The weather in Monrovia in September is very hot. The average temperatures are between 77°F and 80°F, drinking water regularly is advisable.
With more than 22 rainy days, Monrovia is an incredibly wet during September. Be sure to pack your umbrella and bring along your rubber boots to stay dry. It’s going to be raining cats and dogs this month!
Our weather forecast can give you a great sense of what weather to expect in Monrovia in September 2025.
If you’re planning to visit Monrovia in the near future, we highly recommend that you review the 14 day weather forecast for Monrovia before you arrive.
Temperatures
80° / 77°
Rainy Days
23
Snowy Days
0
Dry Days
7
Rainfall
26.1
in
Sun Hours
9.0
Hrs
