The Scottish Environment Protection Agency (Sepa) warned of an increased risk of water scarcity in its situation report published on Friday.
It comes after the temperature gauge peaked at a record 35.1C at Floors Castle, in the Scottish Borders, on Tuesday.
Jennifer Leonard, Sepa’s senior water and land manager, warned “water scarcity is a very real threat as a result of climate change”.
She said: “Dry ground conditions and low river levels means the Don catchment has been raised to moderate scarcity.
“With similar conditions across much of Scotland, the Ythan, the Dee, the Firth of Forth area, the Almond, Tyne and Firth of Tay group remain at moderate scarcity.”
In the west, the Leven catchment area in Dunbartonshire has been raised to an early warning, joining the rest of Galloway and Ayrshire.
Most of the east coast is now at alert or moderate scarcity levels due to an extended period of low river levels and dry weather.
SEPA continues to monitor the situation closely and co-ordinate steps to manage water resources in line with Scotland's National Water Scarcity Plan.
In early warning areas, the advice is for businesses to consider their coming water requirements and to check equipment for any leaks.
If the water scarcity risk level reaches significant, SEPA will then consider whether restrictions on abstractions will be required to protect the water environment.Ms Leonard said: “[Water scarcity] is also the result of long-term weather deficit and below average rainfall, and although some rain is forecast, it is unlikely there will be enough to improve conditions.
“We want to work with businesses to plan their water usage long term, so that we can preserve this vital resource. Not only will that protect Scotland’s rivers and lochs, but it will minimise business risks as well.
“In the meantime, we stand ready to offer advice and support to businesses affected by the current conditions.
“Whilst our first aim is always to help people do the right thing, we can hold to account those who deliberately fail to comply with their legal responsibilities when abstracting water from the environment.”