Nov 6 (Reuters) - Pinnacle West Capital PNW.N on Wednesday posted a fall in third-quarter profit as higher operating and maintenance costs offset gains from favorable weather and more electricity usage.

The electric utility firm said its service areas experienced record temperatures during the summer months, leading to higher electricity consumption.

However, excessive heat along with persistent windy and dry conditions also stoked wildfires across the U.S. Southwest in July.

Adverse weather can significantly impact utilities, leading to increased operation and maintenance costs due to potential damages to power lines, equipment failure and service disruptions.

Pinnacle West's operating expenses for the July-to-September quarter rose to $1.22 billion, from $1.12 billion a year ago.

Phoenix, the largest city in Arizona, endured a record-breaking 113 consecutive days of temperatures exceeding 100 degrees Fahrenheit (38 degrees Celsius) in September, resulting in numerous heat-related fatalities and widespread wildfires.

Pinnacle West provides electric services to about 1.4 million customers through its largest subsidiary in Arizona.

Total interest expenses rose 12% to $98 million in the quarter.

Pinnacle expects 2025 consolidated earnings of $4.40 to $4.60 per share.

The utility raised its annual adjusted earnings forecast to between $5 and $5.20 per share, from its earlier estimate of $4.60 to $4.80. Analysts expect $4.92 per share, according to data compiled by LSEG.

The Phoenix, Arizona-based utility said net income attributable to common shareholders declined slightly to $395 million for the quarter ended Sept. 30, from $398.2 million a year earlier.

(Reporting by Pooja Menon in Bengaluru; Editing by Devika Syamnath)

((Pooja.Menon@thomsonreuters.com;))