The power was running again at Woolworths after 6pm but Horsham Plaza remains closed until Saturday

More than 200 customers are still without power in Horsham and Pimpinio, according to Powercor.

The Western Freeway Melbourne-bound was closed to motorists as a grassfire threatened properties near Myrniong.

The fire is under control but traffic is banked up Melbourne-bound to before Pentland Hills Road, and is now being diverted along the old Western Highway.

READ MORE: At least three buildings under threat by Pentland Hills blaze

Update 6.10pm: EMERGENCY crews are responding to multiple calls for assistance with building damage and trees down across Horsham.

There were more than a dozen reports of incidents across the Wimmera, with the highest concentration of issues in Horsham.

Power is still out and affecting more than 2000 customers in the region, with Powercor having updated the expected time of restoration to 7pm.

The highest temperature recorded in the Wimmera for Friday was 44.6 degrees at Warracknabeal airport at 2.42pm, while the top windspeed was 98km/h in Horsham at 4.21pm.

Update 5.30pm: POWER outages in Horsham have also affected multiple stores including Woolworths and Horsham Plaza which has been closed for patron safety.

The Horsham Woolworths store lost power completely after 4pm, with the generator running now at a minimum.

The store was still trading but customers are shopping in the dark and without air conditioning.

Staff have wrapped perishable items such as cold meat and fresh vegetables in a black plastic wrap, with the fridges still out.

The power was also out at Horsham Plaza which has been closed off to the public until Saturday morning to ensure customer and staff safety.

Horsham Priceline on Baille Street was also without power but has continued trading.

The power was still running at Coles in Horsham.

More than 2000 structures are without power across the Wimmera, according to PowerCor.

Update 5.05pm:

FIREBRACE Street, Horsham has now reopened.

Update 5pm:

AUTHORITIES have blocked the corner of Horsham's Firebrace and McLachlan streets after part of the roof of Horsham's State Emergency Services building blew off.

Horsham Fire Brigade captain John St Clair said the roof was connected to a powerline.

"We're securing the tin from the roof; I know the SES is out at a number of other jobs including roofs that have been damaged and trees across roads," he said.

"This job should take about 15 minutes, then we'll go help the SES with their jobs."

There are reports that the power is out at Horsham's Woolworths store.

Update 4.50pm:

THE Bureau of Meteorology has issued a severe thunderstorm warning for parts of the west and south-west of the state over the next several hours.

Motorists are reminded to slow down in the wet, to be extra-vigilant when behind the wheel and to avoid driving through floodwater.

Passengers taking public transport are encouraged to check for services impacted by the weather before travelling. Extra care should be taken on platforms and when boarding and getting off public transport, as surfaces can become slippery.

Drivers should leave extra space between themselves and the car in front, as braking distances increase in wet conditions.

The use of headlights is recommended to help see and be seen. Drivers should look out for cyclists and motorbikes which can be harder to see.

If the rain becomes too heavy for wipers to cope, we suggest pulling over safely and waiting for the rain to pass.

Damaging winds will likely result in branches and other debris on the road. Where possible, motorists should move parked cars under cover - away from trees.

Real-time traffic conditions are available at traffic.vicroads.vic.gov.au or via the VicTraffic mobile app. The latest public transport information and network status is available at ptv.vic.gov.au or in the PTV mobile app.a

Update 4.30pm:

STRONG winds up to 98km/h have been recorded in Horsham as power outages affect thousands of people.

Powercor said 1889 customers in Horsham had been affected by a power outage and they were investigating the cause.

They said power was estimated to be restored by 6.30pm on Friday.

Lightning strikes have been seen across the sky and the temperature was still in the high 30s and low 40s across the Wimmera.

There are multiple reports of trees down across the region and visibility has become poor.

Earlier:

AVOID being outside with a dust storm forecast and severe thunderstorm warning bringing high winds, very poor air quality and potentially "muddy rain" in the Wimmera today.

Bureau of Meteorology Victoria said there was a severe thunderstorm warning in place for the Wimmera and parts of Central, Mallee, South West, Northern Country and North Central Forecast Districts.

It said very hot and humid north to northwesterly winds were extending across the west with severe thunderstorms likely to produce damaging winds in the warning area over the next several hours.

Locations which may be affected include Horsham, Stawell, Ararat, Maryborough, Ballarat and Daylesford.

A wind gust of 91km/h was recorded at Stawell and 89 km/h was recorded at Longerenong.

Bureau of Meteorology Victoria senior meteorologist Tom Delamotte said there were very hot conditions across the state, with the north west already experiencing temperatures above 40 degrees.

"It will be a very hot night," he said. "Temperatures will stay in the twenties overnight ahead of a cool change on Saturday just before midday, which will clear out a bit of the humidity.

"We're seeing quite a tropical air mass moving down across South Australia at the moment. That's going to help trigger showers and thunderstorms over western and central parts of Victoria today," he said.

"We are seeing a bit of dust around the air today, it's a bit hazy, that's quite a bit of dust moving down from South Australia from Thursday," Mr Delamotte said.

The Environment Protection Authority Victoria said the dust storm will travel south across the state today beginning in the north west.

The EPA said very poor air quality could lead to people experiencing symptoms like coughing or shortness of breath.

Mr Delamotte said the rain and dust could combind to bring a bit of muddy rain across Victoria.

Friday is a total fire ban for the Wimmera with a severe fire danger rating.

READ MORE: Prepare for tropical conditions and a total fire ban in the Wimmera on Friday

The State Emergency Service advises that people should:

READ MORE: 'Give your dishwasher a rest': Victoria could run out of power today

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