Typhoon Gaemi and a southwest monsoon brought heavy rain on Wednesday (Jul 24) to the Philippine capital region and northern provinces, prompting authorities to halt work and classes, while stock and foreign exchange trading were suspended.

The presidential office suspended classes at all academic levels and work in most government offices in the capital region, which is composed of 16 cities and home to at least 13 million people.

Rescuers were deployed across Manila to help evacuate people from low-lying homes after downpours turned streets into rivers.

"Many areas are flooded so we have rescuers deployed all over the city. There is an overwhelming number of people asking for help," Peachy de Leon, a disaster official in suburban Manila, told AFP.

"We were told last night the rain will not hit us, then the rain suddenly poured so we were quite shocked. There is an ongoing search and rescue now."

Gaemi, with maximum sustained winds of 155kmh and gustiness of up to 190kmh, was heading towards Taiwan after sweeping past the Philippines.

It did not make landfall but it is enhancing a southwest monsoon, resulting in heavy to intense rain in northern Philippines, the weather agency said.

"Usually the peak of rainy season is July and August and it so happens that there is a typhoon in the eastern waters of the Philippines that enhances the southwest monsoon," senior weather specialist Glaiza Escullar told AFP.

Gaemi and another tropical storm, Prapiroon, hit the southern Philippines and caused floods last week, resulting in seven deaths.

The Philippine coastguard said 354 passengers and 31 vessels were stranded in ports while airlines cancelled 13 flights on Wednesday, Manila's airport authority said.

The Philippines sees an average of 20 tropical storms annually, causing floods and deadly landslides.