Outdoor Lights Not Working After Rain — What This Tells You

Outdoor lights that go out every time it rains, then come back on when they dry out, are exhibiting one of the clearest patterns in residential electrical faults. The problem is moisture getting somewhere it should not be. The question is where, and how severe the ingress is.

This is particularly common in Melbourne, where periods of sustained heavy rain are more frequent than in Sydney, but it occurs across both cities regularly.

The Most Likely Cause: Compromised IP Rating on the Fitting

Outdoor light fittings are manufactured with an IP (Ingress Protection) rating that specifies how resistant they are to moisture and dust penetration. A fitting rated IP44 provides splash protection. A fitting rated IP65 provides full protection against water jets. A fitting with no rating or a low rating is not designed for outdoor use.

Over time, even a correctly rated outdoor fitting can lose its sealing effectiveness. Gaskets degrade, silicone seals shrink and crack, and lens covers develop hairline fractures. When rain falls, water enters the fitting and contacts the lampholder, creating a short circuit or triggering the RCD. Once the fitting dries out, it may work again.

The solution is to replace the fitting with one correctly rated for outdoor installation. This is a licensed electrician job.

RCD Tripping Due to Earth Leakage

If your outdoor lights are losing power and your safety switch inside has tripped, the fault is introducing earth leakage current. This is the RCD doing its job.

In Melbourne, where winter rain events can be prolonged, a poorly sealed outdoor fitting will absorb moisture into the wiring connections inside the fitting body. This creates a low-resistance path to earth through the moisture film, which the RCD detects and trips on.

The safety switch needs to be reset once the fault is identified and fixed. Do not repeatedly reset a safety switch that keeps tripping after rain without fixing the underlying problem. You are overriding a protection device that is correctly detecting a fault.

Our Melbourne electrician team attends outdoor electrical faults across metropolitan Melbourne. Sydney customers can book through our Sydney electrician page.

Moisture in the Junction Box

Many outdoor lighting installations have a junction box mounted on the exterior wall or in the eaves space where individual cable runs connect. If this junction box is not properly sealed, it can accumulate water during heavy rain, particularly if the box is mounted horizontally with the lid facing up.

Water in a junction box causes the same symptoms as water in the fitting: intermittent loss of power that resolves once it dries. An electrician will check the junction box sealing, the cable gland entries, and whether the box has appropriate drainage or is mounted in an orientation that traps water.

Cable Damage from UV Degradation or Physical Damage

External cables that are exposed to direct sunlight over years of Australian weather will eventually suffer UV degradation to their outer sheathing. When the sheathing cracks, rain can enter the cable itself and travel along the insulation to the connection points. This type of fault can be difficult to locate because the visible section of cable may look intact while the internal damage is further along the run.

If your outdoor lights have never had the exterior cable replaced and the property is more than fifteen to twenty years old, cable condition is worth assessing during an electrician visit.

Frequently Asked Questions

Q1: Why do my outdoor lights work in dry weather but not after rain?
This is a classic moisture ingress pattern. Water is entering the light fitting, junction box, or cable at some point and creating either a direct short or an earth leakage path that triggers the safety switch. The fault appears during rain and disappears as the fitting dries out. It needs to be physically located and repaired rather than simply reset each time it occurs.

Q2: Can I seal my outdoor light fitting myself to keep water out?
Applying silicone around the rim of an outdoor fitting is a temporary measure some homeowners use, but it does not address faults that have already developed internally in the fitting or its wiring connections. If the fitting has already been water-compromised, the lampholders, internal wiring, and connections need to be inspected before re-sealing. A licensed electrician can assess the fitting and advise whether repair or replacement is the correct approach.

Q3: What IP rating do outdoor lights in Melbourne or Sydney need?
As a general rule, outdoor wall lights under an eave in a sheltered location require a minimum of IP44. Lights exposed to direct rain or spray, such as in an uncovered alfresco or garden area, should be IP65 or higher. Lights near pools or in high-humidity areas like under a carport close to a sprinkler system should be IP66 or IP67. Always check the IP rating of any replacement fitting before installation.

Q4: Are outdoor electrical faults covered by home insurance?
Accidental electrical faults, including those caused by water damage, are generally covered under standard home and contents insurance, subject to your policy terms. However, faults resulting from known issues that were not repaired, or from DIY electrical work, may not be covered. Keeping records of licensed electrician repairs and certificates supports any future claim.

Q5: My outdoor power point also loses power after rain. Is this the same problem?
Yes, the same moisture ingress principles apply to outdoor power points. Outdoor GPOs must have spring-loaded weatherproof covers that snap closed when not in use. If the cover is broken, missing, or the seal behind the faceplate has deteriorated, rain entering the outlet will cause the same RCD trip behaviour. Replace any outdoor power point with a broken or missing weatherproof cover as a priority.