“An extended period of moderate to strong Santa Ana winds is expected to impact Southern California this week starting early Monday morning,” Riverside County Fire Chief John Hawkins reported Sunday.

While windy conditions began Sunday night, the winds will intensify today and Tuesday, before diminishing on Wednesday. However, the winds will return Thursday and Friday.

Early Monday morning, the National Weather Service issued both a high wind warning and red flag warning for the Hill.

The High Wind Warning is in effect through Thursday, Dec. 7.

“Areas of northeast winds 20 to 30 mph with gusts to 55 mph. Isolated gusts to 80 mph on Tuesday and Thursday,” was the NWS forecast. "Winds will strengthen this morning and continue at times through Thursday. The strongest and most widespread winds are expected for late tonight into Tuesday...and again late Wednesday night into Thursday."

With the high winds and the wind direction shifting from the northeast, daytime humidity will plummet, possibly to single digits.

A Red Flag Warning means that critical fire weather conditions are either occurring now or may. The combination of strong winds, low relative humidity and warm temperatures contribute to potentially extreme fire behavior, the NWS stated.

The Red Flag Warning was issued about 3 a.m., this morning and is in effect through Thursday, Dec. 7

Humidity will decrease and the chance of fire will increase to moderate over much of the week. By next Saturday, the Santa Ana event should have ended.

By Tuesday, wind speeds could be 25 to 35 miles per hour. At higher elevations and in some of the more wind prone areas, the speeds will approach 60 mph, according to the forecast from the South Operations Predictive Services unit.

On Thursday and Friday, with Santa Ana winds and single-digit humidity, the Inland Empire and San Diego County will be the focus of firefighters for potential ignitions.

“Little if any rain has occurred over Southern California this fall and fuels are very dry. In addition, there is still an abundant grass crop left over from last winter’s heavy rains,” Hawkins wrote noting the fire threat.

The Santa Ana Wildfire Threat Index is High for the Inland Empire on Tuesdy, Dec. 5 and Moderate on Dec. 7 and 8.

The Santa Ana Wildfire Threat Index can be found at the following url: http://sawti.fs.fed.us