Fall Equinox Today: Why Your HVAC Works Harder During Seasonal Transitions

At exactly 2:19 PM Eastern Daylight Time today, September 22, 2025, the sun crosses the celestial equator, marking the official start of fall. While you're reading this, Union County and the rest of New Jersey are transitioning from the heat of summer to the cool embrace of autumn—and your HVAC system is about to face its most challenging period of the year.

This week's forecast tells the whole story: temperatures swinging from Monday's comfortable 76°F to Tuesday's surprising 86°F, then dropping to Thursday's 70°F, with rain chances increasing from 40% to 80% by week's end. These dramatic fluctuations aren't just uncomfortable—they're putting your heating and cooling system through a workout that rivals the hottest summer days or coldest winter nights.

The Hidden Science: Why Your HVAC System Struggles During the Equinox

Most homeowners don't realize that their heating and cooling systems work harder during seasonal transitions than during temperature extremes. The shoulder season—that period between summer and winter—creates unique challenges that can increase your energy bills by 15-20% if you're not prepared.

The Temperature Swing Phenomenon

During stable seasons, your HVAC system settles into predictable patterns. In summer, it runs cooling cycles consistently. In winter, it provides steady heat. But during the fall equinox transition, especially this week in Elizabeth and surrounding areas, your system faces a different challenge entirely.

Consider what's happening right now: This morning at 6 AM, temperatures in Union County dipped to 62°F—cool enough that many homes needed heating. By 2 PM, as the equinox arrives, we're hitting 76°F, triggering cooling systems. Tonight, as temperatures drop back to 60°F, heating may kick in again. This constant switching causes:

• Increased wear on system components, particularly the reversing valve in heat pumps
• Higher energy consumption from frequent startup cycles
• Condensation issues as systems switch between modes
• Thermostat confusion leading to inefficient operation
• Stress on electrical components from mode changes

This Week's Weather: A Perfect Storm for HVAC Systems

The National Weather Service forecast for Union County this week demonstrates exactly why the fall equinox period demands special attention for your HVAC maintenance. After an unusually dry August—the 13th driest on record for New Jersey—we're seeing a rapid transition to wetter, more variable conditions.

Tuesday's sudden spike to 86°F—a full 10 degrees above today—exemplifies the challenge. Your system must rapidly adjust from minimal operation to full cooling mode, then back down as temperatures moderate by Thursday. For commercial HVAC systems in office buildings and retail spaces, this variability is even more pronounced due to occupancy changes and heat generation from equipment.

Smart Energy Strategies for the Shoulder Season

The fall equinox presents a unique opportunity to reduce energy costs while maintaining comfort. With outdoor temperatures frequently falling within the comfort zone of 65-75°F, smart homeowners can leverage natural ventilation and strategic thermostat management to minimize HVAC runtime.

The Free Cooling Advantage

Today's weather—with a high of 76°F and low of 60°F—is perfect for what HVAC professionals call "free cooling." Instead of running your air conditioner, open windows during the comfortable morning and evening hours. This natural ventilation can reduce your cooling costs by 30-50% during September and October.

Here's your hour-by-hour strategy for maximizing free cooling this week:

• 6 AM - 9 AM: Open windows when outdoor temperature is 60-68°F
• 9 AM - 11 AM: Monitor indoor temperature; close windows if it exceeds 72°F
• 11 AM - 6 PM: Keep windows closed; use HVAC if needed
• 6 PM - 10 PM: Reopen windows as temperatures drop below 70°F
• 10 PM - 6 AM: Maintain slight opening for overnight cooling

Your Fall Equinox HVAC Maintenance Checklist

The fall equinox serves as nature's reminder that heating season is approaching. With the first frost typically arriving in Union County by late October—just five weeks away—now is the critical window for preparing your system. Waiting until the first cold snap often means competing with your neighbors for emergency service appointments.

Essential DIY Tasks (Complete This Week)

1. Replace Air Filters: After the dry August (13th driest on record), filters are likely clogged with dust and debris. Install MERV 8-11 filters for optimal balance between filtration and airflow.
2. Test Heating Mode: Today, while it's still mild, run your heating system for 15-20 minutes. Listen for unusual noises, check for odd smells, and verify warm air is flowing from all vents.
3. Clear Outdoor Units: Remove summer growth—leaves, grass, and debris—from around your outdoor condenser. Maintain at least 2 feet of clearance on all sides.
4. Check and Seal Ductwork: With temperature swings ahead, sealed ducts prevent energy loss. Use mastic sealant or metal tape (never duct tape) on visible joints.
5. Program Your Thermostat: Update settings for fall schedule. Set to 68-70°F when home, 62-65°F when away, and enable "Auto" mode for automatic switching.
6. Test Carbon Monoxide Detectors: With heating season approaching, ensure all CO detectors have fresh batteries and test properly.

Professional Services to Schedule Now

While DIY maintenance helps, professional service ensures your system handles the upcoming temperature swings efficiently. Boiler systems especially need annual professional inspection before heating season begins.

• Comprehensive 21-point heating system inspection
• Combustion analysis and efficiency testing
• Heat exchanger inspection for cracks or corrosion
• Blower motor lubrication and belt tension adjustment
• Electrical connection tightening and voltage checks
• Condensate drain cleaning and treatment
• Safety control verification and calibration

Preparing Your Specific HVAC Brand for Fall

Different HVAC brands have unique requirements for seasonal transitions. Understanding your system's specific needs ensures optimal performance during the challenging equinox period.

Heat Pump Considerations

Heat pumps face particular challenges during the fall equinox due to frequent mode switching. The reversing valve—the component that changes your system from heating to cooling—experiences maximum stress during shoulder seasons. If you have a Carrier, Trane, or Lennox heat pump, pay special attention to:

• Unusual clicking or whooshing sounds during mode changes
• Delayed response when switching between heating and cooling
• Ice formation on outdoor coils during mild weather
• Auxiliary heat engaging prematurely (below 40°F)

For Rheem and Goodman systems, which are popular in Summit and Westfield homes, focus on defrost cycle operation. The varying humidity levels this week (increasing from 65% to 85% with incoming rain) can trigger unnecessary defrost cycles, wasting energy and reducing comfort.

Managing Humidity: The Overlooked Equinox Challenge

The transition from New Jersey's dry August to the incoming wet pattern creates humidity management challenges that affect both comfort and system efficiency. This week's forecast shows rain chances increasing from 0% today to 70% Tuesday, dramatically altering indoor humidity levels.

Why Humidity Matters More During Transitions

When outdoor temperatures hover in the 70s with high humidity, your home can feel uncomfortable even at reasonable temperatures. This phenomenon, known as the "comfort index," explains why 72°F can feel perfect one day and sticky the next. During the fall equinox transition:

• Morning dew points rise rapidly, creating condensation on windows
• Afternoon humidity drops cause static electricity and dry skin
• Evening moisture returns, triggering mold and mildew growth
• Basement humidity levels fluctuate wildly, stressing dehumidifiers

Regional Variations: How Union County's Geography Affects Your HVAC

Union County's diverse geography—from the Elizabeth waterfront to the Watchung Mountains—creates microclimates that affect how your HVAC system responds to the fall equinox. Understanding your specific area's challenges helps optimize system performance.

Elevation and Temperature Variations

Homes in Berkeley Heights and mountainside communities experience temperatures 3-5 degrees cooler than Elizabeth or Linden. This means:

• Earlier transition to heating mode (often by mid-September)
• More dramatic day-night temperature swings
• Increased risk of frozen condensate lines in October
• Higher heating bills due to wind exposure

Conversely, urban areas like Union City experience the heat island effect, staying 5-7 degrees warmer at night. These homes may need cooling well into October, making efficient transitions even more critical for energy savings.

Preparing for Fall Weather Emergencies

The equinox marks the beginning of potentially severe weather season in New Jersey. With hurricane season peaking through October and nor'easters possible by November, ensuring your HVAC system can handle emergencies is crucial.

Power Outage Preparedness

This week's rain forecast—with 70% chance Tuesday and potential thunderstorms—reminds us that power outages become more common during seasonal transitions. To protect your HVAC system:

• Install a whole-house surge protector to prevent damage from power fluctuations
• Consider a generator connection for critical heating during outages
• Know how to manually reset your system after power restoration
• Keep Dimatic Control's 24/7 emergency service number handy: (908) 249-9701

Smart Investments: Upgrades That Pay for Themselves

The fall equinox is an ideal time to evaluate system upgrades that can reduce the stress of seasonal transitions. With federal tax credits available through 2032 and utility rebates at seasonal highs, investing now provides maximum return.

Priority Upgrades for Shoulder Season Efficiency

1. Smart Thermostats ($200-$400): Automatically adjust for temperature swings, learning your patterns to optimize comfort while reducing energy use by 20-30%. Pay for themselves in 6-12 months.
2. Variable-Speed Blowers ($800-$1,500): Adjust airflow based on demand, reducing energy consumption during mild weather by up to 40%. Essential for managing shoulder season variations.
3. Zoning Systems ($2,000-$4,000): Heat or cool only occupied areas, particularly valuable during transitions when different rooms need different conditioning.
4. High-Efficiency Filters with UV Lights ($500-$1,000): Improve air quality while preventing mold growth during humid transitions. Especially important after our dry August.

The Next 30 Days: Your Fall HVAC Timeline

As we transition from the equinox through October, your HVAC needs will evolve rapidly. Here's what to expect and when to take action:

Week-by-Week Fall Preparation Schedule

Frequently Asked Questions About Fall HVAC Preparation

Take Action Today: Your HVAC System Needs You

As the sun crosses the celestial equator at 2:19 PM today, marking the official start of fall, your HVAC system enters its most challenging period. The temperature swings ahead—from today's 76°F to Tuesday's 86°F, then down to Thursday's 70°F—will test every component of your heating and cooling system.

The good news? With proper preparation and maintenance, your system can handle these transitions efficiently, keeping your family comfortable while minimizing energy costs. The key is taking action now, during this mild weather window, rather than waiting for the first cold snap when everyone needs service simultaneously.

Remember, the fall equinox isn't just an astronomical event—it's your HVAC system's warning bell. The dramatic temperature swings, humidity changes, and approaching heating season all converge to create unique challenges that require attention now. Whether you tackle DIY maintenance today or schedule professional service this week, taking action during the equinox transition period ensures comfort, efficiency, and reliability through fall and winter.

Happy Fall Equinox from your neighbors at Dimatic Control! We've been keeping Union County comfortable through seasonal transitions since our founding, and we're here to help you navigate this challenging but beautiful time of year. When your HVAC system needs professional attention, remember that we're just a phone call away at (908) 249-9701.