The shift from heating season to cooling season is one of the most overlooked maintenance windows of the year. Get it right and your AC runs efficiently all summer. Skip it and you’re looking at higher energy bills, unexpected breakdowns, and a sweltering house on the first truly hot day.
Here’s how to handle the spring HVAC transition properly — and when to do it based on where you live.
Why the Transition Matters
Your HVAC system has been running in heating mode for months. Dust has accumulated on components that haven’t been active since last fall. Refrigerant lines, condensate drains, and outdoor units have been sitting idle through winter weather. Flipping the switch to “cool” without preparation is like starting a car that’s been parked for six months without checking the oil.
A proper transition extends the life of your system, catches small problems before they become expensive repairs, and ensures you’re not wasting energy when temperatures climb.
When to Make the Switch by Region
Timing varies significantly depending on your climate zone. Here’s a practical breakdown:
Southern States (Zones 1–3: Florida, Texas, Gulf Coast, Desert Southwest)
Transition window: Late February to mid-March
In many southern regions, you may have already needed AC a few times this winter. The formal transition should happen by early March at the latest. Some homes in South Florida and the Rio Grande Valley barely use heat at all, but the maintenance steps still apply.
Mid-South and Southeast (Zones 3–4: Carolinas, Tennessee, Georgia, Arkansas)
Transition window: Mid-March to early April
These regions often experience a “shoulder season” where you might need heat in the morning and AC in the afternoon. If your system has a heat pump, it handles this naturally. For conventional systems, plan your maintenance for mid-March.
Midwest and Mid-Atlantic (Zones 4–5: Missouri, Ohio, Virginia, Kansas)
Transition window: Late March to mid-April
Don’t rush it. Late cold snaps are common through mid-April in the Midwest. Schedule your AC prep for late March, but keep the heating system ready until you’re confident overnight lows are consistently above 50°F.
Northern States and Mountain West (Zones 5–7: Minnesota, Montana, New England, Colorado)
Transition window: Late April to mid-May
Patience is key. Snow in April isn’t unusual in these regions, and heating season can extend well into May at higher elevations. Plan your AC maintenance for late April and don’t fully commit to cooling mode until nighttime temperatures are reliably above 55°F.
Step-by-Step Transition Checklist
Follow these steps in order for a smooth switch from heating to cooling.
Step 1: Replace Your Air Filter
This is the single most impactful thing you can do. A clogged filter from heating season forces your system to work harder, reduces airflow, and degrades indoor air quality. Replace it now, even if you changed it recently.
For most homes, a MERV 8–11 filter strikes the right balance between filtration and airflow. If anyone in the household has allergies, consider stepping up to MERV 13.
Step 2: Inspect and Clean the Outdoor Unit
Your condenser unit has been sitting outside all winter. Walk out and check for:
- Debris accumulation — leaves, branches, mulch, or trash pressed against the fins
- Vegetation encroachment — trim any plants or shrubs back to at least 2 feet of clearance on all sides
- Physical damage — bent fins, loose panels, or critter damage (rodents love to nest in outdoor units during winter)
Gently rinse the condenser coils with a garden hose from the inside out. Don’t use a pressure washer — it will bend the delicate fins and reduce efficiency.
Step 3: Check the Condensate Drain
The condensate drain line removes moisture that your AC pulls from indoor air. If it’s clogged, water backs up and can cause water damage or trigger a system shutdown.
Locate the drain line (usually a PVC pipe near the indoor unit) and pour a cup of white vinegar or diluted bleach through it to clear any algae or buildup. Make sure water flows freely out the other end.
Step 4: Test the System Before You Need It
On a day when outdoor temperatures are above 60°F, switch your thermostat to cooling mode and set it a few degrees below the current indoor temperature. Let the system run for 15–20 minutes and check for:
- Cool air coming from all vents
- No unusual noises (grinding, squealing, or clicking)
- No strange smells (a brief musty smell is normal on first startup, but burning smells are not)
- The outdoor unit fan spinning smoothly
If anything seems off, schedule a professional inspection before the summer rush. HVAC technicians are far easier to book in March than in July.
Step 5: Inspect Your Ductwork
While your system is running, walk through your home and check each vent. Feel for airflow and listen for whistling or hissing that could indicate leaks. If you have accessible ductwork in a basement or attic, look for obvious gaps, disconnected sections, or damaged insulation.
Leaky ducts can waste 20–30% of your conditioned air, according to the Department of Energy. Sealing them with mastic or metal-backed tape (not standard duct tape) is one of the best efficiency upgrades you can make.
Step 6: Program Your Thermostat for Spring
Spring weather is unpredictable, so your thermostat settings should accommodate swings. If you have a programmable or smart thermostat:
- Set a wider comfort range (68–76°F) to avoid constant cycling between heat and AC
- Enable “auto” mode if your system supports it, allowing the thermostat to choose heating or cooling as needed
- Adjust schedules for longer daylight hours — you may need less heating in the evening than during winter
Step 7: Schedule Professional Maintenance
An annual professional tune-up in spring catches issues you can’t see: low refrigerant levels, worn capacitors, electrical connection problems, and efficiency measurements. Most HVAC companies offer spring maintenance specials.
Budget $75–$150 for a standard tune-up. It’s cheap insurance against a $5,000+ emergency replacement in August.
Common Mistakes to Avoid
Running AC when it’s too cold outside. Most air conditioners shouldn’t operate when outdoor temps are below 60°F. The refrigerant doesn’t function properly in cold conditions and you risk damaging the compressor.
Ignoring the heat pump defrost cycle. If you have a heat pump, you may notice it switching between modes during spring. This is normal — heat pumps reverse their cycle to defrost the outdoor coil. Don’t override this process.
Closing vents in unused rooms. This increases pressure in the duct system and can cause leaks or reduce efficiency. Leave vents open throughout the house.
Skipping the outdoor unit inspection. Winter is hard on condenser units. Five minutes of inspection and cleaning prevents expensive repairs later.
Related Reading
- HVAC Seasonal Maintenance by Climate
- Energy Efficiency Tips by Region
- Spring Home Maintenance Checklist
- Appliance Maintenance Schedule
Keep Your Yard Ready for Spring Too
While you’re prepping your home systems for warmer weather, don’t forget about your outdoor spaces. The team at Harvest Home Guides has excellent region-specific guides for getting your garden started this spring — including planting calendars tailored to your exact climate zone.