Boise Idaho Weather Year Round
As a long-time Boise resident and PhD meteorologist in my full-time, bill-paying job, I felt it was only appropriate to share the nitty gritty details about what weather you can expect in Boise if you plan to visit—at any time of year!
Boise, Idaho, is the capital city of Idaho and is located in the southwest corner within the Treasure Valley. The Treasure Valley is located within the lower Snake River Plain. The city itself is nestled against the Boise Foothills to the northeast. The climate in Boise is semi-arid; we receive the bulk of our precipitation in the cooler months, and the warmer months are hot and dry. It’s rarely humid. We receive on average just over 11” of precipitation a year (this includes rain and melted snow).
Boise is fortunate to get all four seasons, and all four seasons produce vastly different weather conditions, sometimes within the same day. Like I’m sure is true in many places across the country, the joke is to “wait 10 minutes” and the weather will change. Knowing what you can expect weather-wise can help you decide when to visit Boise. Below, I shared everything you need to know about the weather in Boise, Idaho, all year round!
Be sure to check the NWS Boise weather forecast before your trip for the most up-to-date information, and don’t hike or mountain bike if the trails are muddy!
Boise Idaho Weather Year Round
When it comes to Boise, as a meteorologist, it has some of the most boring weather you’ll find anywhere in the country. We do not get extreme weather: tornadoes, strong wind storms, blizzards, and hurricanes are all extremely rare. (Being so inland and on the west side of the country, Boise never gets hurricanes, but last year we got remnants of Hurricane Hillary and that’s about how exciting it gets.)
Even though Boise weather is boring, it makes for a fantastic place to live because we are fortunate to not have to worry too much about how weather will impact our day-to-day lives. It also makes it a fun place to visit, because you don’t really have to plan your trip to avoid any season in particular. Of course, it’s still best to be prepared just in case the weather causes travel issues (pop-up thunderstorms and winter weather events have been known to cause flight delays and diversions).
Average Temperature in Boise Idaho
On average, the high temperatures in Boise are lowest in January and December (around 39°F) and highest in July (93°F) followed by August (91°F). The nighttime lows follow the same trend and range from 25°F in winter to 62°F in summer. Temperatures increase more gradually between January and July and drop off more quickly between August and December.
Deciding when to best visit Boise really depends on personal preference and what you want to do! There are fun things to do in Boise in all seasons. Obviously, I recommend visiting in mid to late summer if you want to partake in outdoor water activities. If you’re more of a chill outdoors/farmers market type and don’t like heat, I’d shoot for late spring or early fall. And, of course, there are plenty of activities to do if you enjoy the cold and snow and want to visit in winter!
The graph below shows the monthly climate normals between 1991 and 2020 based on observations taken at the official NWS weather station located at the Boise Airport. The red line is the mean maximum temperature normal, the brown line is the mean average temperature normal (taking the high and the low and averaging those numbers), and the blue line is the mean minimum temperature normal. The total precipitation normal is also shown in the green vertical bars.
Boise in Spring
Spring is a beautiful season to visit Boise. This is when the farmers markets start again and other outdoor activities kick off, including Treefort Music Fest. In spring, everyone gets outside after a long winter to hike, ride bikes, stroll on the greenbelt, and more.
Meteorological spring starts March 1 and runs through May 31, but often times it feels like spring doesn’t start in Boise until April and runs through mid-June or so. Of course, like with any change in seasons, we get spring-like days in February and March but April is when it fully feels like spring.
Spring in Boise is full of weather variety! Snow is not unheard of (it snowed in Boise in May 2022!), but thankfully it doesn’t stick around for long if it does snow. (It’s usually too warm for it to stick to pavement and asphalt.)
Boise gets most of its annual rainfall in the spring; March and May are usually two of the wettest months of the year. Thunderstorms happen most frequently in the spring compared to other seasons, but they still don’t happen all that often; we’re lucky if we get one a week!
Wind is also a common occurrence in Boise in the spring. There is almost always a breeze; you just kind of deal with it! 😆
High temperatures in the spring tend to range between 40°F and 70°F (and May/June is generally warmer than March/April, of course) but may swing beyond that range depending on whatever the large scale weather pattern is.
Boise in Summer
If you visit Boise in the summer, be prepared for the heat! Summers here are known for being hot and dry, and it is by far one of the longest seasons of the year. Boiseans spend hot summer days outside in the water or inside in air conditioning. There are few things better than Boise summer mornings or summer evenings before and after it’s too hot out to do anything!
Meteorological summer spans from June 1 to August 30. In Boise, summers start a variety of different ways; some Junes are hot, while others are rainy and cool. Summer fully sets in by July, which is also usually when the Boise River opens for floating. Early September is also summer-like, though by then the nighttime minimum temperatures are lower.
Summers here are defined by the persistent high pressure ridges that tend to dominate the entire west coast. It’s dry and sunny the majority of the time. It’s boring but at least it’s more predictable. Also, nighttime lows can be considerably cooler than daytime highs thanks to our dry desert air and low humidity.
If there’s any atmospheric instability, Boise can get random convective thunderstorms, and we’ve even gotten monsoonal moisture at times (usually that happens in August if at all). Most often, there will be thunderstorms in the distance that will die before they reach Boise, resulting in a gust front (or outflow boundary) that brings wind and dust.
Like in the other seasons, wind is a common occurrence and usually feels good in the heat. Wildfire smoke also impacts Boise frequently in the late summer (generally August through mid-September). It depends on the winds in the upper levels of the atmosphere, but in general we get most of the wildfire smoke from California, Oregon, and Washington.
Expect summer high temperatures in Boise to be hot (generally around 90-100°F). 80°F days in the summer are what I consider perfect but few and far between, especially in July and August. We also have the occasional days above 100°F. The record high temperature in Boise is 111°F!
If you prefer to spend your time in or around water (floating the river, paddleboarding at Quinn’s Pond, boating at Lucky Peak), you’ll love visiting Boise in July and August. If you’d rather spend your time enjoying other aspects of the outdoors, you may want to shoot for June or maybe even the tail end of summer (which can stretch into early to mid-September).
Boise in Fall
Out of the four seasons, unfortunately fall feels like the shortest season of them all! Not only does fall in Boise start late (usually it doesn’t fully feel like fall until October, and even then we can still get warm temperatures), but the holiday season also cuts it off at the end.
Meteorological fall is from September 1 through November 30. September is one of the best months to enjoy Boise because the daytime high temperatures usually range from 70-90°F and the nighttime lows cool off quite a bit. That said, Boise is also often impacted by wildfire smoke well into September.
The best leaf peeping in Boise happens from mid-October to early to mid-November. The photo of downtown Boise that I took above was taken in mid-October 2023 a week or two before peak. The leaves don’t all change at the same time.
As with most fall seasons, cold fronts pass through frequently, bringing temperature drops, showers, and the occasional thunderstorm. We had some great November thunderstorms in 2021 and 2022! You can also expect breezy conditions pretty much anytime but moreso with changes in the weather.
Fall high temperatures in Boise range wildly (generally around 60-90°F with the occasional 50°F day). I personally find 70°F days in the fall to be perfect, but those can be hard to come by. The temperatures can feel like a rollercoaster, which can make it difficult to pack for a short stay if there are lots of changes in the weather. Definitely stay on top of the forecast!
If you prefer to spend your time in or around water, visit Boise in early September. If you’d rather spend your time enjoying other aspects of the outdoors, aim for September or October for the best weather, though November can be nice, too. In general, I think September is one of the best months to visit Boise because the weather is perfect and there are so many events!
Boise in Winter
If you’re a fan of winter, you’ll probably like it in Boise. Winter definitely feels like it overstays its welcome by the time March rolls around! That said, winters in Boise are milder than in other parts of the state.
Meteorological winter runs from November 1 to January 31. In Boise, it really feels like winter come December, and January is the brunt of the season. We’ve been known to get snowstorms into February, and sometimes the cold temperatures and snow are still lingering come March. (Snow has been known to happen here in April and even May!)
Boise doesn’t get that much snow; we average about 17” total for the whole season. Some winters are definitely snowier than others! (Ask any local and they’ll immediately bring up “Snowmageddon” in January 2017. I was in grad school at the time but spending the holidays in Boise and got stuck here!)
Boise commonly gets temperature inversions in the winter, which is when cold air is trapped near the surface. These occur under high pressure ridges and stagnant conditions when the air isn’t mixing. This results in really cold and dreary conditions with a low layer of stratus clouds. That’s the best time to escape to the mountains! Go ski at Bogus Basin and look out over the “sea” of clouds over the valley as you enjoy the blue skies and sunshine.
Winter high temperatures in Boise range from around 20-40°F (with the occasional day around 50°F and potentially a day or more with a high below 20°F). It might sound counterintuitive, but it tends to be slightly warmer (30s) when it’s snowing and colder (20s) when we get the dreaded temperature inversions.
If there’s snow on the ground, the temperature inversions are even worse than usual! Boise does not get freezing rain that often but it can happen on occasion, so definitely keep an eye on the forecast and come prepared. (Check out what to wear for winter in Idaho!) And, of course, winter can still be quite windy at times, especially ahead of storm systems.
Planning a trip to Boise? Check out these posts!
How to Spend a Long Weekend in Boise: 3 to 4 Day Spring Itinerary
How to Spend a Long Weekend in Boise: 3 to 4 Day Summer Itinerary
How to Spend a Long Weekend in Boise: 3 to 4 Day Fall Itinerary
How to Spend a Long Weekend in Boise: 3 to 4 Day Winter Itinerary
Things to Do in Boise This Weekend: A Seasonal Boise Event Guide