May is one of the best times of the year to check your air conditioner — before the first major heat wave arrives and before your cooling system has to work harder every day.
Once hot weather settles in, small AC issues can quickly turn into uncomfortable days, higher energy bills, or unexpected breakdowns. A weak airflow problem, dirty filter, blocked outdoor unit, or thermostat issue may not seem serious in mild spring weather, but it can become much more noticeable when temperatures rise.
According to Environment and Climate Change Canada’s 2026 temperature outlook, 2026 is expected to continue the recent trend of unusually warm years, with a greater than 99% chance of being hotter than every year on record before 2023. That makes early cooling system preparation even more important for homeowners.
Before the first heat wave, here are seven practical AC checks every homeowner should do in May.
1. Test Your AC Before You Really Need It
Do not wait until the first extremely hot day to turn on your air conditioner for the first time.
Choose a mild day in May and run your AC for at least 15 to 20 minutes. Set the thermostat a few degrees lower than the current indoor temperature and listen carefully while the system starts.
Pay attention to:
- Whether cool air comes from the vents
- How long it takes for the system to start cooling
- Any unusual noises
- Weak airflow from certain rooms
- Strange smells when the system turns on
- Whether the outdoor unit starts properly
If the AC turns on but does not cool well, or if it keeps running without lowering the temperature, it may need professional inspection before summer demand increases.
2. Replace or Check Your Air Filter
A dirty air filter is one of the simplest problems to fix, but it can have a big impact on comfort and efficiency.
When the filter is clogged, your AC has to work harder to move air through the system. This can reduce airflow, increase energy use, and put extra strain on your equipment.
In May, check your HVAC filter and replace it if it looks dusty, grey, or blocked. Homeowners with pets, allergies, renovations, or heavy system use may need to replace filters more often.
A clean filter can help improve:
- Airflow
- Indoor air quality
- Cooling performance
- System efficiency
- Overall comfort
If you replace the filter and still notice weak airflow, the issue may be deeper in the system and should be checked by an HVAC technician.
3. Clear the Area Around the Outdoor Unit
Your outdoor AC unit needs open space to release heat properly. During spring, leaves, grass, branches, dirt, and debris can collect around the unit and reduce airflow.
Walk outside and inspect the area around your condenser. Make sure there is clear space around the unit and gently remove visible debris from the surrounding area.
You should also check for:
- Tall grass growing too close to the unit
- Leaves or branches blocking airflow
- Dirt buildup around the base
- Objects stored too close to the condenser
- Bent or blocked exterior fins
Avoid using sharp tools or high-pressure water on the unit. If the coil looks very dirty or damaged, it is better to have it cleaned professionally during an AC tune-up visit.
4. Check the Thermostat Settings
Sometimes the issue is not the AC unit itself — it is the thermostat.
Before summer, make sure your thermostat is set correctly. Switch it to cooling mode, set the fan to “Auto,” and choose a comfortable temperature. If you have a programmable or smart thermostat, review the schedule to make sure it matches your current routine.
A thermostat problem may be possible if:
- The AC does not turn on when it should
- The indoor temperature does not match the thermostat reading
- The system turns on and off too often
- Some rooms feel much warmer than others
- The schedule is outdated or incorrect
If your thermostat uses batteries, May is also a good time to replace them.
5. Listen for Unusual AC Noises
Your AC should not make loud banging, grinding, buzzing, rattling, or screeching sounds. Some sound is normal when the system starts, but unusual noises can be an early warning sign.
Different noises can point to different problems:
- Rattling may suggest loose parts or debris
- Buzzing may indicate an electrical issue
- Grinding may suggest a motor or mechanical problem
- Screeching may point to belt or motor issues
- Clicking that continues may indicate a control problem
If you hear a strange sound, do not ignore it. A small repair in May may help prevent a larger breakdown during a heat wave.
6. Check Airflow in Different Rooms
Walk through your home while the AC is running and check the airflow from each vent.
Some rooms may naturally feel warmer because of sun exposure, insulation, or layout. However, if one area has very weak airflow or no airflow at all, there may be an issue with the ductwork, dampers, filter, blower, or vents.
Before calling for service, make sure:
- Vents are open
- Furniture is not blocking registers
- Rugs or curtains are not covering vents
- The air filter is clean
- Interior doors are not restricting airflow too much
If airflow still feels uneven, a professional inspection can help identify whether the issue is related to the AC system, ducts, or overall airflow balance.
7. Schedule Preventive AC Maintenance Before Peak Summer
The best time to schedule AC maintenance is before the system is under heavy summer demand.
A professional tune-up can help identify small issues early, clean key components, check system performance, and make sure your cooling equipment is ready for hotter weather.
A typical AC maintenance visit may include checking:
- Thermostat operation
- Electrical components
- Refrigerant-related performance indicators
- Condenser condition
- Airflow
- Drain line function
- System startup and shutdown
- Overall cooling performance
Preventive maintenance is especially important if your AC is older, has not been serviced recently, made strange noises last summer, or struggled to keep your home comfortable.
For homeowners who want peace of mind before the first heat wave, Don’s Heating and Cooling provides professional AC maintenance to help prepare your cooling system for summer.
Why May Is the Right Time to Prepare Your AC
May is a smart time to check your cooling system because HVAC companies often become much busier once the first heat wave arrives.
During extreme heat, many homeowners turn on their AC for the first time and discover problems at the same time. This can lead to higher demand for service appointments and more urgent repair calls.
By checking your system early, you may be able to:
- Avoid uncomfortable indoor temperatures
- Reduce the risk of emergency breakdowns
- Improve cooling performance
- Catch small problems before they become bigger
- Prepare your home before peak summer demand
- Feel more confident when hot weather arrives
Early preparation is not just about comfort. It can also help protect your equipment and reduce stress when temperatures rise.
When Should You Call an HVAC Technician?
Some AC checks are simple for homeowners to do on their own. However, you should contact a professional if you notice:
- The AC is running but not cooling
- Warm air is coming from the vents
- Airflow is very weak
- The system turns on and off repeatedly
- The outdoor unit does not start
- You hear unusual noises
- You notice burning or electrical smells
- Water is leaking around the indoor unit
- Your energy bill suddenly increases
- The system cannot keep up on warmer days
If the problem is urgent, Don’s Heating and Cooling also offers 24/7 service and emergency AC repair to help restore comfort when your cooling system breaks down.
Get Your AC Ready Before the First Heat Wave
A few simple checks in May can make a big difference before summer heat arrives. Testing your AC, replacing the filter, clearing the outdoor unit, checking airflow, and scheduling preventive maintenance can help reduce the risk of unexpected cooling problems.
If you want your system inspected before peak summer demand, contact Don’s Heating and Cooling for professional AC tune-up in Orangeville, Alliston, and nearby areas. We offer free estimates, 24/7 emergency AC repair, and a satisfaction guarantee for homeowners who want reliable comfort when it matters most.
Call Don’s Heating and Cooling today to schedule your AC maintenance before the first heat wave.