Thunderbird was hit by about 500mm of rain by the extreme weather system, with the process plant, access road and accommodation village left in good condition.

The storm did impact some earthwork areas that were under construction before the skies opened.

While construction was not adversely affected by the storm, KMS kept busy by helping Main Roads and the shire.

Main Roads is also looking at using waste rock from Thunderbird to build temporary bypass roads.

Shire president Geoff Haerewa said KMS responded quickly to a request for the short-term use of earth moving equipment, which was much appreciated.

At Thunderbird, construction is on track and more than 75% complete.

Progressive installation of pipework and hoppers at the wet concentrate plant is underway and installation of steel structures at the concentrate upgrade plant has started.

Completion of construction activities and the start of commissioning activities remained on target for late 2023.

Sheffield Resources executive chairman Bruce Griffin said construction was advancing at a rapid pace.

"Our forecast pre-production activities now include anticipated changes to operational mobilisation and scheduling to reduce start up risk, resulting in an anticipated cost increase," he said.

"It is pleasing to note that KMS has continued to manage the capital expenditures in line with final investment decision estimates despite the inflationary environment."

Griffin said KMS was well positioned to complete the project comfortably within the available funding of $484 million.