A natural El Nino, human-caused climate change, a stubborn heat dome over the nation’s midsection and other factors cooked up Tropical Storm Hilary’s record-breaking slosh into California and Nevada, scientists figure.

Cooked up is the key phrase, since hot water and hot air were crucial in rapidly growing Hilary and then steering the storm on an unusual path that dumped 10 months of rain in a single weekend in normally bone-dry places. Nearly a foot of rain fell in parts of Southern California’s mountains, while cities smashed summertime records.

“It was a combination of sort of a perfect situation of everything coming together in a way that made the storm possible,” said University of Albany atmospheric scientist Kristen Corbosiero, an expert on Pacific hurricanes.

It’s never easy to attribute a single event to climate change, especially so quickly and with El Nino being a prominent factor, said former National Oceanic and Atmospheric Administration hurricane and climate scientist Jim Kossin, now with the nonprofit First Street Foundation.