If you’re having a party in or around Hamilton tonight, you probably won’t need a winter coat under your suit.

Today is forecast to be the hottest Halloween on record in Ontario municipalities including Hamilton, Toronto, Burlington, St. Catharines, Lincoln, Niagara Falls, Toronto, Oakville, Mississauga and Brampton. Ottawa and several places in Quebec are also expected to set heat records.

According to CBC Climate Data Dashboardwhich sources data from the Meteorological Service of Canada, October 31 will see 122 heat records set.

In Hamilton, the predicted maximum temperature is 24°C, which the dashboard says is 13°C above the historical average. This average is calculated using data from 1981 to 2010.

It’s “not really unusual” to experience such warm temperatures in October, Peter Kimbell, warning preparedness meteorologist at Environment and Climate Change Canada, told CBC Hamilton. “We’ve seen it many times before.”

For example, Kimbell said, the previous October 31 record in Hamilton was 22.8C, recorded in 1971 and 1876. He said the region had experienced similar hot days around that time in 1901, 1933, 1946 and 1950 as well.

What’s happening now, Kimbell said, is that “a large pressure gradient” from the East Coast to the central part of the United States is causing winds to blow warm air from the southern United States to southern Ontario.

“The air is very warm in southern Ontario and, in fact, there was warm air in northeastern Ontario yesterday,” he said.

Climate modeling shows rising temperatures

In Hamilton, the average temperature over the past 30 days is 11.6°C, which is 2°C above the historical average.

While Hamilton’s hottest Halloween isn’t “smoking gun” in itself, Environmental Hamilton’s Ian Borsuk says it’s indicative of a broader trend toward a warmer climate.

Last year it was hottest ever recordedaccording to the European Union climate agency, and in recent weeks we have seen episodes of severe weather phenomena such as deadly flash floods in Spainwhich scientists say are increasing in frequency due to climate change.

“These problems will only get worse,” Borsuk said. “We’ve locked in this warming.”

Borsuk told CBC Hamilton he hopes the record is a “wake-up call” that we need more action to reduce greenhouse gas emissions.

“It’s entirely possible that this won’t be the hottest Halloween ever,” he said, adding that while some people grew up having to modify their Halloween costumes to stay warm , future children may have to get used to dressing casually because of the heat.

CBC’s Climate Dashboard says Hamilton is expected to be warmer on average by the end of the century. It depends on the scale of greenhouse gas emissions. In a low emissions scenario, the temperature will likely increase between 1.5 C and 3.8 C. In a high emissions scenario, the average annual temperature could increase by up to 8.1 C.

“The hottest Halloween on record could look like a superannuation impact of climate change in 10 to 20 years, because the effect in the future will be much worse,” Borsuk said.

A good opportunity to talk to neighbors about climate change

If the topic of heat comes up at a party, Borsuk recommends talking about it.

“The more we talk about it and the more we make individual commitments in our own lives, the easier it is for us to imagine and design the collective action we desperately need and demand governments follow through on.”

You may also want to bring an umbrella.

Kimbell said the forecast calls for rain this evening.