The UK enjoyed higher temperatures than the Costa del Sol on Saturday, with Sunday expected to be still hotter.
Forecasters predicted the UK's hottest weekend of the year
A high of 30C (86F) was recorded during the afternoon in London, compared with 29C (84.2F) in Malaga, Spain.
The temperature reached 28C (82.4F) in Birmingham, 27C (80.6F) in parts of the South East and Yorkshire, and 24C (75.2F) in Aberdeenshire.
A year high of 32C (89.6F) is forecast for Sunday. Ladbrokes has cut odds on the UK breaking 100F (37.8C) this year.
The bookmakers cut the odds from 6 to 1 to 5 to 1. It had been offering 16 to 1 in January.
The UK's record temperature of 38.1C (100.6F) was recorded in Gravesend, Kent, in 2003. This year's high was 31.9C (89.4F) in London on 27 May.
Sunseekers were flooding on to the beach in Brighton, East Sussex, by 0930 BST, according to seafront council workers.
"I don't think I've ever seen people get onto the beach as early as this," a spokesman said. "You literally cannot see the stones."
The Maritime and Coastguard Agency (MCA) had urged people at the seaside to take extra care to avoid accidents.
"Hot weather inevitably means more people visiting the beach, which in turn results in more incidents," said chief coastguard John Astbury.
The MCA said it was particularly concerned about the number of parents and young children who get into trouble swimming, and launched its Sea Smart campaign to promote sea and beach safety.
The Met Office had warned fair-skinned people of a very high sunburn risk during the weekend, while the RAC urged people to plan journeys to avoid long queues.
MCA'S SEA SMART CODE
Spot the dangers
Always go swimming with a friend
Find and read safety signs
In an emergency call for help, tell a lifeguard or dial 999 for the coastguard
A Met Office statement read: "With soaring temperatures, concerns rise for people's wellbeing.
"The sun is at its strongest at this time of year and sunburn is a real hazard."
During the heatwave of 2003, some 27,000 people across Europe died as a direct result.
In the UK there were 2,000 deaths caused by the heat - 85% of which were people aged 75 and over.
Health experts say it takes just two consecutive days of heatwave temperatures to have a significant effect on health.
After the 2003 heatwave, the government instituted a warning system which identified four levels of risk. Currently, this weekend is at level one, the lowest risk level, where general vigilance is urged.
Thundery showers are forecast for Sunday and Monday, followed by slightly cooler weather.