Best time to visit UP and Bihar, and the winter fog

Temperatures below are typical for Agra, Lucknow and Varanasi, which are similar. Bihar runs slightly warmer and more humid.

From roughly mid-December to late January, still, cold, humid nights over the Indo-Gangetic plain produce dense radiation fog. On bad days, visibility falls below 50 m at dawn and the fog may not lift until late morning or, occasionally, not at all. Spells can last several days. It is a regular feature of north Indian winters, not a rare event.

Fog affects travel more than sightseeing. Trains on the main lines between Delhi, Agra, Lucknow, Varanasi and Patna can run several hours late, and some services are cancelled in the worst weeks. Early-morning flights into and out of Agra, Lucknow, Varanasi, Patna and Gaya are often delayed or diverted, as not all airports and aircraft can land in very low visibility. Delhi airport has better equipment but still sees delays. Road travel slows sharply, and driving in thick fog at night is dangerous.

Sightseeing is affected mainly at dawn. The Taj Mahal can be invisible at sunrise, and the far side of the Ganges disappears at Varanasi. On the other hand, fog brings soft, atmospheric light, smaller crowds and lower hotel rates in parts of January.

We build every December and January journey with fog in mind. None of this is complicated, but it makes the difference between a delayed trip and a ruined one.

• Avoid tight connections between a train and a flight, or between two flights on the same day.
• Choose midday or afternoon flights rather than early-morning ones.
• Use private cars for key transfers, with daylight departures and experienced drivers.
• Keep a spare morning in Agra so the Taj Mahal sunrise can be repeated.
• Allow a buffer night before international departures from Delhi.
• Pack warm layers: dawn temperatures fall to 5 to 8 °C and fog feels colder.

From April, temperatures rise quickly, and by May afternoons regularly pass 40 °C, with hot, dry winds called loo. Sightseeing is possible only in the first hours after sunrise and after sunset. We do not recommend touring the cities from May to June. The exception is Dudhwa National Park, where heat concentrates animals around water and tiger sightings peak from March to May.

The monsoon arrives in the second half of June and lasts into September. Rain comes in heavy bursts rather than all day, and the countryside turns green. At Varanasi the Ganges rises over the lower ghats, the aarti moves to higher ground and boats may be suspended when the current is strong. Humidity is high, and some rural roads in Bihar become slow. It is a quiet, low-cost time for travellers who do not mind rain, especially in Agra and Lucknow.

The whole region shares one broad climate, but the details differ from place to place, and they shape how we plan each stop.

Agra and Mathura, in the west, are the driest part of the region. Winter days are bright and clear, and February and March are outstanding. This is also the area where fog is most likely to hide the Taj Mahal at dawn from mid-December to January, so we always keep a spare morning there. By April, the red sandstone of Agra Fort and Fatehpur Sikri radiates heat by late morning, and visits move to the first hours after sunrise.

Lucknow sits in the middle of the plain and has a similar winter, with slightly more humidity and fog. Its great advantage in December and January is food: this is the season for nihari, makhan malai and the richest Awadhi dishes, which taste best when the evenings are cold.

Varanasi and Prayagraj, further east, have softer, hazier light and mornings on the river that can be very cold in an open boat. The Ganges is at its most comfortable level from October to March. From July to September it rises over the lower ghats, and at Prayagraj the Mela grounds are under water until the river falls in autumn.

Bodh Gaya, Rajgir and the Bihar sites are slightly warmer and more humid. They have a strong pilgrim season from November to February, when monks and lay pilgrims arrive from across Asia, and they grow uncomfortably hot from April. Dudhwa, in the far north on the Nepal border, follows its own calendar: open from about mid-November to mid-June, with the best tiger sightings from March to May.

Many travellers choose their dates around a festival. Most follow the lunar calendar and move each year, so check current status before you travel.

• January to February: Magh Mela at Prayagraj; the Kumbh in its cycle years.
• February: Taj Mahotsav in Agra.
• February to March: Holi in Braj, with Lathmar Holi in Barsana.
• April to May: Buddha Purnima at Bodh Gaya, Sarnath and Kushinagar.
• October to November: Diwali and Chhath across the region.
• November: Dev Deepawali and the Ganga Mahotsav in Varanasi.
• December to January: Buddhist prayer gatherings at Bodh Gaya.

For a first visit covering the Taj Mahal and Varanasi, choose November or February. For the Buddhist circuit, choose October, November or February for calm, or December and January for the full pilgrim atmosphere, accepting fog. For Holi, choose the dates the calendar gives you, usually in March. For tigers at Dudhwa, choose March or April. For Lucknow's winter food, choose December to February.

Whatever the month, book the top hotels early for the peak weeks: Christmas and New Year, Holi, Dev Deepawali and the Magh Mela's main days. Hotel rates are highest from October to March and lowest from May to September.