The UK's spell of warm weather is set to continue this week, but how hot do you think is too hot?
Temperatures are expected to reach 28C in cities such as London and Manchester on Tuesday, as much of the country will stay dry and sunny.
The Met Office is forecasting that the sun will shine across the UK for the rest of the week, with areas such as Scotland and the north of England already officially experiencing a heatwave.
It said almost all of the UK will experience a heatwave this week, after Saturday was the hottest day of the year so far, with temperatures reaching 32C.
Thunder, lightning and heavy rainfall hit large parts of the UK on Monday, and Met Office yellow thunderstorm warnings remain in place until 9pm on Tuesday in Northern Ireland and Scotland.
But most parts of the country are expected to see dry conditions for the rest of the week.
In your opinion, how hot is too hot?
Let us know what temperature is too much to bear by taking our interactive poll below:
Met Office forecaster Simon Partridge said drier weather was expected going into the latter parts of the week.
“We’ve got high pressure starting to rebuild over the course of the day and when you get high pressure that’s what gives us lots of dry, settled weather, like what we’ve had over the last couple of weeks," he said.
How hot will this summer be?
Meteorologists in the US announced earlier this month the return of the El Nino weather cycle, which could lead to record global temperatures.
El Nino conditions are present after three years of the cooler La Nina pattern, which often lowers global temperatures slightly.
El Nino describes the warming of the sea surface temperature that typically occurs in the central and eastern Pacific Ocean near the equator every few years.
The year 2016 began with an El Nino phenomenon and this contributed to it being the hottest year on record.
Early forecasts suggest that this year's El Nino could see global warming reach the crucial barrier of a 1.5C rise since pre-industrial times.
If this happens, it could lead to more heatwaves, longer hot seasons and shorter cold seasons, according to the Intergovernmental Panel on Climate Change.
Professor Adam Scaife, head of long-range prediction at the Met Office, said: “The El Nino pattern of natural climate variability, which is developing quickly in the tropical Pacific, will have widespread consequences.
“Among these is the strong potential for a new record global temperature, most likely exceeding 2016, the current record year."
- Read more: El Nino returns and could bring record hot temperatures (Sky News, 2 mins)
What's the threshold for a heatwave in the UK?
According to the Met Office, a heatwave is "an extended period of hot weather relative to the expected conditions of the area at that time of year, which may be accompanied by high humidity".
The Met Office said the UK heatwave threshold is when when a location records a "period of at least three consecutive days" with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.
This threshold varies by UK county, from 25C in Northern Ireland, Scotland, Wales and the North and South West of England, to 27C and 28C in the South East of England.
Is there a link between heatwaves and climate change?
The Met Office says that climate change is making heatwaves more likely.
In a study carried out in 2018, the Met Office said human-induced climate change made record-breaking high temperatures 30 times more likely than they would be naturally.
Met Office scientist Dr Nikolaos Christidis said in December 2018: “Our models show that there is now about a 12% chance of summer average temperatures being as high as the UK experienced in summer 2018. This compares with a less than half per cent chance we’d expect in a natural climate.”
Heatwaves are 30 times more likely to occur now than before the industrial revolution, the Met Office said, because of the higher concentration of carbon dioxide in the atmosphere.
The Earth’s surface temperature has risen by 1°C since the pre-industrial period – between 1850 and 1900 – and UK temperatures have risen by a similar amount, the Met Office said.
The highest ever UK temperature of 40.3C was recorded on 19 July last year at Coningsby in Lincolnshire.
Watch: Week of sunshine forecast across the UK after thunderstorms