MD Weather Alerts

Overnight Edition

Wednesday, August 19, 2026

Tonight is the calm before it. NWS Baltimore/Washington (LWX, 3:13 PM issuance) and NWS Mount Holly (PHI, 5:48 PM) both describe a quiet, mostly clear night statewide as high pressure makes its exit — but clouds build in from the west after midnight ahead of a cold front, and Thursday brings a legitimate multi-hazard day: widespread showers and thunderstorms, an SPC slight risk for severe weather along and east of I-95, and a Flash Flood Watch consideration creeping toward our northeastern counties. Enjoy tonight. Thursday’s the one to watch.

Tonight’s Timeline

• Evening (now–10 PM): Clear to partly cloudy statewide, comfortable and noticeably less humid. Light west-to-southwest winds.
• Late evening–midnight: Skies stay mostly clear across central and southern MD; western Maryland starts seeing patchy fog develop in the valleys as winds go calm.
• Midnight–dawn Thursday: Cloud cover thickens from west to east as the approaching cold front and a warm front lifting north send in the first showers — Garrett and Allegany counties see rain chances climbing toward daybreak, with Washington and Frederick counties next in line by early morning.
• Thursday morning: Showers spread east across the state; storms fire more widely by afternoon, strongest and most organized along and east of I-95 into the evening.

Western Maryland

Garrett County (Deep Creek/Oakland): Overnight low near 61° — a genuinely cool, pleasant mountain night. Winds go light southwesterly, near calm by early morning, and patchy fog settles into the valleys and around the lake. Rain chances climb overnight (30%) ahead of Thursday’s more organized system, when highs reach the low 70s under mostly cloudy, foggy skies with an 80% chance of showers.

Allegany County (Cumberland): Low tonight near 65°, mostly cloudy with patchy fog developing, especially in the Narrows and along the Potomac valley. Rain chances near 32% overnight, jumping sharply Thursday (86%) with a high near 80° — Cumberland’s the first MD metro area to get worked over by this system.

Northern & Central Maryland

Washington County (Hagerstown): Overnight low around 67°, partly cloudy with just a slight chance of a late shower (18%) as the warm front noses in. Thursday brings a high near 82° with a 79% chance of showers and storms — patchy fog lingers behind any morning activity.

Frederick County: Comfortable tonight, low near 68°, partly cloudy and dry (only 12% precip). Thursday’s a different story: high near 83° with showers and thunderstorms likely (79%) — this is one of the better-positioned counties to see a strong cell given the I-95-adjacent instability axis nosing this way.

Carroll County: Shares Frederick’s numbers almost exactly — low near 68° tonight under partly cloudy skies, then a high in the low-to-mid 80s Thursday with a 79% chance of showers and thunderstorms, some possibly strong.

Baltimore Metro

Baltimore City & County: A genuinely nice night — low near 73°, partly cloudy, winds light out of the west, only a 5% chance of a stray shower. Thursday turns active fast: high near 86°, and this is squarely in the slight-risk zone for severe weather, with a 79% chance of showers and thunderstorms that could include damaging gusts, large hail, and even a brief tornado risk during peak afternoon heating.

Harford County: Tracks with the Baltimore metro grid — low around 73° tonight, high near 86° Thursday, same severe-weather concern given its I-95 corridor location.

Howard County: Same story — comfortable, dry tonight near 73°, then Thursday’s high mid-80s with a strong-to-severe storm threat by afternoon into evening.

Anne Arundel County: Low near 73° tonight, clear-to-partly-cloudy. Thursday’s high around 86° with the severe threat fully in play along the western shore of the Bay — this county sits right in the highest-confidence zone SPC has flagged.

DC Suburbs

Montgomery County: Low near 71° tonight, partly cloudy, quiet. Thursday’s high around 85° with showers and thunderstorms likely (74%) — some could turn strong given the proximity to the I-95 severe corridor.

Prince George’s County: Nearly identical — low near 71°, calm tonight, then a high near 85° Thursday with a 74% chance of showers and storms, damaging wind and hail the primary concerns.

Southern Maryland

Charles, Calvert & St. Mary’s Counties: A pleasant, mostly clear night with lows near 72°. Thursday starts mostly sunny before showers and thunderstorms move in by afternoon (67% chance), high near 87°. This region also carries the flash-flooding footnote — PWATs nearing 2 inches mean any slow-moving cell could produce locally heavy downpours, though storm motion should keep flooding limited to the usual poor-drainage spots.

Upper Eastern Shore

Cecil, Kent, Queen Anne’s, Talbot & Caroline Counties: Mostly clear and comfortable tonight, low near 72°. Thursday’s high near 86° with showers and storms increasing through the day (60% during the day, climbing to 86% Thursday night) — Cecil County in particular sits close enough to the I-95 severe zone to watch closely, while the rest of the upper shore sees the bulk of its heavier rain arrive Thursday evening into the overnight.

Lower Eastern Shore

Dorchester, Wicomico & Somerset Counties: Mostly clear tonight, low near 71°. Thursday’s high near 88° — the warmest reading on the board — with a 73% chance of showers and thunderstorms, mainly afternoon into evening, and a continuing chance overnight into Friday.

Ocean City & the Coast

Worcester County / Ocean City: Mostly clear and mild tonight, low near 74°, light south wind around 7 mph. Thursday stays mostly sunny until around 5 PM before clouds thicken and showers/thunderstorms become likely (66%), high near 84°. Surf holds around 2 feet with a low rip current risk, water temps in the upper 70s. Tides at the Ocean City Fishing Pier: low tide 7:42 AM, high tide 2:13 PM. Southwest winds around 5 mph in the morning build to south around 15 mph by afternoon as the front approaches.

Active Hazards

As of this evening, there are no active watches, warnings, or advisories for Maryland. That said, keep an eye out overnight and into Thursday — LWX has issued a Small Craft Advisory for the southern Chesapeake Bay Thursday afternoon as southerly winds gust near 20 knots, and neighboring PHI has posted a Flash Flood Watch for southeast PA, northern Delaware, and New Jersey from noon Thursday through 2 AM Friday — worth watching in case coverage nudges toward Cecil County or the upper shore as guidance updates overnight.

Severe & Flooding Threat — Thursday

SPC has placed a slight risk (2 of 5) for severe weather across the I-95 corridor and points east, including Baltimore, Harford, Howard, Anne Arundel, Montgomery, and Prince George’s counties, with effective shear nearing 40 knots and CAPE around 2,000 J/kg — enough for discrete storms to organize into a line as they track east Thursday afternoon into early evening. Damaging wind gusts and large hail are the top concerns, with a brief tornado not ruled out. Confidence is highest along and east of I-95. Separately, precipitable water values nearing 2 inches raise an isolated flash flooding concern statewide, though generally progressive storm motion should limit that risk to poor-drainage and flood-prone spots rather than widespread issues.

Humidity, Winds & the Bay

Tonight is the payoff from today’s dry push — noticeably lower humidity statewide, genuinely comfortable sleeping weather from the mountains to the shore. That changes fast Thursday as moisture surges back in ahead of the front. Winds stay light and variable tonight (mostly under 10 mph), then increase Thursday, especially near the Bay, where southerly gusts near 20 knots prompt the Small Craft Advisory for the southern Chesapeake Bay Thursday afternoon. Boaters on the Bay and tidal Potomac should watch for that advisory window and the possibility of sudden marine thunderstorm warnings as storms cross the water Thursday afternoon.

Tonight’s Lows by Zone

Zone	Overnight Low
Western Mountains (Garrett)	Around 61°
Cumberland/Allegany	Around 65°
Hagerstown/Frederick/Carroll	Upper 60s (67°–68°)
Baltimore/DC Corridor	Low 70s (71°–73°)
Southern Maryland	Around 72°
Eastern Shore (Upper & Lower)	Low 70s (71°–72°)
Ocean City	Around 74°

Looking Ahead

Thursday is the headline day — widespread showers and thunderstorms statewide, with the severe and heavy-rain threat concentrated along and east of I-95 during the afternoon and evening. Friday brings a break in intensity but not in moisture — chances of showers and storms linger, especially by afternoon and overnight, as the front stalls nearby. Then Saturday looks like the more unstable of the weekend days as a second wave of energy digs through, followed by lingering Sunday showers before a cooler, drier, more autumn-like pattern settles in to start next week.

Data: NWS Baltimore/Washington, Mount Holly & Wakefield.

MD Weather Alerts — your director’s-cut forecast, every corner of the state, every time. Stay dry out there tomorrow.