Markham, Illinois Weather and Climate Information
Understanding Markham's Continental Climate
Markham, Illinois sits in the southwestern portion of Cook County, approximately 25 miles south of downtown Chicago. The village experiences a humid continental climate characterized by four distinct seasons, with significant temperature variations throughout the year. January temperatures average around 22°F for lows and 32°F for highs, while July brings average lows of 65°F and highs reaching 84°F. The community of roughly 12,500 residents needs to prepare for weather patterns that include cold, snowy winters and warm, humid summers.
The annual precipitation in Markham totals approximately 38 inches, distributed fairly evenly across all twelve months. However, spring and early summer months from April through June typically see the highest rainfall amounts, with each month averaging between 3.5 and 4.2 inches. Snowfall accumulates to about 36 inches annually, with the heaviest snow occurring between December and February. The village's proximity to Lake Michigan, though roughly 20 miles to the east, still influences local weather patterns by moderating extreme temperatures and occasionally contributing to lake-effect snow events.
Markham residents experience an average of 189 sunny days per year, slightly below the national average of 205 days. Cloud cover is most prevalent during winter months, with November through February seeing overcast conditions approximately 65-70% of the time. The growing season extends for about 175 days, typically from late April through mid-October, which is important for local gardening enthusiasts and the maintenance of the area's parks and green spaces. You can find detailed information about seasonal transitions on our FAQ page and learn more about historical climate trends on our about page.
| Month | Avg High (°F) | Avg Low (°F) | Precipitation (inches) | Snowfall (inches) |
|---|---|---|---|---|
| January | 32 | 18 | 2.1 | 11.2 |
| February | 36 | 22 | 1.9 | 8.7 |
| March | 48 | 31 | 2.8 | 4.3 |
| April | 61 | 41 | 3.8 | 0.9 |
| May | 72 | 51 | 4.2 | 0.0 |
| June | 82 | 61 | 4.1 | 0.0 |
| July | 85 | 66 | 3.9 | 0.0 |
| August | 83 | 64 | 4.0 | 0.0 |
| September | 76 | 56 | 3.2 | 0.0 |
| October | 63 | 44 | 3.3 | 0.2 |
| November | 49 | 34 | 3.0 | 2.4 |
| December | 36 | 23 | 2.5 | 8.3 |
Severe Weather Patterns and Preparedness
Markham falls within a region that experiences moderate tornado activity, with Cook County averaging 2-3 tornadoes annually. The peak tornado season runs from April through June, coinciding with the clash of warm, moist air from the Gulf of Mexico and cooler, drier air from Canada. While most tornadoes in the area are rated EF0 or EF1 on the Enhanced Fujita Scale, residents should maintain awareness and have a safety plan. The National Weather Service office in Chicago provides real-time warnings and watches for the Markham area.
Thunderstorms occur on average 40-45 days per year in Markham, with the majority happening between May and August. These storms can produce heavy rainfall, lightning, hail, and strong winds. Flash flooding becomes a concern during intense rainfall events, particularly in low-lying areas and near the Little Calumet River, which flows through the southern portion of Cook County. The village has implemented various drainage improvements over the years to mitigate flooding risks, but residents should remain vigilant during severe weather warnings.
Winter weather hazards include blizzards, ice storms, and dangerous wind chills. The region experiences at least one significant winter storm most years, with blizzard conditions occurring every 2-3 years on average. Wind chill values can plummet to -20°F or lower during Arctic outbreaks, creating dangerous conditions for anyone spending extended time outdoors. The Illinois Emergency Management Agency provides comprehensive resources for winter weather preparedness and safety protocols that Markham residents should review annually.
| Weather Event | Average Occurrences | Peak Season | Severity Range |
|---|---|---|---|
| Tornadoes | 2-3 in Cook County | April-June | EF0-EF2 |
| Severe Thunderstorms | 40-45 days | May-August | Wind gusts 40-70 mph |
| Flash Flood Events | 3-5 events | May-July | Minor to Moderate |
| Blizzards | 0.3-0.5 events | December-February | Heavy snow, low visibility |
| Heat Advisories | 8-12 days | July-August | Heat index 100-110°F |
Seasonal Weather Characteristics
Spring in Markham brings rapidly changing conditions as the region transitions from winter cold to summer warmth. March typically starts with winter-like weather, including occasional snowfall, but by late May, temperatures consistently reach the 70s. This season is known for its unpredictability, with temperature swings of 30-40 degrees possible within 24-48 hours. The average last frost occurs around April 25th, though late-season freezes have occurred as late as mid-May in some years. Spring rainfall supports the greening of local vegetation and fills area waterways.
Summer weather in Markham is characterized by warm to hot temperatures and moderate to high humidity levels. July is typically the warmest month, with average highs of 85°F, though heat waves can push temperatures into the mid-90s for several consecutive days. The heat index, which combines temperature and humidity, frequently reaches 95-105°F during peak summer. Afternoon and evening thunderstorms provide periodic relief from the heat, though they can also bring severe weather. Air conditioning becomes essential for comfort and safety during the hottest periods.
Autumn offers some of the most pleasant weather conditions in Markham, with comfortable temperatures and lower humidity compared to summer. September often features warm days with cool nights, while October brings vibrant fall foliage as trees respond to shorter days and cooler temperatures. The first frost typically arrives around October 15th, signaling the end of the growing season. November transitions toward winter, with temperatures dropping and the first snowfall usually occurring by late month. Winter spans from December through February, with persistent cold, regular snowfall, and occasional Arctic blasts that can send temperatures below zero.
| Season | Months | Avg Temp Range | Total Precip | Notable Features |
|---|---|---|---|---|
| Winter | Dec-Feb | 18-36°F | 6.5 inches | 36 inches snow, wind chills below 0°F |
| Spring | Mar-May | 31-72°F | 10.8 inches | Variable temps, tornado season begins |
| Summer | Jun-Aug | 61-85°F | 12.0 inches | High humidity, heat index 95-105°F |
| Autumn | Sep-Nov | 34-76°F | 9.5 inches | Pleasant conditions, fall foliage |
Climate Trends and Long-Term Patterns
Climate data from the National Oceanic and Atmospheric Administration shows that Markham, like much of the Midwest, has experienced measurable warming trends over the past 50 years. Average annual temperatures have increased by approximately 1.5-2.0°F since 1970, with the most pronounced warming occurring during winter and spring months. Nighttime low temperatures have risen more rapidly than daytime highs, a pattern consistent with global climate change observations. These changes affect everything from energy usage patterns to the timing of seasonal events like leaf emergence and bird migration.
Precipitation patterns have also shifted, with data indicating a 10-15% increase in annual precipitation since the mid-20th century. More significantly, the intensity of heavy rainfall events has increased, with storms producing 2+ inches of rain in 24 hours becoming more frequent. This trend aligns with research from the University of Illinois showing that the Midwest is experiencing more precipitation falling in intense bursts rather than gentle, soaking rains. These changes have implications for urban drainage systems, agriculture, and flood risk management throughout the region.
The growing season in Markham has extended by approximately 10-14 days compared to the 1950-1980 average, with both earlier last-spring frosts and later first-fall frosts. This extension affects local gardening, landscaping decisions, and the behavior of plants and wildlife. Winter snowfall totals show high year-to-year variability, but no clear long-term trend, though the number of days with snow cover has decreased slightly. Understanding these long-term patterns helps residents make informed decisions about home improvements, landscaping, and seasonal preparations.
| Indicator | 1970 Baseline | 2020 Average | Change | Impact |
|---|---|---|---|---|
| Annual Avg Temp | 49.2°F | 51.0°F | +1.8°F | Warmer overall |
| Winter Avg Temp | 25.1°F | 27.3°F | +2.2°F | Milder winters |
| Annual Precipitation | 35.2 inches | 38.8 inches | +10.2% | Wetter conditions |
| Growing Season | 165 days | 177 days | +12 days | Longer season |
| Heavy Rain Events | 4.2/year | 5.8/year | +38% | Increased flooding risk |