Chilly temperatures today are expected to be a prelude to a wet week as the Sacramento region experiences five days of wintry conditions. A frost advisory by the National Weather Service warns of temperatures in the lower to mid 30s across the Sacramento Valley this morning. By 6 a.m., temperatures had dipped to 39 degrees in downtown Sacramento, 37 degrees at Sacramento's Executive Airport in South Sacramento and 33 degrees at Sacramento International Airport. "They still could drop some more," said NWS forecaster Johnnie Powell.