Phoenix Home Answers

How do I prepare my AC for monsoon season?

Monsoon AC prep in Phoenix comes down to a short list: a clean filter, a clear outdoor unit, a drain line that flows, and a plan for power surges. The City of Phoenix says the monsoon runs from June 15 to September 30, with storms peaking between mid-July and mid-August. Your air conditioner is already working its hardest by then, so the time to prepare is before the first storm rolls in.

What monsoon season does to your AC

A monsoon storm hits an air conditioner several ways at once. Dust storms, or haboobs, can carry winds up to 60 mph and a wall of dust as high as 10,000 feet, according to NOAA, which also notes that one to three large dust storms reach the Phoenix area in a typical year. That dust ends up in your filter and on the outdoor unit’s coil.

Wind throws patio furniture and branches. Lightning and outages bring power surges when electricity comes back on. Heavy rain can flood low spots in the yard where an outdoor unit sits. And the monsoon’s moist air makes your AC’s job of removing humidity more important, which depends on a clear condensate drain.

Monsoon AC prep checklist for Phoenix

This table sorts each monsoon hazard by what it does to an air conditioner and what a homeowner can do about it.

Monsoon hazard Effect on your AC What to do
Dust storms Dust can leave the outdoor coil very dirty, and filters clog faster. Dirty coils reduce the system’s ability to cool. Check the filter after each dust storm; ENERGY STAR recommends inspecting it monthly anyway. Have the coils cleaned during a spring tune-up.
High wind Loose yard items can be blown into or against the outdoor unit. Secure or bring in umbrellas, trampolines, and other items that could blow away. Keep at least 2 feet of clearance around the outdoor unit.
Lightning and outages Surges when power is restored can damage equipment, including HVAC systems. Ask an electrician about surge protection. During an outage, set the thermostat to off along with other appliances to avoid a surge when power comes back on.
Heavy rain and flooding Water can damage electrical parts, and even a small shift in the outdoor unit could breach the refrigerant system. Have roof drains and scuppers cleared before the season; working on a roof in summer heat is dangerous. If the unit sits in water, don’t run it or touch it; have it inspected first.
Humidity A plugged condensate drain can affect indoor humidity levels and cause water damage in the house. Check that the drain line flows before storms start.

The filter matters most. The Department of Energy says filters need more attention in dusty conditions, and replacing a dirty filter can cut an air conditioner’s energy use by 5% to 15%. See how often to change your AC filter in Phoenix for a schedule.

If you use an evaporative cooler, expect it to struggle once the humid air arrives. The Department of Energy says evaporative coolers are only suited to low-humidity areas because they add moisture to the air. See swamp cooler maintenance in Phoenix.

During and after a storm

Stay inside while the storm passes. The National Weather Service’s rule is “When thunder roars, go indoors,” and it advises waiting 30 minutes after the last lightning or thunder before going back out. Indoors, it says to avoid touching anything plugged into an outlet.

If the power goes out, SRP advises turning off lights and appliances to avoid a surge when power returns, and APS suggests unplugging equipment you don’t need for the same reason. Once the storm has passed:

  • If there’s no standing water around the outdoor unit, clear branches and debris away from it.
  • Check the filter and replace it if it’s dusty.
  • Stay at least 100 feet from any downed power line, as APS advises, and call 911.
  • Stay out of standing water; the City of Phoenix warns it may be electrically charged.

When to call a pro

Call a qualified HVAC contractor before running the system if the outdoor unit sat in floodwater, was knocked off its pad, or was hit by debris. ESFI says never to touch electrical equipment that has been submerged and to have anything exposed to water inspected by qualified professionals. AHRI goes further: it says flood-damaged heating and cooling equipment should be replaced, not repaired, so ask the technician how high the water reached before deciding.

A technician should also handle anything past the filter and yard: coil cleaning, refrigerant checks, and electrical connections, all items ENERGY STAR lists for a professional check. Booking that visit in spring, as ENERGY STAR recommends, puts it ahead of the monsoon.

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