21/06/2026 – Weather in Cornwall

Cornwall Heads for 31°C This Week as Humid Heat Builds

The good news is the sunshine has arrived for the week. The bad news is the nights that come with it.

Cornwall is in for a mostly dry and increasingly warm spell from now through Thursday, with temperatures climbing into the low thirties and overnight conditions that could make sleeping difficult.

What the forecast says

Today starts with any early cloud quickly breaking up, leaving a bright day with plenty of sunny spells. An isolated light shower is possible in the afternoon. It will feel very warm and increasingly humid, with a maximum temperature of 28°C.

Tonight, any showers ease away to leave a dry night with clear spells and light winds. It stays warm and muggy, especially further east, with a minimum of 12°C.

Monday is the hottest day in the forecast. A little showery rain is possible through the morning before it turns drier and brighter with sunny spells into the afternoon. It will feel hot and humid for everyone, with a maximum temperature of 31°C.

From Tuesday through to Thursday the picture stays settled. The forecast points to dry, sunny conditions throughout, feeling hot by day in the strong sunshine and increasingly warm and humid overnight.

The nights are the hard part

If the heat itself does not get you, the muggy nights might. The forecast specifically warns of difficult sleeping conditions tonight, with the warm and humid overnight temperatures building as the week goes on.

It is the humidity as much as the heat that makes the difference. A 12°C minimum sounds mild on paper, but combined with the muggy air it is enough to leave the bedroom feeling stuffy and restless.

And with the warm overnight conditions set to increase through Tuesday, Wednesday and Thursday, the broken sleep could stack up across the week.

Maximum temperature Monday: 31°C.