Nearly all of Nova Scotia is under a weather warning for heavy rain that could lead to flooding and prolonged power outages this weekend. 

CBC meteorologist Kalin Mitchell says the interaction of three weather systems — a low-pressure system combined with a cold front over the Saint Lawrence Valley and a low-pressure system over the Bahamas — will bring tropical moisture to the Maritimes.

Nova Scotia is in the path of heavy downpours and high and gusty southerly winds.

Here's a breakdown of what to expect:

When can we expect the heaviest rain?

Preliminary bands of rain have already arrived. That will be followed overnight and Saturday with tropical moisture, which will trigger the heavier downpours.

Expect that to start near or after midnight in Digby, Yarmouth and Shelburne counties then spread to the Halifax area by 2 a.m. to 4 a.m. on Saturday.

Then, the rain will move across the mainland by 6 a.m. and across Cape Breton by 6 a.m. to 9 a.m.

NS Weather 20110729

As much as 80 millimetres of rain could fall on parts of Nova Scotia starting Friday afternoon. (Andrew Vaughan/The Canadian Press)

There will be lulls in the rain and downpours, but it won't be completely clear of Nova Scotia until mid to late Saturday.

How much rain will we get?

Amounts will generally total 30 to 50 millimetres for the province, with higher local amounts of 70 or 80 millimetres possible.

weather radar

Here's how much rain Nova Scotia can expect Friday and Saturday. (Kalin Mitchell/CBC)

Don't be deceived by the amounts — the important note is that the rain will come in downpours.

Watch for hydroplaning conditions and localized flooding. Rainfall warnings are in effect for many areas; you can check here for warnings or weather statements for your area.

How strong will the wind be?

Winds will continue to increase Friday night reaching widespread, southeast gusts of 50 km/h to 80 km/h on Saturday. Due to the topography of the Cape Breton Highlands, gusts in Inverness County are likely to exceed 100 km/h.

The winds turn southwest Saturday night into Sunday morning. They will still be high, with gusts of 50 km/h to 80 km/h.

Winds are expected to slowly diminish late Sunday into Monday.

Will it be strong enough to cause power outages?

The wind won't be strong enough to trigger a warning, which comes with sustained 70 km/h winds or gusts of 90 km/h.

But, the prolonged windiness and the downpours could lead to power outages.

Keep portable devices charged and have an emergency plan that includes being able to go 72 hours without power or running tap water. The last storm knocked power out for more than 80,000 Nova Scotia Power customers, including some who had to wait three days to get it back.

What about the tides?

No storm surge warnings have been issued, but the sustained winds will be onshore for many coastal areas including the Atlantic coast.

Rougher than normal surf and higher than normal water levels during high tides are expected. Strong and gale force wind warnings have been issued for the marine areas.

Rain feast or famine, depending on where you are

Rain would be a welcome sight in drought-stricken areas of southwest Nova Scotia but could be tough in areas of Cape Breton that had a record-setting 225 millimetres of rain fall in one day over Thanksgiving weekend.

Cape Breton Regional Municipality said on Thursday its infrastructure should be able to handle 30 or 40 millimetres of rain, but if it were to get 100 millimetres in such a short period of time there could be problems.

Public works crews in the municipality are preparing for the worst and hoping for the best. The municipality is asking people to prepare for more power outages and high water.

With files from Jim Abraham, Cassie Williams