Vodafone Australia has blamed an air-conditioning failure at its Melbourne switch for a three hour service outage late Thursday.
The telco noted in a network status update that the outage started at 7.42pm AEDT and was resolved at 10.45pm.
Users flooded internet forums such as Whirlpool looking for answers.
"We have identified what we believe is an air-conditioning failure in our Tullamarine switch which is impacting 15 percent of national voice traffic and a larger proportion of Victorian customers on 2G and 3G," Vodafone advised on its Facebook page.
Melbourne had suffered through soaring temperatures on Thursday, predicted to reach 37 degrees Celsius, but known to have been higher in parts of the city.