Beware trick-or-treaters — the good weather is soon expected to end.

After a mild Wednesday, the National Weather Service of Pittsburgh forecasts plummeting temperatures and long-lasting rain beginning Wednesday night and continuing all day Thursday. Unfortunately, unseasonably warm weather isn't expected to return any time soon, according to meteorologist Chris Leonardi.

“We're going to have one more dry day Wednesday,” Leonardi said Tuesday. “Rain is probably going to hold off until very late in the day. Everything pretty much goes downhill from there.”

Candy-seekers might find themselves contending with a dark and stormy night on Halloween. Long-lasting rain will deposit an inch to an inch-and-a-half, with some local areas seeing more.

The NWS forecast offered near certainty when it comes to Thursday precipitation.

“It's going to be a good soaking,” Leonardi said.

Don't bother incorporating an umbrella into your costume, either — wind gusts around 30 to 40 mph are expected to begin Thursday night.

Even after the Halloween weather system, further out forecasts look colder. Recent temperatures have averaged a solid 10 to 15 degrees warmer than usual, according to the NWS.

Friday temperatures looked likely to remain in the 30s all day.

Leonardi said Butler will be lucky to see temperatures reach 40 degrees on Friday.

The meteorologist offered one prediction for true Halloween-haters who prefer a white Christmas.

“We cannot totally rule out seeing a snowflake in this weather system,” he said. “That's just one snow flake, nothing of any significance.”

Halloween in Butler last year brought a high temperature of 66 and a low of 48, according to data compiled by Weather Underground, a weather website.

On Tuesday evening, Pittsburgh's NWS predicted a high of 65 and a low of 38 on Halloween this year.