If you’re planning for St. Patrick’s Day in Washington, you’ll want to get ready for weather that bounces between chilly mornings and surprisingly mild afternoons. Most years, temperatures in Seattle dip into the low 40s°F at night and reach the mid-50s°F during the day. Inland cities like Spokane usually start off colder but can warm up to the upper 40s°F or low 50s°F. Rain? It’s a regular visitor in western Washington, but if you’re headed east of the Cascades, things tend to stay drier.
You might catch a parade under gray, drizzly skies in Seattle, or find yourself strolling through Spokane with crisp sunshine and cool air. The state’s terrain is a real patchwork—coastal spots, mountain valleys—so the weather can feel totally different depending on where you are.
It helps to know what you’re up against. Will you need a warm coat, an umbrella, or just a light jacket? Looking at typical weather, local quirks, and what’s happened in the past can help you make the most of St. Patrick’s Day across Washington.
Typical Weather Conditions on St. Patrick’s Day
When you’re making plans for St. Patrick’s Day in Washington, expect mild daytime highs, cool nights, and a decent shot at rain. Things can change fast, so knowing the usual temps, rainfall, and wind patterns gives you a leg up if you’re heading outside or traveling.
Average Temperatures in March
Around March 17, Washington’s temperatures usually land somewhere between the upper 30s °F at night and the mid-50s °F during the day. Some years, mornings dip into the low 30s, while afternoons can surprise you by climbing into the 60s.
The National Weather Service points out that there’s always a chance for extremes. Records show highs have hit the upper 70s in rare years, while the coldest St. Patrick’s Days barely creep above freezing.
If you’re headed to a parade or festival, dress in layers. You’ll probably want a light jacket or sweater early on, but by afternoon, lighter clothes might do the trick. That swing is just part of mid-March weather here.
Precipitation Trends and Rainfall
Rain tends to show up on St. Patrick’s Day in Washington. Data says you’ll see light rain or scattered showers about a third of the time. Snow is pretty rare, but it has happened in chillier years.
Average rainfall in mid-March doesn’t usually top half an inch on the holiday itself. Still, if a system rolls through, things get damp fast. Local weather forecasts often call for short bursts of rain in the afternoon or evening.
A compact umbrella or rain jacket is your friend. Even if it starts dry, March weather here can flip, and showers often pop up later in the day.
Wind and Humidity Levels
Mid-March winds usually stay light to moderate—think 8–15 mph. Breezes from the west or northwest can make things feel colder when temps drop. Sometimes, a cold front brings stronger gusts, but that’s not the norm.
Humidity in March hangs around 40% to 60%. That can make mornings feel brisk, but by midday, it’s usually pretty comfortable.
If you’re outside for a while, expect a mix of cool breezes and mild humidity. That’s just early spring in Washington, and it rarely messes up holiday plans.
Regional Weather Differences Across Washington
St. Patrick’s Day weather changes a lot depending on where you are in Washington. The Cascade Range splits the state, so what you get in Seattle feels nothing like Spokane or other eastern towns.
Seattle and Western Washington
Seattle and the rest of western Washington usually feel damp and cool in March. Highs hit the low to mid-50s °F, lows stick in the 40s °F. Rain shows up a lot, with light showers on many days. Snow almost never makes it to the lowlands, though the mountain passes can still get dumped on.
Clouds are the norm, so don’t count on much sun. The air near Puget Sound stays mild since the Pacific keeps temps steady. That makes western Washington a bit more predictable, with fewer wild swings in daily temps.
If you’re heading outside, plan for wet ground and occasional breezes. Parks and trails might be muddy, but spring flowers often peek out by mid-March. A light rain jacket and waterproof shoes beat heavy winter gear here.
Eastern Washington Climate Variations
Eastern Washington is a whole different story. The Cascades block much of the rain, so things stay drier. Cities like Spokane and the Tri-Cities get far less precipitation than Seattle. In mid-March, highs usually land in the upper 40s to mid-50s °F, while nights often drop below freezing.
Snow sticks around longer here, especially in Spokane and the higher valleys. By mid-March, snow cover is patchy, but frosty mornings are still pretty common. Rainfall is lighter than out west, and when it does rain, it’s usually a quick shower, not a steady drizzle.
The dry air means bigger swings between day and night temps. Outdoor conditions feel crisper and sunnier, but winds can make it feel colder. If you’re visiting eastern Washington in March, bring layers for chilly mornings and milder afternoons.
Historical Weather Patterns for St. Patrick’s Day
Washington’s weather around St. Patrick’s Day has swung from spring-like afternoons to cold, rainy, or even snowy mornings. The National Weather Service has plenty of records showing how wild March can get.
Record Highs and Lows
March 17 temperatures in Washington have run the gamut. Some years, highs soar into the upper 70s—79°F in 1894 holds the record. Those warm days are rare, but they do pop up when high pressure sets in.
On the flip side, lows have plunged into the 20s. The record coldest St. Patrick’s Day was about 9°F in 1900, according to long-term records. Those extreme lows usually show up when clear skies and Arctic air hit.
Most years, things fall in the middle. Typical highs hit the 50s, lows hang around the 30s to low 40s. So, you’ll probably want a jacket in the morning and lighter layers by the afternoon.
Notable Weather Events
Some St. Patrick’s Days have brought weird weather to Washington. In 1965, heavy snow fell in parts of the region, with over 10 inches reported farther north in the Midwest. Washington doesn’t usually see snow that late, but trace amounts have shown up on March 17.
Rain is more the norm. The wettest St. Patrick’s Day on record brought over 1.7 inches of rain in 1898, according to National Weather Service archives. When Pacific storms get active, you might end up with steady showers or a soggy parade.
Wind sometimes gets into the mix. Early spring storms can whip up gusty conditions, making it feel colder than it really is. March weather can be all over the place.
Trends Over Recent Years
In the last decade, afternoons have seemed milder than in past records. Many recent St. Patrick’s Days have had highs in the 50s and 60s, and there have been fewer super-cold mornings. This fits with broader March trends showing warmer averages across the region.
Rainfall jumps around from year to year. Some years bring just light showers, while others see measurable rain. Snow on March 17 is almost unheard of now, with only traces reported lately.
You’re more likely to see variety than consistency. If you’re planning outdoor events, be ready for cool mornings and a shot at rain later.
Weather Influences and Atmospheric Conditions
March weather in Washington can turn on a dime because of shifting air patterns and all that varied terrain. The tug-of-war between Pacific systems and the mountains shapes what you’ll get around St. Patrick’s Day.
Role of High Pressure Systems
When a high pressure system parks over the Pacific Northwest in mid-March, you usually get calmer, drier weather. Clear skies show up, and temperatures often climb above the seasonal average. In western Washington, this can mean highs in the 50s or even low 60s.
High pressure also clears out clouds, which means cooler nights. Lows can drop near or below 40°F, especially away from cities. That kind of setup often brings big swings between day and night temps.
These systems block storms from the Pacific, so you see fewer rain showers and more steady conditions. But if high pressure lingers, it can trap pollutants, making air quality worse in valleys like Puget Sound.
High pressure doesn’t always stick around. When it breaks, storm fronts can roll in with rain and cooler weather, just to remind you that spring is still a work in progress.
Rain Shadow Effect and Mountain Impact
The Cascade Range really shapes March weather. Moist Pacific air climbs the mountains, dropping heavy rain or snow on the west slopes. Seattle and Olympia often get steady rain during this stretch.
Once that air crosses the Cascades, it dries out. This sets up a rain shadow effect for central and eastern Washington. Towns like Yakima and Wenatchee usually see much less rain around St. Patrick’s Day than the west side.
Snow can still fall in higher elevations during March. Cascade ski resorts often get late-season snowstorms, while lower valleys stay pretty dry.
This mountain wall also affects temperatures. Western Washington stays mild and damp, while eastern areas get cooler nights and sunnier afternoons. The difference can be pretty dramatic if you drive across the state in a day.
Severe Weather Possibilities
Around mid-March, Washington’s weather can flip quickly. Some years, you’ll get calm days, but sometimes stronger systems roll in with hail, thunderstorms, or localized flooding. Keeping an eye on these patterns helps you plan for safer travel and outdoor fun.
Chance of Hail and Storms
Thunderstorms don’t show up as often in March as in summer, but they do happen. When they do, you might see small hail and quick downpours. These storms usually pop up in the afternoon or evening when cold air moves over wet ground.
The National Weather Service (NWS) sends out alerts if hail or lightning are likely. It’s smart to check those, especially if you’re driving east of the Cascades. Roads can get slick, and visibility can drop in a hurry.
Hail in western Washington is usually pea-sized and over fast, but in eastern Washington, bigger hailstones happen a bit more often. They’re rare, but they can dent cars or damage crops. If you’re caught outside in hail, find shelter right away.
Flooding and Localized Hazards
Heavy rain is more common than hail this time of year. Rivers and streams often run high from melting mountain snow mixed with spring rain. Low-lying spots, especially near the Snoqualmie, Skagit, and Chehalis Rivers, sometimes see minor flooding.
Flooding can also pop up in cities. Storm drains clog with early spring debris, causing quick street floods. That can slow down travel or mess with parade routes.
The NWS issues flood watches and warnings when water levels get risky. It’s worth checking before you head out, especially near rivers or mountain passes. Even shallow floodwaters can be dangerous to walk or drive through.
Planning for St. Patrick’s Day Activities
Washington’s weather around St. Patrick’s Day jumps between mild afternoons and cooler evenings. Light rain is pretty normal, so staying ready for changing conditions will keep you comfortable at parades, fun runs, or outdoor get-togethers.
What to Wear and Pack
Daytime highs usually hang out in the mid to upper 50s °F (12–16°C). Nights get much cooler, dipping into the 40s °F (4–8°C).
Layering really works best here, since the temperature can drop fast once the sun goes down.
Grab a light waterproof jacket or just toss a compact umbrella into your bag in case you run into scattered showers.
You’ll want comfortable shoes that can handle damp streets, especially if you’re planning to walk around or stand for a while during parades.
If you’re sticking around outside after dark, don’t forget a warm layer—maybe a fleece or a sweater.
Gloves and a hat might come in handy too if it gets windy.
A small crossbody bag or a backpack keeps your hands free and makes it easier to carry things like water, snacks, and rain gear without feeling weighed down.
Outdoor Event Considerations
Parades and festivals usually fill up crowded streets fast, so expect limited seating. You’ll probably spend a lot of time standing, so keep that in mind.
It’s always a good idea to check the weather forecast the day before. That way, you’ll know if you need to grab some rain gear or just slap on some extra sunblock.
If it’s sunny, don’t forget your sunglasses and sunscreen. March might not seem that bright, but UV rays can still sneak up on you.
Cool or cloudy? Focus on staying warm and dry instead.
You’ll probably run into wet ground, so skip shoes with thin soles. Waterproof or sturdy shoes just make life easier out there.
St. Patrick’s Day events can mess with transportation since road closures are common. Try to arrive early, and maybe just take public transit if parking looks impossible near the parade or festival spots.