Heavy rainfall and dirty asphalt have created a deadly blend on NSW's roads, with ambulance crews observing a 35 per cent jump in the number of road accidents following the state's biggest deluge in months.

Emergency services are urging drivers to be more cautious after NSW Ambulance attended to more than fifty motor vehicle accidents on Friday, including two fatalities.

NSW Ambulance at the scene of a fatal crash on Friday. Credit:NSW Ambulance

Those deaths, a 65-year-old motorcyclist who crashed into a barrier near Blacktown and a 32-year-old driver in the Hunter region, bring the state's road toll to eight since the beginning of the year.