According to an analysis by ruidisonglights, the answer depends on the waterproof rating (IP rating) and the overall build quality of the lights. Here’s what you should consider:

When they can be left outside:

1. High Waterproof Rating (IP65 or higher)
   Lights with an IP65 or above rating are designed to withstand rain, snow, and freezing temperatures.

2. Specifically designed for outdoor use
   Products labeled “outdoor use” or “weatherproof” are generally safe to leave out in winter.

3. Cold-resistant materials
   Durable rubber or PVC cables are less likely to crack or become brittle in low temperatures.

Recommended precautions:

• Check if connectors and plugs are waterproof. If not, use protective covers or waterproof boxes.

• Avoid snow buildup on bulbs, as repeated melting and freezing may cause damage.

• Secure the lights firmly in windy areas to prevent tearing or wire breakage.

• Unplug the lights when not in use to reduce the risk of moisture-related issues.

When they should not be left outside:

• String lights designed for indoor use, such as those meant for Christmas trees, are not suitable for harsh outdoor conditions.

• Lights without a specified waterproof rating should not be exposed to snow or rain.

In summary:
Outdoor string lights that are waterproof, weather-resistant, and made for exterior use can safely stay up during the winter. However, indoor-only lights should not be used outdoors in cold or wet conditions.

If you’re looking for reliable, weatherproof string lights, ruidisonglights offers a variety of high-quality options perfect for year-round outdoor use.