A swamp cooler usually isn’t broken when it stops cooling in July. The air is too humid for it to work well. The monsoon raises the moisture in Tucson’s air, and an evaporative cooler needs dry air to cool. Climate Pros Tucson explains how to tell humidity from a real fault, and matches you with a licensed pro when it’s time for refrigerated air.

Why does the cooler fade when the monsoon starts?

An evaporative cooler cools by evaporating water, and air that already holds moisture takes up less. At Tucson’s airport, average dew points sit in the 20s for most of the year and jump into the high 50s in July and August, according to NOAA records. The official monsoon runs June 15 through September 30. A cooler that felt great in May can feel weak and damp by mid-July even when every part works.

What are dew point and wet-bulb in plain English?

Dew point is a measure of how much moisture is in the air. Wet-bulb is the lowest temperature evaporation alone can reach. The higher the dew point, the smaller the gap between outside air and that floor, so the less a cooler can do. You don’t need to calculate anything: if the air feels sticky outdoors, the cooler has less to work with.

Is it humidity or a real fault?

Check for a fault first, because a broken cooler looks the same on a humid day.

  • Pads wet across the whole face, water running, fan spinning: probably humidity.
  • Dry or partly dry pads, no water sound: a water-supply or pump problem. See swamp cooler pump not working.
  • Heavy white scale on pads: Tucson Water says hard water builds calcium deposits in evaporative coolers, and it advises regularly changing the pads and adding an in-line filter.

Does opening a window help?

Yes. A cooler pushes air in, so the house needs a way for it to leave. Open windows a few inches in the rooms you want cooled, so the cool air flows through them on its way out. Without an exit, the air backs up, the house gets muggy and the cooler delivers less.

When should you switch to the AC?

Switch when the house stays uncomfortable with the cooler working and the windows open. If you have both, a common split is the cooler in the dry weeks and refrigerated air once the monsoon sets in. You’ll make that call as the weather turns, not on a calendar date. See swamp cooler vs AC in Tucson and monsoon humidity and your AC for the comparison.

If your house has only a cooler and you’re thinking about ending the summer scramble, replacing a swamp cooler with central air covers what that involves, and AC repair or AC installation are the services involved. The hub at HVAC service in Tucson lists the areas we cover.

Done fighting the humidity?

If you want to talk through refrigerated air or switching, a licensed pro can look at your house. Not every HVAC pro works on evaporative coolers, so ask about that when you call. Call (520) 353-2520 and we’ll match you with a licensed local pro.