Preparing a house for monsoon

Most of what a house needs before a monsoon is work that cannot be done in the rain. Clearing a roof drain is a job for dry weather. Thinning a tree is a job for dry weather. Re-grading a yard is a job for dry weather. The season gives you a fixed date to work backwards from (it opens on 15 June) and the Monsoon Season Clock will tell you how far away that is.

The official guidance is written in four moments, and it is worth keeping them separate: before the season, when a storm is in the forecast, during it, and after it. Mingling them produces the genre of list that puts “buy flood insurance” next to “get out of the wash”, which is a list somebody ends up reading while the water is rising.

The work that needs dry weather

The City of Phoenix’s own pre-season list is short and almost entirely about moving water where you want it. Clear the roof drains and scuppers so rain cannot pond on a flat or low-slope roof. Clear the drywells on the property, because one that has silted up holds almost nothing and sends the water it should have taken somewhere else. Re-grade the landscaping so water runs away from the building rather than toward the slab. Thin the trees and cut back overgrowth.

Two of those deserve a note. The first is that a drywell and a roof drain are the same problem in two places: both are designed capacity that quietly fills with silt over years, and neither announces that it has stopped working. The second is the word thin. Thinning a canopy lets wind through it; leaving it dense turns the whole tree into a lever with the trunk as the fulcrum, which is why the roof article in this series treats tree work as roof work: see Monsoon and your roof.

Then there is the equipment that has nothing to do with rain. A monsoon outage in July takes the air conditioning with it, and the utility guidance is to switch the air conditioner and the major appliances off while the power is out so that nothing is running when it comes back. That is the same maintenance calendar that carries a Phoenix summer, which is what the Home Cooling Task Scheduler is for. Backing up data belongs on the same list; the city names it, which is a reminder that water and electronics are the pairing that costs the most to replace.

The one deadline that cannot move

Flood insurance is the only item on any of these lists that cannot be done at the last minute. A new policy has a thirty-day waiting period before it takes effect, and Maricopa County states the consequence in as many words: when a storm is in the forecast, it is too late to get a flood policy.

Thirty days back from 15 June is 16 May. The waiting period is FEMA’s and the subtraction is this site’s, but the arithmetic is the easy part; the harder part is that 16 May is not a date anybody associates with storms. The county’s other useful figure is that one in four flood insurance claims comes from outside a mapped floodplain, which is its way of saying that a house’s position on a map is not the same thing as its risk.

24 to 48 hours out

This is the last chance to move things, and nothing on the list takes more than an hour.

Bring in the outdoor furniture: the patio chairs go into the garage, not against a wall. Secure anything that could reach a power line, which the utility names specifically as umbrellas, kiddie pools and even trampolines, because they get swept up and end up in the lines; a storm on one street becomes an outage on another. Charge the phones, the power banks and a radio. Decide where the pets will be, because a frightened animal is not going to be caught once it starts. Move what matters to a higher floor. Change any plan that involves a wash or a stream, which the Phoenix forecast office gives as guidance for campers and covers people who never see the rain that floods their site.

The one item that takes real effort is sandbagging, and the county publishes how: fill each bag half to two-thirds full, no more, because a bag packed solid will not settle against the one below it; stack them in a brick pattern; and put them where water actually arrives (the front door and any low entrance) rather than evenly around the house. The city also hands out reusable barriers that open on contact with water and divert flow the way bags do, and during a forecast flood it opens sand sites at city parks, where residents bring their own bags and shovels.

During the storm, the list is things not to do

Nothing in the during-the-storm guidance is a task. Do not drive into a flooded roadway. Do not go around a barricade: a barricade is placed at one specific crossing because that crossing is the problem, and Arizona law attaches liability to the driver who goes past one. Keep children and pets away from washes and storm drains after any rainfall, not only during it. Get out of the pool and stay out, because a pool is the tallest thing in most back yards.

Two more are worth memorising because they are counter-intuitive. In a dust storm the instruction is to turn off every light you have, including the hazards, and the reason is that a driver coming up behind you in zero visibility steers toward the only thing they can see: see What a haboob is and what to do. And after the lightning, the all-clear is thirty minutes after the last rumble of thunder, not after the rain stops.

After the storm, the order is the advice

The county gives five steps in a fixed order: call your insurance company, avoid further danger, photograph the damage, safeguard your health, then remove the water. The order is the point. A claim is easier to make before the evidence is carried out to the kerb.

Around those five, the smaller jobs: wear gloves and boots rather than wading into floodwater, which carries silt, sewage and sharp debris; do not touch electrical equipment that is wet or that you are standing in water to reach; run any generator outdoors and away from windows; and watch the clock on the refrigerator, which holds its temperature for about four hours, and a full freezer for about forty-eight. Anything that needed refrigeration and did not get it is a decision for a pharmacist rather than a label.

Then the mosquitoes, which is a weekly job rather than a one-off: repair torn screens before the season so they have one fewer way in, and afterwards tip and toss even the smallest amounts of standing water out of pots, bird baths, buckets and fountains. The county treats that as part of monsoon work, and the season’s rain is exactly why.

The claims with no official source

A monsoon list circulates every spring that is longer than any agency’s, and four of its items have no official source this site could open. Filling the bathtub before a storm is not on any Arizona or federal list; the closest official instruction is to store clean water in jugs, which a bathtub is not. Taping windows does no good here, and the federal thunderstorm guidance points the other way: shelter away from windows rather than reinforce them. Opening the windows to equalise the pressure comes from tornado advice, not from storms that break glass with debris and wind. And lowering the pool or switching the pump off has no Arizona source either; the only official pool guidance this site could open concerns where drained pool water may go, which is the sanitary sewer and never a storm drain.

If you want the lists without the folklore, the Monsoon Prep Checklist Builder prints the sourced version for your home, car and pets and keeps the unsourced claims in their own block so you can see which is which.