The Republic of Yemen, situated on the southern end of the Arabian Peninsula, is one of the poorest countries in the world. The country has a GNI per capita of US$1,070 (2010) compared with an average of US$2,321 for lower middle-income countries. In addition to significant development challenges, Yemen is particularly vulnerable to climate change. Rainfall is erratic and variable, a situation made worse by high evapotranspiration rates. Based on current high water consumption for irrigation and water supplies, it is expected that groundwater reserves will be nearly exhausted in next few decades. Flash floods and droughts are frequent hazards displacing thousands, causing loss of life and significant damage to assets and livelihoods. The floods of 2008, for example, killed 180 people, displaced 10,000 and caused damage and losses to infrastructure, shelter, and livelihoods equivalent to US$1,638 million amounting to 6% of Yemen’s GDP . Sustainable social and economic development in Yemen depends on knowledge of climate variability and change, and reliable and actionable meteorological and hydrological forecasts and warnings. Upgrading weather, climate and water information will reduce vulnerabilities to natural hazards and increase food and water security.