The one accessory you won't need for tonight's fireworks near the city will be an umbrella - and extra layers of clothing can also be left at home.

Nearly ideal weather conditions are forecast for this evening's pyrotechnics, although the western suburbs and parts of the Blue Mountains may have to endure a late-afternoon thunderstorm before the final hours of 2018 tick away.

Almost ideal conditions predicted for watching fireworks in Sydney tonight. Credit:Janie Barrett

"It's more likely to be the western half of the city'' that will lie in the path of any isolated storm or showers, Tom Hough, a meteorologist with Weatherzone, said. That would include near Penrith or Richmond by about 5-6 pm, and "a bit sooner" in areas near Katoomba.

Gabrielle Woodhouse, a duty forecaster for the Bureau of Meteorology, said revellers might hear "a rumble [of thunder] here and there" and even see some lightning, but any rain would likely to be minimal.