Where is hot in March, before the heat turns serious

There is a short window each year when much of the northern tropics is at its most comfortable. The winter dry season is still in place, the skies are clear, and the heat that builds through April and May, to the point where sightseeing after eleven in the morning becomes an endurance test, has not yet arrived. In most of the places below, that window is March.

It is a month for doing things rather than lying still: walking round ruins, climbing temple steps, cycling between villages. By May you may want to do all of those at dawn or not at all.

The Yucatán, and the equinox

Mexico's Yucatán Peninsula is warm all year, but March is one of its best months: dry, sunny and hot without being oppressive. It is also the month of the spring equinox. Around the equinox, the late afternoon sun on the great stepped pyramid at Chichén Itzá, El Castillo, casts a series of triangular shadows down the edge of its northern staircase. The effect looks like a serpent's body joining the carved serpent head at the bottom. Whether the Maya builders intended it precisely is debated, but it draws large crowds, so if you go for it, go expecting company.

Explore Worldwide's Best of Mexico's Yucatán Peninsula, seven nights, starts on the coast at Playa del Carmen and visits the Maya cities of Cobá, Chichén Itzá and Uxmal. Uxmal is the most elegant of the three, with the ornate stonework of the Puuc style. The trip also includes the colonial towns of Valladolid, Izamal and Mérida, the cenote of Ik Kil, one of the great water-filled sinkholes that pock the limestone of the peninsula, and the estuary at Celestún, known for its flamingos.

The colonial towns are as much a part of the Yucatán as the ruins, and they make the history of the peninsula visible. Mérida, the regional capital, was founded by the Spanish in 1542 on the site of the Maya city of T'hó, and the stones of its pyramids went into the new cathedral. Izamal is painted almost entirely in ochre-yellow. Its great Franciscan convent of San Antonio de Padua, built in the sixteenth century, stands on the platform of a Maya pyramid, with older mounds still rising among the streets around it. In March both towns are warm and bright, and their shaded arcades and squares come into their own in the late afternoon.

Sri Lanka and the Maldives

In Sri Lanka, March is the tail end of the long dry season on the west and south coasts and in the hill country, before the thunderstorms of the inter-monsoon period that usually arrive in April. In the north-central dry zone, where the ancient cities are, it is hot but bearable, and it is worth starting early. Explore Worldwide's Highlights of Sri Lanka covers a great deal in six nights: from Negombo to Wilpattu National Park, the ancient capital of Anuradhapura and the hilltop shrines of Mihintale, across to Trincomalee on the east coast, then Dambulla, Sigiriya, the elephants of Minneriya, Kandy and Colombo.

The Maldives, further out in the Indian Ocean, are still in their dry season in March, with calm seas and clear water. It is a good month for snorkelling. G Adventures' Maldives Dhoni Cruise, six nights by traditional boat, sails among the local islands of the Vaavu atoll, including Fulidhoo and Felidhoo. The cruise runs until March and resumes in October.

Vietnam, from north to south

Vietnam stretches more than fifteen hundred kilometres from north to south, and its weather varies along the way, which makes March a particularly good month to see the whole country. In the south, around Ho Chi Minh City and the Mekong Delta, the dry season continues and it is hot. In the centre, Hue and Hoi An are past their rainy months and warming up pleasantly. In the north, Hanoi and the karst scenery of Lan Ha Bay and Ninh Binh are mild, sometimes misty, and comfortable for walking.

Explore Worldwide's Upgraded Discover Vietnam, thirteen nights, takes that whole length of the country. It starts in Hanoi and goes to Lan Ha Bay and Ninh Binh in the north, then to the old imperial capital of Hue and the merchant town of Hoi An. It finishes in the south, in Ho Chi Minh City, the Mekong Delta and Tra Vinh. March is one of its months.

Whichever direction you choose, March is the month to go if heat is something you want to enjoy rather than survive. A month later, the same places will be considerably hotter, and some of the pleasure of walking about in them will have gone.