An amber cold-health alert has been issued across Kent following a drop in temperatures.
This means there is potential for the whole population to be at risk, an increase in demand for health services, and travel delays, the Met Office says.
While a yellow weather warning for the South East has not been issued, the weather service also said there would be a hard frost and a risk of icy roads overnight on Monday.
It is expected that temperatures will start to climb gradually throughout the rest of the week.