diff --git a/client/brewpi.ui b/client/brewpi.ui
index 9b13aff..4f2ad4f 100644
--- a/client/brewpi.ui
+++ b/client/brewpi.ui
@@ -3727,16 +3727,16 @@
      <string>Set the simulated/assumed ambient temperature</string>
     </property>
     <property name="decimals">
-     <number>1</number>
+     <number>0</number>
     </property>
     <property name="minimum">
-     <double>0.000000000000000</double>
+     <double>-999.000000000000000</double>
     </property>
     <property name="maximum">
-     <double>50.000000000000000</double>
+     <double>999.000000000000000</double>
     </property>
     <property name="singleStep">
-     <double>0.500000000000000</double>
+     <double>1.000000000000000</double>
     </property>
    </widget>
    <widget class="QPushButton" name="btn_pot_reset">
diff --git a/client/brewpi_gui.py b/client/brewpi_gui.py
index ad95762..220aa58 100755
--- a/client/brewpi_gui.py
+++ b/client/brewpi_gui.py
@@ -365,6 +365,15 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		self.checkbox_heater_activate.stateChanged.connect(self.on_checkbox_changed)
 		self.checkbox_stirrer_activate.stateChanged.connect(self.on_checkbox_stirrer_activate_changed)
 		self.checkbox_tc_enable.stateChanged.connect(self.on_checkbox_tc_enable_changed)
+		# Show the last value we had before the GUI last closed (see
+		# closeEvent()) right away, rather than the spinbox's bare design-time
+		# default - blockSignals so this doesn't queue a spurious 'AmbientTemp'
+		# send before the user has touched anything.
+		remembered_ambient = self.user_config.get('ambient_temperature')
+		if remembered_ambient is not None:
+			self.doubleSpinBox_ambient.blockSignals(True)
+			self.doubleSpinBox_ambient.setValue(remembered_ambient)
+			self.doubleSpinBox_ambient.blockSignals(False)
 		self.doubleSpinBox_ambient.valueChanged.connect(self.on_ambient_entry_changed)
 		self.btn_pot_reset.clicked.connect(self.on_action_pot_reset)
 		# Only meaningful (and only shown) once the server confirms its Pot
@@ -424,11 +433,12 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		# on_sud_changed() routes the reply to update_sud_forecast() instead
 		# of a save dialog.
 		self.msg_sud.send({'Save': True})
-		# Re-apply the last ambient temperature we set, in case the server
-		# restarted since (and so fell back to its own config.json default).
-		remembered_ambient = self.user_config.get('ambient_temperature')
-		if remembered_ambient is not None:
-			self.msg_system.send({'AmbientTemp': remembered_ambient})
+		# Re-apply our own ambient temperature, in case the server restarted
+		# since (and so fell back to its own config.json default) - the
+		# spinbox's current value, not the on-disk user config (which is
+		# only refreshed on shutdown - see closeEvent()), so this also picks
+		# up a change made earlier in the same session, before a reconnect.
+		self.msg_system.send({'AmbientTemp': self.doubleSpinBox_ambient.value()})
 
 	def _elapsed_min(self):
 		"""Simulated-schedule minutes elapsed since the run started, or
@@ -493,10 +503,11 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 			self.checkbox_tc_enable.blockSignals(False)
 			self.Slider_temp_soll.setEnabled(False)
 			self.doubleSpinBox_heatrate_soll.setEnabled(False)
+			# ambient_temp (the server's last echoed reading, shown in the
+			# status bar) is no longer trustworthy, but the spinbox itself is
+			# a client-owned setting (see closeEvent()/connect()) - leave it
+			# showing whatever the user last set rather than blanking it.
 			self.ambient_temp = None
-			self.doubleSpinBox_ambient.blockSignals(True)
-			self.doubleSpinBox_ambient.setValue(self.doubleSpinBox_ambient.minimum())
-			self.doubleSpinBox_ambient.blockSignals(False)
 			self.btn_pot_reset.setVisible(False)
 			self.warp_factor = 1.0
 			self.sud_elapsed_seconds = None
@@ -549,7 +560,9 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 		self.msg_pot.send({'Reset': True})
 
 	def on_ambient_entry_changed(self, value):
-		self.user_config.set('ambient_temperature', value)
+		# Persisted on shutdown instead (see closeEvent()), not on every
+		# spinbox tick - this fires on every keystroke/arrow click while
+		# editing.
 		self.msg_system.send({'AmbientTemp': value})
 
 	def update_status_env_label(self):
@@ -945,6 +958,7 @@ class Window(QtWidgets.QMainWindow, Ui_MainWindow):
 
 	def closeEvent(self, event):
 		print("Exitting gracefully!")
+		self.user_config.set('ambient_temperature', self.doubleSpinBox_ambient.value())
 		self.ws_client.disconnect()
 
 
diff --git a/client/main_window.py b/client/main_window.py
index 93c02a4..0b2ff16 100644
--- a/client/main_window.py
+++ b/client/main_window.py
@@ -1239,10 +1239,10 @@ class Ui_MainWindow(object):
         self.label_ambient.setObjectName("label_ambient")
         self.doubleSpinBox_ambient = QtWidgets.QDoubleSpinBox(self.centralwidget)
         self.doubleSpinBox_ambient.setGeometry(QtCore.QRect(620, 500, 70, 31))
-        self.doubleSpinBox_ambient.setDecimals(1)
-        self.doubleSpinBox_ambient.setMinimum(0.0)
-        self.doubleSpinBox_ambient.setMaximum(50.0)
-        self.doubleSpinBox_ambient.setSingleStep(0.5)
+        self.doubleSpinBox_ambient.setDecimals(0)
+        self.doubleSpinBox_ambient.setMinimum(-999.0)
+        self.doubleSpinBox_ambient.setMaximum(999.0)
+        self.doubleSpinBox_ambient.setSingleStep(1.0)
         self.doubleSpinBox_ambient.setObjectName("doubleSpinBox_ambient")
         self.btn_pot_reset = QtWidgets.QPushButton(self.centralwidget)
         self.btn_pot_reset.setGeometry(QtCore.QRect(700, 500, 220, 31))