The average annual temperatures are gradually increasing over time since few decades. This has led to global warming and change in climate. The increase in temperature has not only affected the humans but the flora too. In many flowering plants the temperature has altered the phenology (timing) of flowering, example Cassia fistula, Samanea saman, Delonix regia etc. An attempt is made to investigate the tree Delonix regia (Bojer ex Hook.) Raf. commonly known as Gulmohar. It is monitored for its flowering time since 2016 to 2019. The area selected for study was Bhayandar, Mira road, Andheri and Vile Parle in Mumbai. The data obtained was further analyzed with the literature from different Flora’s and research papers. The actual flowering time according to the old literature was April to June. Since few years it has been observed that Gulmohar flowered twice i.e. October to December and also April to June. The amount of flowers bloomed during October – December was scanty while mass bloom was witnessed during April to June. The phenology of flowering has shifted earlier in response to warming during October – December. The shift in the timing of flowering may have resulted in reproductive failure in the plant. This behaviour of plants is of great concern. More broadly it is important to mitigate climate change by controlling global warming in order to conserve the D. regia trees. It can be used as bio indicator stating the climate change in Mumbai.