Top Tips for Summer Storage: Keep Your Belongings Safe in the Heat

Summer is one of the busiest seasons for self-storage — and one of the riskiest for your belongings. Temperatures inside a non-climate-controlled storage unit can reach 20–30°F above the outdoor temperature on a hot day, meaning a 90°F afternoon can push your unit well past 110°F. At that level, candles melt, vinyl records warp, electronics degrade, and anything with adhesive or composite materials starts to break down.

The good news: a few simple precautions before you store can prevent most heat and humidity damage. Here's exactly what to do.

1. Know What Can't Handle Summer Heat

Before you load the unit, pull these items out of the pile. They're either safety risks or near-guaranteed casualties in a hot storage unit:

Items that melt or warp:

• Candles and wax products
• Vinyl records
• CDs, DVDs, and Blu-rays
• Crayon and art supply collections
• Composite or laminate furniture with heat-sensitive adhesives

Safety hazards in heat:

• Aerosol cans (pressure builds and they can rupture or explode)
• Propane tanks and fuel canisters
• Paint and solvents
• Ammunition

Items that attract pests when warm:

• Food, snacks, and pet food
• Scented candles, potpourri, and air fresheners

If any of these are on your list, find an alternative — a climate-controlled unit, a different location, or leave them at home.

2. Choose Climate-Controlled Storage for Sensitive Items

A climate-controlled unit maintains temperatures between 55–85°F and regulates humidity year-round — regardless of what's happening outside. For summer storage, that consistency is the difference between items coming out in the same condition they went in and coming out damaged.

Worth the upgrade for:

• Wood furniture (warps and cracks in heat and humidity)
• Leather furniture and goods (dries out and cracks, or develops mold)
• Electronics (heat degrades batteries and circuit boards)
• Artwork, photographs, and framed prints
• Documents, books, and records
• Musical instruments
• Clothing stored long-term (heat accelerates fabric breakdown and odor)

Climate-controlled units typically cost 25–50% more than a standard unit — roughly $20–$50 extra per month depending on size and location. For irreplaceable or expensive items, it's almost always worth it.

See which Bolt Storage locations offer climate-controlled units →

3. Switch from Cardboard to Plastic Bins

Cardboard absorbs moisture. In a hot, humid summer unit, cardboard boxes soften, lose structural integrity, and can collapse under the weight of stacked items. Humidity also encourages mold growth inside cardboard boxes even when the items inside seem dry.

Clear plastic bins with tight-fitting lids solve both problems — they're moisture-resistant, stackable, and let you see what's inside without opening every box. If you're storing long-term or through multiple seasons, the investment in plastic bins pays for itself quickly.

4. Prep Appliances and Electronics Before Storing

Heat and residual moisture are the two main threats to appliances and electronics in summer storage. Before anything goes in:

• Clean and dry all appliances thoroughly — any residual moisture causes mold and corrosion
• Leave refrigerator and washing machine doors slightly ajar to prevent mold buildup inside
• Remove all batteries from electronics — heat causes batteries to leak, which can permanently damage devices
• Store cords in labeled zip-lock bags to keep them organized and protect against moisture
• Wrap electronics in moving blankets or anti-static bubble wrap, not plastic sheeting

For valuable electronics — TVs, computers, audio equipment — a climate-controlled unit is strongly recommended for anything stored longer than a few weeks in summer.

5. Use Breathable Covers, Not Plastic Wrap

Plastic sheeting traps heat and moisture against surfaces, which is the opposite of what you want in a summer unit. Plastic wrap on a sofa in a hot unit creates a sealed environment where moisture accumulates — perfect conditions for mold and mildew.

Use instead:

• Moving blankets for sofas, chairs, and wood furniture
• Cotton sheets or fabric furniture covers for dressers and tables
• Breathable fabric mattress bags for mattresses
• Cardboard corner protectors for sharp edges and glass

6. Elevate Everything Off the Floor

Concrete floors in storage units absorb and radiate heat, and condensation from temperature changes settles at floor level. Keeping items elevated creates an air gap that reduces heat transfer and moisture contact.

Use wooden pallets, plastic risers, or shelving units to lift boxes and furniture off the ground. Even a few inches makes a meaningful difference over a long, hot summer.

7. Store Clothing the Right Way

Summer is prime time for storing off-season clothes — winter coats, heavy sweaters, ski gear. Heat and humidity accelerate fabric breakdown and odor if clothing isn't stored correctly.

• Wash and dry all clothing completely before storing — storing clothes with body oils or sweat residue accelerates fabric damage
• Use wardrobe boxes for hanging items to maintain shape and prevent creasing
• Add cedar blocks or moisture absorbers to bins with folded clothing
• Avoid vacuum-seal bags for long-term storage — they compress fibers and can cause permanent creasing in wool and delicate fabrics
• For leather jackets or coats, condition before storing and use a breathable garment bag

8. Create a Labeled Inventory Before You Close the Door

Summer storage is often temporary — a semester break, a seasonal cleanout, a move. The more organized you are going in, the faster and easier the retrieval process is when summer ends.

• Label every bin and box with contents and destination room
• Take a quick video walkthrough of the unit after loading
• Keep a simple inventory list on your phone or in a notes app

Here's how to build a proper storage inventory list.

9. Visit Your Unit During Summer — Don't Just Set and Forget

If you're storing through multiple months of summer, check in periodically. Look for signs of moisture, pests, or anything that seems off. Catching a problem early is far easier than dealing with widespread damage at the end of the season.

Most Bolt Storage facilities offer extended access hours. Some offer 24/7 gate access — check your specific location when reserving.

FAQ: Summer Storage

What temperature does a storage unit reach in summer? In direct sun, non-climate-controlled units can reach 20–30°F above the outdoor temperature. On a 90°F day, that means your unit could hit 110–120°F inside. This is why climate control matters for heat-sensitive items.

Is it safe to store electronics in a non-climate-controlled unit in summer? Short-term (a few days to a week), usually fine. For anything longer, the heat risk to batteries, circuit boards, and screens is real. Climate-controlled storage is strongly recommended for electronics stored through summer.

Can I store wine or candles in a storage unit during summer? Not in a standard unit. Wine is highly sensitive to temperature — heat above 70°F accelerates aging and can permanently damage bottles. Candles will melt. Both need climate-controlled storage or should be kept elsewhere during summer months.

Do plastic bins really make a difference over cardboard? Yes — significantly. Cardboard absorbs moisture, weakens in heat, and can collapse under stacking weight. Plastic bins maintain structural integrity, seal out moisture and pests, and stack more safely.

What's the best way to prevent mold in a summer storage unit? The main causes of mold are moisture and lack of airflow. Store only completely dry items, use breathable covers instead of plastic, elevate items off the floor, use moisture absorbers inside the unit, and choose a climate-controlled unit for anything stored long-term.

How often should I check on my storage unit in summer? At least once a month for long-term summer storage. More frequently if you're in a region with high humidity or if you're storing sensitive items in a standard unit.

Ready to store smarter this summer? Find a Bolt Storage location near you and reserve your unit online in minutes.

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