If you are heading out tonight, you may want to bring an umbrella.

Environment Canada has placed Toronto and the entire GTA under a rainfall warning in advance of the arrival of a system that could bring total rainfall amounts of 20 to 40 millimetres.

The weather agency says that the rain will begin this evening and will continue throughout the night and into the early morning hours before changing to snow on Saturday.

“Rainfall, combined with melting snow, is expected. The frozen ground has a reduced ability to absorb this rainfall,” the warning states.

Due to the amount of snow that remains on the ground, there is an additional risk of flooding posed by the rain.

Eric Holmes, who is a spokesperson for the city, said that work has been ongoing over the last few days to clear out catch basins before the system arrives.

He said that residents are also being encouraged to clear out the catch basins near their homes.

“We sort of watched this forecast coming in recognizing that there is still snow on the ground and some snow banks over catch basins, so our staff made the call to have crews go out in the last few days and clear some of those catch basins,” he said. “Because of the snow they were really all over the city trying to get the catch basins cleared.”

In addition to the rainfall warning, the Toronto Region Conservation Authority has issued a flood outlook for the entire GTA.

They say that a “combination of accumulated snow, high rainfall and the frozen ground conditions will result in runoff from rain and snowmelt” that could create “hazardous conditions” near rivers, streams and other bodies of water.

The temperature is expected to hover around 0 C tonight. A high of 1 C is in the forecast for Saturday.