Flooding in California this month has affected thousands of properties as heavy snow followed by “atmospheric river” storm systems increased risks in many locations, Finnish-based natural catastrophe data company Iceye says.

A total of 2933 properties have been impacted, with an average inundation depth at building level of 32.15 cm, including 390 buildings incurring flooding of 61-152 cm and 56 at deeper levels, the data released last week shows.

The firm’s analysis is focussed on the regions most affected, including Pajaro, Porterville, San Jose, Salinas, Visalia, Gilroy, Watsonville, Old River, San Joaquin River, Sacramento River, Salinas River and the Sierra Foothills.

“When the warm ‘atmospheric rivers’ hit they brought extensive heavy rainfall and triggered extremely rapid snowmelt, resulting in widespread flooding within a very short period,” Iceye meteorologist Brandon Wright said.

“Unlike rain-based flood events where there is often a delay between the weather system impacting and the floods commencing, the flooding we witnessed in California was almost instantaneous due to the accelerated snowmelt.”

The flooding, which started on March 10, was analysed using imagery from satellites and ground-source data.