A large-scale ridge was the reasoning behind the warmer temperatures for the first 3 days of May. Highs soared to 80° on May 1st, followed by two days in the 70s.
The warm streak has come to an end. The ridge at the upper levels has flattened a bit, running more west to east as opposed to a north-south orientation. This will allow for cooler air to move back in and stick around through the rest of the week. Along with the cooler temperatures, a series of short waves will also bring chances for showers at times this week.
Starting on Monday more rain is expected to arrive. While most of the morning will be on the drier side, the showers will begin to arrive during the afternoon, with light rain likely during the evening and overnight.
Light to moderate rainfall is especially expected between 5 PM Monday and 5 PM Tuesday. This will likely be the most rain much of the state has seen in over 3 weeks. Expect it to end by the middle of the day Tuesday as a strong NW wind pushes clouds east. Most of the state will see between a quarter and three-quarters of an inch of rainfall with this wave.
Despite drier weather and more sun during the middle of the week, cooler temperatures will continue across central Iowa. Highs will stay in the lower to middle 60s, which is also actually the warmest part of the week ahead.
By the end of the week, more rain is possible, especially Thursday into Friday. Highs look to stay in the 50s and 60s through next weekend.