Eastern NSW is in for plenty of severe thunderstorms on Monday afternoon as warmth, humidity and instability all collide along the ranges.

Heat is being drawn ahead of a southerly change that is making its way up the coast. Temperatures are expected to peak in the mid-to-high 30’s for the northern half of the state, possible nudging 40°C in the northwest.

Image: Forecast temperatures on Monday. Areas in red are expected to reach at least 35°C

As a cool southerly change moves through, it will combine with the warm and humid air east of the divide, causing it to rise and turn into thunderstorms.

Image: Lifted Index (LI) on Monday. Locations in white and blue could see thunderstorms, with the darker blues indicating a higher chance of severe storms.

Upper cold air will be crossing along with the southerly change, allowing for thunderstorms to become severe with large hail, damaging wind gusts and heavy rainfall.

There is also the possibility of some supercell thunderstorms developing, most likely for the Hunter and Mid North Coast. These are the most dangerous type of thunderstorms and can produce giant hail (larger than cricket balls), destructive winds (exceeding 120km/h) and intense rainfall (flash-flooding).

Thunderstorms look to be generally confined to occur on and east of the ranges, north of about Nowra, possibly including Sydney, Wollongong and Newcastle.

Image: 24hr rainfall on Monday. The 'patchy' nature of the rainfall indicates showers and storms

With severe thunderstorms on the forecast, keep an eye on our warnings page for up-to-date information on storms in your area.