Harrow residents living near Wealdstone Brooks, Yeading Brooks and River Pinn have been warned flooding is possible from 6:00am tomorrow morning (18 June).
Heavy rain and thunderstorms are predicted in the Harrow area and people have been urged to avoid walking or driving through the water caused by flooding.
Forecasters have said that buildings could be damaged and the conditions could lead to delays on public transport.
The warnings issued said: “We have issued a Flood Alert. Heavy rain and thunderstorms, bringing the potential for locally intense rainfall, are forecast to affect London from around 6am and throughout the day on Friday 18 June.
“While uncertainty remains around exact timings and which areas will experience the heaviest rain, if this affects the Hendon, Wembley, Harrow, Wealdstone, Edgware or Stanmore areas there is the possibility that rivers could respond quickly and overtop their banks.
“Flooding to low lying land, roads and riverside gardens is possible on Friday. Surface water flooding may also affect these areas. We recommend you monitor local water levels and weather conditions. Consider putting your flood plan into action. You should avoid walking, cycling or driving through flood water.
“We are monitoring the situation closely and checking rivers for blockages. We will update this message on Friday afternoon, 18 June, or earlier if the situation changes.”