Longmont pollen forecast - today, tomorrow and the week ahead

On 16 July 2026, overall pollen levels in Longmont are moderate. Grass is the main contributor to airborne pollen

On 17 July 2026, pollen conditions in Longmont will be different from today, with grass at medium levels, ambrosia at low levels

According to the five-day outlook, grass pollen levels are expected to gradually decrease, while ambrosia pollen will increase, suggesting mixed conditions later in the week.

On 16 July 2026, Grass is the dominant pollen source in Longmont. birch, cypress, oak, willow, alder, ambrosia, and artemisia are not currently active.

Longmont's pollen season opens with elm and cottonwood from late February, followed by oak and ash through April and May. Grass pollen peaks through June and July. The St. Vrain Creek valley and the Front Range setting channel prevailing westerly winds, while surrounding Colorado farmland and the open plains to the east contribute substantial grass pollen. The Rocky Mountain foothills add pine and grass pollen under downslope easterly winds.

The Longmont pollen forecast is updated four times daily. See the timestamp below for the most recent update.

Studies show that most pollen exposure (often 70–90%) comes from nearby sources, such as local trees and vegetation. A good pollen forecast therefore depends on accurately representing local vegetation. Pollen can travel long distances, but this usually matters only early in the season or during specific wind events.

Pollen data is often misunderstood. Most "pollen levels" are not real-time measurements, but forecasts.

Direct pollen measurements are typically delayed by 1-2 days because they require manual analysis. To show current conditions in Longmont, modern forecasts combine recent measurements, weather data, and information about local vegetation.

This allows us to estimate pollen levels for today and the coming days, not just report the past.

Airmine’s atmospheric monitoring platform was developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team, using satellite and Earth observation technologies to improve emissions monitoring.