Heavy rain yesterday afternoon saw part of the A23 north of Brighton affected by flooding.
Emergency services were called to the scene after one of the lanes was completely blocked by water on Friday (August 10).
The fire service said a high volume of calls about flooding were coming in.
A spokesman said: "The weather is atrocious and with so much rain in such a short period of time we’re experiencing flooding across the county.
"We’ve had a high volume of calls and will respond in priority order as quickly as we can.
"Anyone planning on making a journey today, please drive carefully and if possible avoid driving through flood water as there may be unseen dangers below the surface that could cause an accident."
The Met Office forecast for today (Saturday August 11) warns that heavy rain could return this afternoon, while Sunday could also see more downpours.