Lhasa, situated at an altitude of approximately 3,650 meters (12,000 feet) in a river valley basin, possesses a temperate semi-arid alpine climate. Known as the "City of Sunlight," it receives over 3,000 hours of annual sunshine, creating a weather profile that is surprisingly mild despite its high-altitude setting.
Typical Weather Patterns
Lhasa’s weather is characterized by thin air, high transparency, and distinct dry and wet seasons. The city avoids both the extreme heat of lower-latitude summers and the severe, humid cold found elsewhere. Instead, it experiences strong solar radiation that provides warmth even when air temperatures are low. Winds are generally stronger during the dry winter months and subside during the calm, humid summer.
Diurnal Climate Behavior
One of the most defining features of Lhasa’s climate is the large diurnal temperature range, which often exceeds 15°C (27°F) in a single day.
- Morning/Evening: Temperatures drop sharply as soon as the sun disappears behind the surrounding mountains. Even in summer, nights can feel chilly.
- Midday: Under thin atmosphere, the sun feels remarkably intense. Between 11:00 AM and 4:00 PM, the "perceived" temperature is significantly higher than the recorded thermometer reading.
- The Night Rain Phenomenon: A unique characteristic of Lhasa’s summer (July and August) is that approximately 80% of the rainfall occurs at night. Locals often go through a sunny, bright day only for the basin to experience refreshing moderate rain after sunset, which clears the dust and cools the air for the following morning.
Seasonal Trends
- Spring (March – May): A transitional period where the weather warms rapidly. This is the windiest time of year, and the UV index begins its climb into the "extreme" category. The landscape begins to bloom, but the air remains dry.
- Summer (June – August): The wet season. While temperatures are at their highest—averaging 23°C (73°F) in June—humidity increases, making the air feel more "breathable" compared to the dry seasons. Cloud cover is more common, providing occasional relief from the sun.
- Autumn (September – October): Often considered the most balanced season. The monsoon rains retreat, leaving the atmosphere clear and crisp. Daytime temperatures remain pleasant while nighttime frost begins to appear by late October.
- Winter (November – February): Short and dry. While nights are freezing, reaching as low as -10°C (14°F), daytime highs often hover around 7°C to 10°C (45°F-50°F). Snow is infrequent in the city itself, usually appearing only as a white cap on the surrounding peaks.
Specific Weather Phenomena
- Intense UV Radiation: Due to the thin atmosphere and low ozone column, the UV index in Lhasa frequently reaches levels of 12 to 15, and has historically peaked as high as 20. Skin can begin to burn in as little as 10 to 15 minutes of direct exposure.
- Urban Microclimates: The "Heat Island" effect is noticeable in the central Lhasa city area (near Barkhor Street and the Potala Palace), where stone and concrete surfaces retain heat. Conversely, areas near the Lhasa River feel noticeably cooler and more humid.
Historical Context & Local Experience
Historical data shows a warming trend in Lhasa, particularly in the rising minimum (nighttime) temperatures. Recent decades have seen the summer season slightly lengthening. Locals adapt to these conditions by utilizing the intense sun for sustainable energy and timing outdoor activities for the early morning or late afternoon to avoid the peak UV window. Many residents track the "night rain" patterns to manage agriculture and daily commerce, as the predictability of the evening showers allows for clear-skied business hours.