* WHAT. High temperatures in the upper 80s to upper 90s expected. * WHERE. San Diego County Mountains. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Hot temperatures may cause heat illnesses. * ADDITIONAL DETAILS. Hottest conditions expected over the weekend.

* WHAT. High temperatures in the upper 80s to upper 90s below 5000 feet expected. Low temperatures in the mid 60s to mid 70s below 5000 feet. * WHERE. Riverside County Mountains and San Bernardino County Mountains. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Hot temperatures may cause heat illnesses. * ADDITIONAL DETAILS. Hottest conditions expected over the weekend.

* WHAT. Hot conditions with high temperatures in the upper 90s to 104 expected. Low temperatures in the upper 60s to upper 70s near the foothills. * WHERE. San Bernardino and Riverside County Valleys-The Inland Empire. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Hottest conditions expected over the weekend.

* WHAT. Hot conditions with high temperatures in the 90s expected. Low temperatures in the upper 60s to upper 70s. * WHERE. Santa Ana Mountains and Foothills. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Hottest conditions expected over the weekend.

* WHAT. Hot conditions with high temperatures for the inland valleys in the 90s to 102. Low temperatures in the upper 60s to mid 70s for the far inland valleys near the foothills of the mountains. * WHERE. San Diego County Valleys. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Hottest conditions expected over the weekend.

* WHAT. Dangerously hot conditions with high temperatures of 106 to 112 expected. Low temperatures in the mid 70s to upper 80s. * WHERE. Coachella Valley and San Diego County Deserts. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. Warm overnight temperatures will lead to less relief from the heat, prolonging impacts. * ADDITIONAL DETAILS. Well above average temperatures will continue through early next week.

* WHAT. Dangerously hot conditions with high temperatures of 110 to 115. Low temperatures in the 80s. High temperatures will be 10 to 20 degrees above averages. Slight cooling is expected on Tuesday. * WHERE. Coachella Valley and San Diego County Deserts. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Major HeatRisk from excessive temperatures.

* WHAT. Dangerously hot conditions with high temperatures of 90 to 100F. This is 10 to 20 degrees above normal. Low temperatures of 65 to 75 degrees, warmest in the foothills. * WHERE. San Diego County Valleys and Foothills. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Widespread moderate and areas of major HeatRisk.

* WHAT. Dangerously hot conditions with high temperatures of 90 to 100F. Low temperatures 65 to 70. * WHERE. Santa Ana Mountains and Foothills. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Moderate to locally major HeatRisk.

* WHAT. Dangerously hot conditions with high temperatures 100 to 105 this weekend and near 100 on Monday. This is 15 to 20 degrees above averages. Low temperatures 65 to 72, warmest in the higher terrain. * WHERE. San Bernardino and Riverside County Valleys-The Inland Empire. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. Major HeatRisk for weekend.

* WHAT. High temperatures 90 to 100 across the mountains and foothills. * WHERE. Riverside County Mountains and San Bernardino County Mountains. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Hot temperatures may cause heat illnesses.

* WHAT. High temperatures of 88 to 98 in the mountains and foothills. Low temperatures in the mid 60s to lower 70s. * WHERE. San Diego County Mountains. * WHEN. Until 8 PM PDT Monday. * IMPACTS. Hot temperatures may cause heat illnesses. * ADDITIONAL DETAILS. Moderate HeatRisk can be dangerous for outdoor activities.