Maximum temperatures will reach 16 degrees Celsius, but likely to hover around 14 with a light breeze.
Into the evening, clear skies will turn the night chilly but persistent wind, particularly in the east, is expected to prevent a frost.
A minimum temperature of 3 degrees Celsius is forecast.
A mostly dry week is expected across East and West Sussex, with a chilly morning tomorrow growing into a sunny, but not particularly warm, day.
Tuesday will bring early cloud and rain which is forecast to give way to bright, breezy spells which will continue into Wednesday and Thursday.