As we head into the winter solstice we are expecting La Niña to return to San Diego, but how will that affect winter? Meteorological winter starts Dec. 1, which is based on temperatures, but winter solstice is based on the Earth’s tilt and how far we are from the sun. The solstice will happen on Saturday, Dec. 21, at 1:20 a.m. when the sun will shine directly over the Tropic of Capricorn in the southern hemisphere, where summer begins at the same time. The northern hemisphere will have the shortest day and longest night, while the opposite happens south of the equator. Now that winter is here, what does that mean for our temperatures and rainfall? When San Diegans think of winter and rain, typically El Niño comes to mind first. But this year, we are heading towards a developing La Niña. El Niño-Southern Oscillation (ENSO) is a recurring climate pattern determined by the warming and cooling over the central and eastern tropical Pacific Ocean. El Niño and La Niña are ways to measure the extreme phases of the ENSO cycle; but it’s not always one or the other, there is a third phase called ENSO-neutral and that is where we are right now, but La Niña shows potential development. However, it’s not so simple. To determine seasonal outlooks, climatologists look at the ENSO phase, as well as rainfall patterns over Indonesia, and the low-level winds over the equator. Rain dance or not? We anticipate La Niña to be weak and that is better for San Diego. A typical strong La Niña would favor rain over the Pacific Northwest, with colder air over the northern plains and Midwest, with drier than normal conditions for Southern California, Texas, and the extreme south. We expect to have chances of rain, while it may not be a stormy season. We do expect storms to bring rain with the potential for some being good rain producers. La Niña is set to develop through the course of our rainiest period, which is January through March. Last year, winter was off to a relatively dry start, but rain picked up during our typical rainy months, January through March. All it takes is a few storms to make a difference and that might be just the way this winter goes. Below you can see the average rain totals for our rainy months and how it compares to the last few years. For perspective, 2024 was an El Niño winter. 2023 was coming off the La Niña into a neutral phase and we ended up with similar totals for the three-month period. Will it get cold? Yes, but not often As far as temperatures, much of the country could see mild temperatures, but we have equal chances at seeing temperature swings. The coldest air will hit Washington state to the northern plains. The coldest air won’t travel far, but some storms could make all the difference. The cold air we experience may not be long-lived. The deserts will continue to see above-normal temperatures, which has been a trend all year long. Besides the seasonal outlook, it’s important to stay up to date with monthly and weekly pattern changes which will give us a better sense of what to expect at least 10 to 15 days out. NBC 7’s First Alert Forecast team has you covered.