Sussex Police urged people to look out for a missing 12-year-old girl this morning (Saturday 22 August).
Grace Clarke left her home in the Hollingdean area last night and failed to return home.
Concerns have been heightened by Storm Ellen, with the Met Office having issued a warning about the weather conditions.
Grace was described as white, about 5ft tall and with long dark hair.
She was last seen wearing a black hooded top, black leggings and Nike sliders.
Sergeant Simon Marchant, from Brighton, said: “We, and her family, are enormously worried about Grace and would ask her, if she is reading this, to make contact with either us, her family or a responsible adult.
“There is a possibility she may be taking shelter from the wind and the rain either in wooded areas in the Varndean or Hollingbury areas, or potentially in outhouses or sheds in people’s gardens.
“We are urging everyone to check their premises for signs of Grace and to keep an eye out for her.
“If you see Grace please dial 999 immediately.”