The coldest ground frost in 40 years was felt at the Grovetown Park weather station last week, weather statistics show.

The July 26 frost measured -8.3 degrees Celsius, while the air temperature plummeted to -3.1C on the same date, the coldest temperature measured since 2004.

In the Awatere Valley on the same day the coldest ground frost was -9C and the coldest air frost was -4.7C.

But despite the cold, Blenheim saw lots of sunshine last month, with the number of sunshine hours for July totalling 176.1, compared to 164.7 in July 2010 151.2 in July 2009 and the long-term average of 158.

Plant and Food research scientist Rob Agnew said that despite there being lots of frosts during July, there were only three days during the month when the maximum daily temperature didn't make it above 10C.

"July lived up to reputation for Blenheim, with some cold mornings followed by bright, sunny days.

"In fact, 13 of the 18 days that recorded ground frosts in July recorded above average sunshine hours."

But despite a good sunny July, Blenheim still trails Nelson and Whakatane for the year's total sunshine hours. Nelson, which usually has a much sunnier January than Blenheim, is 32 hours ahead and Whakatane is 16.5 hours ahead.

The first seven months of the year are the warmest since 1999 with an average temperature of 13.7C.

The mean temperature for July was 7.8C. The long term average is 7.2.

Total rainfall in July was just 62 per cent of the long term average – down to 40.6mm from 57.6mm in 2010, 50.8 in 2009 and 152.6mm in 2008.

July recorded slightly higher average daily wind-run at 249.6km. Last July was very calm with 196.9km wind-run. The average for July, 1996-2010 is 231.2km.

- The Marlborough Express

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