An autumn deluge has brought parts of the desert interior of Western Australia their best April rain in decades.

Mount Keith, almost exactly in the centre of WA, saw the heaviest falls with 40mm recorded in the gauge. This was their wettest April day in 22 years. Just up the long road, Carnegie picked up 31mm, its best April rain in 12 years. With these locations located in the middle of one of the world's largest deserts, this rain was about 20% of the annual rainfall for both locations, and a bit over one month's worth of rain in a few hours.

Both Leinster (29mm) and Laverton (6mm) had their wettest April day in 4 years, with more thunderstorms passing over on Tuesday afternoon.

GIF: Satellite, radar, and lightning over WA during yesterday's storms

All up on Monday and Tuesday morning, over 557,000 lightning flashes were recorded over WA. Most of these occurred in the Kimberley and central interior of the state.

Image: Lightning strikes recorded by the Weatherzone Total Lightning Network within 800km of Lake Carnegie on Monday and Tuesday morning

Moisture has been feeding into a trough over WA from the remnants of ex-Tropical Cyclone Herman, as well as a pulse of tropical activity happening off the northwest shelf. This mixed with some leftover heat from summer is pushing the instability well inland.

Showers and storms are continuing on Tuesday afternoon and will likely pick up again on Wednesday, before the trough starts to move east and ease over WA.