The Upper Hunter suffered from reduced visibility when north-easterly wind drove dust from the dry west to the coast yesterday morning.

A Department of Environment warned people with heart or lung conditions to limit outdoor exercise, but the latest influx of dust fell well short of the September dust storm.

The department recorded readings of about 10,651 micrograms of dust a cubic metre in the September dust storm, but yesterday's readings peaked slightly above 300 in the early afternoon.

Weatherwatch meteorologist Anthony Cornelius said the storm had made little impact outside the Hunter Region.

"It just seems to be in the Hunter," he said.

"It may have moved through Sydney but it was probably dark when it did.

"The Hunter seems to be the only area that got it, it doesn't seem to be moving up the coast. It's nowhere near as big as recent ones."

The recent spate of dust storms have been stirred up by unusually strong wind moving through dry areas in western NSW and South Australia, Mr Cornelius said.

He said it was a combination of unusual conditions that had led to the recent spate of storms, but increased moisture or rain would probably stop them recurring.

"We've actually seen a lot of strong systems sweep through lately," he said.

"[Recent storms] are just because the systems have been particularly strong."

There were no foreseeable dust storms, Mr Cornelius said.