The high of 95 degrees at Ontario was three degrees higher than the previous mark for the day, according to Accuweather Inc.
Tuesday will be about 92, according to the forecast, which will be just one degree short of the record for a Nov. 6 set six years ago.
However, the warm days will soon be leaving town, and quickly, starting Wednesday. And there's even a chance of showers on Friday.
Accuweather predicts a high of about 81 on Wednesday, dropping to the mid-60s on Thursday and near 60 on Friday.
The weekend outlook is for partly cloud skies but with the mercury staying no higher than the upper 60s.