NEW DELHI (Reuters) – India’s annual monsoon, which delivers about 70 percent of the country’s rainfall, officially arrived on the coast of Kerala on Saturday, the weather office said, a week later than usual.

The delay has had a big impact on farmers and millions of Indians this year, as an ongoing heat wave has sent temperatures soaring across the country and dried up reservoirs.

Monsoons are the lifeblood of India’s $2.5 trillion economy, spurring farm output and boosting rural spending on items ranging from gold to cars, motorcycles and refrigerators.

Water is typically scarce in the summer months, but the situation has been particularly grim this year in western and southern states which received below average rainfall in the 2018 monsoon season.

The India Meteorological Department (IMD) said in April that India, where half of the farmland lacks irrigation, would likely receive average monsoon rains this year.

The weather bureau declares the arrival of monsoon rains only after measures including consistency of rainfall over a defined geography, intensity, cloudiness and wind speed are met.

It defines average rainfall as between 96 percent and 104 percent of a 50-year average of 89 cm (35 inches) for the entire four-month season beginning June.