A spooky, stormy Halloween weekend ahead

Tucson residents should be prepared for rapidly changing conditions this Halloween weekend, with rain, thunderstorms, strong winds and possible flash flooding all part of the outlook. The most immediate concern is for Friday, when scattered showers and storms are expected in the morning before becoming more widespread during the afternoon and evening. People heading to work, school, outdoor events or Halloween activities may encounter wet roads, gusty winds and sudden downpours, especially north and northeast of Tucson.

The Friday forecast calls for Tucson temperatures to remain a few degrees below average. Most locations are expected to receive between a quarter-inch and three-quarters of an inch of rain, though isolated areas could collect 1 to 2 inches. Some thunderstorms may produce strong wind gusts and small hail. Heavy rainfall could also create isolated flash flooding, with washes and other drainage areas posing particular risks if storms repeatedly move across the same locations.

The weather is expected to ease for a short time on Halloween. The forecast calls for only a 10% to 20% chance of a passing shower Saturday, offering a temporary break for trick-or-treaters and people making weekend plans. That pause may not last, however. A stronger storm system is expected to arrive Saturday night, bringing widespread rain and scattered thunderstorms from Sunday into Monday.

A Flood Watch is scheduled to be in effect from 11 p.m. Saturday through 5 a.m. Monday across most of Pima, Pinal, Santa Cruz, Graham and Greenlee counties. Some areas could see 1 to 2 inches of rain or more during that period, increasing the chance of flash flooding in locations that are vulnerable to runoff. Residents are advised to use caution near washes and low-water crossings because water levels can rise quickly, even when conditions nearby appear manageable.

The forecast information also includes a drier and warmer outlook for southeast Arizona before the next round of unsettled weather. One forecast calls for sunny skies and a high near 93 on Friday, with temperatures reaching about 96 Saturday and remaining near 94 Sunday. That outlook places the greater chance for showers and thunderstorms on Monday, when the chance of rain rises to 50% during the day and 60% Monday night. It also describes deep tropical moisture moving north from the south Monday and Tuesday, followed by another weather system from the West Coast that could produce widespread showers, thunderstorms and below-normal afternoon temperatures.

Taken together, the forecasts point to a weekend that may shift quickly from sunshine and warm conditions to stormier weather. The timing and intensity of rain may vary across the region, which is common during unsettled weather. For Tucson residents, the practical concerns are the same: check conditions before leaving, allow extra time on wet roads, avoid flooded crossings and do not assume a dry stretch means nearby washes are safe. Rain chances are expected to taper Monday morning, with drier conditions forecast from Tuesday through Thursday.

Halloween also brings a separate kind of storm story in the sky. EarthSky is looking back at the powerful solar events of Halloween 2003, when two major eruptions from the sun sent coronal mass ejections toward Earth. The first followed an X17 flare on October 28, and the second followed an X10 flare on October 29. Both produced G5 geomagnetic storms, the strongest classification used for geomagnetic activity. The events disrupted or affected satellites, forced several NASA spacecraft into protective modes and caused extra drag in low Earth orbit, making it harder for operators to track some satellites.

The current solar outlook is far quieter than that historic episode. Solar activity was described as very low, with only B-class flares observed during the reporting period and no new coronal mass ejections identified in available imagery. A coronal mass ejection launched October 26 could deliver a glancing blow, while a high-speed stream from a coronal hole may also disturb Earth’s magnetic field. Forecasters said a minor G1 geomagnetic storm was possible around Halloween and November 1, with auroras potentially visible as far south as Maine and Michigan. That forecast does not place Tucson in the expected viewing area, but it adds another unusual element to a weekend already marked by unsettled conditions on the ground.

For Tucson, the main message remains weather safety rather than a rare celestial display. Friday’s storms could bring heavy rain, hail and strong winds, while the more significant flooding threat is expected from Saturday night through Monday. Even if Halloween itself stays mostly dry, residents should be ready for conditions to deteriorate later in the weekend and should keep checking updated forecasts before traveling or spending time near washes and low-water crossings.