The Met Office has issued a Level 3 Heat Health Alert with a 90 per cent probability of heat health criteria being met between 9am today (Monday July 22) and 9am on Friday (July 26).
For Horsham, Crawley, Mid Sussex, Chichester and Midhurst there is a predicted heatwave - where temperatures will hit at least 27 degrees Celsius during three consecutive days.
The weather predicted for Tuesday looks set to top 30, while Wednesday could be a bit cooler at 28 degree Celsius before it goes back up to 32 degree Celsius on Thursday.
However, the forecast is changing, with already predicted temperatures increased from an hour ago.
For coastal towns and villages the temperature will fluctuate a little more, with Worthing seeing tomorrow (Tuesday) and Thursday around 29 and 30 degrees Celsius, with Wednesday a little cooler at 25 degrees Celsius.
Bognor Regis with see top temperatures fluctuate between 26 and 29 degrees Celsius.
Tomorrow (Tuesday) the area could experience 99 per cent humidity in the early hours, making for an uncomfortable night's sleep.
The Met Office has also said there will be a high UV count on the three days, with residents urged to make sure they wear sunscreen.
During a heatwave, residents are advised to stay out of the sun; cover up with suitable clothing and sunglasses; take extra care with children; keep your home as cool as possible – shading windows and shutting them during the day may help - and open windows when it is cooler at night.
You should also keep drinking fluids and if there's anybody you know, for example an older person living on their own, who might be at special risk, make sure they know what to do.