Terai Heat, Monsoon and Fog: A Practical Guide

The Terai sits at about 60 to 300 m above sea level, at the northern edge of the Gangetic plain. It shares the climate of northern India far more than that of Kathmandu or Pokhara. Many visitors come straight from the cool hills and are surprised by the difference: a spring morning in Pokhara at 20 °C can become an afternoon in Chitwan at 35 °C, just five hours down the road.

Weather shapes everything here: when animals come out, when tracks open, whether flights leave on time and how much you can comfortably do in a day. The good news is that the Terai's seasons are predictable, and with a little planning you can travel well in almost any month. This guide covers what to expect and how to handle it in Chitwan, Janakpur, Koshi Tappu and the rest of the lowlands.

Use this table as a quick guide. Temperatures are typical daytime highs for Chitwan; Janakpur and the far western Terai are usually a little hotter in spring and summer, and Koshi Tappu a little more humid.

From April the Terai heats up fast. By May, afternoons in Chitwan often reach 36 to 40 °C, and towns further west such as Nepalgunj and Dhangadhi can be hotter still. Humidity rises in June as the monsoon approaches, which makes the heat feel heavier. Yet this is also when tiger sightings are most likely, grass is short and parks are quiet, so many keen wildlife travellers come anyway.

The key is to follow the local rhythm. Safaris start at first light and finish by mid-morning, then begin again in the late afternoon. The middle of the day is for shade, rest, a swim if your hotel has a pool and plenty of water. Light, loose, long-sleeved clothes protect better than shorts and T-shirts, and a wide hat makes a large difference in an open jeep.

• Drink at least 3 to 4 litres a day, more on safari days
• Use oral rehydration salts once a day in very hot weather
• Avoid alcohol in the heat of the day
• Know the signs of heat exhaustion: headache, nausea, dizziness, heavy sweating
• Choose a room with air conditioning or a good fan in May and June

The monsoon usually reaches the Terai in mid-June and stays until late September. Most of Nepal's annual rain falls in these months, often in heavy afternoon and night-time downpours with sunny breaks in between. The jungle turns deep green, rivers rise fast and the air is thick and warm.

Inside Chitwan, many park tracks close or become impassable, canoe trips may stop when the Rapti runs high, and walking safaris bring leeches. Some lodges close or scale down from about June to September. On the roads, landslides between Mugling and Narayanghat and on hill sections of the East-West Highway can cause long delays, and floods occasionally cut roads in the eastern and western Terai. Flights generally run, though weather can delay them.

If you do travel in the monsoon, keep plans flexible, carry a light rain jacket and a dry bag for cameras and phones, and wear leech socks on walks. Prices are lower and the jungle is quiet. Check current status before you travel, especially for roads and lodge openings.

From mid-December to late January, dense fog often blankets the Terai in the mornings, sometimes lasting into the afternoon. Temperatures at dawn drop to 5 to 9 °C, and days without sun can feel raw and damp, especially in Janakpur and the eastern Terai. Local people call these cold spells sheetlahar, cold waves, and they are hard on poor households with little heating.

For travellers, fog has two main effects. Flights into Bharatpur, Janakpur, Biratnagar and other Terai airports can be delayed or cancelled, so leave a buffer before international connections. Early-morning safaris start cold and grey, and an open jeep at 6 am can feel close to freezing. Bring a fleece, a windproof jacket, gloves and a warm hat. The reward is soft, misty light for photography and very few mosquitoes.

The Terai has health risks that the hills do not. Mosquitoes are the main concern. Malaria is now much less common than it once was, but cases still occur in some Terai districts, and dengue has caused large outbreaks in Nepal in recent years, including in 2022 and 2023. Japanese encephalitis is also present in the lowlands. See a travel clinic before you go for advice on vaccines and antimalarials.

Use repellent with DEET or picaridin, especially at dawn and dusk, sleep under a net or in screened rooms, and wear long sleeves in the evening. Drink only bottled, boiled or filtered water, and be careful with raw salads in the heat. Snakes are most active in the monsoon; walk with a torch at night and watch where you step. Carry a basic first-aid kit with rehydration salts.

Packing for the Terai is mostly about light layers and protection from sun and insects. If your trip combines the hills and the plains, as most do, you will need both a warm layer for Kathmandu evenings and winter safaris and light clothes for the heat. Laundry is cheap and fast in most hotels, so pack less than you think.

Neutral colours are best for safaris: green, khaki, brown or grey. Bright colours and white stand out in the jungle. For temple visits in Janakpur and Lumbini, bring at least one outfit that covers shoulders and knees, and shoes you can slip off easily.

• Light long-sleeved shirts and trousers in breathable fabric
• A fleece and windproof jacket for December to February mornings
• Wide-brimmed hat, sunglasses and high-factor sunscreen
• Insect repellent with DEET or picaridin
• Refillable water bottle and purification tablets or filter
• Oral rehydration salts and a basic first-aid kit
• Light rain jacket and leech socks from June to September
• Binoculars, a head torch and a dry bag for electronics

For most travellers, October to March is the best time to visit the Terai. October and November bring clear skies and festivals; December and January are cool, with fog; February and March offer the best wildlife and comfortable temperatures. April is still good if you can handle the heat. May and June are for dedicated wildlife watchers, and July to September for the flexible and adventurous.

Whatever the season, build in spare time. A fog delay, a landslide or a flooded road can cost a few hours or a day. We plan Terai trips with buffers, choose hotels with reliable power and air conditioning in hot months, and adjust activities to the weather on the ground. Ask us about conditions for your dates, and check current status before you travel.