After a warm and settled weekend Whanganui is in for a cool change as a cold front moves up from the south.
"For want of a better word things are going to get messy," MetService meteorologist Lewis Ferris said.
"Not only will Whanganui get rain, but there are strong southerlies expected on Tuesday as well.
"There is a high of 13C forecast, but if people are outside it will feel a lot colder because of those southerly winds."
MetService has issued a snow warning for the Desert Rd on Tuesday from 4pm until 10pm.
Snow is expected to settle on the road late Tuesday afternoon and evening with 1-2cm accumulation about the summit of the road, with lesser amounts down to 900m.
A high of 13C is also forecast for Wednesday when showers are expected to clear early, and the day will then be mostly fine with increasing high cloud and southerlies dying out.
The overnight low is expected to be 5C.
The rain is forecast to return early on Thursday morning and is likely to ease to showers later in the day with a northerly change.
There is a high of 16C forecast with an overnight low of 8C.
Friday will bring more showers expected to clear during the day with a high of 15C, an overnight low of 9C and a westerly change.
Westerlies are likely to be strong on Saturday, although showers are expected to clear during the day. A high of 16C is forecast with an overnight low of 9C.
Sunday will bring more showers and strong westerlies with a high of 15C and an overnight low of 8C.
Ferris said the average temperatures for early August are 14C highs and overnight lows of 7C.