Between 13 and 18 May 2014 a low-pressure cyclone designated Tamara and Yvette affected a large area of Southeastern and Central Europe, causing floods and landslides. Serbia and Bosnia and Herzegovina suffered the greatest damage, as the rain was the heaviest in 120 years of recorded weather measurements. By 20 May, at least 62 people had died as a result of the flooding, and hundreds of thousands had been forced from their homes. Towns of Obrenovac in Serbia and Doboj in Bosnia and Herzegovina account for most victims, after being inundated by several-meter high waters from nearby rivers.

Floodwaters caused over 2,000 landslides across Southeast Europe, spreading damage across many towns and villages. The rains activated torrents and mudslides, and subsequently several rivers in watersheds of Sava and Morava rose and flooded surrounding valleys. Official counts indicate that over 1.6 million people were affected in Serbia and Bosnia, after a week of flooding.

Assessments of the damage range up to €3.5 billion for Serbia, Bosnia and Herzegovina. Damage in Serbia, jointly estimated by EU, World Bank group and UN officials, stands at 1,55 billion euros. Officials in Bosnia stated that the damage could exceed that of the Bosnian War. The events initiated a large international aid campaign, with numerous countries, organizations and individuals donating humanitarian, material and monetary support for the affected areas.

On 13 May, a low-pressure area formed over the Adriatic Sea, as polar air from Central Europe penetrated into the Mediterranean basin. The cold polar air mass met with humid subtropical air, leading to very low pressure. On 14 May, the low moved over Southeast Europe, becoming stationary. As a result, extremely heavy rain fell within the region; Serbia (in the area around Belgrade) and Bosnia were most affected. Serbian and Bosnian meteorologists named the formed cyclone "Tamara". On 15 May, the daily amounts of rainfall broke historical records in Belgrade (107.9 mm), Valjevo (108.2 mm) and Loznica (110 mm). By 15 May, the monthly rainfall in Belgrade had broken the historical record (175 L from 1897), reaching 205 L. By Saturday, May 17, the rain had subsided, and the weather gradually became warmer and sunnier, somewhat easing relief and rescue efforts. On 18 May, the cyclone moved further northwest.

The main flooding region was the watershed of the Sava river, which forms a border between Bosnia and Croatia, flows into Serbia, and drains into the Danube in Belgrade. On Wednesday, 14 May, heavy rainfall caused torrential floods across mountainous regions, which destroyed bridges and infrastructure, and caused numerous landslides. The deadliest impact occurred on Thursday, 15 May, when water levels in several right-bank tributaries of the Sava suddenly and uncontrollably rose at an unprecedented rate, flooding towns in their valleys. The Bosna river in central Bosnia completely flooded the cities of Doboj, Maglaj, Zavidovići and Šamac, while the Kolubara, near Belgrade, did the same to Obrenovac; those cities had the major share of victims. Subsequently, the Sava itself rose to record-high levels, threatening the cities of Slavonski Brod, Šabac and Sremska Mitrovica and numerous villages, but the damage was relatively contained as the population, helped by army and volunteers, strengthened flood defenses. Nonetheless, embankments gave way in several places.

Heavy rainfall was also experienced in the region on 3 and 4 May, affecting Romania, Italy and Bosnia. The event produced limited damage but left a number of flooding incidents and high rivers. A state of emergency was declared in parts of Bosnia by local government.

Though heaviest affected areas were in the valleys of the Sava and Kolubara rivers, the center of the flood was the drainage basin of the Bosna river and its mouth into the Sava. Water in the Sava then broke through the newly constructed embankment on the left bank in Croatia and flooded the Lower Syrmia region. The water then uncontrollably rushed into the Bosut river which flows back into the Sava in Serbia. In Serbia, the heaviest floods were in the Kolubara river basin where the major rainfall caused extreme torrents in the mountains, causing the hydrological coincidence, a fact that high tidal waves appeared simultaneously on both the left and the right tributaries of the Kolubara. Rivers of Peštan and Vraničina also spilled over, flooding the surface mine "Tamnava-Zapadna Polje", within the Kolubara mines (see Lake Paljuvi). The flooded mines captured 200 million m3 of the flood water.

Belgrade's Institute "Jaroslav Černi", funded by UNDP, compiled a study "Improvement of the water protection in the Kolubara drainage basin". Hydrological section of the report concludes that the cyclone caused the "continual rain of temperate intensity", which however lasted for too long (over three days). In May, the measured 48-hours rainfall was higher than the millennial rains in Loznica while the return period in Belgrade and Valjevo was 400 years. Return periods of the flow in the Kolubara was 120–520 and at the confluence into the Sava, when the Kolubara flooded Obrenovac and the mines, the discharge was 1,456 m³/s (51,400 cu ft/s). If the system against the floods was finished and functioning properly, and that mines and Obrenovac weren't flooded, the discharge would be 2,460 m³/s (87,000 cu ft/s).