Story highlights Parts of the city have gotten 3 inches of rain since late Friday morning

Houston typically begins to flood after 2 or 3 inches of rain over a short period

(CNN) Bands of heavy rain from Hurricane Harvey began pummeling Houston early Saturday as the flood-prone city braced for what could be several days of downpours as the monster storm hovers over Texas.

A flash-flood watch was in effect Saturday for the Houston area, according to the National Weather Service. More than a foot of rain could fall in the city over the next five days, with higher tallies possible in localized areas, CNN meteorologists said.

By 10 a.m. ET, some parts of Houston already had gotten more than 3 inches of rain over the prior 24 hours, the weather service reported.

And more heavy rain was expected, with Harvey due to stall for days over southeast Texas. The system could maintain tropical storm strength through early Wednesday, then weaken into a tropical depression, the weather service predicted