NWS Forecast for Diamond Bar CA

National Weather Service Forecast for: Diamond Bar CA
Issued by: National Weather Service Los Angeles/Oxnard, CA

Updated: 3:42 pm PDT Jul 12, 2026

This Afternoon Partly Sunny	Tonight Partly Cloudy	Monday Partly Sunny	Monday Night Patchy Fog	Tuesday Patchy Fog then Sunny	Tuesday Night Mostly Clear	Wednesday Hot	Wednesday Night Mostly Clear	Thursday Mostly Sunny
Hi 87 °F	Lo 67 °F	Hi 90 °F	Lo 68 °F	Hi 96 °F	Lo 69 °F	Hi 101 °F	Lo 72 °F	Hi 95 °F

Heat Advisory
Extreme Heat Watch

This Afternoon	Partly sunny, with a high near 87. Southwest wind around 10 mph.
Tonight	Partly cloudy, with a low around 67. Southwest wind 5 to 10 mph.
Monday	Partly sunny, with a high near 90. Light southwest wind becoming west southwest 5 to 10 mph in the morning.
Monday Night	Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 68. Southwest wind 5 to 10 mph becoming light in the evening.
Tuesday	Patchy fog before 11am. Otherwise, mostly sunny and hot, with a high near 96. Light southwest wind becoming west southwest 5 to 10 mph in the morning. Winds could gust as high as 15 mph.
Tuesday Night	Mostly clear, with a low around 69.
Wednesday	Sunny and hot, with a high near 101.
Wednesday Night	Mostly clear, with a low around 72.
Thursday	Mostly sunny, with a high near 95.
Thursday Night	Partly cloudy, with a low around 68.
Friday	Mostly sunny, with a high near 89.
Friday Night	A slight chance of showers. Partly cloudy, with a low around 66.
Saturday	A slight chance of showers. Mostly sunny, with a high near 89.

Forecast from NOAA-NWS for Diamond Bar CA.