Mid-May will be dominated by bouts of moderate to heavy rainfall across the nation's northern tier and in the Southeast, along with significant temperature changes.

In addition, we'll be monitoring for our first subtropical or tropical depression or storm of the 2018 Atlantic hurricane season.

Here are five things you should know about this week's weather.

1. Watching the Gulf Coast for Subtropical or Tropical Development

An area of low pressure will be closely monitored for subtropical or tropical development in the Gulf of Mexico this week as it spreads heavy rainfall across Florida and other parts of the Southeast.

When low-pressure systems like this one form over the waters of the Gulf this time of year, we must always watch them closely for potential development.

(MORE: Subtropical or Tropical Development Possible in Gulf of Mexico)

Right now, the National Hurricane Center gives the system a medium chance of development into a subtropical or tropical depression or storm over the next five days. Heavy rainfall will be the primary concern regardless, especially in the Sunshine State.

If it were to develop, this would be the first subtropical or tropical depression or storm of the 2018 Atlantic hurricane season, which doesn't officially begin until June 1. If it reached tropical storm strength, it would earn the name Alberto.

(MORE: When Hurricane Season Starts Early)

Whether or not the system becomes subtropical or tropical, much of central and southern Florida can still expect at least 1 to 3 inches of rainfall through midweek. Locally higher amounts are expected in heavier thunderstorms, and totals of 3 to 7 inches are likely in southeastern and eastern Florida through midweek.

2. Active Wet Pattern for Much of the Northern Tier

Disturbances in a zonal weather pattern – one that goes from west-to-east rather than south-to-north – will tap into abundant moisture in the eastern half of the nation this week. The Gulf of Mexico system mentioned above will contribute to this influx of moisture.

This will result in numerous bouts of showers and thunderstorms, as well as increased humidity from parts of the Plains and Mississippi Valley to the East Coast.

Locally heavy rain is possible, potentially resulting in some flash flooding. Scattered strong to severe storms could also flare up at times.

(MORE: We're Entering the Prime Time of Year For Flash Flooding in the U.S.)

3. A Change in Seasons in the Midwest and Northeast

After chilly temperatures late last week and into the weekend, warmer weather is returning to the Midwest and Northeast.

Highs in the 70s and even some 80s will be common in the Midwest this week. The exception will be locations on parts of the immediate coastline of the Great Lakes, where temperatures may remain cooler.

Some spots in the Midwest will see highs up to 30 degrees warmer on Monday compared to last Friday. Minneapolis, which had a high of 53 degrees last Friday, will warm to the upper 70s or low 80s much of this week.

After a cool Sunday, a surge of warm air will bring highs in the 70s and 80s back into the Northeast early this week.

New England will cool off some by mid- to late-week, but most of the Northeast will stay warm through at least Thursday. 

(MORE: Spring Heat Makes Water Activities Tempting, But Cold Water Can Be Very Dangerous)

4. Record Warmth to Fade Away in the South

Temperatures will be at record- or near-record-warm levels early this week in parts of the mid-Mississippi Valley, Ohio Valley and the South.

The following cities will be close to setting new records (current record is in parentheses):

• Monday: Memphis (91 degrees); New Orleans (91 degrees); Atlanta (91 degrees)
• Tuesday: Cincinnati (80 degrees); Little Rock (94 degrees); Nashville (91 degrees)

As mentioned earlier, increased cloud cover and showers and thunderstorms will arrive in the East by midweek. This will lead to a decrease in temperatures across most areas.

5. Western Rainmaker Late-Week

While winds will generally be weak this week across the Lower 48, at least one stronger disturbance is possible late in the week on the West Coast. 

There are indications that a trough of low pressure, or southward dip in the jet stream, is likely to develop over the West late week.

This system should ride the periphery of the drought area in the Southwest, which means rain is not expected across the Four Corners region. 

Some rain, however, could alleviate the moderate drought in parts of Oregon and Nevada. It's too early for exact rainfall amounts, but some locations may see more than an inch. 

(MAPS: Weekly Planner)

Unfortunately, this system may also bring rainfall to the northern Rockies, including Montana and northern Washington, which have been experiencing flooding over the last couple of weeks. Rivers are likely to once again experience rises from the additional rain.