A northern New South Wales family has uncovered a meteorological treasure in the form of decades of meticulous weather records from more than a century ago.

Farmers are good record keepers of the day-to-day weather on the land, but Algernon Belfield went above and beyond his duty.

For 40 years from the late 1800s, he watched rainfall as well as humidity, cloud movement and wind speeds.

His records were so good that they are now being shared by scientists to help improve the way weather is forecast in Australia.

The rare and unique discovery of his observations started with an annual spring clean at the home of Elspeth and Richard Belfield on the outskirts of Armidale.

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"I said to him 'what on Earth are you going to do with these weather records?'," Ms Belfield told AM.

"I had a look at them and they were so complex and we had various people look at them and they all said 'we think these records are incredible'."

With that advice, she sought a second opinion.

That confirmed the little books were in fact some of the most accurate historical weather records in Australia.

"They've since found their place in the national archives, they're in the White House, they're in the UK, they're being studied around the world by various scientific bodies," Mr Belfield said.

The home of Algernon Belfield on the outskirts of Armidale ( Source: Richard and Elspeth Belfield )

The reason the books are so rare is the level of meteorological detail that was observed.

Every day, at the same time from 1878 to 1922, Algernon Belfield set out on foot to the same spot on his property to update his books.

"He would go to his weather station and get all his weather details," Richard Belfield said.

"My father said you would never go there at 8.50 because grandfather was on his mission and you just did not disturb him.

"He did 10 readings - cloud, moisture, all sorts of things every day. There's nothing like them in this period that's come to light so far."

That is a point not lost on Bill Oates from the University of New England.

"Suddenly amidst all these records you find this one particular run of really detailed methodical weather record keeping that sits on this continuous run for 40 years," he said.

"We haven't seen anything like this before. A lot of people record rainfalls, a lot of people are recording for the government meteorologists, but this is just a one-off stand-out set."

As well as the detail that Algernon Belfield kept, the importance of his work is the time these records were taken.

The Bureau of Meteorology officially started standardised records in 1910, and they did not start in the New England district until 1961.

Martin Babakhan from the University of Newcastle does a weekly forecast for farmers and says the data are helping him and others better predict weather here in Australia.

"We are coming up with the tools to give ourselves the best forecasting weather patterns for farmers," he said.

"If you can't understand the past, how can you expect us [to understand the future?]."