A calendar question
Homeowners often ask when to paint. For the outside of a house, the answer depends on temperature, sun and rain. For the inside, it depends on whether you can live with open windows and fresh-paint smell. NOAA's degree day normals for the Erie International Airport station are a rough guide to how the year divides between heating and cooling, and that's how this page uses them.
What degree days measure
A degree day counts how far a day's average temperature sits below or above a base temperature. Cool days add heating degree days, warm days add cooling degree days, and the further from the base, the more each day adds. Over a year, the totals show how much of the calendar needs heat and how much needs cooling.
NOAA's annual climate normals for the Erie International Airport station (listed as ERIE INTL AP, PA US) give a normal of 5,904.7 heating degree days a year. The same normals give 752.1 cooling degree days a year, of which 595.6 fall in the June-August summer season. Those are the station's 1991-2020 normals.
Reading the two totals together
For painting, the useful part is the shape:
- The heating total is far larger than the cooling total, so heated-house months take up a large share of the year.
- Most of the cooling degree days land in June, July and August, which tells you where the warmest stretch of the year falls at that station.
Exterior paint needs air and surface temperatures above the minimum on its label, and for a while after application. Months with heavy heating demand will include plenty of days that don't meet that minimum. A practical plan puts exterior work in the warmer part of the year and leaves the heated months for interior rooms, but your painter should decide day by day from the forecast and the label, not from a calendar.
Interior work in the heated months
Painting indoors while the heat is on is common and works well, with a few adjustments.
- Fresh air. Water-based paints still release moisture and odor as they dry. Cracking a window in the room being painted, with a fan pushing air out, helps both.
- Warm walls. Exterior walls in a heated room can still be cool to the touch. Labels give a minimum surface temperature for interior products too.
- Dry air. Heated indoor air dries paint faster at the surface. Painters may work smaller sections so the wet edge doesn't set before they reach it.
- Furniture and timing. Rooms are in daily use in winter. Ask the painter to plan the order so you always have a usable bedroom and bathroom.
The interior painting page covers what good interior prep looks like.
Exterior work in the short warm stretch
Because the warmest weeks are a limited window, exterior painters' calendars fill early. Booking the walk-through ahead of the season gives you more choice of dates and time for the painter to inspect peeling areas and quote repairs. Ask how they handle a week of rain in the middle of a booked job, and whether a late-season exterior would be finished the following year if the weather turns.
Pennsylvania's home improvement law
The Pennsylvania Office of Attorney General says the Home Improvement Consumer Protection Act's list of home improvements includes painting, and its rule for which contractors must register is in the card below. You can ask a painter whether they're registered with the Attorney General's Office; we don't check.
Points to settle with the painter
- Which part of the job is inside and which outside, and in what order?
- What temperatures do the exterior products need, during and after application?
- How will rooms be ventilated while the heat is running?
- Which rooms stay usable each day?