Sunday reprieve from heatwave

The mercury is predicted to hit 42 today (Friday).

Followed by a cool 39 tomorrow.

However the good news it will drop to 34 by Sunday.

But the bad news? It will steadily climb back to 39 by Thursday.

But the good news.

It could all be a lot worse.

Thargomindah could set a new record for the state's highest January minimum temperature.

The current record of 34.5 degrees was set in Birdsville in 2003.

It's possible the mercury won't dip below that in Thargomindah on Friday, with a minimum of 33 degrees forecast.

"The potential is definitely there," BOM meteorologist Andrew Bufalino said.

Acting Health Minister Stirling Hinchliffe has urged people to regularly check the colour of their urine to ensure they stay hydrated.

"If you are feeling that your urine is dark, you should make sure that you increase your fluid intake - that's the best way of making sure you keep yourself safe," he said on Thursday.

Temperatures are expected to return closer to average on Sunday when a trough should bring rain and thunderstorm activity.