San Diego’s weather in 2018 was almost uniformly warm and dry. Until late in the year, when it was neither. 2019 begins with its own personality: cool days and cold nights, with a couple of storms over the next week that should get the month off to a fairly wet start. Rain is expected to begin Saturday night and continue off and on through Sunday evening. Another storm should arrive Wednesday or Thursday, according to the National Weather Service. That’s quite a change from the bulk of 2018 — until December arrived.