Montebello runs from flat residential up into the hills, and the elevation change matters. The flat areas behave like the rest of the region; the hillside properties have drainage problems of their own.
On a slope, water arrives with momentum and volume during a storm and it goes where the ground sends it. A retaining wall with a blocked drain becomes a dam holding water against a structure.
What goes wrong in Montebello properties
Hillside drainage failures and garages cut into slopes account for most of the storm-season work. Retaining wall weep holes silt up and nobody checks them until water is inside.
In the flatter neighborhoods it is ordinary residential plumbing in ageing houses, with slab leaks and water heaters leading.
What should I check before the rainy season?
Clear the drains and weep holes in any retaining wall, confirm downspouts discharge away from the building, and make sure the ground still falls away from the walls. Soil settles over the years.
Water came into the garage from the hillside. Now what?
Extraction and drying first, then look at why it arrived. A garage that takes water once will take it again, and the fix is outside rather than inside.