Monsoon Season in Surprise, Arizona

NWS Phoenix dates the North American Monsoon season from June 15 to September 30 in its review of the 2025 season across the Desert Southwest (NWS Phoenix, 2025 Monsoon Season Review).

The Youngtown cooperative station normally records under an inch of rain in each monsoon month, and its 1991 to 2020 normals show how the season builds: June averages 0.03 inches, July 0.84, August 0.97 and September 0.74 (NOAA ACIS). August is the wettest month of the monsoon at the station, yet February, at 1.25 inches, is wetter than any summer month. The county Flood Control District says the intense rains of summer monsoon storms bring flash flooding to usually dry washes (Flood Control District of Maricopa County, Monsoon).

One season can depart from those normals. NWS Phoenix's review of 2025 says that for the third consecutive year much of the Desert Southwest had below normal monsoon rainfall, while south-central Arizona, including the Phoenix metropolitan area, recorded above-normal rain tied to a couple of intense events mostly in September; the first part of the season, June 15 through August 15, was notably inactive (NWS Phoenix, 2025 review).

Last verified: October 19, 2026, with fresh reads of the NWS Phoenix monsoon safety page and 2025 season review, the Youngtown normals, the county Flood Control District pages, Surprise's monsoon page and FEMA's listing for community 040053.

Of the NWS Phoenix monsoon products, the Flash Flood Warning and the Severe Thunderstorm Warning carry immediate instructions: move to higher ground now, and move into a central interior room (NWS Phoenix, Monsoon Safety).

NWS Phoenix describes a ladder of products for monsoon storms across its region. A Flash Flood Warning means life-threatening rapid flooding is about to occur or is under way, and a Severe Thunderstorm Warning is issued for damaging winds of 60 mph or greater. A Flash Flood Watch means conditions favor flash flooding over large or multiple areas and is usually issued only on an especially active day; an Urban and Small Stream Flood Advisory means minor flooding is expected or under way in low lying and flood prone areas, with extreme caution advised for motorists; a Flash Flood Warning tells people to move to higher ground now (NWS Phoenix). On the wind side, a Severe Thunderstorm Watch signals that widespread storms with damaging winds and even large hail could develop, and a Severe Thunderstorm Warning adds that hail 1 inch in diameter or larger is possible.

When that warning is in effect, NWS Phoenix says to move into a central interior room and stay away from windows, and warns that unanchored mobile homes are not safe in any severe thunderstorm (NWS Phoenix). The office calls the monsoon the most dangerous time of year weather-wise in the Southwest. NWS Phoenix also lists the Dust Storm Warning on the same page; dust storms are covered in the Surprise dust storm safety guide.

NWS Phoenix explains that flash flooding can occur many miles away from a thunderstorm, especially one over mountains, as the runoff flows into the valleys and deserts (NWS Phoenix, Monsoon Safety).

NWS Phoenix adds that although most storms come in the afternoon and evening, some of the region's worst flash floods have happened in the middle of the night, and it advises against camping overnight or parking a vehicle along or near streams and washes during the monsoon (NWS Phoenix). It also warns never to let children play near washes or storm drains after any rainfall, no matter how light, because storm drains are usually large enough to sweep a child away.

The Flood Control District of Maricopa County points out that many parks and recreation areas are also basins or channels, and are dangerous to play in when they are doing their flood control job; it tells residents to stay out of flooded areas and to use the MCDOT road closure map because low water crossings can become uncrossable (Flood Control District of Maricopa County). The City of Surprise adds a driving hazard specific to the first storm of summer: rain lifts oils and other automotive fluids off the pavement and makes roads unusually slick, so the first instruction on its list is to slow down (City of Surprise, Monsoon Safety).

Under the Arizona Stupid Motorist Law, the city warns, a driver who needs rescue from a flooded wash that had posted warning signs or gates may be held responsible for the cost of the water rescue (City of Surprise).

Free sand and bags are set out by the City of Surprise whenever significant rain is in the forecast, at three standing sites and two temporary corners, and residents bring their own shovel (City of Surprise, Monsoon Safety).

The standing sites are the AZ TechCelerator at 12425 W Bell Road, Fire Station 302 at 18600 Reems Road and the water well site at 16849 W Jomax Road; the temporary sites, activated when needed, are the southwest corner of 219th Avenue and Deer Valley Road and the northeast corner of 183rd Avenue and Norwich Drive (City of Surprise). The sites are stocked only when a heavy rain event is forecast, and in the middle of a storm street cleanup comes before restocking. Low stock is reported to the Transportation Hotline, 623.222.6031, or [email protected] (City of Surprise).

Once home with the bags, the county Flood Control District's guidance is bags 1/2 to 2/3 full, stacked in a brick pattern, with the focus on entrance areas of the house such as front doors and low entrances (Flood Control District of Maricopa County). The county district also suggests a family plan and an emergency kit with at least 3 days worth of food and water when preparing for the monsoon (Flood Control District).

Anyone in Surprise who hears thunder should get into a sturdy building or hard-topped vehicle and wait until 30 minutes after the last rumble, because NWS Phoenix says lightning can strike up to 60 miles from the nearest rainfall (NWS Phoenix, Monsoon Safety).

For Surprise yards and patios, the same page lists porches, trees, convertible cars and swimming pools among the places to leave, and advises planning outdoor activity to avoid mid afternoon through mid evening (NWS Phoenix). Indoors, NWS Phoenix says not to touch wires or plumbing, since telephone lines and metal pipes conduct electricity. The City of Surprise gives the same indoor advice in local terms: stay off corded and cordless phones, use a cell phone only if necessary, and stay away from plumbing fixtures because lightning can travel along metal pipes (City of Surprise).

For golfers, the city's list is specific: do not swim or hold metal objects, including golf clubs and lawn chairs, when lightning is near (City of Surprise). If the power goes out, the city suggests keeping freezer and refrigerator doors closed, using surge protectors on electronics, and talking to neighbors and offering help; the city's outage contact list names Arizona Public Service Co. (Electric) at 602-371-7171 (City of Surprise).

Surprise takes part in the National Flood Insurance Program (FEMA NFIP Community Status Book, 040053), and FEMA's FloodSmart site says any homeowner who lives in a participating NFIP community is eligible for a homeowner flood policy (FEMA FloodSmart).

FEMA's community status listing for the City of Surprise, community 040053, shows it participating with a currently effective flood map dated 11/04/15 (FEMA).

The same FEMA record dates Surprise's initial Flood Insurance Rate Map to December 15, 1978 and its initial flood hazard boundary map to June 28, 1974, and its Community Rating System class and premium discount fields are empty as of the record's last refresh on August 25, 2026 (FEMA).

For Surprise owners weighing a policy, FEMA's FloodSmart site says most homeowners and renters insurance does not cover flood damage, and that a new flood policy generally takes effect 30 days after purchase, with exceptions such as buying while making, increasing, extending or renewing a mortgage (FEMA FloodSmart, Buy a Policy). Building policies for homeowners cover up to $250,000, according to the same page.

After a flood, the Flood Control District's recovery steps are calling the insurance company, avoiding additional risk, taking pictures, protecting health and removing the water (Flood Control District).

The Flood Control District of Maricopa County runs a network of automated rain gages that measure the amount and timing of rainfall in real time, and its Rainfall Data page shows real-time and historic data as tables, maps and plots (Flood Control District, Rainfall Data).

The two county pages give different gage counts: the Monsoon page says the district has installed and maintains 355 automated precipitation gages across Maricopa and surrounding counties (Flood Control District, Monsoon), while the Rainfall Data page gives 378 (Flood Control District, Rainfall Data). Both pages say the data are transmitted to the district by radio; neither explains the difference.

On the Rainfall Data page, a report of 6-hour and 24-hour totals at every gage, sorted by jurisdiction, updates every 30 minutes, a second report of 15-minute to 72-hour values updates every 15 minutes, and a daily report covers totals ending at 5 a.m. each day (Flood Control District). County meteorologists also publish a daily weather outlook that residents can read online or receive by email (Flood Control District, Monsoon). The district's main line is 602-506-3011 (Flood Control District).