What the Phoenix climate asks of a new resident

Moving to the low desert is usually described as an adjustment to the heat. In practice the heat is the least surprising part. What catches people out is that the Phoenix climate is not one problem with a season attached, but five separate demands on a household, each with its own timing, and the timing is what makes them either cheap or expensive to meet.

This page is a guide rather than an account of anyone’s move. Every figure in it is a climate normal (the 1991–2020 average at Phoenix Sky Harbor, station USW00023183) which describes a typical year rather than predicting the next one.

What the heat asks

The heat asks for a schedule rather than endurance.

The normal high is at or above 100 °F for 111 days a year, running from 31 May to 18 September, and at or above 105 °F for 66 days in the middle of that. The low matters more than the high: there are 84 nights a year at or above 80 °F, from 20 June to 11 September, and 141 nights at or above 70 °F, from 18 May to 5 October. A house that never cools overnight is a different building to live in, and the hours that are actually workable outdoors narrow to the early morning through the middle of the year.

What that asks of a household is unglamorous. Errands move earlier. Yard work stops for the summer. Exercise moves indoors or to before sunrise. The Heat-Safe Hours Planner takes a month and an activity and reports which hours sit under the limit for that activity, which is a faster way to build the habit than learning it the hard way.

What the monsoon asks

The monsoon is the second demand, and it is the one newcomers underestimate because the first summer can pass with very little rain in it.

The National Weather Service gives the season fixed dates (15 June to 30 September, 108 days) so that forecasts and warnings share a calendar. Within that window, July and August between them carry about a quarter of the year’s 7.22 inches of rain, arriving mostly in a handful of storms rather than spread evenly. The season brings flash flooding in the washes, blowing dust, and wind that takes down trees and puts debris into power lines.

The preparation is modest and front-loaded. The Monsoon Prep Checklist Builder assembles a list for a specific home, vehicle and pets, and the pre-season work is the sort that costs an afternoon in May and saves a week in July: roof drains and scuppers cleared, trees thinned, anything loose on the patio secured before it becomes airborne.

One item on that list has a deadline rather than a season. Flood insurance under the National Flood Insurance Program has a thirty-day waiting period, so a policy bought in the week a storm is forecast does not cover that storm. Maricopa County adds the reason to look at it even outside a mapped floodplain: one in four flood insurance claims in the county comes from outside one.

What the cooling system asks

The cooling system is the household’s one genuine dependency, and it is the thing to sort out first.

Air conditioning here runs harder for longer than in almost any other American city, because the nights do not relieve it. A sensible first task after arriving is a service visit booked in spring, before the first 100 °F afternoon rather than during it: the same appointment is routine in March and an emergency in July. The Home Cooling Task Scheduler turns that into a dated list of filter, coil, pad and service tasks for the equipment a specific house actually has.

The related habit is knowing what the house does when the power goes. Monsoon winds cause outages, and the households that cope are the ones that already know how to open an automatic garage door by hand and which appliances to switch off before power returns.

What the water asks

Water is the part of the bill a household can actually move.

Arizona’s water law is mostly about basins and subdivisions rather than gardens, and the rules that reach a yard (watering days, any drought stage in force, any landscape conditions attached to the land) come from the water provider and the city rather than from the state. That is worth knowing before assuming a rule you have heard about applies to your address, and What Arizona water law means for a yard sets out the framework on its own page.

What the climate asks is simpler than the law. Outdoor water is the portion of residential use with the most room in it, and the cheapest way to reduce it is to group plants by how much water they need rather than scattering thirsty species through a dry yard. The Hydrozone Yard Planner does that grouping, and the Desert Plant Picker is the place to check what a species will actually need before buying it.

What the winter asks

The winter asks for almost nothing, which is exactly why it gets forgotten.

The normals give 0.6 nights a year below freezing at Sky Harbor (0.4 of them in January, 0.1 in December and 0.1 in February) and 6.8 nights below 40 °F in December, 4.7 in January and 1.7 in February. A normal year does not freeze. The record back to 1933 shows that individual winters do, and that is the distinction that matters for anyone arriving with citrus, a tender shrub, or pipes on an exterior wall. The Frost & Freeze Date Explorer works from the record rather than the average, which is the honest way to plan for a once-a-decade night.

The checklist

What none of this asks

It is worth ending on what the climate does not require, because the list above can read as more work than it is.

It does not ask for a different routine so much as a shifted one. It does not ask for desert landscaping in the sense of gravel and nothing else; it asks for plants matched to the water that is actually available. It does not ask a household to think about water rights, which sit with providers and subdivisions rather than with a garden hose. And it does not ask for anything at all in five months of the year, when the normal high sits between the mid-sixties and the high seventies and the outside is simply where people are.

If you want the year laid out month by month rather than by demand, The low desert year is the companion page. If what you need is to be able to read the forecast a local would read, Reading a Valley forecast takes the products and the numbers one at a time.