Moisture from the western Pacific Ocean, including Typhoon Songda, is expected to arrive in the Sacramento area by late Thursday.
After highs in the mid-80s Monday, the forecast calls for temperatures to head downward. Highs in the 70s are projected through Thursday, before dipping into the 60s on Friday.
A high of 86 degrees was reported in downtown Sacramento on Monday, while the international and executive airports recorded highs of 85 and 84, respectively, said Travis Wilson, a meteorologist with the National Weather Service. A high of 78 is forecast for Tuesday.
The National Weather Service is predicting that the high-pressure system that brought the unseasonably warm fall temperatures in the 90s over the weekend is going away, replaced by a low-pressure system, rain and dramatically cooler days.
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Forecasters say several waves of precipitation late Thursday through Sunday could deliver 1 to 3 inches of rain across the Sacramento Valley and 3 to 8 inches over the mountains. Snow is expected to be limited to areas above the 8,000-foot elevation.
So far, Sacramento has seen just 0.02 inches of rain this month. Normally, the month has an average of 1.05 inches of rain.
The rainfall season started Oct. 1. The detailed forecast from the NWS for the Sacramento region:
Tonight: Mostly clear, with a low around 50. Southwest wind 5 to 8 mph.
Tuesday: Sunny, with a high near 78. South-southeast wind round 6 mph becoming west-southwest in the afternoon.
Tuesday night: Partly cloudy, with a low around 51. South-southeast wind 3 to 5 mph.
Wednesday: Mostly sunny, with a high near 78. Southwest wind 3 to 5 mph.
Wednesday night: Mostly cloudy, with a low around 52. South wind around 7 mph.
Thursday: Partly sunny, with a high near 74.
Thursday night: Rain likely. Cloudy, with low around 58. Chance of precipitation is 60 percent.
Friday: Rain. Mostly cloudy, with high near 67.
Friday night: A chance of rain. Mostly cloudy, with a low around 55.
Saturday: A slight chance of showers. Mostly cloudy, with a high near 69.
Saturday night: A chance of rain. Mostly cloudy, with a low around 57.
Sunday: Rain likely. Mostly cloudy, with high near 68.
Sunday night: A chance of rain. Mostly cloudy, with a low around 52.
Monday: A chance of rain. Mostly cloudy, with a high near 66.