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San Mar, Maryland

Community in Washington County, Maryland

Air quality

The air at San Mar

Index 15, good, led by ozone. Read at 1 AM from its reporting area, Hagerstown Region (MD), 15 miles off.

15Good
  • Fine particles (PM2.5)9Good4 mi
  • Ozone15Good15 ppb4 mi

The days ahead

Good each day through Sun Oct 18, led by fine particles. Yesterday measured 15, good.

Smoke, the next 43 hours

Little smoke near the ground through Sat 8 PM: the index from smoke stays at 6 or under.

FriSat

Precipitation

What has fallen at San Mar

0.13 in in the last 24 hours, and none in the 2 days before, to Fri 1 AM. Measured by radar and rain gauges, as water.

Last 24 hours
0.13in
Last 3 days
0.13in

Visibility

How far you can see at San Mar, the next 43 hours

Mist or haze: visibility falls to 2 miles Fri 6 PM.

FriSat

On the radar over San Mar, MarylandReflectivityStorm topsRain rateRain, last 24 hoursForecast temperatureForecast rain totalEvery picture

What is measuring near here

The 6 instruments nearest San Mar, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 2.2 miles away.

measured now4 instruments

Camp DavidRSP

At an airfield/11.5 mi away/1,841 ft/1,273 ft above here

temp, wind, gust, visibility, precip, pressure

Rank709of 736

measured daily2 instruments

Boonsboro 0.4 NNEMD-WH-17

In a volunteer observer's own ground/2.4 mi away/556 ft/12 ft below here

precip, snowfall, snow depth

Rank-

Hagerstown 1EHGCM2

At a cooperative observer's station/6.9 mi away/541 ft/27 ft below here

snowfall, snow depth, precip, high, low

Rank346of 736

Station report

The weather at I-70 at Frederick / Wash. Co line, drawn

The nearest instrument reporting now, 2.2 mi from San Mar, Maryland. From its report of Oct 16, 2026, 1:39 AM local time: 3 of its 5 sheets.

The air

56.7 F with a dew point of 56.7 F, 100 per cent relative humidity. The air is saturated at the ground.

Chart of the air at I-70 at Frederick / Wash. Co line: temperature 56.7 degrees Fahrenheit and dew point 56.7, 100 per cent relative humidity; the air saturated at the ground; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT MD015FIG. B THE AIR AT I-70 AT FREDERICK / WASH. CO LINETHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION01,0002,0003,00050 F60 F70 FSATURATED AT THE GROUNDTEMPERATURE AND DEW POINT 56.7 F, 56.7 FRELATIVE HUMIDITY 100 PER CENTTHE AIR COOLS ABOUT 5.4 F EACH 1,000 FT IT RISES, AND ITS DEW POINT ABOUT 1 FSOLID: THE LIFTED AIR'S TEMPERATURE; DASHED: ITS DEW POINTTITLEI-70 at Frederick / Wash. Co line, the airSTATION REPORT · RWIS MD015TYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 5DATE2026-10-16IDSR-MD015-1DRAWN AS linework on paperSOURCES FB-WAT-020, FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the southeast (132 degrees) at 4 mph, gusting 12 mph: force 2, a light breeze on the Beaufort scale. The strongest gust today was 16 mph.

Plan of the wind at I-70 at Frederick / Wash. Co line, north up: blowing from 132 degrees, the southeast, at 4 miles an hour, gusting 12; beside it the Beaufort scale from calm to hurricane force, force 2, light breeze, marked.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT MD015FIG. C THE WIND AT I-70 AT FREDERICK / WASH. CO LINEPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 132°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR12LIGHT BREEZE4NOW, 4 MPH3GENTLE BREEZE8GUST, 12 MPH4MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLEI-70 at Frederick / Wash. Co line, the windSTATION REPORT · RWIS MD015TYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 2 of 5DATE2026-10-16IDSR-MD015-2DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008

The column

At 1,202 ft above sea level, 4 per cent of the atmosphere's air lies below the station. The standard atmosphere puts the pressure there at 28.64 inHg and the temperature at 54.7 F; it reports 56.7 F, 1.9 F warmer than standard.

Section from sea level of where I-70 at Frederick / Wash. Co line stands in the atmosphere, height to scale: the station 1,202 feet above sea level with 4 per cent of the air below it; the standard atmosphere's pressure there, 28.64 inches of mercury, and temperature, 54.7 degrees Fahrenheit.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT MD015FIG. D WHERE I-70 AT FREDERICK / WASH. CO LINE STANDS IN THE ATMOSPHERESECTION FROM SEA LEVEL, HEIGHT TO SCALE, THE STATION IN THE STANDARD ATMOSPHEREFT ABOVE SEA LEVEL05,00010,00015,000SEA LEVEL, 29.92 inHg IN THE STANDARD ATMOSPHEREI-70 AT FREDERICK / WASH. CO LINE4 PER CENT OF THE AIR BELOW IT1,202 FT10 PER CENT OF THE AIR BELOW, 2,890 FT20 PER CENT OF THE AIR BELOW, 6,050 FT30 PER CENT OF THE AIR BELOW, 9,540 FT40 PER CENT OF THE AIR BELOW, 13,470 FTSTANDARD PRESSURE HERE28.64 inHgSTANDARD TEMPERATURE HERE54.7 FTEMPERATURE, REPORTED56.7 FTITLEI-70 at Frederick / Wash. Co line, the columnSTATION REPORT · RWIS MD015TYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 3 of 5DATE2026-10-16IDSR-MD015-3DRAWN AS linework on paperSOURCES FB-ENG-001, FB-ENG-003

The full report of I-70 at Frederick / Wash. Co line, in 5 sheets, each beside the Field Book plates that explain it

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Snow on the ground

Elsewhere in Maryland

21 places, each with its own forecast and its own instruments.

Near San Mar

The nearest places, each with its own forecast and the instruments nearest it.

Near San Mar

River and lake gauges