Excessive heat warning Saturday afternoon/evening; cooler Sunday

Some smoke from Canadian wildfires will remain in our air into Friday evening, then conditions will improve later Friday night.

The Minnesota Pollution Control Agency continues an air quality alert (shaded orange) across much of Minnesota until 11 p.m. this Friday:

Air quality could reach the orange (unhealthy for sensitive groups) category at times. You can check hourly current air quality readings at the MPCA site.

The Wisconsin Department of Natural Resources has posted an air quality advisory for all of Wisconsin until 11 p.m. Friday. Air quality could reach the orange category.

Here are the various air quality categories that are used by pollution monitoring agencies:

Much of Minnesota had air quality index readings slightly below 100 at 3 p.m. Friday, but a few spots were slightly over 100.

Hot and humid Saturday

Our average Twin Cities high temperature is 81 degrees this time of year.

Saturday high temps will be well into the 90s in many areas, including the Twin Cities:

Dew points will reach the steamy 70s Saturday afternoon:

That combination of heat and moisture will push heat index values over 100 degrees in many locations Saturday afternoon into Saturday evening.

The National Weather Service has issued an excessive heat warning from 1 p.m. to 9 p.m. Saturday from south-central Minnesota through the Twin Cities metro area and several adjacent counties:

A heat advisory (orange) covers many additional counties from 1 p.m. to 9 p.m. Saturday.

Here are details of the excessive heat warning:

URGENT - WEATHER MESSAGE National Weather Service Twin Cities/Chanhassen MN 158 PM CDT Fri Aug 18 2023 MNZ051>053-059>063-065>070-073>077-082>084-091-092-WIZ023-190915- /O.NEW.KMPX.EH.W.0002.230819T1800Z-230820T0200Z/ Sherburne-Isanti-Chisago-Wright-Hennepin-Anoka-Ramsey-Washington- Renville-McLeod-Sibley-Carver-Scott-Dakota-Redwood-Brown-Nicollet- Le Sueur-Rice-Watonwan-Blue Earth-Waseca-Martin-Faribault- St. Croix- Including the cities of Elk River, Cambridge, Center City, Monticello, Minneapolis, Blaine, St Paul, Stillwater, Olivia, Hutchinson, Gaylord, Chanhassen, Chaska, Victoria, Shakopee, Hastings, Redwood Falls, New Ulm, St Peter, Le Sueur, Faribault, St James, Mankato, Waseca, Fairmont, Blue Earth, and Hudson 158 PM CDT Fri Aug 18 2023 ...EXCESSIVE HEAT WARNING IN EFFECT FROM 1 PM TO 9 PM CDT SATURDAY... * WHAT...Dangerously hot conditions with heat index values up to 108 expected. * WHERE...Portions of central, east central, south central and southwest Minnesota and west central Wisconsin. * WHEN...From 1 PM to 9 PM CDT Saturday. * IMPACTS...Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities. PRECAUTIONARY/PREPAREDNESS ACTIONS... Take extra precautions, if you work or spend time outside. When possible, reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear light weight and loose fitting clothing when possible and drink plenty of water. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency, call 9 1 1. An Excessive Heat Warning means that a prolonged period of dangerously hot temperatures will occur. The combination of hot temperatures and high humidity will combine to create a DANGEROUS SITUATION in which heat illnesses are likely. Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances. This is especially true during warm or hot weather when car interiors can reach lethal temperatures in a matter of minutes.

You can hear updated weather information for Minnesota and western Wisconsin on the MPR News network.

Temperature trends

Temperatures retreat a bit on Sunday, with highs ranging from 70s in far northern Minnesota to upper 80s in the far southeast:

Highs in the 90s return to southern Minnesota and the Twin Cities metro area on Monday:

Twin Cities metro area highs are projected to reach the mid 90s on Tuesday and Wednesday.

Rain-free weekend

Most of Saturday and Sunday will be rain-free in Minnesota and western Wisconsin. A stray shower is possible in northwestern Minnesota late on Sunday.

The National Oceanic and Atmospheric Administration’s North American Mesoscale (NAM) forecast model shows the potential rain pattern from 5 a.m. Saturday to 6 p.m. Sunday:

Hurricane Hilary

Hurricane Hilary is a category 4 hurricane in the eastern Pacific, with max sustained winds of 130 mph. Hurricane Hilary is expected to bring destructive winds and flooding rains to Baja California and portions of southern California and Nevada this weekend into early next week.

Here’s the forecast track, plus the cone of uncertainty, for the center of Hurricane Hilary:

Hilary is forecast to be a tropical storm when its center moves over far southern California Sunday night.

Here are potential rain totals for this weekend and into the start of next week:

This is the afternoon update on Hilary, from the NWS National Hurricane Center:

BULLETIN Hurricane Hilary Advisory Number 10 NWS National Hurricane Center Miami FL EP092023 300 PM MDT Fri Aug 18 2023 ...HILARY REMAINS A POWERFUL CATEGORY 4 HURRICANE... ...LIFE-THREATENING AND POTENTIALLY CATASTROPHIC FLOODING LIKELY OVER MUCH OF BAJA CALIFORNIA AND SOUTHERN CALIFORNIA THIS WEEKEND AND EARLY NEXT WEEK... SUMMARY OF 300 PM MDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...18.7N 112.2W ABOUT 80 MI...125 KM W OF SOCORRO ISLAND ABOUT 325 MI...525 KM SSW OF CABO SAN LUCAS MEXICO MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H PRESENT MOVEMENT...NW OR 315 DEGREES AT 12 MPH...19 KM/H MINIMUM CENTRAL PRESSURE...948 MB...28.00 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Mexico has upgraded the Hurricane Watch to a Hurricane Warning on the west coast of Baja California northward to Cabo San Quintin and upgraded the Tropical Storm Watch to a Tropical Storm Warning north of Loreto on the east coast of Baja California and north of Guaymas in mainland Mexico. A Tropical Storm Watch has been extended westward from the Orange/Los Angeles County Line to Point Mugu. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Warning is in effect for... * Baja California peninsula from Punta Abreojos to Cabo San Quintin A Hurricane Watch is in effect for... * Baja California peninsula north of Cabo San Quintin to Ensenada A Tropical Storm Warning is in effect for... * Baja California peninsula from Punta Abreojos southward * Baja California peninsula entire east coast * Mainland Mexico north of Guaymas A Tropical Storm Watch is in effect for... * Mainland Mexico from Huatabampito to Guaymas * Baja California north of Ensenada to the California/Mexico border * California/Mexico border to Point Mugu * Catalina Island A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion. A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Interests in the southwestern U.S. should monitor the progress of Hilary. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 300 PM MDT (2100 UTC), the center of Hurricane Hilary was located near latitude 18.7 North, longitude 112.2 West. Hilary is moving toward the northwest near 12 mph (19 km/h). A turn toward the north-northwest is expected tonight, followed by a faster motion toward the north Saturday night and Sunday. On the forecast track, the center of Hilary will move close to the west coast of the Baja California peninsula over the weekend and reach southern California by Sunday night. Maximum sustained winds are near 130 mph (215 km/h) with higher gusts. Hilary is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Fluctuations in intensity are likely through tonight. Weakening is expected to begin by Saturday, but Hilary will still be a hurricane when it approaches the west coast of the Baja California peninsula Saturday night and Sunday. Hilary is expected to weaken to a tropical storm by late Sunday before it reaches southern California. Hurricane-force winds extend outward up to 50 miles (85 km) from the center and tropical-storm-force winds extend outward up to 275 miles (445 km). The minimum central pressure based on data from the Air Force Hurricane Hunters is 948 mb (28.00 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Hilary can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDEP4 and WMO header WTPZ44 KNHC and on the web at hurricanes.gov/text/MIATCDEP4.shtml. RAINFALL: Hilary is expected to produce rainfall amounts of 3 to 6 inches, with isolated maximum amounts up to 10 inches, across portions of the Baja California Peninsula through Sunday night. Flash and urban flooding, locally catastrophic, will be possible, especially in the northern portions of the peninsula. Heavy rainfall in association with Hilary is expected to impact the Southwestern United States through next Wednesday, peaking on Sunday and Monday. Rainfall amounts of 3 to 6 inches, with isolated amounts of 10 inches, are expected across portions of southern California and southern Nevada. Dangerous to locally catastrophic flooding will be possible. Elsewhere across portions of the Western United States, rainfall totals of 1 to 3 inches are expected, resulting in localized flash flooding. WIND: Hurricane conditions are expected within the hurricane warning area beginning Saturday night and are possible within the hurricane watch by early Sunday. Tropical storm conditions are expected within the warning area tonight, and are possible within the watch area in Mexico on Saturday and Sunday and in southern California beginning late Sunday. STORM SURGE: A dangerous storm surge is likely to produce coastal flooding along the western Baja California peninsula of Mexico near where the center passes the coast in areas of onshore winds, or east of the center if Hilary makes landfall. The surge will be accompanied by large and destructive waves. SURF: Large swells generated by Hilary will affect portions of the coast of southwestern Mexico, the Baja California peninsula, and south California over the next few days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

The National Hurricane Center will issue updates on Hilary every three hours or so.

Programming note

You can hear my live weather updates on MPR News at 7:35 a.m., 9:35 a.m. and 4:39 p.m. each Saturday and Sunday.