Tornado risk in western Renfrew County Tuesday

Environment Canada says there's arisk of a tornado in western Renfrew County on Tuesday, and has issued a rainfall warning and severe thunderstorm watch for most of western Quebec lasting through early Wednesday.

The severe thunderstorm watch, which includes the tornado risk,coversRenfrew County west of Petawawa and Barry's Bay on Tuesday afternoon and evening.

A tornado watch is issued when there's a storm approaching with conditions that could produce a tornado. A warning goes out either when atornado sighting has been reportedor when there's sufficient evidence to suggest a tornado is on the way.

When a tornado forms,people are advisedto stayaway from exterior walls and windows, ideally going to a basement or the ground floor. They should alsoget out of vehicles.

• Here's what to do during a tornadoalert

Along with the tornado risk and lightning, Environment Canada says these storms can bringstrong wind gusts, hail and heavy rain.

Renfrew County also has a special weather statement about 60 millimetres as the top-end forecast from late afternoon into Wednesday. A significant amount of that could fall in an hour and trigger a rainfall warning there.

Pembroke's daily rainrecord of about 26 millimetres on Aug. 27, 1997 could be broken.

Up to 75 mm under rain warning

Another thunderstorm watch covers the Outaouais, except for Gatineau and its easternmost communities such as Grenville, Places east of Quyon could get 20 to 40 millimetres of rain and to the west, about 50 millimetres.

Those more western communities are under a rainfall warning.

If a few thunderstorms hit there, more rain than that could fall. The warning floats 75 millimetres of rain as a possibility by morning.

Ottawa is forecast to get 15 to 25 millimetres of rain overnight.

Environment Canada warns the rain could causeflash floods and water pooling on roads.

In preparation for a flood,Environment Canada advisespeople to learn how to shut off their utilities and safeguard heating equipment, along with keeping sandbags and emergency kits.

In the case of a flood, don't try to walk through the water even if it looks shallowand also avoid driving through it.

Precipitation trends vary across the Ottawa-Gatineau region: Ottawa was having a drier year than usual until early summer, while Kingston is still about 200 millimetresbelow average so far this year.