and the wider public through a series of campaigns over the last few years.
"We believe people are aware of the issue because of our education and wider efforts, unfortunately, people will continue to do what they think or can get away with until more stringent rules come into place," she said.
If people want to report outdoor burning, they can call the pollution hotline on 0800 108 838.