Romeoville weather in May: Romeoville, Illinois: normal highs, lows, rain and records for May
Romeoville in May has a normal high of 72°F and a normal low of 50°F, a daily mean of 61°F, rising from 67°F on the 1st to 78°F by the 31st. Measurable precipitation falls on 14 days in a normal May, 4.81 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 22°C and low of 10°C, 122 mm of precipitation in May.
- NOAA stationRomeoville Weather Office
- Station IDUSC00117457
- Location41.60°N 88.08°W
- Elevation660 ft (201 m)
- From the center2 miles
- Population41,177
- Jan 32° 16°
- Feb 36° 20°
- Mar 49° 30°
- Apr 61° 40°
- May 72° 50°
- Jun 82° 60°
- Jul 85° 65°
- Aug 83° 63°
- Sep 76° 55°
- Oct 64° 44°
- Nov 49° 32°
- Dec 37° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Romeoville in May?
The normal high is 72°F and the normal low 50°F, for a daily mean of 61.4°F. May is 11.1°F warmer than April and 9.5°F cooler than June. May is the 5th warmest month of the year in Romeoville and the wettest. Across the month the normal high rises 11°F, from 67°F on May 1 to 78°F on May 31. From one year to the next May's mean temperature typically moves about 3.2°F either way (NOAA's standard deviation), so roughly two Mays in three average between 58°F and 65°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 44%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| May 1 | 67°F | 45°F | 44% | 28% |
| May 8 | 70°F | 48°F | 44% | 29% |
| May 15 | 72°F | 50°F | 44% | 29% |
| May 22 | 75°F | 52°F | 43% | 28% |
| May 31 | 78°F | 56°F | 42% | 28% |
Every day of May: normal high, low and chance of precipitation (warmest afternoon May 31, coldest night May 1)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| May 1 | 67°F | 45°F | 44% | 28% | 14 h |
| May 2 | 67°F | 45°F | 44% | 29% | 14 h |
| May 3 | 68°F | 46°F | 44% | 29% | 14 h |
| May 4 | 68°F | 46°F | 44% | 29% | 14 h 10 min |
| May 5 | 69°F | 46°F | 44% | 29% | 14 h 10 min |
| May 6 | 69°F | 47°F | 44% | 29% | 14 h 10 min |
| May 7 | 69°F | 47°F | 44% | 29% | 14 h 10 min |
| May 8 | 70°F | 48°F | 44% | 29% | 14 h 10 min |
| May 9 | 70°F | 48°F | 44% | 29% | 14 h 20 min |
| May 10 | 70°F | 48°F | 44% | 29% | 14 h 20 min |
| May 11 | 71°F | 49°F | 44% | 29% | 14 h 20 min |
| May 12 | 71°F | 49°F | 44% | 29% | 14 h 20 min |
| May 13 | 71°F | 49°F | 44% | 29% | 14 h 30 min |
| May 14 | 72°F | 50°F | 44% | 29% | 14 h 30 min |
| May 15 | 72°F | 50°F | 44% | 29% | 14 h 30 min |
| May 16 | 73°F | 50°F | 44% | 29% | 14 h 30 min |
| May 17 | 73°F | 51°F | 44% | 29% | 14 h 30 min |
| May 18 | 73°F | 51°F | 44% | 29% | 14 h 40 min |
| May 19 | 74°F | 51°F | 43% | 29% | 14 h 40 min |
| May 20 | 74°F | 52°F | 43% | 29% | 14 h 40 min |
| May 21 | 74°F | 52°F | 43% | 29% | 14 h 40 min |
| May 22 | 75°F | 52°F | 43% | 28% | 14 h 40 min |
| May 23 | 75°F | 53°F | 43% | 28% | 14 h 40 min |
| May 24 | 75°F | 53°F | 43% | 28% | 14 h 50 min |
| May 25 | 76°F | 54°F | 43% | 28% | 14 h 50 min |
| May 26 | 76°F | 54°F | 43% | 28% | 14 h 50 min |
| May 27 | 76°F | 54°F | 42% | 28% | 14 h 50 min |
| May 28 | 77°F | 55°F | 42% | 28% | 14 h 50 min |
| May 29 | 77°F | 55°F | 42% | 28% | 14 h 50 min |
| May 30 | 77°F | 55°F | 42% | 28% | 15 h |
| May 31 | 78°F | 56°F | 42% | 28% | 15 h |
- Normal high
- 72°FMay average
- Normal low
- 50°FMay average
- Precipitation
- 4.81 inmonth total
- Days with precipitation
- 140.01 inch or more
- Days at 90°F or more
- 1
- Daylight
- 14 h to 15 hMay 1 to May 31
- Days at 70°F or more
- 18
- Days at 80°F or more
- 8
- Sunshine
- 71%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00117457; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Romeoville in May?
On a given May day the chance of 0.01 inch or more is 43% on average, highest around May 10 (44%). In all, 4.81 in falls on 14 days of a normal May, 1 of them with an inch or more.
In a normal May in Romeoville, 1 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00117457.
What are the records for May in Romeoville?
The warmest May temperature on this station's record (since 1992) is 97°F, on May 15, 2025; the coldest is 12°F, on May 12, 1994. The wettest May brought 10.11 in (2019).
The May mean against the 1991-2020 normal of 61.4°F: 2021 59.3°F (−2.1), 2022 63.2°F (+1.8), 2023 62.2°F (+0.8), 2024 64.5°F (+3.1), 2025 58.7°F (−2.7), 2026 59.5°F (−1.9). 3 of 6 ran warmer than normal.
| May | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 59.3°F | −2.1°F | 4.26 in |
| 2022 | 63.2°F | +1.8°F | 4.64 in |
| 2023 | 62.2°F | +0.8°F | 1.28 in |
| 2024 | 64.5°F | +3.1°F | 5.47 in |
| 2025 | 58.7°F | −2.7°F | 1.66 in |
| 2026 | 59.5°F | −1.9°F | 1.64 in |
Source: records: ACIS, station USC00117457; recent months: ACIS, station USC00117457. Records and recent months use complete months only.
How does May in Romeoville compare across Illinois?
Across the 144 places PlainClimate covers in Illinois, May normal highs run from 67°F in Waukegan to 79°F in Belleville; Romeoville's is 72°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.