Weather Delay Days in Philadelphia, PA

A 2016-2025 NOAA station baseline for Philadelphia, PA, scored against Silt soil. January is the worst month at roughly 14 unworkable workdays; the full monthly baseline is below.

Month by month

Typical is the ten-year mean — the figure to carry in a bid or schedule. Median is the middle year of the ten; where it exceeds the mean, the baseline is skewed by unusually dry years. Abnormal above is the mean plus one standard deviation, past which a month sits outside its normal range and is the stronger basis for a claim.

Month	Avg rainfall	Typical lost workdays	Median	Abnormal above
January	3.40″	14	15	18
February	3.10″	12	13	17
March	4.60″	11	11	14
April	4.15″	9	10	11
May	4.85″	10	9	14
June	4.36″	10	10	14
July	4.68″	10	11	13
August	3.98″	8	7	12
September	4.40″	7	7	10
October	3.36″	7	7	11
November	3.21″	9	8	13
December	4.75″	14	14	17

What these numbers mean

A workday counts as lost when precipitation exceeded 0.1″, or the ground had not finished drying from an earlier rain, or the ground was frozen. Only Monday to Friday is counted. Days the station did not report are excluded from the count entirely rather than assumed workable — understating a contractor’s exposure is the one direction of error a delay figure must never make.

Read these month by month, not added up. Each row is an independent baseline for a site in the condition it is in that month. Summing twelve of them would assume a jobsite never improves — no stone haul roads, no stabilised pads, no ditching — which is wrong for any real project past its first few months. Over a single month, or over the two-to-four week window a delay claim actually covers, that effect is negligible and these figures hold. Over a year it is not, so no annual total is published here.

On silt soil this model charges an average of 1.29 drying days per rain day in Philadelphia, PA. That is the figure worth checking against your own experience: if it is wrong for your sites, every number on this page moves with it.

Why Silt soil matters here

Rainfall totals alone understate an earthwork schedule, because the ground stays untrafficable after the rain stops. The drying clock for Philadelphia, PA is seeded at Silt, 2.0 base drying day(s), then adjusted for the day’s temperature, rainfall intensity, and how wet the ground already was over the preceding five days.

The same month of rain costs a sand site almost nothing and a clay site a week. That is why two contractors in the same county can honestly disagree about how many weather days a job should carry.

Year by year: January

An average hides the spread, and the spread is what a claim turns on. Lost workdays in January for each year of the baseline:

Year	Lost workdays
2016	11
2017	16
2018	19 — above the abnormal threshold
2019	18
2020	13
2021	7
2022	18
2023	9
2024	15
2025	14

Nearby metros

Soil changes faster than weather does. These are the closest markets we track — note how the worst month can differ even where the rainfall barely does.

Metro	Distance	Soil	Worst month	Lost workdays
Newark / North Jersey, NJ	75 mi	Silt	January	17
Baltimore, MD	89 mi	Clay	January	14
Washington DC / NoVA, DC	123 mi	Clay	January	15
Hartford, CT	180 mi	Silt	January	16
Richmond, VA	206 mi	Clay	January	15

See every metro we track →

Data source

Observations from the NOAA National Centers for Environmental Information, Global Historical Climatology Network – Daily (GHCND) — U.S. Government public-domain station records. Baseline 2016-2025, 3653 observed days. Algorithm v2.3.0, generated August 1, 2026.

These figures model soil-dependent site work — earthwork, grading, excavation, foundations and underground utilities. Enclosed and vertical work is not modelled. They are planning figures derived from station observations and a deterministic soil model, not site-specific geotechnical findings, and they do not establish contractual entitlement, causation or damages.