U.K. weather forecaster the Met Office says there will be heavy thunder showers across central and east London on Sunday afternoon, with hailstones also a possibility.
The forecaster predicts that the thunder and showers will clear later Sunday, and that Monday will be mostly dry.
More rainclouds, however, are forecast for Tuesday through Thursday. Temperatures, too, will drop this week, hovering at or below 20 degrees Celsius.
London has enjoyed bright and warm weather of up to 30C in the week leading up to the Olympics, after enduring weeks of rain.