David Cameron has praised the "preparedness" of the Mexican authorities for Hurricane Patricia after one of the most powerful storms on record made landfall.
Heavy damage appears to have been avoided, while there have been no reports of fatalities so far.
Hurricane Patricia is now "rapidly weakening" over Mexico, the US National Hurricane Centre said.
Hurricane Patricia has weakened to a Category Two storm but authorities have warned deadly floods and mudslides are now likely.
"The first reports confirm that the damage has been less than those expected from a hurricane of this magnitude," Mexican President Enrique Pena Nieto said.
But he added: "We cannot yet let our guard down".
Hurricane Patricia has weakened to a category 4 storm over Mexico, according to the National Hurricane Center in the US.
They say it is expected to rapidly weaken to a tropical storm by Saturday morning.
Hurricane Patricia has brought torrential rain, surging sea and cyclonic winds of up to 165 miles per hour as it hit the Pacific coast.
Forecasters have warned it will potentially cause “catastrophic” damage.
Television footage showed toppled trees and rain lashing down.
Hurricane Patricia, set to be the strongest on record, has hit land on Mexico's Pacific coast with winds estimated at 165 miles per hour.
Patricia made landfall at Playa Perula in the state of Jalisco, Mexico's meteorological service said. The US National Hurricane Center said Patricia was the strongest storm ever recorded in the Western Hemisphere.
Tens of thousands of residents in vulnerable areas have been evacuated, whilst millions more have been advised to prepare for the "worst-case scenario" to protect life and property.
Hurricane Patricia looks set to be the most powerful hurricane ever recorded, with winds expected to top 200 mph.Read the full story ›
As Mexico prepares for landfall of perhaps the strongest tropical storm on record, one of the astronauts on board the International Space Station has tweeted an incredible photograph of Hurricane Patricia from space.