A survey of traffic volumes suggests the economy is growing, but the impact of the drought could cause some volatility in gross domestic product figures due out next week.
ANZ Bank's Truckometer, which uses traffic volumes as a proxy to map quarterly economic growth, shows traffic flows rose last month.
The Heavy Traffic Index, which measures flows of trucks on 11 roads, surged a seasonally adjusted 4.7 percent in May, with flows lifting on eight of those roads.
The Light Traffic Index, which gives a six month lead on GDP growth, rose 2.2% and ANZ said the trend in this index is rising.
Senior economist Sharon Zollner said the data bodes well for growth in the second half of the year.
She says the 4.7% increase built on a strong rise in April.
"That's a contemporaneous indicator for GDP, so that's good news for the end of Q1 and the first couple of months of Q2."