(Reuters) – Power was restored by Thursday morning to more than half the 7.8 million homes and businesses that Hurricane Irma had left in the dark, leaving 3.1 million customers, or some 6.5 million people, still sweltering in the heat in Florida and Georgia without air conditioning, utilities said.

Most of the remaining outages were in Florida Power & Light’s service area in the southern and eastern parts of the state. FPL, the state’s biggest electric company, said about 1.4 million had no power on Thursday, down from more than 3.6 million on Monday.

NextEra Energy Inc-owned <NEE.N> FPL, which serves nearly 5 million homes and businesses, expects to restore power to essentially all its customers in the eastern portion of Florida by the weekend and the harder-hit western portion of the state by Sept. 22. It will take longer to restore those with tornado damage or severe flooding, FPL said.

Outages at Duke Energy Corp <DUK.N>, which serves the northern and central parts of Florida, fell to 855,000 on Thursday, down from a peak of about 1.2 million on Monday. Duke said on its website it expects to restore service to most customers by midnight on Sept. 17.

High temperatures were forecast to reach the upper 80s F (low 30s C) in Florida’s two biggest cities, Jacksonville and Miami, and the mid 80s in Atlanta over the next week or so, according to meteorologists at AccuWeather.

Irma hit southwestern Florida Sunday morning as a Category 4 storm, the second most severe on the five-step Saffir-Simpson scale. On Monday, when most customers were without power, the storm weakened to a tropical depression.

In Georgia, utilities reported outages declined to about 290,000 on Thursday, down from a peak of around 1.3 million on Monday.

Other big power utilities in Florida are units of Emera Inc <EMA.TO> and Southern Co <SO.N>, which also operates the biggest electric company in Georgia.

(Reporting by Scott DiSavino; Editing by Bernadette Baum)