diff --git a/app/build.gradle b/app/build.gradle
index f39f9a21..c48e284e 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -38,7 +38,7 @@ android {
             buildConfigField "String[]", "DEFAULT_API_KEYS", "{null}"
         }
 
-        buildConfigField "String", "BASE_URL", "\"https://api.openweathermap.org/data/2.5/\""
+        buildConfigField "String", "BASE_URL", "\"https://api.openweathermap.org/data/3.0/\""
 
         javaCompileOptions {
             annotationProcessorOptions {
diff --git a/app/src/main/java/org/secuso/privacyfriendlyweather/activities/ForecastCityActivity.java b/app/src/main/java/org/secuso/privacyfriendlyweather/activities/ForecastCityActivity.java
index dc5d09bd..3cb16832 100644
--- a/app/src/main/java/org/secuso/privacyfriendlyweather/activities/ForecastCityActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlyweather/activities/ForecastCityActivity.java
@@ -1,7 +1,9 @@
 package org.secuso.privacyfriendlyweather.activities;
 
+import android.app.AlertDialog;
 import android.content.Intent;
 import android.os.Bundle;
+import android.preference.PreferenceManager;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
@@ -19,6 +21,7 @@
 import org.secuso.privacyfriendlyweather.database.data.CurrentWeatherData;
 import org.secuso.privacyfriendlyweather.database.data.Forecast;
 import org.secuso.privacyfriendlyweather.database.data.WeekForecast;
+import org.secuso.privacyfriendlyweather.preferences.AppPreferencesManager;
 import org.secuso.privacyfriendlyweather.ui.updater.IUpdateableCityUI;
 import org.secuso.privacyfriendlyweather.ui.updater.ViewUpdater;
 import org.secuso.privacyfriendlyweather.ui.viewPager.WeatherPagerAdapter;
@@ -27,6 +30,7 @@
 
 public class ForecastCityActivity extends BaseActivity implements IUpdateableCityUI {
     private WeatherPagerAdapter pagerAdapter;
+    private AppPreferencesManager appPreferencesManager;
 
     private MenuItem refreshActionButton;
     private MenuItem rainviewerButton;
@@ -73,7 +77,6 @@ protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_forecast_city);
         overridePendingTransition(0, 0);
-
         //cityId = getIntent().getIntExtra("cityId", -1); //done in onResume
 
         initResources();
@@ -113,6 +116,18 @@ public void onPageScrollStateChanged(int state) {}
         }
     }
 
+    @Override
+    protected void onPostCreate(Bundle savedInstanceState) {
+        super.onPostCreate(savedInstanceState);
+
+        if (appPreferencesManager.getOWMApiKey(this) == null) {
+            new AlertDialog.Builder(this).setTitle("")
+                    .setMessage("Get your own API-Key yo")
+                    .setNeutralButton(android.R.string.ok, null)
+                    .show();
+        }
+    }
+
     public void updatePageTitle() {
         if (getSupportActionBar() != null && pagerAdapter.getCount() > 0) {
             getSupportActionBar().setTitle(pagerAdapter.getPageTitleForActionBar(viewPager.getCurrentItem()));
@@ -129,6 +144,7 @@ private void initResources() {
         viewPager = findViewById(R.id.viewPager);
         pagerAdapter = new WeatherPagerAdapter(this, getSupportFragmentManager());
         noCityText = findViewById(R.id.noCitySelectedText);
+        appPreferencesManager = new AppPreferencesManager(PreferenceManager.getDefaultSharedPreferences(this));
     }
 
     @Override
diff --git a/app/src/main/res/values-de/strings.xml b/app/src/main/res/values-de/strings.xml
index 444f69a9..d1b619a8 100644
--- a/app/src/main/res/values-de/strings.xml
+++ b/app/src/main/res/values-de/strings.xml
@@ -204,4 +204,6 @@
     <string name="help_permission_bindservice_description">Die Wetter-App ermöglicht Backups mit unserer Privacy Friendly Backup-App. Um diese Funktionalität zu aktivieren, wird die Berechtigung zum Verbinden mit Diensten benötigt.</string>
     <string name="owm_about">Wetterdaten zur Verfügung gestellt von:</string>
     <string name="owm_logo_copyright">"Das OpenWeatherMap Logo ist lizensiert unter\n<a href="https://creativecommons.org/licenses/by-sa/3.0/deed.en">Creative Commons BY-SA.</a>"</string>
+    <string name="dialog_app_api_deprecation_title">App Deprecation and API changes</string>
+    <string name="dialog_app_api_deprecation_description">Am 1. Juni 2024 deaktiviert Open Weather seine alte API, daher sind die alten API-Schlüssel nicht mehr verwendbar.</string>
 </resources>
diff --git a/app/src/main/res/values-it/strings.xml b/app/src/main/res/values-it/strings.xml
index c39053f0..9704b963 100644
--- a/app/src/main/res/values-it/strings.xml
+++ b/app/src/main/res/values-it/strings.xml
@@ -203,4 +203,6 @@
     <string name="help_permission_bindservice_description">L\'app meteo abilita i backup con la nostra app Privacy Friendly Backup. Per abilitare questa funzionalità, è necessario il permesso di legarsi ai servizi.</string>
     <string name="owm_about">Dati meteo forniti da:</string>
     <string name="owm_logo_copyright">"Il logo di OpenWeatherMap è concesso in licenza sotto\n<a href="https://creativecommons.org/licenses/by-sa/3.0/deed.en">la licenza Creative Commons BY-SA.</a>"</string>
+    <string name="dialog_app_api_deprecation_title">Deprecazione dell\'app e modifiche all\'API</string>
+    <string name="dialog_app_api_deprecation_description">Dal 1° giugno 2024 Open Weather disattiva la sua vecchia API, pertanto le vecchie chiavi API non sono più utilizzabili.</string>
 </resources>
diff --git a/app/src/main/res/values-ja/strings.xml b/app/src/main/res/values-ja/strings.xml
index 418984f5..d388c7e4 100644
--- a/app/src/main/res/values-ja/strings.xml
+++ b/app/src/main/res/values-ja/strings.xml
@@ -257,5 +257,7 @@
     <string name="help_permission_bindservice_description">The weather app enables backups with our Privacy Friendly Backup app. To enable this functionality, the permission to bind with services is needed.</string>
     <string name="owm_about">Weather data provided by:</string>
     <string name="owm_logo_copyright">"OpenWeatherMap logo is licensed under\n<a href="https://creativecommons.org/licenses/by-sa/3.0/deed.en">Creative Commons BY-SA license.</a>"</string>
+    <string name="dialog_app_api_deprecation_title">アプリの非推奨と API の変更</string>
+    <string name="dialog_app_api_deprecation_description">2024 年 6 月 1 日に、Open Weather は古い API を非アクティブ化するため、古い API キーは使用できなくなります。</string>
 
 </resources>
diff --git a/app/src/main/res/values-pt/strings.xml b/app/src/main/res/values-pt/strings.xml
index 35ea47b3..0ab88d80 100644
--- a/app/src/main/res/values-pt/strings.xml
+++ b/app/src/main/res/values-pt/strings.xml
@@ -203,4 +203,6 @@
     <string name="help_permission_bindservice_description">A aplicação meteorológica permite cópias de segurança com a nossa aplicação Privacy Friendly Backup. Para activar esta funcionalidade, é necessária a permissão de ligação com serviços.</string>
     <string name="owm_about">Dados meteorológicos fornecidos por:</string>
     <string name="owm_logo_copyright">"O logótipo OpenWeatherMap está licenciado sob\n<a href="https://creativecommons.org/licenses/by-sa/3.0/deed.en">Creative Commons BY-SA licença.</a>"</string>
+    <string name="dialog_app_api_deprecation_title">Descontinuação de aplicativos e alterações de API</string>
+    <string name="dialog_app_api_deprecation_description">Em 1º de junho de 2024, o Open Weather desativa sua API antiga, portanto, as chaves da API antigas não podem mais ser usadas.</string>
 </resources>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index ad904020..b5465542 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -174,6 +174,14 @@
     </string>
     <string name="dialog_add_close_button">Close</string>
     <string name="dialog_add_add_button">Add</string>
+    <string name="dialog_app_api_deprecation_title">App Deprecation and API changes</string>
+    <string name="dialog_app_api_deprecation_description">
+        On 1st June, 2024 Open Weather deactivates its old API, therefore the old api keys are not usable anymore.
+        As the Privacy Friendly Weather App is deprecated, we won\'t adjust to any api changes and the app won\'t function as expected.
+
+        If you want to continue using this app, get your own api key by following the <a href="https://openweathermap.org/appid">OpenWeather instruction</a>.
+        After obtaining your api key, set it in the settings.
+    </string>
 
     <!-- ###WEATHER CATEGORIES### -->
     <string name="weather_category_clear_sky">Clear Sky</string>