Halloween temperatures will be spine-chilling for some trick-or-treaters

CNNTrick-or-treaters are in for a shock this Halloween as an impressive shot of cold air from Canada plunges into the US and temperatures plummet in its wake.

High pressure from Canada will slide into the central US and keep conditions dry for many trick-or-treaters. But it will also bring the cold air which may come as a surprise to many in the South and East who will be coming off a warmer weekend.

By Halloween, temperatures will be below-average across much of the country, save for the West Coast.

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Temperatures will start to drop in parts of the already cold Northern Plains Saturday. The cold will linger there, and bone-chilling temperatures in the 20s and 30s will be widespread on Halloween night.

Costumes might need a few extra layers in Bismark, North Dakota, which will have a high temperature of 27 degrees – more typical for mid-December than late October. Factor in the wind chill and it will feel like the mid-teens.

The cold is expected to creep into the Midwest and Central Plains by Sunday, bringing frosty conditions and much cooler temperatures through Tuesday. Kansas City and Chicago might struggle to reach the 40s on Halloween day.

The cold air will hit the mid-Atlantic and Southeast just in time for Halloween, causing temperatures to crash. On Monday, Birmingham, Alabama, will have a high temperature near 80 degrees. Just 24 hours later, the high temperature will only reach 58 degrees.

Mild and mostly dry conditions will prevail for the Southeast, but other parts of the country aren’t so lucky.

The Great Lakes could see a snowflake or two on Halloween as temperatures spiral downward. Erie, Pennsylvania, and Cleveland could see snow Tuesday evening overnight into Wednesday.

A few showers are possible in parts of the mid-Atlantic spanning southward into Tennessee, so Halloween plans could be foiled into Tuesday evening.

The West Coast will luck out this Halloween. Temperatures will be near normal, from the 50s to the mid 70s, and the region will also dodge rain.