Pasadena Temperatures to Drop Sharply as Rain Chances Increase Ahead of Halloween Weekend

Pasadena residents can expect a steady cooling trend this week, with daytime temperatures falling from near 80 degrees to the mid-60s by Halloween weekend as cloud cover increases and rain chances rise, according to the National Weather Service.

Tuesday is forecast to be the warmest day of the week, with sunny skies and a high near 79 degrees. Light south-southwest winds around 5 mph are expected during the afternoon. Overnight, patchy fog may develop after 11:00 p.m. as clouds increase and temperatures fall to about 54 degrees.

The cooling trend will continue Wednesday and Thursday. Wednesday is expected to begin with patchy fog before skies become mostly sunny. The high temperature is forecast to reach 78 degrees. Wednesday night will be mostly cloudy with a low near 55 degrees.

Thursday will be partly sunny with a high near 76 degrees, followed by mostly cloudy conditions Thursday night and a low around 56 degrees.

National Weather Service forecasters said a weak trough of low pressure and persistent onshore flow will gradually lower temperatures through the week while increasing cloud coverage across Southern California.

The most significant temperature change is expected by Friday, when Pasadena’s high is forecast to reach only 68 degrees. That would represent an 11-degree drop from Tuesday’s expected high.

Rain chances begin to enter the forecast Friday night, when a slight chance of showers is expected under mostly cloudy skies. Forecasters said confidence remains high that rain will affect Southern California during the weekend, although the exact timing and rainfall amounts remain uncertain.

Saturday, which falls on Halloween, is expected to be mostly cloudy with a high near 66 degrees and a chance of showers developing after 11:00 a.m. Shower chances are forecast to continue Saturday night and Sunday, when temperatures are expected to remain cool with a high near 67 degrees.

The National Weather Service said Saturday and Sunday currently appear to have the highest potential for rainfall as a developing storm system approaches the region. Forecast discussions indicate most areas south of Point Conception could receive around an inch of rain, though forecasters noted confidence in specific rainfall totals remains low.

Winds are expected to remain relatively light throughout the forecast period, generally around 5 mph during the afternoon hours with calm conditions at night and during the morning.

Following the weekend system, conditions are expected to improve Monday. Sunny skies are forecast to return, with temperatures warming slightly to around 71 degrees.

Forecasters also said an active weather pattern may continue into next week, with additional opportunities for precipitation possible across Southern California.

Here is the Pasadena forecast from the National Weather Service as of 11:01 p.m. Monday:

Today: Sunny, with a high near 79. Calm wind becoming south southwest around 5 mph in the afternoon.

Tonight: Patchy fog after 11:00 p.m. Otherwise, increasing clouds, with a low around 54. South southwest wind around 5 mph becoming southeast in the evening.

Wednesday: Patchy fog before 11:00 a.m. Otherwise, cloudy, then gradually becoming mostly sunny, with a high near 78. Calm wind becoming south around 5 mph in the afternoon.

Wednesday Night: Mostly cloudy, with a low around 55. South southwest wind around 5 mph becoming calm in the evening.

Thursday: Partly sunny, with a high near 76. Calm wind.

Thursday Night: Mostly cloudy, with a low around 56.

Friday: Partly sunny, with a high near 68.

Friday Night: A slight chance of showers. Mostly cloudy, with a low around 55.

Saturday: A chance of showers, mainly after 11:00 a.m. Mostly cloudy, with a high near 66.

Saturday Night: A chance of showers. Mostly cloudy, with a low around 54.

Sunday: A chance of showers. Mostly cloudy, with a high near 67.

Sunday Night: Partly cloudy, with a low around 52.

Monday: Sunny, with a high near 71.