'sweltering sun' is correct and usable in written English.
You can use it to describe a sun that is extremely hot or oppressive. For example, "The city streets were unbearable in the sweltering sun."
On Wednesday, a small crowd gathered under a sweltering sun as firefighters recovered the bodies.
In Yenagoa in Bayelsa state on Friday, Judith Jacobs had been standing under the sweltering sun for more than five hours.
The Warden is behind the unusual punishment metered out to the boys at Camp Green Lake, that they must dig holes in the sweltering sun every day.
A crowd of thousands had queued for hours under the sweltering sun, lines snaking around the campus of Florida International University.
He is often among the dozen or so Giants who remain on the field after practice, under what is often a sweltering sun.
The Yankees scored all their runs in the ninth inning of a 9-7 loss to Toronto, in a game played under a sweltering sun.
"I'm a fast walker," she said as she headed out through a working-class neighborhood under a sweltering morning sun.
The Levys, wearing yellow ribbons, looked dazed and tired as they met with reporters in the sweltering summer sun, both before and after their session with the chief.
The horizon is fringed with the tall trees of the Ghanaian rainforest, but for Huang, this dilapidated shelter is his only shade from the sweltering tropical sun.
He strapped an air conditioner to a side window to little effect; the bus still heats up like an oven in the sweltering summer sun.
Behind the stage which has been used by Islamist leaders to rally pro-Morsi supporters for the past six weeks, 25 bodies were laid out wrapped in white shawls, unrefrigerated in the sweltering August sun.
