A spokesperson for the body said Britain’s only venomous snake are back after months underground.
The National Trust reminded people adders are ‘shy’ and ‘ask only to be left in peace.’
A spokesperson said: “After months underground, Britain’s only venomous snake is emerging to bask in the first warm days of spring and they really are a wonderful sight.
“Look for them on heathland, moorland and chalk downland, coiled quietly in the sunshine.
“Recognisable by their beautiful zigzag markings, they are shy creatures that ask only to be left in peace.”
The trust said to give the reptiles space and keep dogs close when around adders, but to also appreciate the declining species as a sign of the new season.
Photos of adders can be uploaded to the County Press Camera Club on Facebook.