Fire season 'doesn't look good': BOM

Australians should brace themselves for a severe bushfire season as one of the worst El Nino events the world has endured reaches record strength.

The Bureau of Meteorology is warning the outlook for fires over the coming summer "doesn't look good" and expects the El Nino to become the strongest event of its kind by Christmas.

The El Nino weather event - which brings dry conditions - is likely to result in 2015 being the hottest ever recorded year for the globe, BOM officials told a Senate estimates hearing in Canberra.

Water resources were also likely to fall with extra pressure on the Murray-Darling Basin predicted.

Storages in northern areas of the basin already were down to 20-25 per cent, while those in southern areas were sitting around 45-50 per cent.

There was no "immediate crisis" for capital cities but the bureau warned levels would drop over the summer.