Waterloo, Iowa · May 2027
Northern lights in Waterloo, Iowa in May 2027
Answer
May against the rest of the year
May cloud at Waterloo, Iowa averages 63% in NASA POWER's 2001 to 2020 record, 5 points cloudier than its yearly mean. September is Waterloo, Iowa's clearest month at 46%. By civil night times clear sky, May scores 3.0 hours at Waterloo, Iowa, 12th of 12. Minneapolis, 286 km away, averages the same 63%.
Civil night at Waterloo, Iowa starts May at 8 h 46 min and reaches 7 h 41 min by May 31, 1.1 hours shorter. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 5.3 hours on the 15th.
May night by night
May opens toward a new moon on May 6, with full moon on May 20, in America/Chicago dates. Waterloo, Iowa gets 129 hours of civil night with the moon below the horizon across the month. The best of them for moon-free darkness inside 10 PM to 2 AM: May 1 (4 h), May 2 (4 h), May 3 (4 h).
- 1
20% lit
7.3 h
- 2
12% lit
7.6 h
- 3
6% lit
7.9 h
- 4
2% lit
8.3 h
- 5
0% lit
8.6 h
- 6
1% lit
8.3 h
- 7
4% lit
7.0 h
- 8
10% lit
5.9 h
- 9
18% lit
4.9 h
- 10
28% lit
4.1 h
- 11
39% lit
3.5 h
- 12
50% lit
3.0 h
- 13
61% lit
2.6 h
- 14
72% lit
2.2 h
- 15
81% lit
1.8 h
- 16
89% lit
1.4 h
- 17
94% lit
0.9 h
- 18
98% lit
0.4 h
- 19
100% lit
0.0 h
- 20
99% lit
0.3 h
- 21
97% lit
1.3 h
- 22
93% lit
2.1 h
- 23
87% lit
2.8 h
- 24
80% lit
3.3 h
- 25
72% lit
3.8 h
- 26
63% lit
4.1 h
- 27
54% lit
4.5 h
- 28
44% lit
4.8 h
- 29
34% lit
5.1 h
- 30
25% lit
5.4 h
- 31
16% lit
5.8 h
Each cell is the night that starts on that date. Hours are civil-dark time with the moon below the horizon; the green rule scales with them. Green outline: new moon. Bone outline: full moon.
Activity in past Mays
Waterloo, Iowa needs Kp 8 for the average oval edge to sit overhead. 8 of the 930 May days from 1996 to 2025 (1%) reached it in the GFZ Potsdam record, one of the three most active months for that level; storm days with Kp 5 or more made up 10%. Waterloo, Iowa sits at 51.1 degrees geomagnetic. The lowest NOAA storm level whose typical viewing latitude reaches it is G3 (Kp = 7). By SWPC's rule the average oval edge is overhead only at Kp 8.
May across United States
No month-page town in United States has more civil night on May 15 than Waterloo, Iowa; the national median is 7.6 hours. Coming from April (9.5 hours at Waterloo, Iowa), May loses darkness, and June brings shorter nights (7.4 hours on the 15th).
| Town | Civil night | Cloud |
|---|---|---|
| Waterloo, Iowa | 8.2 h | 63% |
| Buffalo | 8.1 h | 65% |
| Portland, Maine | 8.0 h | 66% |
| Minneapolis | 7.9 h | 63% |
| Duluth | 7.6 h | 65% |
| Fargo | 7.6 h | 61% |
| Seattle | 7.5 h | 70% |
| Juneau | 5.1 h | 74% |
| Anchorage | 3.8 h | 79% |
| Eagle River | 3.7 h | 79% |
| Fairbanks | 0.0 h | 70% |
Darkness and moon, every night
| Night | Civil | Astronomical | Moon-free dark | Moon-free, 10 PM to 2 AM | Moon lit |
|---|---|---|---|---|---|
| Sat May 1 | 8 h 46 min | 6 h 7 min | 7 h 15 min | 4 h | 20% |
| Sun May 2 | 8 h 44 min | 6 h 3 min | 7 h 34 min | 4 h | 12% |
| Mon May 3 | 8 h 41 min | 5 h 59 min | 7 h 55 min | 4 h | 6% |
| Tue May 4 | 8 h 38 min | 5 h 56 min | 8 h 20 min | 4 h | 2% |
| Wed May 5 | 8 h 36 min | 5 h 52 min | 8 h 36 min | 4 h | 0% |
| Thu May 6 | 8 h 33 min | 5 h 48 min | 8 h 16 min | 4 h | 1% |
| Fri May 7 | 8 h 31 min | 5 h 45 min | 7 h | 3 h 39 min | 4% |
| Sat May 8 | 8 h 28 min | 5 h 41 min | 5 h 52 min | 2 h 32 min | 10% |
| Sun May 9 | 8 h 26 min | 5 h 37 min | 4 h 54 min | 1 h 35 min | 18% |
| Mon May 10 | 8 h 23 min | 5 h 34 min | 4 h 7 min | 50 min | 28% |
| Tue May 11 | 8 h 21 min | 5 h 30 min | 3 h 30 min | 14 min | 39% |
| Wed May 12 | 8 h 18 min | 5 h 27 min | 3 h | 0 min | 50% |
| Thu May 13 | 8 h 16 min | 5 h 23 min | 2 h 34 min | 0 min | 61% |
| Fri May 14 | 8 h 14 min | 5 h 20 min | 2 h 10 min | 0 min | 72% |
| Sat May 15 | 8 h 11 min | 5 h 16 min | 1 h 47 min | 0 min | 81% |
| Sun May 16 | 8 h 9 min | 5 h 13 min | 1 h 23 min | 0 min | 89% |
| Mon May 17 | 8 h 7 min | 5 h 9 min | 56 min | 0 min | 94% |
| Tue May 18 | 8 h 5 min | 5 h 6 min | 26 min | 0 min | 98% |
| Wed May 19 | 8 h 3 min | 5 h 3 min | 0 min | 0 min | 100% |
| Thu May 20 | 8 h | 4 h 59 min | 18 min | 0 min | 99% |
| Fri May 21 | 7 h 58 min | 4 h 56 min | 1 h 15 min | 22 min | 97% |
| Sat May 22 | 7 h 56 min | 4 h 53 min | 2 h 5 min | 1 h 12 min | 93% |
| Sun May 23 | 7 h 54 min | 4 h 50 min | 2 h 45 min | 1 h 54 min | 87% |
| Mon May 24 | 7 h 53 min | 4 h 47 min | 3 h 18 min | 2 h 28 min | 80% |
| Tue May 25 | 7 h 51 min | 4 h 44 min | 3 h 45 min | 2 h 56 min | 72% |
| Wed May 26 | 7 h 49 min | 4 h 41 min | 4 h 7 min | 3 h 19 min | 63% |
| Thu May 27 | 7 h 47 min | 4 h 38 min | 4 h 27 min | 3 h 40 min | 54% |
| Fri May 28 | 7 h 45 min | 4 h 35 min | 4 h 46 min | 4 h | 44% |
| Sat May 29 | 7 h 44 min | 4 h 33 min | 5 h 5 min | 4 h | 34% |
| Sun May 30 | 7 h 42 min | 4 h 30 min | 5 h 25 min | 4 h | 25% |
| Mon May 31 | 7 h 41 min | 4 h 28 min | 5 h 48 min | 4 h | 16% |
Questions
- Can you see the northern lights in Waterloo, Iowa in May?
- On dark, clear nights with enough activity. 31 of 31 nights at Waterloo, Iowa have civil darkness, and 1% of past May days reached Kp 8.
- How dark is Waterloo, Iowa in May?
- Waterloo, Iowa averages 8.2 hours of civil night a night in May 2027, from 8 h 46 min on the 1st to 7 h 41 min on the last night.
- How cloudy is Waterloo, Iowa in May?
- NASA POWER's 2001 to 2020 climatology gives Waterloo, Iowa's 1 degree cell 63% mean cloud in May, against 58% for the whole year. It is an all-hours average, not a forecast.
- What is the best night in May 2027 for aurora in Waterloo, Iowa?
- By darkness and moon alone, May 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Waterloo, Iowa. Activity on that date will only be known hours ahead.
- Is May or June better in Waterloo, Iowa?
- By civil night times the clear share, May scores 3.0 hours at Waterloo, Iowa and June 3.3. June comes out ahead.
Sources and verification
- SunCalchttps://github.com/mourner/suncalc
- NASA POWER climatologyhttps://power.larc.nasa.gov/docs/services/api/temporal/climatology/
- GFZ Potsdam Kp indexhttps://kp.gfz.de/en/data
- NOAA SWPC, Tips on viewing the aurorahttps://www.spaceweather.gov/content/tips-viewing-aurora
Quoted figures last checked against their sources on 2026-09-30; next review 2026-12-31. Computed figures come from SunCalc and the IGRF-14 dipole as described in the methodology. Every quote is listed in the sources ledger.