Isolated storm chances continue through the Labor Day weekend

Tucson residents planning to spend the Labor Day weekend outdoors should be prepared for changing conditions, even as the chance of rain remains limited in the city. Tropical moisture will continue moving into the region, creating opportunities for isolated showers and thunderstorms, particularly east and south of Tucson. The most important concern is not widespread rain, but the possibility of intense downpours that could trigger flash flooding in washes, low water crossings, streets and other flood prone areas.

Storm chances are expected to be greatest during the afternoon and evening, although the timing could vary. Forecast guidance indicates that Friday has the best opportunity for storms near Tucson, with activity more likely east of the city and during the daytime than overnight. Friday’s high is expected to reach about 93 degrees, with a 30 percent chance of rain and thunderstorms. Friday night should be partly cloudy, with a low near 71 and a 20 percent rain chance.

For the rest of the holiday weekend, precipitation chances in Tucson are expected to stay relatively low, generally between 10 and 20 percent from Saturday through Tuesday. Saturday is forecast to be mostly sunny with a high near 94 and a 20 percent chance of showers and thunderstorms. The overnight rain chance drops to 10 percent, with temperatures near 73. Sunday should be mostly sunny and warmer, reaching about 96 degrees, followed by a slight chance of showers and thunderstorms Sunday night and a low near 76.

Labor Day is expected to be mostly sunny, with a high close to 98 degrees. There is a 10 percent chance of showers and thunderstorms Monday night, and a similar chance continues Tuesday, when the high should again approach 98. While the city may stay mostly dry, isolated storms could still produce sudden heavy rain, strong wind or lightning in parts of the county. Conditions can differ sharply from one neighborhood to another, especially near the foothills, mountain ranges and areas east or south of Tucson.

The broader weather pattern is being influenced by moisture associated with the remnants of Hurricane Marie. That moisture is expected to increase shower activity across southwestern Arizona and southeastern California, while higher terrain and eastern Arizona have better rain chances than the Phoenix area. In Tucson, temperatures are expected to remain in the 90s through the seven day forecast, generally normal to a few degrees below normal before warming toward Labor Day.

The forecast becomes wetter again after the holiday. Storm chances rise to 30 percent Tuesday night, 40 percent Wednesday, 50 percent Wednesday night and 40 percent Thursday. Highs are projected to remain in the mid to upper 90s, including about 96 degrees Wednesday and 94 Thursday. That longer term increase means residents should not assume that a dry holiday weekend signals the end of monsoon hazards.

Flash flooding remains the primary threat from any stronger storm. Water can move quickly through normally dry washes and roadways, and drivers should never attempt to cross a flooded street. If water begins rising around a vehicle, drivers and passengers should leave quickly and move to higher ground. People in neighborhoods vulnerable to flooding should be ready to evacuate and should not return until officials say it is safe. Downed power lines can energize nearby ground and standing water, so residents should stay away from both.

The storms also can disrupt electricity, water and gas service. Households should keep flashlights and extra batteries available, store enough water for everyone, maintain food that does not require cooking or refrigeration, and have backup power for phones or medical equipment. A first aid kit and a battery powered or hand crank radio can help during an outage. During a thunderstorm, the safest indoor location is away from windows, skylights and glass doors. Residents should also monitor weather updates and be ready for conditions to change quickly.

Even with occasional rain, heat safety remains important. People hiking, exercising or working outside should drink water before, during and after activity, limit strenuous plans during the hottest part of the day, wear light colored clothing and protect their heads. Phones should be carried, and hikers should tell someone where they are going and when they expect to return. Heat exhaustion can include headache, dizziness, weakness, nausea and cool, damp skin. Confusion, seizures, unconsciousness or a body temperature above 103 degrees can indicate heat stroke, a medical emergency. Residents should check on vulnerable friends, relatives and neighbors, particularly during the warmest parts of the weekend.