London has been hit with a yellow health alert by the UK Health Security Agency (UKHSA) as the capital faces a possible fifth heatwave. However, things will warm up on Sunday before peaking on Monday, when temperatures could reach 32C according to the Met Office. Advertisement AdvertisementAdvertisement AdvertisementThe UKHSA's health alert is in place from 9am on Sunday until 9am on Thursday, August 5. In London a heatwave is reached when three or more consecutive days see temperatures reach 28C or higher. "[Sunday] will be turning relatively hot once again in the southeast, where temperatures could get quite close to 30 degrees Celsius in the London area.