Rain Starts Today, With Colder Temps; Set To Last All Week

National Weather Service forecasters are warning Pasadena residents to prepare for a series of storms that will bring significant rainfall and much colder temperatures through the week. The most powerful system is expected to hit Wednesday night into Thursday morning, potentially dropping 1-2 inches of rain across the area with temperatures plummeting to around 55 degrees by Thursday.

Pasadena will experience cloudy and cool conditions today with high temperatures reaching the low 60s, marking a drop of 6 to 12 degrees from yesterday. Light rain is possible throughout the day as the first, milder storm system moves through the area.

Looking ahead to the next 48 hours, residents should prepare for a brief respite tonight before conditions deteriorate Wednesday. A more powerful storm will develop Wednesday morning, with rainfall intensifying throughout the day.

Pasadena is under a Flood Watch as a major storm system approaches the Southland. The warning, effective from Wednesday evening through Thursday afternoon, cautions residents about potential flash flooding and debris flows, particularly in areas near recent burn scars.

By Wednesday night into Thursday morning, a cold front will bring periods of heavy rain with peak rainfall rates of 0.5 to 0.75 inches per hour. Winds of 30-50 mph are expected to accompany the front.

Temperatures will continue their downward trend throughout the week, with highs tumbling from the low 60s today to the mid-50s by Thursday—approximately 15 degrees below normal for March and more typical of January weather. Overnight lows will dip into the 40s, creating unusually chilly conditions for Pasadena.

The most significant precipitation is forecast for Wednesday night through Thursday. The National Weather Service predicts 1-2 inches of rain across Pasadena, with potentially higher amounts in nearby foothill areas that could see 2-4 inches due to upslope flow. The heavy rain will gradually transition to showers by Thursday morning, with scattered showers continuing throughout the day. There’s also a slight chance of thunderstorms on Thursday, which could produce localized rainfall rates exceeding 1 inch per hour.

Wind conditions will intensify with the approaching storm system. While today brings relatively light winds, Wednesday will see strengthening southerly winds ahead of the cold front. The strongest winds will occur Wednesday night into Thursday morning, with gusts potentially reaching 30-40 mph in the Pasadena area.

The unsettled weather pattern will continue into the weekend, though with less intensity. Current forecasts suggest some clearing may occur Saturday, but another system could bring additional light rain by Sunday. Temperatures will begin a modest recovery, climbing back into the 60s by the weekend.

Pasadena residents should be aware of potential impacts from this weather system, particularly in areas prone to poor drainage. Street flooding is possible during periods of heavy rainfall Wednesday night and Thursday. Foothill communities may experience more significant impacts, with possible debris flows in recently burned areas. Commuters should anticipate slower traffic and potential roadway flooding for both Wednesday evening and Thursday morning commutes.

The National Weather Service has issued a Flash Flood Watch for the area from Wednesday evening through Thursday afternoon. Residents in or below hillside areas should remain alert to changing conditions and be prepared to take action if warnings are issued.

Looking beyond the weekend, long-range forecasts suggest the unsettled pattern may continue into next week, with additional chances for rain on Monday as another system moves through. However, confidence in the timing and intensity of these later systems remains low.

As this significant weather pattern unfolds, Pasadena residents should prepare for a wet and unusually cool week ahead, with the most impactful weather occurring Wednesday night into Thursday. The National Weather Service recommends monitoring forecasts and warnings as the situation develops.

Here is the latest forecast for Pasadena from the National Weather Service as of 3:50 a.m. on Tuesday, March 11:

Tuesday: Rain. High near 59. East southeast wind 5 to 10 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

Tuesday Night: A 30 percent chance of rain before 11:00 p.m. Mostly cloudy, with a low around 48. East wind 5 to 10 mph. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Rain likely, mainly after 11:00 a.m. Mostly cloudy, with a high near 60. East southeast wind 5 to 10 mph becoming south in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday Night: Rain likely, then rain and possibly a thunderstorm after 11:00 p.m. Some of the storms could produce heavy rainfall. Low around 47. South wind 10 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Thursday: Showers and possibly a thunderstorm before 11:00 a.m- then showers likely. High near 56. Chance of precipitation is 100%.

Thursday Night: A 20 percent chance of showers before 11:00 p.m. Partly cloudy, with a low around 39.

Friday: A chance of showers after 11:00 a.m. Partly sunny, with a high near 54.

Friday Night: A chance of showers before 11:00 p.m. Mostly cloudy, with a low around 43.

Saturday: Mostly sunny, with a high near 65.

Saturday Night: Mostly clear, with a low around 45.

Sunday: Mostly sunny, with a high near 69.

Sunday Night: Mostly cloudy, with a low around 48.

Monday: A chance of rain. Partly sunny, with a high near 65.