A strong high pressure system will shift back over the Desert Southwest early this week leading to hotter temperatures and overall fairly dry conditions. This high pressure system is expected to persist over the region all week, with at most day-to-day high terrain monsoon activity across eastern Arizona. Starting today, temperatures will rise to around 5-7°F above average as Major HeatRisk developing across the lower deserts. An Extreme Heat Warning is in effect for the lower deserts of AZ and southeast CA today through Friday, with the San Carlos area in southern Gila County joining in the warning starting on Tuesday.