Australia's main telecoms operators have switched on temporary disaster roaming (TDR).

The service will enable Australians to switch over to a different mobile provider if their own goes down during a weather emergency.

Following years of testing, the service will now be available in parts of the country when there's severe weather disruption.

If Telstra is the only network operating in a particular area, then Optus and TPG customers will be able to automatically connect to Telstra's network. Although plans will vary across different carriers, there's no added costs to use TDR.

The country's main operators are keen to point out that TDR is totally separate to the country's Triple Zero (000) service, which connects calls to Australia's emergency services.

TDR will only be switched on in specific circumstances, including when it can be done safely, and only where another participating network is still running and can carry the extra demand while still maintaining access to Triple Zero services.

Activations of the service will typically run for 24 hours at a time, noted Telstra.

"If a prolonged power outage takes down every network in an area, TDR can't help, which is one reason it sits alongside, rather than replaces, everything else we do to support network resilience," said Telstra.

The concept of TDR isn't unique to Australia, as similar services are available in other countries, such as Japan, where the country launched "JAPAN Roaming" earlier this year.

In Telstra's announcement of TDR, the company did warn that the service might not be available in metropolitan areas, as it's intended for use in regional and rural areas affected by eligible disasters.

On other occasions, TDR may not be in use when a power outage has occurred and there is no safe access to a generator. Older handsets will also be limited, as TDR requires VoLTE roaming, while the service itself is only for compatible smartphones and not for non-smartphone connected devices.