The Met Office has issued a level 3 heat-health alert for Kent.
It follows yesterday's level 2 warning and confirms the weather service's threshold temperatures will be reached at the end of the week.
With temperatures set to reach the low 30s this week, public health experts have warned of potential health risks for vulnerable people on Friday and Saturday.
A level 3 alert is triggered when the Met Office confirms the threshold for one of more regions has been reached for one day and the following night, and the forecast for the next day has more than a 90% chance of doing the same.
An average threshold temperature is 30C by day and 15C overnight for at least two consecutive days.
This stage – known as heatwave action – requires social and healthcare services to target specific actions at high-risk groups.
Friday could potentially be the hottest day of the year so far, with early predictions of 32C in some places across Kent. If that prediction is accurate, it would make Britain hotter than Portugal, Jamaica, Costa Rica, the Canary Islands and Cyprus.
The amber alert for London, East of England and the South East will remain in place until midnight on Saturday.
A level 2 alert remains in place for the East Midlands and South West.
Most heat-related deaths occur in the first two days of a heatwave, so health bosses say action should be taken to reduce the risk of harm to vulnerable residents ahead of the soaring temperatures.
KCC director for public health, Anjan Ghosh, said: “We’ve been looking forward to nice weather and it’s quite right that people want to go out and enjoy it but it’s worth remembering that sunny spells and high temperatures can pose serious health risks for some.
"It’s important to protect yourself from too much sun or heat, to carry water when travelling, and it’s equally vital that you look after young children or older people, who may feel the heat more acutely than others.”
Key advice has been issued to ensure the safety of those at risk:
People are being urged not to go to A&E or call 999 unless it is an emergency. However, experts say that should you or someone you know become unwell, use 111 as the first point of contact.
Dr Navin Kumta, clinical chair of NHS Kent and Medway CCG said: “By taking simple precautions, such as staying hydrated and finding shade during the hottest parts of the day, you can significantly reduce the risk of becoming ill and needing the services of the NHS.