Canada puts contact lens wearers through a lot. Winters drop well below freezing, summers bring humidity and UV exposure, and the shift between seasons can happen within days. Knowing how each season affects your lenses can save your eyes a great deal of grief.
Can Heat and Cold Actually Damage Your Lenses?
Two of the most common questions contact lens wearers have are whether their lenses can freeze in winter or melt in summer heat. Neither happens while you are wearing them.
Your cornea stays at around 34 to 35 degrees Celsius regardless of outside air temperature. That warmth keeps your lenses from freezing even when temperatures dip to -30°C. Your lenses will not melt on your eyes, in your car, or sitting on a hot porch in July.
Stored lenses are different. Contacts kept in solution can freeze when temperatures drop to around -15°C. If that happens to a delivery left outside, let them thaw at room temperature. Do not use hot water or place them near a heat source. Once thawed, inspect the lenses and discard the old solution. If anything looks off, throw them out.
A 2019 CooperVision study tested lenses at temperature extremes for 72 hours and confirmed they maintained approved parameters, including base curve, diameter, water content, and power, as long as the packaging stayed intact.
Hot vs. Cold Weather and What Changes for Contact Lens Wearers
Both seasons create different challenges for your eyes and lenses. Here is a quick side-by-side look.
| Condition | Hot Weather | Cold Weather |
|---|---|---|
| Main Risk | Water exposure and infection | Dry eyes and tear evaporation |
| Effect on Lenses | Sweat and water can contaminate lenses | Lenses may feel stiff or dry due to low humidity |
| Eye Concern | Acanthamoeba keratitis from pool or tap water | Dry, gritty eyes from cold air and indoor heating |
| UV Exposure | Higher risk outdoors in summer | Still present, especially with snow glare |
| What Helps | Goggles when swimming, rewetting drops, UV sunglasses | Lubricating drops, humidifier, redirect heat vents |
Wearing Contact Lenses in Hot Weather
Canadian summers bring more UV exposure, humidity, and outdoor activity, all of which affect your lenses.
Stay out of the water. Remove your contacts before swimming in a pool, lake, or hot tub. Even fresh water can carry microorganisms that cling to contact lens surfaces. One serious risk is acanthamoeba keratitis, a rare but severe eye infection that can cause permanent vision damage if left untreated. If you must swim with contacts, wear tight-fitting goggles.
Watch out for sweat. Sweat trapped between the lens and cornea can cause irritation, redness, and in some cases, infection. Keep rewetting drops nearby during outdoor activity and wash your hands before touching your eyes.
Protect against UV. UV rays reflect off water, concrete, and sand, making summer exposure higher than most people realise. Sunglasses with UV protection are the strongest barrier. Some contact lenses also come with UV-blocking properties, though they do not cover the full eye the way sunglasses do.
The Indoor-Outdoor Temperature Shift and What It Does to Your Lenses
This is a challenge that is specific to Canadian winters. When you walk from -20°C outside into a heated building, the rapid shift in temperature and humidity hits your tear film hard. Cold outdoor air is dry. Heated indoor air is even drier. Moving between the two multiple times a day speeds up tear evaporation, leaving your lenses feeling uncomfortable well before the day is over.
Forced-air heating systems, common in Canadian homes and offices, pull moisture out of the air and make this worse. The result is lenses that feel gritty or tight on the eye, even if your eyes felt fine first thing in the morning.
Blinking consciously when you come indoors gives your tear film a chance to resettle. Preservative-free lubricating drops used at the start and end of each outing reduce the drying effect of repeated temperature changes. A humidifier at home makes a noticeable difference during the months when the furnace runs constantly.
Wearing Contact Lenses in Cold Weather
Wind dries out your eyes fast. Prairie provinces and coastal areas can see wind chills that strip moisture from your eyes within minutes. Wraparound sunglasses or ski goggles act as a barrier that contacts simply cannot. On very windy days, glasses are the better call.
Skip contacts when you are sick. Cold and flu season falls during the months when your eyes are already under stress. If your eyes are puffy, red, or irritated, wait until symptoms clear before putting lenses back in.
How To Keep Your Contacts Comfortable All Year
These habits go a long way regardless of the season.
- Clean and store your lenses properly every day. Follow the replacement schedule on your prescription.
- Switch to daily disposables if your current lenses feel uncomfortable during seasonal changes. They start fresh each day and reduce buildup and irritation.
- Wear glasses for a few hours in the evening to let your eyes breathe.
- Avoid sleeping in your contacts unless your prescription allows it.
If symptoms persist, see your optometrist. Persistent dryness, redness, or blurred vision can point to fitting issues or an underlying condition that drops and lens swaps will not fix.
References
CooperVision. Impacts of Extreme Environmental Conditions on Contact Lenses. CooperVision Practitioner. 2019.
Stapleton F, et al. CLEAR – Contact Lens Complications. Contact Lens and Anterior Eye. 2021.
Willcox MDP, et al. TFOS DEWS II Tear Film Report. The Ocular Surface. 2017.
Canadian Association of Optometrists. Contact Lens Care and Safety. CAO.ca. 2023.
