Best Time of Year to Clean Windows

The Two Best Windows for Most Climates

For the majority of U.S. climates, two timing windows produce the longest-lasting clean:

• Late spring (May–early June): After the main tree and grass pollen peak, before summer heat bakes deposits onto glass. This is typically the highest-impact cleaning of the year.
• Late fall (October–November): After leaves have dropped and before winter precipitation begins. Clears the year's accumulated organic residue and sets you up for cleaner glass through the winter months when low sun angles make dirty glass most noticeable.

By Region: Optimal Timing

Regional climate drives significant variation in optimal timing:

• Southeast and Mid-Atlantic: Late May (post-oak-pollen, pre-heat) and late October (post-leaf-drop). Avoid March–April when tree pollen is at peak.
• Midwest: Late May and mid-November. Cottonwood season (late May) is the trigger for the spring cleaning — wait until after it ends. Fall cleaning in November after all hardwood species have dropped.
• Texas and South Central: April (post-cedar, mid-oak pollen) and November. Cedar pollen from January through March is the contamination driver — clean after it peaks.
• Desert Southwest (AZ, NV, NM): Late June before monsoon season and February. The pre-monsoon cleaning is the most important — the first monsoon rains hit dusty glass and deposit a mineral layer that requires professional removal.
• California: September–October before the rainy season begins, and April after spring rains end. The fall cleaning is the most important — it removes summer's dry accumulation before rain bakes it in.
• Pacific Northwest: Late April–May after the winter rains taper, and September before fall rains return. Interior cleaning is valuable year-round since outdoor cleaning is quickly undone by the next day's rain in winter.
• Northeast: Late June after the sequential pollen season (tree → grass → mold spores), and October before first frost. Do not clean in April or May — you're cleaning into peak pollen season.
• Mountain: Late May–June after snowmelt, and September before first freeze. The post-snowmelt cleaning is the most impactful — it removes the silty film that melt water leaves on lower-level glass.

What to Avoid

Certain timing choices consistently produce shorter-lasting results:

• Cleaning during active pollen season: Pollen deposits on glass within hours of cleaning in high-pollen periods. Wait until after your local pollen peak.
• Cleaning right before heavy rain: Light rain rinses and deposits minerals; heavy rain during a storm doesn't 'clean' glass, it deposits more. If a significant storm is forecast within 48 hours, defer cleaning.
• Cleaning exterior glass when temperatures are below freezing: Water-fed pole and squeegee cleaning requires above-freezing temperatures for safe operation and quality results. Many window cleaning companies pause exterior service below 35°F.
• Cleaning coastal glass right before onshore wind events: Salt air deposits in hours during high-wind coastal conditions. For coastal properties, clean during low-wind periods.

Interior Timing Is Different

Interior window cleaning doesn't have the same seasonal constraints as exterior work. Interior glass isn't subject to weather and pollen — it accumulates cooking grease, dust, and film at a fairly constant rate year-round.

The best time for interior cleaning is whenever it fits your schedule, with one consideration: low-light winter months make interior glass clarity most valuable, so a fall or early-winter interior cleaning makes the most of the season when you're indoors most and natural light is limited.