History:
According to the history of Dehradun, it was originally part of the Garhwal kingdom for a long time except for a brief Rohilla interlude. Nestled in the Himalayas, Dehradun is one of the oldest cities of India and is presently the Provisional Capital of the newly created Uttaranchal or Uttarakhand state since November 2000. For about twenty years it was under Gorkha occupation. In April 1815, the Gorkhas were ousted and Garhwal annexed by the British. Tehsil Dehradun thus became part of Saharanpur district. Within 1825 and 1871, the history of Dehradun shows that it constituted part of Kumaon, Meerut, Saharanpur and Garhwal divisions respectively. 
According to popular belief, Rama and Lakshmana performed penance here while the Pandavas took rest here during their ascent of the mountains. Dehradun was once ruled by Emperor Ashoka (1st century BC), whose rock inscription has been discovered near Kalsi nearby. At different times, this area passed into the control of Sikhs, Mughals and Gorkhas. It served as a British army base and educational center after 1815. Post-independence, Dehradun has transformed from a peaceful sub-Himalayan town to a busy commercial hub. Local agitations for a separate hill state were initiated from this town.

Geography:
The geography of Dehradun shows it as being located at the center of the Doon Valley in the state of Uttaranchal, forming part of the Garhwal Himalayas. The Himalayas lie to its north, the Shivalik range to its south, the Ganges to its east and the Yamuna to its west. It is about 235 kilometers from Delhi. Once under British rule, Dehradun has preserved its colonial tinge despite considerable modernization. The magnificent landscapes and excellent infrastructure attract numerous visitors to Dehradun. 
Dehradun enjoys a pleasant climate. During the summer months, temperatures range between 36°C and 16.7°C. Winter temperatures vary between 23.4°C and 5.2° C respectively. Dehradun is today a major academic and research center and a popular summer retreat. Although the weather is pleasant throughout the year, the geography of Dehradun reveals April to July to be the ideal time for traveling to Dehradun.

Weather:
The geographical location of Dehradun is mainly responsible for the ever-changing but pleasant weather of Dehradun. Dehradun has a sub-tropical climate with cold winters, warm and colorful springs, humid and hot summers and an elongated monsoon. Since Dehradun is an inter-mountain valley and is positioned between an altitude of 2,300 - 3,300 ft (1000 m) above sea level and is surrounded by forests and mountains, its weather changes abruptly sometimes.
The spring here remains from the months March to mid April with a mild temperature, sunny days and pleasantly cool nights. Summer follows the spring season from mid April to June end. This time period is has very contrasting temperature with extremely hot days and erratic rain showers bringing cold winds.