Road Salt Nearly Doubled This Winter. Below 15°F It Barely Melts Ice Anyway

The coordinator of a regional buying group outside Pittsburgh put it plainly in September: the salt its member towns would spread this winter cost “almost twice as much” as last year’s, and it came from the only one of four major suppliers that bid. A month earlier, public works directors in northern Illinois learned that the state contract many of them buy through had drawn no bids for them at all. One, with fifteen years in the job, told a local paper: “I have never heard of this before.”

That is the news. This article adds the part the news leaves out. Even a town with a full dome has a chemistry problem every January: below a certain pavement temperature, rock salt barely melts ice, however much of it goes down. We set out the 2026–27 prices as reported, then the temperatures at which each common deicer stops working, why calcium chloride keeps going where salt stalls, and what the per-pound math says about where each one belongs. We take no side on why the bids failed; the reporting below does not settle it, and neither do we.

How much has road salt gone up for winter 2026–27?

Where it has been reported, by roughly half to three-quarters per ton, and in some places towns had to hunt for any bid at all. The figures below are what local governments said they paid or were offered, as published by WPXI in Pittsburgh on 22 September 2026 and by Shaw Local in Illinois on 15 September 2026. They are municipal contract prices for bulk rock salt, delivered, not retail bag prices.

On our arithmetic the Pittsburgh-area price rose 72%, from $88.32 to $152. McHenry’s two offers were 50% and 104% above its usual $80. The Munhall manager said the increase was “a $250,000 increase to our budget, which would be equivalent to our roads paving program.” The group’s coordinator summed it up in four words: “Sticker shock is real.”

Not every state is in the same position. Michigan’s cooperative purchasing program lists 2026–27 bulk rock salt pricing as good through August 2027, and a Peoria official told 25 News Now on 15 October that the city’s increase of roughly 30–40% per ton had been budgeted. The squeeze is real, uneven, and concentrated in the places that buy late or through a single pooled tender.

Why does rock salt stop working in the cold?

Because salt does not melt ice by itself. It has to dissolve first, in the thin film of liquid water that sits on ice, and the brine it makes is what melts more ice. The colder it gets, the less liquid water there is to start the process and the more slowly salt goes into solution. The University of Minnesota’s SmartWinterSalt guidance, written for property managers and homeowners, gives the working numbers: “Rock salt, for example, is effective down to about 15°F. Below 15°F, it will work very slowly and will not melt much ice, and below -6°F (the eutectic temperature), it will not work at all.”

The two temperatures in that quote are different things. The eutectic is a laboratory limit: the coldest point at which a salt-and-water brine can exist as a liquid at all, about −6°F (−21°C) for sodium chloride. The practical temperature is the one that matters on a sidewalk: the point below which the melting is too slow to be worth the material. SmartWinterSalt warns that some deicer labels quote the eutectic, “which is the lowest temperature they can melt ice under ideal, laboratory-type conditions—not what typically happens on your driveway or sidewalk.” When a bag says “melts to −25°F”, it is worth asking which of the two numbers that is.

Pavement temperature is the number that counts, not air temperature. A sunlit dark asphalt lot can sit well above the air at midday; a shaded concrete step at dawn can sit below it. Road crews read pavement sensors for this reason. For a facility manager the useful habit is simple: on mornings when the pavement is in the single digits, salt alone will not clear a walkway in any reasonable time.

Which deicers work at the lowest temperatures?

The chlorides of calcium and magnesium, and two non-chloride liquids used mostly at airports. The table gives the lowest practical melting temperature and the eutectic temperature for the common deicers, as published by the Minnesota Pollution Control Agency and the University of Minnesota’s SmartWinterSalt program. The calcium chloride producer OxyChem lists lower practical limits for its own products, and that column is shown separately so the two kinds of source are not mixed.

Two things stand out. Calcium chloride’s brine stays liquid some 54°F colder than salt brine at the eutectic, which is the real reason it keeps working when salt has stalled. And the sources disagree on magnesium chloride: the state agency puts it at −10°F, while the calcium chloride producer puts it at 0°F. A producer comparing itself with a competitor has an interest, so we show both rather than pick one.

Both the MPCA and SmartWinterSalt also note that most bagged blends are mostly rock salt, because it is the cheapest ingredient, with some calcium or magnesium chloride added. More of the chloride lowers the working temperature. If a blend does not state its composition, its working temperature is a guess.

Why does calcium chloride get hot on ice?

Because dissolving it releases heat. Many salts take a little heat from their surroundings when they dissolve; sodium chloride takes a small amount, which is one reason it starts slowly on cold ice. Anhydrous calcium chloride does the opposite and gives off a large amount of heat as its ions are surrounded by water. On ice, that heat speeds up the dissolving, which makes more brine, which melts more ice. Calcium chloride also pulls moisture out of the air, so it can start making its own brine on a dry, frozen surface where salt would sit as dry grit.

The size of the effect depends on how much water is already locked in the crystal. OxyChem’s September 2026 white paper gives heats of solution, citing Perry’s Chemical Engineers’ Handbook, with a negative sign meaning heat is released:

On our arithmetic, anhydrous calcium chloride releases about ten times the heat of magnesium chloride hexahydrate on the same basis (317.2 ÷ 30.0 ≈ 10.6). The hexahydrate has six water molecules already bound to each magnesium ion, so most of the hydration energy was spent when the crystal formed. The same white paper notes that commercial calcium chloride pellets run above 90% calcium chloride and flake typically about 83%, while a solid magnesium chloride product contains at most 52%. The rest is water you are paying to ship and spread.

Does calcium chloride have more ions than salt?

Per formula unit, yes; per pound, no, and that turns out to matter. A unit of calcium chloride breaks into three ions (one Ca²⁺ and two Cl⁻) and a unit of salt into two. Freezing-point depression depends on the number of dissolved particles, so this is often given as the reason calcium chloride works better. But calcium chloride is a heavier compound, 110.98 g/mol against 58.44 g/mol for sodium chloride. On our arithmetic, a pound of sodium chloride puts about 15.5 moles of ions into solution and a pound of anhydrous calcium chloride about 12.3. Pound for pound, salt makes about 27% more particles.

So where it is warm enough for salt to work well, salt is not a weak deicer; it is an efficient and cheap one. Calcium chloride’s advantage is not the ion count. It is the three properties covered above: its brine stays liquid to a far lower temperature, it releases heat as it dissolves, and it draws in moisture to start the process on dry ice. All three matter most exactly when salt is failing.

What this means on a specification

Price per ton is the wrong comparison on its own. Calcium chloride costs many times more per ton than municipal road salt, at any of the prices reported this year, and nobody should plan to spread it on a whole road network. The useful comparison is the cost of clearing a specific surface at a specific temperature. OxyChem’s white paper gives an application rate for undercutting a thin sheet of ice at 20°F with a 92% calcium chloride pellet. The right-hand figures are our arithmetic from that rate.

Three caveats. The rates are for a pellet above 90% calcium chloride; a flake at about 83% needs proportionally more, so check the assay on the product you buy. Thicker ice and colder pavement need more. And every source here, including the producer, says the cheapest pound of deicer is the one you do not use: OxyChem’s paper says “Mechanical removal is the most economical and lowest impact method of snow and ice control,” and the state guidance says the same. Plow or shovel first, then treat what is bonded to the pavement.

Read that way, the salt shortage and the cold limit point the same direction. A facility that has less rock salt this winter can stretch it by keeping it for the days it works, and holding a smaller quantity of calcium chloride for the steps, ramps, loading docks and entrances on the coldest mornings, where salt would sit unmelted. The state guidance lists every chloride deicer, calcium chloride included, as corrosive, which is another argument for using the least that does the job.

About supply. This article reports road-salt prices that municipalities paid or were offered, as published by local news outlets. Alliance Chemical does not sell bulk road salt. The article makes no claim about ours: it does not say how these conditions touch the supply or price of the calcium chloride or magnesium chloride we list, where that material is made, or what it will cost later in the season. Prices are on the product pages and change with pack size.

Common questions

Why is road salt so expensive for winter 2026–27?

Municipal bids drew few or no offers in several regions. A Pittsburgh-area buying group got one bid from four major suppliers, at $152 a ton against $88.32 last season, and many of the more than 250 Illinois municipal agencies in the state program came away without a contract after Cargill did not bid. The reporting does not give a single cause.

At what temperature does rock salt stop working?

The University of Minnesota’s SmartWinterSalt guidance says rock salt is effective down to about 15°F pavement temperature, works very slowly below that, and does not work at all below about −6°F, its eutectic temperature. Pavement temperature, not air temperature, is what counts.

Is calcium chloride better than rock salt?

Below about 15°F, yes. Calcium chloride is listed at −20°F by the Minnesota Pollution Control Agency, releases heat as it dissolves and draws in moisture to start melting. Above that temperature, salt is cheaper per pound of ice melted in most cases. Calcium chloride costs many times more per ton.

Why does calcium chloride get warm when it dissolves?

Dissolving anhydrous calcium chloride releases heat as water molecules bind to its ions. OxyChem lists its heat of solution at −317.2 on the same basis as −30.0 for magnesium chloride hexahydrate, about ten times larger on our arithmetic. Forms that already contain water release less.

How much calcium chloride do I need for a sidewalk?

OxyChem gives 28 lb per 1,000 square feet to undercut a thin sheet of ice at 20°F with a 92% pellet. On our arithmetic, a 50 lb bag covers about 1,786 square feet in one pass. Thicker ice, colder pavement or a lower-assay flake need more. Remove snow mechanically first.

Is magnesium chloride the same as calcium chloride for deicing?

No. Magnesium chloride is usually sold as a hexahydrate that is at most about 52% magnesium chloride, releases far less heat, and is listed at −10°F by the MPCA and 0°F by OxyChem. Calcium chloride works colder, and OxyChem reports it melting 5.7 lb of ice per lb at 20°F against 3.2 lb for magnesium chloride.

What we stock

Calcium Chloride Technical Grade

2 and 5 lb packs; 50 lb bags. Also used for dust control and as a desiccant.

Magnesium Chloride Hexahydrate FCC, USP GRADE

2 and 5 lb packs; 55 lb bags. A high-purity grade for formulation and lab work; priced for that, not for spreading.

Key numbers and sources