Your May Tropical Homestead Checklist

One millimetre of rain falling on one square metre of roof gives you 1 litre of water.

So a 100 square metre roof in a 20 mm storm catches 2,000 litres, about ten bathtubs. Not all of it reaches the tank, because some splashes off or goes to the first flush. Texas rainwater experts say installers count on 75 to 90% of it.

That means one good tropical storm can put roughly 1,500 litres in your tank. After months of dust, that's a lot of drinking, washing and watering.

The first rain after the dry spell washes all that dust and droppings off the roof. The CDC, the US health agency, says that first water carries most of the dirt and germs.

Make sure your first-flush diverter is empty and working, so that dirty water goes to the ground instead of into the tank.

Once a tank is full, extra water has to go somewhere. Make sure the overflow pipe runs well away from the house's walls and foundations.

Cover every opening, including the overflow, with fine mesh. Otherwise it becomes a front door for mosquitoes, frogs and rats. Our rainwater harvesting guide explains tanks, overflows and safe drinking water.

Fresh rain can stir up the mud at the bottom of a tank. Until you know the water is clean, treat what you drink.

Boil it the way February's list explains, and filter cloudy water or let it settle first.

Mosquitoes are the dark side of the rains. The kind that spreads dengue fever lays eggs just above the waterline in buckets, tyres and pots.

Here's the sneaky part. The CDC says those eggs can survive drying out for up to 8 months, then hatch as soon as rain covers them. From egg to flying mosquito takes only 7 to 10 days.

So the CDC's advice is a weekly habit: once a week, empty and scrub, turn over, cover or throw out anything that holds water. That includes plant pots, seed trays and garden containers. The World Health Organization says about half the world's people now live where dengue can spread.

It's tempting to sow the day after the first storm. But the first rains can be a "false start": a few showers, then a dry spell of a week or more.

Seeds that sprout and then dry out are lost. Researchers at Delft University of Technology studied this in West Africa. Sowing straight after the first rains raised the risk of water stress, because the soil hadn't stored enough moisture yet.

So wait until the rains have settled in and the soil is moist deep down, not just on top. Local farmers and your weather service know the usual pattern where you live, because every tropical climate keeps its own calendar.

Then it's time to plant. So what should you plant in May in the tropics? Not the same vegetables as the dry months. Once the rains are established, the garden wants plants that thrive in warm, wet weather:

"Fix nitrogen" sounds like something a mechanic does. It just means these plants pull plant food out of the air and leave some in the soil for the next crop.

Before you sow, prepare the garden beds so they drain. Norrington builds raised beds from whatever she has: old tin, wood, blocks, even old carpet. Then direct sow the big seeds like corn and beans straight into the bed, where they grow quickly in the warm, wet soil.

Tomatoes are the odd one out. The University of the West Indies notes that heavy rain damages their flowers, and Gardening Australia calls the Darwin wet too hot and humid for them. If you want tomato fruit, save that job for the dry season.

Heavy tropical rain hits bare soil like a drum, washing the best topsoil away. Keep beds covered with mulch, or with plants, so the rain soaks in instead of running off.

Gardening Australia suggests coarse mulch like hay or leaves, which softens the hit of big raindrops. Charles Darwin University's gardening expert Scott McDonald adds a catch: mulch breaks down quicker in the wet, so top it up regularly.

Rain also washes plant food away fast. That's why Gardening Australia suggests applying a bit of fertiliser to tropical greens every week or so while the rains last. Our off-grid garden guide covers soil, compost and watering.

The first heavy rain is the real test of your roof. Look at ceilings, walls and window frames for wet patches the morning after.

Act fast when you find one. The CDC says wet things should be dried or removed within 24 to 48 hours to stop mould from growing.

Rain that pools against a house soaks into walls and floors. Clear the drains and ditches around the house, and make sure gutters and downpipes lead water away.

Our guide to building an off-grid home explains why a house starts with a dry, well-drained spot.

Clouds cut solar power, but they don't stop it. In Bangkok, PVGIS figures show one kilowatt of panels making about 3.9 kilowatt-hours a day in May, against about 4.7 in March.

A kilowatt-hour is an amount of electricity, about what a small heater uses in one hour. So May still gives you roughly four fifths of March's power.

The real test comes later, in the cloudiest weeks. Our guide to how many solar panels you need shows how to size a system for the darkest month, not the brightest.

A compost heap needs to be damp, like a wrung-out sponge, but not soaked.

When the rain soaks a heap, water fills the gaps where air should be. Without air, the heap starts to smell like rotten eggs, and the rain also washes nutrients out of the bottom.

So cover the heap with a lid, a tarp or a thick layer of dry leaves during heavy rain. Our guide to home composting explains how to rescue a soggy heap.