❄ YourSnowCalculator

Free · All 50 States · Updated for Winter 2026

Snow Day Predictor, Snowfall Converter & Roof Snow Load Calculator

Three tools in one: estimate the odds your school or district closes for snow, convert snowfall between inches, centimeters, and liquid water equivalent, and check whether your roof is carrying a dangerous snow load — all calibrated by U.S. state and region.

State / Region

Forecast Snowfall (inches)

Forecast Low Temp (°F)

Storm Timing

Snowfall Amount

Unit

Snow Type (density)

Snow Depth on Roof (inches)

Snow Condition

Region Building Code (ground snow load)

Snow Day Calculator Guide

How Snow Day Predictions Actually Work

Every winter, millions of parents and students across the United States refresh school district websites and local news apps hoping to see the words "closed" or "two-hour delay." A snow day calculator can't replace that official announcement, but it can give you a realistic, data-informed estimate of the odds — using the same core factors that superintendents themselves weigh when they make the call, usually between 4:00 and 5:30 a.m. on the day of a storm.

The main inputs that matter are forecast snowfall total, the timing of the storm relative to the morning bus routes, road temperature (not just air temperature — a 34°F day with wet roads can be more dangerous than a 15°F day with dry roads), and — critically — regional norms. This is where geography matters most: a forecast of 3 inches means something completely different in Buffalo, New York than it does in Atlanta, Georgia.

Why the Same Snowfall Closes Some Schools and Not Others

Districts in the Snow Belt states maintain large fleets of plows, pre-treat roads with brine before storms even arrive, and have bus drivers experienced in winter conditions, so they can often stay open through storms that would shut down an entire state further south. Districts in snow-rare regions frequently don't own a single snowplow, and a forecast of even an inch of accumulation — especially if it coincides with black ice on rural roads — is enough to cancel classes preemptively the night before.

Typical snowfall thresholds that trigger school closures by region
Region Type	Typical Closure Threshold	Example States
Snow Belt	6–10+ inches, or dangerous wind chill	Minnesota, Vermont, Maine, N. New York, N. Michigan
Northern / Midwest	3–6 inches, or ice accumulation	Illinois, Ohio, Pennsylvania, Massachusetts, Iowa
Transitional	1–3 inches, especially with ice	Virginia, Kentucky, Missouri, Kansas, Colorado Front Range
Snow-Rare South	Under 1 inch, or forecast alone	Georgia, North Carolina, Tennessee, Texas, Louisiana

Snowfall Conversion: Inches, Centimeters, and Water Equivalent

Weather reports mix units constantly — American broadcasts use inches, international and scientific sources use centimeters or millimeters, and hydrologists use snow water equivalent (SWE) to describe how much liquid water a snowpack actually contains. The snowfall converter above handles all three, and it accounts for snow density, which is the detail most simple unit converters get wrong. One inch of light, dry powder in Minnesota in January might contain a tenth of the water that one inch of heavy, wet spring snow in the Mid-Atlantic contains.

Roof Snow Load: When Does Snow Become Dangerous?

Roof collapses from snow load are a genuine, recurring risk every winter, particularly for flat or low-slope roofs, older barns and outbuildings, and structures that have already accumulated multiple storms without melting or shedding snow between them. Building codes assign every region a "ground snow load" design value in pounds per square foot (psf), and structural engineers use that value, along with roof geometry, to determine how much a roof should be able to bear. The calculator above gives a rough estimate of current load versus typical design capacity — it is not a substitute for a professional structural inspection, especially on older buildings, flat roofs, or after several storms have piled up without a thaw.

Geo Data

Snow Day Calculator by State: Regional Snow Patterns

Snow day likelihood, average annual snowfall, and typical school-closure culture vary dramatically across the country. The table below covers all 50 states with approximate statewide average annual snowfall and typical closure tendency — use it alongside the calculator above to sanity-check your result. State-wide averages can understate reality in mountain and lake-effect zones, and overstate it in southern coastal areas.

Average annual snowfall and school closure tendency by U.S. state
State	Approx. Avg. Annual Snowfall	School Closure Tendency
Alabama	~1 in	Very low — ice, not snow depth, drives closures
Alaska	~80 in (statewide varies widely)	Very high — extreme cold and darkness matter more than depth
Arizona	~1 in lowlands, 100+ in at elevation	Very low in valleys; high near ski regions
Arkansas	~5 in	Low — ice storms are the main trigger
California	~1 in coastal, 400+ in Sierra	Very low statewide; extreme tolerance at Sierra elevation
Colorado	~67 in statewide	Moderate on Front Range; high in mountain districts
Connecticut	~36 in	Moderate — nor'easters are the main driver
Delaware	~14 in	Low-moderate
Florida	~0 in	Not applicable — closures don't occur for snow
Georgia	~1 in	Very low — even 1 inch can close schools statewide
Hawaii	~0 in (summit only)	Not applicable
Idaho	~35 in	Moderate-high, especially rural districts
Illinois	~19 in (much higher north)	Moderate — 4+ inches or ice typically needed
Indiana	~24 in	Moderate; rural districts close more readily
Iowa	~30 in	Moderate — wind/drifting matter as much as totals
Kansas	~15 in	Low-moderate — wind-driven snow and rural roads matter
Kentucky	~13 in	Low — hilly terrain and ice are key factors
Louisiana	<1 in	Very low — rare events close schools statewide
Maine	~65 in	High — rural bus routes are the limiting factor
Maryland	~15 in	Low-moderate
Massachusetts	~40 in	Moderate — nor'easters are the main closure driver
Michigan	~55 in (much higher in the north/UP)	High — lake-effect snow is routine
Minnesota	~50 in	High — wind chill often matters more than snowfall
Mississippi	~1 in	Very low
Missouri	~15 in	Low — ice storms close schools more than snow
Montana	~45 in	Moderate-high; rural distances are a major factor
Nebraska	~25 in	Moderate
Nevada	~15 in statewide, much higher at Tahoe elevation	Low in Las Vegas area; high near Sierra
New Hampshire	~60 in	High — well-equipped districts
New Jersey	~20 in	Moderate
New Mexico	~10 in statewide	Low in lowlands; higher near mountains
New York	~40 in statewide, 100+ in lake-effect belts	High upstate/lake-effect zones; moderate downstate
North Carolina	~5 in	Very low — forecast alone often triggers closure
North Dakota	~35 in	High — blowing snow/visibility is the main trigger
Ohio	~25 in	Moderate; varies significantly rural vs. urban
Oklahoma	~7 in	Low — ice is the primary concern
Oregon	~5 in valleys, much higher in Cascades	Low in Willamette Valley; high in mountain districts
Pennsylvania	~35 in	Moderate — hilly rural roads lower the threshold
Rhode Island	~30 in	Moderate
South Carolina	~1 in	Very low — minimal winter equipment
South Dakota	~35 in	Moderate-high; wind and drifting are key factors
Tennessee	~5 in	Very low — hilly roads amplify risk
Texas	<1 in statewide	Very low — infrastructure not built for ice/snow
Utah	~35 in valleys, 300+ in at ski elevations	Moderate in valleys; very high tolerance near resorts
Vermont	~70 in	High — closures mainly from ice or extreme cold
Virginia	~10 in	Low — ice is the biggest closure trigger
Washington	~5 in lowlands, 400+ in Cascades	Low in Seattle area despite rainy climate; high near mountain passes
West Virginia	~30 in	Moderate-high — mountainous rural roads
Wisconsin	~45 in	High — consistent plowing infrastructure
Wyoming	~40 in statewide, much higher in mountains	Moderate-high; wind is a major factor

Figures above are approximate statewide averages for general reference. Local conditions — elevation, lake-effect bands, and coastal vs. inland location — can cause dramatic variation within a single state.

Terminology

Snow & Winter Weather Glossary

Understanding the terms forecasters and school districts use makes it easier to interpret both the raw forecast and this calculator's output.

Snow water equivalent (SWE): the depth of liquid water contained in a layer of snow if it were fully melted. Used by hydrologists and engineers because raw snow depth alone doesn't indicate weight or runoff potential.
Ground snow load: a building-code design value, in pounds per square foot (psf), representing the maximum expected snow load on the ground in a given region over a defined return period (commonly 50 years).
Roof snow load: the actual load a roof structure is designed or expected to bear, typically calculated as a percentage of ground snow load adjusted for roof slope, exposure, and thermal factors.
Lake-effect snow: highly localized, often intense snowfall generated when cold air moves over relatively warmer lake water (most notably the Great Lakes), picking up moisture that is then dumped as snow on the downwind shore.
Snow density: the mass of snow per unit volume, commonly measured in pounds per cubic foot. Fresh powder is far less dense than wind-packed, wet, or partially melted and refrozen snow.
Two-hour delay: a partial closure where school start time is pushed back, typically to allow road crews more time to clear and treat roads, or to let morning temperatures rise before buses run.
Wind chill: the perceived temperature accounting for wind speed's cooling effect on exposed skin — a major factor in closure decisions independent of snowfall amount, especially in the Upper Midwest and Northern Plains.
Black ice: a thin, transparent layer of ice on pavement that is difficult to see and often more dangerous than visible snow accumulation, frequently the deciding factor in closures even with minimal snowfall.

How Closures Are Decided

Who Actually Decides School Closures, and How

School closure decisions in the U.S. are made locally, almost always by the superintendent of an individual school district, not by state or federal authorities. Superintendents typically wake in the early morning hours during an active or overnight storm — commonly between 4:00 and 5:00 a.m. — and personally assess road conditions, sometimes by driving key rural routes themselves, before making the call.

The decision draws on several inputs beyond the forecast itself: real-time reports from transportation directors and bus garage staff, road temperature readings from public works departments, staff and bus-driver availability, and increasingly, decisions already announced by neighboring districts, since large regional gaps in closures can create logistical and safety complications. Districts serving large rural areas with long bus routes on unpaved or hilly roads generally have a lower threshold for closing than urban and suburban districts with shorter, plowed routes — even within the same state.

Once the decision is made, districts typically notify families through automated call/text alert systems, their website and social media, and local TV and radio station "closings and delays" segments. This calculator estimates the odds behind that decision; it does not have access to a specific district's internal call.

Historical Context

Notable Snow Events and Records

Historical extremes help calibrate what "a lot of snow" really means. Some of the most significant U.S. snow events include the Great Blizzard of 1888, which paralyzed the Northeast with drifts over 40 feet in places; the Storm of the Century in March 1993, which dropped snow from the Gulf Coast to Maine in a single system; and recurring multi-day lake-effect events near Buffalo, New York, which have produced localized totals exceeding 6 feet within 48 hours.

On the roof-load side, some of the most damaging structural collapse events in U.S. history followed not single massive storms but a series of moderate snowfalls in quick succession without a thaw in between — a reminder that cumulative, undrained snow load can be more dangerous than any single storm's headline total. This is why the roof load calculator on this page asks for current total depth rather than just the most recent storm's snowfall.

Roof Safety

Roof Snow Load Reference by Building Code Region

Ground snow load design values are set by local building codes (based on ASCE 7 standards in the U.S.) and vary from as low as 10-20 psf in the Deep South to well over 100 psf in high-elevation mountain zones of Colorado, Utah, and the Sierra Nevada. Roof snow load is typically calculated as a fraction of ground load — often around 70% for a typical sloped residential roof, though flat roofs, valleys, and areas prone to drifting can see significantly higher local loads.

Region	Typical Ground Snow Load	Approx. Safe Fresh Snow Depth*
Southern / mild-winter states	~20 psf	~3–4 ft of fresh powder
Mid-latitude / Midwest & Northeast	~30 psf	~4–5 ft of fresh powder
Northern / mountain valley states	~50 psf	~7–8 ft of fresh powder
Extreme snow zones (high elevation)	80+ psf	11+ ft of fresh powder

*Estimates for fresh, light powder only. Wet or compacted snow reaches these load limits at a fraction of the depth — always use the roof calculator above with your actual snow condition, and consult a structural engineer for any roof showing sagging, creaking, or cracking.

FAQ

Frequently Asked Questions

How accurate is a snow day calculator?

A snow day calculator gives a probability estimate based on forecast snowfall, temperature, timing, and your district's historical closure pattern. It is not official — only your school district or local government can confirm a closure, usually announced the night before or early morning of the storm via text alert, robocall, or website posting.

How much snow does it usually take to close schools?

It varies enormously by region. Snow Belt districts (northern Michigan, upstate New York, Minnesota, Vermont) may stay open through 6-8+ inches because they have equipment and experience. Districts in the South or areas unused to snow may close for 1-2 inches, or even just the forecast of snow, since they lack plows and salt trucks.

What is snow water equivalent (SWE) and why does it matter?

Snow water equivalent is the depth of liquid water you'd get if you melted a given layer of snow completely. It matters because snow density varies widely — a foot of light powder might hold half an inch of water, while a foot of wet, packed snow could hold two inches or more. SWE is the figure engineers and hydrologists actually rely on for roof-load and runoff calculations, not raw snow depth.

How much snow can a roof hold before it collapses?

Most U.S. residential roofs are built to a ground snow load of 20-50 psf depending on regional building code, which roughly translates to 2-4 feet of fresh powder or 8-12 inches of dense, wet snow. Roof pitch, snow density, drifting, and the building's age and design all affect the real number, so a calculator estimate should never replace a structural engineer's in-person assessment, especially for flat or older roofs.

Does wet snow weigh more than powdery snow?

Yes, significantly. Fresh powder can weigh as little as 3-5 lb per cubic foot, while wet, compacted, or rain-soaked snow can weigh 15-20+ lb per cubic foot — four to six times heavier for the same depth. That's why a "light" 12-inch snowfall and a "heavy, wet" 12-inch snowfall put very different loads on the same roof.

How do I convert inches of snow to inches of rain?

The commonly cited rule of thumb is a 10:1 ratio — 10 inches of average snow melts to roughly 1 inch of rain. In reality, the ratio ranges from about 5:1 for wet, heavy snow up to 20:1 or more for very dry powder in extreme cold, so 10:1 is only a rough average, not a fixed conversion.

Which U.S. states get the most snow?

By average annual snowfall, the snowiest states are typically Alaska, Vermont, Maine, New Hampshire, and Great Lakes-adjacent areas of New York and Michigan due to lake-effect snow. Mountain regions in Colorado, Utah, and California's Sierra Nevada also get extremely heavy snowfall at elevation, even though state-wide averages there are lower because of lower-elevation deserts and valleys.

Do two-hour delays count differently than full snow days in this calculator?

The calculator above estimates overall closure likelihood rather than distinguishing delays from full closures, since districts weigh that decision differently. Generally, marginal snow-day conditions (light accumulation, improving conditions by mid-morning) push districts toward a delay rather than a full closure, while heavy overnight snowfall or dangerous morning temperatures push toward a full closure.

Why did my school close for less snow than a calculator predicted?

Superintendents weigh factors a calculator can't see: staff availability, bus driver call-offs, specific rural road conditions, ice underneath the snow, and even neighboring district decisions. Calculators are a helpful estimate, not a guarantee, precisely because these hyper-local, day-of factors can outweigh the raw snowfall number.

What time do schools usually announce snow day closures?

Most U.S. districts announce overnight-storm closures between 4:00 and 6:00 a.m., after transportation staff and administrators have assessed real road conditions. For storms arriving during the school day, districts may announce early dismissal several hours in advance to get students home before roads deteriorate.

Does a snow day get made up later in the school year?

In most U.S. states, yes — districts are required to meet a minimum number of instructional days or hours, so snow days are typically made up by extending the school year in June, converting a scheduled break day, or using built-in "bank" days already reserved in the calendar for weather. Some states have relaxed this requirement in recent years by allowing remote learning days to count instead of an in-person make-up day.

What's the difference between a snow squall and a snowstorm?

A snow squall is a brief, intense burst of heavy snowfall and strong wind that dramatically reduces visibility for a short period — often 30 minutes or less — while a snowstorm or winter storm describes a longer-duration system that can last many hours to multiple days. Squalls can cause serious whiteout conditions and highway pile-ups despite producing relatively little total accumulation.

How is snow load measured on an existing roof?

There's no single instrument that measures roof load directly in a typical home; it's estimated from snow depth and density, which is why the calculator on this page asks for both. Professional structural assessments may involve a physical inspection for visible sagging, cracking sounds, doors or windows that suddenly stick, and — for flat commercial roofs — direct measurement of accumulated snow and ice at multiple points.

Can I safely remove snow from my roof myself?

Light, fresh snow can often be safely removed from ground level using a roof rake on single-story homes, but climbing onto a snow- or ice-covered roof is a leading cause of fall injuries every winter and should generally be avoided. For heavy accumulation, ice dams, or any roof showing signs of stress, hiring a professional snow removal service or structural engineer is the safer option.