The significant boost contributes to the longer-term trend, which has seen property prices in the area achieve 17.4% annual growth.
The average Northumberland house price in June was £181,776, Land Registry figures show – a 6.3% increase on May.
Over the month, the picture was similar to that across the North East, where prices increased 5.9%, and Northumberland outperformed the 4.5% rise for the UK as a whole.
Over the last year, the average sale price of property in Northumberland rose by £27,000 – putting the area second among the North East’s 13 local authorities for annual growth.
The best annual growth in the region was in Redcar and Cleveland, where property prices increased on average by 19.7%, to £139,000. At the other end of the scale, properties in Stockton gained 7.5% in value, giving an average price of £142,000.
Owners of terraced houses saw the biggest improvement in property prices in Northumberland in June – they increased 6.4%, to £142,538 on average. Over the last year, prices rose by 17.5%.
Detached houses are up 6.3% monthly; up 19% annually; to an average of £308,452.
Semi-detached properties are up 6.1% monthly; up 16.4% annually; to an average of £171,110.
While flats are up 6% monthly; up 13.4% annually; to an average of £95,265.
First-time buyers in Northumberland spent an average of £148,000 on their property – £21,000 more than a year ago, and £28,000 more than in June 2016.
By comparison, former owner-occupiers paid £209,000 on average in June – 41.6% more than first-time buyers.