Idaho's studded tire window, and the month it is out at each end

Idaho is one of two states in HopTire's ten metros that puts dates on studded tires. It writes them backwards, which is the first thing to know, and the dates it writes do not match the weather they were written for, which is the more interesting thing.

The statute writes the closed season, not the open one

Idaho Code 49-948(3), verbatim:

"No tire on a vehicle moved on a highway shall have on its periphery any block, stud, flange, cleat, spike, or any other protuberance of any material other than rubber which projects beyond the tread of the traction surface of the tire, except as allowed herein. It shall be permissible to use farm machinery with tires having protuberances which will not injure the highway, and it shall be permissible to use tire chains. Tires with built-in lugs of tungsten carbide or other suitable material, hereinafter called studs, may be used upon any vehicle when required for safety because of snow, ice, or other conditions tending to cause a vehicle to skid, that will not unduly damage the highway. Motor vehicles, trailers and semitrailers with tires having built-in studs are prohibited on public highways between the dates of May 1 and September 30, annually, except as provided in paragraphs (a), (b) and (c) of this subsection"

So the sentence everyone repeats — "studs are legal in Idaho from October to April" — is not in the statute. It is the complement of what the statute says, and we are telling you that we are deriving it rather than quoting it.

Then paragraph (b) confirms the derivation independently, and it is the only place in the section where the open window appears as dates:

"A vehicle may be equipped year-round with tires that have retractable studs if the studs retract pneumatically or mechanically to at or below the wear bar of the tire when not in use and the retractable studs protrude beyond the wear bar of the tire only between October 1 and April 30. Retractable studs may be made of metal or other material and are not subject to the stud weight requirements of subsection (4) of this section."

Two independent readings of the same section, one by complement and one written out: 1 October to 30 April.

The other two exceptions are narrow. Paragraph (a): "Fire pumper/tanker trucks and ladder trucks belonging to fire departments and firefighting agencies are exempt from the prohibited dates." Paragraph (c): special exemptions may be granted by the Idaho transportation board "if it is found by the board that enhancements to public safety outweigh the increased pavement wear".

Getting it wrong is an infraction rather than a misdemeanour. Under 49-236(2) it is an infraction to violate the provisions of chapters 3, 4 and 6 through 9 of Title 49 unless otherwise specifically provided, and 49-948 sits in chapter 9. It is not a crime. We are not going to put a dollar figure on it, because Idaho's fixed infraction penalties are set by court rule and we did not read the rule.

Now put the law next to the weather

Here is the genuinely local part, and both halves of it are sourced. The 1991 to 2020 NOAA normals for Boise Air Terminal, against the statutory window:

Month	Nights at or below 32 F	Normal snowfall	Studs lawful?
October	3.3	0.1 in	Yes, from the 1st
November	14.2	2.6 in	Yes
December	24.9	7.0 in	Yes
January	23.9	5.1 in	Yes
February	18.2	2.8 in	Yes
March	10.9	1.3 in	Yes
April	4.5	0.3 in	Yes, to the 30th
May to September	0.9, 0.0, 0.0, 0.0, 0.2	none measurable	No

The law opens about a month before the weather and closes about a month after it. October gets 3.3 freezing nights and a tenth of an inch of snow; November gets 14.2 and 2.6 inches. At the other end the window runs to 30 April while April itself has 4.5 freezing nights and three tenths of an inch.

That is not a criticism of the statute — a state-wide rule has to cover the Panhandle as well as the Treasure Valley — but it does mean the dates are a permission slip rather than a recommendation. If you fit studs on 1 October in Boise you will spend most of the month running metal on dry asphalt.

Two things in the same section that are not about you

This section gets misread more than any other tire rule in Idaho, in two specific ways, so here they are set straight.

The stud size and weight limits bind the seller and the fitter, not the driver. 49-948(4), verbatim:

"Commercial tire retailers shall not sell studded tires with studs exceeding the following weight and protrusion limitations after July 1, 2005. Commercial tire retailers and tire shops shall not manually install studs exceeding the following weight and protrusion limitations after July 1, 2005. (a) Studs shall not protrude more than six-hundredths (.06) of an inch from the surface of the tire tread when originally installed. (b) Stud size shall be as recommended by the manufacturer of the tire for the type and size of the tire. (c) Studs shall individually weigh no more than one and one-half (1.5) grams if the stud is size 14 or less. (d) Studs shall individually weigh no more than two and three-tenths (2.3) grams if the stud size is 15 or 16. (e) Studs shall individually weigh no more than three (3) grams if the stud size is 17 or larger."

The subject of every sentence is a retailer or a tire shop. The verbs are sell and manually install. Nothing in 49-948(4) creates an offence for a driver running a tire whose studs exceed those limits. It is a trade rule, and it is the half that would bind a business like ours. What binds you is the calendar in subsection (3).

And there is no Boise chain law. Subsections (5) to (9) of the same section are most of it by length and none of it applies to a commuter here. The chain-up regime is triggered only when the Idaho transportation department determines that "Lookout Pass or Fourth of July Pass on interstate 90 or Lolo Pass on state highway 12 is of an unsafe condition so as to require chains", and it applies to commercial vehicles as defined in 49-123(2)(d)(i) and (ii). All three passes are in northern Idaho, hundreds of miles from the Treasure Valley.

The only general statement about chains in Idaho law is the one in subsection (3): "it shall be permissible to use tire chains." A chain is defined in 49-104(5) as a device of "two (2) circular metal loops, one (1) on each side of the tire, connected by not less than nine (9) evenly spaced chains across the tire tread". Permitted. Not required of you, anywhere near Boise.

A winter tire and a studded tire are different things in Idaho law

This matters if you want grip without a calendar. Idaho Code 49-121(2) defines tire types, and the definitions are mutually exclusive:

"(c) Snow tire. Every rubber tire with tread design or material embedded in the tire to improve winter traction except studded tires. ... (e) Studded tire. Every tire with built-in lugs of tungsten carbide or other suitable material designed to contact the road surface for improved winter traction."

Read the three words "except studded tires". A studless winter tire is a snow tire in Idaho law, and only the studded category has a closed season. If you run a proper winter tire without studs, 49-948(3) does not reach you in July, in April or in any other month.

Where Idaho sits against the rest of our map

Of the ten metros HopTire serves, exactly two have a dated studded-tire window: this one and Pittsburgh. Pennsylvania runs 1 November to 15 April. Idaho runs 1 October to 30 April, which is forty-six days longer (DERIVED: thirty-one days earlier at the start, fifteen days later at the end). Colorado's statute attaches no dates to studs at all, and Illinois bars them for ordinary drivers.

That ranking is over the ten metros in our launch set and nothing wider. We have not surveyed all fifty states and we are not going to imply that we have.

What we do with those two dates

The window gives Boise two moments a year that force a decision, and neither arrives with a letter in the post: the first week of October, when studs may go on, and the last week of April, when they must come off.

We swap seasonal sets at your address. $350 for a set already mounted on its own wheels, $390 for loose tires that have to be mounted on the same wheels and balanced. If the off-season set is your own and has necessarily been run, we check tread and age at the visit and either refit it or tell you it is finished. We do not store tires: storage needs a building, custody terms and insurance, and we have none of those, so we do not sell it.

Book the April swap before the 30th rather than on it. The deadline is the one day everyone in the valley remembers at once.

Where to go next

Winter tire changeover in Boise is the operational version of this page: what to swap, when, and what the snow actually does. Nobody looks at a Boise car covers the rest of Idaho's tire law, including the fact that it sets no tread depth. Hillside addresses covers where a van can work.

For the repair side: mobile tire repair in Boise, a flat, a nail, a slow leak, local prices and who is open today.

Nationally: all-season, all-weather and winter tires explains the markings, seasonal changeover explains the swap, why we do not offer tire storage explains the gap, and find your tire size explains the sidewall. Our Boise service area covers where we come.

Our price: $350 on wheels, $390 loose

A seasonal changeover at your address is $350 for a set already on its own wheels and $390 for loose tires that have to be mounted on the same wheels and balanced. There is no separate call-out fee; the visit is inside the price you see online.

If instead you are buying new, we supply the tires and fit them at the same visit, matched to the door placard, one to four tires, wheels up to 22 inches, TPMS reset included where the vehicle supports it at the roadside. We do not mount tires bought elsewhere and we do not sell used tires.

A mobile puncture repair is $145 for the first tire and $50 for each additional tire in the same visit. If a tire turns out not to be repairable, the inspection is charged and the repair is not.

Questions people ask

• When are studded tires legal in Idaho? From 1 October to 30 April. The statute, 49-948(3), actually writes the closed season — studs are "prohibited on public highways between the dates of May 1 and September 30, annually" — and paragraph (b) confirms the open window in dates by allowing retractable studs to protrude "only between October 1 and April 30".
• What happens if I leave them on in May? It is an infraction, not a misdemeanour: 49-236(2) makes violations of chapters 3, 4 and 6 through 9 infractions, and 49-948 sits in chapter 9. We will not quote a fine, because the fixed penalties are set by court rule that we have not read.
• Are heavy studs illegal for me to drive on? No. The 0.06 inch protrusion limit and the 1.5, 2.3 and 3 gram weight limits in 49-948(4) bind "commercial tire retailers" and "tire shops", and the verbs are sell and manually install. They create no offence for a driver.
• Do I need chains around Boise? No. Idaho's chain requirement in 49-948(5) to (9) applies to commercial vehicles on Lookout Pass and Fourth of July Pass on I-90 and Lolo Pass on SH-12, all in northern Idaho. The only general statement in the section is that "it shall be permissible to use tire chains".
• Can I run winter tires in summer? Yes, if they are studless. Idaho Code 49-121(2)(c) defines a snow tire as one with tread design or embedded material to improve winter traction "except studded tires", so the closed season reaches only the studded category.
• Is Idaho's window the longest anywhere? We do not know and we are not going to say. Of the ten metros we serve, only Idaho and Pennsylvania have dated windows, and Idaho's is forty-six days longer than Pennsylvania's. That is the whole population we have checked.