Temperatures are climbing in Perth as a broadening low pressure trough gets set to generate widespread thunderstorms across WA this weekend.

Hot air from northern and central Australia will filter down to the nation's southwest as a low pressure trough deepens over WA on Friday.

Perth is forecast to reach 32 degrees during the afternoon, which is five above average for this time of year. This would be the city's first day over 30 degrees since May, making this its latest first 30 degree day of the season since 2005.

But while it will be warm and sunny in Perth for the next few days, the deepening trough will trigger widespread showers and thunderstorms over the state's inland districts and northern tropics.

The heaviest rain and thunderstorms will target the state's western interior on Saturday and then shift further south and east on Sunday. Some inland areas of the state could receive 30-50mm of rain during the weekend, most likely about the eastern Gascoyne, northern Goldfields and South Interior.

Some of this weekend's thunderstorms are likely to become severe, so keep up to date with the latest warnings at: http://www.weatherzone.com.au/warnings.jsp