South Wales Police has declared a "major incident" after the severe weather forced people out of their homes, caused disruption to roads and transport as well as some communities being hit by landslides.
It said emergency services, local authorities, health boards and organisations including Mountain Rescue, Natural Resources Wales and utility companies, are working together to ensure the safety of those affected, minimise damage to homes and businesses, and disruption.
Some communities have been cut-off as a result of the severe weather and residents have been evacuated from their homes.
Police said many rescues have been carried out over the past few hours along the evacuation of houses.
Local authorities across the region have set up emergency centres for residents who have been displaced.
South Wales Fire and Rescue service said it had received more than a thousand calls relating to flooding since midnight, resulting in crews performing 76 rescues with more than 30 "ongoing incidents".
It confirmed a man in his sixties died after falling into the River Tawe in the Swansea Valley. Police said his body was found around seven miles downstream in the Trebanos area.
South Wales Police said its officers will "continue to work tirelessly until all risks dissipate"
Police have issued the following advice for people in affected areas:
Remain indoors, unless your journey is absolutely necessary.
Steer well clear of dangers such as waterways.
In an emergency, dial 999 – let highly skilled emergency service and rescue staff deal with incidents safely.
Monitor local media and social media accounts for relevant organisations for updates.
This video shows a rescue helicopter winching people to safety in Crickhowell:
Welsh Water said its crews are currently dealing with the impact of the extreme weather on their sites. They said they have been working throughout the night in floods to help maintain supplies to customers.
Natural Resources Wales said their teams are out 24/7 to measure the flood levels.