Forecasters warn that rain and snow on frozen surfaces can cause travel disruption and further icy conditions.
Met Office yellow weather warning for ice The law is in effect until 14:00 GMT in Wales.
According to the Welsh Ambulance Service, it was experiencing difficulties high call demandThis is especially true for people who have fallen.
A separate warning was issued to large parts of Wales that heavy rain is possible starting at 18:00. weather warning.
Due to high demand, the ambulance service stated that some patients were forced to wait up to an hour for an ambulance.
Sonia Thompson, assistant director, operations, stated that “extreme weather, combined with a high number of calls which are mostly reporting falling and breathing problems, has limited our ability to respond safely, and timely.”
“We’re sorry for anyone who waited longer to have their calls answered and then waited longer for an ambulance to arrive.”
The Met Office stated that up to 50mm (2ins.) of snow could be falling on Wales’ highest ground and up to 20mm (0.8in) on lower levels. However, this could lead to an increase in the ice risk.
It stated that strong winds were expected, mostly over higher ground, in addition to the risk of ice and snow.
People were also warned to expect heavy and persistent rain starting Sunday evening.
According to the Met Office there would be a difference of 35-50mm (1.3-2in), for many areas, and 70-90mm (3.2.7-3.5in), on high ground.
This warning applies to south-east Wales and Swansea and Carmarthenshire, as well as Powys, from 18:00 GMT Sunday through 06:00 GMT Tuesday.
This rain alert comes on the heels of one that was issued over the weekend due to icy conditions. “only drive if it’s necessary” Due to “extremely poor road conditions.”
Gwent Police reported road accidents, and North Wales Police reported road closures due ice.