Yellowstone National Park sits at over 7,000 feet elevation in the Rocky Mountains, making its weather more extreme and unpredictable than most parks. Using Perfect Weather Index (PWI) scores calculated from daily National Weather Service forecast data, this page shows exactly when conditions are most comfortable for wildlife viewing, geyser watching, and hiking — and when winter closes most of the park entirely.
Current Perfect Weather Index scores for the next 7 days at Yellowstone National Park. Higher scores indicate more comfortable outdoor conditions. Updated daily using National Weather Service forecast data.
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How to use this: Days with higher scores are generally better for hiking and outdoor activities, with more comfortable temperatures, lighter winds, and fewer weather impacts. → View official National Weather Service forecast for Yellowstone
July offers the most consistently comfortable weather at Yellowstone National Park, while June and August provide excellent conditions during the peak summer season.
Based on Perfect Weather Index (PWI) data from the Old Faithful area (elevation ~7,300 ft) — drawing on both NWS forecast records and historical climate normals — Yellowstone shows a classic high-altitude Rocky Mountain pattern: a long, cold winter with limited park access, a rapid spring thaw with variable conditions, an excellent summer window, and a quick descent into fall cold from October onward. These seasonal patterns are consistent with decades of climate data for the Yellowstone Plateau.
Raw monthly totals were normalized into monthly PWI scores (percent of possible points) and paired with the number of rare Perfect 10 days.
Monthly PWI scores reflect the percentage of possible comfort points earned at Yellowstone across all days in each month, derived from National Weather Service forecast data and consistent with long-term climate normals for the Old Faithful area. Perfect 10 days are days scoring a full 10 out of 10 on the PWI scale.
| Month | Monthly PWI Score | Perfect 10 Days | What It Means | Verdict |
|---|---|---|---|---|
| January | ~50% | 0 | Deep winter, extreme cold | Avoid |
| February | ~44% | 0 | Coldest, least comfortable | Avoid |
| March | ~50% | 0 | Winter lingers | Avoid |
| April | ~59% | 0 | Slow thaw, limited access | Caution |
| May | ~70% | 2 | Improving but variable | Good |
| June | ~81% | 2 | Excellent early-summer weather | Excellent |
| July ⭐ | ~87% | 2 | Peak comfort, most reliable | Excellent |
| August | ~84% | 2 | Warm days, cool nights | Excellent |
| September | ~79% | 2 | Crisp, stable fall weather | Very Good |
| October | ~60% | 0 | Rapid cooling, early snow | Caution |
| November | ~55% | 0 | Cold returns quickly | Avoid |
| December | ~45% | 0 | Harsh winter conditions | Avoid |
PWI scores based on NWS forecast data at the Old Faithful area (~7,300 ft). Conditions at higher elevations within the park will be cooler; Mammoth Hot Springs (~6,239 ft) runs slightly warmer.
Monthly visitor counts at Yellowstone National Park (2024, source: NPS). July is both the most visited and the highest-scoring PWI month — but September offers nearly identical wildlife viewing opportunities with 140,000 fewer visitors and strong weather scores.
| Month | % of Annual Visitors | Avg Visitors | Crowd Level |
|---|---|---|---|
| January | 1% | 42,740 | Very Low |
| February | 1% | 49,291 | Very Low |
| March | 1% | 32,862 | Very Low |
| April | 2% | 71,784 | Low |
| May | 11% | 522,450 | Moderate |
| June | 19% | 914,612 | High |
| July ⭐ | 21% | 992,352 | Peak |
| August | 18% | 868,259 | Peak |
| September | 18% | 852,435 | High |
| October | 7% | 346,025 | Moderate |
| November | <1% | 21,133 | Very Low |
| December | 1% | 30,410 | Very Low |
Source: National Park Service visitor use statistics, 2024.
July is Yellowstone's top-scoring month at 87% PWI, with the most reliable conditions for hiking, wildlife viewing, and geyser watching. All roads are open, temperatures at the 7,000-foot elevation are comfortable rather than hot, and afternoon thunderstorms — while common — are typically brief. July is also the most visited month, so popular areas like Old Faithful and Grand Prismatic Spring see the heaviest crowds. Book accommodation 6–12 months in advance for July visits.
August scores 84% PWI and sees slightly fewer visitors than July while maintaining excellent conditions. Wildflower season is winding down but wildlife activity remains high. Bison rut begins in late August, creating some of the most dramatic wildlife viewing opportunities of the year. Evenings cool noticeably at elevation, making for comfortable camping and stargazing conditions.
June scores 81% PWI — the strongest early-summer month. Wildflowers are at their peak, snowmelt fills the rivers and waterfalls to impressive levels, and most roads reopen from their winter closure by late May or early June. Visitor numbers are high but somewhat lower than peak July. Wildlife with newborn young is common in June, making it one of the best months for animal sightings.
September is the month Yellowstone regulars keep to themselves. The elk rut transforms the park — bulls bugle at dawn in Lamar Valley, and the lack of summer crowds means you can actually pull over and watch without a traffic jam forming behind you. Weather holds firm through most of the month before temperatures start dropping noticeably in late September. Fall color begins creeping into the higher meadows around mid-month. If you've been to Yellowstone in July and found the crowds exhausting, September shows you an entirely different park.
May is Yellowstone at its most raw and unpredictable. Snowpack is still melting at elevation, so road openings happen on a rolling schedule — check the NPS road status page before planning any specific routes. The payoff is wildlife that hasn't yet been pushed back by summer visitors: bears foraging near roadsides, bison herds with newborn calves, and rivers running full and fast from snowmelt. Pack layers and accept that a bluebird morning can turn to sleet by afternoon. Visitor numbers are a fraction of summer, which makes the trade-off worthwhile for flexible travelers.
Most Yellowstone roads close to regular vehicles from early November through late April. The park transitions to oversnow vehicle access only (snowcoaches and snowmobiles) from mid-December through mid-March — a unique and genuinely spectacular winter experience, but not a casual visit. PWI scores drop sharply from October (60%) through February (44%) as high-altitude cold sets in. October can still offer comfortable days but early snow is common and conditions change rapidly.
Yellowstone sits on a high plateau averaging 7,000–8,000 feet elevation, which means weather is cooler, snowfall heavier, and summer shorter than most visitors expect. Conditions vary significantly across the park's 3,472 square miles.
Afternoon thunderstorms are common throughout summer at Yellowstone's elevation — typically building after midday and clearing by evening. Lightning risk on exposed ridges and boardwalks is real; most visitors plan higher-elevation activities for morning and return to valley areas in the afternoon. Snow is possible in every month of the year at Yellowstone, even in July at higher elevations.
What is the best time to visit Yellowstone National Park?
July is the best month to visit Yellowstone based on Perfect Weather Index scores — peak comfort, full road access, and reliable conditions at high elevation. September is the best value month, offering 79% PWI scores with dramatically fewer crowds and excellent wildlife viewing during elk rut. If avoiding crowds is the priority, late May and early September offer strong weather with significantly fewer visitors than peak summer.
How cold does Yellowstone get in winter?
Yellowstone winters are extreme. January and February average highs near 20–25°F (-4 to -6°C) with lows regularly dropping below 0°F (-18°C). Wind and elevation make conditions feel even harsher. PWI scores in winter drop to around 44–50%, reflecting genuinely difficult outdoor conditions. Most park roads close to regular vehicles from November through late April, with oversnow vehicle access only from mid-December through mid-March.
Does Yellowstone get afternoon thunderstorms?
Yes — afternoon thunderstorms are a defining feature of Yellowstone's summer weather, particularly July and August. They typically build after midday and clear by evening, but lightning risk on exposed boardwalks, ridgelines, and thermal areas is real. Most experienced visitors plan higher-elevation hikes and geyser walks for morning and move to sheltered valley areas in the afternoon. The Perfect Weather Index accounts for precipitation and cloud cover in its daily scoring.
When is the best time to see wildlife at Yellowstone?
Wildlife viewing is excellent across multiple seasons. June brings newborn bison, elk calves, and bear cubs. Late August through September offers the dramatic elk rut, with bugling bulls audible throughout the park. The Lamar Valley is the premier corridor year-round for wolf and bear sightings, especially in early morning. Winter visitors on snowcoaches often have some of the most intimate bison and wolf encounters due to low crowds and animals concentrated near geothermal areas.
What is the best time to visit Yellowstone for international visitors?
September is ideal for international visitors — peak weather comfort, fewer crowds than summer, and spectacular elk rut wildlife viewing. July and August are also excellent if summer travel is preferred. Yellowstone is commonly paired with Grand Teton National Park (just south via the John D. Rockefeller Jr. Memorial Parkway) and is within a day's drive of Salt Lake City or a short flight into Jackson Hole or Bozeman airports.
What is the Perfect Weather Index?
The Perfect Weather Index (PWI) is a daily comfort score from 1–10 calculated from National Weather Service forecast data. It combines temperature, sunshine, humidity, wind, and precipitation into a single rating. A score of 8 or higher means genuinely excellent outdoor conditions. Scores below 4 reflect cold, storms, or other conditions that significantly limit outdoor comfort. Learn more about how the PWI works →