Weather

A batch of Canadian air will sprawl from the Great Lakes to coastal areas of New England and the upper part of the Middle Atlantic on Saturday. Temperatures are forecast to be 20 to 30 degrees lower than in recent days and weeks. A frost and freeze may even visit parts of the northern tier at night.

Farther south, rain showers and thunderstorms will extend from the Tennessee Valley to the southern Appalachians and lower Middle Atlantic. A few of the downpours can be heavy enough to cause urban flooding. South of this zone, warm and humid air is forecast to hold on, with thunderstorm activity remaining minimal.

Farther west, torrential rain will raise the risk of flash, urban and stream flooding over the southern Plains to part of the lower Mississippi Valley. Areas at greatest risk for life-threatening flooding will include parts of northern Texas, southeastern Oklahoma and northwestern Arkansas.

Most areas from the northern Plains to the Southwest can expect dry weather. There will be an elevated risk of wildfire ignition and spread from parts of Nevada and Utah to Northern California, southern Idaho and southeastern Oregon. A few showers will dampen the northwest corner of the nation.

FOCUS: Fall Returns to the Northeast

After severe thunderstorms concluded Friday, Saturday will feel cooler and less humid from the Great Lakes to the Northeast. The weather will be fitting for the official start to astronomical autumn, which occurs at 9:54 p.m. EDT this evening.