The official death toll rose on Monday to 1,419, and at least 6,000 were injured by the 7.2-magnitude quake – a tremor even more powerful than the 7.0-magnitude earthquake that killed more than 200,000 Haitians in 2010.
The devastating earthquake has so far destroyed 3,000 homes and rescue workers fear conditions could worsen as tropical depression Grace makes landfall.
By midday on Monday, heavy rain was already lashing the capital, Port-au-Prince, with fears it could trigger landslides and flash floods.
Reuters said projections from the US National Hurricane Center (NHC) indicated that Grace, which is expected to hit Haiti between Monday night and Tuesday morning (Tuesday afternoon BST) , could pass over areas directly affected by the earthquake and douse them with up to 38cm (15in) of rain.
“We need to get prepared. It’s going to bring a lot of flooding … and it’s going to hamper rescue efforts,” said Jean William Pape, an established Haitian doctor who is involved in the earthquake response.
Homes, churches and schools were among buildings crushed in the quake and some hospitals were left overwhelmed and in need of supplies.
Humanitarian organisations have said survivors need drinking water and shelter.
More than 30,000 families have reportedly been left homeless.
It comes as the Queen shared her sadness at the devastation caused by the earthquake in a message of condolence to the prime minister of the Caribbean nation.
The Queen’s message to Haiti’s premier Ariel Henry read: “I am deeply saddened by the tragic loss of life and destruction caused by the earthquake in Haiti.
“My thoughts and prayers are with those who have lost their lives, loved ones and homes, as well as the emergency services working in the recovery effort.”
The natural disaster follows the assassination of Haiti’s president last month. President Jovenal Moise was shot dead at his private residence in July.