Locally heavy rains at the end of April produced minor flooding along the lower reaches of the Black River on the first 2 days of May. Locally heavy rains on the evening of the 19th produced another round of minor flooding on portions of the Black River from the 20th to 22nd. The Mississippi River was already running near bank-full at the beginning of May. A period of widespread moderate to heavy rains across much of MN and northern WI during the last week of April produced strong within bank rises or minor flooding along the Mississippi River during the first 2 weeks of May. With soils quite wet and the Mississippi River running quite high, widespread moderate to heavy rains across central MN and northern WI around the 12th and 19th sent another round of strong within bank rises or minor flooding down the river during the 3rd week of May.
May 2014 rainfall was near to below normal across the southeast two-thirds of the HSA, to near and above normal across the northwest third. Weak weather systems brought light to locally moderate rains to mainly the north half of the HSA on the 1st and 2nd. Stronger systems brought light to moderate rains to mainly the northwest third of the HSA on the 7th into the 8th and moderate to locally heavy rains to most of the HSA on the 12th into the 13th. A passing system brought light to locally moderate rains to the southwest end of the HSA on the 15th. Another stronger system produced moderate to locally heavy and excessive rains across the north half of the HSA on the 19th. A slow moving cold front brought light to moderate rains to the northeast two-thirds of the HSA on the 27th and 28th. The beginning of another period of widespread moderate to heavy rain started late on May 31st, with light to moderate rains across the southwest end of the HSA during the evening.
Normal May rainfall ranges from around 3.5 inches across the northeast half of the HSA, to near 4.5 inches across the northeast IA portion of the HSA. Rainfall this month ranged from 35 to 75 percent across much of the southeast two-thirds of the HSA, to 75 to 125 percent of normal across much of the northwest third. Most May rainfall totals were 50 to 100 percent of normal. Extreme totals recorded for the month ranged from 1.41 inches at Viroqua in Vernon Co. WI and 1.46 inches near Lancaster in Grant Co. WI, to 5.54 inches at Osseo in Trempealeau Co. WI and 5.71 inches at Westboro in Taylor Co. WI. Unlike last year, snowfall this May was limited to a few flurries across the far northwest end of the HSA on the 1st.
Average temperatures for May 2014 were 56 to 60 degrees. This was 0.5 degree below to 1 degree above the normals. Temperatures were below normal from the 1st to the 4th then near to above normal from the 5th to the 12th. Temperatures were below to much below normal from the 13th to the 17th then near to above normal from the 18th to the 24th. The last week of the month (25th to 31st) saw above to much above normal temperatures. Extremes for the month ranged from lows in the middle 20s to upper 30s on the mornings of the 16th and 17th, to highs in the 80s to near 90 on the 30th and 31st.
Flows in the rivers and streams of the HSA were above to much above normal during May. The near normal temperatures during the month and generally below normal rainfall helped spring fieldwork, planting activities and crop growth to progress and catch up. Most crop growth and progress was only a week to 10 days behind normal at the end of May. However, wet soils did continue to delay planting across some northern portions of the HSA.