import datetime as dt
import random
import sys
from threading import Thread, Event
monitor_event = Event()
PROMPT = 'Type quit to quit: '

def print_msg(msg):
    print()
    print(msg)
    print(PROMPT, end='')
    sys.stdout.flush()

def read_temperature():
    temp = random.gauss(30, 7)
    # print('reading', temp)
    return temp

class Monitor(Thread):
    def __init__(self, delta_sensor, delta_report, threshold):
        Thread.__init__(self)
        self.ds = delta_sensor.total_seconds()
        self.delta_report = delta_report
        self.threshold = threshold
        
    def run(self):
        # self.resume = True
        self.next_report = dt.datetime.now() + self.delta_report
        while True:
            monitor_event.clear()
            monitor_event.wait(timeout=self.ds)
            if monitor_event.is_set():
                break
            temp = read_temperature()
            if temp > self.threshold:
                print_msg(
                    'Warning: temperature {:.1f} above threshold {:.1f}'.format(
                    temp, self.threshold))
            t = dt.datetime.now()
            if t >= self.next_report:
                print_msg(
                    '{:%Y-%m-%d %H:%M:%S}: current temperature is {:.1f}'.format(
                        t, temp))
                self.next_report = t + self.delta_report

if __name__ == "__main__":
    monitor = Monitor(dt.timedelta(seconds=1), dt.timedelta(seconds=5), 40)
    monitor.start()
    try:
        while True:
            s = input(PROMPT)
            if s.strip().lower() in ('q', 'quit'):
                break
    finally:
        monitor_event.set()
        monitor.join()

Output:
λ python3 paillasse/cooler.py
Type quit to quit: 
2019-05-29 08:12:04: current temperature is 27.4
Type quit to quit: 
2019-05-29 08:12:09: current temperature is 36.9
Type quit to quit: 
2019-05-29 08:12:14: current temperature is 25.2
Type quit to quit: 
2019-05-29 08:12:19: current temperature is 25.3
Type quit to quit: 
2019-05-29 08:12:24: current temperature is 28.4
Type quit to quit: 
2019-05-29 08:12:29: current temperature is 34.4
Type quit to quit: 
2019-05-29 08:12:34: current temperature is 26.3
Type quit to quit: 
Warning: temperature 46.6 above threshold 40.0
Type quit to quit: 
Warning: temperature 41.8 above threshold 40.0
Type quit to quit: 
2019-05-29 08:12:39: current temperature is 29.3
Type quit to quit: 
2019-05-29 08:12:44: current temperature is 31.3
Type quit to quit: 
Warning: temperature 42.2 above threshold 40.0
Type quit to quit: quit