Indian voters are battling sweltering conditions to take part in the world’s biggest election as a severe heat wave hits parts of the country and authorities forecast a hotter-than-normal summer for the South Asian nation.

The India Meteorological Department (IMD) said a heat wave will affect parts of south and east India until the end of the week, including four states that are voting on Friday.

Parts of West Bengal, Bihar, Uttar Pradesh and Karnataka are among 13 states and union territories voting in the second phase of India’s mammoth elections, with temperatures forecast to exceed 40 degrees Celsius (104 degrees Fahrenheit) in some areas.

On Thursday, Baripada in the eastern state of Odisha hit 43.6 C (110.4 F) and Telangana’s Khammam in the south reached 43.4 C (110.1 F), according to the IMD, which warned last month that India would likely see stronger and longer heat waves this year due to above-normal temperatures.