The past few months in Calgary have been the hottest on record, in terms of consistently high temperatures, according to Environment Canada.

"Never since 1881, when records began in Calgary, has there ever been a warmer May, June and July," senior climatologist David Phillips said Wednesday.

"My gosh, if you want summer — good beer-drinking weather in a muscle shirt or tank top — Calgary's the place to be."

Environment Canada has issued another heat warning for Calgary, noting elevated temperatures are expected both day and night until Friday, at least.

Phillips said it's the overnight and early-morning temperatures that are particularly unusual, noting the forecast suggests it could be as warm as 19 C before the sun rises on Thursday morning.

'Uncharted territory'

"Let me tell you how rare that is," he said.

"There has never been in Calgary, with records that go back to the 1800s, a temperature in the morning — that is about 5 or 6 o'clock in the morning — as warm as 19 C. So this is something that is uncharted territory."

The previous record for early-morning temperature was set in 1889, Phillips said, at 16.7 C.

While the city isn't expected to break records for daytime highs in the next few days, Phillips said it's the sustained temperature levels throughout the day that prompted the heat warning.

"From a health point of view, that is the concern ... when it's those nighttime temperatures that don't cool off."

On average, Calgary has seen an average of 2.1 days each July that reach or exceed 30 C, based on Environment Canada's past 50 years of published weather data.

So far this July, there have been six days that cracked that mark: July 7, July 9, July 13, July 15, July 23 and July 27.

With files from the Calgary Eyeopener