Salt Range, but otherwise the distribution of grain sizes is irregular. The currently active Indus River flood plain stretches > 20 km in width at the southern edges of the desert and the abandoned floodplain reaches even wider, covering areas of higher ground. These uplands are actively eroded by the Jhelum River and form up to scarps which face the floodplain. As compared to the Upper Indus sand, the sand dunes of the Thal are poorer in quartz and sedimentary to low-rank metasedimentary rock fragments. However, they are higher in feldspars, volcanic, metavolcanic and metabasite rock fragments and heavy minerals. The dune sand is thought to be derived from the Transhimalayan arcs (40–45%, predominantly from the Kohistan arc), the Karakorum-Hindukush Ranges (40–50%, of which a third is via the Kabul River), the Nanga Parbat massif (< 10%), and the Himalayan belt (< 10%, inclusive of detritus recycled by the Soan River). Climate The Thal desert is a subtropical sandy region with severe climatic conditions that are prone to temperature extremes. Approximately 50% of the region sees hyper-arid climatic conditions (annual rainfall less than 200mm) and the remaining half sees semi-arid climatic conditions (annual rainfall between 200mm and 500mm). The desert is also characterised by strong winds that blow year-round and can cause serious wind erosion that leads to local crop damage. Temperature Summers in the area see temperatures generally range from 32o C - 40o C and average around 35o C between June to July. However, southern borne hot winds blowing with high velocity can see these temperatures rise to over 45oC. Dust storms, resulting from unsteady thermal conditions, are also common in the summer months. This has made crop cultivation challenging as the soil becomes difficult to bind, leading to extensive erosion and losses for the farming community. In the winter, temperatures vary between 3o C and 8o C and are accompanied by cold, dry winds from the north. In January, temperatures can reach near freezing point. Precipitation The Thal Desert's rainfall patterns are low and erratic with mean annual values ranging between 150-350mm. The majority of precipitation occurs between the months of June and August however there is high variability across seasons and even years. Total annual rainfall has been seen to progressively decrease from the northern end of the desert to the south. It also displays cyclic fluctuations where two to three years of continued decreased rainfall