Flood Watch issued for southern Arizona

People in Tucson and across southern Arizona should prepare for a higher risk of localized flash flooding as a Flood Watch takes effect from 11 p.m. Tuesday through 11 p.m. Wednesday. The region is entering an active stretch of monsoon weather, with showers and thunderstorms possible each day and some storms capable of producing rainfall at a rate of 1 to 2 inches per hour. That intensity can quickly overwhelm washes, low water crossings, streets, and other areas that collect runoff, even if heavy rain is limited to a small part of the city or surrounding communities.

Tuesday’s forecast calls for a 50 percent chance of showers and thunderstorms after 11 a.m. Tucson is expected to reach about 91 degrees under partly sunny skies, with light winds shifting from the southeast. Storm chances continue overnight at 40 percent, as skies become mostly cloudy and temperatures fall to around 72 degrees. The limited coverage expected Tuesday does not eliminate the flooding concern, because individual storms can still produce intense rainfall over a short period.

Wednesday is expected to be the wettest and most unsettled day in the immediate forecast. There is an 80 percent chance of precipitation, with showers and thunderstorms possible during the day and showers becoming more likely after 2 p.m. The high should be near 88 degrees, followed by a low around 72 Wednesday night. Showers and possibly a thunderstorm are likely before 8 p.m., with additional storm chances afterward. The forecast places the chance of rain at 60 percent Wednesday night.

The weather pattern is part of a broader increase in monsoon activity across Arizona. In the high country, storms have already produced flash flood warnings, flood advisories, and severe weather. Storms are expected to move southwest through the state, spreading the threat of heavy rain beyond mountain areas. Thursday and Friday are expected to bring an even greater flash flood risk statewide, along with the possibility of damaging wind gusts and hail. Southern Arizona is included in the areas where showers and storms may develop Thursday morning, with storms expected to form over the mountains around midday before moving southwest.

For Tucson residents, that movement can make conditions change quickly between neighborhoods and communities. A storm that develops east or south of the city can send runoff into normally dry channels, while rain falling elsewhere in the watershed can affect roads some distance from where the storm is visible. Anyone driving should avoid entering water covering a roadway. If water begins rising around a vehicle, drivers and passengers should leave quickly and move to higher ground, provided it can be done safely. Downed power lines also present a danger, since standing water near them may be energized.

The broader Arizona forecast calls for storm chances to continue beyond the Flood Watch, although coverage is expected to become more scattered or isolated over the weekend. Rain chances in the Phoenix area are projected to fall to about 20 percent, with Sunday currently appearing to be the least likely day for storms. Temperatures there are expected to drop into the upper 90s Friday and Saturday, but high humidity could make it feel like the low 100s. Storm chances remain possible into next week, when warming could push Phoenix temperatures back between 100 and 105 degrees. In Tucson, the near term forecast shows a high near 91 Thursday, followed by mostly sunny conditions and a 20 percent storm chance. A high near 95 is forecast Monday, with smaller storm chances continuing into Tuesday.

The combination of heat, humidity, heavy rain, wind, and dust means residents should prepare for more than flooded streets. Weather officials and emergency agencies recommend having flashlights and extra batteries, a first aid kit, drinking water, food that does not require cooking or refrigeration, and backup power for phones or essential medical equipment. Households should identify an interior location away from windows, skylights, and glass doors where people can shelter during strong winds or hail. Those who live in areas prone to flooding should be ready to leave quickly if conditions worsen or officials issue an evacuation order.

Outdoor activity also requires caution, even when storms bring cooler air. Health officials advise limiting strenuous activity during the hottest part of the day, drinking water before, during, and after time outdoors, and checking on older adults, neighbors, and others at risk of heat illness. Warning signs of heat exhaustion include headache, dizziness, weakness, nausea, heavy sweating, and cool, moist skin. Confusion, seizures, unconsciousness, or a body temperature above 103 degrees can indicate heat stroke, which is a medical emergency. A person showing serious symptoms should be cooled with wet cloths and fans, but should not be given anything by mouth if they are vomiting, unable to swallow, or unconscious.

Conditions can change rapidly during monsoon storms, so residents should monitor local forecasts and official warnings through the Flood Watch period and afterward. People should never attempt to cross moving water on foot or in a vehicle, and should turn around rather than continue onto a flooded road. Residents can call 511 for Arizona road information or 1-888-411-7623. The active pattern is expected to continue with daily opportunities for storms, making it important for Tucsonans to remain alert even on days when overall storm coverage appears limited.