The Indian stock market recorded sharp gains on Monday, with Sensex and Nifty extending rise for the fourth consecutive session as heavy rainfall revived monsoon hopes, FIIs turned net buyers and other factors further boosted investor sentiment.Sensex jumped more than 600 points to cross 78,370 while Nifty 50 gained 177 points to 24,447, as seen at 1.15 pm. The sharp gains added more than Rs 2 lakh crore to the total market capitalisation of all companies listed on the NSE, pulling it up to Rs 482 lakh crore.HDFC Bank shares surged around 4% to lead gains on the Sensex, while Mahindra & Mahindra (M&M), Bharat Electronics (BEL), Reliance Industries, ICICI Bank and Bharti Airtel gained 1-2%. Bucking the trend, Kotak Mahindra Bank shares dropped around 4% to lead losses on the benchmark index.Broader markets also hovered in the green, although with lesser gains than the benchmark indices. Nifty Smallcap 100 and Nifty Midcap 100 indices gained up to 0.5% This came even as India VIX, which measures volatility in market, gained more than 1% to 11.93 in the afternoon.Here are six factors which are boosting market sentiment today.1) Heavy rainfall revives decent monsoon hopesIndian equities earlier last week faced strong defence at higher levels as a patchy start to the monsoon prompted profit-booking near key psychological levels. However, various parts of India saw heavy rainfall over the weekend, with the India Meteorological Department (IMD) placing several cities including Mumbai on red alert, reviving hopes for a decent monsoon season.“Investors will closely track the progress of the monsoon season, given its implications for rural demand, agricultural output, and inflation trends,” Bajaj Broking had said.2) FII buyingForeign institutional investors remained net buyers of Indian equities on Friday, purchasing shares worth more than Rs 1,355 crore on Dalal Street, according to provisional data available on NSE. According to VK Vijayakumar, Chief Investment Strategist at Geojit Investments, the revival of monsoon and FIIs turning buyers last Friday are positives for the market in the near-term.More to come...